Sample records for accurate mechanical properties

  1. A Multiscale Red Blood Cell Model with Accurate Mechanics, Rheology, and Dynamics

    PubMed Central

    Fedosov, Dmitry A.; Caswell, Bruce; Karniadakis, George Em

    2010-01-01

    Abstract Red blood cells (RBCs) have highly deformable viscoelastic membranes exhibiting complex rheological response and rich hydrodynamic behavior governed by special elastic and bending properties and by the external/internal fluid and membrane viscosities. We present a multiscale RBC model that is able to predict RBC mechanics, rheology, and dynamics in agreement with experiments. Based on an analytic theory, the modeled membrane properties can be uniquely related to the experimentally established RBC macroscopic properties without any adjustment of parameters. The RBC linear and nonlinear elastic deformations match those obtained in optical-tweezers experiments. The rheological properties of the membrane are compared with those obtained in optical magnetic twisting cytometry, membrane thermal fluctuations, and creep followed by cell recovery. The dynamics of RBCs in shear and Poiseuille flows is tested against experiments and theoretical predictions, and the applicability of the latter is discussed. Our findings clearly indicate that a purely elastic model for the membrane cannot accurately represent the RBC's rheological properties and its dynamics, and therefore accurate modeling of a viscoelastic membrane is necessary. PMID:20483330

  2. A multiscale red blood cell model with accurate mechanics, rheology, and dynamics.

    PubMed

    Fedosov, Dmitry A; Caswell, Bruce; Karniadakis, George Em

    2010-05-19

    Red blood cells (RBCs) have highly deformable viscoelastic membranes exhibiting complex rheological response and rich hydrodynamic behavior governed by special elastic and bending properties and by the external/internal fluid and membrane viscosities. We present a multiscale RBC model that is able to predict RBC mechanics, rheology, and dynamics in agreement with experiments. Based on an analytic theory, the modeled membrane properties can be uniquely related to the experimentally established RBC macroscopic properties without any adjustment of parameters. The RBC linear and nonlinear elastic deformations match those obtained in optical-tweezers experiments. The rheological properties of the membrane are compared with those obtained in optical magnetic twisting cytometry, membrane thermal fluctuations, and creep followed by cell recovery. The dynamics of RBCs in shear and Poiseuille flows is tested against experiments and theoretical predictions, and the applicability of the latter is discussed. Our findings clearly indicate that a purely elastic model for the membrane cannot accurately represent the RBC's rheological properties and its dynamics, and therefore accurate modeling of a viscoelastic membrane is necessary. Copyright 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  3. Mechanical properties of human atherosclerotic intima tissue.

    PubMed

    Akyildiz, Ali C; Speelman, Lambert; Gijsen, Frank J H

    2014-03-03

    Progression and rupture of atherosclerotic plaques in coronary and carotid arteries are the key processes underlying myocardial infarctions and strokes. Biomechanical stress analyses to compute mechanical stresses in a plaque can potentially be used to assess plaque vulnerability. The stress analyses strongly rely on accurate representation of the mechanical properties of the plaque components. In this review, the composition of intima tissue and how this changes during plaque development is discussed from a mechanical perspective. The plaque classification scheme of the American Heart Association is reviewed and plaques originating from different vascular territories are compared. Thereafter, an overview of the experimental studies on tensile and compressive plaque intima properties are presented and the results are linked to the pathology of atherosclerotic plaques. This overview revealed a considerable variation within studies, and an enormous dispersion between studies. Finally, the implications of the dispersion in experimental data on the clinical applications of biomechanical plaque modeling are presented. Suggestions are made on mechanical testing protocol for plaque tissue and on using a standardized plaque classification scheme. This review identifies the current status of knowledge on plaque mechanical properties and the future steps required for a better understanding of the plaque type specific material properties. With this understanding, biomechanical plaque modeling may eventually provide essential support for clinical plaque risk stratification. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Methods for Efficiently and Accurately Computing Quantum Mechanical Free Energies for Enzyme Catalysis.

    PubMed

    Kearns, F L; Hudson, P S; Boresch, S; Woodcock, H L

    2016-01-01

    Enzyme activity is inherently linked to free energies of transition states, ligand binding, protonation/deprotonation, etc.; these free energies, and thus enzyme function, can be affected by residue mutations, allosterically induced conformational changes, and much more. Therefore, being able to predict free energies associated with enzymatic processes is critical to understanding and predicting their function. Free energy simulation (FES) has historically been a computational challenge as it requires both the accurate description of inter- and intramolecular interactions and adequate sampling of all relevant conformational degrees of freedom. The hybrid quantum mechanical molecular mechanical (QM/MM) framework is the current tool of choice when accurate computations of macromolecular systems are essential. Unfortunately, robust and efficient approaches that employ the high levels of computational theory needed to accurately describe many reactive processes (ie, ab initio, DFT), while also including explicit solvation effects and accounting for extensive conformational sampling are essentially nonexistent. In this chapter, we will give a brief overview of two recently developed methods that mitigate several major challenges associated with QM/MM FES: the QM non-Boltzmann Bennett's acceptance ratio method and the QM nonequilibrium work method. We will also describe usage of these methods to calculate free energies associated with (1) relative properties and (2) along reaction paths, using simple test cases with relevance to enzymes examples. © 2016 Elsevier Inc. All rights reserved.

  5. Engineering the Mechanical Properties of Polymer Networks with Precise Doping of Primary Defects.

    PubMed

    Chan, Doreen; Ding, Yichuan; Dauskardt, Reinhold H; Appel, Eric A

    2017-12-06

    Polymer networks are extensively utilized across numerous applications ranging from commodity superabsorbent polymers and coatings to high-performance microelectronics and biomaterials. For many applications, desirable properties are known; however, achieving them has been challenging. Additionally, the accurate prediction of elastic modulus has been a long-standing difficulty owing to the presence of loops. By tuning the prepolymer formulation through precise doping of monomers, specific primary network defects can be programmed into an elastomeric scaffold, without alteration of their resulting chemistry. The addition of these monomers that respond mechanically as primary defects is used both to understand their impact on the resulting mechanical properties of the materials and as a method to engineer the mechanical properties. Indeed, these materials exhibit identical bulk and surface chemistry, yet vastly different mechanical properties. Further, we have adapted the real elastic network theory (RENT) to the case of primary defects in the absence of loops, thus providing new insights into the mechanism for material strength and failure in polymer networks arising from primary network defects, and to accurately predict the elastic modulus of the polymer system. The versatility of the approach we describe and the fundamental knowledge gained from this study can lead to new advancements in the development of novel materials with precisely defined and predictable chemical, physical, and mechanical properties.

  6. Effect of vitro preservation on mechanical properties of brain tissue

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Liu, Yi-fan; Liu, Li-fu; Niu, Ying; Ma, Jian-li; Wu, Cheng-wei

    2017-05-01

    To develop the protective devices for preventing traumatic brain injuries, it requires the accurate characterization of the mechanical properties of brain tissue. For this, it necessary to elucidate the effect of vitro preservation on the mechanical performance of brain tissue as usually the measurements are carried out in vitro. In this paper, the thermal behavior of brain tissue preserved for various period of time was first investigated and the mechanical properties were also measured. Both reveals the deterioration with prolonged preservation duration. The observations of brain tissue slices indicates the brain tissue experiences karyorrhexis and karyorrhexis in sequence, which accounts for the deterioration phenomena.

  7. Kinetic approach to degradation mechanisms in polymer solar cells and their accurate lifetime predictions

    NASA Astrophysics Data System (ADS)

    Arshad, Muhammad Azeem; Maaroufi, AbdelKrim

    2018-07-01

    A beginning has been made in the present study regarding the accurate lifetime predictions of polymer solar cells. Certain reservations about the conventionally employed temperature accelerated lifetime measurements test for its unworthiness of predicting reliable lifetimes of polymer solar cells are brought into light. Critical issues concerning the accelerated lifetime testing include, assuming reaction mechanism instead of determining it, and relying solely on the temperature acceleration of a single property of material. An advanced approach comprising a set of theoretical models to estimate the accurate lifetimes of polymer solar cells is therefore suggested in order to suitably alternate the accelerated lifetime testing. This approach takes into account systematic kinetic modeling of various possible polymer degradation mechanisms under natural weathering conditions. The proposed kinetic approach is substantiated by its applications on experimental aging data-sets of polymer solar materials/solar cells including, P3HT polymer film, bulk heterojunction (MDMO-PPV:PCBM) and dye-sensitized solar cells. Based on the suggested approach, an efficacious lifetime determination formula for polymer solar cells is derived and tested on dye-sensitized solar cells. Some important merits of the proposed method are also pointed out and its prospective applications are discussed.

  8. Constitutive model of friction stir weld with consideration of its inhomogeneous mechanical properties

    NASA Astrophysics Data System (ADS)

    Zhang, Ling; Min, Junying; Wang, Bin; Lin, Jianping; Li, Fangfang; Liu, Jing

    2016-03-01

    In practical engineering, finite element(FE) modeling for weld seam is commonly simplified by neglecting its inhomogeneous mechanical properties. This will cause a significant loss in accuracy of FE forming analysis, in particular, for friction stir welded(FSW) blanks due to the large width and good formability of its weld seam. The inhomogeneous mechanical properties across weld seam need to be well characterized for an accurate FE analysis. Based on a similar AA5182 FSW blank, the metallographic observation and micro-Vickers hardness analysis upon the weld cross-section are performed to identify the interfaces of different sub-zones, i.e., heat affected zone(HAZ), thermal-mechanically affected zone(TMAZ) and weld nugget(WN). Based on the rule of mixture and hardness distribution, a constitutive model is established for each sub-zone to characterize the inhomogeneous mechanical properties across the weld seam. Uniaxial tensile tests of the AA5182 FSW blank are performed with the aid of digital image correlation(DIC) techniques. Experimental local stress-strain curves are obtained for different weld sub-zones. The experimental results show good agreement with those derived from the constitutive models, which demonstrates the feasibility and accuracy of these models. The proposed research gives an accurate characterization of inhomogeneous mechanical properties across the weld seam produced by FSW, which provides solutions for improving the FE simulation accuracy of FSW sheet forming.

  9. Methodologies in determining mechanical properties of thin films using nanoindentation

    NASA Astrophysics Data System (ADS)

    Han, Seung Min Jane

    Thin films are critical components of microelectronic and MEMS devices, and evaluating their mechanical properties is of current interest. As the dimensions of the devices become smaller and smaller, however, understanding the mechanical properties of materials at sub-micron length scales becomes more challenging. The conventional methods for evaluating strengths of materials in bulk form cannot be applied, and new methodologies are required for accurately evaluating mechanical properties of thin films. In this work, development of methodologies using the nanoindenter was pursued in three parts: (1) creation of a new method for extracting thin film hardness, (2) use of combinatorial methods for determining compositions with desired mechanical properties, and (3) use of microcompression testing of sub-micron sized pillars to understand plasticity in Al-Sc multilayers. The existing nanoindentation hardness model by Oliver & Pharr is unable to accurately determine the hardness of thin films on substrates with an elastic mismatch. Thus, a new method of analysis for extracting thin film hardness from film/substrate systems, that eliminates the effect of elastic mismatch of the underlying substrate, surface roughness, and also pile-up/sink-in, is needed. Such a method was developed in the first part of this study. The feasibility of using the nanoindentation hardness together with combinatorial methods to efficiently scan through mechanical properties of Ti-Al metallic alloys was examined in the second part of this study. The combinatorial approach provides an efficient method that can be used to determine alloy compositions that might merit further exploration and development as bulk materials. Finally, the mechanical properties of Al-Al3Sc multilayers with bilayer periods ranging from 6-100 nm were examined using microcompression. The sub-micron sized pillars were prepared using the focused ion beam (FIB) and compression tested with the flat tip of the nanoindenter

  10. Determination of mechanical properties of battery films from acoustic resonances

    NASA Astrophysics Data System (ADS)

    Dallon, Kathryn L.; Yao, Jing; Wheeler, Dean R.; Mazzeo, Brian A.

    2018-04-01

    Measuring the mechanical properties of lithium-ion battery films, such as thickness and elasticity, is important for predicting and improving homogeneity of the films and subsequent performance of the battery. Problems with film heterogeneity could be identified and addressed early on through accurate, non-destructive inspection of the electrode as it is being manufactured. This research investigates the use of acoustic measurements as an alternative means of non-destructive quality control that could be adapted for on-line use. Here we report on our efforts to distinguish among films with different mechanical properties using acoustic resonances. A clamped film is excited using a pulsed infrared laser to produce an acoustic resonance in a confined area, and a microphone measures the acoustic response. Because the resonance depends on properties such as thickness and density, the resonance frequency shifts with changes in these properties. As the thickness increases, the resonance frequency decreases. These results show that acoustic tests can demonstrate observable differences between films with different properties.

  11. Mechanical Properties of Fe-Ni Meteorites

    NASA Astrophysics Data System (ADS)

    Roberta, Mulford; El Dasher, B.

    2010-10-01

    Iron-nickel meteorites exhibit a unique lamellar microstructure, Widmanstatten patterns, consisting of small regions with steep-iron-nickel composition gradients.1,2 The microstructure arises as a result of extremely slow cooling in a planetary core or other large mass. Mechanical properties of these structures have been investigated using microindentation, x-ray fluorescence, and EBSD. Observation of local mechanical properties in these highly structured materials supplements bulk measurements, which can exhibit large variation in dynamic properties, even within a single sample. 3 Accurate mechanical properties for meteorites may enable better modeling of planetary cores, the likely origin of these objects. Appropriate values for strength are important in impact and crater modeling and in understanding the consequences of observed impacts on planetary crusts. Previous studies of the mechanical properties of a typical iron-nickel meteorite, a Diablo Canyon specimen, indicated that the strength of the composite was higher by almost an order of magnitude than values obtained from laboratory-prepared specimens.4 This was ascribed to the extreme work-hardening evident in the EBSD measurements. This particular specimen exhibited only residual Widmanstatten structures, and may have been heated and deformed during its traverse of the atmosphere. Additional specimens from the Canyon Diablo fall (type IAB, coarse octahedrite) and examples from the Muonionalusta meteorite and Gibeon fall ( both IVA, fine octahedrite), have been examined to establish a range of error on the previously measured yield, to determine the extent to which deformation upon re-entry contributes to yield, and to establish the degree to which the strength varies as a function of microstructure. 1. A. Christiansen, et.al., Physica Scripta, 29 94-96 (1984.) 2. Goldstein and Ogilvie, Geochim Cosmochim Acta, 29 893-925 (1965.) 3. M. D. Furnish, M.B. Boslough, G.T. Gray II, and J.L. Remo, Int. J. Impact Eng

  12. Mechanism for accurate, protein-assisted DNA annealing by Deinococcus radiodurans DdrB

    PubMed Central

    Sugiman-Marangos, Seiji N.; Weiss, Yoni M.; Junop, Murray S.

    2016-01-01

    Accurate pairing of DNA strands is essential for repair of DNA double-strand breaks (DSBs). How cells achieve accurate annealing when large regions of single-strand DNA are unpaired has remained unclear despite many efforts focused on understanding proteins, which mediate this process. Here we report the crystal structure of a single-strand annealing protein [DdrB (DNA damage response B)] in complex with a partially annealed DNA intermediate to 2.2 Å. This structure and supporting biochemical data reveal a mechanism for accurate annealing involving DdrB-mediated proofreading of strand complementarity. DdrB promotes high-fidelity annealing by constraining specific bases from unauthorized association and only releases annealed duplex when bound strands are fully complementary. To our knowledge, this mechanism provides the first understanding for how cells achieve accurate, protein-assisted strand annealing under biological conditions that would otherwise favor misannealing. PMID:27044084

  13. Investigation of Mechanical Properties and Interfacial Mechanics of Crystalline Nanomaterials

    NASA Astrophysics Data System (ADS)

    Qin, Qingquan

    Nanowires (NWs) and nanotubes (NTs) are critical building blocks of nanotechnologies. The operation and reliability of these nanomaterials based devices depend on their mechanical properties of the nanomaterials, which is therefore important to accurately measure the mechanical properties. Besides, the NW--substrate interfaces also play a critical role in both mechanical reliability and electrical performance of these nanodevices, especially when the size of the NW is small. In this thesis, we focus on the mechanical properties and interface mechanics of three important one dimensional (1D) nanomaterials: ZnO NWs, Ag NWs and Si NWs. For the size effect study, this thesis presents a systematic experimental investigation on the elastic and failure properties of ZnO NWs under different loading modes: tension and buckling. Both tensile modulus (from tension) and bending modulus (from buckling) were found to increase as the NW diameter decreased from 80 to 20 nm. The elastic modulus also shows loading mode dependent; the bending modulus increases more rapidly than the tensile modulus. The tension experiments showed that fracture strain and strength of ZnO NWs increase as the NW diameter decrease. A resonance testing setup was developed to measure elastic modulus of ZnO NWs to confirm the loading mode dependent effect. A systematic study was conducted on the effect of clamping on resonance frequency and thus measured Young's modulus of NWs via a combined experiment and simulation approach. A simple scaling law was provided as guidelines for future designs to accurate measure elastic modulus of a cantilevered NW using the resonance method. This thesis reports the first quantitative measurement of a full spectrum of mechanical properties of five-fold twinned Ag NWs including Young's modulus, yield strength and ultimate tensile strength. In situ tensile testing of Ag NWs with diameters between 34 and 130 nm was carried out inside a SEM. Young's modulus, yield strength and

  14. Experimental study and constitutive modeling of the viscoelastic mechanical properties of the human prolapsed vaginal tissue.

    PubMed

    Peña, Estefania; Calvo, B; Martínez, M A; Martins, P; Mascarenhas, T; Jorge, R M N; Ferreira, A; Doblaré, M

    2010-02-01

    In this paper, the viscoelastic mechanical properties of vaginal tissue are investigated. Using previous results of the authors on the mechanical properties of biological soft tissues and newly experimental data from uniaxial tension tests, a new model for the viscoelastic mechanical properties of the human vaginal tissue is proposed. The structural model seems to be sufficiently accurate to guarantee its application to prediction of reliable stress distributions, and is suitable for finite element computations. The obtained results may be helpful in the design of surgical procedures with autologous tissue or prostheses.

  15. Accurate RNA 5-methylcytosine site prediction based on heuristic physical-chemical properties reduction and classifier ensemble.

    PubMed

    Zhang, Ming; Xu, Yan; Li, Lei; Liu, Zi; Yang, Xibei; Yu, Dong-Jun

    2018-06-01

    RNA 5-methylcytosine (m 5 C) is an important post-transcriptional modification that plays an indispensable role in biological processes. The accurate identification of m 5 C sites from primary RNA sequences is especially useful for deeply understanding the mechanisms and functions of m 5 C. Due to the difficulty and expensive costs of identifying m 5 C sites with wet-lab techniques, developing fast and accurate machine-learning-based prediction methods is urgently needed. In this study, we proposed a new m 5 C site predictor, called M5C-HPCR, by introducing a novel heuristic nucleotide physicochemical property reduction (HPCR) algorithm and classifier ensemble. HPCR extracts multiple reducts of physical-chemical properties for encoding discriminative features, while the classifier ensemble is applied to integrate multiple base predictors, each of which is trained based on a separate reduct of the physical-chemical properties obtained from HPCR. Rigorous jackknife tests on two benchmark datasets demonstrate that M5C-HPCR outperforms state-of-the-art m 5 C site predictors, with the highest values of MCC (0.859) and AUC (0.962). We also implemented the webserver of M5C-HPCR, which is freely available at http://cslab.just.edu.cn:8080/M5C-HPCR/. Copyright © 2018 Elsevier Inc. All rights reserved.

  16. Atomistic modeling of BN nanofillers for mechanical and thermal properties: a review.

    PubMed

    Kumar, Rajesh; Parashar, Avinash

    2016-01-07

    Due to their exceptional mechanical properties, thermal conductivity and a wide band gap (5-6 eV), boron nitride nanotubes and nanosheets have promising applications in the field of engineering and biomedical science. Accurate modeling of failure or fracture in a nanomaterial inherently involves coupling of atomic domains of cracks and voids as well as a deformation mechanism originating from grain boundaries. This review highlights the recent progress made in the atomistic modeling of boron nitride nanofillers. Continuous improvements in computational power have made it possible to study the structural properties of these nanofillers at the atomistic scale.

  17. Mechanical Properties of Graphene Nanoplatelet/Carbon Fiber/Epoxy Hybrid Composites: Multiscale Modeling and Experiments

    NASA Technical Reports Server (NTRS)

    Hadden, C. M.; Klimek-McDonald, D. R.; Pineda, E. J.; King, J. A.; Reichanadter, A. M.; Miskioglu, I.; Gowtham, S.; Odegard, G. M.

    2015-01-01

    Because of the relatively high specific mechanical properties of carbon fiber/epoxy composite materials, they are often used as structural components in aerospace applications. Graphene nanoplatelets (GNPs) can be added to the epoxy matrix to improve the overall mechanical properties of the composite. The resulting GNP/carbon fiber/epoxy hybrid composites have been studied using multiscale modeling to determine the influence of GNP volume fraction, epoxy crosslink density, and GNP dispersion on the mechanical performance. The hierarchical multiscale modeling approach developed herein includes Molecular Dynamics (MD) and micromechanical modeling, and it is validated with experimental testing of the same hybrid composite material system. The results indicate that the multiscale modeling approach is accurate and provides physical insight into the composite mechanical behavior. Also, the results quantify the substantial impact of GNP volume fraction and dispersion on the transverse mechanical properties of the hybrid composite while the effect on the axial properties is shown to be insignificant.

  18. Mechanical Properties of Graphene Nanoplatelet/Carbon Fiber/Epoxy Hybrid Composites: Multiscale Modeling and Experiments

    NASA Technical Reports Server (NTRS)

    Hadden, C. M.; Klimek-McDonald, D. R.; Pineda, E. J.; King, J. A.; Reichanadter, A. M.; Miskioglu, I.; Gowtham, S.; Odegard, G. M.

    2015-01-01

    Because of the relatively high specific mechanical properties of carbon fiber/epoxy composite materials, they are often used as structural components in aerospace applications. Graphene nanoplatelets (GNPs) can be added to the epoxy matrix to improve the overall mechanical properties of the composite. The resulting GNP/carbon fiber/epoxy hybrid composites have been studied using multiscale modeling to determine the influence of GNP volume fraction, epoxy crosslink density, and GNP dispersion on the mechanical performance. The hierarchical multiscale modeling approach developed herein includes Molecular Dynamics (MD) and micromechanical modeling, and it is validated with experimental testing of the same hybrid composite material system. The results indicate that the multiscale modeling approach is accurate and provides physical insight into the composite mechanical behavior. Also, the results quantify the substantial impact of GNP volume fraction and dispersion on the transverse mechanical properties of the hybrid composite, while the effect on the axial properties is shown to be insignificant.

  19. Mechanical Properties of Graphene Nanoplatelet Carbon Fiber Epoxy Hybrid Composites: Multiscale Modeling and Experiments

    NASA Technical Reports Server (NTRS)

    Hadden, Cameron M.; Klimek-McDonald, Danielle R.; Pineda, Evan J.; King, Julie A.; Reichanadter, Alex M.; Miskioglu, Ibrahim; Gowtham, S.; Odegard, Gregory M.

    2015-01-01

    Because of the relatively high specific mechanical properties of carbon fiber/epoxy composite materials, they are often used as structural components in aerospace applications. Graphene nanoplatelets (GNPs) can be added to the epoxy matrix to improve the overall mechanical properties of the composite. The resulting GNP/carbon fiber/epoxy hybrid composites have been studied using multiscale modeling to determine the influence of GNP volume fraction, epoxy crosslink density, and GNP dispersion on the mechanical performance. The hierarchical multiscale modeling approach developed herein includes Molecular Dynamics (MD) and micromechanical modeling, and it is validated with experimental testing of the same hybrid composite material system. The results indicate that the multiscale modeling approach is accurate and provides physical insight into the composite mechanical behavior. Also, the results quantify the substantial impact of GNP volume fraction and dispersion on the transverse mechanical properties of the hybrid composite, while the effect on the axial properties is shown to be insignificant.

  20. Mechanical properties of transription

    NASA Astrophysics Data System (ADS)

    Sevier, Stuart; Levine, Herbert

    Over the last several decades it has been increasingly recognized that both stochastic and mechanical processes play a central role in transcription. Though many aspects have been explained a number of fundamental properties are undeveloped. Recent results have pointed to mechanical feedback as the source of transcriptional bursting and DNA supercoiling but a reconciliation of this perspective with preexisting views of transcriptional is lacking. In this work we present a simple model of transcription where RNA elongation, RNA polymerase rotation and DNA supercoiling are coupled. The mechanical properties of each object form a foundational framework for understanding the physical nature of transcription. The resulting model can explain several important aspects of chromatin structure and generates a number of predictions for the mechanical properties of transcription.

  1. Mechanical properties of low dimensional materials

    NASA Astrophysics Data System (ADS)

    Saini, Deepika

    Recent advances in low dimensional materials (LDMs) have paved the way for unprecedented technological advancements. The drive to reduce the dimensions of electronics has compelled researchers to devise newer techniques to not only synthesize novel materials, but also tailor their properties. Although micro and nanomaterials have shown phenomenal electronic properties, their mechanical robustness and a thorough understanding of their structure-property relationship are critical for their use in practical applications. However, the challenges in probing these mechanical properties dramatically increase as their dimensions shrink, rendering the commonly used techniques inadequate. This dissertation focuses on developing techniques for accurate determination of elastic modulus of LDMs and their mechanical responses under tensile and shear stresses. Fibers with micron-sized diameters continuously undergo tensile and shear deformations through many phases of their processing and applications. Significant attention has been given to their tensile response and their structure-tensile properties relations are well understood, but the same cannot be said about their shear responses or the structure-shear properties. This is partly due to the lack of appropriate instruments that are capable of performing direct shear measurements. In an attempt to fill this void, this dissertation describes the design of an inexpensive tabletop instrument, referred to as the twister, which can measure the shear modulus (G) and other longitudinal shear properties of micron-sized individual fibers. An automated system applies a pre-determined twist to the fiber sample and measures the resulting torque using a sensitive optical detector. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers. Two industrially important fibers, IM7 carbon fiber and KevlarRTM 119, were found to have G = 17 and 2.4 GPa, respectively. In addition to measuring the shear

  2. The Mechanical Properties of Nanowires

    PubMed Central

    Wang, Shiliang; Shan, Zhiwei

    2017-01-01

    Applications of nanowires into future generation nanodevices require a complete understanding of the mechanical properties of the nanowires. A great research effort has been made in the past two decades to understand the deformation physics and mechanical behaviors of nanowires, and to interpret the discrepancies between experimental measurements and theoretical predictions. This review focused on the characterization and understanding of the mechanical properties of nanowires, including elasticity, plasticity, anelasticity and strength. As the results from the previous literature in this area appear inconsistent, a critical evaluation of the characterization techniques and methodologies were presented. In particular, the size effects of nanowires on the mechanical properties and their deformation mechanisms were discussed. PMID:28435775

  3. Grindability and mechanical property of ceramics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Guo, Changsheng; Chand, R.H.

    1996-12-31

    For cost-effective ceramic machining, material-specific machining methodology is needed. This requires characterizing ceramics from machining view point. In this paper, a preliminary study of the correlation between grindability and mechanical properties is reported. Results indicate that there exists complex correlations between grindability and mechanical properties such as hardness, fracture toughness and elasticity. Some ceramics of similar mechanical properties have different grindabilities, which implies that it is possible to develop ceramics of both superior mechanical properties and good grindability.

  4. Characterizing viscoelastic mechanical properties of highly compliant polymers and biological tissues using impact indentation.

    PubMed

    Mijailovic, Aleksandar S; Qing, Bo; Fortunato, Daniel; Van Vliet, Krystyn J

    2018-04-15

    Precise and accurate measurement of viscoelastic mechanical properties becomes increasingly challenging as sample stiffness decreases to elastic moduli <1 kPa, largely due to difficulties detecting initial contact with the compliant sample surface. This limitation is particularly relevant to characterization of biological soft tissues and compliant gels. Here, we employ impact indentation which, in contrast to shear rheology and conventional indentation, does not require contact detection a priori, and present a novel method to extract viscoelastic moduli and relaxation time constants directly from the impact response. We first validate our approach by using both impact indentation and shear rheology to characterize polydimethylsiloxane (PDMS) elastomers of stiffness ranging from 100 s of Pa to nearly 10 kPa. Assuming a linear viscoelastic constitutive model for the material, we find that the moduli and relaxation times obtained from fitting the impact response agree well with those obtained from fitting the rheological response. Next, we demonstrate our validated method on hydrated, biological soft tissues obtained from porcine brain, murine liver, and murine heart, and report the equilibrium shear moduli, instantaneous shear moduli, and relaxation time constants for each tissue. Together, our findings provide a new and straightforward approach capable of probing local mechanical properties of highly compliant viscoelastic materials with millimeter scale spatial resolution, mitigating complications involving contact detection or sample geometric constraints. Characterization and optimization of mechanical properties can be essential for the proper function of biomaterials in diverse applications. However, precise and accurate measurement of viscoelastic mechanical properties becomes increasingly difficult with increased compliance (particularly for elastic moduli <1 kPa), largely due to challenges detecting initial contact with the compliant sample surface

  5. Physical and mechanical properties of the B2 compound NiAl

    NASA Technical Reports Server (NTRS)

    Noebe, R. D.; Bowman, R. R.; Nathal, M. V.

    1993-01-01

    Considerable work has been performed on NiAl over the last three decades, with an extremely rapid growth in research on this intermetallic occurring in the last few years due to recent interest in this material for electronic and high temperature structural applications. However, many physical properties and the controlling fracture and deformation mechanisms over certain temperature regimes are still in question. Part of this problem lies in the incomplete characterization of many of the alloys previously investigated. Fragmentary data on processing conditions, chemistry, microstructure and the apparent difficulty in accurately measuring composition has made direct comparison between individual studies sometimes tenuous. Therefore, the purpose of this review is to summarize all available mechanical and pertinent physical properties on NiAl, stressing the most recent investigations, in an attempt to understand the behavior of NiAl and its alloys over a broad temperature range.

  6. Size Dependent Mechanical Properties of Monolayer Densely Arranged Polystyrene Nanospheres.

    PubMed

    Huang, Peng; Zhang, Lijing; Yan, Qingfeng; Guo, Dan; Xie, Guoxin

    2016-12-13

    In contrast to macroscopic materials, the mechanical properties of polymer nanospheres show fascinating scientific and application values. However, the experimental measurements of individual nanospheres and quantitative analysis of theoretical mechanisms remain less well performed and understood. We provide a highly efficient and accurate method with monolayer densely arranged honeycomb polystyrene (PS) nanospheres for the quantitatively mechanical characterization of individual nanospheres on the basis of atomic force microscopy (AFM) nanoindentation. The efficiency is improved by 1-2 orders, and the accuracy is also enhanced almost by half-order. The elastic modulus measured in the experiments increases with decreasing radius to the smallest nanospheres (25-35 nm in radius). A core-shell model is introduced to predict the size dependent elasticity of PS nanospheres, and the theoretical prediction agrees reasonably well with the experimental results and also shows a peak modulus value.

  7. Accurate quantification of magnetic particle properties by intra-pair magnetophoresis for nanobiotechnology

    NASA Astrophysics Data System (ADS)

    van Reenen, Alexander; Gao, Yang; Bos, Arjen H.; de Jong, Arthur M.; Hulsen, Martien A.; den Toonder, Jaap M. J.; Prins, Menno W. J.

    2013-07-01

    The application of magnetic particles in biomedical research and in-vitro diagnostics requires accurate characterization of their magnetic properties, with single-particle resolution and good statistics. Here, we report intra-pair magnetophoresis as a method to accurately quantify the field-dependent magnetic moments of magnetic particles and to rapidly generate histograms of the magnetic moments with good statistics. We demonstrate our method with particles of different sizes and from different sources, with a measurement precision of a few percent. We expect that intra-pair magnetophoresis will be a powerful tool for the characterization and improvement of particles for the upcoming field of particle-based nanobiotechnology.

  8. Accurate prediction of X-ray pulse properties from a free-electron laser using machine learning

    DOE PAGES

    Sanchez-Gonzalez, A.; Micaelli, P.; Olivier, C.; ...

    2017-06-05

    Free-electron lasers providing ultra-short high-brightness pulses of X-ray radiation have great potential for a wide impact on science, and are a critical element for unravelling the structural dynamics of matter. To fully harness this potential, we must accurately know the X-ray properties: intensity, spectrum and temporal profile. Owing to the inherent fluctuations in free-electron lasers, this mandates a full characterization of the properties for each and every pulse. While diagnostics of these properties exist, they are often invasive and many cannot operate at a high-repetition rate. Here, we present a technique for circumventing this limitation. Employing a machine learning strategy,more » we can accurately predict X-ray properties for every shot using only parameters that are easily recorded at high-repetition rate, by training a model on a small set of fully diagnosed pulses. Lastly, this opens the door to fully realizing the promise of next-generation high-repetition rate X-ray lasers.« less

  9. Accurate prediction of X-ray pulse properties from a free-electron laser using machine learning

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sanchez-Gonzalez, A.; Micaelli, P.; Olivier, C.

    Free-electron lasers providing ultra-short high-brightness pulses of X-ray radiation have great potential for a wide impact on science, and are a critical element for unravelling the structural dynamics of matter. To fully harness this potential, we must accurately know the X-ray properties: intensity, spectrum and temporal profile. Owing to the inherent fluctuations in free-electron lasers, this mandates a full characterization of the properties for each and every pulse. While diagnostics of these properties exist, they are often invasive and many cannot operate at a high-repetition rate. Here, we present a technique for circumventing this limitation. Employing a machine learning strategy,more » we can accurately predict X-ray properties for every shot using only parameters that are easily recorded at high-repetition rate, by training a model on a small set of fully diagnosed pulses. Lastly, this opens the door to fully realizing the promise of next-generation high-repetition rate X-ray lasers.« less

  10. Loading rate effect on mechanical properties of cervical spine ligaments.

    PubMed

    Trajkovski, Ana; Omerovic, Senad; Krasna, Simon; Prebil, Ivan

    2014-01-01

    Mechanical properties of cervical spine ligaments are of great importance for an accurate finite element model when analyzing the injury mechanism. However, there is still little experimental data in literature regarding fresh human cervical spine ligaments under physiological conditions. The focus of the present study is placed on three cervical spine ligaments that stabilize the spine and protect the spinal cord: the anterior longitudinal ligament, the posterior longitudinal ligament and the ligamentum flavum. The ligaments were tested within 24-48 hours after death, under two different loading rates. An increase trend in failure load, failure stress, stiffness and modulus was observed, but proved not to be significant for all ligament types. The loading rate had the highest impact on failure forces for all three ligaments (a 39.1% average increase was found). The observed increase trend, compared to the existing increase trends reported in literature, indicates the importance of carefully applying the existing experimental data, especially when creating scaling factors. A better understanding of the loading rate effect on ligaments properties would enable better case-specific human modelling.

  11. Mechanical Properties of Polymers.

    ERIC Educational Resources Information Center

    Aklonis, J. J.

    1981-01-01

    Mechanical properties (stress-strain relationships) of polymers are reviewed, taking into account both time and temperature factors. Topics include modulus-temperature behavior of polymers, time dependence, time-temperature correspondence, and mechanical models. (JN)

  12. Accurate transport properties for H–CO and H–CO{sub 2}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dagdigian, Paul J., E-mail: pjdagdigian@jhu.edu

    2015-08-07

    Transport properties for collisions of hydrogen atoms with CO and CO{sub 2} have been computed by means of quantum scattering calculations. The carbon oxides are important species in hydrocarbon combustion. The following potential energy surfaces (PES’s) for the interaction of the molecule fixed in its equilibrium geometry were employed: for H–CO, the PES was taken from the work of Song et al. [J. Phys. Chem. A 117, 7571 (2013)], while the PES for H–CO{sub 2} was computed in this study by a restricted coupled cluster method that included single, double, and (perturbatively) triple excitations. The computed transport properties were foundmore » to be significantly different from those computed by the conventional approach that employs isotropic Lennard-Jones (12-6) potentials. The effect of using the presently computed accurate transport properties in 1-dimensional combustion simulations of methane-air flames was investigated.« less

  13. Mechanical Properties of Be-Al Alloys

    DTIC Science & Technology

    2000-02-22

    technology (sand and mold casting) producing a coarse dendritic structure that did not produce mechanical properties appropriate for structural ... Mechanical Properties of Be-AI Alloys 2. REPORT TYPE Technical Report 6. AUTHOR(S) E. U. Lee K. George V. V. Agarwala H. Sanders 3. DATES...SUPPLEMENTARY NOTES 14. ABSTRACT ~ — — This study was conducted to define the mechanical properties of a wrought 62Be-38A1 alloy and a cast 65Be-32A1

  14. Hyperspectral imaging-based spatially-resolved technique for accurate measurement of the optical properties of horticultural products

    NASA Astrophysics Data System (ADS)

    Cen, Haiyan

    Hyperspectral imaging-based spatially-resolved technique is promising for determining the optical properties and quality attributes of horticultural and food products. However, considerable challenges still exist for accurate determination of spectral absorption and scattering properties from intact horticultural products. The objective of this research was, therefore, to develop and optimize hyperspectral imaging-based spatially-resolved technique for accurate measurement of the optical properties of horticultural products. Monte Carlo simulations and experiments for model samples of known optical properties were performed to optimize the inverse algorithm of a single-layer diffusion model and the optical designs, for extracting the absorption (micro a) and reduced scattering (micros') coefficients from spatially-resolved reflectance profiles. The logarithm and integral data transformation and the relative weighting methods were found to greatly improve the parameter estimation accuracy with the relative errors of 10.4%, 10.7%, and 11.4% for micro a, and 6.6%, 7.0%, and 7.1% for micros', respectively. More accurate measurements of optical properties were obtained when the light beam was of Gaussian type with the diameter of less than 1 mm, and the minimum and maximum source-detector distances were 1.5 mm and 10--20 transport mean free paths, respectively. An optical property measuring prototype was built, based on the optimization results, and evaluated for automatic measurement of absorption and reduced scattering coefficients for the wavelengths of 500--1,000 nm. The instrument was used to measure the optical properties, and assess quality/maturity, of 500 'Redstar' peaches and 1039 'Golden Delicious' (GD) and 1040 'Delicious' (RD) apples. A separate study was also conducted on confocal laser scanning and scanning electron microscopic image analysis and compression test of fruit tissue specimens to measure the structural and mechanical properties of 'Golden

  15. Nondestructive evaluation of hydrogel mechanical properties using ultrasound

    PubMed Central

    Walker, Jason M.; Myers, Ashley M.; Schluchter, Mark D.; Goldberg, Victor M.; Caplan, Arnold I.; Berilla, Jim A.; Mansour, Joseph M.; Welter, Jean F.

    2012-01-01

    The feasibility of using ultrasound technology as a noninvasive, nondestructive method for evaluating the mechanical properties of engineered weight-bearing tissues was evaluated. A fixture was designed to accurately and reproducibly position the ultrasound transducer normal to the test sample surface. Agarose hydrogels were used as phantoms for cartilage to explore the feasibility of establishing correlations between ultrasound measurements and commonly used mechanical tissue assessments. The hydrogels were fabricated in 1–10% concentrations with a 2–10 mm thickness. For each concentration and thickness, six samples were created, for a total of 216 gel samples. Speed of sound was determined from the time difference between peak reflections and the known height of each sample. Modulus was computed from the speed of sound using elastic and poroelastic models. All ultrasonic measurements were made using a 15 MHz ultrasound transducer. The elastic modulus was also determined for each sample from a mechanical unconfined compression test. Analytical comparison and statistical analysis of ultrasound and mechanical testing data was carried out. A correlation between estimates of compressive modulus from ultrasonic and mechanical measurements was found, but the correlation depended on the model used to estimate the modulus from ultrasonic measurements. A stronger correlation with mechanical measurements was found using the poroelastic rather than the elastic model. Results from this preliminary testing will be used to guide further studies of native and engineered cartilage. PMID:21773854

  16. Mechanical Properties of Polymer Nano-composites

    NASA Astrophysics Data System (ADS)

    Srivastava, Iti

    Thermoset polymer composites are increasingly important in high-performance engineering industries due to their light-weight and high specific strength, finding cutting-edge applications such as aircraft fuselage material and automobile parts. Epoxy is the most widely employed thermoset polymer, but is brittle due to extensive cross-linking and notch sensitivity, necessitating mechanical property studies especially fracture toughness and fatigue resistance, to ameliorate the low crack resistance. Towards this end, various nano and micro fillers have been used with epoxy to form composite materials. Particularly for nano-fillers, the 1-100 nm scale dimensions lead to fascinating mechanical properties, oftentimes proving superior to the epoxy matrix. The chemical nature, topology, mechanical properties and geometry of the nano-fillers have a profound influence on nano-composite behavior and hence are studied in the context of enhancing properties and understanding reinforcement mechanisms in polymer matrix nano-composites. Using carbon nanotubes (CNTs) as polymer filler, uniquely results in both increased stiffness as well as toughness, leading to extensive research on their applications. Though CNTs-polymer nano-composites offer better mechanical properties, at high stress amplitude their fatigue resistance is lost. In this work covalent functionalization of CNTs has been found to have a profound impact on mechanical properties of the CNT-epoxy nano-composite. Amine treated CNTs were found to give rise to effective fatigue resistance throughout the whole range of stress intensity factor, in addition to significantly enhancing fracture toughness, ductility, Young's modulus and average hardness of the nano-composite by factors of 57%, 60%, 30% and 45% respectively over the matrix as a result of diminished localized cross-linking. Graphene, a one-atom-thick sheet of atoms is a carbon allotrope, which has garnered significant attention of the scientific community and is

  17. A novel method to measure skin mechanical properties with three-dimensional digital image correlation.

    PubMed

    Xu, Z; Dela Cruz, J; Fthenakis, C; Saliou, C

    2018-06-06

    Measuring skin mechanical properties has been of great interest in the skincare industry. It is a high accuracy and non-invasive optical technique which quantitatively tracks skin movement and deformation under mechanical perturbations. A study was conducted with female subjects (25-65 years old). A refined speckle pattern applied onto the skin surface was used for DIC measurements. A unidirectional force pulled the skin at a constant velocity, while the deformation process was quantified by the DIC. Prior to the DIC measurement, Cutometer ® readings were taken on the same area. The DIC protocol's reproducibility across multiple pattern applications, the measurement's repeatability, and the sensitivity in differentiating skin mechanical properties were investigated. Subjects were clustered with statistical significance according to their skin mechanical properties described by six DIC metrics (μ [major strain], σ [major strain], μ [minor strain], σ [minor strain], μ [displacement], and σ [displacement]). Most measurement random errors are below 6%. This is several folds smaller in magnitude than the difference in the mean response between the clusters. Several Cutometer ® parameters also showed good agreement with μ (displacement). DIC was able to differentiate skins of different mechanical qualities. We also proposed the physical significance of the DIC metrics. Some of the DIC metrics potentially offer new insights into skin mechanical properties that complement those revealed by conventional instruments. Accurate measurements, large measurement areas along with ease of direct visualization are substantial advantages of DIC. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  18. Determination of the mechanical and physical properties of cartilage by coupling poroelastic-based finite element models of indentation with artificial neural networks.

    PubMed

    Arbabi, Vahid; Pouran, Behdad; Campoli, Gianni; Weinans, Harrie; Zadpoor, Amir A

    2016-03-21

    One of the most widely used techniques to determine the mechanical properties of cartilage is based on indentation tests and interpretation of the obtained force-time or displacement-time data. In the current computational approaches, one needs to simulate the indentation test with finite element models and use an optimization algorithm to estimate the mechanical properties of cartilage. The modeling procedure is cumbersome, and the simulations need to be repeated for every new experiment. For the first time, we propose a method for fast and accurate estimation of the mechanical and physical properties of cartilage as a poroelastic material with the aid of artificial neural networks. In our study, we used finite element models to simulate the indentation for poroelastic materials with wide combinations of mechanical and physical properties. The obtained force-time curves are then divided into three parts: the first two parts of the data is used for training and validation of an artificial neural network, while the third part is used for testing the trained network. The trained neural network receives the force-time curves as the input and provides the properties of cartilage as the output. We observed that the trained network could accurately predict the properties of cartilage within the range of properties for which it was trained. The mechanical and physical properties of cartilage could therefore be estimated very fast, since no additional finite element modeling is required once the neural network is trained. The robustness of the trained artificial neural network in determining the properties of cartilage based on noisy force-time data was assessed by introducing noise to the simulated force-time data. We found that the training procedure could be optimized so as to maximize the robustness of the neural network against noisy force-time data. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Microstructure and mechanical properties of sheep horn.

    PubMed

    Zhu, Bing; Zhang, Ming; Zhao, Jian

    2016-07-01

    The sheep horn presents outstanding mechanical properties of impact resistance and energy absorption, which suits the need of the vehicle bumper design, but the mechanism behind this phenomenon is less investigated. The microstructure and mechanical properties of the sheep horn of Small Tailed Han Sheep (Ovis aries) living in northeast China were investigated in this article. The effect of sampling position and orientation of the sheep horn sheath on mechanical properties were researched by tensile and compression tests. Meanwhile, the surface morphology and microstructure of the sheep horn were observed using scanning electron microscopy (SEM). The formation mechanism of the mechanical properties of the sheep horn was investigated by biological coupling analysis. The analytical results indicated that the outstanding mechanical properties of the sheep horn are determined by configuration, structure, surface morphology and material coupling elements. These biological coupling elements make the sheep horn possess super characteristics of crashworthiness and energy absorption through the internal coupling mechanism. We suppose that these findings would make a difference in vehicle bumper design. Microsc. Res. Tech. 79:664-674, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  20. Chronic alcohol abuse in men alters bone mechanical properties by affecting both tissue mechanical properties and microarchitectural parameters.

    PubMed

    Cruel, M; Granke, M; Bosser, C; Audran, M; Hoc, T

    2017-06-01

    Alcohol-induced secondary osteoporosis in men has been characterized by higher fracture prevalence and a modification of bone microarchitecture. Chronic alcohol consumption impairs bone cell activity and results in an increased fragility. A few studies highlighted effects of heavy alcohol consumption on some microarchitectural parameters of trabecular bone. But to date and to our knowledge, micro- and macro-mechanical properties of bone of alcoholic subjects have not been investigated. In the present study, mechanical properties and microarchitecture of trabecular bone samples from the iliac crest of alcoholic male patients (n=15) were analyzed and compared to a control group (n=8). Nanoindentation tests were performed to determine the tissue's micromechanical properties, micro-computed tomography was used to measure microarchitectural parameters, and numerical simulations provided the apparent mechanical properties of the samples. Compared to controls, bone tissue from alcoholic patients exhibited an increase of micromechanical properties at tissue scale, a significant decrease of apparent mechanical properties at sample scale, and significant changes in several microarchitectural parameters. In particular, a crucial role of structure model index (SMI) on mechanical properties was identified. 3D microarchitectural parameters are at least as important as bone volume fraction to predict bone fracture risk in the case of alcoholic patients. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  1. Determining the mechanical properties of rat skin with digital image speckle correlation.

    PubMed

    Guan, E; Smilow, Sarah; Rafailovich, Miriam; Sokolov, Jonathan

    2004-01-01

    Accurate measurement of the mechanical properties of skin has numerous implications in surgical repair, dermal disorders and the diagnosis and treatment of trauma to the skin. Investigation of facial wrinkle formation, as well as research in the areas of skin aging and cosmetic product assessment can also benefit from alternative methodologies for the measurement of mechanical properties. A noncontact, noninvasive technique, digital image speckle correlation (DISC), has been successfully introduced to measure the deformation field of a skin sample loaded by a material test machine. With the force information obtained from the loading device, the mechanical properties of the skin, such as Young's modulus, linear limitation and material strength, can be calculated using elastic or viscoelastic theory. The DISC method was used to measure the deformation of neonatal rat skin, with and without a glycerin-fruit-oil-based cream under uniaxial tension. Deformation to failure procedure of newborn rat skin was recorded and analyzed. Single skin layer failures were observed and located by finding the strain concentration. Young's moduli of freshly excised rat skin, cream-processed rat skin and unprocessed rat skin, 24 h after excision, were found with tensile tests to be 1.6, 1.4 and 0.7 MPa, respectively. Our results have shown that DISC provides a novel technique for numerous applications in dermatology and reconstructive surgeries. Copyright 2004 S. Karger AG, Basel

  2. Nanostructured Composites: Effective Mechanical Property Determination of Nanotube Bundles

    NASA Technical Reports Server (NTRS)

    Saether, E.; Pipes, R. B.; Frankland, S. J. V.

    2002-01-01

    Carbon nanotubes naturally tend to form crystals in the form of hexagonally packed bundles or ropes that should exhibit a transversely isotropic constitutive behavior. Although the intratube axial stiffness is on the order of 1 TPa due to a strong network of delocalized bonds, the intertube cohesive strength is orders of magnitude less controlled by weak, nonbonding van der Waals interactions. An accurate determination of the effective mechanical properties of nanotube bundles is important to assess potential structural applications such as reinforcement in future composite material systems. A direct method for calculating effective material constants is developed in the present study. The Lennard-Jones potential is used to model the nonbonding cohesive forces. A complete set of transverse moduli are obtained and compared with existing data.

  3. Mechanical properties experimental investigation of HTPB propellant after thermal accelerated aging

    NASA Astrophysics Data System (ADS)

    Yang, Xiaohong; Sun, Chaoxiang; Zhang, Junfa; Xu, Jinsheng; Tan, Bingdong

    2017-04-01

    To get accurate aging mechanical properties of aged HTPB propellant, the thermal accelerated aging experiment method is utilized and the uniaxial tensile experiments were conducted to obtain the mechanical data of aged HTPB propellants, and the maximum tensile strength, σm, maximum tensile strain, ɛm, and the fracture tensile strain, ɛb, of HTPB propellant with different aging time and various aging temperatures,were obtained, using universal material testing machine. The experimental results show that the σm of HTPB propellant initially increases, subsequently decreases and finally increases with aging time. The ɛm and ɛb generally decrease with increasing aging time, what's more, the decrease rate of both ɛm and ɛb reduce with the aging time. What's more, the postcure effect and oxidation reaction occurred inside HTPB matrix, including the chain degradation reaction and oxidation-induced crosslinking, were discussed to explain the mechanical aging rule of HTPB propellant.

  4. Emerging technologies for the non-invasive characterization of physical-mechanical properties of tablets.

    PubMed

    Dave, Vivek S; Shahin, Hend I; Youngren-Ortiz, Susanne R; Chougule, Mahavir B; Haware, Rahul V

    2017-10-30

    The density, porosity, breaking force, viscoelastic properties, and the presence or absence of any structural defects or irregularities are important physical-mechanical quality attributes of popular solid dosage forms like tablets. The irregularities associated with these attributes may influence the drug product functionality. Thus, an accurate and efficient characterization of these properties is critical for successful development and manufacturing of a robust tablets. These properties are mainly analyzed and monitored with traditional pharmacopeial and non-pharmacopeial methods. Such methods are associated with several challenges such as lack of spatial resolution, efficiency, or sample-sparing attributes. Recent advances in technology, design, instrumentation, and software have led to the emergence of newer techniques for non-invasive characterization of physical-mechanical properties of tablets. These techniques include near infrared spectroscopy, Raman spectroscopy, X-ray microtomography, nuclear magnetic resonance (NMR) imaging, terahertz pulsed imaging, laser-induced breakdown spectroscopy, and various acoustic- and thermal-based techniques. Such state-of-the-art techniques are currently applied at various stages of development and manufacturing of tablets at industrial scale. Each technique has specific advantages or challenges with respect to operational efficiency and cost, compared to traditional analytical methods. Currently, most of these techniques are used as secondary analytical tools to support the traditional methods in characterizing or monitoring tablet quality attributes. Therefore, further development in the instrumentation and software, and studies on the applications are necessary for their adoption in routine analysis and monitoring of tablet physical-mechanical properties. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Mechanical property characterization of intraply hybrid composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sinclair, J. H.

    1979-01-01

    An investigation of the mechanical properties of intraply hybrids made from graphite fiber/epoxy matrix hybridized with secondary S-glass or Kevlar 49 fiber composites is presented. The specimen stress-strain behavior was determined, showing that mechanical properties of intraply hybrid composites can be measured with available methods such as the ten-degree off-axis test for intralaminar shear, and conventional tests for tensile, flexure, and Izod impact properties. The results also showed that combinations of high modulus graphite/S-glass/epoxy matrix composites exist which yield intraply hybrid laminates with the best 'balanced' properties, and that the translation efficiency of mechanical properties from the constituent composites to intraply hybrids may be assessed with a simple equation.

  6. Filler characteristics of modern dental resin composites and their influence on physico-mechanical properties.

    PubMed

    Randolph, Luc D; Palin, William M; Leloup, Gaëtane; Leprince, Julian G

    2016-12-01

    The mechanical properties of dental resin-based composites (RBCs) are highly dependent on filler characteristics (size, content, geometry, composition). Most current commercial materials are marketed as "nanohybrids" (i.e. filler size <1μm). In the present study, filler characteristics of a selection of RBCs were described, aiming at identifying correlations with physico-mechanical properties and testing the relevance of the current classification. Micron/sub-micron particles (> or <500nm) were isolated from 17 commercial RBCs and analyzed by laser diffractrometry and/or electron microscopy. Filler and silane content were evaluated by thermogravimetric analysis and a sedimentation technique. The flexural modulus (E flex ) and strength (σ flex ) and micro-hardness were determined by three-point bending or with a Vickers indenter, respectively. Sorption was also determined. All experiments were carried out after one week of incubation in water or 75/25 ethanol/water. Average size for micron-sized fillers was almost always higher than 1μm. Ranges for mechanical properties were: 3.775wt%) were associated with the highest mechanical properties (E flex and σ flex >12GPa and 130MPa, respectively) and lowest solvent sorption (∼0.3%). Mechanical properties and filler characteristics significantly vary among modern RBCs and the current classification does not accurately illustrate either. Further, the chemical stability of RBCs differed, highlighting differences in resin and silane composition. Since E flex and sorption were well correlated to the filler content, a simple and unambiguous classification based on such characteristic is suggested, with three levels (ultra-low fill, low-fill and compact resin composites). Copyright © 2016 The Academy of Dental Materials. All

  7. Characterization of mechanical properties of pericardium tissue using planar biaxial tension and flexural deformation.

    PubMed

    Murdock, Kyle; Martin, Caitlin; Sun, Wei

    2018-01-01

    Flexure is an important mode of deformation for native and bioprosthetic heart valves. However, mechanical characterization of bioprosthetic leaflet materials has been done primarily through planar tensile testing. In this study, an integrated experimental and computational cantilever beam bending test was performed to characterize the flexural properties of glutaraldehyde-treated bovine and porcine pericardium of different thicknesses. A strain-invariant based structural constitutive model was used to model the pericardial mechanical behavior quantified through the bending tests of this study and the planar biaxial tests previously performed. The model parameters were optimized through an inverse finite element (FE) procedure in order to describe both sets of experimental data. The optimized material properties were implemented in FE simulations of transcatheter aortic valve (TAV) deformation. It was observed that porcine pericardium TAV leaflets experienced significantly more flexure than bovine when subjected to opening pressurization, and that the flexure may be overestimated using a constitutive model derived from purely planar tensile experimental data. Thus, modeling of a combination of flexural and biaxial tensile testing data may be necessary to more accurately describe the mechanical properties of pericardium, and to computationally investigate bioprosthetic leaflet function and design. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Measuring the mechanical properties of plant cells by combining micro-indentation with osmotic treatments.

    PubMed

    Weber, Alain; Braybrook, Siobhan; Huflejt, Michal; Mosca, Gabriella; Routier-Kierzkowska, Anne-Lise; Smith, Richard S

    2015-06-01

    Growth in plants results from the interaction between genetic and signalling networks and the mechanical properties of cells and tissues. There has been a recent resurgence in research directed at understanding the mechanical aspects of growth, and their feedback on genetic regulation. This has been driven in part by the development of new micro-indentation techniques to measure the mechanical properties of plant cells in vivo. However, the interpretation of indentation experiments remains a challenge, since the force measures results from a combination of turgor pressure, cell wall stiffness, and cell and indenter geometry. In order to interpret the measurements, an accurate mechanical model of the experiment is required. Here, we used a plant cell system with a simple geometry, Nicotiana tabacum Bright Yellow-2 (BY-2) cells, to examine the sensitivity of micro-indentation to a variety of mechanical and experimental parameters. Using a finite-element mechanical model, we found that, for indentations of a few microns on turgid cells, the measurements were mostly sensitive to turgor pressure and the radius of the cell, and not to the exact indenter shape or elastic properties of the cell wall. By complementing indentation experiments with osmotic experiments to measure the elastic strain in turgid cells, we could fit the model to both turgor pressure and cell wall elasticity. This allowed us to interpret apparent stiffness values in terms of meaningful physical parameters that are relevant for morphogenesis. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  9. Regional and depth variability of porcine meniscal mechanical properties through biaxial testing.

    PubMed

    Kahlon, A; Hurtig, M B; Gordon, K D

    2015-01-01

    The menisci in the knee joint undergo complex loading in-vivo resulting in a multidirectional stress distribution. Extensive mechanical testing has been conducted to investigate the tissue properties of the knee meniscus, but the testing conditions do not replicate this complex loading regime. Biaxial testing involves loading tissue along two different directions simultaneously, which more accurately simulates physiologic loading conditions. The purpose of this study was to report mechanical properties of meniscal tissue resulting from biaxial testing, while simultaneously investigating regional variations in properties. Ten left, fresh porcine joints were obtained, and the medial and lateral menisci were harvested from each joint (twenty menisci total). Each menisci was divided into an anterior, middle and posterior region; and three slices (femoral, deep and tibial layers) were obtained from each region. Biaxial and constrained uniaxial testing was performed on each specimen, and Young's moduli were calculated from the resulting stress strain curves. Results illustrated significant differences in regional mechanical properties, with the medial anterior (Young's modulus (E)=11.14 ± 1.10 MPa), lateral anterior (E=11.54 ± 1.10 MPa) and lateral posterior (E=9.0 ± 1.2 MPa) regions exhibiting the highest properties compared to the medial central (E=5.0 ± 1.22 MPa), medial posterior (E=4.16 ± 1.13 MPa) and lateral central (E=5.6 ± 1.20 MPa) regions. Differences with depth were also significant on the lateral meniscus, with the femoral (E=12.7 ± 1.22 MPa) and tibial (E=8.6 ± 1.22 MPa) layers exhibiting the highest Young's moduli. This data may form the basis for future modeling of meniscal tissue, or may aid in the design of synthetic replacement alternatives. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Mechanical Properties of Respiratory Muscles

    PubMed Central

    Sieck, Gary C.; Ferreira, Leonardo F.; Reid, Michael B.; Mantilla, Carlos B.

    2014-01-01

    Striated respiratory muscles are necessary for lung ventilation and to maintain the patency of the upper airway. The basic structural and functional properties of respiratory muscles are similar to those of other striated muscles (both skeletal and cardiac). The sarcomere is the fundamental organizational unit of striated muscles and sarcomeric proteins underlie the passive and active mechanical properties of muscle fibers. In this respect, the functional categorization of different fiber types provides a conceptual framework to understand the physiological properties of respiratory muscles. Within the sarcomere, the interaction between the thick and thin filaments at the level of cross-bridges provides the elementary unit of force generation and contraction. Key to an understanding of the unique functional differences across muscle fiber types are differences in cross-bridge recruitment and cycling that relate to the expression of different myosin heavy chain isoforms in the thick filament. The active mechanical properties of muscle fibers are characterized by the relationship between myoplasmic Ca2+ and cross-bridge recruitment, force generation and sarcomere length (also cross-bridge recruitment), external load and shortening velocity (cross-bridge cycling rate), and cross-bridge cycling rate and ATP consumption. Passive mechanical properties are also important reflecting viscoelastic elements within sarcomeres as well as the extracellular matrix. Conditions that affect respiratory muscle performance may have a range of underlying pathophysiological causes, but their manifestations will depend on their impact on these basic elemental structures. PMID:24265238

  11. Mechanical Properties of Organic Semiconductors for Stretchable, Highly Flexible, and Mechanically Robust Electronics.

    PubMed

    Root, Samuel E; Savagatrup, Suchol; Printz, Adam D; Rodriquez, Daniel; Lipomi, Darren J

    2017-05-10

    Mechanical deformability underpins many of the advantages of organic semiconductors. The mechanical properties of these materials are, however, diverse, and the molecular characteristics that permit charge transport can render the materials stiff and brittle. This review is a comprehensive description of the molecular and morphological parameters that govern the mechanical properties of organic semiconductors. Particular attention is paid to ways in which mechanical deformability and electronic performance can coexist. The review begins with a discussion of flexible and stretchable devices of all types, and in particular the unique characteristics of organic semiconductors. It then discusses the mechanical properties most relevant to deformable devices. In particular, it describes how low modulus, good adhesion, and absolute extensibility prior to fracture enable robust performance, along with mechanical "imperceptibility" if worn on the skin. A description of techniques of metrology precedes a discussion of the mechanical properties of three classes of organic semiconductors: π-conjugated polymers, small molecules, and composites. The discussion of each class of materials focuses on molecular structure and how this structure (and postdeposition processing) influences the solid-state packing structure and thus the mechanical properties. The review concludes with applications of organic semiconductor devices in which every component is intrinsically stretchable or highly flexible.

  12. Study of nano mechanical properties polydimethylsiloxane (PDMS)/MWCNT composites

    NASA Astrophysics Data System (ADS)

    Murudkar, Vrishali; Gaonkar, Amita; Deshpande, V. D.; Mhaske, S. T.

    2018-05-01

    Polydimethylsiloxane (PDMS), a clear elastomer, is a common material used in many applications; but has poor mechanical properties. Carbon nano tubes (CNT) exhibit excellent mechanical properties & hence are used as filler in PDMS. It was found that the elastic modulus and strength of the PDMS/MWCNT nano composites were enhanced by adding MWCNT [1]. Through the nano indentation experiment, the hardness (H), the elastic modulus (E), and other mechanical properties can be determined from very small volumes of materials [2]; hence nano indentation is widely used to study mechanical properties. PDMS/MWCNT composites have enhanced mechanical properties over neat PDMS. FTIR analysis shows bonding between MWCNT and PDMS; which affects the mechanical properties. From AFM study it shows decreasing roughness for increasing MWCNT concentration. Surface morphology (SEM) study shows well dispersion of MWCNT into PDMS matrix.

  13. Microstructure, mechanical properties, bio-corrosion properties and antibacterial properties of Ti-Ag sintered alloys.

    PubMed

    Chen, Mian; Zhang, Erlin; Zhang, Lan

    2016-05-01

    In this research, Ag element was selected as an antibacterial agent to develop an antibacterial Ti-Ag alloy by a powder metallurgy. The microstructure, phase constitution, mechanical properties, corrosion resistance and antibacterial properties of the Ti-Ag sintered alloys have been systematically studied by X-ray diffraction (XRD), scanning electron microscope (SEM), compressive test, electrochemical measurements and antibacterial test. The effects of the Ag powder size and the Ag content on the antibacterial property and mechanical property as well as the anticorrosion property have been investigated. The microstructure results have shown that Ti-Ag phase, residual pure Ag and Ti were the mainly phases in Ti-Ag(S75) sintered alloy while Ti2Ag was synthesized in Ti-Ag(S10) sintered alloy. The mechanical test indicated that Ti-Ag sintered alloy showed a much higher hardness and the compressive yield strength than cp-Ti but the mechanical properties were slightly reduced with the increase of Ag content. Electrochemical results showed that Ag powder size had a significant effect on the corrosion resistance of Ti-Ag sintered alloy. Ag content increased the corrosion resistance in a dose dependent way under a homogeneous microstructure. Antibacterial tests have demonstrated that antibacterial Ti-Ag alloy was successfully prepared. It was also shown that the Ag powder particle size and the Ag content influenced the antibacterial activity seriously. The reduction in the Ag powder size was benefit to the improvement in the antibacterial property and the Ag content has to be at least 3wt.% in order to obtain a strong and stable antibacterial activity against Staphylococcus aureus bacteria. The bacterial mechanism was thought to be related to the Ti2Ag and its distribution. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Skin mechanical properties and modeling: A review.

    PubMed

    Joodaki, Hamed; Panzer, Matthew B

    2018-04-01

    The mechanical properties of the skin are important for various applications. Numerous tests have been conducted to characterize the mechanical behavior of this tissue, and this article presents a review on different experimental methods used. A discussion on the general mechanical behavior of the skin, including nonlinearity, viscoelasticity, anisotropy, loading history dependency, failure properties, and aging effects, is presented. Finally, commonly used constitutive models for simulating the mechanical response of skin are discussed in the context of representing the empirically observed behavior.

  15. The Mechanical Properties and Modeling of Creep Behavior of UHMWPE/Nano-HA Composites

    NASA Astrophysics Data System (ADS)

    Li, Fan; Gao, Lilan; Gao, Hong; Cui, Yun

    2017-09-01

    Composites with different levels of hydroxyapatite (HA) content and ultra-high molecular weight polyethylene (UHMWPE) were prepared in this work. Mechanical properties of the composites were examined here, and to evaluate the effect of HA particles on the time-dependent behavior of the pure matrix, the creep and recovery performance of composites at various stress levels were also researched. As expected, the addition of HA influenced the time-dependent response of the UHMWPE and the effect had a strong dependence on the HA content. The creep and recovery strain of the composites significantly decreased with increasing HA content, and tensile properties were also impaired, which was due to the concentration of HA fillers. The mechanism and effect of HA dispersed into the UHMWPE matrix were examined by scanning electron microscopy. Additionally, since variations in the adjusted parameters revealed the impact of HA on the creep behavior of the UHMWPE matrix, Findley's model was employed. The results indicated that the analytical model was accurate for the prediction of creep of the pure matrix and its composites.

  16. Crystal Graph Convolutional Neural Networks for an Accurate and Interpretable Prediction of Material Properties

    NASA Astrophysics Data System (ADS)

    Xie, Tian; Grossman, Jeffrey C.

    2018-04-01

    The use of machine learning methods for accelerating the design of crystalline materials usually requires manually constructed feature vectors or complex transformation of atom coordinates to input the crystal structure, which either constrains the model to certain crystal types or makes it difficult to provide chemical insights. Here, we develop a crystal graph convolutional neural networks framework to directly learn material properties from the connection of atoms in the crystal, providing a universal and interpretable representation of crystalline materials. Our method provides a highly accurate prediction of density functional theory calculated properties for eight different properties of crystals with various structure types and compositions after being trained with 1 04 data points. Further, our framework is interpretable because one can extract the contributions from local chemical environments to global properties. Using an example of perovskites, we show how this information can be utilized to discover empirical rules for materials design.

  17. Glass Fiber Reinforced Polypropylene Mechanical Properties Enhancement by Adhesion Improvement

    PubMed Central

    Etcheverry, Mariana; Barbosa, Silvia E.

    2012-01-01

    Glass fibers (GF) are the reinforcement agent most used in polypropylene (PP) based composites, as they have good balance between properties and costs. However, their final properties are mainly determined by the strength and stability of the polymer-fiber interphase. Fibers do not act as an effective reinforcing material when the adhesion is weak. Also, the adhesion between phases can be easily degraded in aggressive environmental conditions such as high temperatures and/or elevated moisture, and by the stress fields to which the material may be exposed. Many efforts have been done to improve polymer-glass fiber adhesion by compatibility enhancement. The most used techniques include modifications in glass surface, polymer matrix and/or both. However, the results obtained do not show a good costs/properties improvement relationship. The aim of this work is to perform an accurate analysis regarding methods for GF/PP adhesion improvement and to propose a new route based on PP in-situ polymerization onto fibers. This route involves the modification of fibers with an aluminum alkyl and hydroxy-α-olefin and from there to enable the growth of the PP chains using direct metallocenic copolymerization. The adhesion improvements were further proved by fragmentation test, as well as by mechanical properties measurements. The strength and toughness increases three times and the interfacial strength duplicates in PP/GF composites prepared with in-situ polymerized fibers. PMID:28817025

  18. Fabrication of novel silicone capsules with tunable mechanical properties by microfluidic techniques.

    PubMed

    Vilanova, Neus; Rodríguez-Abreu, Carlos; Fernández-Nieves, Alberto; Solans, Conxita

    2013-06-12

    A novel approach for the synthesis of silicone capsules using double W/O/W emulsions as templates is introduced. The low viscosity of the silicone precursors enables the use of microfluidic techniques to accurately control the size and morphology of the double emulsion droplets, which after cross-linking result in the desired monodisperse silicone capsules. Their shell thickness can be finely tuned, which in turn allows control over their permeability and mechanical properties; the latter are particularly important in a variety of practical applications where the capsules are subjected to large external forces. The potential of these capsules for controlled release is also demonstrated using a model hydrophilic substance.

  19. Measurement of mechanical properties of homogeneous tissue with ultrasonically induced shear waves

    NASA Astrophysics Data System (ADS)

    Greenleaf, James F.; Chen, Shigao

    2007-03-01

    Fundamental mechanical properties of tissue are altered by many diseases. Regional and systemic diseases can cause changes in tissue properties. Liver stiffness is caused by cirrhosis and fibrosis. Vascular wall stiffness and tone are altered by smoking, diabetes and other diseases. Measurement of tissue mechanical properties has historically been done with palpation. However palpation is subjective, relative, and not quantitative or reproducible. Elastography in which strain is measured due to stress application gives a qualitative estimate of Young's modulus at low frequency. We have developed a method that takes advantage of the fact that the wave equation is local and shear wave propagation depends only on storage and loss moduli in addition to density, which does not vary much in soft tissues. Our method is called shearwave dispersion ultrasonic velocity measurement (SDUV). The method uses ultrasonic radiation force to produce repeated motion in tissue that induces shear waves to propagate. The shear wave propagation speed is measured with pulse echo ultrasound as a function of frequency of the shear wave. The resulting velocity dispersion curve is fit with a Voight model to determine the elastic and viscous moduli of the tissue. Results indicate accurate and precise measurements are possible using this "noninvasive biopsy" method. Measurements in beef along and across the fibers are consistent with the literature values.

  20. Food mechanical properties and dietary ecology.

    PubMed

    Berthaume, Michael A

    2016-01-01

    Interdisciplinary research has benefitted the fields of anthropology and engineering for decades: a classic example being the application of material science to the field of feeding biomechanics. However, after decades of research, discordances have developed in how mechanical properties are defined, measured, calculated, and used due to disharmonies between and within fields. This is highlighted by "toughness," or energy release rate, the comparison of incomparable tests (i.e., the scissors and wedge tests), and the comparison of incomparable metrics (i.e., the stress and displacement-limited indices). Furthermore, while material scientists report on a myriad of mechanical properties, it is common for feeding biomechanics studies to report on just one (energy release rate) or two (energy release rate and Young's modulus), which may or may not be the most appropriate for understanding feeding mechanics. Here, I review portions of materials science important to feeding biomechanists, discussing some of the basic assumptions, tests, and measurements. Next, I provide an overview of what is mechanically important during feeding, and discuss the application of mechanical property tests to feeding biomechanics. I also explain how 1) toughness measures gathered with the scissors, wedge, razor, and/or punch and die tests on non-linearly elastic brittle materials are not mechanical properties, 2) scissors and wedge tests are not comparable and 3) the stress and displacement-limited indices are not comparable. Finally, I discuss what data gathered thus far can be best used for, and discuss the future of the field, urging researchers to challenge underlying assumptions in currently used methods to gain a better understanding between primate masticatory morphology and diet. © 2016 Wiley Periodicals, Inc.

  1. Review of research on the mechanical properties of the human tooth

    PubMed Central

    Zhang, Ya-Rong; Du, Wen; Zhou, Xue-Dong; Yu, Hai-Yang

    2014-01-01

    ‘Bronze teeth' reflect the mechanical properties of natural teeth to a certain extent. Their mechanical properties resemble those of a tough metal, and the gradient of these properties lies in the direction from outside to inside. These attributes confer human teeth with effective mastication ability. Understanding the various mechanical properties of human teeth and dental materials is the basis for the development of restorative materials. In this study, the elastic properties, dynamic mechanical properties (visco-elasticity) and fracture mechanical properties of enamel and dentin were reviewed to provide a more thorough understanding of the mechanical properties of human teeth. PMID:24743065

  2. Enhancement of mechanical properties of 123 superconductors

    DOEpatents

    Balachandran, Uthamalingam

    1995-01-01

    A composition and method of preparing YBa.sub.2 Cu.sub.3 O.sub.7-x superconductor. Addition of tin oxide containing compounds to YBCO superconductors results in substantial improvement of fracture toughness and other mechanical properties without affect on T.sub.c. About 5-20% additions give rise to substantially improved mechanical properties.

  3. Ultrasonic nondestructive evaluation, microstructure, and mechanical property interrelations

    NASA Technical Reports Server (NTRS)

    Vary, A.

    1984-01-01

    Ultrasonic techniques for mechanical property characterizations are reviewed and conceptual models are advanced for explaining and interpreting the empirically based results. At present, the technology is generally empirically based and is emerging from the research laboratory. Advancement of the technology will require establishment of theoretical foundations for the experimentally observed interrelations among ultrasonic measurements, mechanical properties, and microstructure. Conceptual models are applied to ultrasonic assessment of fracture toughness to illustrate an approach for predicting correlations found among ultrasonic measurements, microstructure, and mechanical properties.

  4. The relationships between deformation mechanisms and mechanical properties of additively manufactured porous biomaterials.

    PubMed

    Kadkhodapour, J; Montazerian, H; Darabi, A Ch; Zargarian, A; Schmauder, S

    2017-06-01

    Modulating deformation mechanism through manipulating morphological parameters of scaffold internal pore architecture provides potential to tailor the overall mechanical properties under physiological loadings. Whereas cells sense local strains, cell differentiation is also impressed by the elastic deformations. In this paper, structure-property relations were developed for Ti6-Al-4V scaffolds designed based on triply periodic minimal surfaces. 10mm cubic scaffolds composed of 5×5×5 unit cells formed of F-RD (bending dominated) and I-WP (stretching dominated) architectures were additively manufactured at different volume fractions and subjected to compressive tests. The first stages of deformation for stretching dominated structure, was accompanied by bilateral layer-by-layer failure of unit cells owing to the buckling of micro-struts, while for bending dominated structure, namely F-RD, global shearing bands appeared since the shearing failure of struts in the internal architecture. Promoted mechanical properties were found for stretching dominated structure since the global orientation of struts were parallel to loading direction while inclination of struts diminished specific properties for bending dominated structure. Moreover, elastic-plastic deformation was computationally studied by applying Johnson-Cook damage model to the voxel-based models in FE analysis. Scaling analysis was performed for mechanical properties with respect to the relative density thereby failure mechanism was correlated to the constants of power law describing mechanical properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Mechanical Deformation Mechanisms and Properties of Prion Fibrils Probed by Atomistic Simulations

    NASA Astrophysics Data System (ADS)

    Choi, Bumjoon; Kim, Taehee; Ahn, Eue Soo; Lee, Sang Woo; Eom, Kilho

    2017-03-01

    Prion fibrils, which are a hallmark for neurodegenerative diseases, have recently been found to exhibit the structural diversity that governs disease pathology. Despite our recent finding concerning the role of the disease-specific structure of prion fibrils in determining their elastic properties, the mechanical deformation mechanisms and fracture properties of prion fibrils depending on their structures have not been fully characterized. In this work, we have studied the tensile deformation mechanisms of prion and non-prion amyloid fibrils by using steered molecular dynamics simulations. Our simulation results show that the elastic modulus of prion fibril, which is formed based on left-handed β-helical structure, is larger than that of non-prion fibril constructed based on right-handed β-helix. However, the mechanical toughness of prion fibril is found to be less than that of non-prion fibril, which indicates that infectious prion fibril is more fragile than non-infectious (non-prion) fibril. Our study sheds light on the role of the helical structure of amyloid fibrils, which is related to prion infectivity, in determining their mechanical deformation mechanisms and properties.

  6. Enhancement of mechanical properties of 123 superconductors

    DOEpatents

    Balachandran, U.

    1995-04-25

    A composition and method are disclosed of preparing YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} superconductor. Addition of tin oxide containing compounds to YBCO superconductors results in substantial improvement of fracture toughness and other mechanical properties without affect on T{sub c}. About 5-20% additions give rise to substantially improved mechanical properties.

  7. Intermolecular potentials and the accurate prediction of the thermodynamic properties of water

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shvab, I.; Sadus, Richard J., E-mail: rsadus@swin.edu.au

    2013-11-21

    The ability of intermolecular potentials to correctly predict the thermodynamic properties of liquid water at a density of 0.998 g/cm{sup 3} for a wide range of temperatures (298–650 K) and pressures (0.1–700 MPa) is investigated. Molecular dynamics simulations are reported for the pressure, thermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, and Joule-Thomson coefficient of liquid water using the non-polarizable SPC/E and TIP4P/2005 potentials. The results are compared with both experiment data and results obtained from the ab initio-based Matsuoka-Clementi-Yoshimine non-additive (MCYna) [J. Li, Z. Zhou, and R. J. Sadus, J. Chem. Phys.more » 127, 154509 (2007)] potential, which includes polarization contributions. The data clearly indicate that both the SPC/E and TIP4P/2005 potentials are only in qualitative agreement with experiment, whereas the polarizable MCYna potential predicts some properties within experimental uncertainty. This highlights the importance of polarizability for the accurate prediction of the thermodynamic properties of water, particularly at temperatures beyond 298 K.« less

  8. Trabecular Bone Mechanical Properties and Fractal Dimension

    NASA Technical Reports Server (NTRS)

    Hogan, Harry A.

    1996-01-01

    Countermeasures for reducing bone loss and muscle atrophy due to extended exposure to the microgravity environment of space are continuing to be developed and improved. An important component of this effort is finite element modeling of the lower extremity and spinal column. These models will permit analysis and evaluation specific to each individual and thereby provide more efficient and effective exercise protocols. Inflight countermeasures and post-flight rehabilitation can then be customized and targeted on a case-by-case basis. Recent Summer Faculty Fellowship participants have focused upon finite element mesh generation, muscle force estimation, and fractal calculations of trabecular bone microstructure. Methods have been developed for generating the three-dimensional geometry of the femur from serial section magnetic resonance images (MRI). The use of MRI as an imaging modality avoids excessive exposure to radiation associated with X-ray based methods. These images can also detect trabecular bone microstructure and architecture. The goal of the current research is to determine the degree to which the fractal dimension of trabecular architecture can be used to predict the mechanical properties of trabecular bone tissue. The elastic modulus and the ultimate strength (or strain) can then be estimated from non-invasive, non-radiating imaging and incorporated into the finite element models to more accurately represent the bone tissue of each individual of interest. Trabecular bone specimens from the proximal tibia are being studied in this first phase of the work. Detailed protocols and procedures have been developed for carrying test specimens through all of the steps of a multi-faceted test program. The test program begins with MRI and X-ray imaging of the whole bones before excising a smaller workpiece from the proximal tibia region. High resolution MRI scans are then made and the piece further cut into slabs (roughly 1 cm thick). The slabs are X-rayed again

  9. Fibrin mechanical properties and their structural origins.

    PubMed

    Litvinov, Rustem I; Weisel, John W

    2017-07-01

    Fibrin is a protein polymer that is essential for hemostasis and thrombosis, wound healing, and several other biological functions and pathological conditions that involve extracellular matrix. In addition to molecular and cellular interactions, fibrin mechanics has been recently shown to underlie clot behavior in the highly dynamic intra- and extravascular environments. Fibrin has both elastic and viscous properties. Perhaps the most remarkable rheological feature of the fibrin network is an extremely high elasticity and stability despite very low protein content. Another important mechanical property that is common to many filamentous protein polymers but not other polymers is stiffening occurring in response to shear, tension, or compression. New data has begun to provide a structural basis for the unique mechanical behavior of fibrin that originates from its complex multi-scale hierarchical structure. The mechanical behavior of the whole fibrin gel is governed largely by the properties of single fibers and their ensembles, including changes in fiber orientation, stretching, bending, and buckling. The properties of individual fibrin fibers are determined by the number and packing arrangements of double-stranded half-staggered protofibrils, which still remain poorly understood. It has also been proposed that forced unfolding of sub-molecular structures, including elongation of flexible and relatively unstructured portions of fibrin molecules, can contribute to fibrin deformations. In spite of a great increase in our knowledge of the structural mechanics of fibrin, much about the mechanisms of fibrin's biological functions remains unknown. Fibrin deformability is not only an essential part of the biomechanics of hemostasis and thrombosis, but also a rapidly developing field of bioengineering that uses fibrin as a versatile biomaterial with exceptional and tunable biochemical and mechanical properties. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Efficient and accurate approach to modeling the microstructure and defect properties of LaCoO3

    NASA Astrophysics Data System (ADS)

    Buckeridge, J.; Taylor, F. H.; Catlow, C. R. A.

    2016-04-01

    Complex perovskite oxides are promising materials for cathode layers in solid oxide fuel cells. Such materials have intricate electronic, magnetic, and crystalline structures that prove challenging to model accurately. We analyze a wide range of standard density functional theory approaches to modeling a highly promising system, the perovskite LaCoO3, focusing on optimizing the Hubbard U parameter to treat the self-interaction of the B-site cation's d states, in order to determine the most appropriate method to study defect formation and the effect of spin on local structure. By calculating structural and electronic properties for different magnetic states we determine that U =4 eV for Co in LaCoO3 agrees best with available experiments. We demonstrate that the generalized gradient approximation (PBEsol +U ) is most appropriate for studying structure versus spin state, while the local density approximation (LDA +U ) is most appropriate for determining accurate energetics for defect properties.

  11. Optimization of mechanical properties, biocorrosion properties and antibacterial properties of wrought Ti-3Cu alloy by heat treatment.

    PubMed

    Bao, Mianmian; Liu, Ying; Wang, Xiaoyan; Yang, Lei; Li, Shengyi; Ren, Jing; Qin, Gaowu; Zhang, Erlin

    2018-03-01

    Previous study has shown that Ti-3Cu alloy shows good antibacterial properties (>90% antibacterial rate), but the mechanical properties still need to be improved. In this paper, a series of heat-treatment processes were selected to adjust the microstructure in order to optimize the properties of Ti-3Cu alloy. Microstructure, mechanical properties, biocorrosion properties and antibacterial properties of wrought Ti-3Cu alloy at different conditions was systematically investigated by X-ray diffraction, optical microscope, scanning electron microscope, transmission electron microscopy, electrochemical measurements, tensile test, fatigue test and antibacterial test. Heat treatment could significantly improve the mechanical properties, corrosion resistance and antibacterial rate due to the redistribution of copper elements and precipitation of Ti 2 Cu phase. Solid solution treatment increased the yield strength from 400 to 740 MPa and improved the antibacterial rate from 33% to 65.2% while aging treatment enhanced the yield strength to 800-850 MPa and antibacterial rate (>91.32%). It was demonstrated that homogeneous distribution and fine Ti 2 Cu phase plays a very important role in mechanical properties, corrosion resistance and antibacterial properties.

  12. A clinically applicable non-invasive method to quantitatively assess the visco-hyperelastic properties of human heel pad, implications for assessing the risk of mechanical trauma.

    PubMed

    Behforootan, Sara; Chatzistergos, Panagiotis E; Chockalingam, Nachiappan; Naemi, Roozbeh

    2017-04-01

    Pathological conditions such as diabetic foot and plantar heel pain are associated with changes in the mechanical properties of plantar soft tissue. However, the causes and implications of these changes are not yet fully understood. This is mainly because accurate assessment of the mechanical properties of plantar soft tissue in the clinic remains extremely challenging. To develop a clinically viable non-invasive method of assessing the mechanical properties of the heel pad. Furthermore the effect of non-linear mechanical behaviour of the heel pad on its ability to uniformly distribute foot-ground contact loads in light of the effect of overloading is also investigated. An automated custom device for ultrasound indentation was developed along with custom algorithms for the automated subject-specific modeling of heel pad. Non-time-dependent and time-dependent material properties were inverse engineered from results from quasi-static indentation and stress relaxation test respectively. The validity of the calculated coefficients was assessed for five healthy participants. The implications of altered mechanical properties on the heel pad's ability to uniformly distribute plantar loading were also investigated in a parametric analysis. The subject-specific heel pad models with coefficients calculated based on quasi-static indentation and stress relaxation were able to accurately simulate dynamic indentation. Average error in the predicted forces for maximum deformation was only 6.6±4.0%. When the inverse engineered coefficients were used to simulate the first instance of heel strike the error in terms of peak plantar pressure was 27%. The parametric analysis indicated that the heel pad's ability to uniformly distribute plantar loads is influenced both by its overall deformability and by its stress-strain behaviour. When overall deformability stays constant, changes in stress/strain behaviour leading to a more "linear" mechanical behaviour appear to improve the heel

  13. Microstructural and Morphological Factors Affecting Uncertainty in Small Scale Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Maughan, Michael R.

    If materials are to be developed from the ground up, the process will be dependent upon accurate and well-defined models of material behavior. These models can be closed-form solutions developed from first principles, simulations, or empirically derived equations, among others. Material behavior at the mesoscale is in general well understood, having had several centuries of study. However, behavior at the micro or nanoscale still requires characterization. Understanding the collective influence of the microstructure on the bulk material, for example with models like the Hall-Petch relation, has advanced our ability to manipulate the material to our advantage. We now have the ability to study not only the structure of the material, but also the material behavior and properties at the nanoscale. Understanding this behavior is critical to developing a framework for interpreting and utilizing these properties in materials design. This research aims to improve the fundamental understanding of the mechanical performance of materials and the subsequent variation in measured properties. The literature reports widely varying material properties such as hardness, elastic modulus, and yield point when measured at the nanoscale. Proposed variation mechanisms in these properties include surface preparation, error in measurement, heterogeneous dislocation density and distribution, crystal orientation, surface oxide film fracture, and others. Among other things, this work shows that these sources of variation can be determined and quantified, and that this information can be utilized as a characterization and/or predictive tool. The main goals of this work are to 1) continue basic research on sources of variation in the nanoscale properties of materials, specifically hardness and modulus in crystalline and glassy solids, 2) study the abrupt transition from elastic to plastic material behavior known as pop-in and resolve the problem of pseudo-elastic behavior prior to plasticity

  14. Metal Additive Manufacturing: A Review of Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Lewandowski, John J.; Seifi, Mohsen

    2016-07-01

    This article reviews published data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples covered in this review include powder bed fusion (e.g., EBM, SLM, DMLS) and directed energy deposition (e.g., LENS, EBF3). Although only a limited number of metallic alloy systems are currently available for additive manufacturing (e.g., Ti-6Al-4V, TiAl, stainless steel, Inconel 625/718, and Al-Si-10Mg), the bulk of the published mechanical properties information has been generated on Ti-6Al-4V. However, summary tables for published mechanical properties and/or key figures are included for each of the alloys listed above, grouped by the additive technique used to generate the data. Published values for mechanical properties obtained from hardness, tension/compression, fracture toughness, fatigue crack growth, and high cycle fatigue are included for as-built, heat-treated, and/or HIP conditions, when available. The effects of test orientation/build direction on properties, when available, are also provided, along with discussion of the potential source(s) (e.g., texture, microstructure changes, defects) of anisotropy in properties. Recommendations for additional work are also provided.

  15. Tools for Accurate and Efficient Analysis of Complex Evolutionary Mechanisms in Microbial Genomes. Final Report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nakhleh, Luay

    I proposed to develop computationally efficient tools for accurate detection and reconstruction of microbes' complex evolutionary mechanisms, thus enabling rapid and accurate annotation, analysis and understanding of their genomes. To achieve this goal, I proposed to address three aspects. (1) Mathematical modeling. A major challenge facing the accurate detection of HGT is that of distinguishing between these two events on the one hand and other events that have similar "effects." I proposed to develop a novel mathematical approach for distinguishing among these events. Further, I proposed to develop a set of novel optimization criteria for the evolutionary analysis of microbialmore » genomes in the presence of these complex evolutionary events. (2) Algorithm design. In this aspect of the project, I proposed to develop an array of e cient and accurate algorithms for analyzing microbial genomes based on the formulated optimization criteria. Further, I proposed to test the viability of the criteria and the accuracy of the algorithms in an experimental setting using both synthetic as well as biological data. (3) Software development. I proposed the nal outcome to be a suite of software tools which implements the mathematical models as well as the algorithms developed.« less

  16. Mechanical, Thermal and Dynamic Mechanical Properties of PP/GF/xGnP Nanocomposites

    NASA Astrophysics Data System (ADS)

    Ashenai Ghasemi, F.; Ghorbani, A.; Ghasemi, I.

    2017-03-01

    The mechanical, thermal, and dynamic mechanical properties of ternary nanocomposites based on polypropylene, short glass fibers, and exfoliated graphene nanoplatelets were studied. To investigate the mechanical properties, uniaxial tensile and Charpy impact tests were carried out. To study the crystallinity of the compositions, a DSC test was performed. A dynamic mechanical analysis was used to characterize the storage modulus and loss factor (tan δ). The morphology of the composites was studied by a scanning electron microscope (SEM). The results obtained are presented in tables and graphics.

  17. Machine learning predictions of molecular properties: Accurate many-body potentials and nonlocality in chemical space

    DOE PAGES

    Hansen, Katja; Biegler, Franziska; Ramakrishnan, Raghunathan; ...

    2015-06-04

    Simultaneously accurate and efficient prediction of molecular properties throughout chemical compound space is a critical ingredient toward rational compound design in chemical and pharmaceutical industries. Aiming toward this goal, we develop and apply a systematic hierarchy of efficient empirical methods to estimate atomization and total energies of molecules. These methods range from a simple sum over atoms, to addition of bond energies, to pairwise interatomic force fields, reaching to the more sophisticated machine learning approaches that are capable of describing collective interactions between many atoms or bonds. In the case of equilibrium molecular geometries, even simple pairwise force fields demonstratemore » prediction accuracy comparable to benchmark energies calculated using density functional theory with hybrid exchange-correlation functionals; however, accounting for the collective many-body interactions proves to be essential for approaching the “holy grail” of chemical accuracy of 1 kcal/mol for both equilibrium and out-of-equilibrium geometries. This remarkable accuracy is achieved by a vectorized representation of molecules (so-called Bag of Bonds model) that exhibits strong nonlocality in chemical space. The same representation allows us to predict accurate electronic properties of molecules, such as their polarizability and molecular frontier orbital energies.« less

  18. Machine Learning Predictions of Molecular Properties: Accurate Many-Body Potentials and Nonlocality in Chemical Space

    PubMed Central

    2015-01-01

    Simultaneously accurate and efficient prediction of molecular properties throughout chemical compound space is a critical ingredient toward rational compound design in chemical and pharmaceutical industries. Aiming toward this goal, we develop and apply a systematic hierarchy of efficient empirical methods to estimate atomization and total energies of molecules. These methods range from a simple sum over atoms, to addition of bond energies, to pairwise interatomic force fields, reaching to the more sophisticated machine learning approaches that are capable of describing collective interactions between many atoms or bonds. In the case of equilibrium molecular geometries, even simple pairwise force fields demonstrate prediction accuracy comparable to benchmark energies calculated using density functional theory with hybrid exchange-correlation functionals; however, accounting for the collective many-body interactions proves to be essential for approaching the “holy grail” of chemical accuracy of 1 kcal/mol for both equilibrium and out-of-equilibrium geometries. This remarkable accuracy is achieved by a vectorized representation of molecules (so-called Bag of Bonds model) that exhibits strong nonlocality in chemical space. In addition, the same representation allows us to predict accurate electronic properties of molecules, such as their polarizability and molecular frontier orbital energies. PMID:26113956

  19. Mechanical Properties of Recycled Concrete in Marine Environment

    PubMed Central

    Wang, Jianxiu; Huang, Tianrong; Liu, Xiaotian; Wu, Pengcheng; Guo, Zhiying

    2013-01-01

    Experimental work was carried out to develop information about mechanical properties of recycled concrete (RC) in marine environment. By using the seawater and dry-wet circulation to simulate the marine environment, specimens of RC were tested with different replacement percentages of 0%, 30%, and 60% after immersing in seawater for 4, 8, 12, and 16 months, respectively. Based on the analysis of the stress-strain curves (SSCs) and compressive strength, it is revealed that RC' peak value and elastic modulus decreased with the increase of replacement percentage and corroding time in marine environment. And the failure of recycled concrete was speeded up with more obvious cracks and larger angles of 65° to 85° in the surface when compared with normal concrete. Finally, the grey model (GM) with equal time intervals was constructed to investigate the law of compressive strength of recycled concrete in marine environment, and it is found that the GM is accurate and feasible for the prediction of RC compressive strength in marine environment. PMID:23766707

  20. Mechanical Properties of Transcription

    NASA Astrophysics Data System (ADS)

    Sevier, Stuart A.; Levine, Herbert

    2017-06-01

    The mechanical properties of transcription have recently been shown to play a central role in gene expression. However, a full physical characterization of this central biological process is lacking. In this Letter, we introduce a simple description of the basic physical elements of transcription where RNA elongation, RNA polymerase rotation, and DNA supercoiling are coupled. The resulting framework describes the relative amount of RNA polymerase rotation and DNA supercoiling that occurs during RNA elongation. Asymptotic behavior is derived and can be used to experimentally extract unknown mechanical parameters of transcription. Mechanical limits to transcription are incorporated through the addition of a DNA supercoiling-dependent RNA polymerase velocity. This addition can lead to transcriptional stalling and resulting implications for gene expression, chromatin structure and genome organization are discussed.

  1. Mechanical properties of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Salvetat, J.-P.; Bonard, J.-M.; Thomson, N. H.; Kulik, A. J.; Forró, L.; Benoit, W.; Zuppiroli, L.

    A variety of outstanding experimental results on the elucidation of the elastic properties of carbon nanotubes are fast appearing. These are based mainly on the techniques of high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM) to determine the Young's moduli of single-wall nanotube bundles and multi-walled nanotubes, prepared by a number of methods. These results are confirming the theoretical predictions that carbon nanotubes have high strength plus extraordinary flexibility and resilience. As well as summarising the most notable achievements of theory and experiment in the last few years, this paper explains the properties of nanotubes in the wider context of materials science and highlights the contribution of our research group in this rapidly expanding field. A deeper understanding of the relationship between the structural order of the nanotubes and their mechanical properties will be necessary for the development of carbon-nanotube-based composites. Our research to date illustrates a qualitative relationship between the Young's modulus of a nanotube and the amount of disorder in the atomic structure of the walls. Other exciting results indicate that composites will benefit from the exceptional mechanical properties of carbon nanotubes, but that the major outstanding problem of load transfer efficiency must be overcome before suitable engineering materials can be produced.

  2. Exploration of mechanisms underlying the strain-rate-dependent mechanical property of single chondrocytes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nguyen, Trung Dung; Gu, YuanTong, E-mail: yuantong.gu@qut.edu.au

    2014-05-05

    Based on the characterization by Atomic Force Microscopy, we report that the mechanical property of single chondrocytes has dependency on the strain-rates. By comparing the mechanical deformation responses and the Young's moduli of living and fixed chondrocytes at four different strain-rates, we explore the deformation mechanisms underlying this dependency property. We found that the strain-rate-dependent mechanical property of living cells is governed by both of the cellular cytoskeleton and the intracellular fluid when the fixed chondrocytes are mainly governed by their intracellular fluid, which is called the consolidation-dependent deformation behavior. Finally, we report that the porohyperelastic constitutive material model whichmore » can capture the consolidation-dependent behavior of both living and fixed chondrocytes is a potential candidature to study living cell biomechanics.« less

  3. Mechanical Properties of Aerogels

    NASA Technical Reports Server (NTRS)

    Parmenter, Kelly E.; Milstein, Frederick

    1995-01-01

    Aerogels are extremely low density solids that are characterized by a high porosity and pore sizes on the order of nanometers. Their low thermal conductivity and sometimes transparent appearance make them desirable for applications such as insulation in cryogenic vessels and between double paned glass in solar architecture. An understanding of the mechanical properties of aerogels is necessary before aerogels can be used in load bearing applications. In the present study, the mechanical behavior of various types of fiber-reinforced silica aerogels was investigated with hardness, compression, tension and shear tests. Particular attention was paid to the effects of processing parameters, testing conditions, storage environment, and age on the aerogels' mechanical response. The results indicate that the addition of fibers to the aerogel matrix generally resulted in softer, weaker materials with smaller elastic moduli. Furthermore, the testing environment significantly affected compression results. Tests in ethanol show an appreciable amount of scatter, and are not consistent with results for tests in air. In fact, the compression specimens appeared to crack and begin to dissolve upon exposure to the ethanol solution. This is consistent with the inherent hydrophobic nature of these aerogels. In addition, the aging process affected the aerogels' mechanical behavior by increasing their compressive strength and elastic moduli while decreasing their strain at fracture. However, desiccation of the specimens did not appreciably affect the mechanical properties, even though it reduced the aerogel density by removing trapped moisture. Finally, tension and shear test results indicate that the shear strength of the aerogels exceeds the tensile strength. This is consistent with the response of brittle materials. Future work should concentrate on mechanical testing at cryogenic temperatures, and should involve more extensive tensile tests. Moreover, before the mechanical response

  4. Mechanical, electronic and thermodynamic properties of full Heusler compounds Fe2VX(X = Al, Ga)

    NASA Astrophysics Data System (ADS)

    Khalfa, M.; Khachai, H.; Chiker, F.; Baki, N.; Bougherara, K.; Yakoubi, A.; Murtaza, G.; Harmel, M.; Abu-Jafar, M. S.; Omran, S. Bin; Khenata, R.

    2015-11-01

    The electronic structure, mechanical and thermodynamic properties of Fe2VX, (with X = Al and Ga), have been studied self consistently by employing state-of-the-art full-potential linearized approach of augmented plane wave plus local orbitals (FP-LAPW + lo) method. The exchange-correlation potential is treated with the local density and generalized gradient approximations (LDA and GGA). Our predicted ground state properties such as lattice constants, bulk modulus and elastic constants appear more accurate when we employed the GGA rather than the LDA, and these results are in very good agreement with the available experimental and theoretical data. Further, thermodynamic properties of Fe2VAl and Fe2VGa are predicted with pressure and temperature in the ranges of 0-40 GPa and 0-1500 K using the quasi-harmonic Debye model. We have obtained successfully the variations of the heat capacities, primitive cell volume and volume expansion coefficient.

  5. EVALUATION OF THE MECHANICAL PROPERTIES OF 9NI-4CO FORGINGS.

    DTIC Science & Technology

    FORGING, MECHANICAL PROPERTIES, STEEL , QUENCHING, SPECIFICATIONS, TENSILE PROPERTIES, COMPRESSIVE PROPERTIES, FATIGUE(MECHANICS), TOUGHNESS, STRESS...CORROSION, THERMAL STABILITY, STRAIN(MECHANICS), BAINITE , TEST METHODS, HEAT TREATMENT, CRACK PROPAGATION.

  6. Mechanical properties of additively manufactured octagonal honeycombs.

    PubMed

    Hedayati, R; Sadighi, M; Mohammadi-Aghdam, M; Zadpoor, A A

    2016-12-01

    Honeycomb structures have found numerous applications as structural and biomedical materials due to their favourable properties such as low weight, high stiffness, and porosity. Application of additive manufacturing and 3D printing techniques allows for manufacturing of honeycombs with arbitrary shape and wall thickness, opening the way for optimizing the mechanical and physical properties for specific applications. In this study, the mechanical properties of honeycomb structures with a new geometry, called octagonal honeycomb, were investigated using analytical, numerical, and experimental approaches. An additive manufacturing technique, namely fused deposition modelling, was used to fabricate the honeycomb from polylactic acid (PLA). The honeycombs structures were then mechanically tested under compression and the mechanical properties of the structures were determined. In addition, the Euler-Bernoulli and Timoshenko beam theories were used for deriving analytical relationships for elastic modulus, yield stress, Poisson's ratio, and buckling stress of this new design of honeycomb structures. Finite element models were also created to analyse the mechanical behaviour of the honeycombs computationally. The analytical solutions obtained using Timoshenko beam theory were close to computational results in terms of elastic modulus, Poisson's ratio and yield stress, especially for relative densities smaller than 25%. The analytical solutions based on the Timoshenko analytical solution and the computational results were in good agreement with experimental observations. Finally, the elastic properties of the proposed honeycomb structure were compared to those of other honeycomb structures such as square, triangular, hexagonal, mixed, diamond, and Kagome. The octagonal honeycomb showed yield stress and elastic modulus values very close to those of regular hexagonal honeycombs and lower than the other considered honeycombs. Copyright © 2016 Elsevier B.V. All rights

  7. Enhancing Aluminum Reactivity by Exploiting Surface Chemistry and Mechanical Properties

    DTIC Science & Technology

    2015-06-01

    alter its mechanical properties . In bulk material processing , annealing and quenching metals such as Al can relieve residual stress and improve...increasing  Al  reactivity is to alter its mechanical  properties .  In bulk material  processing , annealing and quenching metals such as  Al  can relieve...mechanical properties . On a single particle level, affecting mechanical properties may also affect Al particle reactivity. Aluminum particles underwent

  8. Mechanical properties of nanocrystalline cobalt

    NASA Astrophysics Data System (ADS)

    Karimpoor, Amir A.; Erb, Uwe

    2006-05-01

    Due to their excellent wear and corrosion properties, nanocrystalline cobalt and several cobalt alloys made by electrodeposition are currently being developed as environmentally benign replacement coatings for hard chromium electrodeposits. The focus of this study is on the mechanical properties of nanocrystalline cobalt, which are currently not well understood. A comparison is presented for hardness, tensile properties, Charpy impact properties and fracture surface analysis of both nanocrystalline (grain size: 12 nm) and conventional polycrystalline (grain size: 4.8 m) cobalt. It is shown that the hardness and tensile strength of nanocrystalline cobalt is 2-3 times higher than for polycrystalline cobalt. However, in contrast to other nanocrystalline materials tested previously, nanocrystalline cobalt retains considerable ductility with elongation to fracture values up to 7%.

  9. Hierarchical structure and mechanical properties of remineralized dentin.

    PubMed

    Chen, Yi; Wang, Jianming; Sun, Jian; Mao, Caiyun; Wang, Wei; Pan, Haihua; Tang, Ruikang; Gu, Xinhua

    2014-12-01

    It is widely accepted that the mechanical properties of dentin are significantly determined by its hierarchical structure. The current correlation between the mechanical properties and the hierarchical structure was mainly established by studying altered forms of dentin, which limits the potential outcome of the research. In this study, dentins with three different hierarchical structures were obtained via two different remineralization procedures and at different remineralization stages: (1) a dentin structure with amorphous minerals incorporated into the collagen fibrils, (2) a dentin with crystallized nanominerals incorporated into the collagen fibrils, and (3) a dentin with an out-of-order mineral layer filling the collagen fibrils matrix. Nanoindentation tests were performed to investigate the mechanical behavior of the remineralized dentin slides. The results showed that the incorporation of the crystallized nanominerals into the acid-etched demineralized organic fibrils resulted in a remarkable improvement of the mechanical properties of the dentin. In contrast, for the other two structures, i.e. the amorphous minerals inside the collagen fibrils and the out-of-order mineral layer within the collagen fibrils matrix, the excellent mechanical properties of dentin could not be restored. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Modeling the mechanics of cancer: effect of changes in cellular and extra-cellular mechanical properties.

    PubMed

    Katira, Parag; Bonnecaze, Roger T; Zaman, Muhammad H

    2013-01-01

    Malignant transformation, though primarily driven by genetic mutations in cells, is also accompanied by specific changes in cellular and extra-cellular mechanical properties such as stiffness and adhesivity. As the transformed cells grow into tumors, they interact with their surroundings via physical contacts and the application of forces. These forces can lead to changes in the mechanical regulation of cell fate based on the mechanical properties of the cells and their surrounding environment. A comprehensive understanding of cancer progression requires the study of how specific changes in mechanical properties influences collective cell behavior during tumor growth and metastasis. Here we review some key results from computational models describing the effect of changes in cellular and extra-cellular mechanical properties and identify mechanistic pathways for cancer progression that can be targeted for the prediction, treatment, and prevention of cancer.

  11. Rationally designed synthetic protein hydrogels with predictable mechanical properties.

    PubMed

    Wu, Junhua; Li, Pengfei; Dong, Chenling; Jiang, Heting; Bin Xue; Gao, Xiang; Qin, Meng; Wang, Wei; Bin Chen; Cao, Yi

    2018-02-12

    Designing synthetic protein hydrogels with tailored mechanical properties similar to naturally occurring tissues is an eternal pursuit in tissue engineering and stem cell and cancer research. However, it remains challenging to correlate the mechanical properties of protein hydrogels with the nanomechanics of individual building blocks. Here we use single-molecule force spectroscopy, protein engineering and theoretical modeling to prove that the mechanical properties of protein hydrogels are predictable based on the mechanical hierarchy of the cross-linkers and the load-bearing modules at the molecular level. These findings provide a framework for rationally designing protein hydrogels with independently tunable elasticity, extensibility, toughness and self-healing. Using this principle, we demonstrate the engineering of self-healable muscle-mimicking hydrogels that can significantly dissipate energy through protein unfolding. We expect that this principle can be generalized for the construction of protein hydrogels with customized mechanical properties for biomedical applications.

  12. Residual Stress Induced Mechanical Property Enhancement in Steel Encapsulated Light Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Fudger, Sean James

    Macro hybridized systems consisting of steel encapsulated light metal matrix composites (MMCs) were produced with the goal of creating a low cost/light weight composite system with enhanced mechanical properties. MMCs are frequently incorporated into advanced material systems due to their tailorable material properties. However, they often have insufficient ductility for many structural applications. The macro hybridized systems take advantage of the high strength, modulus, and damage tolerance of steels and high specific stiffness and low density of MMCs while mitigating the high density of steels and the poor ductility of MMCs. Furthermore, a coefficient of thermal expansion (CTE) mismatch induced residual compressive stress method is utilized as a means of improving the ductility of the MMCs and overall efficiency of the macro hybridized systems. Systems consisting of an A36, 304 stainless steel, or NitronicRTM 50 stainless steel shell filled with an Al-SiC, Al-Al2O3, or Mg-B4C MMC are evaluated in this work. Upon cooling from processing temperatures, residual strains are generated due to a CTE mismatch between each of the phases. The resulting systems offer higher specific properties and a more structurally efficient system can be attained. Mechanical testing was performed and improvements in yield stress, ultimate tensile stress, and ductility were observed. However, the combination of these dissimilar materials often results in the formation of intermetallic compounds. In certain loading situations, these typically brittle intermetallic layers can result in degraded performance. X-ray Diffraction (XRD), X-ray Energy Dispersive Spectroscopy (EDS), and Electron Backscatter Diffraction (EBSD) are utilized to characterize the intermetallic layer formation at the interface between the steel and MMC. As the residual stress condition in each phase has a large impact on the mechanical property improvement, accurate quantification of these strains/stresses is

  13. Magnetic Resonance Poroelastography: An Algorithm for Estimating the Mechanical Properties of Fluid-Saturated Soft Tissues

    PubMed Central

    Perriñez, Phillip R.; Kennedy, Francis E.; Van Houten, Elijah E. W.; Weaver, John B.; Paulsen, Keith D.

    2010-01-01

    Magnetic Resonance Poroelastography (MRPE) is introduced as an alternative to single-phase model-based elastographic reconstruction methods. A three-dimensional (3D) finite element poroelastic inversion algorithm was developed to recover the mechanical properties of fluid-saturated tissues. The performance of this algorithm was assessed through a variety of numerical experiments, using synthetic data to probe its stability and sensitivity to the relevant model parameters. Preliminary results suggest the algorithm is robust in the presence of noise and capable of producing accurate assessments of the underlying mechanical properties in simulated phantoms. Further, a 3D time-harmonic motion field was recorded for a poroelastic phantom containing a single cylindrical inclusion and used to assess the feasibility of MRPE image reconstruction from experimental data. The elastograms obtained from the proposed poroelastic algorithm demonstrate significant improvement over linearly elastic MRE images generated using the same data. In addition, MRPE offers the opportunity to estimate the time-harmonic pressure field resulting from tissue excitation, highlighting the potential for its application in the diagnosis and monitoring of disease processes associated with changes in interstitial pressure. PMID:20199912

  14. Simulated Hail Ice Mechanical Properties and Failure Mechanism at Quasi-Static Strain Rates

    NASA Astrophysics Data System (ADS)

    Swift, Jonathan M.

    Hail is a significant threat to aircraft both on the ground and in the air. Aeronautical engineers are interested in better understanding the properties of hail to improve the safety of new aircraft. However, the failure mechanism and mechanical properties of hail, as opposed to clear ice, are not well understood. A literature review identifies basic mechanical properties of ice and a failure mechanism based upon the state of stress within an ice sphere is proposed. To better understand the properties of Simulated Hail Ice (SHI), several tests were conducted using both clear and cotton fiber reinforced ice. Pictures were taken to show the internal crystal structure of SHI. SHI crush tests were conducted to identify the overall force-displacement trends at various quasi-static strain rates. High speed photography was also used to visually track the failure mechanism of spherical SHI. Compression tests were done to measure the compression strength of SHI and results were compared to literature data. Fracture toughness tests were conducted to identify the crack resistance of SHI. Results from testing clear ice samples were successfully compared to previously published literature data to instill confidence in the testing methods. The methods were subsequently used to test and characterize the cotton fiber reinforced ice.

  15. Isotropic microscale mechanical properties of coral skeletons

    PubMed Central

    Pasquini, Luca; Molinari, Alan; Fantazzini, Paola; Dauphen, Yannicke; Cuif, Jean-Pierre; Levy, Oren; Dubinsky, Zvy; Caroselli, Erik; Prada, Fiorella; Goffredo, Stefano; Di Giosia, Matteo; Reggi, Michela; Falini, Giuseppe

    2015-01-01

    Scleractinian corals are a major source of biogenic calcium carbonate, yet the relationship between their skeletal microstructure and mechanical properties has been scarcely studied. In this work, the skeletons of two coral species: solitary Balanophyllia europaea and colonial Stylophora pistillata, were investigated by nanoindentation. The hardness HIT and Young's modulus EIT were determined from the analysis of several load–depth data on two perpendicular sections of the skeletons: longitudinal (parallel to the main growth axis) and transverse. Within the experimental and statistical uncertainty, the average values of the mechanical parameters are independent on the section's orientation. The hydration state of the skeletons did not affect the mechanical properties. The measured values, EIT in the 76–77 GPa range, and HIT in the 4.9–5.1 GPa range, are close to the ones expected for polycrystalline pure aragonite. Notably, a small difference in HIT is observed between the species. Different from corals, single-crystal aragonite and the nacreous layer of the seashell Atrina rigida exhibit clearly orientation-dependent mechanical properties. The homogeneous and isotropic mechanical behaviour of the coral skeletons at the microscale is correlated with the microstructure, observed by electron microscopy and atomic force microscopy, and with the X-ray diffraction patterns of the longitudinal and transverse sections. PMID:25977958

  16. Microstructure and Mechanical Properties of Porous Mullite

    NASA Astrophysics Data System (ADS)

    Hsiung, Chwan-Hai Harold

    Mullite (3 Al2O3 : 2 SiO2) is a technologically important ceramic due to its thermal stability, corrosion resistance, and mechanical robustness. One variant, porous acicular mullite (ACM), has a unique needle-like microstructure and is the material platform for The Dow Chemical Company's diesel particulate filter AERIFY(TM). The investigation described herein focuses on the microstructure-mechanical property relationships in acicular mullites as well as those with traditional porous microstructures with the goal of illuminating the critical factors in determining their modulus, strength, and toughness. Mullites with traditional pore morphologies were made to serve as references via slipcasting of a kaolinite-alumina-starch slurry. The starch was burned out to leave behind a pore network, and the calcined body was then reaction-sintered at 1600C to form mullite. The samples had porosities of approximately 60%. Pore size and shape were altered by using different starch templates, and pore size was found to influence the stiffness and toughness. The ACM microstructure was varied along three parameters: total porosity, pore size, and needle size. Total porosity was found to dominate the mechanical behavior of ACM, while increases in needle and pore size increased the toughness at lower porosities. ACM was found to have much improved (˜130%) mechanical properties relative to its non-acicular counterpart at the same porosity. A second set of investigations studied the role of the intergranular glassy phase which wets the needle intersections of ACM. Removal of the glassy phase via an HF etch reduced the mechanical properties by ˜30%, highlighting the intergranular phase's importance to the enhanced mechanical properties of ACM. The composition of the glassy phase was altered by doping the ACM precursor with magnesium and neodymium. Magnesium doping resulted in ACM with greatly reduced fracture strength and toughness. Studies showed that the mechanical properties of the

  17. In Vitro Tissue Differentiation using Dynamics of Tissue Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Lin, Wei-Chiang; Phillips, Paul J.

    2002-03-01

    Dynamics of tissue mechanical properties of various human tissue types were studied at macroscopic as well as microscopic level in vitro. This study was conducted to enable the development of a feedback system based on dynamics of tissue mechanical properties for intraoperative guidance for tumor treatment (e.g., RF ablation of liver tumor) and noninvasive tumor localization. Human liver tissues, including normal, cancerous, and cirrhotic tissues, were obtained from patients receiving liver transplant or tumor resection at Vanderbilt University Medical Center with the approval of the Vanderbilt Institutional Review Board. Tissue samples, once resected from the patients, were snap-frozen using liquid nitrogen and stored at -70 oC. Measurements of the mechanical properties of these tissue samples were conducted at the University of Tennessee at Knoxville. Dynamics of tissue mechanical properties were measured from both native and thermally coagulated tissue samples at macroscopic and microscopic level. Preliminary results suggest the dynamics of mechanical properties of normal liver tissues are very different from those of cancerous liver tissues. The correlation between the dynamics of mechanical properties at macroscopic level and those at microscopic level is currently under investigation.

  18. Mechanical properties of wood

    Treesearch

    David W. Green; Jerrold E. Winandy; David E. Kretschmann

    1999-01-01

    The mechanical properties presented in this chapter were obtained from tests of small pieces of wood termed “clear” and “straight grained” because they did not contain characteristics such as knots, cross grain, checks, and splits. These test pieces did have anatomical characteristics such as growth rings that occurred in consistent patterns within each piece. Clear...

  19. Mechanical properties of wood

    Treesearch

    David Kretschmann

    2010-01-01

    The mechanical properties presented in this chapter were obtained from tests of pieces of wood termed “clear” and “straight grained” because they did not contain characteristics such as knots, cross grain, checks, and splits. These test pieces did have anatomical characteristics such as growth rings that occurred in consistent patterns within each piece. Clear wood...

  20. Investigation of mechanical properties of cryogenically treated music wire

    NASA Astrophysics Data System (ADS)

    Heptonstall, A.; Waller, M.; Robertson, N. A.

    2015-08-01

    It has been reported that treating music wire (high carbon steel wire) by cooling to cryogenic temperatures can enhance its mechanical properties with particular reference to those properties important for musical performance. We use such wire for suspending many of the optics in Advanced LIGO, the upgrade to LIGO—the Laser Interferometric Gravitational-Wave Observatory. Two properties that particularly interest us are mechanical loss and breaking strength. A decrease in mechanical loss would directly reduce the thermal noise associated with the suspension, thus enhancing the noise performance of mirror suspensions within the detector. An increase in strength could allow thinner wire to be safely used, which would enhance the dilution factor of the suspension, again leading to lower suspension thermal noise. In this article, we describe the results of an investigation into some of the mechanical properties of music wire, comparing untreated wire with the same wire which has been cryogenically treated. For the samples we studied, we conclude that there is no significant difference in the properties of interest for application in gravitational wave detectors.

  1. Microstructure and mechanical properties of horns derived from three domestic bovines.

    PubMed

    Zhang, Quan-bin; Li, Chun; Pan, Yan-ting; Shan, Guang-hua; Cao, Ping; He, Jia; Lin, Zhong-shi; Ao, Ning-jian; Huang, Yao-xiong

    2013-12-01

    The microstructure and mechanical properties of horns derived from three domestic bovines (buffalo, cattle and sheep) were examined. The effects of water content, sampling position and orientation of three bovid horns on mechanical properties were systematically investigated by uniaxial tension and micron indentation tests. Meanwhile, the material composition and metal element contents were determined by Raman spectroscopy and elemental analysis respectively, and the microstructures of the horns were measured by scanning electron microscopy (SEM). Results show that the mechanical properties of horns have negative correlation with water contents and depend on sampling position and orientation. The spatial variations of the mechanical properties in horns are attributed to the different keratinization degrees in the proximal, middle and distal parts. And the mechanical properties of horns in the longitudinal direction are better than those in transverse. Among the three kinds of horns, the mechanical properties of buffalo horn are the best, followed by cattle horn, and those in sheep horn are the worst. This is due to the differences in material composition, metal element, and the microstructures of the horns. But the mechanical properties of buffalo horns are not dependent on the source of the buffalo. Therefore, regular engineered buffalo keratinous materials with standard mechanical properties can be obtained from different buffalo horns by using proper preparation methods. © 2013.

  2. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing.

    PubMed

    Luecke, William E; Slotwinski, John A

    2014-01-01

    Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands.

  3. Measurements and Characterizations of Mechanical Properties of Human Skins

    NASA Astrophysics Data System (ADS)

    Song, Han Wook; Park, Yon Kyu

    A skin is an indispensible organ for humans because it contributes to metabolism using its own biochemical functions and protects the human body from external stimuli. Recently, mechanical properties such as a thickness, a friction and an elastic coefficient have been used as a decision index in the skin physiology and in the skin care market due to the increased awareness of wellbeing issues. In addition, the use of mechanical properties is known to have good discrimination ability in the classification of human constitutions, which are used in the field of an alternative medicine. In this study, a system that measures mechanical properties such as a friction and an elastic coefficient is designed. The equipment consists of a load cell type (manufactured by the authors) for the measurements of a friction coefficient, a decompression tube for the measurement of an elastic coefficient. Using the proposed system, the mechanical properties of human skins from different constitutions were compared, and the relative repeatability error for measurements of mechanical properties was determined to be less than 2%. Combining the inspection results of medical doctors in the field of an alternative medicine, we could conclude that the proposed system might be applicable to a quantitative constitutional diagnosis between human constitutions within an acceptable level of uncertainty.

  4. Method of predicting mechanical properties of decayed wood

    DOEpatents

    Kelley, Stephen S.

    2003-07-15

    A method for determining the mechanical properties of decayed wood that has been exposed to wood decay microorganisms, comprising: a) illuminating a surface of decayed wood that has been exposed to wood decay microorganisms with wavelengths from visible and near infrared (VIS-NIR) spectra; b) analyzing the surface of the decayed wood using a spectrometric method, the method generating a first spectral data of wavelengths in VIS-NIR spectra region; and c) using a multivariate analysis to predict mechanical properties of decayed wood by comparing the first spectral data with a calibration model, the calibration model comprising a second spectrometric method of spectral data of wavelengths in VIS-NIR spectra obtained from a reference decay wood, the second spectral data being correlated with a known mechanical property analytical result obtained from the reference decayed wood.

  5. Mechanical Properties of Stable Glasses Using Nanoindentation

    NASA Astrophysics Data System (ADS)

    Wolf, Sarah; Liu, Tianyi; Jiang, Yijie; Ablajan, Keyume; Zhang, Yue; Walsh, Patrick; Turner, Kevin; Fakhraai, Zahra

    Glasses with enhanced stability over ordinary, liquid quenched glasses have been formed via the process of Physical Vapor Deposition (PVD) by using a sufficiently slow deposition rate and a substrate temperature slightly below the glass transition temperature. These stable glasses have been shown to exhibit higher density, lower enthalpy, and better kinetic stability over ordinary glass, and are typically optically birefringent, due to packing and orientational anisotropy. Given these exceptional properties, it is of interest to further investigate how the properties of stable glasses compare to those of ordinary glass. In particular, the mechanical properties of stable glasses remain relatively under-investigated. While the speed of sound and elastic moduli have been shown to increase with increased stability, little is known about their hardness and fracture toughness compared to ordinary glasses. In this study, glasses of 9-(3,5-di(naphthalen-1-yl)phenyl)anthracene were deposited at varying temperatures relative to their glass transition temperature, and their mechanical properties measured by nanoindentation. Hardness and elastic modulus of the glasses were compared across substrate temperatures. After indentation, the topography of these films were studied using Atomic Force Microscopy (AFM) in order to further compare the relationship between thermodynamic and kinetic stability and mechanical failure. Z.F. and P.W. acknowledge funding from NSF(DMREF-1628407).

  6. Mechanical properties of composite materials

    NASA Technical Reports Server (NTRS)

    Thornton, H. Richard; Cornwell, L. R.

    1993-01-01

    A composite material incorporates high strength, high modulus fibers in a matrix (polymer, metal, or ceramic). The fibers may be oriented in a manner to give varying in-plane properties (longitudinal, transverse-stress, strain, and modulus of elasticity). The lay-up of the composite laminates is such that a center line of symmetry and no bending moment exist through the thickness. The laminates are tabbed, with either aluminum or fiberglass, and are ready for tensile testing. The determination of the tensile properties of resin matrix composites, reinforced by continuous fibers, is outlined in ASTM standard D 3039, Tensile Properties of Oriented Fiber Composites. The tabbed flat tensile coupons are placed into the grips of a tensile machine and load-deformation curves plotted. The load-deformation data are translated into stress-strain curves for determination of mechanical properties (ultimate tensile strength and modulus of elasticity).

  7. Database of Mechanical Properties of Textile Composites

    NASA Technical Reports Server (NTRS)

    Delbrey, Jerry

    1996-01-01

    This report describes the approach followed to develop a database for mechanical properties of textile composites. The data in this database is assembled from NASA Advanced Composites Technology (ACT) programs and from data in the public domain. This database meets the data documentation requirements of MIL-HDBK-17, Section 8.1.2, which describes in detail the type and amount of information needed to completely document composite material properties. The database focuses on mechanical properties of textile composite. Properties are available for a range of parameters such as direction, fiber architecture, materials, environmental condition, and failure mode. The composite materials in the database contain innovative textile architectures such as the braided, woven, and knitted materials evaluated under the NASA ACT programs. In summary, the database contains results for approximately 3500 coupon level tests, for ten different fiber/resin combinations, and seven different textile architectures. It also includes a limited amount of prepreg tape composites data from ACT programs where side-by-side comparisons were made.

  8. Determinants of the mechanical properties of bones

    NASA Technical Reports Server (NTRS)

    Martin, R. B.

    1991-01-01

    The mechanical properties of bones are governed by the same principles as those of man-made load-bearing structures, but the organism is able to adapt its bone structure to changes in skeletal loading. In this overview of the determinants of the strength and stiffness of bone, a continuum approach has been taken, in which the behavior of a macroscopic structure depends on its shape and size, and on the mechanical properties of the material within. The latter are assumed to depend on the composition (porosity and mineralization) and organization (trabecular or cortical bone architecture, collagen fiber orientation, fatigue damage) of the bone. The effects of each of these factors are reviewed. Also, the possible means of non-invasively estimating the strength or other mechanical properties of a bone are reviewed, including quantitative computed tomography, photon absorptiometry, and ultrasonic measurements. The best estimates of strength have been obtained with photon absorptiometry and computed tomography, which at best are capable of accounting for 90% of the strength variability in a simple in vitro test, but results from different laboratories have been highly variable.

  9. Mechanical property characterization of polymeric composites reinforced by continuous microfibers

    NASA Astrophysics Data System (ADS)

    Zubayar, Ali

    Innumerable experimental works have been conducted to study the effect of polymerization on the potential properties of the composites. Experimental techniques are employed to understand the effects of various fibers, their volume fractions and matrix properties in polymer composites. However, these experiments require fabrication of various composites which are time consuming and cost prohibitive. Advances in computational micromechanics allow us to study the various polymer based composites by using finite element simulations. The mechanical properties of continuous fiber composite strands are directional. In traditional continuous fiber laminated composites, all fibers lie in the same plane. This provides very desirable increases in the in-plane mechanical properties, but little in the transverse mechanical properties. The effect of different fiber/matrix combinations with various orientations is also available. Overall mechanical properties of different micro continuous fiber reinforced composites with orthogonal geometry are still unavailable in the contemporary research field. In this research, the mechanical properties of advanced polymeric composite reinforced by continuous micro fiber will be characterized based on analytical investigation and FE computational modeling. Initially, we have chosen IM7/PEEK, Carbon Fiber/Nylon 6, and Carbon Fiber/Epoxy as three different case study materials for analysis. To obtain the equivalent properties of the micro-hetero structures, a concept of micro-scale representative volume elements (RVEs) is introduced. Five types of micro scale RVEs (3 square and 2 hexagonal) containing a continuous micro fiber in the polymer matrix were designed. Uniaxial tensile, lateral expansion and transverse shear tests on each RVE were designed and conducted by the finite element computer modeling software ANSYS. The formulae based on elasticity theory were derived for extracting the equivalent mechanical properties (Young's moduli, shear

  10. Mechanical Properties of the TiAl IRIS Alloy

    NASA Astrophysics Data System (ADS)

    Voisin, Thomas; Monchoux, Jean-Philippe; Thomas, Marc; Deshayes, Christophe; Couret, Alain

    2016-12-01

    This paper presents a study of the mechanical properties at room and high temperature of the boron and tungsten containing IRIS alloy (Ti-48Al-2W-0.08B at. pct). This alloy was densified by Spark Plasma Sintering (SPS). The resultant microstructure consists of small lamellar colonies surrounded by γ regions containing B2 precipitates. Tensile tests are performed from room temperature to 1273 K (1000 °C). Creep properties are determined at 973 K (700 °C)/300 MPa, 1023 K (750 °C)/120 MPa, and 1023 K (750 °C)/200 MPa. The tensile strength and the creep resistance at high temperature are found to be very high compared to the data reported in the current literature while a plastic elongation of 1.6 pct is preserved at room temperature. A grain size dependence of both ductility and strength is highlighted at room temperature. The deformation mechanisms are studied by post-mortem analyses on deformed samples and by in situ straining experiments, both performed in a transmission electron microscope. In particular, a low mobility of non-screw segments of dislocations at room temperature and the activation of a mixed-climb mechanism during creep have been identified. The mechanical properties of this IRIS alloy processed by SPS are compared to those of other TiAl alloys developed for high-temperature structural applications as well as to those of similar tungsten containing alloys obtained by more conventional processing techniques. Finally, the relationships between mechanical properties and microstructural features together with the elementary deformation mechanisms are discussed.

  11. Obtaining and Mechanical Properties of Ti-Mo-Zr-Ta Alloys

    NASA Astrophysics Data System (ADS)

    Bălţatu, M. S.; Vizureanu, P.; Geantă, V.; Nejneru, C.; Țugui, C. A.; Focşăneanu, S. C.

    2017-06-01

    Ti-based alloys are successfully used in the area of orthopedic biomaterials for their enhanced biocompatibility, good corrosion and mechanical properties. The most suitable metals as an alloying element for orthopedic biomaterials are zirconium, molybdenum and tantalum because are non toxic and have good properties. The paper purpose development of two alloys of Ti-Mo-Zr-Ta (TMZT) prepared by arc-melting with several mechanical properties determined by microindentation. The mechanical properties analyzed was Vickers hardness and dynamic elasticity modulus. The investigated alloys presents a low Young’s modulus, an important condition of biomaterials for preventing stress shielding phenomenon.

  12. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing

    PubMed Central

    Luecke, William E; Slotwinski, John A

    2014-01-01

    Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands. PMID:26601037

  13. Mechanical properties of atomic layer deposition-reinforced nanoparticle thin films.

    PubMed

    Zhang, Lei; Prosser, Jacob H; Feng, Gang; Lee, Daeyeon

    2012-10-21

    Nanoparticle thin films (NTFs) exhibit multifunctionality, making them useful for numerous advanced applications including energy storage and conversion, biosensing and photonics. Poor mechanical reliability and durability of NTFs, however, limit their industrial and commercial applications. Atomic layer deposition (ALD) represents a unique opportunity to enhance the mechanical properties of NTFs at a relatively low temperature without drastically changing their original structure and functionality. In this work, we study how ALD of different materials, Al(2)O(3), TiO(2), and SiO(2), affects the mechanical properties of TiO(2) and SiO(2) NTFs. Our results demonstrate that the mechanical properties of ALD-reinforced NTFs are dominantly influenced by the mechanical properties of the ALD materials rather than by the compositional matching between ALD and nanoparticle materials. Among the three ALD materials, Al(2)O(3) ALD provides the best enhancement in the modulus and hardness of the NTFs. Interestingly, Al(2)O(3) ALD is able to enhance not only the modulus and hardness but also the toughness of NTFs. Our study presents an additional benefit of depositing nanometer scale ALD layers in NTFs; that is, we find that the hardness and modulus of ultrathin ALD layers (<5 nm) can be estimated from the mechanical properties of ALD-reinforced NTFs using a simple mixing rule. This investigation also provides insight into the use of nanoindentation for testing the mechanical properties of ultrathin ALD-reinforced NTFs.

  14. Mechanical Properties and Failure of Biopolymers: Atomistic Reactions to Macroscale Response

    PubMed Central

    Jung, GangSeob; Qin, Zhao

    2017-01-01

    The behavior of chemical bonding under various mechanical loadings is an intriguing mechanochemical property of biological materials, and the property plays a critical role in determining their deformation and failure mechanisms. Because of their astonishing mechanical properties and roles in constituting the basis of a variety of physiologically relevant materials, biological protein materials have been intensively studied. Understanding the relation between chemical bond networks (structures) and their mechanical properties offers great possibilities to enable new materials design in nanotechnology and new medical treatments for human diseases. Here we focus on how the chemical bonds in biological systems affect mechanical properties and how they change during mechanical deformation and failure. Three representative cases of biomaterials related to the human diseases are discussed in case studies, including: amyloids, intermediate filaments, and collagen, each describing mechanochemical features and how they relate to the pathological conditions at multiple scales. PMID:26108895

  15. Mechanical properties of water desalination and wastewater treatment membranes

    DOE PAGES

    Wang, Kui; Abdalla, Ahmed A.; Khaleel, Mohammad A.; ...

    2017-07-13

    Applications of membrane technology in water desalination and wastewater treatment have increased significantly in the past fewdecades due to itsmany advantages over otherwater treatment technologies.Water treatment membranes provide high flux and contaminant rejection ability and require good mechanical strength and durability. Thus, assessing the mechanical properties of water treatment membranes is critical not only to their design, but also for studying their failure mechanisms, including the surface damage, mechanical and chemical ageing, delamination and loss of dimensional stability of the membranes. The various experimental techniques to assess themechanical properties ofwastewater treatment and desalinationmembranes are reviewed. Uniaxial tensile test, bending test,more » dynamic mechanical analysis, nanoindentation and bursting tests are the most widely used mechanical characterization methods for water treatment membranes. Mechanical degradations induced by fouling, chemical cleaning as well as membrane delamination are then discussed. Moreover, in order to study the membranesmechanical responses under similar loading conditions, the stress-state of the membranes are analyzed and advanced mechanical testing approaches are proposed. Lastly, some perspectives are highlighted to study the structure-properties relationship for wastewater treatment and water desalination membranes.« less

  16. Mechanical properties of water desalination and wastewater treatment membranes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Kui; Abdalla, Ahmed A.; Khaleel, Mohammad A.

    Applications of membrane technology in water desalination and wastewater treatment have increased significantly in the past fewdecades due to itsmany advantages over otherwater treatment technologies.Water treatment membranes provide high flux and contaminant rejection ability and require good mechanical strength and durability. Thus, assessing the mechanical properties of water treatment membranes is critical not only to their design, but also for studying their failure mechanisms, including the surface damage, mechanical and chemical ageing, delamination and loss of dimensional stability of the membranes. The various experimental techniques to assess themechanical properties ofwastewater treatment and desalinationmembranes are reviewed. Uniaxial tensile test, bending test,more » dynamic mechanical analysis, nanoindentation and bursting tests are the most widely used mechanical characterization methods for water treatment membranes. Mechanical degradations induced by fouling, chemical cleaning as well as membrane delamination are then discussed. Moreover, in order to study the membranesmechanical responses under similar loading conditions, the stress-state of the membranes are analyzed and advanced mechanical testing approaches are proposed. Lastly, some perspectives are highlighted to study the structure-properties relationship for wastewater treatment and water desalination membranes.« less

  17. Mechanical and microwave absorbing properties of carbon-filled polyurethane.

    PubMed

    Kucerová, Z; Zajícková, L; Bursíková, V; Kudrle, V; Eliás, M; Jasek, O; Synek, P; Matejková, J; Bursík, J

    2009-01-01

    Polyurethane (PU) matrix composites were prepared with various carbon fillers at different filler contents in order to investigate their structure, mechanical and microwave absorbing properties. As fillers, flat carbon microparticles, carbon microfibers and multiwalled carbon nanotubes (MWNT) were used. The microstructure of the composite was examined by scanning electron microscopy and transmission electron microscopy. Mechanical properties, namely universal hardness, plastic hardness, elastic modulus and creep were assessed by means of depth sensing indentation test. Mechanical properties of PU composite filled with different fillers were investigated and the composite always exhibited higher hardness, elastic modulus and creep resistance than un-filled PU. Influence of filler shape, content and dispersion was also investigated.

  18. Shell-binary nanoparticle materials with variable electrical and electro-mechanical properties.

    PubMed

    Zhang, P; Bousack, H; Dai, Y; Offenhäusser, A; Mayer, D

    2018-01-18

    Nanoparticle (NP) materials with the capability to adjust their electrical and electro-mechanical properties facilitate applications in strain sensing technology. Traditional NP materials based on single component NPs lack a systematic and effective means of tuning their electrical and electro-mechanical properties. Here, we report on a new type of shell-binary NP material fabricated by self-assembly with either homogeneous or heterogeneous arrangements of NPs. Variable electrical and electro-mechanical properties were obtained for both materials. We show that the electrical and electro-mechanical properties of these shell-binary NP materials are highly tunable and strongly affected by the NP species as well as their corresponding volume fraction ratio. The conductivity and the gauge factor of these shell-binary NP materials can be altered by about five and two orders of magnitude, respectively. These shell-binary NP materials with different arrangements of NPs also demonstrate different volume fraction dependent electro-mechanical properties. The shell-binary NP materials with a heterogeneous arrangement of NPs exhibit a peaking of the sensitivity at medium mixing ratios, which arises from the aggregation induced local strain enhancement. Studies on the electron transport regimes and micro-morphologies of these shell-binary NP materials revealed the different mechanisms accounting for the variable electrical and electro-mechanical properties. A model based on effective medium theory is used to describe the electrical and electro-mechanical properties of such shell-binary nanomaterials and shows an excellent match with experiment data. These shell-binary NP materials possess great potential applications in high-performance strain sensing technology due to their variable electrical and electro-mechanical properties.

  19. Investigation of the influence of the composition on mechanical properties of polylactide

    NASA Astrophysics Data System (ADS)

    Baikin, A. S.; Sevostyanov, M. A.; Nasakina, E. O.; Sergienko, K. V.; Kaplan, M. A.; Konushkin, S. V.; Kolmakova, A. A.; Yakubov, A. D.; Kolmakov, A. G.

    2018-04-01

    In this paper we describe the creation of films from polylactide. Studied the mechanical properties of developed polymer films of polylactide. The effect of the molecular weight of polylactide on the mechanical properties of the resulting polymer films is shown. The dependence of the mechanical properties of polylactide films on the polymer concentration in chloroform was studied. The possibility of creating biodegradable films with specified mechanical properties is shown.

  20. Mechanical properties of intra-ocular lenses

    NASA Astrophysics Data System (ADS)

    Ehrmann, Klaus; Kim, Eon; Parel, Jean-Marie

    2008-02-01

    Cataract surgery usually involves the replacement of the natural crystalline lens with a rigid or foldable intraocular lens to restore clear vision for the patient. While great efforts have been placed on optimising the shape and optical characteristics of IOLs, little is know about the mechanical properties of these devices and how they interact with the capsular bag once implanted. Mechanical properties measurements were performed on 8 of the most commonly implanted IOLs using a custom build micro tensometer. Measurement data will be presented for the stiffness of the haptic elements, the buckling resistance of foldable IOLs, the dynamic behaviour of the different lens materials and the axial compressibility. The biggest difference between the lens types was found between one-piece and 3-piece lenses with respect to the flexibility of the haptic elements

  1. Study on the mechanical properties of Cu/LDPE composite IUDs.

    PubMed

    Tang, Ying; Xia, Xianping; Wang, Yun; Xie, Changsheng

    2011-03-01

    The copper/low-density polyethylene composite (Cu/LDPE composite) intrauterine devices (IUDs), which can eliminate or lessen the side effects of existing IUDs, have been developed in our laboratory. As a novel type of copper-containing IUDs, it is not clear whether the mechanical properties of the Cu/LDPE composite IUDs can meet the need of clinical use or not. Therefore, the mechanical properties of the Cu/LDPE composite IUDs have been studied in the present article. The influence of copper particle content and size on the mechanical properties of the Cu/LDPE composite IUDs was analyzed firstly to provide guidance for the material composition design of the Cu/LDPE composite IUDs, and then the BaSO(4)/LDPE composite, which has been applied as a framework of the existing copper-containing IUDs in clinical use for decades, has been used as reference to judge whether the mechanical properties of the Cu/LDPE composite IUDs can meet the need of clinical use or not. However, the mechanical properties of IUDs cannot be characterized directly. Therefore, the mechanical properties of both the Cu/LDPE composite IUDs and the framework of the existing copper-containing IUDs were investigated by means of tensile test using standard tensile samples, and the fracture surface morphology of the tensile samples was characterized by scanning electron microscopy (SEM). Both the elongation at break and the tensile strength decrease with increasing of copper particle content and increase with increasing of the copper particle size, while the elastic modulus shows an opposite tendency. The tensile strength and elastic modulus of both the Cu/LDPE microcomposite IUDs and the Cu/LDPE nanocomposite IUDs with 25 wt.% of copper particles are higher than those of existing copper-containing IUDs (TCu220C; its framework is made of the BaSO(4)/LDPE composite with 20 wt.% of BaSO(4)). The content and size of the copper particles have significant effect on the mechanical properties of Cu

  2. Measurement of material mechanical properties in microforming

    NASA Astrophysics Data System (ADS)

    Yun, Wang; Xu, Zhenying; Hui, Huang; Zhou, Jianzhong

    2006-02-01

    As the rapid market need of micro-electro-mechanical systems engineering gives it the wide development and application ranging from mobile phones to medical apparatus, the need of metal micro-parts is increasing gradually. Microforming technology challenges the plastic processing technology. The findings have shown that if the grain size of the specimen remains constant, the flow stress changes with the increasing miniaturization, and also the necking elongation and the uniform elongation etc. It is impossible to get the specimen material properties in conventional tensile test machine, especially in the high precision demand. Therefore, one new measurement method for getting the specimen material-mechanical property with high precision is initiated. With this method, coupled with the high speed of Charge Coupled Device (CCD) camera and high precision of Coordinate Measuring Machine (CMM), the elongation and tensile strain in the gauge length are obtained. The elongation, yield stress and other mechanical properties can be calculated from the relationship between the images and CCD camera movement. This measuring method can be extended into other experiments, such as the alignment of the tool and specimen, micro-drawing process.

  3. Characterization of Mechanical Properties of Microbial Biofilms

    NASA Astrophysics Data System (ADS)

    Callison, Elizabeth; Gose, James; Perlin, Marc; Ceccio, Steven

    2017-11-01

    The physical properties of microbial biofilms grown subject to shear flows determine the form and mechanical characteristics of the biofilm structure, and consequently, the turbulent interactions over and through the biofilm. These biofilms - sometimes referred to as slime - are comprised of microbial cells and extracellular polymeric substance (EPS) matrices that surround the multicellular communities. Some of the EPSs take the form of streamers that tend to oscillate in flows, causing increased turbulent mixing and drag. As the presence of EPS governs the compliance and overall stability of the filamentous streamers, investigation of the mechanical properties of biofilms may also inform efforts to understand hydrodynamic performance of fouled systems. In this study, a mixture of four diatom genera was grown under turbulent shear flow on test panels. The mechanical properties and hydrodynamic performance of the biofilm were investigated using rheology and turbulent flow studies in the Skin-Friction Flow Facility at the University of Michigan. The diatoms in the mixture of algae were identified, and the elastic and viscous moduli were determined from small-amplitude oscillations, while a creep test was used to evaluate the biofilm compliance.

  4. Controlling Mechanical Properties of Bis-leucine Oxalyl Amide Gels

    NASA Astrophysics Data System (ADS)

    Chang, William; Carvajal, Daniel; Shull, Kenneth

    2011-03-01

    is-leucine oxalyl amide is a low molecular weight gelator capable of gelling polar and organic solvents. A fundamental understanding of self-assembled systems can lead to new methods in drug delivery and the design of new soft material systems. An important feature of self-assembled systems are the intermolecular forces between solvent and gelator molecule; by changing the environment the gel is in, the mechanical properties also change. In this project two variables were considered: the degree of neutralization present for the gelator molecule from neutral to completely ionized, and the concentration of the gelator molecule, from 1 weight percent to 8 weight percent in 1-butanol. Mechanical properties were studied using displacement controlled indentation techniques and temperature sweep rheometry. It has been found that properties such as the storage modulus, gelation temperature and maximum stress allowed increase with bis-leucine oxalyl amide concentration. The results from this study establish a 3-d contour map between the gelator concentration, the gelator degree of ionization and mechanical properties such as storage modulus and maximum stress allowed. The intermolecular forces between the bis-leucine low molecular weight gelator and 1-butanol govern the mechanical properties of the gel system, and understanding these interactions will be key to rationally designed self-assembled systems.

  5. Effect of Terminal Modification on the Molecular Assembly and Mechanical Properties of Protein-Based Block Copolymers.

    PubMed

    Jacobsen, Matthew M; Tokareva, Olena S; Ebrahimi, Davoud; Huang, Wenwen; Ling, Shengjie; Dinjaski, Nina; Li, David; Simon, Marc; Staii, Cristian; Buehler, Markus J; Kaplan, David L; Wong, Joyce Y

    2017-09-01

    Accurate prediction and validation of the assembly of bioinspired peptide sequences into fibers with defined mechanical characteristics would aid significantly in designing and creating materials with desired properties. This process may also be utilized to provide insight into how the molecular architecture of many natural protein fibers is assembled. In this work, computational modeling and experimentation are used in tandem to determine how peptide terminal modification affects a fiber-forming core domain. Modeling shows that increased terminal molecular weight and hydrophilicity improve peptide chain alignment under shearing conditions and promote consolidation of semicrystalline domains. Mechanical analysis shows acute improvements to strength and elasticity, but significantly reduced extensibility and overall toughness. These results highlight an important entropic function that terminal domains of fiber-forming peptides exhibit as chain alignment promoters, which ultimately has notable consequences on the mechanical behavior of the final fiber products. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Comparison of mechanical properties for polyamide 12 composite-based biomaterials fabricated by fused filament fabrication and injection molding

    NASA Astrophysics Data System (ADS)

    Rahim, Tuan Noraihan Azila Tuan; Abdullah, Abdul Manaf; Akil, Hazizan Md; Mohamad, Dasmawati

    2016-12-01

    The emergence of 3D printing technology known as fused filament fabrication (FFF) has offered the possibility of producing an anatomically accurate, patient specific implant with more affordable prices. The only weakness of this technology is related to incompatibility and lack of properties of current material to be applied in biomedical. Therefore, this study aims to develop a new, polymer composite-based biomaterial that exhibits a high processability using FFF technique, strong enough and shows acceptable biocompatibility, and safe for biomedical use. Polyamide 12 (PA12), which meets all these requirements was incorporated with two bioceramic fillers, zirconia and hydroxyapatite in order to improve the mechanical and bioactivity properties. The obtained mechanical properties were compared with injection-molded specimens and also a commercial biomedical product, HAPEXTM which is composed of hydroxyapatite and polyethylene. The yield strength and modulus of the PA12 composites increased steadily with increasing filler loading. Although the strength of printed PA12 composites were reduced compared with injection molded specimen, but still higher than HAPEXTM material. The higher surface roughness obtained by printed PA12 was expected to enhance the cell adhesion and provide better implant fixation.

  7. Mechanical properties of normal versus cancerous breast cells

    PubMed Central

    Smelser, Amanda M.; Macosko, Jed C.; O’Dell, Adam P.; Smyre, Scott; Bonin, Keith

    2016-01-01

    A cell’s mechanical properties are important in determining its adhesion, migration, and response to the mechanical properties of its microenvironment and may help explain behavioral differences between normal and cancerous cells. Using fluorescently labeled peroxisomes as microrheological probes, the interior mechanical properties of normal breast cells were compared to a metastatic breast cell line, MDA-MB-231. To estimate the mechanical properties of cell cytoplasms from the motions of their peroxisomes, it was necessary to reduce the contribution of active cytoskeletal motions to peroxisome motion. This was done by treating the cells with blebbistatin, to inhibit myosin II, or with sodium azide and 2-deoxy-D-glucose, to reduce intracellular ATP. Using either treatment, the peroxisomes exhibited normal diffusion or subdiffusion, and their mean squared displacements (MSDs) showed that the MDA-MB-231 cells were significantly softer than normal cells. For these two cell types, peroxisome MSDs in treated and untreated cells converged at high frequencies, indicating that cytoskeletal structure was not altered by the drug treatment. The MSDs from ATP-depleted cells were analyzed by the generalized Stokes–Einstein relation to estimate the interior viscoelastic modulus G* and its components, the elastic shear modulus G′ and viscous shear modulus G″, at angular frequencies between 0.126 and 628rad/s. These moduli are the material coefficients that enter into stress–strain relations and relaxation times in quantitative mechanical models such as the poroelastic model of the interior regions of cancerous and non-cancerous cells. PMID:25929519

  8. Mechanical properties of the beetle elytron, a biological composite material

    USDA-ARS?s Scientific Manuscript database

    We determined the relationship between composition and mechanical properties of elytral (modified forewing) cuticle of the beetles Tribolium castaneum and Tenebrio molitor. Elytra of both species have similar mechanical properties at comparable stages of maturation (tanning). Shortly after adult ecl...

  9. Mechanical Properties of 23 Species of Eastern Hardwoods.

    Treesearch

    B. A. Bendtsen; R. L. Ethington

    1975-01-01

    Important mechanical properties of clear, straight-grained wood of 23 species are tabulated, along with coefficients of variation. These property estimates can be used to match up species with kind of material needed for a specific job, or to search for substitutes for a presently used species. Some of the species appear, with allowable properties, in two published...

  10. Mechanical properties of reconstituted Australian black coal

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jasinge, D.; Ranjith, P.G.; Choi, S.K.

    2009-07-15

    Coal is usually highly heterogeneous. Great variation in properties can exist among samples obtained even at close proximity within the same seam or within the same core sample. This makes it difficult to establish a correlation between uniaxial compressive strength (UCS) and point load index for coal. To overcome this problem, a method for making reconstituted samples for laboratory tests was developed. Samples were made by compacting particles of crushed coal mixed with cement and water. These samples were allowed to cure for four days. UCS and point load tests were performed to measure the geomechanical properties of the reconstitutedmore » coal. After four days curing, the average UCS was found to be approximately 4 MPa. This technical note outlines some experimental results and correlations that were developed to predict the mechanical properties of the reconstituted black coal samples. By reconstituting the samples from crushed coal, it is hoped that the samples will retain the important mechanical and physicochemical properties of coal, including the swelling, fluid transport, and gas sorption properties of coal. The aim is to be able to produce samples that are homogeneous with properties that are highly reproducible, and the reconstituted coal samples can be used for a number of research areas related to coal, including the long-term safe storage of CO{sub 2} in coal seams.« less

  11. Structure-mechanics property relationship of waste derived biochars.

    PubMed

    Das, Oisik; Sarmah, Ajit K; Bhattacharyya, Debes

    2015-12-15

    The widespread applications of biochar in agriculture and environmental remediation made the scientific community ignore its mechanical properties. Hence, to examine the scope of biochar's structural applications, its mechanical properties have been investigated in this paper through nanoindentation technique. Seven waste derived biochars, made under different pyrolysis conditions and from diverse feedstocks, were studied via nanoindentation, infrared spectroscopy, X-ray crystallography, thermogravimetry, and electron microscopy. Following this, an attempt was made to correlate the biochars' hardness/modulus with reaction conditions and their chemical properties. The pine wood biochar made at 900°C and 60min residence time was found to have the highest hardness and elastic modulus of 4.29 and 25.01GPa, respectively. It was shown that a combination of higher heat treatment (≥500°C) temperature and longer residence time (~60min) increases the values of hardness and modulus. It was further realized that pyrolysis temperature was a more dominant factor than residence time in determining the final mechanical properties of biochar particles. The degree of aromaticity and crystallinity of the biochar were also correlated with higher values of hardness and modulus. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Enhancement of mechanical properties of epoxy/graphene nanocomposite

    NASA Astrophysics Data System (ADS)

    Berhanuddin, N. I. C.; Zaman, I.; Rozlan, S. A. M.; Karim, M. A. A.; Manshoor, B.; Khalid, A.; Chan, S. W.; Meng, Q.

    2017-10-01

    Graphene is a novel class of nanofillers possessing outstanding characteristics including most compatible with most polymers, high absolute strength, high aspect ratio and cost effectiveness. In this study, graphene was used to reinforce epoxy as a matrix, to enhance its mechanical properties. Two types of epoxy composite were developed which are epoxy/graphene nanocomposite and epoxy/modified graphene nanocomposite. The fabrication of graphene was going through thermal expansion and sonication process. Chemical modification was only done for modified graphene where 4,4’-Methylene diphenyl diisocyanate (MDI) is used. The mechanical properties of both nanocomposite, such as Young’s modulus and maximum stress were investigated. Three weight percentage were used for this study which are 0.5 wt%, 1.0 wt% and 1.5 wt%. At 0.5 wt%, modified and unmodified shows the highest value compared to neat epoxy, where the value were 8 GPa, 6 GPa and 0.675 GPa, respectively. For maximum stress, neat epoxy showed the best result compared to both nanocomposite due to the changes of material properties when adding the filler into the matrix. Therefore, both nanocomposite increase the mechanical properties of the epoxy, however modification surface of graphene gives better improvement.

  13. Respiratory system dynamical mechanical properties: modeling in time and frequency domain.

    PubMed

    Carvalho, Alysson Roncally; Zin, Walter Araujo

    2011-06-01

    The mechanical properties of the respiratory system are important determinants of its function and can be severely compromised in disease. The assessment of respiratory system mechanical properties is thus essential in the management of some disorders as well as in the evaluation of respiratory system adaptations in response to an acute or chronic process. Most often, lungs and chest wall are treated as a linear dynamic system that can be expressed with differential equations, allowing determination of the system's parameters, which will reflect the mechanical properties. However, different models that encompass nonlinear characteristics and also multicompartments have been used in several approaches and most specifically in mechanically ventilated patients with acute lung injury. Additionally, the input impedance over a range of frequencies can be assessed with a convenient excitation method allowing the identification of the mechanical characteristics of the central and peripheral airways as well as lung periphery impedance. With the evolution of computational power, the airway pressure and flow can be recorded and stored for hours, and hence continuous monitoring of the respiratory system mechanical properties is already available in some mechanical ventilators. This review aims to describe some of the most frequently used models for the assessment of the respiratory system mechanical properties in both time and frequency domain.

  14. Quantifying dynamic mechanical properties of human placenta tissue using optimization techniques with specimen-specific finite-element models.

    PubMed

    Hu, Jingwen; Klinich, Kathleen D; Miller, Carl S; Nazmi, Giseli; Pearlman, Mark D; Schneider, Lawrence W; Rupp, Jonathan D

    2009-11-13

    Motor-vehicle crashes are the leading cause of fetal deaths resulting from maternal trauma in the United States, and placental abruption is the most common cause of these deaths. To minimize this injury, new assessment tools, such as crash-test dummies and computational models of pregnant women, are needed to evaluate vehicle restraint systems with respect to reducing the risk of placental abruption. Developing these models requires accurate material properties for tissues in the pregnant abdomen under dynamic loading conditions that can occur in crashes. A method has been developed for determining dynamic material properties of human soft tissues that combines results from uniaxial tensile tests, specimen-specific finite-element models based on laser scans that accurately capture non-uniform tissue-specimen geometry, and optimization techniques. The current study applies this method to characterizing material properties of placental tissue. For 21 placenta specimens tested at a strain rate of 12/s, the mean failure strain is 0.472+/-0.097 and the mean failure stress is 34.80+/-12.62 kPa. A first-order Ogden material model with ground-state shear modulus (mu) of 23.97+/-5.52 kPa and exponent (alpha(1)) of 3.66+/-1.90 best fits the test results. The new method provides a nearly 40% error reduction (p<0.001) compared to traditional curve-fitting methods by considering detailed specimen geometry, loading conditions, and dynamic effects from high-speed loading. The proposed method can be applied to determine mechanical properties of other soft biological tissues.

  15. Bombyx mori silk: From mechanical properties to functionalities

    NASA Astrophysics Data System (ADS)

    Koh, Leng Duei

    Bombyx mori silkworms are the main producer of silk worldwide. It has been used as high-end textile fibers and as surgical sutures, and is being further developed for various emerging biomedical applications including drug delivery, tissue engineering, sensing, and imaging. The silk fibroin features a hierarchical architecture consisting of beta-sheet crystallites embedded in a less ordered amorphous matrix, which accounts for its unique combination of lustre appearance, soft-to-touch texture, and impressive mechanical properties. Notably, many applications of silk take advantage of its impressive mechanical properties, which by nature surpass many natural and synthetic materials. Interestingly, both the silkworm silk and spider dragline silk share similar hierarchical architecture but possess great disparity in mechanical properties. Inspired by spider dragline silk with much superior strength and toughness, there is an ever growing interest to enhance the mechanical properties of Bombyx mori silk. Here, we design a green and facile feeding method to modulate the structures of silk fibroin at the nanoscale using citric acid (CA), and achieved greatly enhanced mechanical properties. The silk obtained (i.e., CA silk) emerges to be the intrinsically toughest silkworm silk, with mechanical properties that exceed those of the previously reported natural and enhanced silkworm silk, and compare well with those of naturally produced spider silk (including those from spiders Araneus diadematus, Nephila clavipes, etc.).The underlying interactions of CA with fibroin structures are revealed by both advanced characterizations and simulations. It is found that CA interacts with fibroin, resulted in remarkably shorter crystallites, and thus giving the outstanding strength and toughness of the CA silk. The greatly enhanced mechanical properties are expected to lead to better functionalities and wider applications of the Bombyx mori silkworm silk. Silkworms usually produce white

  16. Tissue-Level Mechanical Properties of Bone Contributing to Fracture Risk.

    PubMed

    Nyman, Jeffry S; Granke, Mathilde; Singleton, Robert C; Pharr, George M

    2016-08-01

    Tissue-level mechanical properties characterize mechanical behavior independently of microscopic porosity. Specifically, quasi-static nanoindentation provides measurements of modulus (stiffness) and hardness (resistance to yielding) of tissue at the length scale of the lamella, while dynamic nanoindentation assesses time-dependent behavior in the form of storage modulus (stiffness), loss modulus (dampening), and loss factor (ratio of the two). While these properties are useful in establishing how a gene, signaling pathway, or disease of interest affects bone tissue, they generally do not vary with aging after skeletal maturation or with osteoporosis. Heterogeneity in tissue-level mechanical properties or in compositional properties may contribute to fracture risk, but a consensus on whether the contribution is negative or positive has not emerged. In vivo indentation of bone tissue is now possible, and the mechanical resistance to microindentation has the potential for improving fracture risk assessment, though determinants are currently unknown.

  17. Tissue-level Mechanical Properties of Bone Contributing to Fracture Risk

    PubMed Central

    Nyman, Jeffry S.; Granke, Mathilde; Singleton, Robert C.; Pharr, George M.

    2016-01-01

    Tissue-level mechanical properties characterize mechanical behavior independently of microscopic porosity. Specifically, quasi-static nanoindentation provides measurements of modulus (stiffness) and hardness (resistance to yielding) of tissue at the length scale of the lamella, while dynamic nanoindentation assesses time-dependent behavior in the form of storage modulus (stiffness), loss modulus (dampening), and loss factor (ratio of the two). While these properties are useful in establishing how a gene, signaling pathway, or disease of interest affects bone tissue, they generally do not vary with aging after skeletal maturation or with osteoporosis. Heterogeneity in tissue-level mechanical properties or in compositional properties may contribute to fracture risk, but a consensus on whether the contribution is negative or positive has not emerged. In vivo indentation of bone tissue is now possible, and the mechanical resistance to microindentation has the potential for improving fracture risk assessment, though determinants are currently unknown. PMID:27263108

  18. Mechanical Properties of Materials with Nanometer Scale Microstructures

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    William D. Nix

    2004-10-31

    We have been engaged in research on the mechanical properties of materials with nanometer-scale microstructural dimensions. Our attention has been focused on studying the mechanical properties of thin films and interfaces and very small volumes of material. Because the dimensions of thin film samples are small (typically 1 mm in thickness, or less), specialized mechanical testing techniques based on nanoindentation, microbeam bending and dynamic vibration of micromachined structures have been developed and used. Here we report briefly on some of the results we have obtained over the past three years. We also give a summary of all of the dissertations,more » talks and publications completed on this grant during the past 15 years.« less

  19. The impact of long term freezing on the mechanical properties of porcine aortic tissue.

    PubMed

    O'Leary, Siobhan A; Doyle, Barry J; McGloughlin, Tim M

    2014-09-01

    Preservation of the native artery׳s functionality can be important in both clinical and experimental applications. Although, simple cryopreservation techniques offer an attractive solution to this problem, the extent to which freezing affects the tissue׳s properties is widely debated. Earlier assessments of the mechanical properties post-freezing have been limited by one or more of the following: small sample numbers, uncontrolled inter-specimen/animal variability, failure to account for the impact of potential errors in thickness measurements, short storage times and uniaxial test methods. Biaxial mechanical tests were performed on porcine aortic samples (n=89) extracted from superior, middle and inferior regions of five aortas, stored in isotonic saline at -20°C for 1 day, 1 week, 1, 6 and 12 months, thawed and retested. The sample׳s weight and thickness were also measured pre and post-freezing. A total of 178 tests were performed and elastic modulus was assessed by calculating the slope of the Cauchy stress-stretch curve at the low and high stretch regions in both the circumferential (θ) and longitudinal (L) directions. The weight of the samples increased post-freezing. However, in general, no significant difference was found between the elastic modulus of porcine aortic tissue before and after freezing at -20°C and was unaffected by storage time. Although more accurate measuring instruments are warranted to confirm this finding, minor changes to the elastic modulus as a result of freezing were negatively correlated with regional variances i.e. changes in the elastic modulus decreased from the superior to the inferior region. These results indicate that for applications which require preservation of the gross mechanical properties, storing the tissue at -20°C in isotonic saline, for an extended period of time, is acceptable. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. DNA origami compliant nanostructures with tunable mechanical properties.

    PubMed

    Zhou, Lifeng; Marras, Alexander E; Su, Hai-Jun; Castro, Carlos E

    2014-01-28

    DNA origami enables fabrication of precise nanostructures by programming the self-assembly of DNA. While this approach has been used to make a variety of complex 2D and 3D objects, the mechanical functionality of these structures is limited due to their rigid nature. We explore the fabrication of deformable, or compliant, objects to establish a framework for mechanically functional nanostructures. This compliant design approach is used in macroscopic engineering to make devices including sensors, actuators, and robots. We build compliant nanostructures by utilizing the entropic elasticity of single-stranded DNA (ssDNA) to locally bend bundles of double-stranded DNA into bent geometries whose curvature and mechanical properties can be tuned by controlling the length of ssDNA strands. We demonstrate an ability to achieve a wide range of geometries by adjusting a few strands in the nanostructure design. We further developed a mechanical model to predict both geometry and mechanical properties of our compliant nanostructures that agrees well with experiments. Our results provide a basis for the design of mechanically functional DNA origami devices and materials.

  1. Characterization of three-dimensional anisotropic heart valve tissue mechanical properties using inverse finite element analysis.

    PubMed

    Abbasi, Mostafa; Barakat, Mohammed S; Vahidkhah, Koohyar; Azadani, Ali N

    2016-09-01

    Computational modeling has an important role in design and assessment of medical devices. In computational simulations, considering accurate constitutive models is of the utmost importance to capture mechanical response of soft tissue and biomedical materials under physiological loading conditions. Lack of comprehensive three-dimensional constitutive models for soft tissue limits the effectiveness of computational modeling in research and development of medical devices. The aim of this study was to use inverse finite element (FE) analysis to determine three-dimensional mechanical properties of bovine pericardial leaflets of a surgical bioprosthesis under dynamic loading condition. Using inverse parameter estimation, 3D anisotropic Fung model parameters were estimated for the leaflets. The FE simulations were validated using experimental in-vitro measurements, and the impact of different constitutive material models was investigated on leaflet stress distribution. The results of this study showed that the anisotropic Fung model accurately simulated the leaflet deformation and coaptation during valve opening and closing. During systole, the peak stress reached to 3.17MPa at the leaflet boundary while during diastole high stress regions were primarily observed in the commissures with the peak stress of 1.17MPa. In addition, the Rayleigh damping coefficient that was introduced to FE simulations to simulate viscous damping effects of surrounding fluid was determined. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Characterizing the macro and micro mechanical properties of scaffolds for rotator cuff repair.

    PubMed

    Smith, Richard D J; Zargar, Nasim; Brown, Cameron P; Nagra, Navraj S; Dakin, Stephanie G; Snelling, Sarah J B; Hakimi, Osnat; Carr, Andrew

    2017-11-01

    Retearing after rotator cuff surgery is a major clinical problem. Numerous scaffolds are being used to try to reduce retear rates. However, few have demonstrated clinical efficacy. We hypothesize that this lack of efficacy is due to insufficient mechanical properties. Therefore, we compared the macro and nano/micro mechanical properties of 7 commercially available scaffolds to those of the human supraspinatus tendons, whose function they seek to restore. The clinically approved scaffolds tested were X-Repair, LARS ligament, Poly-Tape, BioFiber, GraftJacket, Permacol, and Conexa. Fresh frozen cadaveric human supraspinatus tendon samples were used. Macro mechanical properties were determined through tensile testing and rheometry. Scanning probe microscopy and scanning electron microscopy were performed to assess properties of materials at the nano/microscale (morphology, Young modulus, loss tangent). None of the scaffolds tested adequately approximated both the macro and micro mechanical properties of human supraspinatus tendon. Macroscale mechanical properties were insufficient to restore load-bearing function. The best-performing scaffolds on the macroscale (X-Repair, LARS ligament) had poor nano/microscale properties. Scaffolds approximating tendon properties on the nano/microscale (BioFiber, biologic scaffolds) had poor macroscale properties. Existing scaffolds failed to adequately approximate the mechanical properties of human supraspinatus tendons. Combining the macroscopic mechanical properties of a synthetic scaffold with the micro mechanical properties of biologic scaffold could better achieve this goal. Future work should focus on advancing techniques to create new scaffolds with more desirable mechanical properties. This may help improve outcomes for rotator cuff surgery patients. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  3. Electro-optical and physic-mechanical properties of colored alicyclic polyimide

    NASA Astrophysics Data System (ADS)

    Kravtsova, V.; Umerzakova, M.; Korobova, N.; Timoshenkov, S.; Timoshenkov, V.; Orlov, S.; Iskakov, R.; Prikhodko, O.

    2016-09-01

    Main optical, thermal and mechanical properties of new compositions based on alicyclic polyimide and active bright red 6C synthetic dye have been studied. It was shown that the transmission ratio of the new material in the region of 400-900 nm and 2.0 wt.% dye concentration was around 60-70%. Thermal, mechanical and electrical properties of new colored compositions were comparable with the properties of original polyimide.

  4. Simple display system of mechanical properties of cells and their dispersion.

    PubMed

    Shimizu, Yuji; Kihara, Takanori; Haghparast, Seyed Mohammad Ali; Yuba, Shunsuke; Miyake, Jun

    2012-01-01

    The mechanical properties of cells are unique indicators of their states and functions. Though, it is difficult to recognize the degrees of mechanical properties, due to small size of the cell and broad distribution of the mechanical properties. Here, we developed a simple virtual reality system for presenting the mechanical properties of cells and their dispersion using a haptic device and a PC. This system simulates atomic force microscopy (AFM) nanoindentation experiments for floating cells in virtual environments. An operator can virtually position the AFM spherical probe over a round cell with the haptic handle on the PC monitor and feel the force interaction. The Young's modulus of mesenchymal stem cells and HEK293 cells in the floating state was measured by AFM. The distribution of the Young's modulus of these cells was broad, and the distribution complied with a log-normal pattern. To represent the mechanical properties together with the cell variance, we used log-normal distribution-dependent random number determined by the mode and variance values of the Young's modulus of these cells. The represented Young's modulus was determined for each touching event of the probe surface and the cell object, and the haptic device-generating force was calculated using a Hertz model corresponding to the indentation depth and the fixed Young's modulus value. Using this system, we can feel the mechanical properties and their dispersion in each cell type in real time. This system will help us not only recognize the degrees of mechanical properties of diverse cells but also share them with others.

  5. Simple Display System of Mechanical Properties of Cells and Their Dispersion

    PubMed Central

    Shimizu, Yuji; Kihara, Takanori; Haghparast, Seyed Mohammad Ali; Yuba, Shunsuke; Miyake, Jun

    2012-01-01

    The mechanical properties of cells are unique indicators of their states and functions. Though, it is difficult to recognize the degrees of mechanical properties, due to small size of the cell and broad distribution of the mechanical properties. Here, we developed a simple virtual reality system for presenting the mechanical properties of cells and their dispersion using a haptic device and a PC. This system simulates atomic force microscopy (AFM) nanoindentation experiments for floating cells in virtual environments. An operator can virtually position the AFM spherical probe over a round cell with the haptic handle on the PC monitor and feel the force interaction. The Young's modulus of mesenchymal stem cells and HEK293 cells in the floating state was measured by AFM. The distribution of the Young's modulus of these cells was broad, and the distribution complied with a log-normal pattern. To represent the mechanical properties together with the cell variance, we used log-normal distribution-dependent random number determined by the mode and variance values of the Young's modulus of these cells. The represented Young's modulus was determined for each touching event of the probe surface and the cell object, and the haptic device-generating force was calculated using a Hertz model corresponding to the indentation depth and the fixed Young's modulus value. Using this system, we can feel the mechanical properties and their dispersion in each cell type in real time. This system will help us not only recognize the degrees of mechanical properties of diverse cells but also share them with others. PMID:22479595

  6. Lightweight Concrete : Mechanical Properties : TechBrief

    DOT National Transportation Integrated Search

    2013-06-01

    There is a limited amount of test data on the mechanical properties of high-strength lightweight concrete (LWC) with a concrete unit weight (wc) between that of traditional LWC and normal weight concrete (NWC). Concrete with a wc in this range is als...

  7. Rhenium Mechanical Properties and Joining Technology

    NASA Technical Reports Server (NTRS)

    Reed, Brian D.; Biaglow, James A.

    1996-01-01

    Iridium-coated rhenium (Ir/Re) provides thermal margin for high performance and long life radiation cooled rockets. Two issues that have arisen in the development of flight Ir/Re engines are the sparsity of rhenium (Re) mechanical property data (particularly at high temperatures) required for engineering design, and the inability to directly electron beam weld Re chambers to C103 nozzle skirts. To address these issues, a Re mechanical property database is being established and techniques for creating Re/C103 transition joints are being investigated. This paper discusses the tensile testing results of powder metallurgy Re samples at temperatures from 1370 to 2090 C. Also discussed is the evaluation of Re/C103 transition pieces joined by both, explosive and diffusion bonding. Finally, the evaluation of full size Re transition pieces, joined by inertia welding, as well as explosive and diffusion bonding, is detailed.

  8. Selected physical and mechanical properties of moso bamboo (Phyllostachys pubescens)

    Treesearch

    H.Q. Yu; Z.H. Jiang; C.Y. Hse; T.F. Shupe

    2008-01-01

    Selected physical and mechanical properties of moso bamboo (Phyllostachys pubescens). Selected physical and mechanical properties of 4?6 year old moso bamboo (Phyllostachys pubescens) grown in Zhejiang, China were investigated at different vertical and horizontal positions. Two way analysis of variance and Tukey?s mean comparison...

  9. Multiscale Modeling of Carbon/Phenolic Composite Thermal Protection Materials: Atomistic to Effective Properties

    NASA Technical Reports Server (NTRS)

    Arnold, Steven M.; Murthy, Pappu L.; Bednarcyk, Brett A.; Lawson, John W.; Monk, Joshua D.; Bauschlicher, Charles W., Jr.

    2016-01-01

    Next generation ablative thermal protection systems are expected to consist of 3D woven composite architectures. It is well known that composites can be tailored to achieve desired mechanical and thermal properties in various directions and thus can be made fit-for-purpose if the proper combination of constituent materials and microstructures can be realized. In the present work, the first, multiscale, atomistically-informed, computational analysis of mechanical and thermal properties of a present day - Carbon/Phenolic composite Thermal Protection System (TPS) material is conducted. Model results are compared to measured in-plane and out-of-plane mechanical and thermal properties to validate the computational approach. Results indicate that given sufficient microstructural fidelity, along with lowerscale, constituent properties derived from molecular dynamics simulations, accurate composite level (effective) thermo-elastic properties can be obtained. This suggests that next generation TPS properties can be accurately estimated via atomistically informed multiscale analysis.

  10. Mechanical properties of canine osteosarcoma-affected antebrachia.

    PubMed

    Steffey, Michele A; Garcia, Tanya C; Daniel, Leticia; Zwingenberger, Allison L; Stover, Susan M

    2017-05-01

    To determine the influence of neoplasia on the biomechanical properties of canine antebrachia. Ex vivo biomechanical study. Osteosarcoma (OSA)-affected canine antebrachia (n = 12) and unaffected canine antebrachia (n = 9). Antebrachia were compressed in axial loading until failure. A load-deformation curve was used to acquire the structural mechanical properties of neoplastic and unaffected specimens. Structural properties and properties normalized by body weight (BW) and radius length were compared using analysis of variance (ANOVA). Modes of failure were compared descriptively. Neoplastic antebrachia fractured at, or adjacent to, the OSA in the distal radial diaphysis. Unaffected antebrachia failed via mid-diaphyseal radial fractures with a transverse cranial component and an oblique caudal component. Structural mechanical properties were more variable in neoplastic antebrachia than unaffected antebrachia, which was partially attributable to differences in bone geometry related to dog size. When normalized by dog BW and radial length, strength, stiffness, and energy to yield and failure, were lower in neoplastic antebrachia than in unaffected antebrachia. OSA of the distal radial metaphysis in dogs presented for limb amputation markedly compromises the structural integrity of affected antebrachia. However, biomechanical properties of affected bones was sufficient for weight-bearing, as none of the neoplastic antebrachia fractured before amputation. The behavior of tumor invaded bone under cyclic loading warrants further investigations to evaluate the viability of in situ therapies for bone tumors in dogs. © 2017 The American College of Veterinary Surgeons.

  11. Accurate dipole moment curve and non-adiabatic effects on the high resolution spectroscopic properties of the LiH molecule

    NASA Astrophysics Data System (ADS)

    Diniz, Leonardo G.; Kirnosov, Nikita; Alijah, Alexander; Mohallem, José R.; Adamowicz, Ludwik

    2016-04-01

    A very accurate dipole moment curve (DMC) for the ground X1Σ+ electronic state of the 7LiH molecule is reported. It is calculated with the use of all-particle explicitly correlated Gaussian functions with shifted centers. The DMC - the most accurate to our knowledge - and the corresponding highly accurate potential energy curve are used to calculate the transition energies, the transition dipole moments, and the Einstein coefficients for the rovibrational transitions with ΔJ = - 1 and Δv ⩽ 5 . The importance of the non-adiabatic effects in determining these properties is evaluated using the model of a vibrational R-dependent effective reduced mass in the rovibrational calculations introduced earlier (Diniz et al., 2015). The results of the present calculations are used to assess the quality of the two complete linelists of 7LiH available in the literature.

  12. Simulation of the Press Hardening Process and Prediction of the Final Mechanical Material Properties

    NASA Astrophysics Data System (ADS)

    Hochholdinger, Bernd; Hora, Pavel; Grass, Hannes; Lipp, Arnulf

    2011-08-01

    Press hardening is a well-established production process in the automotive industry today. The actual trend of this process technology points towards the manufacturing of parts with tailored properties. Since the knowledge of the mechanical properties of a structural part after forming and quenching is essential for the evaluation of for example the crash performance, an accurate as possible virtual assessment of the production process is more than ever necessary. In order to achieve this, the definition of reliable input parameters and boundary conditions for the thermo-mechanically coupled simulation of the process steps is required. One of the most important input parameters, especially regarding the final properties of the quenched material, is the contact heat transfer coefficient (IHTC). The CHTC depends on the effective pressure or the gap distance between part and tool. The CHTC at different contact pressures and gap distances is determined through inverse parameter identification. Furthermore a simulation strategy for the subsequent steps of the press hardening process as well as adequate modeling approaches for part and tools are discussed. For the prediction of the yield curves of the material after press hardening a phenomenological model is presented. This model requires the knowledge of the microstructure within the part. By post processing the nodal temperature history with a CCT diagram the quantitative distribution of the phase fractions martensite, bainite, ferrite and pearlite after press hardening is determined. The model itself is based on a Hockett-Sherby approach with the Hockett-Sherby parameters being defined in function of the phase fractions and a characteristic cooling rate.

  13. Correlation between the mechanical and histological properties of liver tissue.

    PubMed

    Yarpuzlu, Berkay; Ayyildiz, Mehmet; Tok, Olgu Enis; Aktas, Ranan Gulhan; Basdogan, Cagatay

    2014-01-01

    In order to gain further insight into the mechanisms of tissue damage during the progression of liver diseases as well as the liver preservation for transplantation, an improved understanding of the relation between the mechanical and histological properties of liver is necessary. We suggest that this relation can only be established truly if the changes in the states of those properties are investigated dynamically as a function of post mortem time. In this regard, we first perform mechanical characterization experiments on three bovine livers to investigate the changes in gross mechanical properties (stiffness, viscosity, and fracture toughness) for the preservation periods of 5, 11, 17, 29, 41 and 53h after harvesting. Then, the histological examination is performed on the samples taken from the same livers to investigate the changes in apoptotic cell count, collagen accumulation, sinusoidal dilatation, and glycogen deposition as a function of the same preservation periods. Finally, the correlation between the mechanical and histological properties is investigated via the Spearman's Rank-Order Correlation method. The results of our study show that stiffness, viscosity, and fracture toughness of bovine liver increase as the preservation period is increased. These macroscopic changes are very strongly correlated with the increase in collagen accumulation and decrease in deposited glycogen level at the microscopic level. Also, we observe that the largest changes in mechanical and histological properties occur after the first 11-17h of preservation. © 2013 Elsevier Ltd. All rights reserved.

  14. Correlation of microstructure and thermo-mechanical properties of a novel hydrogen transport membrane

    NASA Astrophysics Data System (ADS)

    Zhang, Yongjun

    A key part of the FutureGen concept is to support the production of hydrogen to fuel a "hydrogen economy," with the use of clean burning hydrogen in power-producing fuel cells, as well as for use as a transportation fuel. One of the key technical barriers to FutureGen deployment is reliable and efficient hydrogen separation technology. Most Hydrogen Transport Membrane (HTM) research currently focuses on separation technology and hydrogen flux characterization. No significant work has been performed on thermo-mechanical properties of HTMs. The objective of the thesis is to understand the structure-property correlation of HTM and to characterize (1) thermo mechanical properties under different reducing environments and thermal cycles (thermal shock), and (2) evaluate the stability of the novel HTM material. A novel HTM cermet bulk sample was characterized for its physical and mechanical properties at both room temperature and at elevated temperature up to 1000°C. Micro-structural properties and residual stresses were evaluated in order to understand the changing mechanism of the microstructure and its effects on the mechanical properties of materials. A correlation of the microstructural and thermo mechanical properties of the HTM system was established for both HTM and the substrate material. Mechanical properties of both selected structural ceramics and the novel HTM cermet bulk sample are affected mainly by porosity and microstructural features, such as grain size and pore size-distribution. The Young's Modulus (E-value) is positively correlated to the flexural strength for materials with similar crystallographic structure. However, for different crystallographic materials, physical properties are independent of mechanical properties. Microstructural properties, particularly, grain size and crystallographic structure, and thermodynamic properties are the main factors affecting the mechanical properties at both room and high temperatures. The HTM cermet behaves

  15. ZM-21 magnesium alloy corrosion properties and cryogenic to elevated temperature mechanical properties

    NASA Technical Reports Server (NTRS)

    Montana, J. W.; Nelson, E. E.

    1972-01-01

    The mechanical properties of bare ZM-21 magnesium alloy flat tensile specimens were determined for test temperatures of +400 F, +300 F, +200 F, +80 F, 0 F, -100 F, -200 F, and -320 F. The ultimate tensile and yield strengths of the material increased with decreasing temperature with a corresponding reduction in elongation values. Stress corrosion tests performed under: (1) MSFC atmospheric conditions; (2) 95% relative humidity; and (3) submerged in 100 ppm chloride solution for 8 weeks indicated that the alloy is not susceptible to stress corrosion. The corrosion tests indicated that the material is susceptible to attack by crevice corrosion in high humidity and chemical type attack by chloride solution. Atmospheric conditions at MSFC did not produce any adverse effects on the material, probably due to the rapid formation of a protective oxide coating. In both the mechanical properties and the stress corrosion evaluations the test specimens which were cut transverse to the rolling direction had superior properties when compared to the longitudinal properties.

  16. Chitosan fibers with improved biological and mechanical properties for tissue engineering applications.

    PubMed

    Albanna, Mohammad Z; Bou-Akl, Therese H; Blowytsky, Oksana; Walters, Henry L; Matthew, Howard W T

    2013-04-01

    The low mechanical properties of hydrogel materials such as chitosan hinder their broad utility for tissue engineering applications. Previous research efforts improved the mechanical properties of chitosan fiber through chemical and physical modifications; however, unfavorable toxicity effects on cells were reported. In this paper, we report the preparation of chitosan fibers with improved mechanical and biocompatibility properties. The structure-property relationships of extruded chitosan fibers were explored by varying acetic acid (AA) concentration, ammonia concentration, annealing temperature and degree of heparin crosslinking. Results showed that optimizing AA concentration to 2vol% improved fiber strength and stiffness by 2-fold. Extruding chitosan solution into 25wt% of ammonia solution reduced fiber diameters and improved fiber strength by 2-fold and stiffness by 3-fold, due to an increase in crystallinity as confirmed by XRD. Fiber annealing further reduced fiber diameter and improved fiber strength and stiffness as temperature increased. Chitosan fibers crosslinked with heparin had increased diameter but lower strength and stiffness properties and higher breaking strain values. When individual parameters were combined, further improvement in fiber mechanical properties was achieved. All mechanically improved fibers and heparin crosslinked fibers promoted valvular interstitial cells (VIC) attachment and growth over 10 day cultures. Our results demonstrate the ability to substantially improve the mechanical properties of chitosan fibers without adversely affecting their biological properties. The investigated treatments offer numerous advantages over previous physical/chemical modifications and thus are expected to expand the utility of chitosan fibers with tunable mechanical properties in various tissue engineering applications. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. Long term mechanical properties of alkali activated slag

    NASA Astrophysics Data System (ADS)

    Zhu, J.; Zheng, W. Z.; Xu, Z. Z.; Leng, Y. F.; Qin, C. Z.

    2018-01-01

    This article reports a study on the microstructural and long-term mechanical properties of the alkali activated slag up to 180 days, and cement paste is studied as the comparison. The mechanical properties including compressive strength, flexural strength, axis tensile strength and splitting tensile strength are analyzed. The results showed that the alkali activated slag had higher compressive and tensile strength, Slag is activated by potassium silicate (K2SiO3) and sodium hydroxide (NaOH) solutions for attaining silicate modulus of 1 using 12 potassium silicate and 5.35% sodium hydroxide. The volume dosage of water is 35% and 42%. The results indicate that alkali activated slag is a kind of rapid hardening and early strength cementitious material with excellent long-term mechanical properties. Single row of holes block compressive strength, single-hole block compressive strength and standard solid brick compressive strength basically meet engineering requirements. The microstructures of alkali activated slag are studied by X-ray diffraction (XRD). The hydration products of alkali-activated slag are assured as hydrated calcium silicate and hydrated calcium aluminate.

  18. Wood plastic composites from agro-waste materials: Analysis of mechanical properties.

    PubMed

    Nourbakhsh, Amir; Ashori, Alireza

    2010-04-01

    This article presents the application of agro-waste materials (i.e., corn stalk, reed stalk, and oilseed stalk) in order to evaluate and compare their suitability as reinforcement for thermoplastics as an alternative to wood fibers. The effects of fiber loading and CaCO(3) content on the mechanical properties were also studied. Overall trend shows that with addition of agro-waste materials, tensile and flexural properties of the composites are significantly enhanced. Oilseed fibers showed superior mechanical properties due to their high aspect ratio and chemical characteristics. The order of increment in the mechanical properties of the composites is oilseed stalk >corn stalk>reed stalk at all fiber loadings. The tensile and flexural properties of the composite significantly decreased with increasing CaCO(3) content, due to the reduction of interface bond between the fiber and matrix. It can be concluded from this study that the used agro-waste materials are attractive reinforcements from the standpoint of their mechanical properties. Copyright 2009 Elsevier Ltd. All rights reserved.

  19. Papermaking properties of aspen ultrahigh-yield mechanical pulps

    Treesearch

    J. N. McGovern; T. H. Wegner

    1991-01-01

    Eleven types of aspen ultra-high-yield (90% and above) mechanical pubs were evaluated for their chemical compositions (including sulfur), handsheet strength, and optical properties, fiber length indices, and fiberizing energies. The pulping processes were stone groundwood, pressurized stone groundwood, refiner mechanical, thermomechanical, chemimechanical (alkaline...

  20. Effects of heat treatment on mechanical properties of h13 steel

    NASA Astrophysics Data System (ADS)

    Guanghua, Yan; Xinmin, Huang; Yanqing, Wang; Xingguo, Qin; Ming, Yang; Zuoming, Chu; Kang, Jin

    2010-12-01

    Heat treatment on the mechanical properties of H13 hot working die steel for die casting is discussed. The H13 steel for die casting was treated by different temperatures of vacuum quenching, tempering, and secondary tempering to investigate its mechanical properties. Strength, plasticity, hardness, and impact toughness of the H13 hot working die steel for die casting were measured. Microstructure, grain size, and carbide particle size after heat treatment have a great impact on the mechanical properties of H13 hot working die steel for die casting. The microstructure of the H13 was analyzed by scanning electron microscopy (SEM) and by a metallographic microscope. It is found that H13 exhibits excellent mechanical properties after vacuum quenching at 1050°C and twice tempering at 600°C.

  1. Mechanical properties of sugar beet root during storage

    NASA Astrophysics Data System (ADS)

    Nedomová, Šárka; Kumbár, Vojtěch; Pytel, Roman; Buchar, Jaroslav

    2017-10-01

    This paper is an investigation via two experimental methods, of the textural properties of sugar beet roots during the storage period. In the work, sugar beet roots mechanical properties were evaluated during the post-harvest period - 1, 8, 22, 43, and 71 days after crop. Both experimental methods, i.e. compression test and puncture test, suggest that the failure strength of the sugar beet root increases with the storage time. The parameters obtained using the puncture test, are more sensitive to the storage duration than those obtained by way of the compression test. We also found that such mechanical properties served as a reliable tool for monitoring the progress of sugar beet roots storage. The described methods could also be used to highlight important information on sugar beet evolution during storage.

  2. Mechanical property studies of human gallstones.

    PubMed

    Stranne, S K; Cocks, F H; Gettliffe, R

    1990-08-01

    The recent development of gallstone fragmentation methods has increased the significance of the study of the mechanical properties of human gallstones. In the present work, fracture strength data and microhardness values of gallstones of various chemical compositions are presented as tested in both dry and simulated bile environments. Generally, both gallstone hardness and fracture strength values were significantly less than kidney stone values found in previous studies. However, a single calcium carbonate stone was found to have an outer shell hardness exceeding those values found for kidney stones. Diametral compression measurements in simulated bile conclusively demonstrated low gallstone fracture strength as well as brittle fracture in the stones tested. Based on the results of this study, one may conclude that the wide range of gallstone microhardnesses found may explain the reported difficulties previous investigators have experienced using various fragmentation techniques on specific gallstones. Moreover, gallstone mechanical properties may be relatively sensitive to bile-environment composition.

  3. Mechanical properties of hydrogenated bilayer graphene

    NASA Astrophysics Data System (ADS)

    Andrew, R. C.; Mapasha, R. E.; Chetty, N.

    2013-06-01

    Using first principle methods, we study the mechanical properties of monolayer and bilayer graphene with 50% and 100% coverage of hydrogen. We employ the vdW-DF, vdW-DF-C09x, and vdW-DF2-C09x van der Waals functionals for the exchange correlation interactions that give significantly improved interlayer spacings and energies. We also use the PBE form for the generalized gradient corrected exchange correlation functional for comparison. We present a consistent theoretical framework for the in-plane layer modulus and the out-of-plane interlayer modulus and we calculate, for the first time, these properties for these systems. This gives a measure of the change of the strength properties when monolayer and bilayer graphene are hydrogenated. Moreover, comparing the relative performance of these functionals in describing hydrogenated bilayered graphenes, we also benchmark these functionals in how they calculate the properties of graphite.

  4. Accurate electron gun-positioning mechanism for electron beam-mapping of large cross-section magnetic surfaces

    NASA Astrophysics Data System (ADS)

    Anderson, F. S. B.; Middleton, F.; Colchin, R. J.; Million, D.

    1989-04-01

    A method of accurately supporting and positioning an electron source inside a large cross-sectional area magnetic field which provides very low electron beam occlusion is reported. The application of electrical discharge machining to the fabrication of a 1-m truss support structure has provided an extremely long, rigid and mechanically strong electron gun support. Reproducible electron gun positioning to within 1 mm has been achieved at any location within a 1×0.6-m2 area. The extremely thin sections of the support truss (≤1.5 mm) have kept the electron beam occlusion to less than 3 mm. The support and drive mechanism have been designed and fabricated at the University of Wisconsin for application to the mapping of the magnetic surface structure of the Advanced Toroidal Facility torsatron1 at the Oak Ridge National Laboratory.

  5. Mechanical properties and strengthening mechanism of epoxy resin reinforced with nano-SiO2 particles and multi-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Xiao, Chufan; Tan, Yefa; Yang, Xupu; Xu, Ting; Wang, Lulu; Qi, Zehao

    2018-03-01

    Nano-SiO2 particles and MWCNTs were used to reinforce the EPs. The mechanical properties of the composites and the strengthening mechanisms of nano-SiO2 and MWCNTs on the mechanical properties of epoxy composites were studied. The results show that the mechanical properties of the reinforced epoxy composites are greatly improved. Especially, nano-SiO2/MWCNTs/EP composites exhibit the most excellent mechanical properties. The synergistic strengthening mechanisms of nano-SiO2 and MWCNTs on the EP are the micro plastic deformation effect, micro-cracks and their divarication effect, and the pull-out effect of MWCNTs in EP matrix, which can reduce the extent of stress concentration and absorb more energy.

  6. Predicting Silk Fiber Mechanical Properties through Multiscale Simulation and Protein Design.

    PubMed

    Rim, Nae-Gyune; Roberts, Erin G; Ebrahimi, Davoud; Dinjaski, Nina; Jacobsen, Matthew M; Martín-Moldes, Zaira; Buehler, Markus J; Kaplan, David L; Wong, Joyce Y

    2017-08-14

    Silk is a promising material for biomedical applications, and much research is focused on how application-specific, mechanical properties of silk can be designed synthetically through proper amino acid sequences and processing parameters. This protocol describes an iterative process between research disciplines that combines simulation, genetic synthesis, and fiber analysis to better design silk fibers with specific mechanical properties. Computational methods are used to assess the protein polymer structure as it forms an interconnected fiber network through shearing and how this process affects fiber mechanical properties. Model outcomes are validated experimentally with the genetic design of protein polymers that match the simulation structures, fiber fabrication from these polymers, and mechanical testing of these fibers. Through iterative feedback between computation, genetic synthesis, and fiber mechanical testing, this protocol will enable a priori prediction capability of recombinant material mechanical properties via insights from the resulting molecular architecture of the fiber network based entirely on the initial protein monomer composition. This style of protocol may be applied to other fields where a research team seeks to design a biomaterial with biomedical application-specific properties. This protocol highlights when and how the three research groups (simulation, synthesis, and engineering) should be interacting to arrive at the most effective method for predictive design of their material.

  7. Mechanical Properties of Additively Manufactured Thick Honeycombs.

    PubMed

    Hedayati, Reza; Sadighi, Mojtaba; Mohammadi Aghdam, Mohammad; Zadpoor, Amir Abbas

    2016-07-23

    Honeycombs resemble the structure of a number of natural and biological materials such as cancellous bone, wood, and cork. Thick honeycomb could be also used for energy absorption applications. Moreover, studying the mechanical behavior of honeycombs under in-plane loading could help understanding the mechanical behavior of more complex 3D tessellated structures such as porous biomaterials. In this paper, we study the mechanical behavior of thick honeycombs made using additive manufacturing techniques that allow for fabrication of honeycombs with arbitrary and precisely controlled thickness. Thick honeycombs with different wall thicknesses were produced from polylactic acid (PLA) using fused deposition modelling, i.e., an additive manufacturing technique. The samples were mechanically tested in-plane under compression to determine their mechanical properties. We also obtained exact analytical solutions for the stiffness matrix of thick hexagonal honeycombs using both Euler-Bernoulli and Timoshenko beam theories. The stiffness matrix was then used to derive analytical relationships that describe the elastic modulus, yield stress, and Poisson's ratio of thick honeycombs. Finite element models were also built for computational analysis of the mechanical behavior of thick honeycombs under compression. The mechanical properties obtained using our analytical relationships were compared with experimental observations and computational results as well as with analytical solutions available in the literature. It was found that the analytical solutions presented here are in good agreement with experimental and computational results even for very thick honeycombs, whereas the analytical solutions available in the literature show a large deviation from experimental observation, computational results, and our analytical solutions.

  8. Mechanical Properties of Additively Manufactured Thick Honeycombs

    PubMed Central

    Hedayati, Reza; Sadighi, Mojtaba; Mohammadi Aghdam, Mohammad; Zadpoor, Amir Abbas

    2016-01-01

    Honeycombs resemble the structure of a number of natural and biological materials such as cancellous bone, wood, and cork. Thick honeycomb could be also used for energy absorption applications. Moreover, studying the mechanical behavior of honeycombs under in-plane loading could help understanding the mechanical behavior of more complex 3D tessellated structures such as porous biomaterials. In this paper, we study the mechanical behavior of thick honeycombs made using additive manufacturing techniques that allow for fabrication of honeycombs with arbitrary and precisely controlled thickness. Thick honeycombs with different wall thicknesses were produced from polylactic acid (PLA) using fused deposition modelling, i.e., an additive manufacturing technique. The samples were mechanically tested in-plane under compression to determine their mechanical properties. We also obtained exact analytical solutions for the stiffness matrix of thick hexagonal honeycombs using both Euler-Bernoulli and Timoshenko beam theories. The stiffness matrix was then used to derive analytical relationships that describe the elastic modulus, yield stress, and Poisson’s ratio of thick honeycombs. Finite element models were also built for computational analysis of the mechanical behavior of thick honeycombs under compression. The mechanical properties obtained using our analytical relationships were compared with experimental observations and computational results as well as with analytical solutions available in the literature. It was found that the analytical solutions presented here are in good agreement with experimental and computational results even for very thick honeycombs, whereas the analytical solutions available in the literature show a large deviation from experimental observation, computational results, and our analytical solutions. PMID:28773735

  9. An Introduction to the Mechanical Properties of Ceramics

    NASA Astrophysics Data System (ADS)

    Green, David J.

    1998-09-01

    Over the past twenty-five years ceramics have become key materials in the development of many new technologies as scientists have been able to design these materials with new structures and properties. An understanding of the factors that influence their mechanical behavior and reliability is essential. This book will introduce the reader to current concepts in the field. It contains problems and exercises to help readers develop their skills. This is a comprehensive introduction to the mechanical properties of ceramics, and is designed primarily as a textbook for advanced undergraduates in materials science and engineering. It will also be of value as a supplementary text for more general courses and to industrial scientists and engineers involved in the development of ceramic-based products, materials selection and mechanical design.

  10. Phase imaging of mechanical properties of live cells (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Wax, Adam

    2017-02-01

    The mechanisms by which cells respond to mechanical stimuli are essential for cell function yet not well understood. Many rheological tools have been developed to characterize cellular viscoelastic properties but these typically require direct mechanical contact, limiting their throughput. We have developed a new approach for characterizing the organization of subcellular structures using a label free, noncontact, single-shot phase imaging method that correlates to measured cellular mechanical stiffness. The new analysis approach measures refractive index variance and relates it to disorder strength. These measurements are compared to cellular stiffness, measured using the same imaging tool to visualize nanoscale responses to flow shear stimulus. The utility of the technique is shown by comparing shear stiffness and phase disorder strength across five cellular populations with varying mechanical properties. An inverse relationship between disorder strength and shear stiffness is shown, suggesting that cell mechanical properties can be assessed in a format amenable to high throughput studies using this novel, non-contact technique. Further studies will be presented which include examination of mechanical stiffness in early carcinogenic events and investigation of the role of specific cellular structural proteins in mechanotransduction.

  11. Improved mechanical properties of retorted carrots by ultrasonic pre-treatments.

    PubMed

    Day, Li; Xu, Mi; Øiseth, Sofia K; Mawson, Raymond

    2012-05-01

    The use of ultrasound pre-processing treatment, compared to blanching, to enhance mechanical properties of non-starchy cell wall materials was investigated using carrot as an example. The mechanical properties of carrot tissues were measured by compression and tensile testing after the pre-processing treatment prior to and after retorting. Carrot samples ultrasound treated for 10 min at 60 °C provided a higher mechanical strength (P<0.05) to the cell wall structure than blanching for the same time period. With the addition of 0.5% CaCl(2) in the pre-treatment solution, both blanching and ultrasound treatment showed synergistic effect on enhancing the mechanical properties of retorted carrot pieces. At a relatively short treatment time (10 min at 60 °C) with the use of 0.5% CaCl(2), ultrasound treatment achieved similar enhancement to the mechanical strength of retorted carrots to blanching for a much longer time period (i.e. 40 min). The mechanism involved appears to be related to the stress responses present in all living plant matter. However, there is a need to clarify the relative importance of the potential stress mechanisms in order to get a better understanding of the processing conditions likely to be most effective. The amount of ultrasound treatment required is likely to involve low treatment intensities and there are indications from the structural characterisation and mechanical property analyses that the plant cell wall tissues were more elastic than that accomplished using low temperature long time blanching. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

  12. Brain Mechanical Property Measurement Using MRE with Intrinsic Activation

    PubMed Central

    Pattison, Adam J.; McGarry, Matthew D.; Perreard, Irina M.; Swienckowski, Jessica G.; Eskey, Clifford J.; Lollis, S. Scott; Paulsen, Keith D.

    2013-01-01

    Problem Addressed Many pathologies alter the mechanical properties of tissue. Magnetic resonance elastography (MRE) has been developed to noninvasively characterize these quantities in vivo. Typically, small vibrations are induced in the tissue of interest with an external mechanical actuator. The resulting displacements are measured with phase contrast sequences and are then used to estimate the underlying mechanical property distribution. Several MRE studies have quantified brain tissue properties. However, the cranium and meninges, especially the dura, are very effective at damping externally applied vibrations from penetrating deeply into the brain. Here, we report a method, termed ‘intrinsic activation’, that eliminates the requirement for external vibrations by measuring the motion generated by natural blood vessel pulsation. Methodology A retrospectively gated phase contrast MR angiography sequence was used to record the tissue velocity at eight phases of the cardiac cycle. The velocities were numerically integrated via the Fourier transform to produce the harmonic displacements at each position within the brain. The displacements were then reconstructed into images of the shear modulus based on both linear elastic and poroelastic models. Results, Significance and Potential Impact The mechanical properties produced fall within the range of brain tissue estimates reported in the literature and, equally important, the technique yielded highly reproducible results. The mean shear modulus was 8.1 kPa for linear elastic reconstructions and 2.4 kPa for poroelastic reconstructions where fluid pressure carries a portion of the stress. Gross structures of the brain were visualized, particularly in the poroelastic reconstructions. Intra-subject variability was significantly less than the inter-subject variability in a study of 6 asymptomatic individuals. Further, larger changes in mechanical properties were observed in individuals when examined over time than when

  13. Brain mechanical property measurement using MRE with intrinsic activation

    NASA Astrophysics Data System (ADS)

    Weaver, John B.; Pattison, Adam J.; McGarry, Matthew D.; Perreard, Irina M.; Swienckowski, Jessica G.; Eskey, Clifford J.; Lollis, S. Scott; Paulsen, Keith D.

    2012-11-01

    Many pathologies alter the mechanical properties of tissue. Magnetic resonance elastography (MRE) has been developed to noninvasively characterize these quantities in vivo. Typically, small vibrations are induced in the tissue of interest with an external mechanical actuator. The resulting displacements are measured with phase contrast sequences and are then used to estimate the underlying mechanical property distribution. Several MRE studies have quantified brain tissue properties. However, the cranium and meninges, especially the dura, are very effective at damping externally applied vibrations from penetrating deeply into the brain. Here, we report a method, termed ‘intrinsic activation’, that eliminates the requirement for external vibrations by measuring the motion generated by natural blood vessel pulsation. A retrospectively gated phase contrast MR angiography sequence was used to record the tissue velocity at eight phases of the cardiac cycle. The velocities were numerically integrated via the Fourier transform to produce the harmonic displacements at each position within the brain. The displacements were then reconstructed into images of the shear modulus based on both linear elastic and poroelastic models. The mechanical properties produced fall within the range of brain tissue estimates reported in the literature and, equally important, the technique yielded highly reproducible results. The mean shear modulus was 8.1 kPa for linear elastic reconstructions and 2.4 kPa for poroelastic reconstructions where fluid pressure carries a portion of the stress. Gross structures of the brain were visualized, particularly in the poroelastic reconstructions. Intra-subject variability was significantly less than the inter-subject variability in a study of six asymptomatic individuals. Further, larger changes in mechanical properties were observed in individuals when examined over time than when the MRE procedures were repeated on the same day. Cardiac pulsation

  14. Cell Mechanosensitivity: Mechanical Properties and Interaction with Gravitational Field

    PubMed Central

    Ogneva, I. V.

    2013-01-01

    This paper addressed the possible mechanisms of primary reception of a mechanical stimulus by different cells. Data concerning the stiffness of muscle and nonmuscle cells as measured by atomic force microscopy are provided. The changes in the mechanical properties of cells that occur under changed external mechanical tension are presented, and the initial stages of mechanical signal transduction are considered. The possible mechanism of perception of different external mechanical signals by cells is suggested. PMID:23509748

  15. Measurement and Comparison of Mechanical Properties of Nitinol Stents

    NASA Astrophysics Data System (ADS)

    Hanus, Josef; Zahora, Jiri

    2005-01-01

    The self expandable Nitinol stents or stentgrafts are typically used for miniinvasive treatment of stenosis and aneurysms in the cardiovascular system. The minimal traumatisation of the patient, shorter time of hospitalization are typical advantages of these methods. More than ten years of experience has yielded also important information about the performance of stents in interaction with biological system and the possible problems related with it. The leakage or the shift of stent are some typical disadvantages, that can be related among other in the construction of the stent. The problem is that the mechanical properties, dimensions and the dynamical properties of the stent do not exactly correspond to the properties of the vessel or generally of tissue where this stent is introduced. The measurement, the description and the comparison of the relations between the mechanical properties of stents and tissues can be one of the possible ways to minimize these disadvantages. The developed original computer controlled measuring system allows the measurement of mechanical properties of stents, the measurement of strain-stress curves or simulation of interaction of the stent and vessel for exactly defined hemodynamic conditions. We measured and compared the mechanical parameters of different selfexpandable Nitinol stents, which differed in geometry (radius and length), in the type of construction (number of branches and rising of winding) and in the diameter of used wire. The results of measurements confirmed the theoretical assumptions that just the diameter of the Nitinol wire significantly influences the rigidity and the level of compressibility of the stent as well. A compromise must be found between the required rigidity of the stent and the minimal size of the delivery system. The exact description of the relation between the mechanical properties and geometry and construction of the stents enables to design the stent to fit the patient and it is expected that

  16. Mechanical and physical properties of agro-based fiberboard

    Treesearch

    S. Lee; T.F. Shupe; C.Y. Hse

    2006-01-01

    In order to better utilize agricultural fibers as an alternative resource for composite panels, several variables were investigated to improve mechanical and physical properties of agm-based fiberboard. This study focused on the effect of fiber morphology, slenderness ratios (UD), and fiber mixing combinations on panel properties. The panel construction types were also...

  17. Mechanical properties of contemporary composite resins and their interrelations.

    PubMed

    Thomaidis, Socratis; Kakaboura, Afrodite; Mueller, Wolf Dieter; Zinelis, Spiros

    2013-08-01

    To characterize a spectrum of mechanical properties of four representative types of modern dental resin composites and to investigate possible interrelations. Four composite resins were used, a microhybrid (Filtek Z-250), a nanofill (Filtek Ultimate), a nanohybrid (Majesty Posterior) and an ormocer (Admira). The mechanical properties investigated were Flexural Modulus and Flexural Strength (three point bending), Brinell Hardness, Impact Strength, mode I and mode II fracture toughness employing SENB and Brazilian tests and Work of Fracture. Fractographic analysis was carried out in an SEM to determine the origin of fracture for specimens subjected to SENB, Brazilian and Impact Strength testing. The results were statistically analyzed employing ANOVA and Tukey post hoc test (a=0.05) while Pearson correlation was applied among the mechanical properties. Significant differences were found between the mechanical properties of materials tested apart from mode I fracture toughness measured by Brazilian test. The latter significantly underestimated the mode I fracture toughness due to analytical limitations and thus its validity is questionable. Fractography revealed that the origin of fracture is located at notches for fracture toughness tests and contact surface with pendulum for Impact Strength testing. Pearson analysis illustrated a strong correlation between modulus of elasticity and hardness (r=0.87) and a weak negative correlation between Work of Fracture and Flexural Modulus (r=-0.46) and Work of Fracture and Hardness (r=-0.44). Weak correlations were also allocated between Flexural Modulus and Flexural Strength (r=0.40), Flexural Strength and Hardness (r=0.39), and Impact Strength and Hardness (r=0.40). Since the four types of dental resin composite tested exhibited large differences among their mechanical properties differences in their clinical performance is also anticipated. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights

  18. Towards child versus adult brain mechanical properties.

    PubMed

    Chatelin, S; Vappou, J; Roth, S; Raul, J S; Willinger, R

    2012-02-01

    The characterization of brain tissue mechanical properties is of crucial importance in the development of realistic numerical models of the human head. While the mechanical behavior of the adult brain has been extensively investigated in several studies, there is a considerable paucity of data concerning the influence of age on mechanical properties of the brain. Therefore, the implementation of child and infant head models often involves restrictive assumptions like properties scaling from adult or animal data. The present study presents a step towards the investigation of the effects of age on viscoelastic properties of human brain tissue from a first set of dynamic oscillatory shear experiments. Tests were also performed on three different locations of brain (corona radiata, thalamus and brainstem) in order to investigate regional differences. Despite the limited number of child brain samples a significant increase in both storage and loss moduli occurring between the age of 5 months and the age of 22 months was found, confirmed by statistical Student's t-tests (p=0.104,0.038 and 0.054 for respectively corona radiata, thalamus and brain stem samples locations respectively). The adult brain appears to be 3-4 times stiffer than the young child one. Moreover, the brainstem was found to be approximately 2-3 times stiffer than both gray and white matter from corona radiata and thalamus. As a tentative conclusion, this study provides the first rheological data on the human brain at different ages and brain regions. This data could be implemented in numerical models of the human head, especially in models concerning pediatric population. Copyright © 2011 Elsevier Ltd. All rights reserved.

  19. Differences in time-dependent mechanical properties between extruded and molded hydrogels

    PubMed Central

    Ersumo, N; Witherel, CE; Spiller, KL

    2016-01-01

    The mechanical properties of hydrogels used in biomaterials and tissue engineering applications are critical determinants of their functionality. Despite the recent rise of additive manufacturing, and specifically extrusion-based bioprinting, as a prominent biofabrication method, comprehensive studies investigating the mechanical behavior of extruded constructs remain lacking. To address this gap in knowledge, we compared the mechanical properties and swelling properties of crosslinked gelatin-based hydrogels prepared by conventional molding techniques or by 3D bioprinting using a BioBots Beta pneumatic extruder. A preliminary characterization of the impact of bioprinting parameters on construct properties revealed that both Young's modulus and optimal extruding pressure increased with polymer content, and that printing resolution increased with both printing speed and nozzle gauge. High viability (>95%) of encapsulated NIH 3T3 fibroblasts confirmed the cytocompatibility of the construct preparation process. Interestingly, the Young's moduli of extruded and molded constructs were not different, but extruded constructs did show increases in both the rate and extent of time-dependent mechanical behavior observed in creep. Despite similar polymer densities, extruded hydrogels showed greater swelling over time compared to molded hydrogels, suggesting that differences in creep behavior derived from differences in microstructure and fluid flow. Because of the crucial roles of time-dependent mechanical properties, fluid flow, and swelling properties on tissue and cell behavior, these findings highlight the need for greater consideration of the effects of the extrusion process on hydrogel properties. PMID:27550945

  20. Study of hepatocyte plasma membrane mechanical properties using optical trapping

    NASA Astrophysics Data System (ADS)

    Vedyaykin, A. D.; Morozova, N. E.; Pobegalov, G. E.; Arseniev, A. N.; Khodorkoskii, M. A.; Sabantsev, A. V.

    2014-12-01

    In this paper we describe the use of membrane tether formation technique which is widely used to study mechanical properties of plasma membranes. This method was successfully used for the direct measurement of parameters characterizing membranes mechanical properties (static tether tension force and effective membrane viscosity) of human hepatocytes (HepG2 hepatocellular carcinoma line). These results allow using this method in future for diagnostics of the cell membrane, evaluating the influence on the mechanical parameters of various factors, including toxins and drugs.

  1. Mechanical Properties of Nylon Harp Strings.

    PubMed

    Lynch-Aird, Nicolas; Woodhouse, Jim

    2017-05-04

    Monofilament nylon strings with a range of diameters, commercially marketed as harp strings, have been tested to establish their long-term mechanical properties. Once a string had settled into a desired stress state, the Young's modulus was measured by a variety of methods that probe different time-scales. The modulus was found to be a strong function of testing frequency and also a strong function of stress. Strings were also subjected to cyclical variations of temperature, allowing various thermal properties to be measured: the coefficient of linear thermal expansion and the thermal sensitivities of tuning, Young's modulus and density. The results revealed that the particular strings tested are divided into two groups with very different properties: stress-strain behaviour differing by a factor of two and some parametric sensitivities even having the opposite sign. Within each group, correlation studies allowed simple functional fits to be found to the key properties, which have the potential to be used in automated tuning systems for harp strings.

  2. Artificial insect wings with biomimetic wing morphology and mechanical properties.

    PubMed

    Liu, Zhiwei; Yan, Xiaojun; Qi, Mingjing; Zhu, Yangsheng; Huang, Dawei; Zhang, Xiaoyong; Lin, Liwei

    2017-09-26

    The pursuit of a high lift force for insect-scale flapping-wing micro aerial vehicles (FMAVs) requires that their artificial wings possess biomimetic wing features which are close to those of their natural counterpart. In this work, we present both fabrication and testing methods for artificial insect wings with biomimetic wing morphology and mechanical properties. The artificial cicada (Hyalessa maculaticollis) wing is fabricated through a high precision laser cutting technique and a bonding process of multilayer materials. Through controlling the shape of the wing venation, the fabrication method can achieve three-dimensional wing architecture, including cambers or corrugations. Besides the artificial cicada wing, the proposed fabrication method also shows a promising versatility for diverse wing types. Considering the artificial cicada wing's characteristics of small size and light weight, special mechanical testing systems are designed to investigate its mechanical properties. Flexural stiffness, maximum deformation rate and natural frequency are measured and compared with those of its natural counterpart. Test results reveal that the mechanical properties of the artificial cicada wing depend strongly on its vein thickness, which can be used to optimize an artificial cicada wing's mechanical properties in the future. As such, this work provides a new form of artificial insect wings which can be used in the field of insect-scale FMAVs.

  3. Loops determine the mechanical properties of mitotic chromosomes

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Heermann, Dieter W.

    2013-03-01

    In mitosis, chromosomes undergo a condensation into highly compacted, rod-like objects. Many models have been put forward for the higher-order organization of mitotic chromosomes including radial loop and hierarchical folding models. Additionally, mechanical properties of mitotic chromosomes under different conditions were measured. However, the internal organization of mitotic chromosomes still remains unclear. Here we present a polymer model for mitotic chromosomes and show how chromatin loops play a major role for their mechanical properties. The key assumption of the model is the ability of the chromatin fibre to dynamically form loops with the help of binding proteins. Our results show that looping leads to a tight compaction and significantly increases the bending rigidity of chromosomes. Moreover, our qualitative prediction of the force elongation behaviour is close to experimental findings. This indicates that the internal structure of mitotic chromosomes is based on self-organization of the chromatin fibre. We also demonstrate how number and size of loops have a strong influence on the mechanical properties. We suggest that changes in the mechanical characteristics of chromosomes can be explained by an altered internal loop structure. YZ gratefully appreciates funding by the German National Academic Foundation (Studienstiftung des deutschen Volkes) and support by the Heidelberg Graduate School for Mathematical and Computational Methods in the Sciences (HGS MathComp).

  4. Mechanical properties of amyloid-like fibrils defined by secondary structures

    NASA Astrophysics Data System (ADS)

    Bortolini, C.; Jones, N. C.; Hoffmann, S. V.; Wang, C.; Besenbacher, F.; Dong, M.

    2015-04-01

    Amyloid and amyloid-like fibrils represent a generic class of highly ordered nanostructures that are implicated in some of the most fatal neurodegenerative diseases. On the other hand, amyloids, by possessing outstanding mechanical robustness, have also been successfully employed as functional biomaterials. For these reasons, physical and chemical factors driving fibril self-assembly and morphology are extensively studied - among these parameters, the secondary structures and the pH have been revealed to be crucial, since a variation in pH changes the fibril morphology and net chirality during protein aggregation. It is important to quantify the mechanical properties of these fibrils in order to help the design of effective strategies for treating diseases related to the presence of amyloid fibrils. In this work, we show that by changing pH the mechanical properties of amyloid-like fibrils vary as well. In particular, we reveal that these mechanical properties are strongly related to the content of secondary structures. We analysed and estimated the Young's modulus (E) by comparing the persistence length (Lp) - measured from the observation of TEM images by using statistical mechanics arguments - with the mechanical information provided by peak force quantitative nanomechanical property mapping (PF-QNM). The secondary structure content and the chirality are investigated by means of synchrotron radiation circular dichroism (SR-CD). Results arising from this study could be fruitfully used as a protocol to investigate other medical or engineering relevant peptide fibrils.Amyloid and amyloid-like fibrils represent a generic class of highly ordered nanostructures that are implicated in some of the most fatal neurodegenerative diseases. On the other hand, amyloids, by possessing outstanding mechanical robustness, have also been successfully employed as functional biomaterials. For these reasons, physical and chemical factors driving fibril self-assembly and morphology

  5. The effects of multiple repairs on Inconel 718 weld mechanical properties

    NASA Technical Reports Server (NTRS)

    Russell, C. K.; Nunes, A. C., Jr.; Moore, D.

    1991-01-01

    Inconel 718 weldments were repaired 3, 6, 9, and 13 times using the gas tungsten arc welding process. The welded panels were machined into mechanical test specimens, postweld heat treated, and nondestructively tested. Tensile properties and high cycle fatigue life were evaluated and the results compared to unrepaired weld properties. Mechanical property data were analyzed using the statistical methods of difference in means for tensile properties and difference in log means and Weibull analysis for high cycle fatigue properties. Statistical analysis performed on the data did not show a significant decrease in tensile or high cycle fatigue properties due to the repeated repairs. Some degradation was observed in all properties, however, it was minimal.

  6. Optical measurement of arterial mechanical properties: from atherosclerotic plaque initiation to rupture

    NASA Astrophysics Data System (ADS)

    Nadkarni, Seemantini K.

    2013-12-01

    During the pathogenesis of coronary atherosclerosis, from lesion initiation to rupture, arterial mechanical properties are altered by a number of cellular, molecular, and hemodynamic processes. There is growing recognition that mechanical factors may actively drive vascular cell signaling and regulate atherosclerosis disease progression. In advanced plaques, the mechanical properties of the atheroma influence stress distributions in the fibrous cap and mediate plaque rupture resulting in acute coronary events. This review paper explores current optical technologies that provide information on the mechanical properties of arterial tissue to advance our understanding of the mechanical factors involved in atherosclerosis development leading to plaque rupture. The optical approaches discussed include optical microrheology and traction force microscopy that probe the mechanical behavior of single cell and extracellular matrix components, and intravascular imaging modalities including laser speckle rheology, optical coherence elastography, and polarization-sensitive optical coherence tomography to measure the mechanical properties of advanced coronary lesions. Given the wealth of information that these techniques can provide, optical imaging modalities are poised to play an increasingly significant role in elucidating the mechanical aspects of coronary atherosclerosis in the future.

  7. Contribution of cytoskeletal elements to the axonal mechanical properties

    PubMed Central

    2013-01-01

    Background Microtubules, microfilaments, and neurofilaments are cytoskeletal elements that affect cell morphology, cellular processes, and mechanical structures in neural cells. The objective of the current study was to investigate the contribution of each type of cytoskeletal element to the mechanical properties of axons of dorsal root and sympathetic ganglia cells in chick embryos. Results Microtubules, microfilaments, and neurofilaments in axons were disrupted by nocodazole, cytochalasin D, and acrylamide, respectively, or a combination of the three. An atomic force microscope (AFM) was then used to compress the treated axons, and the resulting corresponding force-deformation information was analyzed to estimate the mechanical properties of axons that were partially or fully disrupted. Conclusion We have found that the mechanical stiffness was most reduced in microtubules-disrupted-axons, followed by neurofilaments-disrupted- and microfilaments-disrupted-axons. This suggests that microtubules contribute the most of the mechanical stiffness to axons. PMID:24007256

  8. Mechanical and Fatigue Properties of Additively Manufactured Metallic Materials

    NASA Astrophysics Data System (ADS)

    Yadollahi, Aref

    This study aims to investigate the mechanical and fatigue behavior of additively manufactured metallic materials. Several challenges associated with different metal additive manufacturing (AM) techniques (i.e. laser-powder bed fusion and direct laser deposition) have been addressed experimentally and numerically. Experiments have been carried out to study the effects of process inter-layer time interval--i.e. either building the samples one-at-a-time or multi-at-a-time (in-parallel)--on the microstructural features and mechanical properties of 316L stainless steel samples, fabricated via a direct laser deposition (DLD). Next, the effect of building orientation--i.e. the orientation in which AM parts are built--on microstructure, tensile, and fatigue behaviors of 17-4 PH stainless steel, fabricated via a laser-powder bed fusion (L-PBF) method was investigated. Afterwards, the effect of surface finishing--here, as-built versus machined--on uniaxial fatigue behavior and failure mechanisms of Inconel 718 fabricated via a laser-powder bed fusion technique was sought. The numerical studies, as part of this dissertation, aimed to model the mechanical behavior of AM materials, under monotonic and cyclic loading, based on the observations and findings from the experiments. Despite significant research efforts for optimizing process parameters, achieving a homogenous, defect-free AM product--immediately after fabrication--has not yet been fully demonstrated. Thus, one solution for ensuring the adoption of AM materials for application should center on predicting the variations in mechanical behavior of AM parts based on their resultant microstructure. In this regard, an internal state variable (ISV) plasticity-damage model was employed to quantify the damage evolution in DLD 316L SS, under tensile loading, using the microstructural features associated with the manufacturing process. Finally, fatigue behavior of AM parts has been modeled based on the crack-growth concept

  9. Mechanical properties evaluation of extruded wood polymer composites

    NASA Astrophysics Data System (ADS)

    Zaini, A. S. Syah M.; Rus, Anika Zafiah M.; Rahman, Norherman Abdul; Jais, Farhana Hazwanee M.; Fauzan, M. Zarif; Sufian, N. Afiqah

    2017-09-01

    The rapidly expanding of interest in the manufacture of composite materials from waste industrial and agricultural materials is due to high demand for environmentally friendly materials. Wood polymer composite (WPC) are being used in many type of applications such as in the automobile, electronic, aerospace industry and construction. Therefore, this research study is to determine the mechanical properties behaviour of WPC after an extended Ultra Violet (UV) irradiation exposure. The fabricated sample has been used and to be compared in this research is consists of rice husk, waste fibre and polypropylene (PP) with 4 different types of WPC which are wood block waste (WBW), wood block virgin (WBV), wood sheet (WS) and wood sheet waste (WSW). The extruded specimens were tested for mechanical properties such as strength under compression, puncture strength and impact resistance, and density. In addition, the specimen has been irradiated with the UV exposure at 5000 hours, 10000 hours and 15000 hours. Generally, the mechanical properties the WPC which made from the recycled material were lower than the WPC from virgin material but the density was comparable between the two products after UV irradiation exposure.

  10. Structure and mechanical properties of Octopus vulgaris suckers.

    PubMed

    Tramacere, Francesca; Kovalev, Alexander; Kleinteich, Thomas; Gorb, Stanislav N; Mazzolai, Barbara

    2014-02-06

    In this study, we investigate the morphology and mechanical features of Octopus vulgaris suckers, which may serve as a model for the creation of a new generation of attachment devices. Octopus suckers attach to a wide range of substrates in wet conditions, including rough surfaces. This amazing feature is made possible by the sucker's tissues, which are pliable to the substrate profile. Previous studies have described a peculiar internal structure that plays a fundamental role in the attachment and detachment processes of the sucker. In this work, we present a mechanical characterization of the tissues involved in the attachment process, which was performed using microindentation tests. We evaluated the elasticity modulus and viscoelastic parameters of the natural tissues (E ∼ 10 kPa) and measured the mechanical properties of some artificial materials that have previously been used in soft robotics. Such a comparison of biological prototypes and artificial material that mimics octopus-sucker tissue is crucial for the design of innovative artificial suction cups for use in wet environments. We conclude that the properties of the common elastomers that are generally used in soft robotics are quite dissimilar to the properties of biological suckers.

  11. Structure and mechanical properties of Octopus vulgaris suckers

    PubMed Central

    Tramacere, Francesca; Kovalev, Alexander; Kleinteich, Thomas; Gorb, Stanislav N.; Mazzolai, Barbara

    2014-01-01

    In this study, we investigate the morphology and mechanical features of Octopus vulgaris suckers, which may serve as a model for the creation of a new generation of attachment devices. Octopus suckers attach to a wide range of substrates in wet conditions, including rough surfaces. This amazing feature is made possible by the sucker's tissues, which are pliable to the substrate profile. Previous studies have described a peculiar internal structure that plays a fundamental role in the attachment and detachment processes of the sucker. In this work, we present a mechanical characterization of the tissues involved in the attachment process, which was performed using microindentation tests. We evaluated the elasticity modulus and viscoelastic parameters of the natural tissues (E ∼ 10 kPa) and measured the mechanical properties of some artificial materials that have previously been used in soft robotics. Such a comparison of biological prototypes and artificial material that mimics octopus-sucker tissue is crucial for the design of innovative artificial suction cups for use in wet environments. We conclude that the properties of the common elastomers that are generally used in soft robotics are quite dissimilar to the properties of biological suckers. PMID:24284894

  12. Length-dependent mechanical properties of gold nanowires

    NASA Astrophysics Data System (ADS)

    Han, Jing; Fang, Liang; Sun, Jiapeng; Han, Ying; Sun, Kun

    2012-12-01

    The well-known "size effect" is not only related to the diameter but also to the length of the small volume materials. It is unfortunate that the length effect on the mechanical behavior of nanowires is rarely explored in contrast to the intensive studies of the diameter effect. The present paper pays attention to the length-dependent mechanical properties of <111>-oriented single crystal gold nanowires employing the large-scale molecular dynamics simulation. It is discovered that the ultrashort Au nanowires exhibit a new deformation and failure regime-high elongation and high strength. The constrained dislocation nucleation and transient dislocation slipping are observed as the dominant mechanism for such unique combination of high strength and high elongation. A mechanical model based on image force theory is developed to provide an insight to dislocation nucleation and capture the yield strength and nucleation site of first partial dislocation indicated by simulation results. Increasing the length of the nanowires, the ductile-to-brittle transition is confirmed. And the new explanation is suggested in the predict model of this transition. Inspired by the superior properties, a new approach to strengthen and toughen nanowires-hard/soft/hard sandwich structured nanowires is suggested. A preliminary evidence from the molecular dynamics simulation corroborates the present opinion.

  13. Autoclaving and clinical recycling: effects on mechanical properties of orthodontic wires.

    PubMed

    Oshagh, M; Hematiyan, M R; Mohandes, Y; Oshagh, M R; Pishbin, L

    2012-01-01

    About half of the orthodontists recycle and reuse orthodontic wires because of their costs. So when talking about reuse and sterilization of wires, their effects on mechanical properties of wires should be clarified. The purpose of this study was to assess the effects of sterilization and clinical use on mechanical properties of stainless steel wires. Thirty stainless steel orthodontic wires were divided into three equal groups of control, autoclave (sterilized by autoclave), and recycle group (wires were used for orthodontic patients up to 4 weeks, cleaned by isopropyl alcohol and sterilized by autoclave). The mechanical properties (tensile test, three-point loading test for load-deflection curve) were determined. Fracture force, yield strength, stiffness and modulus of elasticity in recycle groups were significantly lower than the other groups (P < 0.05). Although recycle wires were softer than those of control group, relatively small differences and also various properties of available wires have obscured the clinical predictability of their application. There is seemingly no problem in terms of mechanical properties to recycle orthodontic wires.

  14. Improvement of the mechanical properties of reinforced aluminum foam samples

    NASA Astrophysics Data System (ADS)

    Formisano, A.; Barone, A.; Carrino, L.; De Fazio, D.; Langella, A.; Viscusi, A.; Durante, M.

    2018-05-01

    Closed-cell aluminum foam has attracted increasing attention due to its very interesting properties, thanks to which it is expected to be used as both structural and functional material. A research challenge is the improvement of the mechanical properties of foam-based structures adopting a reinforced approach that does not compromise their lightness. Consequently, the aim of this research is the fabrication of enhanced aluminum foam samples without significantly increasing their original weight. In this regard, cylindrical samples with a core of closed-cell aluminum foam and a skin of fabrics and grids of different materials were fabricated in a one step process and were mechanically characterized, in order to investigate their behaviour and to compare their mechanical properties to the ones of the traditional foam.

  15. Experimental measurement and modeling analysis on mechanical properties of incudostapedial joint

    PubMed Central

    Zhang, Xiangming

    2011-01-01

    The incudostapedial (IS) joint between the incus and stapes is a synovial joint consisting of joint capsule, cartilage, and synovial fluid. The mechanical properties of the IS joint directly affect the middle ear transfer function for sound transmission. However, due to the complexity and small size of the joint, the mechanical properties of the IS joint have not been reported in the literature. In this paper, we report our current study on mechanical properties of human IS joint using both experimental measurement and finite element (FE) modeling analysis. Eight IS joint samples with the incus and stapes attached were harvested from human cadaver temporal bones. Tension, compression, stress relaxation and failure tests were performed on those samples in a micro-material testing system. An analytical approach with the hyperelastic Ogden model and a 3D FE model of the IS joint including the cartilage, joint capsule, and synovial fluid were employed to derive mechanical parameters of the IS joint. The comparison of measurements and modeling results reveals the relationship between the mechanical properties and structure of the IS joint. PMID:21061141

  16. Experimental measurement and modeling analysis on mechanical properties of incudostapedial joint.

    PubMed

    Zhang, Xiangming; Gan, Rong Z

    2011-10-01

    The incudostapedial (IS) joint between the incus and stapes is a synovial joint consisting of joint capsule, cartilage, and synovial fluid. The mechanical properties of the IS joint directly affect the middle ear transfer function for sound transmission. However, due to the complexity and small size of the joint, the mechanical properties of the IS joint have not been reported in the literature. In this paper, we report our current study on mechanical properties of human IS joint using both experimental measurement and finite element (FE) modeling analysis. Eight IS joint samples with the incus and stapes attached were harvested from human cadaver temporal bones. Tension, compression, stress relaxation and failure tests were performed on those samples in a micro-material testing system. An analytical approach with the hyperelastic Ogden model and a 3D FE model of the IS joint including the cartilage, joint capsule, and synovial fluid were employed to derive mechanical parameters of the IS joint. The comparison of measurements and modeling results reveals the relationship between the mechanical properties and structure of the IS joint.

  17. Passive and active mechanical properties of biotemplated ceramics revisited.

    PubMed

    Van Opdenbosch, Daniel; Fritz-Popovski, Gerhard; Plank, Johann; Zollfrank, Cordt; Paris, Oskar

    2016-10-13

    Living nature and human technology apply different principles to create hard, strong and tough materials. In this review, we compare and discuss prominent aspects of these alternative strategies, and demonstrate for selected examples that nanoscale-precision biotemplating is able to produce uncommon mechanical properties as well as actuating behavior, resembling to some extent the properties of the original natural templates. We present and discuss mechanical testing data showing for the first time that nanometer-precision biotemplating can lead to porous ceramic materials with deformation characteristics commonly associated with either biological or highly advanced technical materials. We also review recent findings on the relation between hierarchical structuring and humidity-induced directional motion. Finally, we discuss to which extent the observed behavior is in agreement with previous results and theories on the mechanical properties of multiscale hierarchical materials, as well as studies of highly disperse technical materials, together with an outlook for further lines of investigation.

  18. Intrinsic and extrinsic mechanical properties related to the differentiation of mesenchymal stem cells.

    PubMed

    Lee, Jin-Ho; Park, Hun-Kuk; Kim, Kyung Sook

    2016-05-06

    Diverse intrinsic and extrinsic mechanical factors have a strong influence on the regulation of stem cell fate. In this work, we examined recent literature on the effects of mechanical environments on stem cells, especially on differentiation of mesenchymal stem cells (MSCs). We provide a brief review of intrinsic mechanical properties of single MSC and examined the correlation between the intrinsic mechanical property of MSC and the differentiation ability. The effects of extrinsic mechanical factors relevant to the differentiation of MSCs were considered separately. The effect of nanostructure and elasticity of the matrix on the differentiation of MSCs were summarized. Finally, we consider how the extrinsic mechanical properties transfer to MSCs and then how the effects on the intrinsic mechanical properties affect stem cell differentiation. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. Mechanical properties of organic semiconductors for mechanically stable and intrinsically stretchable solar cells (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Lipomi, Darren J.

    2016-09-01

    This presentation describes my group's efforts to understand the molecular and microstructural basis for the mechanical properties of organic semiconductors for organic photovoltaic (OPV) devices. Our work is motivated by two goals. The first goal is to mitigate mechanical forms of degradation of printed modules during roll-to-roll fabrication, installation, and environmental forces—i.e., wind, rain, snow, and thermal expansion and contraction. Mechanical stability is a prerequisite for inexpensive processing on flexible substrates: to encapsulate devices in glass is to surrender this advantage. The second goal is to enable the next generation of ultra-flexible and stretchable solar cells for collapsible, portable, and wearable applications, and as low-cost sources of energy—"solar tarps"—for disaster relief and for the developing world. It may seem that organic semiconductors, due to their carbon framework, are already sufficiently compliant for these applications. We have found, however, that the mechanical properties (stiffness and brittleness) occupy a wide range of values, and can be difficult to predict from molecular structure alone. We are developing an experimental and theoretical framework for how one can combine favorable charge-transport properties and mechanical compliance in organic semiconductor films. In particular, we have explored the roles of the backbone, alkyl side chain, microstructural order, the glass transition, molecular packing with fullerenes, plasticizing effects of additives, extent of separation of [60]PCBM and [70]PCBM, structural randomness in low-bandgap polymers, and reinforcement by encapsulation, on the mechanical compliance. We are exploring the applicability of semi-empirical "back-of-the-envelope" models, along with multi-scale molecular dynamics simulations, with the ultimate goal of designing electroactive organic materials whose mechanical properties can be dialed-in. We have used the insights we have developed to

  20. Rib biomechanical properties exhibit diagnostic potential for accurate ageing in forensic investigations

    PubMed Central

    Bonicelli, Andrea; Xhemali, Bledar; Kranioti, Elena F.

    2017-01-01

    Age estimation remains one of the most challenging tasks in forensic practice when establishing a biological profile of unknown skeletonised remains. Morphological methods based on developmental markers of bones can provide accurate age estimates at a young age, but become highly unreliable for ages over 35 when all developmental markers disappear. This study explores the changes in the biomechanical properties of bone tissue and matrix, which continue to change with age even after skeletal maturity, and their potential value for age estimation. As a proof of concept we investigated the relationship of 28 variables at the macroscopic and microscopic level in rib autopsy samples from 24 individuals. Stepwise regression analysis produced a number of equations one of which with seven variables showed an R2 = 0.949; a mean residual error of 2.13 yrs ±0.4 (SD) and a maximum residual error value of 2.88 yrs. For forensic purposes, by using only bench top machines in tests which can be carried out within 36 hrs, a set of just 3 variables produced an equation with an R2 = 0.902 a mean residual error of 3.38 yrs ±2.6 (SD) and a maximum observed residual error 9.26yrs. This method outstrips all existing age-at-death methods based on ribs, thus providing a novel lab based accurate tool in the forensic investigation of human remains. The present application is optimised for fresh (uncompromised by taphonomic conditions) remains, but the potential of the principle and method is vast once the trends of the biomechanical variables are established for other environmental conditions and circumstances. PMID:28520764

  1. Prediction of mechanical and wear properties of 6026 aluminum alloy waste to be used in prosthetics limbs

    NASA Astrophysics Data System (ADS)

    Arbilei, Marwan N.

    2018-05-01

    This paper aimed to recycle high power electrical wires west in prosthetics limbs manufacturing. The effect of grain size on mechanical properties (Hardness and Tensile Strength), and wear resistance of commercial 6026 T9 Aluminum alloys that used in electrical industry have been modeled to be predicted. Six sets of samples were prepared with different annealing heat treatment parameters, (300,350 and 400)°C with (1 and 2) hours. Each treatment gained different grain sizes (23-71) μm and evenly HV (61-169) values. The grain size that produced from heat treatments was ranged from. Tensile properties regarding HV have been reviewed and all data haven collected to create a mathematical model showing the relation between Tensile strength and Hardness. The Sliding wear tests applied with (3 and 8) N with five periods (20-100) minutes. Multiple regression model prepared for predicting the values of weight loss for wear process. The model was tested and validated for the properties. The main purpose of this research is to provide an effective and accurate way to predict weight loose rate in wear process.

  2. Comparison of mechanical properties for several electrical spring contact alloys

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nordstrom, Terry V.

    Work was conducted to determine whether beryllium-nickel alloy 440 had mechanical properties which made it suitable as a substitute for the presently used precious metal contact alloys Paliney 7 and Neyoro G, in certain electrical contact applications. Possible areas of applicability for the alloy were where extremely low contact resistance was not necessary or in components encountering elevated temperatures above those presently seen in weapons applications. Evaluation of the alloy involved three major experimental areas: 1) measurement of the room temperature microplastic (epsilon approximately 10/sup -6/) and macroplastic (epsilon approximately 10/sup -3/) behavior of alloy 440 in various age hardeningmore » conditions, 2) determination of applied stress effects on stress relaxation or contact force loss and 3) measurement of elevated temperature mechanical properties and stress relaxation behavior. Similar measurements were also made on Neyoro G and Paliney 7 for comparison. The primary results of the study show that beryllium-nickel alloy 440 is from a mechanical properties standpoint, equal or superior to the presently used Paliney 7 and Neyoro G for normal Sandia requirements. For elevated temperature applications, alloy 440 has clearly superior mechanical properties.« less

  3. Accurate thermoelastic tensor and acoustic velocities of NaCl

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Marcondes, Michel L., E-mail: michel@if.usp.br; Chemical Engineering and Material Science, University of Minnesota, Minneapolis, 55455; Shukla, Gaurav, E-mail: shukla@physics.umn.edu

    Despite the importance of thermoelastic properties of minerals in geology and geophysics, their measurement at high pressures and temperatures are still challenging. Thus, ab initio calculations are an essential tool for predicting these properties at extreme conditions. Owing to the approximate description of the exchange-correlation energy, approximations used in calculations of vibrational effects, and numerical/methodological approximations, these methods produce systematic deviations. Hybrid schemes combining experimental data and theoretical results have emerged as a way to reconcile available information and offer more reliable predictions at experimentally inaccessible thermodynamics conditions. Here we introduce a method to improve the calculated thermoelastic tensor bymore » using highly accurate thermal equation of state (EoS). The corrective scheme is general, applicable to crystalline solids with any symmetry, and can produce accurate results at conditions where experimental data may not exist. We apply it to rock-salt-type NaCl, a material whose structural properties have been challenging to describe accurately by standard ab initio methods and whose acoustic/seismic properties are important for the gas and oil industry.« less

  4. Mechanical properties of experimental composites with different calcium phosphates fillers.

    PubMed

    Okulus, Zuzanna; Voelkel, Adam

    2017-09-01

    Calcium phosphates (CaPs)-containing composites have already shown good properties from the point of view of dental restorative materials. The purpose of this study was to examine the crucial mechanical properties of twelve hydroxyapatite- or tricalcium phosphate-filled composites. The raw and surface-treated forms of both CaP fillers were applied. As a reference materials two experimental glass-containing composites and one commercial dental restorative composite were applied. Nano-hardness, elastic modulus, compressive, flexural and diametral tensile strength of all studied materials were determined. Application of statistical methods (one-way analysis of variance and cluster agglomerative analysis) allowed for assessing the similarities between examined materials according to the values of studied parameters. The obtained results show that in almost all cases the mechanical properties of experimental CaPs-composites are comparable or even better than mechanical properties of examined reference materials. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Mechanical properties of kinked silicon nanowires

    NASA Astrophysics Data System (ADS)

    Jing, Yuhang; Zhang, Chuan; Liu, Yingzhi; Guo, Licheng; Meng, Qingyuan

    2015-04-01

    Molecular dynamics simulations are used to investigate the mechanical properties of KSiNWs. Our results show that KSiNWs have a much larger fracture strain compared to straight SiNWs. The effects of the periodic length of KSiNWs with symmetric arms and the arm length of the KSiNW with asymmetric arms on the mechanical properties of KSiNWs are studied. The fracture stress of KSiNWs decrease as the periodic length increases. However, the fracture strain of KSiNWs is not dependent on the short periodic length and the fracture strain of KSiNWs will abruptly increase to very large value and then vary slightly as the periodic length increases. In addition, the fracture stress is not dependent on arm length while the fracture strain monotonically increases as the arm length increases. We also investigate the fracture process of KSiNWs. The results in this paper suggest that the KSiNWs with larger fracture strain can be a promising anode materials in high performance Li-ion batteries.

  6. Mechanical properties of some materials used in airplane construction

    NASA Technical Reports Server (NTRS)

    Wolff, E B; Van Ewijk, L J G

    1928-01-01

    Since lightness is desirable in airplane construction, greater stresses must be tolerated than in other kinds of construction. It is therefore necessary to have a more accurate knowledge of the greatest stresses that may occur and of the actual properties of the materials used. The Aeronautic Research Laboratories took the limit of elasticity as the basis of the strength calculations. Many tests were made of different steels, woods, aluminum alloys, and fabrics.

  7. Metallurgical Mechanisms Controlling Mechanical Properties of Aluminum Alloy 2219 Produced By Electron Beam Freeform Fabrication

    NASA Technical Reports Server (NTRS)

    Domack, Marcia S.; Taminger, Karen M. B.; Begley, Matthew

    2006-01-01

    The electron beam freeform fabrication (EBF3) layer-additive manufacturing process has been developed to directly fabricate complex geometry components. EBF3 introduces metal wire into a molten pool created on the surface of a substrate by a focused electron beam. Part geometry is achieved by translating the substrate with respect to the beam to build the part one layer at a time. Tensile properties have been demonstrated for electron beam deposited aluminum and titanium alloys that are comparable to wrought products, although the microstructures of the deposits exhibit features more typical of cast material. Understanding the metallurgical mechanisms controlling mechanical properties is essential to maximizing application of the EBF3 process. In the current study, mechanical properties and resulting microstructures were examined for aluminum alloy 2219 fabricated over a range of EBF3 process variables. Material performance was evaluated based on tensile properties and results were compared with properties of Al 2219 wrought products. Unique microstructures were observed within the deposited layers and at interlayer boundaries, which varied within the deposit height due to microstructural evolution associated with the complex thermal history experienced during subsequent layer deposition. Microstructures exhibited irregularly shaped grains, typically with interior dendritic structures, which were described based on overall grain size, morphology, distribution, and dendrite spacing, and were correlated with deposition parameters. Fracture features were compared with microstructural elements to define fracture paths and aid in definition of basic processing-microstructure-property correlations.

  8. Mechanical Properties of Nonwoven Reinforced Thermoplastic Polyurethane Composites

    PubMed Central

    Tausif, Muhammad; Pliakas, Achilles; O’Haire, Tom; Goswami, Parikshit; Russell, Stephen J.

    2017-01-01

    Reinforcement of flexible fibre reinforced plastic (FRP) composites with standard textile fibres is a potential low cost solution to less critical loading applications. The mechanical behaviour of FRPs based on mechanically bonded nonwoven preforms composed of either low or high modulus fibres in a thermoplastic polyurethane (TPU) matrix were compared following compression moulding. Nonwoven preform fibre compositions were selected from lyocell, polyethylene terephthalate (PET), polyamide (PA) as well as para-aramid fibres (polyphenylene terephthalamide; PPTA). Reinforcement with standard fibres manifold improved the tensile modulus and strength of the reinforced composites and the relationship between fibre, fabric and composite’s mechanical properties was studied. The linear density of fibres and the punch density, a key process variable used to consolidate the nonwoven preform, were varied to study the influence on resulting FRP mechanical properties. In summary, increasing the strength and degree of consolidation of nonwoven preforms did not translate to an increase in the strength of resulting fibre reinforced TPU-composites. The TPU composite strength was mainly dependent upon constituent fibre stress-strain behaviour and fibre segment orientation distribution. PMID:28772977

  9. Near surface mechanical properties of optical single crystals and surface response to deterministic microgrinding

    NASA Astrophysics Data System (ADS)

    Randi, Joseph A., III

    2005-12-01

    This thesis makes use of microindentation, nanoindentation and nanoscratching methods to better understand the mechanical properties of single crystalline silicon, calcium fluoride, and magnesium fluoride. These properties are measured and are used to predict the material's response to material removal, specifically by grinding and polishing, which is a combination of elastic, plastic and fracture processes. The hardness anisotropy during Knoop microindentation, hardness from nanoindentation, and scratch morphology from nanoscratching are reported. This information is related to the surface microroughness from grinding. We show that mechanical property relationships that predict the surface roughness from lapping and deterministic microgrinding of optical glasses are applicable to single crystals. We show the range of hardness from some of the more common crystallographic faces. Magnesium fluoride, having a tetragonal structure, has 2-fold hardness anisotropy. Nanoindentation, as expected provides higher hardness than microindentation, but anisotropy is not observed. Nanoscratching provides the scratch profile during loading, after the load has been removed, and the coefficient of friction during the loading. Ductile and brittle mode scratching is present with brittle mode cracking being orientation specific. Subsurface damage (SSD) measurements are made using a novel process known as the MRF technique. Magnetorheological finishing is used to polish spots into the ground surface where SSD can be viewed. SSD is measured using an optical microscope and knowledge of the spot profile. This technique is calibrated with a previous technique and implemented to accurately measure SSD in single crystals. The data collected are compared to the surface microroughness of the ground surface, resulting in an upper bound relationship. The results indicate that SSD is always less than 1.4 times the peak-to-valley surface microroughness for single crystals regardless of the

  10. Effect of stacking sequence on mechanical properties neem wood veneer plastic composites

    NASA Astrophysics Data System (ADS)

    Nagamadhu, M.; Kumar, G. C. Mohan; Jeyaraj, P.

    2018-04-01

    This study investigates the effect of wood veneer stacking sequence on mechanical properties of neem wood polymer composite (WPC) experimentally. Wood laminated samples were fabricated by conventional hand layup technique in a mold and cured under pressure at room temperature and then post cured at elevated temperature. Initially, the tensile, flexural, and impact test were conducted to understand the effect of weight fraction of fiber on mechanical properties. The mechanical properties have increased with the weight fraction of fiber. Moreover the stacking sequence of neem wood plays an important role. As it has a significant impact on the mechanical properties. The results indicated that 0°/0° WPC shows highest mechanical properties as compared to other sequences (90°/90°, 0°/90°, 45°/90°, 45°/45°). The Fourier Transform Infrared Spectroscopy (FTIR) Analysis were carried out to identify chemical compounds both in raw neem wood and neem wood epoxy composite. The microstructure raw/neat neem wood and the interfacial bonding characteristics of neem wood composite investigated using Scanning electron microscopy images.

  11. Mechanical property determination of high conductivity metals and alloys

    NASA Technical Reports Server (NTRS)

    Harrod, D. L.; Vandergrift, E.; France, L.

    1973-01-01

    Pertinent mechanical properties of three high conductivity metals and alloys; namely, vacuum hot pressed grade S-200E beryllium, OFHC copper and beryllium-copper alloy no. 10 were determined. These materials were selected based on their possible use in rocket thrust chamber and nozzle hardware. They were procured in a form and condition similar to that which might be ordered for actual hardware fabrication. The mechanical properties measured include (1) tension and compression stress strain curves at constant strain rate (2) tensile and compressive creep, (3) tensile and compressive stress-relaxation behavior and (4) elastic properties. Tests were conducted over the temperature range of from 75 F to 1600 F. The resulting data is presented in both graphical and tabular form.

  12. Mechanical Properties of Organized Microcomposites Fabricated by Interference Lithography

    NASA Astrophysics Data System (ADS)

    Singamaneni, Srikanth; Chang, Sehoon; Jang, Ji-Hyun; Davis, Whitney; Thomas, Edwin; Tsukruk, Vladimir

    2009-03-01

    We demonstrate that organized, porous, polymer microstructures with continuous open nanoscale pores and sub-micron spacings obtained via interference lithography can be successfully utilized in a highly non-traditional field of ordered microcomposites. Organized microcomposite structures are fabricated by employing two independent strategies, namely, capillary infiltration and in situ polymerization of the rubbery component into the porous glassy microframes. The mechanical properties and ultimate fracture behavior of the single and bicomponent microframes are investigated at different length scales. The ordered single and bi-component microstructures with high degree of control over the microscopic organization of the polymeric phases result in excellent mechanical properties. Combining hard and soft polymer components provides multifunctional materials and coatings with synergetic properties and is frequently utilized for design of advanced polymeric composites.

  13. Improved predictive modeling of white LEDs with accurate luminescence simulation and practical inputs with TracePro opto-mechanical design software

    NASA Astrophysics Data System (ADS)

    Tsao, Chao-hsi; Freniere, Edward R.; Smith, Linda

    2009-02-01

    The use of white LEDs for solid-state lighting to address applications in the automotive, architectural and general illumination markets is just emerging. LEDs promise greater energy efficiency and lower maintenance costs. However, there is a significant amount of design and cost optimization to be done while companies continue to improve semiconductor manufacturing processes and begin to apply more efficient and better color rendering luminescent materials such as phosphor and quantum dot nanomaterials. In the last decade, accurate and predictive opto-mechanical software modeling has enabled adherence to performance, consistency, cost, and aesthetic criteria without the cost and time associated with iterative hardware prototyping. More sophisticated models that include simulation of optical phenomenon, such as luminescence, promise to yield designs that are more predictive - giving design engineers and materials scientists more control over the design process to quickly reach optimum performance, manufacturability, and cost criteria. A design case study is presented where first, a phosphor formulation and excitation source are optimized for a white light. The phosphor formulation, the excitation source and other LED components are optically and mechanically modeled and ray traced. Finally, its performance is analyzed. A blue LED source is characterized by its relative spectral power distribution and angular intensity distribution. YAG:Ce phosphor is characterized by relative absorption, excitation and emission spectra, quantum efficiency and bulk absorption coefficient. Bulk scatter properties are characterized by wavelength dependent scatter coefficients, anisotropy and bulk absorption coefficient.

  14. Mechanical Properties of Nylon Harp Strings

    PubMed Central

    Lynch-Aird, Nicolas; Woodhouse, Jim

    2017-01-01

    Monofilament nylon strings with a range of diameters, commercially marketed as harp strings, have been tested to establish their long-term mechanical properties. Once a string had settled into a desired stress state, the Young’s modulus was measured by a variety of methods that probe different time-scales. The modulus was found to be a strong function of testing frequency and also a strong function of stress. Strings were also subjected to cyclical variations of temperature, allowing various thermal properties to be measured: the coefficient of linear thermal expansion and the thermal sensitivities of tuning, Young’s modulus and density. The results revealed that the particular strings tested are divided into two groups with very different properties: stress-strain behaviour differing by a factor of two and some parametric sensitivities even having the opposite sign. Within each group, correlation studies allowed simple functional fits to be found to the key properties, which have the potential to be used in automated tuning systems for harp strings. PMID:28772858

  15. Investigation on Mechanical Properties of Graphene Oxide reinforced GFRP

    NASA Astrophysics Data System (ADS)

    Arun, G. K.; Sreenivas, Nikhil; Brahma Reddy, Kesari; Sai Krishna Reddy, K.; Shashi Kumar, M. E.; Pramod, R.

    2018-02-01

    Graphene and E-glass fibres individually find a very wide field of applications because of their various mechanical and chemical properties. Recently graphene has attracted both academic and industrial interest because it can produce a dramatic improvement in properties at very low filler content. The primary interest of this venture is to investigate on Graphene reinforced polymer matrix nanocomposites and finding the mechanical properties. The composites were fabricated by Hand Lay Process and have been evaluated by the addition of Graphene with 1, 1.5, 2, 2.5 and 3 by weight% as reinforcement in composites. The theoretical and experimental results validate the increase in properties such as tensile strength, hardness and flexural strength with increase in weight proportions from 1% to 3% of graphene powder. It was observed that the composite material with 2.5% weight fraction of graphene yielded superior properties over other weight percentages. Graphene reinforced polymer matrix nanocomposites finds its major applications in the manufacture of aircraft bodies, ballistic missiles, sporting equipment, marine applications and extraterrestrial ventures.

  16. Manufacturing of hydrogel biomaterials with controlled mechanical properties for tissue engineering applications.

    PubMed

    Vedadghavami, Armin; Minooei, Farnaz; Mohammadi, Mohammad Hossein; Khetani, Sultan; Rezaei Kolahchi, Ahmad; Mashayekhan, Shohreh; Sanati-Nezhad, Amir

    2017-10-15

    Hydrogels have been recognized as crucial biomaterials in the field of tissue engineering, regenerative medicine, and drug delivery applications due to their specific characteristics. These biomaterials benefit from retaining a large amount of water, effective mass transfer, similarity to natural tissues and the ability to form different shapes. However, having relatively poor mechanical properties is a limiting factor associated with hydrogel biomaterials. Controlling the biomechanical properties of hydrogels is of paramount importance. In this work, firstly, mechanical characteristics of hydrogels and methods employed for characterizing these properties are explored. Subsequently, the most common approaches used for tuning mechanical properties of hydrogels including but are not limited to, interpenetrating polymer networks, nanocomposites, self-assembly techniques, and co-polymerization are discussed. The performance of different techniques used for tuning biomechanical properties of hydrogels is further compared. Such techniques involve lithography techniques for replication of tissues with complex mechanical profiles; microfluidic techniques applicable for generating gradients of mechanical properties in hydrogel biomaterials for engineering complex human tissues like intervertebral discs, osteochondral tissues, blood vessels and skin layers; and electrospinning techniques for synthesis of hybrid hydrogels and highly ordered fibers with tunable mechanical and biological properties. We finally discuss future perspectives and challenges for controlling biomimetic hydrogel materials possessing proper biomechanical properties. Hydrogels biomaterials are essential constituting components of engineered tissues with the applications in regenerative medicine and drug delivery. The mechanical properties of hydrogels play crucial roles in regulating the interactions between cells and extracellular matrix and directing the cells phenotype and genotype. Despite

  17. Molecular Simulation of the Free Energy for the Accurate Determination of Phase Transition Properties of Molecular Solids

    NASA Astrophysics Data System (ADS)

    Sellers, Michael; Lisal, Martin; Brennan, John

    2015-06-01

    Investigating the ability of a molecular model to accurately represent a real material is crucial to model development and use. When the model simulates materials in extreme conditions, one such property worth evaluating is the phase transition point. However, phase transitions are often overlooked or approximated because of difficulty or inaccuracy when simulating them. Techniques such as super-heating or super-squeezing a material to induce a phase change suffer from inherent timescale limitations leading to ``over-driving,'' and dual-phase simulations require many long-time runs to seek out what frequently results in an inexact location of phase-coexistence. We present a compilation of methods for the determination of solid-solid and solid-liquid phase transition points through the accurate calculation of the chemical potential. The methods are applied to the Smith-Bharadwaj atomistic potential's representation of cyclotrimethylene trinitramine (RDX) to accurately determine its melting point (Tm) and the alpha to gamma solid phase transition pressure. We also determine Tm for a coarse-grain model of RDX, and compare its value to experiment and atomistic counterpart. All methods are employed via the LAMMPS simulator, resulting in 60-70 simulations that total 30-50 ns. Approved for public release. Distribution is unlimited.

  18. Determining the Mechanical Properties of Lattice Block Structures

    NASA Technical Reports Server (NTRS)

    Wilmoth, Nathan

    2013-01-01

    Lattice block structures and shape memory alloys possess several traits ideal for solving intriguing new engineering problems in industries such as aerospace, military, and transportation. Recent testing at the NASA Glenn Research Center has investigated the material properties of lattice block structures cast from a conventional aerospace titanium alloy as well as lattice block structures cast from nickel-titanium shape memory alloy. The lattice block structures for both materials were sectioned into smaller subelements for tension and compression testing. The results from the cast conventional titanium material showed that the expected mechanical properties were maintained. The shape memory alloy material was found to be extremely brittle from the casting process and only compression testing was completed. Future shape memory alloy lattice block structures will utilize an adjusted material composition that will provide a better quality casting. The testing effort resulted in baseline mechanical property data from the conventional titanium material for comparison to shape memory alloy materials once suitable castings are available.

  19. The Effect of Water Molecules on Mechanical Properties of Bamboo Microfibrils

    NASA Astrophysics Data System (ADS)

    Rahbar, Nima

    Bamboo fibers have higher strength-to-weight ratios than steel and concrete. The unique properties of bamboo fibers come from their natural composite structures that comprise mainly cellulose nanofibrils in a matrix of intertwined hemicellulose and lignin called lignin-carbohydrate complex (LCC). Here, we have utilized atomistic simulations to investigate the mechanical properties and mechanisms of interactions between these materials, in the presence of water molecules. Our results suggest that hemicellulose exhibits better mechanical properties and lignin shows greater tendency to adhere to cellulose nanofibrils. Consequently, the role of hemicellulose found to be enhancing the mechanical properties and lignin found to be providing the strength of bamboo fibers. The abundance of Hbonds in hemicellulose chains is responsible for improving the mechanical behavior of LCC. The strong van der Waals forces between lignin molecules and cellulose nanofibrils is responsible for higher adhesion energy between LCC/cellulose nanofibrils. We also found out that the amorphous regions of cellulose nanofibrils is the weakest interface in bamboo Microfibrils. In presence of water, the elastic modulus of lignin increases at low water content (less than 10 NSF CAREER Grant No. 1261284.

  20. Rheological and mechanical properties of recycled polyethylene films contaminated by biopolymer.

    PubMed

    Gere, D; Czigany, T

    2018-06-01

    Nowadays, with the increasing amount of biopolymers used, it can be expected that biodegradable polymers (e.g. PLA, PBAT) may appear in the petrol-based polymer waste stream. However, their impact on the recycling processes is not known yet; moreover, the properties of the products made from contaminated polymer blends are not easily predictable. Therefore, our goal was to investigate the rheological and mechanical properties of synthetic and biopolymer compounds. We made different compounds from regranulates of mixed polyethylene film waste and original polylactic acid (PLA) by extruison, and injection molded specimens from the compounds. We investigated the rheological properties of the regranulates, and the mechanical properties of the samples. When PLA was added, the viscosity and specific volume of all the blends decreased, and mechanical properties (tensile strength, modulus, and impact strength) changed significantly. Young's modulus increased, while elongation at break and impact strength decreased with the increase of the weight fraction of PLA. Copyright © 2018 Elsevier Ltd. All rights reserved.

  1. Mineral concentration dependent modulation of mechanical properties of bone-inspired bionanocomposite scaffold

    NASA Astrophysics Data System (ADS)

    Biswas, Abhijit; Ovaert, Timothy C.; Slaboch, Constance; Zhao, He; Bayer, Ilker S.; Biris, Alexandru S.; Wang, Tao

    2011-07-01

    We demonstrate tunable mechanical properties of bone-inspired bionanocomposite scaffolds while maintaining the required viscoelasticity. Mechanical properties such as hardness and elastic modulus of the bionanocomposite scaffolds were controlled by varying mineral concentrations of the bioscaffold. In particular, higher calcium and oxygen contents in the bioscaffold resulted in a significant enhancement in hardness and modulus of the bionanocomposite. Moreover, the phosphorous content appeared to be a determining factor in the hardness and mechanical properties of the bionanocomposites. These results open up the possibility of designing new engineered biocompatible nanoscaffolds with desired and tunable biomimetic functions and biomechanical properties with significant potential for advanced bone tissue engineering platforms and bone substitutes.

  2. Mechanical Properties in a Bamboo Fiber/PBS Biodegradable Composite

    NASA Astrophysics Data System (ADS)

    Ogihara, Shinji; Okada, Akihisa; Kobayashi, Satoshi

    In recent years, biodegradable plastics which have low effect on environment have been developed. However, many of them have lower mechanical properties than conventional engineering plastics. Reinforcing them with a natural fiber is one of reinforcing methods without a loss of their biodegradability. In the present study, we use a bamboo fiber as the reinforcement and polybutylenesuccinate (PBS) as the matrix. We fabricate long fiber unidirectional composites and cross-ply laminate with different fiber weight fractions (10, 20, 30, 40 and 50wt%). We conduct tensile tests to evaluate the mechanical properties of these composites. In addition, we measure bamboo fiber strength distribution. We discuss the experimentally-obtained properties based on the mechanical properties of the constituent materials. Young's modulus and tensile strength in unidirectional composite and cross-ply laminate increase with increasing fiber weight fraction. However, the strain at fracture showed decreasing tendency. Young's modulus in fiber and fiber transverse directions are predictable by the rules of mixture. Tensile strength in fiber direction is lower than Curtin's prediction of strength which considers distribution of fiber strength. Young's modulus in cross-ply laminate is predictable by the laminate theory. However, analytical prediction of Poisson's ratio in cross-ply laminate by the laminate theory is lower than the experimental results.

  3. Structure-property relation and relevance of beam theories for microtubules: a coupled molecular and continuum mechanics study.

    PubMed

    Li, Si; Wang, Chengyuan; Nithiarasu, Perumal

    2018-04-01

    Quasi-one-dimensional microtubules (MTs) in cells enjoy high axial rigidity but large transverse flexibility due to the inter-protofilament (PF) sliding. This study aims to explore the structure-property relation for MTs and examine the relevance of the beam theories to their unique features. A molecular structural mechanics (MSM) model was used to identify the origin of the inter-PF sliding and its role in bending and vibration of MTs. The beam models were then fitted to the MSM to reveal how they cope with the distinct mechanical responses induced by the inter-PF sliding. Clear evidence showed that the inter-PF sliding is due to the soft inter-PF bonds and leads to the length-dependent bending stiffness. The Euler beam theory is found to adequately describe MT deformation when the inter-PF sliding is largely prohibited. Nevertheless, neither shear deformation nor the nonlocal effect considered in the 'more accurate' beam theories can fully capture the effect of the inter-PF sliding. This reflects the distinct deformation mechanisms between an MT and its equivalent continuous body.

  4. Structural characterization and mechanical properties of polypropylene reinforced natural fibers

    NASA Astrophysics Data System (ADS)

    Karim, M. A. A.; Zaman, I.; Rozlan, S. A. M.; Berhanuddin, N. I. C.; Manshoor, B.; Mustapha, M. S.; Khalid, A.; Chan, S. W.

    2017-10-01

    Recently the development of natural fiber composite instead of synthetics fiber has lead to eco-friendly product manufacturing to meet various applications in the field of automotive, construction and manufacturing. The use of natural fibers offer an alternative to the reinforcing fibers because of their good mechanical properties, low density, renewability, and biodegradability. In this present research, the effects of maleic anhydride polypropylene (MAPP) on the mechanical properties and material characterization behaviour of kenaf fiber and coir fiber reinforced polypropylene were investigated. Different fractions of composites with 10wt%, 20wt% and 30wt% fiber content were prepared by using brabender mixer at 190°C. The 3wt% MAPP was added during the mixing. The composites were subsequently molded with injection molding to prepare the test specimens. The mechanical properties of the samples were investigated according to ISO 527 to determine the tensile strength and modulus. These results were also confirmed by the SEM machine observations of fracture surface of composites and FTIR analysis of the chemical structure. As the results, the presence of MAPP helps increasing the mechanical properties of both fibers and 30wt% kenaf fiber with 3wt% MAPP gives the best result compare to others.

  5. Microstructure and Mechanical Properties of Graphene-Reinforced Titanium Matrix/Nano-Hydroxyapatite Nanocomposites

    PubMed Central

    Li, Feng; Shao, Zhenyi; Zhu, Degui; Zhu, Minhao

    2018-01-01

    Biomaterial composites made of titanium and hydroxyapatite (HA) powder are among the most important biomedicalmaterials due to their good mechanical properties and biocompatibility. In this work, graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites were prepared by vacuum hot-pressing sintering. The microstructure and mechanical properties of graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were systematically investigated. Microstructures of the nanocomposites were examined by X-ray diffraction (XRD), back scattered electron imaging (BSE), scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS), electron probe microanalyzer (EPMA), and transmission electron microscope (TEM). The mechanical properties were determined from microhardness, shear strength, and compressive strength. Results showed that during the high-temperature sintering process, complex chemical reactions occurred, resulting in new phases of nucleation such as Ca3(PO4)2, TixPy, and Ti3O.The new phases, which easily dropped off under the action of external force, could hinder the densification of sintering and increase the brittleness of the nanocomposites. Results demonstrated that graphene had an impact on the microstructure and mechanical properties of the nanocomposites. Based on the mechanical properties and microstructure of the nanocomposites, the strengthening and fracture mechanisms of the graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were analyzed. PMID:29659504

  6. Microstructure and Mechanical Properties of Graphene-Reinforced Titanium Matrix/Nano-Hydroxyapatite Nanocomposites.

    PubMed

    Li, Feng; Jiang, Xiaosong; Shao, Zhenyi; Zhu, Degui; Zhu, Minhao

    2018-04-16

    Biomaterial composites made of titanium and hydroxyapatite (HA) powder are among the most important biomedicalmaterials due to their good mechanical properties and biocompatibility. In this work, graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites were prepared by vacuum hot-pressing sintering. The microstructure and mechanical properties of graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were systematically investigated. Microstructures of the nanocomposites were examined by X-ray diffraction (XRD), back scattered electron imaging (BSE), scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS), electron probe microanalyzer (EPMA), and transmission electron microscope (TEM). The mechanical properties were determined from microhardness, shear strength, and compressive strength. Results showed that during the high-temperature sintering process, complex chemical reactions occurred, resulting in new phases of nucleation such as Ca₃(PO₄)₂, Ti x P y , and Ti₃O.The new phases, which easily dropped off under the action of external force, could hinder the densification of sintering and increase the brittleness of the nanocomposites. Results demonstrated that graphene had an impact on the microstructure and mechanical properties of the nanocomposites. Based on the mechanical properties and microstructure of the nanocomposites, the strengthening and fracture mechanisms of the graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were analyzed.

  7. Effect of thermo-mechanical treatments on the microstructure and mechanical properties of an ODS ferritic steel

    NASA Astrophysics Data System (ADS)

    Oksiuta, Z.; Mueller, P.; Spätig, P.; Baluc, N.

    2011-05-01

    The Fe-14Cr-2W-0.3Ti-0.3Y 2O 3 oxide dispersion strengthened (ODS) reduced activation ferritic (RAF) steel was fabricated by mechanical alloying of a pre-alloyed, gas atomised powder with yttria nano-particles, followed by hot isostatic pressing and thermo-mechanical treatments (TMTs). Two kinds of TMT were applied: (i) hot pressing, or (ii) hot rolling, both followed by annealing in vacuum at 850 °C. The use of a thermo-mechanical treatment was found to yield strong improvement in the microstructure and mechanical properties of the ODS RAF steel. In particular, hot pressing leads to microstructure refinement, equiaxed grains without texture, and an improvement in Charpy impact properties, especially in terms of the upper shelf energy (about 4.5 J). Hot rolling leads to elongated grains in the rolling direction, with a grain size ratio of 6:1, higher tensile strength and reasonable ductility up to 750 °C, and better Charpy impact properties, especially in terms of the ductile-to-brittle transition temperature (about 55 °C).

  8. Mechanical property quantification of endothelial cells using scanning acoustic microscopy

    NASA Astrophysics Data System (ADS)

    Shelke, A.; Brand, S.; Kundu, T.; Bereiter-Hahn, J.; Blase, C.

    2012-04-01

    The mechanical properties of cells reflect dynamic changes of cellular organization which occur during physiologic activities like cell movement, cell volume regulation or cell division. Thus the study of cell mechanical properties can yield important information for understanding these physiologic activities. Endothelial cells form the thin inner lining of blood vessels in the cardiovascular system and are thus exposed to shear stress as well as tensile stress caused by the pulsatile blood flow. Endothelial dysfunction might occur due to reduced resistance to mechanical stress and is an initial step in the development of cardiovascular disease like, e.g., atherosclerosis. Therefore we investigated the mechanical properties of primary human endothelial cells (HUVEC) of different age using scanning acoustic microscopy at 1.2 GHz. The HUVECs are classified as young (tD < 90 h) and old (tD > 90 h) cells depending upon the generation time for the population doubling of the culture (tD). Longitudinal sound velocity and geometrical properties of cells (thickness) were determined using the material signature curve V(z) method for variable culture condition along spatial coordinates. The plane wave technique with normal incidence is assumed to solve two-dimensional wave equation. The size of the cells is modeled using multilayered (solid-fluid) system. The propagation of transversal wave and surface acoustic wave are neglected in soft matter analysis. The biomechanical properties of HUVEC cells are quantified in an age dependent manner.

  9. Fatigue and mechanical properties of nickel-titanium endodontic instruments.

    PubMed

    Kuhn, Grégoire; Jordan, Laurence

    2002-10-01

    Shape memory alloys are increasingly used in superelastic conditions under complex cyclic deformation situations. In these applications, it is very difficult to predict the service life based on the theoretical law. In the present work, fatigue properties of NiTi engine-driven rotary files have been characterized by using differential scanning calorimetry (DSC) and mechanical testing (bending). The DSC technique was used to measure precise transformation. The degree of deformation by bending was studied with combined DSC and mechanical property measurements. In these cold-worked files, the high dislocation density influences the reorientation processes and the crack growth. Some thermal treatments are involved in promoting some changes in the mechanical properties and transformation characteristics. Annealing around 400 degrees C shows good results; the recovery allows a compromise between an adequate density for the R-Phase germination and a low density to limit the brittleness of these instruments. In clinical usage, it is important to consider different canal shapes. It could be proposed that only few cycles of use is safe for very curved canals but to follow the manufacturer's advise for straight canals.

  10. In vivo quantification of spatially-varying mechanical properties in developing tissues

    PubMed Central

    Serwane, Friedhelm; Mongera, Alessandro; Rowghanian, Payam; Kealhofer, David A.; Lucio, Adam A.; Hockenbery, Zachary M.; Campàs, Otger

    2017-01-01

    It is generally believed that the mechanical properties of the cellular microenvironment and their spatiotemporal variations play a central role in sculpting embryonic tissues, maintaining organ architecture and controlling cell behavior, including cell differentiation. However, no direct in vivo and in situ measurement of mechanical properties within developing 3D tissues and organs has been performed yet. Here we introduce a technique that employs biocompatible ferrofluid microdroplets as local mechanical actuators and allows quantitative spatiotemporal measurements of mechanical properties in vivo. Using this technique, we show that vertebrate body elongation entails spatially-varying tissue mechanics along the anteroposterior axis. Specifically, we find that the zebrafish tailbud is viscoelastic (elastic below a few seconds and fluid after just one minute) and displays decreasing stiffness and increasing fluidity towards its posterior elongating region. This method opens new avenues to study mechanobiology in vivo, both in embryogenesis and in disease processes, including cancer. PMID:27918540

  11. Mechanical Properties of Nanostructured Materials Determined Through Molecular Modeling Techniques

    NASA Technical Reports Server (NTRS)

    Clancy, Thomas C.; Gates, Thomas S.

    2005-01-01

    The potential for gains in material properties over conventional materials has motivated an effort to develop novel nanostructured materials for aerospace applications. These novel materials typically consist of a polymer matrix reinforced with particles on the nanometer length scale. In this study, molecular modeling is used to construct fully atomistic models of a carbon nanotube embedded in an epoxy polymer matrix. Functionalization of the nanotube which consists of the introduction of direct chemical bonding between the polymer matrix and the nanotube, hence providing a load transfer mechanism, is systematically varied. The relative effectiveness of functionalization in a nanostructured material may depend on a variety of factors related to the details of the chemical bonding and the polymer structure at the nanotube-polymer interface. The objective of this modeling is to determine what influence the details of functionalization of the carbon nanotube with the polymer matrix has on the resulting mechanical properties. By considering a range of degree of functionalization, the structure-property relationships of these materials is examined and mechanical properties of these models are calculated using standard techniques.

  12. Mechanical properties of DNA origami nanoassemblies are determined by Holliday junction mechanophores

    PubMed Central

    Shrestha, Prakash; Emura, Tomoko; Koirala, Deepak; Cui, Yunxi; Hidaka, Kumi; Maximuck, William J; Endo, Masayuki; Sugiyama, Hiroshi; Mao, Hanbin

    2016-01-01

    DNA nanoassemblies have demonstrated wide applications in various fields including nanomaterials, drug delivery and biosensing. In DNA origami, single-stranded DNA template is shaped into desired nanostructure by DNA staples that form Holliday junctions with the template. Limited by current methodologies, however, mechanical properties of DNA origami structures have not been adequately characterized, which hinders further applications of these materials. Using laser tweezers, here, we have described two mechanical properties of DNA nanoassemblies represented by DNA nanotubes, DNA nanopyramids and DNA nanotiles. First, mechanical stability of DNA origami structures is determined by the effective density of Holliday junctions along a particular stress direction. Second, mechanical isomerization observed between two conformations of DNA nanotubes at 10–35 pN has been ascribed to the collective actions of individual Holliday junctions, which are only possible in DNA origami with rotational symmetric arrangements of Holliday junctions, such as those in DNA nanotubes. Our results indicate that Holliday junctions control mechanical behaviors of DNA nanoassemblies. Therefore, they can be considered as ‘mechanophores’ that sustain mechanical properties of origami nanoassemblies. The mechanical properties observed here provide insights for designing better DNA nanostructures. In addition, the unprecedented mechanical isomerization process brings new strategies for the development of nano-sensors and actuators. PMID:27387283

  13. Investigation of the influence of the composition on mechanical properties poly(glycolide-DL-lactide)

    NASA Astrophysics Data System (ADS)

    Baikin, A. S.; Sevostyanov, M. A.; Nasakina, E. O.; Sergienko, K. V.; Kaplan, M. A.; Konushkin, S. V.; Kolmakova, A. A.; Yakubov, A. D.; Kolmakov, A. G.

    2018-04-01

    In this paper we describe the creation of films from poly (glycolide-DL-lactide). Studied the mechanical properties of developed polymer films of poly (glycolide-DL-lactide). The effect of the molecular weight of poly (glycolide-DL-lactide) on the mechanical properties of the resulting polymer films is shown. The dependence of the mechanical properties of poly (glycolide-DL-lactide) films on the polymer concentration in chloroform was studied. The possibility of creating biodegradable films with specified mechanical properties is shown.

  14. Mechanical property characterization of bilayered tablets using nondestructive air-coupled acoustics.

    PubMed

    Akseli, Ilgaz; Dey, Dipankar; Cetinkaya, Cetin

    2010-03-01

    A noncontact/nondestructive air-coupled acoustic technique to be potentially used in mechanical property determination of bilayer tablets is presented. In the reported experiments, a bilayer tablet is vibrated via an acoustic field of an air-coupled transducer in a frequency range sufficiently high to excite several vibrational modes (harmonics) of the tablet. The tablet vibrational transient responses at a number of measurement points on the tablet are acquired by a laser vibrometer in a noncontact manner. An iterative computational procedure based on the finite element method is utilized to extract the Young's modulus, the Poisson's ratio, and the mass density values of each layer material of a bilayer tablet from a subset of the measured resonance frequencies. For verification purposes, a contact ultrasonic technique based on the time-of-flight data of the longitudinal (pressure) and transverse (shear) acoustic waves in each layer of a bilayer tablet is also utilized. The extracted mechanical properties from the air-coupled acoustic data agree well with those determined from the contact ultrasonic measurements. The mechanical properties of solid oral dosage forms have been shown to impact its mechanical integrity, disintegration profile and the release rate of the drug in the digestive tract, thus potentially affecting its therapeutic response. The presented nondestructive technique provides greater insight into the mechanical properties of the bilayer tablets and has the potential to identify quality and performance problems related to the mechanical properties of the bilayer tablets early on the production process and, consequently, reduce associated cost and material waste.

  15. Mechanical properties and material characterization of polysialate structural composites

    NASA Astrophysics Data System (ADS)

    Foden, Andrew James

    One of the major concerns in using Fiber Reinforced Composites in applications that are subjected to fire is their resistance to high temperature. Some of the fabrics used in FRC, such as carbon, are fire resistant. However, almost all the resins used cannot withstand temperatures higher than 200°C. This dissertation deals with the development and use of a potassium aluminosilicate (GEOPOLYMER) resin that is inorganic and can sustain more than 1000°C. The results presented include the mechanical properties of the unreinforced polysialate matrix in tension, flexure, and compression as well as the strain capacities and surface energy. The mechanical properties of the matrix reinforced with several different fabrics were obtained in flexure, tension, compression and shear. The strength and stiffness of the composite was evaluated for each loading condition. Tests were conducted on unexposed samples as well as samples exposed to temperatures from 200 to 1000°C. Fatigue properties were determined using flexural loading. A study of the effect of several processing variables on the properties of the composite was undertaken to determine the optimum procedure for manufacturing composite plates. The processing variables studied were the curing temperature and pressure, and the post cure drying time required to remove any residual water. The optimum manufacturing conditions were determined using the void content, density, fiber volume fraction, and flexural strength. Analytical models are presented based on both micro and macro mechanical analysis of the composite. Classic laminate theory is used to evaluate the state of the composite as it is being loaded to determine the failure mechanisms. Several failure criteria theories are considered. The analysis is then used to explain the mechanical behavior of the composite that was observed during the experimental study.

  16. Predicting the Highly Nonlinear Mechanical Properties of Polymeric Materials

    NASA Astrophysics Data System (ADS)

    Porter, David

    2009-06-01

    Over the past few years, we have developed models that calculate the highly nonlinear mechanical properties of polymers as a function of temperature, strain and strain rate from their molecular and morphological structure. A review of these models is presented here, with emphasis on combining the fundamental aspects of molecular physics that dictate these properties and the pragmatic need to make realistic predictions for our customers; the designer of new materials and the engineers who use these materials. The models calculate the highly nonlinear mechanical properties of polymers as a function of temperature, strain and strain rate from their molecular structure. The model is based upon the premise that mechanical properties are a direct consequence of energy stored and energy dissipated during deformation of a material. This premise is transformed into a consistent set of structure-property relations for the equation of state, EoS, and the engineering constitutive relations in a polymer by quantifying energy storage and loss at the molecular level of interactions between characteristic groups of atoms in a polymer. These relations are derived from a simple volumetric mean field Lennard-Jones potential function for the potential energy of intermolecular interactions in a polymer. First, properties such as temperature-volume relations and glass transition temperature are calculated directly from the potential function. Then, the `shock' EoS is derived simply by differentiating the potential function with respect to volume, assuming that the molecules cannot relax in the time scales of the deformation. The energy components are then used to predict the dynamic mechanical spectrum of a polymer in terms of temperature and rate. This can be transformed directly into the highly nonlinear stress-strain relations through yield. The constitutive relations are formulated as a set of analytical equations that predict properties directly in terms of a small set of

  17. Metallurgical Mechanisms Controlling Mechanical Properties of Aluminum Alloy 2219 Produced by Electron Beam Freeform Fabrication

    NASA Technical Reports Server (NTRS)

    Domack, Marcia S.; Tainger, Karen M.

    2006-01-01

    The electron beam freeform fabrication (EBF3) layer-additive manufacturing process has been developed to directly fabricate complex geometry components. EBF3 introduces metal wire into a molten pool created on the surface of a substrate by a focused electron beam. Part geometry is achieved by translating the substrate with respect to the beam to build the part one layer at a time. Tensile properties demonstrated for electron beam deposited aluminum and titanium alloys are comparable to wrought products, although the microstructures of the deposits exhibit cast features. Understanding the metallurgical mechanisms controlling mechanical properties is essential to maximizing application of the EBF3 process. Tensile mechanical properties and microstructures were examined for aluminum alloy 2219 fabricated over a range of EBF3 process variables. Unique microstructures were observed within the deposited layers and at interlayer boundaries, which varied within the deposit height due to microstructural evolution associated with the complex thermal history experienced during subsequent layer deposition. Microstructures exhibited irregularly shaped grains with interior dendritic structures, described based on overall grain size, morphology, distribution, and dendrite spacing, and were correlated with deposition parameters. Fracture features were compared with microstructural elements to define fracture paths and aid in definition of basic processing-microstructure-property correlations.

  18. Cumulative atomic multipole moments complement any atomic charge model to obtain more accurate electrostatic properties

    NASA Technical Reports Server (NTRS)

    Sokalski, W. A.; Shibata, M.; Ornstein, R. L.; Rein, R.

    1992-01-01

    The quality of several atomic charge models based on different definitions has been analyzed using cumulative atomic multipole moments (CAMM). This formalism can generate higher atomic moments starting from any atomic charges, while preserving the corresponding molecular moments. The atomic charge contribution to the higher molecular moments, as well as to the electrostatic potentials, has been examined for CO and HCN molecules at several different levels of theory. The results clearly show that the electrostatic potential obtained from CAMM expansion is convergent up to R-5 term for all atomic charge models used. This illustrates that higher atomic moments can be used to supplement any atomic charge model to obtain more accurate description of electrostatic properties.

  19. Porcine bladder acellular matrix (ACM): protein expression, mechanical properties.

    PubMed

    Farhat, Walid A; Chen, Jun; Haig, Jennifer; Antoon, Roula; Litman, Jessica; Sherman, Christopher; Derwin, Kathleen; Yeger, Herman

    2008-06-01

    Experimentally, porcine bladder acellular matrix (ACM) that mimics extracellular matrix has excellent potential as a bladder substitute. Herein we investigated the spatial localization and expression of different key cellular and extracellular proteins in the ACM; furthermore, we evaluated the inherent mechanical properties of the resultant ACM prior to implantation. Using a proprietary decellularization method, the DNA contents in both ACM and normal bladder were measured; in addition we used immunohistochemistry and western blots to quantify and localize the different cellular and extracellular components, and finally the mechanical testing was performed using a uniaxial mechanical testing machine. The mean DNA content in the ACM was significantly lower in the ACM compared to the bladder. Furthermore, the immunohistochemical and western blot analyses showed that collagen I and IV were preserved in the ACM, but possibly denatured collagen III in the ACM. Furthermore, elastin, laminin and fibronectin were mildly reduced in the ACM. Although the ACM did not exhibit nucleated cells, residual cellular components (actin, myosin, vimentin and others) were still present. There was, on the other hand, no significant difference in the mean stiffness between the ACM and the bladder. Although our decellularization method is effective in removing nuclear material from the bladder while maintaining its inherent mechanical properties, further work is mandatory to determine whether these residual DNA and cellular remnants would lead to any immune reaction, or if the mechanical properties of the ACM are preserved upon implantation and cellularization.

  20. Mechanical properties of single electrospun drug-encapsulated nanofibres

    PubMed Central

    Chew, Sing Yian; Hufnagel, Todd C; Lim, Chwee Teck; Leong, Kam W

    2008-01-01

    The mechanical and structural properties of a surface play an important role in determining the morphology of attached cells, and ultimately their cellular functions. As such, mechanical and structural integrity are important design parameters for a tissue scaffold. Electrospun fibrous meshes are widely used in tissue engineering. When in contact with electrospun scaffolds, cells see the individual micro- or nanofibres as their immediate microenvironment. In this study, tensile testing of single electrospun nanofibres composed of poly(ε-caprolactone) (PCL), and its copolymer, poly(caprolactone-co-ethyl ethylene phosphate) (PCLEEP), revealed a size effect in the Young's modulus, E, and tensile strength, σT. Both strength and stiffness increase as the fibre diameter decreases from bulk (∼5 μm) into the nanometre region (200–300 nm). In particular, E and σT of individual PCL nanofibres were at least two-fold and an order of magnitude higher than that of PCL film, respectively. PCL films were observed to have more pronounced crystallographic texture than the nanofibres; however no difference in crystalline fraction, perfection, or texture was detected among the various fibres. When drugs were encapsulated into single PCLEEP fibres, mechanical properties were enhanced with 1–20 wt% of loaded retinoic acid, but weakened by 10–20 wt% of encapsulated bovine serum albumin. This understanding of the effect of size and drug and protein encapsulation on the mechanical properties of electrospun fibres may help in the optimization of tissue scaffold design that combines biochemical and biomechanical cues for tissue regeneration. PMID:19079553

  1. Damage Mechanisms and Mechanical Properties of High-Strength Multiphase Steels

    PubMed Central

    Heibel, Sebastian; Dettinger, Thomas; Nester, Winfried; Tekkaya, A. Erman

    2018-01-01

    The usage of high-strength steels for structural components and reinforcement parts is inevitable for modern car-body manufacture in reaching lightweight design as well as increasing passive safety. Depending on their microstructure these steels show differing damage mechanisms and various mechanical properties which cannot be classified comprehensively via classical uniaxial tensile testing. In this research, damage initiation, evolution and final material failure are characterized for commercially produced complex-phase (CP) and dual-phase (DP) steels in a strength range between 600 and 1000 MPa. Based on these investigations CP steels with their homogeneous microstructure are characterized as damage tolerant and hence less edge-crack sensitive than DP steels. As final fracture occurs after a combination of ductile damage evolution and local shear band localization in ferrite grains at a characteristic thickness strain, this strain measure is introduced as a new parameter for local formability. In terms of global formability DP steels display advantages because of their microstructural composition of soft ferrite matrix including hard martensite particles. Combining true uniform elongation as a measure for global formability with the true thickness strain at fracture for local formability the mechanical material response can be assessed on basis of uniaxial tensile testing incorporating all microstructural characteristics on a macroscopic scale. Based on these findings a new classification scheme for the recently developed high-strength multiphase steels with significantly better formability resulting of complex underlying microstructures is introduced. The scheme overcomes the steel designations using microstructural concepts, which provide no information about design and production properties. PMID:29747417

  2. Damage Mechanisms and Mechanical Properties of High-Strength Multiphase Steels.

    PubMed

    Heibel, Sebastian; Dettinger, Thomas; Nester, Winfried; Clausmeyer, Till; Tekkaya, A Erman

    2018-05-09

    The usage of high-strength steels for structural components and reinforcement parts is inevitable for modern car-body manufacture in reaching lightweight design as well as increasing passive safety. Depending on their microstructure these steels show differing damage mechanisms and various mechanical properties which cannot be classified comprehensively via classical uniaxial tensile testing. In this research, damage initiation, evolution and final material failure are characterized for commercially produced complex-phase (CP) and dual-phase (DP) steels in a strength range between 600 and 1000 MPa. Based on these investigations CP steels with their homogeneous microstructure are characterized as damage tolerant and hence less edge-crack sensitive than DP steels. As final fracture occurs after a combination of ductile damage evolution and local shear band localization in ferrite grains at a characteristic thickness strain, this strain measure is introduced as a new parameter for local formability. In terms of global formability DP steels display advantages because of their microstructural composition of soft ferrite matrix including hard martensite particles. Combining true uniform elongation as a measure for global formability with the true thickness strain at fracture for local formability the mechanical material response can be assessed on basis of uniaxial tensile testing incorporating all microstructural characteristics on a macroscopic scale. Based on these findings a new classification scheme for the recently developed high-strength multiphase steels with significantly better formability resulting of complex underlying microstructures is introduced. The scheme overcomes the steel designations using microstructural concepts, which provide no information about design and production properties.

  3. Thermally Sprayed High Temperature Sandwich Structures: Physical Properties and Mechanical Performance

    NASA Astrophysics Data System (ADS)

    Salavati, Saeid

    Metallic foam core sandwich structures have been of particular interest for engineering applications in recent decades due to their unique physical and mechanical properties. One of the potential applications of open pore metallic foam core sandwich structures is in heat exchangers. An investigation of sandwich structures fabricated from materials suitable for application at high temperatures and in corrosive environments was undertaken in this project. A novel method for fabrication of metallic foam core sandwich structures is thermal spray deposition of the faces on the prepared surfaces of the metallic foam substrate. The objective of the current study was to optimize the twin wire arc spray process parameters for the deposition of alloy 625 faces with controllable porosity content on the nickel foam substrate, and to characterize the physical and mechanical properties of the sandwich structure. The experimental investigations consisted of microstructural evaluation of the skin material and the foam substrate, investigation of the effect of alloying on the mechanical and thermal properties of the nickel foam, optimization of the grit-blasting and arc spray processes, observation of mechanical properties of the alloy 625 deposit by tensile testing and evaluation of the overall mechanical properties of the sandwich structure under flexural loading condition. The optimization of arc spraying process parameters allowed deposition of alloy 625 faces with a porosity of less than 4% for heat exchanger applications. Modification of the arc spraying process by co-deposition of polyester powder enabled 20% porosity to be obtained in the deposited faces for heat shield applications with film cooling. The effects of nickel foam alloying and heat treatment on the flexural rigidity of the sandwich structures were investigated and compared with as-received foam and as-fabricated sandwich structures. Available analytical models were employed to describe the effect of

  4. Mechanical properties of nanodiamond-reinforced hydroxyapatite composite coatings deposited by suspension plasma spraying

    NASA Astrophysics Data System (ADS)

    Chen, Xiuyong; Zhang, Botao; Gong, Yongfeng; Zhou, Ping; Li, Hua

    2018-05-01

    Hydroxyapatite (HA) coatings suffer from poor mechanical properties, which can be enhanced via incorporation of secondary bioinert reinforcement material. Nanodiamond (ND) possesses excellent mechanical properties to play the role as reinforcement for improving the mechanical properties of brittle HA bioceramic coatings. The major persistent challenge yet is the development of proper deposition techniques for fabricating the ND reinforced HA coatings. In this study, we present a novel deposition approach by plasma spraying the mixtures of ND suspension and micron-sized HA powder feedstock. The effect of ND reinforcement on the microstructure and the mechanical properties of the coatings such as hardness, adhesive strength and friction coefficient were examined. The results showed that the ND-reinforced HA coatings display lower porosity, fewer unmelted particles and uniform microstructure, in turn leading to significantly enhanced mechanical properties. The study presented a promising approach to fabricate ND-reinforced HA composite coatings on metal-based medical implants for potential clinical application.

  5. Effect of alkaline treatment on mechanical properties of kenaf fiber reinforced polyester composites

    NASA Astrophysics Data System (ADS)

    Reddy, Bijjam Ramgopal; Dhoria, Sneha H.

    2018-04-01

    This paper focuses on the study of the effect of chemical treatment on mechanical properties such as tensile, flexural and impact properties of kenaf fiber reinforced polyester composites. Adhesion between the fiber and polymer is one of factors affecting the mechanical properties of composites. In order to increase the adhesion, the fibers are chemically treated with 5% of sodium hydroxide (NaOH) solution. The composite specimens are prepared in both untreated and treated forms of kenaf fibers with five levels of fiber volume fractions. The specimens are prepared according to ASTM standards. Mechanical tests such as tensile, flexural and impact are conducted to determine ultimate tensile strength, bending strength and impact strength of composites. The effect of change in volume fraction on the mechanical properties of the composites is studied for both untreated (raw) and chemically treated kenaf fibers. It has been found that the composites made of chemically treated fibers have good mechanical properties compared to untreated fibers.

  6. Assessment of structural, thermal, and mechanical properties of portlandite through molecular dynamics simulations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hajilar, Shahin, E-mail: shajilar@iastate.edu; Shafei, Behrouz, E-mail: shafei@iastate.edu

    The structural, thermal, and mechanical properties of portlandite, the primary solid phase of ordinary hydrated cement paste, are investigated using the molecular dynamics method. To understand the effects of temperature on the structural properties of portlandite, the coefficients of thermal expansion of portlandite are determined in the current study and validated with what reported from the experimental tests. The atomic structure of portlandite equilibrated at various temperatures is then subjected to uniaxial tensile strains in the three orthogonal directions and the stress-strain curves are developed. Based on the obtained results, the effect of the direction of straining on the mechanicalmore » properties of portlandite is investigated in detail. Structural damage analysis is performed to reveal the failure mechanisms in different directions. The energies of the fractured surfaces are calculated in different directions and compared to those of the ideal surfaces available in the literature. The key mechanical properties, including tensile strength, Young's modulus, and fracture strain, are extracted from the stress-strain curves. The sensitivity of the obtained mechanical properties to temperature and strain rate is then explored in a systematic way. This leads to valuable information on how the structural and mechanical properties of portlandite are affected under various exposure conditions and loading rates. - Graphical abstract: Fracture mechanism of portlandite under uniaxial strain in the z-direction. - Highlights: • The structural, thermal, and mechanical properties of portlandite are investigated. • The coefficients of thermal expansion are determined. • The stress-strain relationships are studied in three orthogonal directions. • The effects of temperature and strain rate on mechanical properties are examined. • The plastic energy required for fracture in the crystalline structure is reported.« less

  7. Determination of prestress and elastic properties of virus capsids

    NASA Astrophysics Data System (ADS)

    Aggarwal, Ankush

    2018-03-01

    Virus capsids are protein shells that protect the virus genome, and determination of their mechanical properties has been a topic of interest because of their potential use in nanotechnology and therapeutics. It has been demonstrated that stresses exist in virus capsids, even in their equilibrium state, due to their construction. These stresses, termed "prestresses" in this study, closely affect the capsid's mechanical behavior. Three methods—shape-based metric, atomic force microscope indentation, and molecular dynamics—have been proposed to determine the capsid elastic properties without fully accounting for prestresses. In this paper, we theoretically analyze the three methods used for mechanical characterization of virus capsids and numerically investigate how prestresses affect the capsid's mechanical properties. We consolidate all the results and propose that by using these techniques collectively, it is possible to accurately determine both the mechanical properties and prestresses in capsids.

  8. Measurement of Mechanical Properties of Cantilever Shaped Materials

    PubMed Central

    Finot, Eric; Passian, Ali; Thundat, Thomas

    2008-01-01

    Microcantilevers were first introduced as imaging probes in Atomic Force Microscopy (AFM) due to their extremely high sensitivity in measuring surface forces. The versatility of these probes, however, allows the sensing and measurement of a host of mechanical properties of various materials. Sensor parameters such as resonance frequency, quality factor, amplitude of vibration and bending due to a differential stress can all be simultaneously determined for a cantilever. When measuring the mechanical properties of materials, identifying and discerning the most influential parameters responsible for the observed changes in the cantilever response are important. We will, therefore, discuss the effects of various force fields such as those induced by mass loading, residual stress, internal friction of the material, and other changes in the mechanical properties of the microcantilevers. Methods to measure variations in temperature, pressure, or molecular adsorption of water molecules are also discussed. Often these effects occur simultaneously, increasing the number of parameters that need to be concurrently measured to ensure the reliability of the sensors. We therefore systematically investigate the geometric and environmental effects on cantilever measurements including the chemical nature of the underlying interactions. To address the geometric effects we have considered cantilevers with a rectangular or circular cross section. The chemical nature is addressed by using cantilevers fabricated with metals and/or dielectrics. Selective chemical etching, swelling or changes in Young's modulus of the surface were investigated by means of polymeric and inorganic coatings. Finally to address the effect of the environment in which the cantilever operates, the Knudsen number was determined to characterize the molecule-cantilever collisions. Also bimaterial cantilevers with high thermal sensitivity were used to discern the effect of temperature variations. When appropriate

  9. Ultrasonic evaluation of the physical and mechanical properties of granites.

    PubMed

    Vasconcelos, G; Lourenço, P B; Alves, C A S; Pamplona, J

    2008-09-01

    Masonry is the oldest building material that survived until today, being used all over the world and being present in the most impressive historical structures as an evidence of spirit of enterprise of ancient cultures. Conservation, rehabilitation and strengthening of the built heritage and protection of human lives are clear demands of modern societies. In this process, the use of nondestructive methods has become much common in the diagnosis of structural integrity of masonry elements. With respect to the evaluation of the stone condition, the ultrasonic pulse velocity is a simple and economical tool. Thus, the central issue of the present paper concerns the evaluation of the suitability of the ultrasonic pulse velocity method for describing the mechanical and physical properties of granites (range size between 0.1-4.0 mm and 0.3-16.5 mm) and for the assessment of its weathering state. The mechanical properties encompass the compressive and tensile strength and modulus of elasticity, and the physical properties include the density and porosity. For this purpose, measurements of the longitudinal ultrasonic pulse velocity with distinct natural frequency of the transducers were carried out on specimens with different size and shape. A discussion of the factors that induce variations on the ultrasonic velocity is also provided. Additionally, statistical correlations between ultrasonic pulse velocity and mechanical and physical properties of granites are presented and discussed. The major output of the work is the confirmation that ultrasonic pulse velocity can be effectively used as a simple and economical nondestructive method for a preliminary prediction of mechanical and physical properties, as well as a tool for the assessment of the weathering changes of granites that occur during the serviceable life. This is of much interest due to the usual difficulties in removing specimens for mechanical characterization.

  10. Effects of Defects on the Mechanical Properties of Kinked Silicon Nanowires.

    PubMed

    Chen, Yun; Zhang, Cheng; Li, Liyi; Tuan, Chia-Chi; Chen, Xin; Gao, Jian; He, Yunbo; Wong, Ching-Ping

    2017-12-01

    Kinked silicon nanowires (KSiNWs) have many special properties that make them attractive for a number of applications. The mechanical properties of KSiNWs play important roles in the performance of sensors. In this work, the effects of defects on the mechanical properties of KSiNWs are studied using molecular dynamics simulations and indirectly validated by experiments. It is found that kinks are weak points in the nanowire (NW) because of inharmonious deformation, resulting in a smaller elastic modulus than that of straight NWs. In addition, surface defects have more significant effects on the mechanical properties of KSiNWs than internal defects. The effects of the width or the diameter of the defects are larger than those of the length of the defects. Overall, the elastic modulus of KSiNWs is not sensitive to defects; therefore, KSiNWs have a great potential as strain or stress sensors in special applications.

  11. Mechanical Properties of Calcium Fluoride-Based Composite Materials

    PubMed Central

    Kleczewska, Joanna; Pryliński, Mariusz; Podlewska, Magdalena; Sokołowski, Jerzy; Łapińska, Barbara

    2016-01-01

    Aim of the study was to evaluate mechanical properties of light-curing composite materials modified with the addition of calcium fluoride. The study used one experimental light-curing composite material (ECM) and one commercially available flowable light-curing composite material (FA) that were modified with 0.5–5.0 wt% anhydrous calcium fluoride. Morphology of the samples and uniformity of CaF2 distribution were analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Mechanical properties were tested after 24-hour storage of specimens in dry or wet conditions. Stored dry ECM enriched with 0.5–1.0 wt% CaF2 showed higher tensile strength values, while water storage of all modified ECM specimens decreased their tensile strength. The highest Vickers hardness tested after dry storage was observed for 2.5 wt% CaF2 content in ECM. The addition of 2.0–5.0 wt% CaF2 to FA caused significant decrease in tensile strength after dry storage and overall tensile strength decrease of modified FA specimens after water storage. The content of 2.0 wt% CaF2 in FA resulted in the highest Vickers hardness tested after wet storage. Commercially available composite material (FA), unmodified with fluoride addition, demonstrated overall significantly higher mechanical properties. PMID:28004001

  12. Mechanical properties of metal dihydrides

    DOE PAGES

    Schultz, Peter A.; Snow, Clark S.

    2016-02-04

    First-principles calculations are used to characterize the bulk elastic properties of cubic and tetragonal phase metal dihydrides,more » $$\\text{M}{{\\text{H}}_{2}}$$ {$$\\text{M}$$ = Sc, Y, Ti, Zr, Hf, lanthanides} to gain insight into the mechanical properties that govern the aging behavior of rare-earth di-tritides as the constituent 3H, tritium, decays into 3He. As tritium decays, helium is inserted in the lattice, the helium migrates and collects into bubbles, that then can ultimately create sufficient internal pressure to rupture the material. The elastic properties of the materials are needed to construct effective mesoscale models of the process of bubble growth and fracture. Dihydrides of the scandium column and most of the rare-earths crystalize into a cubic phase, while dihydrides from the next column, Ti, Zr, and Hf, distort instead into the tetragonal phase, indicating incipient instabilities in the phase and potentially significant changes in elastic properties. We report the computed elastic properties of these dihydrides, and also investigate the off-stoichiometric phases as He or vacancies accumulate. As helium builds up in the cubic phase, the shear moduli greatly soften, converting to the tetragonal phase. Conversely, the tetragonal phases convert very quickly to cubic with the removal of H from the lattice, while the cubic phases show little change with removal of H. Finally, the source and magnitude of the numerical and physical uncertainties in the modeling are analyzed and quantified to establish the level of confidence that can be placed in the computational results, and this quantified confidence is used to justify using the results to augment and even supplant experimental measurements.« less

  13. Micro-mechanical evaluation of SiC-SiC composite interphase properties and debond mechanisms

    DOE PAGES

    Kabel, Joey; Yang, Y.; Balooch, Mehdi; ...

    2017-07-31

    SiC-SiC composites exhibit exceptional high temperature strength and oxidation properties making them an advantageous choice for accident tolerant nuclear fuel cladding. In the present work, small scale mechanical testing along with AFM and TEM analysis were employed to evaluate PyC interphase properties that play a key role in the overall mechanical behavior of the composite. The Mohr-Coulomb formulation allowed for the extraction of the internal friction coefficient and debonding shear strength as a function of the PyC layer thickness, an additional parameter. Here, these results have led to re-evaluation of the Mohr-Coulomb failure criterion and adjustment via a new phenomenologicalmore » equation.« less

  14. Study the bonding mechanism of binders on hydroxyapatite surface and mechanical properties for 3DP fabrication bone scaffolds.

    PubMed

    Wei, Qinghua; Wang, Yanen; Li, Xinpei; Yang, Mingming; Chai, Weihong; Wang, Kai; zhang, Yingfeng

    2016-04-01

    In 3DP fabricating artificial bone scaffolds process, the interaction mechanism between binder and bioceramics power determines the microstructure and macro mechanical properties of Hydroxyapatite (HA) bone scaffold. In this study, we applied Molecular Dynamics (MD) methods to investigating the bonding mechanism and essence of binders on the HA crystallographic planes for 3DP fabrication bone scaffolds. The cohesive energy densities of binders and the binding energies, PCFs g(r), mechanical properties of binder/HA interaction models were analyzed through the MD simulation. Additionally, we prepared the HA bone scaffold specimens with different glues by 3DP additive manufacturing, and tested their mechanical properties by the electronic universal testing machine. The simulation results revealed that the relationship of the binding energies between binders and HA surface is consistent with the cohesive energy densities of binders, which is PAM/HA>PVA/HA>PVP/HA. The PCFs g(r) indicated that their interfacial interactions mainly attribute to the ionic bonds and hydrogen bonds which formed between the polar atoms, functional groups in binder polymer and the Ca, -OH in HA. The results of mechanical experiments verified the relationship of Young׳s modulus for three interaction models in simulation, which is PVA/HA>PAM/HA>PVP/HA. But the trend of compressive strength is PAM/HA>PVA/HA>PVP/HA, this is consistent with the binding energies of simulation. Therefore, the Young׳s modulus of bone scaffolds are limited by the Young׳s modulus of binders, and the compressive strength is mainly decided by the viscosity of binder. Finally, the major reasons for differences in mechanical properties between simulation and experiment were found, the space among HA pellets and the incomplete infiltration of glue were the main reasons influencing the mechanical properties of 3DP fabrication HA bone scaffolds. These results provide useful information in choosing binder for 3DP fabrication

  15. Mechanical properties of DNA origami nanoassemblies are determined by Holliday junction mechanophores.

    PubMed

    Shrestha, Prakash; Emura, Tomoko; Koirala, Deepak; Cui, Yunxi; Hidaka, Kumi; Maximuck, William J; Endo, Masayuki; Sugiyama, Hiroshi; Mao, Hanbin

    2016-08-19

    DNA nanoassemblies have demonstrated wide applications in various fields including nanomaterials, drug delivery and biosensing. In DNA origami, single-stranded DNA template is shaped into desired nanostructure by DNA staples that form Holliday junctions with the template. Limited by current methodologies, however, mechanical properties of DNA origami structures have not been adequately characterized, which hinders further applications of these materials. Using laser tweezers, here, we have described two mechanical properties of DNA nanoassemblies represented by DNA nanotubes, DNA nanopyramids and DNA nanotiles. First, mechanical stability of DNA origami structures is determined by the effective density of Holliday junctions along a particular stress direction. Second, mechanical isomerization observed between two conformations of DNA nanotubes at 10-35 pN has been ascribed to the collective actions of individual Holliday junctions, which are only possible in DNA origami with rotational symmetric arrangements of Holliday junctions, such as those in DNA nanotubes. Our results indicate that Holliday junctions control mechanical behaviors of DNA nanoassemblies. Therefore, they can be considered as 'mechanophores' that sustain mechanical properties of origami nanoassemblies. The mechanical properties observed here provide insights for designing better DNA nanostructures. In addition, the unprecedented mechanical isomerization process brings new strategies for the development of nano-sensors and actuators. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

  16. Towards the feasibility of using ultrasound to determine mechanical properties of tissues in a bioreactor.

    PubMed

    Mansour, Joseph M; Gu, Di-Win Marine; Chung, Chen-Yuan; Heebner, Joseph; Althans, Jake; Abdalian, Sarah; Schluchter, Mark D; Liu, Yiying; Welter, Jean F

    2014-10-01

    Our ultimate goal is to non-destructively evaluate mechanical properties of tissue-engineered (TE) cartilage using ultrasound (US). We used agarose gels as surrogates for TE cartilage. Previously, we showed that mechanical properties measured using conventional methods were related to those measured using US, which suggested a way to non-destructively predict mechanical properties of samples with known volume fractions. In this study, we sought to determine whether the mechanical properties of samples, with unknown volume fractions could be predicted by US. Aggregate moduli were calculated for hydrogels as a function of SOS, based on concentration and density using a poroelastic model. The data were used to train a statistical model, which we then used to predict volume fractions and mechanical properties of unknown samples. Young's and storage moduli were measured mechanically. The statistical model generally predicted the Young's moduli in compression to within <10% of their mechanically measured value. We defined positive linear correlations between the aggregate modulus predicted from US and both the storage and Young's moduli determined from mechanical tests. Mechanical properties of hydrogels with unknown volume fractions can be predicted successfully from US measurements. This method has the potential to predict mechanical properties of TE cartilage non-destructively in a bioreactor.

  17. Towards the feasibility of using ultrasound to determine mechanical properties of tissues in a bioreactor

    PubMed Central

    Mansour, Joseph M.; Gu, Di-Win Marine; Chung, Chen-Yuan; Heebner, Joseph; Althans, Jake; Abdalian, Sarah; Schluchter, Mark D.; Liu, Yiying; Welter, Jean F.

    2016-01-01

    Introduction Our ultimate goal is to non-destructively evaluate mechanical properties of tissue-engineered (TE) cartilage using ultrasound (US). We used agarose gels as surrogates for TE cartilage. Previously, we showed that mechanical properties measured using conventional methods were related to those measured using US, which suggested a way to non-destructively predict mechanical properties of samples with known volume fractions. In this study, we sought to determine whether the mechanical properties of samples, with unknown volume fractions could be predicted by US. Methods Aggregate moduli were calculated for hydrogels as a function of SOS, based on concentration and density using a poroelastic model. The data were used to train a statistical model, which we then used to predict volume fractions and mechanical properties of unknown samples. Young's and storage moduli were measured mechanically. Results The statistical model generally predicted the Young's moduli in compression to within < 10% of their mechanically measured value. We defined positive linear correlations between the aggregate modulus predicted from US and both the storage and Young's moduli determined from mechanical tests. Conclusions Mechanical properties of hydrogels with unknown volume fractions can be predicted successfully from US measurements. This method has the potential to predict mechanical properties of TE cartilage non-destructively in a bioreactor. PMID:25092421

  18. Woven TPS Mechanical Property Evaluation

    NASA Technical Reports Server (NTRS)

    Gonzales, Gregory Lewis; Kao, David Jan-Woei; Stackpoole, Margaret M.

    2013-01-01

    Woven Thermal Protection Systems (WTPS) is a relatively new program funded by the Office of the Chief Technologist (OCT). The WTPS approach to producing TPS architectures uses precisely engineered 3-D weaving techniques that allow tailoring material characteristics needed to meet specific mission requirements. A series of mechanical tests were performed to evaluate performance of different weave types, and get a better understanding of failure modes expected in these three-dimensional architectures. These properties will aid in material down selection and guide selection of the appropriate WTPS for a potential mission.

  19. Size Effect on the Mechanical Properties of CF Winding Composite

    NASA Astrophysics Data System (ADS)

    Cui, Yuqing; Yin, Zhongwei

    2017-12-01

    Mechanical properties of filament winding composites are usually tested by NOL ring samples. Few people have studied the size effect of winding composite samples on the testing result of mechanical property. In this research, winding composite thickness, diameter, and geometry of NOL ring samples were prepared to investigate the size effect on the mechanical strength of carbon fiber (CF) winding composite. The CF T700, T1000, M40, and M50 were adopted for the winding composite, while the matrix was epoxy resin. Test results show that the tensile strength and ILSS of composites decreases monotonically with an increase of thickness from 1 mm to 4 mm. The mechanical strength of composite samples increases monotonically with the increase in diameter from 100 mm to 189 mm. The mechanical strength of composite samples with two flat sides are higher than those of cyclic annular samples.

  20. High-Throughput Assessment of Cellular Mechanical Properties.

    PubMed

    Darling, Eric M; Di Carlo, Dino

    2015-01-01

    Traditionally, cell analysis has focused on using molecular biomarkers for basic research, cell preparation, and clinical diagnostics; however, new microtechnologies are enabling evaluation of the mechanical properties of cells at throughputs that make them amenable to widespread use. We review the current understanding of how the mechanical characteristics of cells relate to underlying molecular and architectural changes, describe how these changes evolve with cell-state and disease processes, and propose promising biomedical applications that will be facilitated by the increased throughput of mechanical testing: from diagnosing cancer and monitoring immune states to preparing cells for regenerative medicine. We provide background about techniques that laid the groundwork for the quantitative understanding of cell mechanics and discuss current efforts to develop robust techniques for rapid analysis that aim to implement mechanophenotyping as a routine tool in biomedicine. Looking forward, we describe additional milestones that will facilitate broad adoption, as well as new directions not only in mechanically assessing cells but also in perturbing them to passively engineer cell state.

  1. Mechanical properties of graphene oxides.

    PubMed

    Liu, Lizhao; Zhang, Junfeng; Zhao, Jijun; Liu, Feng

    2012-09-28

    The mechanical properties, including the Young's modulus and intrinsic strength, of graphene oxides are investigated by first-principles computations. Structural models of both ordered and amorphous graphene oxides are considered and compared. For the ordered graphene oxides, the Young's modulus is found to vary from 380 to 470 GPa as the coverage of oxygen groups changes, respectively. The corresponding variations in the Young's modulus of the amorphous graphene oxides with comparable coverage are smaller at 290-430 GPa. Similarly, the ordered graphene oxides also possess higher intrinsic strength compared with the amorphous ones. As coverage increases, both the Young's modulus and intrinsic strength decrease monotonically due to the breaking of the sp(2) carbon network and lowering of the energetic stability for the ordered and amorphous graphene oxides. In addition, the band gap of the graphene oxide becomes narrower under uniaxial tensile strain, providing an efficient way to tune the electronic properties of graphene oxide-based materials.

  2. Modified Continuum Mechanics Modeling on Size-Dependent Properties of Piezoelectric Nanomaterials: A Review

    PubMed Central

    Yan, Zhi; Jiang, Liying

    2017-01-01

    Piezoelectric nanomaterials (PNs) are attractive for applications including sensing, actuating, energy harvesting, among others in nano-electro-mechanical-systems (NEMS) because of their excellent electromechanical coupling, mechanical and physical properties. However, the properties of PNs do not coincide with their bulk counterparts and depend on the particular size. A large amount of efforts have been devoted to studying the size-dependent properties of PNs by using experimental characterization, atomistic simulation and continuum mechanics modeling with the consideration of the scale features of the nanomaterials. This paper reviews the recent progresses and achievements in the research on the continuum mechanics modeling of the size-dependent mechanical and physical properties of PNs. We start from the fundamentals of the modified continuum mechanics models for PNs, including the theories of surface piezoelectricity, flexoelectricity and non-local piezoelectricity, with the introduction of the modified piezoelectric beam and plate models particularly for nanostructured piezoelectric materials with certain configurations. Then, we give a review on the investigation of the size-dependent properties of PNs by using the modified continuum mechanics models, such as the electromechanical coupling, bending, vibration, buckling, wave propagation and dynamic characteristics. Finally, analytical modeling and analysis of nanoscale actuators and energy harvesters based on piezoelectric nanostructures are presented. PMID:28336861

  3. Modified Continuum Mechanics Modeling on Size-Dependent Properties of Piezoelectric Nanomaterials: A Review.

    PubMed

    Yan, Zhi; Jiang, Liying

    2017-01-26

    Piezoelectric nanomaterials (PNs) are attractive for applications including sensing, actuating, energy harvesting, among others in nano-electro-mechanical-systems (NEMS) because of their excellent electromechanical coupling, mechanical and physical properties. However, the properties of PNs do not coincide with their bulk counterparts and depend on the particular size. A large amount of efforts have been devoted to studying the size-dependent properties of PNs by using experimental characterization, atomistic simulation and continuum mechanics modeling with the consideration of the scale features of the nanomaterials. This paper reviews the recent progresses and achievements in the research on the continuum mechanics modeling of the size-dependent mechanical and physical properties of PNs. We start from the fundamentals of the modified continuum mechanics models for PNs, including the theories of surface piezoelectricity, flexoelectricity and non-local piezoelectricity, with the introduction of the modified piezoelectric beam and plate models particularly for nanostructured piezoelectric materials with certain configurations. Then, we give a review on the investigation of the size-dependent properties of PNs by using the modified continuum mechanics models, such as the electromechanical coupling, bending, vibration, buckling, wave propagation and dynamic characteristics. Finally, analytical modeling and analysis of nanoscale actuators and energy harvesters based on piezoelectric nanostructures are presented.

  4. Structural, Mechanical, and Magnetic Properties of W Reinforced FeCo Alloys

    NASA Astrophysics Data System (ADS)

    Li, Gang; Corte-Real, Michelle; Yarlagadda, Shridhar; Vaidyanathan, Ranji; Xiao, John; Unruh, Karl

    2002-03-01

    Despite their superior soft magnetic properties, the poor mechanical properties of FeCo alloys have limited their potential use in rotating machines operating at elevated temperatures. In an attempt to address this shortcoming we have prepared bulk FeCo alloys at near equiatomic compositions reinforced by a relatively small volume fraction of continuous W fibers. These materials have been assembled by consolidating individual FeCo coated W fibers at elevated temperatures and moderate pressures. The mechanical and magnetic properties of the fiber reinforced composites have been studied and correlated with results of microstructural characterization.

  5. Nondestructive measurement of esophageal biaxial mechanical properties utilizing sonometry

    NASA Astrophysics Data System (ADS)

    Aho, Johnathon M.; Qiang, Bo; Wigle, Dennis A.; Tschumperlin, Daniel J.; Urban, Matthew W.

    2016-07-01

    Malignant esophageal pathology typically requires resection of the esophagus and reconstruction to restore foregut continuity. Reconstruction options are limited and morbid. The esophagus represents a useful target for tissue engineering strategies based on relative simplicity in comparison to other organs. The ideal tissue engineered conduit would have sufficient and ideally matched mechanical tolerances to native esophageal tissue. Current methods for mechanical testing of esophageal tissues both in vivo and ex vivo are typically destructive, alter tissue conformation, ignore anisotropy, or are not able to be performed in fluid media. The aim of this study was to investigate biomechanical properties of swine esophageal tissues through nondestructive testing utilizing sonometry ex vivo. This method allows for biomechanical determination of tissue properties, particularly longitudinal and circumferential moduli and strain energy functions. The relative contribution of mucosal-submucosal layers and muscular layers are compared to composite esophagi. Swine thoracic esophageal tissues (n  =  15) were tested by pressure loading using a continuous pressure pump system to generate stress. Preconditioning of tissue was performed by pressure loading with the pump system and pre-straining the tissue to in vivo length before data was recorded. Sonometry using piezocrystals was utilized to determine longitudinal and circumferential strain on five composite esophagi. Similarly, five mucosa-submucosal and five muscular layers from thoracic esophagi were tested independently. This work on esophageal tissues is consistent with reported uniaxial and biaxial mechanical testing and reported results using strain energy theory and also provides high resolution displacements, preserves native architectural structure and allows assessment of biomechanical properties in fluid media. This method may be of use to characterize mechanical properties of tissue engineered esophageal

  6. Data for prediction of mechanical properties of aspen flakeboards

    Treesearch

    C. G. Carll; P. Wang

    1983-01-01

    This research compared two methods of producing flakeboards with uniform density distribution (which could then be used to predict bending properties of flakeboards with density gradients). One of the methods was suspected of producing weak boards because it involved exertion of high pressures on cold mats. Although differences were found in mechanical properties of...

  7. Mechanical properties and fiber type composition of chronically inactive muscles

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Monti, R. J.; Vallance, K. A.; Kim, J. A.; Edgerton, V. R.

    2000-01-01

    A role for neuromuscular activity in the maintenance of skeletal muscle properties has been well established. However, the role of activity-independent factors is more difficult to evaluate. We have used the spinal cord isolation model to study the effects of chronic inactivity on the mechanical properties of the hindlimb musculature in cats and rats. This model maintains the connectivity between the motoneurons and the muscle fibers they innervate, but the muscle unit is electrically "silent". Consequently, the measured muscle properties are activity-independent and thus the advantage of using this model is that it provides a baseline level (zero activity) from which regulatory factors that affect muscle cell homeostasis can be defined. In the present paper, we will present a brief review of our findings using the spinal cord isolation model related to muscle mechanical and fiber type properties.

  8. Accurate atomistic potentials and training sets for boron-nitride nanostructures

    NASA Astrophysics Data System (ADS)

    Tamblyn, Isaac

    Boron nitride nanotubes exhibit exceptional structural, mechanical, and thermal properties. They are optically transparent and have high thermal stability, suggesting a wide range of opportunities for structural reinforcement of materials. Modeling can play an important role in determining the optimal approach to integrating nanotubes into a supporting matrix. Developing accurate, atomistic scale models of such nanoscale interfaces embedded within composites is challenging, however, due to the mismatch of length scales involved. Typical nanotube diameters range from 5-50 nm, with a length as large as a micron (i.e. a relevant length-scale for structural reinforcement). Unlike their carbon-based counterparts, well tested and transferable interatomic force fields are not common for BNNT. In light of this, we have developed an extensive training database of BN rich materials, under conditions relevant for BNNT synthesis and composites based on extensive first principles molecular dynamics simulations. Using this data, we have produced an artificial neural network potential capable of reproducing the accuracy of first principles data at significantly reduced computational cost, allowing for accurate simulation at the much larger length scales needed for composite design.

  9. The role of focal adhesion kinase in the regulation of cellular mechanical properties

    NASA Astrophysics Data System (ADS)

    Mierke, Claudia Tanja

    2013-12-01

    The regulation of mechanical properties is necessary for cell invasion into connective tissue or intra- and extravasation through the endothelium of blood or lymph vessels. Cell invasion is important for the regulation of many healthy processes such as immune response reactions and wound healing. In addition, cell invasion plays a role in disease-related processes such as tumor metastasis and autoimmune responses. Until now the role of focal adhesion kinase (FAK) in regulating mechanical properties of cells and its impact on cell invasion efficiency is still not well known. Thus, this review focuses on mechanical properties regulated by FAK in comparison to the mechano-regulating protein vinculin. Moreover, it points out the connection between cancer cell invasion and metastasis and FAK by showing that FAK regulates cellular mechanical properties required for cellular motility. Furthermore, it sheds light on the indirect interaction of FAK with vinculin by binding to paxillin, which then impairs the binding of paxillin to vinculin. In addition, this review emphasizes whether FAK fulfills regulatory functions similar to vinculin. In particular, it discusses the differences and the similarities between FAK and vinculin in regulating the biomechanical properties of cells. Finally, this paper highlights that both focal adhesion proteins, vinculin and FAK, synergize their functions to regulate the mechanical properties of cells such as stiffness and contractile forces. Subsequently, these mechanical properties determine cellular invasiveness into tissues and provide a source sink for future drug developments to inhibit excessive cell invasion and hence, metastases formation.

  10. Mechanical properties of polymer-infiltrated-ceramic (sodium aluminum silicate) composites for dental restoration.

    PubMed

    Cui, Bencang; Li, Jing; Wang, Huining; Lin, Yuanhua; Shen, Yang; Li, Ming; Deng, Xuliang; Nan, Cewen

    2017-07-01

    To fabricate indirect restorative composites for CAD/CAM applications and evaluate the mechanical properties. Polymer-infiltrated-ceramic composites were prepared through infiltrating polymer into partially sintered sodium aluminum silicate ceramic blocks and curing. The corresponding samples were fabricated according to standard ISO-4049 using for mechanical properties measurement. The flexural strength and fracture toughness were measured using a mechanical property testing machine. The Vickers hardness and elastic modulus were calculated from the results of nano-indentation. The microstructures were investigated using secondary electron detector. The density of the porous ceramic blocks was obtained through TG-DTA. The conversion degrees were calculated from the results of mid-infrared spectroscopy. The obtained polymer infiltrated composites have a maximum flexural strength value of 214±6.5MPa, Vickers hardness of 1.76-2.30GPa, elastic modulus of 22.63-27.31GPa, fracture toughness of 1.76-2.35MPam 1/2 and brittleness index of 0.75-1.32μm -1/2 . These results were compared with those of commercial CAD/CAM blocks. Our results suggest that these materials with good mechanical properties are comparable to two commercial CAD/CAM blocks. The sintering temperature could dramatically influence the mechanical properties. Restorative composites with superior mechanical properties were produced. These materials mimic the properties of natural dentin and could be a promising candidate for CAD/CAM applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Extreme mechanical properties of materials under extreme pressure and temperature conditions (Invited)

    NASA Astrophysics Data System (ADS)

    Kavner, A.; Armentrout, M. M.; Xie, M.; Weinberger, M.; Kaner, R. B.; Tolbert, S. H.

    2010-12-01

    A strong synergy ties together the high-pressure subfields of mineral physics, solid-state physics, and materials engineering. The catalog of studies measuring the mechanical properties of materials subjected to large differential stresses in the diamond anvil cell demonstrates a significant pressure-enhancement of strength across many classes of materials, including elemental solids, salts, oxides, silicates, and borides and nitrides. High pressure techniques—both radial diffraction and laser heating in the diamond anvil cell—can be used to characterize the behavior of ultrahard materials under extreme conditions, and help test hypotheses about how composition, structure, and bonding work together to govern the mechanical properties of materials. The principles that are elucidated by these studies can then be used to help design engineering materials to encourage desired properties. Understanding Earth and planetary interiors requires measuring equations of state of relevant materials, including oxides, silicates, and metals under extreme conditions. If these minerals in the diamond anvil cell have any ability to support a differential stress, the assumption of quasi-hydrostaticity no longer applies, with a resulting non-salubrious effect on attempts to measure equation of state. We illustrate these applications with the results of variety of studies from our laboratory and others’ that have used high-pressure radial diffraction techniques and also laser heating in the diamond anvil cell to characterize the mechanical properties of a variety of ultrahard materials, especially osmium metal, osmium diboride, rhenium diboride, and tungsten tetraboride. We compare ambient condition strength studies such as hardness testing with high-pressure studies, especially radial diffraction under differential stress. In addition, we outline criteria for evaluating mechanical properties of materials at combination high pressures and temperatures. Finally, we synthesize our

  12. Measurement of the Mechanical Properties of Intact Collagen Fibrils

    NASA Astrophysics Data System (ADS)

    Mercedes, H.; Heim, A.; Matthews, W. G.; Koob, T.

    2006-03-01

    Motivated by the genetic disorder Ehlers-Danlos syndrome (EDS), in which proper collagen synthesis is interrupted, we are investigating the structural and mechanical properties of collagen fibrils. The fibrous glycoprotein collagen is the most abundant protein found in the human body and plays a key role in the extracellular matrix of the connective tissue, the properties of which are altered in EDS. We have selected as our model system the collagen fibrils of the sea cucumber dermis, a naturally mutable tissue. This system allows us to work with native fibrils which have their proteoglycan complement intact, something that is not possible with reconstituted mammalian collagen fibrils. Using atomic force microscopy, we measure, as a function of the concentration of divalent cations, the fibril diameter, its response to force loading, and the changes in its rigidity. Through these experiments, we will shed light on the mechanisms which control the properties of the sea cucumber dermis and hope to help explain the altered connective tissue extracellular matrix properties associated with EDS.

  13. Optimization of mechanical properties, biocorrosion properties and antibacterial properties of as-cast Ti-Cu alloys.

    PubMed

    Zhang, Erlin; Ren, Jing; Li, Shengyi; Yang, Lei; Qin, Gaowu

    2016-10-21

    Ti-Cu sintered alloys have shown good antibacterial abilities. However, the sintered method (powder metallurgy) is not convenient to produce devices with a complex structure. In this paper, Ti-Cu alloys with 2.0, 3.0 and 4.0 wt.% Cu were prepared in an arc melting furnace and subjected to different heat treatments: solid solution and ageing, to explore the possibility of preparing an antibacterial Ti-Cu alloy by a casting method and to examine the effect of Cu content. Phase identification was conducted on an XRD diffraction meter, and the microstructure was observed by a metallographic microscope, a scanning electron microscope (SEM) with energy disperse spectroscopy (EDS) and transmission electron microscopy (TEM). Microhardness and the compressive property of Ti-Cu alloys were tested, and the corrosion resistance and antibacterial activity were assessed in order to investigate the effect of the Cu content. Results showed that the as-cast Ti-Cu alloys exhibited a very low antibacterial rate against Staphylococcus aureus (S. aureus). Heat treatment improved the antibacterial rate significantly, especially after a solid and ageing treatment (T6). Antibacterial rates as high as 90.33% and 92.57% were observed on Ti-3Cu alloy and Ti-4Cu alloy, respectively. The hardness, the compressive yield strength, the anticorrosion resistance and the antibacterial rate of Ti-Cu alloys increased with an increase of Cu content in all conditions. It was demonstrated that homogeneous distribution and a fine Ti 2 Cu phase played a very important role in the mechanical property, anticorrosion and antibacterial properties. Furthermore, it should be pointed out that the Cu content should be at least 3 wt.% to obtain good antibacterial properties (>90% antibacterial rate) as well as satisfactory mechanical properties.

  14. Effective thermo-mechanical properties and shape memory effect of CNT/SMP composites

    NASA Astrophysics Data System (ADS)

    Yang, Qingsheng; Liu, Xia; Leng, Fangfang

    2009-07-01

    Shape memory polymer (SMP) has been applied in many fields as intelligent sensors and actuators. In order to improve the mechanical properties and recovery force of SMP, the addition of minor amounts of carbon nanotubes (CNT) into SMP has attracted wide attention. A micromechanical model and thermo-mechanical properties of CNT/SMP composites were studied in this paper. The thermo-mechanical constitutive relation of intellectual composites with isotropic and transversely isotropic CNT was obtained. Moreover, the shape memory effect of CNT/SMP composites and the effect of temperature and the volume fraction of CNT were discussed. The work shows that CNT/SMP composites exhibit excellent macroscopic thermo-mechanical properties and shape memory effect, while both of them can be affected remarkably by temperature and the microstructure parameters.

  15. Effects of mechanical strain on optical properties of ZnO nanowire

    NASA Astrophysics Data System (ADS)

    Vazinishayan, Ali; Lambada, Dasaradha Rao; Yang, Shuming; Zhang, Guofeng; Cheng, Biyao; Woldu, Yonas Tesfaye; Shafique, Shareen; Wang, Yiming; Anastase, Ndahimana

    2018-02-01

    The main objective of this study is to investigate the influences of mechanical strain on optical properties of ZnO nanowire (NW) before and after embedding ZnS nanowire into the ZnO nanowire, respectively. For this work, commercial finite element modeling (FEM) software package ABAQUS and three-dimensional (3D) finite-difference time-domain (FDTD) methods were utilized to analyze the nonlinear mechanical behavior and optical properties of the sample, respectively. Likewise, in this structure a single focused Gaussian beam with wavelength of 633 nm was used as source. The dimensions of ZnO nanowire were defined to be 12280 nm in length and 103.2 nm in diameter with hexagonal cross-section. In order to investigate mechanical properties, three-point bending technique was adopted so that both ends of the model were clamped with mid-span under loading condition and then the physical deformation model was imported into FDTD solutions to study optical properties of ZnO nanowire under mechanical strain. Moreover, it was found that increase in the strain due to the external load induced changes in reflectance, transmittance and absorptance, respectively.

  16. Morphology, orientation, and mechanical properties of gelatin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Blanton, T.N.; Tsou, A.H.

    1996-12-31

    Gelatin is a polypeptide derived from degradation and disorganization of collagen fibers and is the primary binder in photographic emulsions. Gelatin provides the mechanical integrity and strength to the photographic emulsion allowing for packaging, handling, and photofinishing operations. Gelatin films generated from aqueous-solution casting can exist in a semicrystalline or an amorphous state. When a gelatin solution is cooled below its helix-coil transition temperature, partial renaturation of gelatin to form triple helices can occur. The degree of renaturation in a coated film is dependent upon the drying temperature and the drying rate. During the drying process, gelatin crystals can bemore » formed by lateral association of the triple helices through a mechanism of nucleation and growth of a fringed micelle structure. X-ray scattering techniques have been utilized to examine the morphology and orientation of gelatin films. Based on X-ray diffraction data, it is observed that aggregates of triple-helix rods lie parallel to the film plane but are symmetrically distributed within the film plane. Since a material`s physical and mechanical properties are related to its structure, it is necessary to understand and to characterize the morphological development in gelatin film formation. In this study, an X-ray diffractometer and pole figure goniometer were utilized to examine the structural development and orientation anisotropy in solid-state gelatin films. Also, in this study, the in-plane mechanical properties of a gelatin film were determined from a uniaxial tensile test, and the gelatin film properties in the thickness direction were extracted from an indentation test based on the finite element analysis of the indentation results using a viscoelastic material model.« less

  17. Room temperature mechanical properties of electron beam welded zircaloy-4 sheet

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Parga, C. J.; Rooyen, I. J.; Coryell, B. D.

    Room temperature mechanical properties of electron beam welded and plain Zircaloy-4 sheet (1.6mm thick) have been measured and compared. Various welding parameters were utilized to join sheet material. Electron beam welded specimens and as-received sheet specimens show comparable mechanical properties. Zr-4 sheet displays anisotropy; tensile properties measured for transverse display higher elastic modulus, yield strength, reduction of area and slightly lower ductility than for the longitudinal (rolling direction). Higher welding power increases the alloy’s hardness, elastic modulus and yield strength, with a corresponding decrease in tensile strength and ductility. The hardness measured at weld is comparable to the parent metalmore » hardness. Hardness at heat-affected-zone is slightly higher. Electron microscopic examination shows distinct microstructure morphology and grain size at the weld zone, HAZ and parent metal. A correlation between welding parameters, mechanical properties and microstructural features was established for electron beam welded Zircaloy-4 sheet material.« less

  18. Room temperature mechanical properties of electron beam welded zircaloy-4 sheet

    DOE PAGES

    Parga, C. J.; Rooyen, I. J.; Coryell, B. D.; ...

    2017-11-04

    Room temperature mechanical properties of electron beam welded and plain Zircaloy-4 sheet (1.6mm thick) have been measured and compared. Various welding parameters were utilized to join sheet material. Electron beam welded specimens and as-received sheet specimens show comparable mechanical properties. Zr-4 sheet displays anisotropy; tensile properties measured for transverse display higher elastic modulus, yield strength, reduction of area and slightly lower ductility than for the longitudinal (rolling direction). Higher welding power increases the alloy’s hardness, elastic modulus and yield strength, with a corresponding decrease in tensile strength and ductility. The hardness measured at weld is comparable to the parent metalmore » hardness. Hardness at heat-affected-zone is slightly higher. Electron microscopic examination shows distinct microstructure morphology and grain size at the weld zone, HAZ and parent metal. A correlation between welding parameters, mechanical properties and microstructural features was established for electron beam welded Zircaloy-4 sheet material.« less

  19. Role of Sequence and Structural Polymorphism on the Mechanical Properties of Amyloid Fibrils

    PubMed Central

    Kim, Jae In; Na, Sungsoo; Eom, Kilho

    2014-01-01

    Amyloid fibrils playing a critical role in disease expression, have recently been found to exhibit the excellent mechanical properties such as elastic modulus in the order of 10 GPa, which is comparable to that of other mechanical proteins such as microtubule, actin filament, and spider silk. These remarkable mechanical properties of amyloid fibrils are correlated with their functional role in disease expression. This suggests the importance in understanding how these excellent mechanical properties are originated through self-assembly process that may depend on the amino acid sequence. However, the sequence-structure-property relationship of amyloid fibrils has not been fully understood yet. In this work, we characterize the mechanical properties of human islet amyloid polypeptide (hIAPP) fibrils with respect to their molecular structures as well as their amino acid sequence by using all-atom explicit water molecular dynamics (MD) simulation. The simulation result suggests that the remarkable bending rigidity of amyloid fibrils can be achieved through a specific self-aggregation pattern such as antiparallel stacking of β strands (peptide chain). Moreover, we have shown that a single point mutation of hIAPP chain constituting a hIAPP fibril significantly affects the thermodynamic stability of hIAPP fibril formed by parallel stacking of peptide chain, and that a single point mutation results in a significant change in the bending rigidity of hIAPP fibrils formed by antiparallel stacking of β strands. This clearly elucidates the role of amino acid sequence on not only the equilibrium conformations of amyloid fibrils but also their mechanical properties. Our study sheds light on sequence-structure-property relationships of amyloid fibrils, which suggests that the mechanical properties of amyloid fibrils are encoded in their sequence-dependent molecular architecture. PMID:24551113

  20. Evaluation of mechanical properties of hybrid fiber (hemp, jute, kevlar) reinforced composites

    NASA Astrophysics Data System (ADS)

    Suresha, K. V.; Shivanand, H. K.; Amith, A.; Vidyasagar, H. N.

    2018-04-01

    In today's world composites play wide role in all the engineering fields. The reinforcement of composites decides the properties of the material. Natural fiber composites compared to synthetic fiber possesses poor mechanical properties. The solution for this problem is to use combination of natural fiber and synthetic fiber. Hybridization helps to improve the overall mechanical properties of the material. In this study, hybrid reinforced composites of Hemp fabric/Kevlar fabric/Epoxy and Jute fabric/ Kevlar fabric/Epoxy composites are fabricated using Simple hand layup technique followed by Vacuum bagging process. Appropriate test methods as per standards and guidelines are followed to analyze mechanical behavior of the composites. The mechanical characteristics like tensile, compression and flexural properties of the hybrid reinforced composites are tested as per the ASTM standards by series of tensile test; compression test and three point bending tests were conducted on the hybrid composites. A quantitative relationship between the Hemp fabric/Kevlar fabric/Epoxy and Jute/ Kevlar fabric/Epoxy has been established with constant thickness.

  1. Effect of Graphene Oxide on Mechanical Properties of Recycled Mortar

    NASA Astrophysics Data System (ADS)

    Fang, Changle; Long, Wujian; Wei, Jingjie; Xiao, Bingxu; Yan, Chen

    2017-12-01

    The use of recycled aggregate as replacement of natural aggregate has increased in recent years in order to reduce the high consumption of natural resources in construction industry. This paper presents an experimental investigation on the effect of graphene oxide (GO) on the mechanical properties of recycled mortar. It is showed that the recycled mortar with GO has a better mechanical properties than the recycled mortar without GO. Microstructural analysis of the recycled mortar with GO showed to have much denser and better crystallization of hydration product.

  2. Mechanical properties of monolayer graphene oxide.

    PubMed

    Suk, Ji Won; Piner, Richard D; An, Jinho; Ruoff, Rodney S

    2010-11-23

    Mechanical properties of ultrathin membranes consisting of one layer, two overlapped layers, and three overlapped layers of graphene oxide platelets were investigated by atomic force microscopy (AFM) imaging in contact mode. In order to evaluate both the elastic modulus and prestress of thin membranes, the AFM measurement was combined with the finite element method (FEM) in a new approach for evaluating the mechanics of ultrathin membranes. Monolayer graphene oxide was found to have a lower effective Young's modulus (207.6 ± 23.4 GPa when a thickness of 0.7 nm is used) as compared to the value reported for "pristine" graphene. The prestress (39.7-76.8 MPa) of the graphene oxide membranes obtained by solution-based deposition was found to be 1 order of magnitude lower than that obtained by others for mechanically cleaved graphene. The novel AFM imaging and FEM-based mapping methods presented here are of general utility for obtaining the elastic modulus and prestress of thin membranes.

  3. Machine Learning of Accurate Energy-Conserving Molecular Force Fields

    NASA Astrophysics Data System (ADS)

    Chmiela, Stefan; Tkatchenko, Alexandre; Sauceda, Huziel; Poltavsky, Igor; Schütt, Kristof; Müller, Klaus-Robert; GDML Collaboration

    Efficient and accurate access to the Born-Oppenheimer potential energy surface (PES) is essential for long time scale molecular dynamics (MD) simulations. Using conservation of energy - a fundamental property of closed classical and quantum mechanical systems - we develop an efficient gradient-domain machine learning (GDML) approach to construct accurate molecular force fields using a restricted number of samples from ab initio MD trajectories (AIMD). The GDML implementation is able to reproduce global potential-energy surfaces of intermediate-size molecules with an accuracy of 0.3 kcal/mol for energies and 1 kcal/mol/Å for atomic forces using only 1000 conformational geometries for training. We demonstrate this accuracy for AIMD trajectories of molecules, including benzene, toluene, naphthalene, malonaldehyde, ethanol, uracil, and aspirin. The challenge of constructing conservative force fields is accomplished in our work by learning in a Hilbert space of vector-valued functions that obey the law of energy conservation. The GDML approach enables quantitative MD simulations for molecules at a fraction of cost of explicit AIMD calculations, thereby allowing the construction of efficient force fields with the accuracy and transferability of high-level ab initio methods.

  4. The Effect of Water Molecules on Mechanical Properties of Cell Walls

    NASA Astrophysics Data System (ADS)

    Rahbar, Nima; Youssefian, Sina

    The unique properties of bamboo fibers come from their natural composite structures that comprise mainly cellulose nanofibrils in a matrix of intertwined hemicellulose and lignin called lignin-carbohydrate complex (LCC). Here, we have utilized atomistic simulations to investigate the mechanical properties and mechanisms of interactions between these materials, in the presence of water molecules. The role of hemicellulose found to be enhancing the mechanical properties and lignin found to be providing the strength of bamboo fibers. The abundance of Hbonds in hemicellulose chains is responsible for improving the mechanical behavior of LCC. The strong van der Waals forces between lignin molecules and cellulose nanofibrils are responsible for higher adhesion energy between LCC/cellulose nanofibrils. We also found out that the amorphous regions of cellulose nanofibrils is the weakest interface in bamboo Microfibrils. In presence of water, the elastic modulus of lignin increases at low water content and decreases in higher water content, whereas the hemicellulose elastic modulus constantly decreases. The variations of Radial Distribution Function and Free Fractional Volume of these materials with water suggest that water molecules enhance the mechanical properties of lignin by filling voids in the system and creating Hbond bridges between polymer chains. For hemicellulose, however, the effect is always regressive due to the destructive effect of water molecules on the Hbond of its dense structure.

  5. Increased Mechanical Properties Through the Addition of Zr to GRCop-84

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Lerch, Bradley A.

    2011-01-01

    GRCop-84 (Cu-8 at.% Cr-4 at.% Nb) has shown exceptional mechanical properties above 932 F (773 K). However, its properties below 932 F (773 K) are inferior to precipitation strengthened alloys such as Cu-Cr, Cu-Zr and Cu-Cr-Zr when they are in the fully aged, hard-drawn condition. It has been noted that the addition of small amounts of Zr, typically 0.1 wt.% to 0.5 wt.%, can greatly enhance the mechanical properties of copper-based alloys. Limited testing was conducted upon GRCop-84 with an addition of 0.4 wt.% Zr to determine its tensile, creep and low cycle fatigue (LCF) properties. Very large increases in strength (up to 68%) and ductility (up to 123%) were observed at both room temperature and 932 F (773 K). Creep properties at 932 F (773 K) demonstrated more than an order of magnitude decrease in the creep rate relative to unmodified GRCop-84 with a corresponding order of magnitude increase in creep life. Limited LCF testing showed that the modified alloy had a comparable LCF life at room temperature, but it was capable of sustaining a much higher load. While more testing and composition optimization are required, the addition of Zr to GRCop-84 has shown clear benefits to mechanical properties.

  6. Molecular dynamics modelling of mechanical properties of polymers for adaptive aerospace structures

    NASA Astrophysics Data System (ADS)

    Papanikolaou, Michail; Drikakis, Dimitris; Asproulis, Nikolaos

    2015-02-01

    The features of adaptive structures depend on the properties of the supporting materials. For example, morphing wing structures require wing skin materials, such as rubbers that can withstand the forces imposed by the internal mechanism while maintaining the required aerodynamic properties of the aircraft. In this study, Molecular Dynamics and Minimization simulations are being used to establish well-equilibrated models of Ethylene-Propylene-Diene Monomer (EPDM) elastomer systems and investigate their mechanical properties.

  7. Effect of nanopatterning on mechanical properties of Lithium anode

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Campbell, Colin; Lee, Yong Min; Cho, Kuk Young

    One of the challenges in developing Lithium anodes for Lithium ion batteries (LIB) is controlling the formation of Li dendrites during cycling of the battery. Nanostructuring and nanopatterning of electrodes shows a promising way to suppress the growth of Li dendrites. However, in order to control this behavior, a fundamental understanding of the effect of nanopatterning on the electromechanical properties of Li metal is necessary. In this paper, we have investigated the mechanical and wear properties of Li metal using Atomic Force Microscopy (AFM) in an airtight cell. By using different load regimes, we determined the mechanical properties of Limore » metal. Here, we show that as a result of nanopatterning, Li metal surface underwent work hardening due to residual compressive stress. The presence of such stresses can help to improve cycle lifetime of LIBs with Li anodes and obtain very high energy densities.« less

  8. Effect of nanopatterning on mechanical properties of Lithium anode

    DOE PAGES

    Campbell, Colin; Lee, Yong Min; Cho, Kuk Young; ...

    2018-02-06

    One of the challenges in developing Lithium anodes for Lithium ion batteries (LIB) is controlling the formation of Li dendrites during cycling of the battery. Nanostructuring and nanopatterning of electrodes shows a promising way to suppress the growth of Li dendrites. However, in order to control this behavior, a fundamental understanding of the effect of nanopatterning on the electromechanical properties of Li metal is necessary. In this paper, we have investigated the mechanical and wear properties of Li metal using Atomic Force Microscopy (AFM) in an airtight cell. By using different load regimes, we determined the mechanical properties of Limore » metal. Here, we show that as a result of nanopatterning, Li metal surface underwent work hardening due to residual compressive stress. The presence of such stresses can help to improve cycle lifetime of LIBs with Li anodes and obtain very high energy densities.« less

  9. Crash Padding Research : Vol. I. Material Mechanical Properties.

    DOT National Transportation Integrated Search

    1986-08-01

    The dynamic mechanical properties of Uniroyal Ensolite AAC, a viscoelastic closed-cell foam rubber, are investigated by means of materials tests. Sufficient test data is presented to form a basis for one-dimensional (uniform compression) empirical co...

  10. Microstructure and Mechanical Properties of Additively Manufactured Parts with Staircase Feature

    NASA Astrophysics Data System (ADS)

    Keya, Tahmina

    This thesis focuses on a part with staircase feature that is made of Inconel 718 and fabricated by SLM process. The objective of the study was to observe build height effect on the microstructure and mechanical properties of the part. Due to the nature of SLM, there is possibility of different microstructure and mechanical properties in different locations depending on the design of the part. The objective was to compare microstructure and mechanical properties from different location and four comparison groups were considered: 1. Effect of thermal cycle; 2. External and internal surfaces; 3. Build height effect and 4. Bottom surfaces. To achieve the goals of this research, standard metallurgical procedure has been performed to prepare samples. Etching was done to reveal the microstructure of SLM processed Inconel 718 parts. Young's modulus and hardness were measured using nanoindentation technique. FEM analysis was performed to simulate nanoindentation. The conclusions drawn from this research are: 1. The microstructure of front and side surface of SLM processed Inconel 718 consists of arc shaped cut ends of melt pools with intermetallic phase at the border of the melt pool; 2. On top surface, melted tracks and scanning patterns can be observed and the average width of melted tracks is 100-150 microm; 3. The microstructure looks similar at different build height; 4. Microstructure on the top of a stair is more defined and organized than the internal surface; 5. The mechanical properties are highest at the bottom. OM images revealed slight difference in microstructure in terms of build height for this specific part, but mechanical properties seem to be vary noticeably. This is something to be kept in mind while designing or determining build orientation. External and internal surfaces of a stair at the same height showed difference in both microstructure and mechanical properties. To minimize that effect and to make it more uniform, gradual elevation can be

  11. Intravenous immunoglobulins – understanding properties and mechanisms

    PubMed Central

    Durandy, A; Kaveri, S V; Kuijpers, T W; Basta, M; Miescher, S; Ravetch, J V; Rieben, R

    2009-01-01

    High-dose intravenous immunoglobulin (IVIg) preparations are used currently for the treatment of autoimmune or inflammatory diseases. Despite numerous studies demonstrating efficacy, the precise mode of action of IVIg remains unclear. Paradoxically, IgG can exert both pro- and anti-inflammatory activities, depending on its concentration. The proinflammatory activity of low-dose IVIg requires complement activation or binding of the Fc fragment of IgG to IgG-specific receptors (FcγR) on innate immune effector cells. In contrast, when administered in high concentrations, IVIg has anti-inflammatory properties. How this anti-inflammatory effect is mediated has not yet been elucidated fully, and several mutually non-exclusive mechanisms have been proposed. This paper represents the proceedings of a session entitled ‘IVIg – Understanding properties and mechanisms’ at the 6th International Immunoglobulin Symposium that was held in Interlaken on 26–28 March 2009. The presentations addressed how IgG may affect the cellular compartment, evidence for IVIg-mediated scavenging of complement fragments, the role of the dimeric fraction of IVIg, the anti-inflammatory properties of the minor fraction of sialylated IgG molecules, and the genetic organization and variation in FcγRs. These findings demonstrate the considerable progress that has been made in understanding the mechanisms of action of IVIgs, and may influence future perspectives in the field of Ig therapy. PMID:19883419

  12. Improvement of Mechanical Properties of Spheroidized 1045 Steel by Induction Heat Treatment

    NASA Astrophysics Data System (ADS)

    Kim, Minwook; Shin, Jung-Ho; Choi, Young; Lee, Seok-Jae

    2016-04-01

    The effects of induction heat treatment on the formation of carbide particles and mechanical properties of spheroidized 1045 steel were investigated by means of microstructural analysis and tensile testing. The induction spheroidization accelerated the formation of spherical cementite particles and effectively softened the steel. The volume fraction of cementite was found to be a key factor that affected the mechanical properties of spheroidized steels. Further tests showed that sequential spheroidization by induction and furnace heat treatments enhanced elongation within a short spheroidization time, resulting in better mechanical properties. This was due to the higher volume fraction of spherical cementite particles that had less diffusion time for particle coarsening.

  13. Mechanical properties of hyaline and repair cartilage studied by nanoindentation.

    PubMed

    Franke, O; Durst, K; Maier, V; Göken, M; Birkholz, T; Schneider, H; Hennig, F; Gelse, K

    2007-11-01

    Articular cartilage is a highly organized tissue that is well adapted to the functional demands in joints but difficult to replicate via tissue engineering or regeneration. Its viscoelastic properties allow cartilage to adapt to both slow and rapid mechanical loading. Several cartilage repair strategies that aim to restore tissue and protect it from further degeneration have been introduced. The key to their success is the quality of the newly formed tissue. In this study, periosteal cells loaded on a scaffold were used to repair large partial-thickness cartilage defects in the knee joint of miniature pigs. The repair cartilage was analyzed 26 weeks after surgery and compared both morphologically and mechanically with healthy hyaline cartilage. Contact stiffness, reduced modulus and hardness as key mechanical properties were examined in vitro by nanoindentation in phosphate-buffered saline at room temperature. In addition, the influence of tissue fixation with paraformaldehyde on the biomechanical properties was investigated. Although the repair process resulted in the formation of a stable fibrocartilaginous tissue, its contact stiffness was lower than that of hyaline cartilage by a factor of 10. Fixation with paraformaldehyde significantly increased the stiffness of cartilaginous tissue by one order of magnitude, and therefore, should not be used when studying biomechanical properties of cartilage. Our study suggests a sensitive method for measuring the contact stiffness of articular cartilage and demonstrates the importance of mechanical analysis for proper evaluation of the success of cartilage repair strategies.

  14. Elastic and Mechanical Properties of the MAX Phases

    NASA Astrophysics Data System (ADS)

    Barsoum, Michel W.; Radovic, Miladin

    2011-08-01

    The more than 60 ternary carbides and nitrides, with the general formula Mn+1AXn—where n = 1, 2, or 3; M is an early transition metal; A is an A-group element (a subset of groups 13-16); and X is C and/or N—represent a new class of layered solids, where Mn+1Xn layers are interleaved with pure A-group element layers. The growing interest in the Mn+1AXn phases lies in their unusual, and sometimes unique, set of properties that can be traced back to their layered nature and the fact that basal dislocations multiply and are mobile at room temperature. Because of their chemical and structural similarities, the MAX phases and their corresponding MX phases share many physical and chemical properties. In this paper we review our current understanding of the elastic and mechanical properties of bulk MAX phases where they differ significantly from their MX counterparts. Elastically the MAX phases are in general quite stiff and elastically isotropic. The MAX phases are relatively soft (2-8 GPa), are most readily machinable, and are damage tolerant. Some of them are also lightweight and resistant to thermal shock, oxidation, fatigue, and creep. In addition, they behave as nonlinear elastic solids, dissipating 25% of the mechanical energy during compressive cycling loading of up to 1 GPa at room temperature. At higher temperatures, they undergo a brittle-to-plastic transition, and their mechanical behavior is a strong function of deformation rate.

  15. Mechanical properties of a biodegradable bone regeneration scaffold

    NASA Technical Reports Server (NTRS)

    Porter, B. D.; Oldham, J. B.; He, S. L.; Zobitz, M. E.; Payne, R. G.; An, K. N.; Currier, B. L.; Mikos, A. G.; Yaszemski, M. J.

    2000-01-01

    Poly (Propylene Fumarate) (PPF), a novel, bulk erosion, biodegradable polymer, has been shown to have osteoconductive effects in vivo when used as a bone regeneration scaffold (Peter, S. J., Suggs, L. J., Yaszemski, M. J., Engel, P. S., and Mikos, A. J., 1999, J. Biomater. Sci. Polym. Ed., 10, pp. 363-373). The material properties of the polymer allow it to be injected into irregularly shaped voids in vivo and provide mechanical stability as well as function as a bone regeneration scaffold. We fabricated a series of biomaterial composites, comprised of varying quantities of PPF, NaCl and beta-tricalcium phosphate (beta-TCP), into the shape of right circular cylinders and tested the mechanical properties in four-point bending and compression. The mean modulus of elasticity in compression (Ec) was 1204.2 MPa (SD 32.2) and the mean modulus of elasticity in bending (Eb) was 1274.7 MPa (SD 125.7). All of the moduli were on the order of magnitude of trabecular bone. Changing the level of NaCl from 20 to 40 percent, by mass, did not decrease Ec and Eb significantly, but did decrease bending and compressive strength significantly. Increasing the beta-TCP from 0.25 g/g PPF to 0.5 g/g PPF increased all of the measured mechanical properties of PPF/NVP composites. These results indicate that this biodegradable polymer composite is an attractive candidate for use as a replacement scaffold for trabecular bone.

  16. Selective flow-induced vesicle rupture to sort by membrane mechanical properties

    NASA Astrophysics Data System (ADS)

    Pommella, Angelo; Brooks, Nicholas J.; Seddon, John M.; Garbin, Valeria

    2015-08-01

    Vesicle and cell rupture caused by large viscous stresses in ultrasonication is central to biomedical and bioprocessing applications. The flow-induced opening of lipid membranes can be exploited to deliver drugs into cells, or to recover products from cells, provided that it can be obtained in a controlled fashion. Here we demonstrate that differences in lipid membrane and vesicle properties can enable selective flow-induced vesicle break-up. We obtained vesicle populations with different membrane properties by using different lipids (SOPC, DOPC, or POPC) and lipid:cholesterol mixtures (SOPC:chol and DOPC:chol). We subjected vesicles to large deformations in the acoustic microstreaming flow generated by ultrasound-driven microbubbles. By simultaneously deforming vesicles with different properties in the same flow, we determined the conditions in which rupture is selective with respect to the membrane stretching elasticity. We also investigated the effect of vesicle radius and excess area on the threshold for rupture, and identified conditions for robust selectivity based solely on the mechanical properties of the membrane. Our work should enable new sorting mechanisms based on the difference in membrane composition and mechanical properties between different vesicles, capsules, or cells.

  17. Selective flow-induced vesicle rupture to sort by membrane mechanical properties

    PubMed Central

    Pommella, Angelo; Brooks, Nicholas J.; Seddon, John M.; Garbin, Valeria

    2015-01-01

    Vesicle and cell rupture caused by large viscous stresses in ultrasonication is central to biomedical and bioprocessing applications. The flow-induced opening of lipid membranes can be exploited to deliver drugs into cells, or to recover products from cells, provided that it can be obtained in a controlled fashion. Here we demonstrate that differences in lipid membrane and vesicle properties can enable selective flow-induced vesicle break-up. We obtained vesicle populations with different membrane properties by using different lipids (SOPC, DOPC, or POPC) and lipid:cholesterol mixtures (SOPC:chol and DOPC:chol). We subjected vesicles to large deformations in the acoustic microstreaming flow generated by ultrasound-driven microbubbles. By simultaneously deforming vesicles with different properties in the same flow, we determined the conditions in which rupture is selective with respect to the membrane stretching elasticity. We also investigated the effect of vesicle radius and excess area on the threshold for rupture, and identified conditions for robust selectivity based solely on the mechanical properties of the membrane. Our work should enable new sorting mechanisms based on the difference in membrane composition and mechanical properties between different vesicles, capsules, or cells. PMID:26302783

  18. Mechanical properties of HDPE/UHMWPE blends: effect of filler loading and filler treatment.

    PubMed

    Lai, K L K; Roziyanna, A; Ogunniyi, D S; Zainal, Arifin M I; Azlan, Ariffin A

    2004-05-01

    Various blend ratios of high-density polyethylene (HDPE) and ultra high molecular weight polyethylene (UHMWPE) were prepared with the objective of determining their suitability as biomaterials. In the unfilled state, a blend of 50/50 (HDPE/UHMWPE) ratio by weight was found to yield optimum properties in terms of processability and mechanical properties. Hydroxyapatite (HA) was compounded with the optimum blend ratio. The effects of HA loading, varied from 0 to 50wt% for both filled and unfilled blends were tested for mechanical properties. It was found that the inclusion of HA in the blend led to a remarkable improvement of mechanical properties compared to the unfilled blend. In order to improve the bonding between the polymer blend and the filler, the HA used was chemically treated with a coupling agent known as 3-(trimethoxysiyl) propyl methacrylate and the treated HA was mixed into the blend. The effect of mixing the blend with silane-treated HA also led to an overall improvement of mechanical properties.

  19. Effect of Casting Defect on Mechanical Properties of 17-4PH Stainless Steel

    NASA Astrophysics Data System (ADS)

    Kim, Jong-Yup; Lee, Joon-Hyun; Nahm, Seung-Hoon

    Damage and integrity evaluation techniques should be developed steadily in order to ensure the reliability and the economic efficiency of gas turbine engines. Casting defects may exist in most casting components of gas turbine engines, and the defects could give serious effect on mechanical properties and fracture toughness. Therefore, it is very important to understand the effect of casting defects on the above properties in order to predict the safety and life of components. In this study, specimens with internal casting defects, made from 17-4PH stainless steel, were prepared and evaluated and characterized based on the volume fraction of defects. The relation between mechanical properties such as tensile, low cycle fatigue and fracture toughness and volume fraction of defect has been investigated. As a result of the analysis, the mechanical properties of 17-4PH decreased as the defect volume fraction increased with very good linearity. The mechanical properties also showed an inversely proportional relationship to electrical resistivity.

  20. The Electromagnetic and Mechanical Properties of Structural Composites: A Theoretical and Experimental Design Study

    DTIC Science & Technology

    2014-08-22

    higher frequencies due to weaves with smaller unit cells. A second predicts the dielectric properties of unidirectional composite fabrics and laminates ...effective dielectric properties of composite laminates within the X- band (8-12 GHz). The circuit analog method becomes less accurate as the...architectures and to multilayered laminates . In this project, experimental validation from 4-50 GHz is provided for single layers of dry structural grade

  1. Effect of cobalt doping on the mechanical properties of ZnO nanowires

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vahtrus, Mikk; Šutka, Andris

    In this work, we investigate the influence of doping on the mechanical properties of ZnO nanowires (NWs) by comparing the mechanical properties of pure and Co-doped ZnO NWs grown in similar conditions and having the same crystallographic orientation [0001]. The mechanical characterization included three-point bending tests made with atomic force microscopy and cantilever beam bending tests performed inside scanning electron microscopy. It was found that the Young's modulus of ZnO NWs containing 5% of Co was approximately a third lower than that of the pure ZnO NWs. Bending strength values were comparable for both materials and in both cases weremore » close to theoretical strength indicating high quality of NWs. Dependence of mechanical properties on NW diameter was found for both doped and undoped ZnO NWs. - Highlights: •Effect of Co doping on the mechanical properties of ZnO nanowires is studied. •Co substitutes Zn atoms in ZnO crystal lattice. •Co addition affects crystal lattice parameters. •Co addition results in significantly decreased Young's modulus of ZnO. •Bending strength for doped and undoped wires is close to the theoretical strength.« less

  2. The effect of thermal damage on the mechanical properties of polymer regrinds

    NASA Technical Reports Server (NTRS)

    Kundu, Nikhil K.

    1990-01-01

    Reprocessed polymers are subjected to high processing temperatures that result in the breakdown of molecular chains and changes in the molecular structures. These phenomena are reflected in the mechanical properties of materials. Practically every regrind is seen as a new material. These experiments deal with the molding, regrinding, and reprocessing of test specimens for the study of their mechanical properties. The comparative test data from each recycled material would give students an insight of the molecular structures and property degradation. Three important rheological and mechanical properties such as melt flow, impact strength, and flexural strength are to be determined. These properties play key roles in the selection of engineering materials. The material selected for demonstration was Makrolon 3000L, a polycarbonate thermoplastic from Bayer AG. The thermal degradation due to repeated processing is reflected in the decrease in molecular weight and breakdown of molecular chains causing increase in melt flow. The Izod-impact resistance and the flexural strength deteriorate gradually.

  3. Mechanical properties of 4d transition metals in molten state

    NASA Astrophysics Data System (ADS)

    Singh, Deobrat; Sonvane, Yogesh; Thakor, P. B.

    2016-05-01

    Mechanical properties of 4d transition metals in molten state have been studied in the present study. We have calculated mechanical properties such as isothermal bulk modulus (B), modulus of rigidity (G), Young's modulus (Y) and Hardness have also been calculated from the elastic part of the Phonon dispersion curve (PDC). To describe the structural information, we have used different structure factor S(q) using Percus-Yevick hard sphere (PYHS) reference systems along with our newly constructed parameter free model potential.To see the influence of exchange and correlation effect on the above said properties of 3d liquid transition metals, we have used Sarkar et al (S)local field correction functions. Present results have been found good in agreement with available experimental data.

  4. Design and mechanical properties of insect cuticle.

    PubMed

    Vincent, Julian F V; Wegst, Ulrike G K

    2004-07-01

    Since nearly all adult insects fly, the cuticle has to provide a very efficient and lightweight skeleton. Information is available about the mechanical properties of cuticle-Young's modulus of resilin is about 1 MPa, of soft cuticles about 1 kPa to 50 MPa, of sclerotised cuticles 1-20 GPa; Vicker's Hardness of sclerotised cuticle ranges between 25 and 80 kgf mm(-2); density is 1-1.3 kg m(-3)-and one of its components, chitin nanofibres, the Young's modulus of which is more than 150 GPa. Experiments based on fracture mechanics have not been performed although the layered structure probably provides some toughening. The structural performance of wings and legs has been measured, but our understanding of the importance of buckling is lacking: it can stiffen the structure (by elastic postbuckling in wings, for example) or be a failure mode. We know nothing of fatigue properties (yet, for instance, the insect wing must undergo millions of cycles, flexing or buckling on each cycle). The remarkable mechanical performance and efficiency of cuticle can be analysed and compared with those of other materials using material property charts and material indices. Presented in this paper are four: Young's modulus-density (stiffness per unit weight), specific Young's modulus-specific strength (elastic hinges, elastic energy storage per unit weight), toughness-Young's modulus (fracture resistance under various loading conditions), and hardness (wear resistance). In conjunction with a structural analysis of cuticle these charts help to understand the relevance of microstructure (fibre orientation effects in tendons, joints and sense organs, for example) and shape (including surface structure) of this fibrous composite for a given function. With modern techniques for analysis of structure and material, and emphasis on nanocomposites and self-assembly, insect cuticle should be the archetype for composites at all levels of scale.

  5. PICA Variants with Improved Mechanical Properties

    NASA Technical Reports Server (NTRS)

    Thornton, Jeremy; Ghandehari, Ehson M.; Fan, Wenhong; Stackpoole, Margaret; Chavez-Garcia, Jose

    2011-01-01

    Phenolic Impregnated Carbon Ablator (PICA) is a member of the family of Lightweight Ceramic Ablators (LCAs) and was developed at NASA Ames Research Center as a thermal protection system (TPS) material for the Stardust mission probe that entered the Earth s atmosphere faster than any other probe or vehicle to date. PICA, carbon fiberform base and phenolic polymer, shows excellent thermal insulative properties at heating rates from about 250 W/sq cm to 1000 W/sq cm. The density of standard PICA - 0.26 g/cu cm to 0.28 g/cu cm - can be changed by changing the concentration of the phenolic resin. By adding polymers to the phenolic resin before curing it is possible to significantly improve the mechanical properties of PICA without significantly increasing the density.

  6. Interface effects on mechanical properties of particle-reinforced composites.

    PubMed

    Debnath, S; Ranade, R; Wunder, S L; McCool, J; Boberick, K; Baran, G

    2004-09-01

    Effective bonding between the filler and matrix components typically improves the mechanical properties of polymer composites containing inorganic fillers. The aim of this study was to test the hypothesis that composite flexural modulus, flexure strength, and toughness are directly proportional to filler-matrix interfacial shear strength. The resin matrix component of the experimental composite consisted of a 60:40 blend of BisGMA:TEGDMA. Two levels of photoinitiator components were used: 0.15, and 0.5%. Raman spectroscopy was used to determine degree of cure, and thermogravimetry (TGA) was used to quantify the degree of silane, rubber, or polymer attachment to silica and glass particles. Filler-matrix interfacial shear strengths were measured using a microbond test. Composites containing glass particles with various surface treatments were prepared and the modulus, flexure strength, and fracture toughness of these materials obtained using standard methods. Mechanical properties were measured on dry and soaked specimens. The interfacial strength was greatest for the 5% MPS treated silica, and it increased for polymers prepared with 0.5% initiator compared with 0.15% initiator concentrations. For the mechanical properties measured, the authors found that: (1) the flexural modulus was independent of the type of filler surface treatment, though flexural strength and toughness were highest for the silanated glass; (2) rubber at the interface, whether bonded to the filler and matrix or not, did not improve toughness; (3) less grafting of resin to silanated filler particles was observed when the initiator concentration decreased. These findings suggest that increasing the strength of the bond between filler and matrix will not result in improvements in the mechanical properties of particulate-reinforced composites in contrast to fiber-reinforced composites. Also, contraction stresses in the 0.5 vs 0.15% initiator concentration composites may be responsible for increases

  7. Some physical and mechanical properties of recycled polyurethane foam blends

    NASA Astrophysics Data System (ADS)

    Bledzki, A. K.; Zicans, J.; Merijs Meri, R.; Kardasz, D.

    2008-09-01

    Blends of secondary rigid polyurethane foams (RPUFs) with soft polyurethane foams (SPUFs) were investigated. The effect of SPUF content and its chemical nature on some physical and mechanical properties of the blends was evaluated. Owing to the stronger intermolecular interaction and higher values of cohesion energy, the blends of RPUFs with polyester SPUFs showed higher mechanical properties than those with polyether SPUFs. The density, hardness, ultimate strength, and the tensile, shear, and flexural moduli increased, while the impact toughness, ultimate elongation, and damping characteristics decreased with increasing RPUF content in the blends.

  8. Mechanical Properties of Irradiated Polarization-Maintaining Optical Fibers

    NASA Technical Reports Server (NTRS)

    Moeti, L.; Moghazy, S.; Ally, A.; Barnes, S.; Watkins, L.; Cuddihy, E.

    1996-01-01

    Polarization-maintaining optical fibers, referred to as PANDA fibers, were subjected to Cobalt 60 radiation (300,000 Rad). The mechanical properties of the PANDA fibers were measured after exposure to gamma radiation and compared to non-irradiated PANDA fibers.

  9. Effect of SMAT on microstructural and mechanical properties of AA2024

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tadge, Prashant, E-mail: prashant-tadge@rediffmail.com; Sasikumar, C., E-mail: csasimv@gmail.com

    In recent days surface mechanical attrition treatment (SMAT) had attracted the attention of researchers as it produces a nano-crystalline surface with improved mechanical properties. In the present study Al-4%Cu alloy used in automobile and aerospace application is subjected to surface mechanical attrition treatment using steel shots. The microstructural changes introduced on the surface of the Al alloy was investigated using Scanning Electron Microscopy (SEM). The secondary phases formed during the SMAT process is been investigated using EDX and XRD analysis. The effects of SMAT on the mechanical properties were analyzed using a tensile testing. The SMA treatment had resulted inmore » severe plastic deformation of the surface, thereby yielded a nanocrystalline surface with a grain size of 30 to 50 nm. Further, it is also found that the SMAT produced ultra nanocrystalline particles of Cu{sub 2}Al dispersed uniformly into α-Al matrix. These microstructural changes had resulted in considerable change in the mechanical properties of these alloys. The tensile strength of these alloys had increased from ∼212 MPa to 303 MPa while the fracture toughness increased up to 28% in 10 minutes of SMAT.« less

  10. Effect of SMAT on microstructural and mechanical properties of AA2024

    NASA Astrophysics Data System (ADS)

    Tadge, Prashant; Sasikumar, C.

    2016-05-01

    In recent days surface mechanical attrition treatment (SMAT) had attracted the attention of researchers as it produces a nano-crystalline surface with improved mechanical properties. In the present study Al-4%Cu alloy used in automobile and aerospace application is subjected to surface mechanical attrition treatment using steel shots. The microstructural changes introduced on the surface of the Al alloy was investigated using Scanning Electron Microscopy (SEM). The secondary phases formed during the SMAT process is been investigated using EDX and XRD analysis. The effects of SMAT on the mechanical properties were analyzed using a tensile testing. The SMA treatment had resulted in severe plastic deformation of the surface, thereby yielded a nanocrystalline surface with a grain size of 30 to 50 nm. Further, it is also found that the SMAT produced ultra nanocrystalline particles of Cu2Al dispersed uniformly into α-Al matrix. These microstructural changes had resulted in considerable change in the mechanical properties of these alloys. The tensile strength of these alloys had increased from ˜212 MPa to 303 MPa while the fracture toughness increased up to 28% in 10 minutes of SMAT.

  11. Nanostructured BN-Mg composites: features of interface bonding and mechanical properties.

    PubMed

    Kvashnin, Dmitry G; Krasheninnikov, Arkady V; Shtansky, Dmitry; Sorokin, Pavel B; Golberg, Dmitri

    2016-01-14

    Magnesium (Mg) is one of the lightest industrially used metals. However, wide applications of Mg-based components require a substantial enhancement of their mechanical characteristics. This can be achieved by introducing small particles or fibers into the metal matrix. Using first-principles calculations, we investigate the stability and mechanical properties of a nanocomposite made of magnesium reinforced with boron nitride (BN) nanostructures (BN nanotubes and BN monolayers). We show that boron vacancies at the BN/Mg interface lead to a substantial increase in BN/Mg bonding establishing an efficient route towards the development of BN/Mg composite materials with enhanced mechanical properties.

  12. Resource Letter MPF-1: Mechanical Properties of Fluids

    ERIC Educational Resources Information Center

    Stanley, R. C.

    1974-01-01

    Presents an annotated bibliography concerning the mechanical properties of fluids, including topics for use at elementary, secondary, undergraduate, and graduate levels. Indicates that the material can particularly help college physicists in improving course contents in specified fields of physics. (CC)

  13. Ortho-para H₂ conversion by proton exchange at low temperature: an accurate quantum mechanical study.

    PubMed

    Honvault, P; Jorfi, M; González-Lezana, T; Faure, A; Pagani, L

    2011-07-08

    We report extensive, accurate fully quantum, time-independent calculations of cross sections at low collision energies, and rate coefficients at low temperatures for the H⁺ + H₂(v = 0, j) → H⁺ + H₂(v = 0, j') reaction. Different transitions are considered, especially the ortho-para conversion (j = 1 → j' = 0) which is of key importance in astrophysics. This conversion process appears to be very efficient and dominant at low temperature, with a rate coefficient of 4.15 × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹ at 10 K. The quantum mechanical results are also compared with statistical quantum predictions and the reaction is found to be statistical in the low temperature regime (T < 100 K).

  14. Anisotropic mechanical properties of zircon and the effect of radiation damage

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Beirau, Tobias; Nix, William D.; Bismayer, Ulrich

    2016-06-02

    Our study provides new insights into the relationship between radiation-dose-dependent structural damage, due to natural U and Th impurities, and the anisotropic mechanical properties (Poisson s ratio, elastic modulus and hardness) of zircon. Natural zircon samples from Sri Lanka (see Muarakami et al. 1991) and synthetic samples, covering a dose range of zero up to 6.8 x 10 18 -decays/g, have been studied by nanoindentation. Measurements along the [100] crystallographic direction and calculations, based on elastic stiffness constants determined by zkan (1976), revealed a general radiation-induced decrease in stiffness (~ 54 %) and hardness (~ 48 %) and an increasemore » of the Poisson s ratio (~ 54 %) with increasing dose. Additional indentations on selected samples along the [001] allowed one to follow the amorphization process to the point that the mechanical properties are isotropic. This work shows that the radiation-dose-dependent changes of the mechanical properties of zircon can be directly correlated with the amorphous fraction as determined by previous investigations with local and global probes (Rios et al. 2000a; Farnan and Salje 2001; Zhang and Salje 2001). This agreement, revealed by the different methods, indicates a huge influence of structural and even local phenomena on the macroscopic mechanical properties.« less

  15. Simulation and Analysis of Mechanical Properties of Silica Aerogels: From Rationalization to Prediction

    PubMed Central

    Ma, Hao; Zheng, Xiaoyang; Luo, Xuan; Yang, Fan

    2018-01-01

    Silica aerogels are highly porous 3D nanostructures and have exhibited excellent physio-chemical properties. Although silica aerogels have broad potential in many fields, the poor mechanical properties greatly limit further applications. In this study, we have applied the finite volume method (FVM) method to calculate the mechanical properties of silica aerogels with different geometric properties such as particle size, pore size, ligament diameter, etc. The FVM simulation results show that a power law correlation existing between relative density and mechanical properties (elastic modulus and yield stress) of silica aerogels, which are consistent with experimental and literature studies. In addition, depending on the relative densities, different strategies are proposed in order to synthesize silica aerogels with better mechanical performance by adjusting the distribution of pore size and ligament diameter of aerogels. Finally, the results suggest that it is possible to synthesize silica aerogels with ultra-low density as well as high strength and stiffness as long as the textural features are well controlled. It is believed that the FVM simulation methodology could be a valuable tool to study mechanical performance of silica aerogel based materials in the future. PMID:29385745

  16. Simulation and Analysis of Mechanical Properties of Silica Aerogels: From Rationalization to Prediction.

    PubMed

    Ma, Hao; Zheng, Xiaoyang; Luo, Xuan; Yi, Yong; Yang, Fan

    2018-01-30

    Silica aerogels are highly porous 3D nanostructures and have exhibited excellent physio-chemical properties. Although silica aerogels have broad potential in many fields, the poor mechanical properties greatly limit further applications. In this study, we have applied the finite volume method (FVM) method to calculate the mechanical properties of silica aerogels with different geometric properties such as particle size, pore size, ligament diameter, etc. The FVM simulation results show that a power law correlation existing between relative density and mechanical properties (elastic modulus and yield stress) of silica aerogels, which are consistent with experimental and literature studies. In addition, depending on the relative densities, different strategies are proposed in order to synthesize silica aerogels with better mechanical performance by adjusting the distribution of pore size and ligament diameter of aerogels. Finally, the results suggest that it is possible to synthesize silica aerogels with ultra-low density as well as high strength and stiffness as long as the textural features are well controlled. It is believed that the FVM simulation methodology could be a valuable tool to study mechanical performance of silica aerogel based materials in the future.

  17. Moisture effect on mechanical properties of polymeric composite materials

    NASA Astrophysics Data System (ADS)

    Airale, A. G.; Carello, M.; Ferraris, A.; Sisca, L.

    2016-05-01

    The influence of moisture on the mechanical properties of fibre-reinforced polymer matrix composites (PMCs) was investigated. Four materials had been take into account considering: both 2×2-Twill woven carbon fibre or glass fibre, thermosetting matrix (Epoxy Resin) or thermoplastic matrix (Polyphenylene Sulfide). The specimens were submitted for 1800 hours to a hygrothermic test to evaluate moisture absorption on the basis of the Fick's law and finally tested to verify the mechanical properties (ultimate tensile strength). The results showed that the absorbed moisture decreases those properties of composites which were dominated by the matrix or the interface, while was not detectable the influence of water on the considered fibre. An important result is that the diffusion coefficient is highest for glass/PPS and lowest for carbon/epoxy composite material. The results give useful suggestions for the design of vehicle components that are exposed to environmental conditions (rain, snow and humidity).

  18. Mechanical Properties of Unsaturated Polyester / Montmorillonite Composites

    DTIC Science & Technology

    2001-11-01

    Montmorillonite Composites DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the following report: TITLE: Nanophase and...Mechanical Properties of Unsaturated Polyester / Montmorillonite Composites A. Baran Inceoglu and Ulku Yilmazer Middle East Technical University, Chemical...analysed the nature of the curing agent on structure. Kornmann, Berglund and Giannelis [8] studied nanocomposites based on montmorillonite modified

  19. Multi-fidelity machine learning models for accurate bandgap predictions of solids

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pilania, Ghanshyam; Gubernatis, James E.; Lookman, Turab

    Here, we present a multi-fidelity co-kriging statistical learning framework that combines variable-fidelity quantum mechanical calculations of bandgaps to generate a machine-learned model that enables low-cost accurate predictions of the bandgaps at the highest fidelity level. Additionally, the adopted Gaussian process regression formulation allows us to predict the underlying uncertainties as a measure of our confidence in the predictions. In using a set of 600 elpasolite compounds as an example dataset and using semi-local and hybrid exchange correlation functionals within density functional theory as two levels of fidelities, we demonstrate the excellent learning performance of the method against actual high fidelitymore » quantum mechanical calculations of the bandgaps. The presented statistical learning method is not restricted to bandgaps or electronic structure methods and extends the utility of high throughput property predictions in a significant way.« less

  20. Multi-fidelity machine learning models for accurate bandgap predictions of solids

    DOE PAGES

    Pilania, Ghanshyam; Gubernatis, James E.; Lookman, Turab

    2016-12-28

    Here, we present a multi-fidelity co-kriging statistical learning framework that combines variable-fidelity quantum mechanical calculations of bandgaps to generate a machine-learned model that enables low-cost accurate predictions of the bandgaps at the highest fidelity level. Additionally, the adopted Gaussian process regression formulation allows us to predict the underlying uncertainties as a measure of our confidence in the predictions. In using a set of 600 elpasolite compounds as an example dataset and using semi-local and hybrid exchange correlation functionals within density functional theory as two levels of fidelities, we demonstrate the excellent learning performance of the method against actual high fidelitymore » quantum mechanical calculations of the bandgaps. The presented statistical learning method is not restricted to bandgaps or electronic structure methods and extends the utility of high throughput property predictions in a significant way.« less

  1. Physical and Mechanical Properties of Composites and Light Alloys Reinforced with Detonation Nanodiamonds

    NASA Astrophysics Data System (ADS)

    Sakovich, G. V.; Vorozhtsov, S. A.; Vorozhtsov, A. B.; Potekaev, A. I.; Kulkov, S. N.

    2016-07-01

    The influence of introduction of particles of detonation-synthesized nanodiamonds into composites and aluminum-base light alloys on their physical and mechanical properties is analyzed. The data on microstructure and physical and mechanical properties of composites and cast aluminum alloys reinforced with diamond nanoparticles are presented. The introduction of nanoparticles is shown to result in a significant improvement of the material properties.

  2. Mechanical properties and structure evolution of single-crystalline silicon irradiated by 1 MeV Au+ and Cu+ ions

    NASA Astrophysics Data System (ADS)

    Liang, Wei; Zhu, Fei; Ling, Yunhan; Liu, Kezhao; Hu, Yin; Pan, Qifa; Chen, Limin; Zhang, Zhengjun

    2018-05-01

    Mechanical and structural evolutions of single-crystalline silicon irradiated by a series of doses 1 MeV Au+ ions and Cu+ ions are characterized by Surface laser-acoustic wave spectroscopy by (LA wave), Rutherford backscattering spectrometry and channeling (RBS/C) and transmission electron microscopy (TEM). The behavior of implanted Au+ and Cu+ ions was also simulated by using Stopping and range of ions in matter (SRIM) software package, respectively. It is demonstrated that LA wave and RBS could be applied for accurate evaluation of the TEM observed amorphous layer's thickness. The modified mechanical properties depend on the species and the dose of implantation. For 1 MeV Au+ ions, the threshold dose of completely amorphous is 5 × 1014 atoms/cm2, while the one for Cu+ ions is 5 × 1015 atoms/cm2. Upon completely amorphous, the young's modulus and layer density decreased significantly while saturated with the dose increasing sequentially.

  3. Bovine versus Porcine Acellular Dermal Matrix: A Comparison of Mechanical Properties.

    PubMed

    Adelman, David M; Selber, Jesse C; Butler, Charles E

    2014-05-01

    Porcine and bovine acellular dermal matrices (PADM and BADM, respectively) are the most commonly used biologic meshes for ventral hernia repair. A previous study suggests a higher rate of intraoperative device failures using PADM than BADM. We hypothesize that this difference is, in part, related to intrinsic mechanical properties of the matrix substrate and source material. The following study directly compares these 2 matrices to identify any potential differences in mechanical properties that may relate to clinical outcomes. Sections of PADM (Strattice; Lifecell, Branchburg, N.J.) and BADM (SurgiMend; TEI Biosciences, Boston, Mass.) were subjected to a series of biomechanical tests, including suture retention, tear strength, and uniaxial tensile strength. Results were collected and compared statistically. In all parameters, BADM exhibited a superior mechanical strength profile compared with PADM of similar thickness. Increased BADM thickness correlated with increased mechanical strength. In suture tear-through testing with steel wire, failure of the steel wire occurred in the 4-mm-thick BADM, whereas the matrix material failed in all other thicknesses of BADM and PADM. Before implantation, BADM is inherently stronger than PADM at equivalent thicknesses and considerably stronger at increased thicknesses. These results corroborate clinical data from a previous study in which PADM was associated with a higher intraoperative device failure rate. Although numerous properties of acellular dermal matrix contribute to clinical outcomes, surgeons should consider initial mechanical strength properties when choosing acellular dermal matrices for load-bearing applications such as hernia repair.

  4. Effect of cold drawing on mechanical properties of biodegradable fibers.

    PubMed

    La Mantia, Francesco Paolo; Ceraulo, Manuela; Mistretta, Maria Chiara; Morreale, Marco

    2017-01-26

    Biodegradable polymers are currently gaining importance in several fields, because they allow mitigation of the impact on the environment related to disposal of traditional, nonbiodegradable polymers, as well as reducing the utilization of oil-based sources (when they also come from renewable resources). Fibers made of biodegradable polymers are of particular interest, though, it is not easy to obtain polymer fibers with suitable mechanical properties and to tailor these to the specific application. The main ways to tailor the mechanical properties of a given biodegradable polymer fiber are based on crystallinity and orientation control. However, crystallinity can only marginally be modified during processing, while orientation can be controlled, either during hot drawing or cold stretching. In this paper, a systematic investigation of the influence of cold stretching on the mechanical and thermomechanical properties of fibers prepared from different biodegradable polymer systems was carried out. Rheological and thermal characterization helped in interpreting the orientation mechanisms, also on the basis of the molecular structure of the polymer systems. It was found that cold drawing strongly improved the elastic modulus, tensile strength and thermomechanical resistance of the fibers, in comparison with hot-spun fibers. The elastic modulus showed higher increment rates in the biodegradable systems upon increasing the draw ratio.

  5. Mechanical Properties of a Primary Cilium Measured by Resonant Oscillation

    NASA Astrophysics Data System (ADS)

    Resnick, Andrew

    Primary cilia are ubiquitous mammalian cellular substructures implicated in an ever-increasing number of regulatory pathways. The well-established `ciliary hypothesis' states that physical bending of the cilium (for example, due to fluid flow) initiates signaling cascades, yet the mechanical properties of the cilium remain incompletely measured, resulting in confusion regarding the biological significance of flow-induced ciliary mechanotransduction. In this work we measure the mechanical properties of a primary cilium by using an optical trap to induce resonant oscillation of the structure. Our data indicate 1), the primary cilium is not a simple cantilevered beam, 2), the base of the cilium may be modeled as a nonlinear rotatory spring, the linear spring constant `k' of the cilium base calculated to be (4.6 +/- 0.62)*10-12 N/rad and nonlinear spring constant ` α' to be (-1 +/- 0.34) *10-10 N/rad2 , and 3) the ciliary base may be an essential regulator of mechanotransduction signalling. Our method is also particularly suited to measure mechanical properties of nodal cilia, stereocilia, and motile cilia, anatomically similar structures with very different physiological functions.

  6. Mechanical properties of a collagen fibril under simulated degradation.

    PubMed

    Malaspina, David C; Szleifer, Igal; Dhaher, Yasin

    2017-11-01

    Collagen fibrils are a very important component in most of the connective tissue in humans. An important process associated with several physiological and pathological states is the degradation of collagen. Collagen degradation is usually mediated by enzymatic and non-enzymatic processes. In this work we use molecular dynamics simulations to study the influence of simulated degradation on the mechanical properties of the collagen fibril. We applied tensile stress to the collagen fiber at different stages of degradation. We compared the difference in the fibril mechanical priorities due the removal of enzymatic crosslink, surface degradation and volumetric degradation. As anticipated, our results indicated that, regardless of the degradation scenario, fibril mechanical properties is reduced. The type of degradation mechanism (crosslink, surface or volumetric) expressed differential effect on the change in the fibril stiffness. Our simulation results showed dramatic change in the fibril stiffness with a small amount of degradation. This suggests that the hierarchical structure of the fibril is a key component for the toughness and is very sensitive to changes in the organization of the fibril. The overall results are intended to provide a theoretical framework for the understanding the mechanical behavior of collagen fibrils under degradation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Mechanical Properties of Primary Cilia

    NASA Astrophysics Data System (ADS)

    Battle, Christopher; Schmidt, Christoph F.

    2013-03-01

    Recent studies have shown that the primary cilium, long thought to be a vestigial cellular appendage with no function, is involved in a multitude of sensory functions. One example, interesting from both a biophysical and medical standpoint, is the primary cilium of kidney epithelial cells, which acts as a mechanosensitive flow sensor. Genetic defects in ciliary function can cause, e.g., polycystic kidney disease (PKD). The material properties of these non-motile, microtubule-based 9 +0 cilia, and the way they are anchored to the cell cytoskeleton, are important to know if one wants to understand the mechano-electrochemical response of these cells, which is mediated by their cilia. We have probed the mechanical properties, boundary conditions, and dynamics of the cilia of MDCK cells using optical traps and DIC/fluorescence microscopy. We found evidence for both elastic relaxation of the cilia themselves after bending and for compliance in the intracellular anchoring structures. Angular and positional fluctuations of the cilia reflect both thermal excitations and cellular driving forces.

  8. Role of differential physical properties in the collective mechanics and dynamics of tissues

    NASA Astrophysics Data System (ADS)

    Das, Moumita

    Living cells and tissues are highly mechanically sensitive and active. Mechanical stimuli influence the shape, motility, and functions of cells, modulate the behavior of tissues, and play a key role in several diseases. In this talk I will discuss how collective biophysical properties of tissues emerge from the interplay between differential mechanical properties and statistical physics of underlying components, focusing on two complementary tissue types whose properties are primarily determined by (1) the extracellular matrix (ECM), and (2) individual and collective cell properties. I will start with the structure-mechanics-function relationships in articular cartilage (AC), a soft tissue that has very few cells, and its mechanical response is primarily due to its ECM. AC is a remarkable tissue: it can support loads exceeding ten times our body weight and bear 60+ years of daily mechanical loading despite having minimal regenerative capacity. I will discuss the biophysical principles underlying this exceptional mechanical response using the framework of rigidity percolation theory, and compare our predictions with experiments done by our collaborators. Next I will discuss ongoing theoretical work on how the differences in cell mechanics, motility, adhesion, and proliferation in a co-culture of breast cancer cells and healthy breast epithelial cells may modulate experimentally observed differential migration and segregation. Our results may provide insights into the mechanobiology of tissues with cell populations with different physical properties present together such as during the formation of embryos or the initiation of tumors. This work was partially supported by a Cottrell College Science Award.

  9. Mechanical and electrical properties of low density polyethylene filled with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Sabet, Maziyar; Soleimani, Hassan

    2014-08-01

    Carbon nanotubes (CNTs) reveal outstanding electrical and mechanical properties in addition to nanometer scale diameter and high aspect ratio, consequently, making it an ideal reinforcing agent for high strength polymer composites. Low density polyethylene (LDPE)/CNT composites were prepared via melt compounding. Mechanical and electrical properties of (LDPE)/CNT composites with different CNT contents were studied in this research.

  10. Microstructure, Mechanical Properties, and Toughening Mechanisms of a New Hot Stamping-Bake Toughening Steel

    NASA Astrophysics Data System (ADS)

    Lin, Tao; Song, Hong-Wu; Zhang, Shi-Hong; Cheng, Ming; Liu, Wei-Jie; Chen, Yun

    2015-09-01

    In this article, the hot stamping-bake toughening process has been proposed following the well-known concept of bake hardening. The influences of the bake time on the microstructure and the mechanical properties of the hot stamped-baked part were studied by means of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and mechanical tests at room temperature. The results show that the amount of the retained austenite was nearly not changed by the bake process. Also observed were spherical Cu-rich precipitates of about 15 nm in martensite laths. According to the Orowan mechanism, their contribution of the Cu-rich precipitates to the strength is approximately 245 MPa. With the increase of the bake time, the tensile strength of the part was decreased, whereas both the ductility and the product of the tensile strength and ductility were increased then decreased. The tensile strength and ductility product and the tensile strength are as high as 21.9 GPa pct, 2086 MPa, respectively. The excellent combined properties are due to the transformation-induced plasticity effect caused by retained austenite.

  11. Microstructural modification of pure Mg for improving mechanical and biocorrosion properties.

    PubMed

    Ahmadkhaniha, D; Järvenpää, A; Jaskari, M; Sohi, M Heydarzadeh; Zarei-Hanzaki, A; Fedel, M; Deflorian, F; Karjalainen, L P

    2016-08-01

    In this study, the effect of microstructural modification on mechanical properties and biocorrosion resistance of pure Mg was investigated for tailoring a load-bearing orthopedic biodegradable implant material. This was performed utilizing the friction stir processing (FSP) in 1-3 passes to refine the grain size. Microstructure was examined in an optical microscope and scanning electron microscope with an electron backscatter diffraction unit. X-ray diffraction method was used to identify the texture. Mechanical properties were measured by microhardness and tensile testing. Electrochemical impedance spectroscopy was applied to evaluate corrosion behavior. The results indicate that even applying a single pass of FSP refined the grain size significantly. Increasing the number of FSP passes further refined the structure, increased the mechanical strength and intensified the dominating basal texture. The best combination of mechanical properties and corrosion resistance were achieved after three FSP passes. In this case, the yield strength was about six times higher than that of the as-cast Mg and the corrosion resistance was also improved compared to that in the as-cast condition. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Mechanical properties of dental resin/composite containing urchin-like hydroxyapatite.

    PubMed

    Liu, Fengwei; Sun, Bin; Jiang, Xiaoze; Aldeyab, Sultan S; Zhang, Qinghong; Zhu, Meifang

    2014-12-01

    To investigate the reinforcing effect of urchin-like hydroxyapatite (UHA) in bisphenol A glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) dental resin (without silica nanoparticles) and dental composites (with silica nanoparticles), and explore the effect of HA filler morphologies and loadings on the mechanical properties. UHA was synthesized by a facile method of microwave irradiation and studied by X-ray diffraction (XRD), scanning electron microscope (SEM), and thermogravimetric analysis (TGA). Mechanical properties of the dental resin composites containing silanized UHA were tested by a universal mechanical testing machine. Analysis of variance was used for the statistical analysis of the acquired data. The fracture morphologies of tested composites were observed by SEM. Composites with silanized irregular particulate hydroxyapatite (IPHA) and hydroxyapatite whisker (HW) were prepared for comparative studies. Impregnation of lower loadings (5 wt% and 10 wt%) of silanized UHA into dental resin (without silica nanoparticles) substantially improved the mechanical properties; higher UHA loadings (20 wt% and 30 wt%) of impregnation continuously improved the flexural modulus and microhardness, while the strength would no longer be increased. Compared with silanized IPHA and HW, silanized UHA consisting of rods extending radially from center were embedded into the matrix closely and well dispersed in the composite, increasing filler-matrix interfacial contact area and combination. At higher filler loadings, UHA interlaced together tightly without affecting the mobility of monomer inside, which might bear higher loads during fracture of the composite, leading to higher strengths than those of dental resins with IPHA and HW. Besides, impregnation of silanized UHA into dental composites (with silica nanoparticles) significantly improved the strength and modulus. UHA could serve as novel reinforcing HA filler to improve the mechanical properties

  13. Atomistic modeling of mechanical properties of polycrystalline graphene.

    PubMed

    Mortazavi, Bohayra; Cuniberti, Gianaurelio

    2014-05-30

    We performed molecular dynamics (MD) simulations to investigate the mechanical properties of polycrystalline graphene. By constructing molecular models of ultra-fine-grained graphene structures, we studied the effect of different grain sizes of 1-10 nm on the mechanical response of graphene. We found that the elastic modulus and tensile strength of polycrystalline graphene decrease with decreasing grain size. The calculated mechanical proprieties for pristine and polycrystalline graphene sheets are found to be in agreement with experimental results in the literature. Our MD results suggest that the ultra-fine-grained graphene structures can show ultrahigh tensile strength and elastic modulus values that are very close to those of pristine graphene sheets.

  14. Effects of Zoledronate and Mechanical Loading during Simulated Weightlessness on Bone Structure and Mechanical Properties

    NASA Technical Reports Server (NTRS)

    Scott, R. T.; Nalavadi, M. O.; Shirazi-Fard, Y.; Castillo, A. B.; Alwood, J. S.

    2016-01-01

    Space flight modulates bone remodeling to favor bone resorption. Current countermeasures include an anti-resorptive drug class, bisphosphonates (BP), and high-force loading regimens. Does the combination of anti-resorptives and high-force exercise during weightlessness have negative effects on the mechanical and structural properties of bone? In this study, we implemented an integrated model to mimic mechanical strain of exercise via cyclical loading (CL) in mice treated with the BP Zoledronate (ZOL) combined with hindlimb unloading (HU). Our working hypothesis is that CL combined with ZOL in the HU model induces additive structural and mechanical changes. Thirty-two C57BL6 mice (male,16 weeks old, n8group) were exposed to 3 weeks of either HU or normal ambulation (NA). Cohorts of mice received one subcutaneous injection of ZOL (45gkg), or saline vehicle, prior to experiment. The right tibia was axially loaded in vivo, 60xday to 9N in compression, repeated 3xweek during HU. During the application of compression, secant stiffness (SEC), a linear estimate of slope of the force displacement curve from rest (0.5N) to max load (9.0N), was calculated for each cycle once per week. Ex vivo CT was conducted on all subjects. For ex vivo mechanical properties, non-CL left femurs underwent 3-point bending. In the proximal tibial metaphysis, HU decreased, CL increased, and ZOL increased the cancellous bone volume to total volume ratio by -26, +21, and +33, respectively. Similar trends held for trabecular thickness and number. Ex vivo left femur mechanical properties revealed HU decreased stiffness (-37),and ZOL mitigated the HU stiffness losses (+78). Data on the ex vivo Ultimate Force followed similar trends. After 3 weeks, HU decreased in vivo SEC (-16). The combination of CL+HU appeared additive in bone structure and mechanical properties. However, when HU + CL + ZOL were combined, ZOL had no additional effect (p0.05) on in vivo SEC. Structural data followed this trend with

  15. Mechanical properties of cement concrete composites containing nano-metakaolin

    NASA Astrophysics Data System (ADS)

    Supit, Steve Wilben Macquarie; Rumbayan, Rilya; Ticoalu, Adriana

    2017-11-01

    The use of nano materials in building construction has been recognized because of its high specific surface area, very small particle sizes and more amorphous nature of particles. These characteristics lead to increase the mechanical properties and durability of cement concrete composites. Metakaolin is one of the supplementary cementitious materials that has been used to replace cement in concrete. Therefore, it is interesting to investigate the effectiveness of metakaolin (in nano scale) in improving the mechanical properties including compressive strength, tensile strength and flexural strength of cement concretes. In this experiment, metakaolin was pulverized by using High Energy Milling before adding to the concrete mixes. The pozzolan Portland cement was replaced with 5% and 10% nano-metakaolin (by wt.). The result shows that the optimum amount of nano-metakaolin in cement concrete mixes is 10% (by wt.). The improvement in compressive strength is approximately 123% at 3 days, 85% at 7 days and 53% at 28 days, respectively. The tensile and flexural strength results also showed the influence of adding 10% nano-metakaolin (NK-10) in improving the properties of cement concrete (NK-0). Furthermore, the Backscattered Electron images and X-Ray Diffraction analysis were evaluated to support the above findings. The results analysis confirm the pores modification due to nano-metakaolin addition, the consumption of calcium hydroxide (CH) and the formation of Calcium Silicate Hydrate (CSH) gel as one of the beneficial effects of amorphous nano-metakaolin in improving the mechanical properties and densification of microstructure of mortar and concrete.

  16. Multiscale mechanisms of nutritionally induced property variation in spider silks

    PubMed Central

    Nobbs, Madeleine; Martens, Penny J.; Tso, I-Min; Chuang, Wei-Tsung; Chang, Chung-Kai; Sheu, Hwo-Shuenn

    2018-01-01

    Variability in spider major ampullate (MA) silk properties at different scales has proven difficult to determine and remains an obstacle to the development of synthetic fibers mimicking MA silk performance. A multitude of techniques may be used to measure multiscale aspects of silk properties. Here we fed five species of Araneoid spider solutions that either contained protein or were protein deprived and performed silk tensile tests, small and wide-angle X-ray scattering (SAXS/WAXS), amino acid composition analyses, and silk gene expression analyses, to resolve persistent questions about how nutrient deprivation induces variations in MA silk mechanical properties across scales. Our analyses found that the properties of each spider’s silk varied differently in response to variations in their protein intake. We found changes in the crystalline and non-crystalline nanostructures to play specific roles in inducing the property variations we found. Across treatment MaSp expression patterns differed in each of the five species. We found that in most species MaSp expression and amino acid composition variations did not conform with our predictions based on a traditional MaSp expression model. In general, changes to the silk’s alanine and proline compositions influenced the alignment of the proteins within the silk’s amorphous region, which influenced silk extensibility and toughness. Variations in structural alignment in the crystalline and non-crystalline regions influenced ultimate strength independent of genetic expression. Our study provides the deepest insights thus far into the mechanisms of how MA silk properties vary from gene expression to nanostructure formations to fiber mechanics. Such knowledge is imperative for promoting the production of synthetic silk fibers. PMID:29390013

  17. Multiscale mechanisms of nutritionally induced property variation in spider silks.

    PubMed

    Blamires, Sean J; Nobbs, Madeleine; Martens, Penny J; Tso, I-Min; Chuang, Wei-Tsung; Chang, Chung-Kai; Sheu, Hwo-Shuenn

    2018-01-01

    Variability in spider major ampullate (MA) silk properties at different scales has proven difficult to determine and remains an obstacle to the development of synthetic fibers mimicking MA silk performance. A multitude of techniques may be used to measure multiscale aspects of silk properties. Here we fed five species of Araneoid spider solutions that either contained protein or were protein deprived and performed silk tensile tests, small and wide-angle X-ray scattering (SAXS/WAXS), amino acid composition analyses, and silk gene expression analyses, to resolve persistent questions about how nutrient deprivation induces variations in MA silk mechanical properties across scales. Our analyses found that the properties of each spider's silk varied differently in response to variations in their protein intake. We found changes in the crystalline and non-crystalline nanostructures to play specific roles in inducing the property variations we found. Across treatment MaSp expression patterns differed in each of the five species. We found that in most species MaSp expression and amino acid composition variations did not conform with our predictions based on a traditional MaSp expression model. In general, changes to the silk's alanine and proline compositions influenced the alignment of the proteins within the silk's amorphous region, which influenced silk extensibility and toughness. Variations in structural alignment in the crystalline and non-crystalline regions influenced ultimate strength independent of genetic expression. Our study provides the deepest insights thus far into the mechanisms of how MA silk properties vary from gene expression to nanostructure formations to fiber mechanics. Such knowledge is imperative for promoting the production of synthetic silk fibers.

  18. CRITICAL MECHANICAL PROPERTIES OF STRUCTURAL LIGHT-WEIGHT CONCRETE AND THE EFFECTS OF THESE PROPERTIES ON THE DESIGN OF THE PAVEMENT STRUCTURE.

    DOT National Transportation Integrated Search

    1965-01-01

    In this study, critical mechanical properties of structural lightweight concrete were determined and utilized in the evaluation of a design of concrete pavements. Also presented are the critical mechanical properties resulting from unrestrained and r...

  19. Improving the mechanical properties of nano-hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Khanal, Suraj Prasad

    Hydroxyapatite (HAp) is an ideal bioactive material that is used in orthopedics. Chemical composition and crystal structure properties of HAp are similar to the natural bone hence it promotes bone growth. However, its mechanical properties of synthetic HAp are not sufficient for major load-bearing bone replacement. The potential of improving the mechanical properties of synthetic hydroxyapatite (HAp) by incorporating carboxyl functionalized single walled carbon nanotubes (CfSWCNT) and polymerized epsilon-caprolactam (nylon) is studied. The fracture toughness, tensile strength, Young's modulus, stiffness and fracture energy were studied for a series of HAp samples with CfSWCNT concentrations varying from 0 to 1.5 wt. % without, and with nylon addition. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) were used to characterize the samples. The fracture toughness and tensile test was performed under the standard protocol of ASTM D5045 and ASTM D638-02a respectively. Reproducible maximum values of (3.60 +/- 0.3) MPa.m1/2 for fracture toughness and 65.38 MPa for tensile strength were measured for samples containing 1 wt. % CfSWCNT and nylon. The Young's modulus, stiffness and fracture energy of the samples are 10.65 GPa, 1482.12 N/mm, and 644 J/m2 respectively. These values are comparable to those of the cortical bone. Further increase of the CfSWCNT content results to a decreased fracture toughness and tensile strength and formation of a secondary phase.

  20. First-principles investigation of mechanical properties of silicene, germanene and stanene

    NASA Astrophysics Data System (ADS)

    Mortazavi, Bohayra; Rahaman, Obaidur; Makaremi, Meysam; Dianat, Arezoo; Cuniberti, Gianaurelio; Rabczuk, Timon

    2017-03-01

    Two-dimensional allotropes of group-IV substrates including silicene, germanene and stanene have recently attracted considerable attention in nanodevice fabrication industry. These materials involving the buckled structure have been experimentally fabricated lately. In this study, first-principles density functional theory calculations were utilized to investigate the mechanical properties of single-layer and free-standing silicene, germanene and stanene. Uniaxial tensile and compressive simulations were carried out to probe and compare stress-strain properties; such as the Young's modulus, Poisson's ratio and ultimate strength. We evaluated the chirality effect on the mechanical response and bond structure of the 2D substrates. Our first-principles simulations suggest that in all studied samples application of uniaxial loading can alter the electronic nature of the buckled structures into the metallic character. Our investigation provides a general but also useful viewpoint with respect to the mechanical properties of silicene, germanene and stanene.

  1. Microstructural evolution and mechanical properties of SnAgCu alloys

    NASA Astrophysics Data System (ADS)

    Fouassier, O.; Heintz, J.-M.; Chazelas, J.; Geffroy, P.-M.; Silvain, J.-F.

    2006-08-01

    Lead containing solder paste is now considered as an environmental threat. In order to eliminate this undesirable environmental impact associated to their production, a family of lead-free solder joint, Sn-3.8Ag-0.7Cu, is proposed. Microstructural and mechanical data of this solder joint have been acquired and compared with the most common used SnPb solder paste. The evolution of the microstructure as well as the failure mode and the mechanical properties of SnAgCu solder joint are discussed as a function of strain rate, annealing treatments, and testing temperature. Tensile tests have been performed, at temperatures ranging from -50to+150°C, on bulk samples. Changes of the mechanical properties of bulk tested samples are actually correlated with microstructural changes, as shown by transmission electronic microscopy investigations.

  2. Quantitative ultrasonic evaluation of mechanical properties of engineering materials

    NASA Technical Reports Server (NTRS)

    Vary, A.

    1978-01-01

    Current progress in the application of ultrasonic techniques to nondestructive measurement of mechanical strength properties of engineering materials is reviewed. Even where conventional NDE techniques have shown that a part is free of overt defects, advanced NDE techniques should be available to confirm the material properties assumed in the part's design. There are many instances where metallic, composite, or ceramic parts may be free of critical defects while still being susceptible to failure under design loads due to inadequate or degraded mechanical strength. This must be considered in any failure prevention scheme that relies on fracture analysis. This review will discuss the availability of ultrasonic methods that can be applied to actual parts to assess their potential susceptibility to failure under design conditions.

  3. Changes in pelvic organ prolapse mesh mechanical properties following implantation in rats.

    PubMed

    Ulrich, Daniela; Edwards, Sharon L; Alexander, David L J; Rosamilia, Anna; Werkmeister, Jerome A; Gargett, Caroline E; Letouzey, Vincent

    2016-02-01

    Pelvic organ prolapse (POP) is a multifactorial disease that manifests as the herniation of the pelvic organs into the vagina. Surgical methods for prolapse repair involve the use of a synthetic polypropylene mesh. The use of this mesh has led to significantly higher anatomical success rates compared with native tissue repairs, and therefore, despite recent warnings by the Food and Drug Administration regarding the use of vaginal mesh, the number of POP mesh surgeries has increased over the last few years. However, mesh implantation is associated with higher postsurgery complications, including pain and erosion, with higher consecutive rates of reoperation when placed vaginally. Little is known on how the mechanical properties of the implanted mesh itself change in vivo. It is assumed that the mechanical properties of these meshes remain unchanged, with any differences in mechanical properties of the formed mesh-tissue complex attributed to the attached tissue alone. It is likely that any changes in mesh mechanical properties that do occur in vivo will have an impact on the biomechanical properties of the formed mesh-tissue complex. The objective of the study was to assess changes in the multiaxial mechanical properties of synthetic clinical prolapse meshes implanted abdominally for up to 90 days, using a rat model. Another objective of the study was to assess the biomechanical properties of the formed mesh-tissue complex following implantation. Three nondegradable polypropylene clinical synthetic mesh types for prolapse repair (Gynemesh PS, Polyform Lite, and Restorelle) and a partially degradable polypropylene/polyglecaprone mesh (UltraPro) were mechanically assessed before and after implantation (n = 5/ mesh type) in Sprague Dawley rats for 30 (Gynemesh PS, Polyform Lite, and Restorelle) and 90 (UltraPro and Polyform Lite) days. Stiffness and permanent extension following cyclic loading, and breaking load, of the preimplanted mesh types, explanted mesh

  4. Relationship between critical mechanical properties and age for structural lightweight concrete.

    DOT National Transportation Integrated Search

    1964-02-25

    The necessity to use structural lightweight concrete has created : a need for investigations into its critical mechanical properties that : affect the design and performance of structures. The primary critical : properties were found to be direct ten...

  5. Advanced Ceramics Property Measurements

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan; Helfinstine, John; Quinn, George; Gonczy, Stephen

    2013-01-01

    Mechanical and physical properties of ceramic bodies can be difficult to measure correctly unless the proper techniques are used. The Advanced Ceramics Committee of ASTM, C-28, has developed dozens of consensus test standards and practices to measure various properties of a ceramic monolith, composite, or coating. The standards give the "what, how, how not, and why" for measurement of many mechanical, physical, thermal, and performance properties. Using these standards will provide accurate, reliable, and complete data for rigorous comparisons with other test results from your test lab, or another. The C-28 Committee has involved academics, producers, and users of ceramics to write and continually update more than 45 standards since the committee's inception in 1986. Included in this poster is a pictogram of the C-28 standards and information on how to obtain individual copies with full details or the complete collection of standards in one volume.

  6. Nanocrystalline CuNi alloys: improvement of mechanical properties and thermal stability

    NASA Astrophysics Data System (ADS)

    Nogues, Josep; Varea, A.; Pellicer, E.; Sivaraman, K. M.; Pane, S.; Nelson, B. J.; Surinach, S.; Baro, M. D.; Sort, J.

    2014-03-01

    Nanocrystalline metallic films are known to benefit from novel and enhanced physical and chemical properties. In spite of these outstanding properties, nanocrystalline metals typically show relatively poor thermal stability which leads to deterioration of the properties due to grain coarsening. We have studied nanocrystalline Cu1-xNix (0.56 < x < 1) thin films (3 μm-thick) electrodeposited galvanostatically onto Cu/Ti/Si (100) substrates. CuNi thin films exhibit large values of hardness (6.15 < H < 7.21 GPa), which can be tailored by varying the composition. However, pure Ni films (x = 1) suffer deterioration of their mechanical and magnetic properties after annealing during 3 h at relatively low temperatures (TANN > 475 K) due to significant grain growth. Interestingly, alloying Ni with Cu clearly improves the thermal stability of the material because grain coarsening is delayed due to segregation of a Cu-rich phase at grain boundaries, thus preserving both the mechanical and magnetic properties up to higher TANN.

  7. Anisotropic mechanical properties of zircon and the effect of radiation damage

    NASA Astrophysics Data System (ADS)

    Beirau, Tobias; Nix, William D.; Bismayer, Ulrich; Boatner, Lynn A.; Isaacson, Scott G.; Ewing, Rodney C.

    2016-10-01

    This study provides new insights into the relationship between radiation-dose-dependent structural damage due to natural U and Th impurities and the anisotropic mechanical properties (Poisson's ratio, elastic modulus and hardness) of zircon. Natural zircon samples from Sri Lanka (see Muarakami et al. in Am Mineral 76:1510-1532, 1991) and synthetic samples, covering a dose range of zero up to 6.8 × 1018 α-decays/g, have been studied by nanoindentation. Measurements along the [100] crystallographic direction and calculations, based on elastic stiffness constants determined by Özkan (J Appl Phys 47:4772-4779, 1976), revealed a general radiation-induced decrease in stiffness (~54 %) and hardness (~48 %) and an increase in the Poisson's ratio (~54 %) with increasing dose. Additional indentations on selected samples along the [001] allowed one to follow the amorphization process to the point that the mechanical properties are isotropic. This work shows that the radiation-dose-dependent changes of the mechanical properties of zircon can be directly correlated with the amorphous fraction as determined by previous investigations with local and global probes (Ríos et al. in J Phys Condens Matter 12:2401-2412, 2000a; Farnan and Salje in J Appl Phys 89:2084-2090, 2001; Zhang and Salje in J Phys Condens Matter 13:3057-3071, 2001). The excellent agreement, revealed by the different methods, indicates a large influence of structural and even local phenomena on the macroscopic mechanical properties. Therefore, this study indicates the importance of acquiring better knowledge about the mechanical long-term stability of radiation-damaged materials.

  8. Mechanical properties of niobium radio-frequency cavities

    DOE PAGES

    Ciovati, Gianluigi; Dhakal, Pashupati; Matalevich, Joseph R.; ...

    2015-07-02

    Radio-frequency cavities made of bulk niobium are one of the components used in modern particle accelerators. The mechanical stability is an important aspect of cavity design, which typically relies on finite-element analysis simulations using material properties from tensile tests on sample. This contribution presents the results of strain and resonant frequency measurements as a function of a uniform pressure up to 722 kPa, applied to single-cell niobium cavities with different crystallographic structure, purity and treatments. In addition, burst tests of high-purity multi-cell cavities with different crystallographic structure have been conducted up to the tensile strength of the material. Finite-element analysismore » of the single-cell cavity geometry is in good agreement with the observed behavior in the elastic regime assuming a Young's modulus value of 88.5 GPa and a Poisson's ratio of 0.4, regardless of crystallographic structure, purity or treatment. However, the measured yield strength and tensile strength depend on crystallographic structure, material purity and treatment. In particular, the results from this study show that the mechanical properties of niobium cavities with large crystals are comparable to those of cavities made of fine-grain niobium.« less

  9. Mechanical properties of asthmatic airway smooth muscle.

    PubMed

    Chin, Leslie Y M; Bossé, Ynuk; Pascoe, Chris; Hackett, Tillie L; Seow, Chun Y; Paré, Peter D

    2012-07-01

    Airway smooth muscle (ASM) is the major effector of excessive airway narrowing in asthma. Changes in some of the mechanical properties of ASM could contribute to excessive narrowing and have not been systematically studied in human ASM from nonasthmatic and asthmatic subjects. Human ASM strips (eight asthmatic and six nonasthmatic) were studied at in situ length and force was normalised to maximal force induced by electric field stimulation (EFS). Measurements included: passive and active force versus length before and after length adaptation, the force-velocity relationship, maximal shortening and force recovery after length oscillation. Force was converted to stress by dividing by cross-sectional area of muscle. The only functional differences were that the asthmatic tissue was stiffer at longer lengths (p<0.05) and oscillatory strain reduced isometric force in response to EFS by 19% as opposed to 36% in nonasthmatics (p<0.01). The mechanical properties of human ASM from asthmatic and nonasthmatic subjects are comparable except for increased passive stiffness and attenuated decline in force generation after an oscillatory perturbation. These data may relate to reduced bronchodilation induced by a deep inspiration in asthmatic subjects.

  10. Evaluation of consolidation method on mechanical and structural properties of ODS RAF steel

    NASA Astrophysics Data System (ADS)

    Frelek-Kozak, M.; Kurpaska, L.; Wyszkowska, E.; Jagielski, J.; Jozwik, I.; Chmielewski, M.

    2018-07-01

    In the present work, the effects of the fabrication method on mechanical and structural properties of 12%Cr, 2%W, 0.25%Ti, 0.25%Y2O3 steels were investigated. Materials obtained by Spark Plasma Sintering (SPS), Hot Isostatic Pressing (HIP) and Hot Extrusion (HE) methods were studied. The microstructure was characterized by using Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction analysis (EBSD). Mechanical properties of the studied samples were evaluated by using Vickers micro hardness HV0.1, Small Punch Test (SPT) and nanoindentation (NI) methods. The analysis revealed that samples manufactured via HIP and SPS processes exhibit very similar properties, whereas SPS method produces material with slightly lower hardness. In addition, significantly lower mechanical properties of the specimens after HE process were observed. The study described in this article addresses also the problems of mechanical parameters measured in micro- and nano-scale experiments and aims to identify possible pitfalls related to the use of various manufacturing technologies.

  11. Mechanical properties of turbine blade alloys in hydrogen at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Deluca, D. P.

    1981-01-01

    The mechanical properties of single crystal turbine blade alloys in a gaseous hydrogen environment were determined. These alloys are proposed for use in space propulsion systems in pure or partial high pressure hydrogen environments at elevated temperatures. Mechanical property tests included: tensile, creep, low fatigue (LCF), and crack growth. Specimens were in both transverse and longitudinal directions relative to the casting solidification direction. Testing was conducted on solid specimens exposed to externally pressurized environments of gaseous hydrogen and hydrogen-enriched steam.

  12. Dynamic and mechanical properties of supported lipid bilayers

    NASA Astrophysics Data System (ADS)

    Wu, Hsing-Lun; Tsao, Heng-Kwong; Sheng, Yu-Jane

    2016-04-01

    Supported lipid bilayers (SLBs) offer an excellent model system for investigating the physico-chemical properties of the cell membrane. In this work, dynamic and mechanical properties of SLBs are explored by dissipative particle dynamics simulations for lipids with different architectures (chain length, kink, and asymmetry associated with lipid tails). It is found that the lateral diffusivity (Dx) and flip-flop rate (FF) grow with increasing temperature in both gel and liquid phases and can be described by an Arrhenius-like expression. Three regimes can be clearly identified for symmetric and asymmetric saturated lipids but only two regimes are observed for kinked lipids. Both Dx and FF grow with decreasing tail length and increasing number of kinks. The stretching (KA) and apparent bending (KB) moduli exhibit concave upward curves with temperature and the minima are attained at Tm. In general, the minima of KA and KB decrease with the chain length and increase with number of kinks. The typical relation among the bending modulus, area stretching modulus, and bilayer thickness is still followed, KB = βKAh2 and β is much smaller in the gel phase. The dynamic and mechanical properties of lipids with asymmetric tails are found to situate between their symmetric counterparts.

  13. Correlating P-wave Velocity with the Physico-Mechanical Properties of Different Rocks

    NASA Astrophysics Data System (ADS)

    Khandelwal, Manoj

    2013-04-01

    In mining and civil engineering projects, physico-mechanical properties of the rock affect both the project design and the construction operation. Determination of various physico-mechanical properties of rocks is expensive and time consuming, and sometimes it is very difficult to get cores to perform direct tests to evaluate the rock mass. The purpose of this work is to investigate the relationships between the different physico-mechanical properties of the various rock types with the P-wave velocity. Measurement of P-wave velocity is relatively cheap, non-destructive and easy to carry out. In this study, representative rock mass samples of igneous, sedimentary, and metamorphic rocks were collected from the different locations of India to obtain an empirical relation between P-wave velocity and uniaxial compressive strength, tensile strength, punch shear, density, slake durability index, Young's modulus, Poisson's ratio, impact strength index and Schmidt hammer rebound number. A very strong correlation was found between the P-wave velocity and different physico-mechanical properties of various rock types with very high coefficients of determination. To check the sensitivity of the empirical equations, Students t test was also performed, which confirmed the validity of the proposed correlations.

  14. Protocol dependence of mechanical properties in granular systems.

    PubMed

    Inagaki, S; Otsuki, M; Sasa, S

    2011-11-01

    We study the protocol dependence of the mechanical properties of granular media by means of computer simulations. We control a protocol of realizing disk packings in a systematic manner. In 2D, by keeping material properties of the constituents identical, we carry out compaction with various strain rates. The disk packings exhibit the strain rate dependence of the critical packing fraction above which the pressure becomes non-zero. The observed behavior contrasts with the well-studied jamming transitions for frictionless disk packings. We also observe that the elastic moduli of the disk packings depend on the strain rate logarithmically. Our results suggest that there exists a time-dependent state variable to describe macroscopic material properties of disk packings, which depend on its protocol.

  15. Acoustic and mechanical properties of renal calculi: implications in shock wave lithotripsy.

    PubMed

    Chuong, C J; Zhong, P; Preminger, G M

    1993-12-01

    The acoustic and mechanical properties of renal calculi dictate how a stone interacts with the mechanical forces produced by shock wave lithotripsy; thus, these properties are directly related to the success of the treatment. Using an ultrasound pulse transmission technique, we measured both longitudinal and transverse (or shear) wave propagation speeds in nine groups of renal calculi with different chemical compositions. We also measured stone density using a pycnometer based on Archimedes' principle. From these measurements, we calculated wave impedance and dynamic mechanical properties of the renal stones. Calcium oxalate monohydrate and cystine stones had higher longitudinal and transverse wave speeds, wave impedances, and dynamic moduli (bulk modulus, Young's modulus, and shear modulus), suggesting that these stones are more difficult to fragment. Phosphate stones (carbonate apatite and magnesium ammonium phosphate hydrogen) were found to have lower values of these properties, suggesting they are more amenable to shock wave fragmentation. These data provide a physical explanation for the significant differences in stone fragility observed clinically.

  16. Mechanical properties of cancellous bone in the human mandibular condyle are anisotropic.

    PubMed

    Giesen, E B; Ding, M; Dalstra, M; van Eijden, T M

    2001-06-01

    The objective of the present study was (1) to test the hypothesis that the elastic and failure properties of the cancellous bone of the mandibular condyle depend on the loading direction, and (2) to relate these properties to bone density parameters. Uniaxial compression tests were performed on cylindrical specimens (n=47) obtained from the condyles of 24 embalmed cadavers. Two loading directions were examined, i.e., a direction coinciding with the predominant orientation of the plate-like trabeculae (axial loading) and a direction perpendicular to the plate-like trabeculae (transverse loading). Archimedes' principle was applied to determine bone density parameters. The cancellous bone was in axial loading 3.4 times stiffer and 2.8 times stronger upon failure than in transverse loading. High coefficients of correlation were found among the various mechanical properties and between them and the apparent density and volume fraction. The anisotropic mechanical properties can possibly be considered as a mechanical adaptation to the loading of the condyle in vivo.

  17. Thermal and Mechanical Property Characterization of the Advanced Disk Alloy LSHR

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Gayda, John; Telesman, Jack; Kantzos, Peter T.

    2005-01-01

    A low solvus, high refractory (LSHR) powder metallurgy disk alloy was recently designed using experimental screening and statistical modeling of composition and processing variables on sub-scale disks to have versatile processing-property capabilities for advanced disk applications. The objective of the present study was to produce a scaled-up disk and apply varied heat treat processes to enable full-scale demonstration of LSHR properties. Scaled-up disks were produced, heat treated, sectioned, and then machined into specimens for mechanical testing. Results indicate the LSHR alloy can be processed to produce fine and coarse grain microstructures with differing combinations of strength and time-dependent mechanical properties, for application at temperatures exceeding 1300 F.

  18. Mechanical and electronic properties of Janus monolayer transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Shi, Wenwu; Wang, Zhiguo

    2018-05-01

    The mechanical and electronic properties of Janus monolayer transition metal dichalcogenides MXY (M  =  Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W; X/Y  =  S, Se, Te) were investigated using density functional theory. Results show that breaking the out-of-plane structural symmetry can be used to tune the electronic and mechanical behavior of monolayer transition metal dichalcogenides. The band gaps of monolayer WXY and MoXY are in the ranges of 0.16–1.91 and 0.94–1.69 eV, respectively. A semiconductor to metallic phase transition occurred in Janus monolayer MXY (M  =  Ti, Zr and Hf). The monolayers MXY (M  =  V, Nb, Ta and Cr) show metallic characteristics, which show no dependence on the structural symmetry breaking. The mechanical properties of MXY depended on the composition. Monolayer MXY (M  =  Mo, Ti, Zr, Hf and W) showed brittle characteristic, whereas monolayer CrXY and VXY are with ductile characteristic. The in-plane stiffness of pristine and Janus monolayer MXY are in the range between 22 and 158 N m‑1. The tunable electronic and mechanical properties of these 2D materials would advance the development of ultra-sensitive detectors, nanogenerators, low-power electronics, and energy harvesting and electromechanical systems.

  19. Recent advances in small-scale mechanical property measurement by nanoindentation

    DOE PAGES

    Pharr, George Mathews

    2015-08-25

    Since its initial development in the early 1980’s [1], nanoindentation has matured into one of the premier testing techniques for measuring mechanical properties at the micrometer and sub-micrometer scales and has emerged as a critical tool that has helped to shape the nanotechnology revolution. At the heart of the technique are testing systems with simple but precise force actuators and displacement measuring devices that record the force–displacement record as a diamond indenter, usually the form of a pyramid or a sphere, is pressed into and withdrawn from a small region in the surface of a material of interest. The nano-scalemore » force–displacement data, which can be obtained with a spatial resolution as small as a few nanometers, contains a wealth of information about the local mechanical properties [2], [3] and [4]. This enables the mechanical characterization of very thin films, like those used in the semiconductor, magnetic storage, and hard coatings industries, as well as very small precipitates, particles and second phases, many of which may not exist in bulk form and cannot be characterized by traditional mechanical testing methods. Here, computer automation of nanoindentation testing systems now routinely provides for complete two-dimensional mapping of properties over regions stretching from sub-micron to millimeters in scale.« less

  20. Local mechanical properties of LFT injection molded parts: Numerical simulations versus experiments

    NASA Astrophysics Data System (ADS)

    Desplentere, F.; Soete, K.; Bonte, H.; Debrabandere, E.

    2014-05-01

    In predictive engineering for polymer processes, the proper prediction of material microstructure from known processing conditions and constituent material properties is a critical step forward properly predicting bulk properties in the finished composite. Operating within the context of long-fiber thermoplastics (LFT, length < 15mm) this investigation concentrates on the prediction of the local mechanical properties of an injection molded part. To realize this, the Autodesk Simulation Moldflow Insight 2014 software has been used. In this software, a fiber breakage algorithm for the polymer flow inside the mold is available. Using well known micro mechanic formulas allow to combine the local fiber length with the local orientation into local mechanical properties. Different experiments were performed using a commercially available glass fiber filled compound to compare the measured data with the numerical simulation results. In this investigation, tensile tests and 3 point bending tests are considered. To characterize the fiber length distribution of the polymer melt entering the mold (necessary for the numerical simulations), air shots were performed. For those air shots, similar homogenization conditions were used as during the injection molding tests. The fiber length distribution is characterized using automated optical method on samples for which the matrix material is burned away. Using the appropriate settings for the different experiments, good predictions of the local mechanical properties are obtained.

  1. Enhanced mechanical and thermal properties of regenerated cellulose/graphene composite fibers.

    PubMed

    Tian, Mingwei; Qu, Lijun; Zhang, Xiansheng; Zhang, Kun; Zhu, Shifeng; Guo, Xiaoqing; Han, Guangting; Tang, Xiaoning; Sun, Yaning

    2014-10-13

    In this study, a wet spinning method was applied to fabricate regenerated cellulose fibers filled with low graphene loading which was systematically characterized by SEM, TEM, FTIR and XRD techniques. Subsequently, the mechanical and thermal properties of the resulting fibers were investigated. With only 0.2 wt% loading of graphene, a ∼ 50% improvement of tensile strength and 25% enhancement of Young's modulus were obtained and the modified Halpin-Tsai model was built to predict the mechanical properties of composite fibers. Thermal analysis of the composite fibers showed remarkably enhanced thermal stability and dynamic heat transfer performance of graphene-filled cellulose composite fiber, also, the presence of graphene oxide can significantly enhance the thermal conductivity of the composite fiber. This work provided a facile way to improve mechanical and thermal properties of regenerated cellulose fibers. The resultant composite fibers have potential application in thermal insulation and reinforced fibrous materials. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. A critical evaluation of the enhancement of mechanical properties of epoxy modified using CNTs

    NASA Astrophysics Data System (ADS)

    Bedsole, Robert W.; Park, Cheol; Bogert, Philip B.; Tippur, Hareesh V.

    2015-09-01

    Carbon nanotubes (CNTs) have been widely shown in the literature to improve mechanical properties of epoxy, such as tensile strength, elastic modulus, strain to failure, and fracture toughness. These improvements in nanocomposite properties have been attributed to the extraordinary properties of the nanotubes, as well as the quality of their dispersion within and adhesion to the epoxy matrix. However, many authors have also struggled to show significant mechanical improvements using similar methodologies and despite, in some cases, showing qualitative improvements in dispersion with optical microscopy. These authors have frequently resorted to other methods for improving the mechanical properties of CNT/epoxy, such as electrically aligning CNTs, using different types of CNTs, or modifying the stoichiometry. The current work examines many different dispersion techniques, types of CNTs, types of epoxies, curing cycles, and other variables in an attempt to improve the mechanical properties of neat epoxy with CNTs. Despite seeing significant changes in the microscopy, no significant improvements in tensile or fracture properties have been attributed to CNTs in this work.

  3. Mechanical characterization of capsule properties using abrupt-step channels

    NASA Astrophysics Data System (ADS)

    Salsac, Anne-Virginie; Le Goff, Anne; Kaoui, Badr; Barthè-Biesel, Dominique; Biomechanics; Bioengineering Lab Team

    2017-11-01

    Capsules consisting of a liquid droplet enclosed by a thin polymerized membrane are commonly encountered in nature (cells) or in industrial process (pharmaceutical, cosmetic or food products). The mechanical properties of the capsule wall are essential to guarantee the particle integrity and release of the internal contents when and where necessary. The difficulty is to assess the mechanical properties of the thin membrane. We will show how abrupt-step channels can be used to identify the membrane viscoelastic properties and point of rupture. This can be achieved by using a channel presenting a step change in cross-section and inverting the direction of the flow of the capsule suspension within the tube. To deduce information on the viscoelasticity, we will exploit the relaxation of the capsules as they flow through the expansion. To study membrane rupture, we will instead invert the channel, block the capsules at the neck of the constriction and determine the pressure difference needed for breakup. All the experiments will be conducted on initially spherical capsules with a thin cross-linked protein membrane for a proof of concept.

  4. [Investigation of the accurate measurement of the basic imaging properties for the digital radiographic system based on flat panel detector].

    PubMed

    Katayama, R; Sakai, S; Sakaguchi, T; Maeda, T; Takada, K; Hayabuchi, N; Morishita, J

    2008-07-20

    PURPOSE/AIM OF THE EXHIBIT: The purpose of this exhibit is: 1. To explain "resampling", an image data processing, performed by the digital radiographic system based on flat panel detector (FPD). 2. To show the influence of "resampling" on the basic imaging properties. 3. To present accurate measurement methods of the basic imaging properties of the FPD system. 1. The relationship between the matrix sizes of the output image and the image data acquired on FPD that automatically changes depending on a selected image size (FOV). 2. The explanation of the image data processing of "resampling". 3. The evaluation results of the basic imaging properties of the FPD system using two types of DICOM image to which "resampling" was performed: characteristic curves, presampled MTFs, noise power spectra, detective quantum efficiencies. CONCLUSION/SUMMARY: The major points of the exhibit are as follows: 1. The influence of "resampling" should not be disregarded in the evaluation of the basic imaging properties of the flat panel detector system. 2. It is necessary for the basic imaging properties to be measured by using DICOM image to which no "resampling" is performed.

  5. Assesment of influncing factors on mechanical and electrical properties of Al/Cu joints

    NASA Astrophysics Data System (ADS)

    Selvaraj, R. Meby; Hynes, N. Rajesh Jesudoss

    2018-05-01

    Joining of dissimilar materials opens up challenging opportunities in todays technology. Al/Cu weldments are used in applications that demands corrosion resistance, thermal and electrical conducting properties. In dissimilar joining mechanical and thermal properties result in large stress gradients during heating. The Al-Cu joints are lighter, cheaper and have conductivity equal to copper alloy. The main scope of this study is to assess the influencing factors of Al/Cu joints in mechanical and electrical properties. It includes the influence of the dilution between the base metals, influence of physical properties, influence of welding parameters, influence of filler metal, influence of heat treatment, and influence of electrical properties

  6. Compositional Determinants of Mechanical Properties of Enamel

    PubMed Central

    Baldassarri, M.; Margolis, H.C.; Beniash, E.

    2008-01-01

    Dental enamel is comprised primarily of carbonated apatite, with less than 1% w/w organic matter and 4-5% w/w water. To determine the influence of each component on the microhardness and fracture toughness of rat incisor enamel, we mechanically tested specimens in which water and organic matrix were selectively removed. Tests were performed in mid-sagittal and transverse orientations to assess the effect of the structural organization on enamel micromechanical properties. While removal of organic matrix resulted in up to a 23% increase in microhardness, and as much as a 46% decrease in fracture toughness, water had a significantly lesser effect on these properties. Moreover, removal of organic matrix dramatically weakened the dentino-enamel junction (DEJ). Analysis of our data also showed that the structural organization of enamel affects its micromechanical properties. We anticipate that these findings will help guide the development of bio-inspired nanostructured materials for mineralized tissue repair and regeneration. PMID:18573984

  7. Mechanical property characterization of intraply hybrid composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sinclair, J. H.

    1979-01-01

    An investigation was conducted to characterize the mechanical properties of intraply hybrids made from graphite fiber/epoxy matrix (primary composites) hybridized with varying amounts of secondary composites made from S-glass or Kevlar 49 fibers. The tests were conducted using thin laminates having the same thickness. The specimens for these tests were instrumented with strain gages to determine stress-strain behavior. Significant results are included.

  8. Electronic properties and mechanical strength of β-phosphorene nano-ribbons

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Swaroop, Ram; Bhatia, Pradeep; Kumar, Ashok, E-mail: ashok@cup.ac.in

    We have performed first principles calculations to find out the effect of mechanical strain on the electronic properties of zig-zag edged nano ribbons of β-phosphorene. It is found that electronic band-gap get opened-up to 2.61 eV by passivation of the edges of ribbons. Similarly, the mechanical strength is found to be increase from 1.75 GPa to 2.65 GPa on going from unpassivated nano ribbons to passivated ones along with the 2% increase in ultimate tensile strain. The band-gap value of passivated ribbon gets decreased to 0.43 eV on applying strain up to which the ribbon does not break. These tunable properties ofmore » β-phospherene with passivation with H-atom and applying mechanical strain offer its use in tunable nano electronics.« less

  9. Use of regional mechanical properties of abdominal aortic aneurysms to advance finite element modeling of rupture risk.

    PubMed

    Tierney, Áine P; Callanan, Anthony; McGloughlin, Timothy M

    2012-02-01

    To investigate the use of regional variations in the mechanical properties of abdominal aortic aneurysms (AAA) in finite element (FE) modeling of AAA rupture risk, which has heretofore assumed homogeneous mechanical tissue properties. Electrocardiogram-gated computed tomography scans from 3 male patients with known infrarenal AAA were used to characterize the behavior of the aneurysm in 4 different segments (posterior, anterior, and left and right lateral) at maximum diameter and above the infrarenal aorta. The elasticity of the aneurysm (circumferential cyclic strain, compliance, and the Hudetz incremental modulus) was calculated for each segment and the aneurysm as a whole. The FE analysis inclusive of prestress (pre-existing tensile stress) produced a detailed stress pattern on each of the aneurysm models under pressure loading. The 4 largest areas of stress in each region were considered in conjunction with the local regional properties of the segment to define a specific regional prestress rupture index (RPRI). In terms of elasticity, there were average reductions of 68% in circumferential cyclic strain and 63% in compliance, with a >5-fold increase in incremental modulus, between the healthy and the aneurysmal aorta for each patient. There were also regional variations in all elastic properties in each individual patient. The average difference in total stress inclusive of prestress was 59%, 67%, and 15%, respectively, for the 3 patients. Comparing the strain from FE models with the CT scans revealed an average difference in strain of 1.55% for the segmented models and 3.61% for the homogeneous models, which suggests that the segmented models more accurately reflect in vivo behavior. RPRI values were calculated for each segment for all patients. A greater understanding of the local material properties and their use in FE models is essential for greater accuracy in rupture prediction. Quantifying the regional behavior will yield insight into the changes in

  10. Study of Al-Si Alloy Oxygen Saturation on Its Microstructure and Mechanical Properties.

    PubMed

    Finkelstein, Arkady; Schaefer, Arseny; Chikova, Оlga; Borodianskiy, Konstantin

    2017-07-11

    One of the main goals of modern materials research is obtaining different microstructures and studying their influence on the mechanical properties of metals; aluminum alloys are particularly of interest due to their advanced performance. Traditionally, their required properties are obtained by alloying process, modification, or physical influence during solidification. The present work describes a saturation of the overheated AlSi₇Fe₁ casting alloy by oxides using oxygen blowing approach in overheated alloy. Changes in metals' microstructural and mechanical properties are also described in the work. An Al 10 SiFe intermetallic complex compound was obtained as a preferable component to Al₂O₃ precipitation on it, and its morphology was investigated by scanning electron microscopy. The mechanical properties of the alloy after the oxygen blowing treatment are discussed in this work.

  11. Thermal treatment and mechanical properties of aluminum-2021

    NASA Technical Reports Server (NTRS)

    Brennecke, M. W.

    1970-01-01

    Mechanical properties, after thermal treatments, are summarized for sheet and plate of copper-rich, high-strength, heat-treatable aluminum-2021. The alloy is quench sensitive, quench rate and variations in aging affect corrosion behavior. Aging effects on yield strength, tensile strength, and elongation of sheet and plate are compared.

  12. Evaluation of mechanical properties and durability performance of HDPE-wood composites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tazi, M.; Erchiqui, F.; Kaddami, H.

    The objective of this work is to evaluate the mechanical properties and durability performance of bio-composite materials made from sawdust and thermoplastic polymer (HDPE). For the preparation of the composites, sawdust in different proportions with Maleic Anhydride grafted Polyethylene (MAPE) as the coupling agent was used. The thermal and mechanical properties were successively characterized. The results indicate that adding wood fillers to a polymer matrix increases the degree of crystallinity and improves the tensile strength and ductility of composites. On the contrary, resistance to water absorption decreases as a function of the wood fillers. Scanning electron microscopy (SEM) was usedmore » to analyze morphological structure alteration when exposed to intense weathering. The biodegradability of bio-composites up to 97 days was also investigated; the results indicate that, by increasing the filler content, the amount of weight loss increased as well. In other words, even though the addition of sawdust to thermoplastic polymer improves the mechanical performance of a composite material, it also accelerates the biodegradation rate of the composite. An optimum amount of filler content might compromise the effect of biodegradation and mechanical properties of composite materials.« less

  13. Mechanical properties of MEMS materials: reliability investigations by mechanical- and HRXRD-characterization related to environmental testing

    NASA Astrophysics Data System (ADS)

    Bandi, T.; Shea, H.; Neels, A.

    2014-06-01

    The performance and aging of MEMS often rely on the stability of the mechanical properties over time and under harsh conditions. An overview is given on methods to investigate small variations of the mechanical properties of structural MEMS materials by functional characterization, high-resolution x-ray diffraction methods (HR-XRD) and environmental testing. The measurement of the dynamical properties of micro-resonators is a powerful method for the investigation of elasticity variations in structures relevant to microtechnology. X-ray diffraction techniques are used to analyze residual strains and deformations with high accuracy and in a non-destructive manner at surfaces and in buried micro-structures. The influence of elevated temperatures and radiation damage on the performance of resonant microstructures with a focus on quartz and single crystal silicon is discussed and illustrated with examples including work done in our laboratories at CSEM and EPFL.

  14. Influence of cross-link structure, density and mechanical properties in the mesoscale deformation mechanisms of collagen fibrils

    PubMed Central

    Depalle, Baptiste; Qin, Zhao; Shefelbine, Sandra J.; Buehler, Markus J.

    2015-01-01

    Collagen is a ubiquitous protein with remarkable mechanical properties. It is highly elastic, shows large fracture strength and enables substantial energy dissipation during deformation. Most of the connective tissue in humans consists of collagen fibrils composed of a staggered array of tropocollagen molecules, which are connected by intermolecular cross-links. In this study, we report a three-dimensional coarse-grained model of collagen and analyze the influence of enzymatic cross-links on the mechanics of collagen fibrils. Two representatives immature and mature cross-links are implemented in the mesoscale model using a bottom-up approach. By varying the number, type and mechanical properties of cross-links in the fibrils and performing tensile test on the models, we systematically investigate the deformation mechanisms of cross-linked collagen fibrils. We find that cross-linked fibrils exhibit a three phase behavior, which agrees closer with experimental results than what was obtained using previous models. The fibril mechanical response is characterized by: (i) an initial elastic deformation corresponding to the collagen molecule uncoiling, (ii) a linear regime dominated by molecule sliding and (iii) the second stiffer elastic regime related to the stretching of the backbone of the tropocollagen molecules until the fibril ruptures. Our results suggest that both cross-link density and type dictate the stiffness of large deformation regime by increasing the number of interconnected molecules while cross-links mechanical properties determine the failure strain and strength of the fibril. These findings reveal that cross-links play an essential role in creating an interconnected fibrillar material of tunable toughness and strength. PMID:25153614

  15. Modeling of Mechanical Properties of Advanced Nanostructured Ceramic Composites

    DTIC Science & Technology

    2010-03-15

    of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently...nucleation of nanograins near crack tips and its role as a special toughening mechanism in ceramic nanocomposites; (vii) generation of nanoscale tracks at...mechanical properties 16. SECURITY CLASSIFICATION OF : a . REPORT b. ABSTRACT c. THIS PAGE 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES

  16. Relationship between mechanical-property and energy-absorption trends for composite tubes

    NASA Technical Reports Server (NTRS)

    Farley, Gary L.

    1992-01-01

    U.S. Army helicopters are designed to dissipate prescribed levels of crash impact kinetic energy without compromising the integrity of the fuselage. Because of the complexity of the energy-absorption process it is imperative for designers of energy-absorbing structures to develop an in-depth understanding of how and why composite structures absorb energy. A description of the crushing modes and mechanisms of energy absorption for composite tubes and beams is presented. Three primary crushing modes of composite structures including transverse shearing, lamina bending, and local buckling are described. The experimental data presented show that fiber and matrix mechanical properties and laminate stiffness and strength mechanical properties cannot reliably predict the energy-absorption response of composite tubes.

  17. Improvement of Mechanical Properties in Natural Rubber with Organic Fillers

    NASA Astrophysics Data System (ADS)

    Gonzales-Fernandes, M.; Bastos, Andrade C. G.; Esper, F. J.; Valenzuela-Diaz, F. R.; Wiebeck, H.

    When added to polymeric matrices, organophilic clay transforms the performance of the resulting composites. A natural rubber matrix with different loads was prepared as bentonite chocolate B modified by sodification and treated with ammonium quaternary salt with cellulose charge, cardboard and palm fiber. After the mixture of natural rubber in a roller mill with the additives and subsequent addition of loads individually, plates were vulcanized for fabricating specimens. We measured the mechanical properties of traction and the interlayer distances analyzed by XRD. The aim of the paper is to show that the composite obtained improved in mechanical properties as compared to plates without the addition of loads.

  18. Electrospun PCL/Gelatin composite fibrous scaffolds: mechanical properties and cellular responses.

    PubMed

    Yao, Ruijuan; He, Jing; Meng, Guolong; Jiang, Bo; Wu, Fang

    2016-06-01

    Electrospinning of hybrid polymer has gained widespread interest by taking advantages of the biological property of the natural polymer and the mechanical property of the synthetic polymer. However, the effect of the blend ratio on the above two properties has been less reported despite the importance to balance these two properties in various tissue engineering applications. To this aim, we investigated the electrospun PCL/Gelatin composite fibrous scaffolds with different blend ratios of 4:1, 2:1, 1:1, 1:2, 1:4, respectively. The morphology of the electrospun samples was observed by SEM and the result showed that the fiber diameter distribution became more uniform with the increase of the gelatin content. The mechanical testing results indicated that the 2:1 PCL/Gelatin sample had both the highest tensile strength of 3.7 MPa and the highest elongation rate of about 90%. Surprisingly, the 2:1 PCL/Gelatin sample also showed the best mesenchymal stem cell responses in terms of attachment, spreading, and cytoskeleton organization. Such correlation might be partly due to the fact that the enhanced mechanical property, an integral part of the physical microenvironment, likely played an important role in regulating the cellular functions. Overall, our results indicated that the PCL/Gelatin sample with the blend ratio of 2:1 was a superior candidate for scaffolds for tissue engineering applications.

  19. An investigation into the mechanism for enhanced mechanical properties in friction stir welded AA2024-T3 joints coated with cold spraying

    NASA Astrophysics Data System (ADS)

    Li, N.; Li, W. Y.; Yang, X. W.; Feng, Y.; Vairis, A.

    2018-05-01

    Using cold spraying (CS), a surface layer with a modified microstructure and enhanced mechanical properties was formed on a 3.2 mm thick friction stir welded (FSWed) AA2024-T3 joint. The combined effect of "shot peening effect (SPE)" and "heat flow effect (HFE)" during CS were used to enhance joint mechanical properties. The microstructure evolution of the FSWed AA2024-T3 joints in the surface layer following CS coatings and their effect on mechanical properties were systematically characterized with electron back-scattered diffraction, transmission electron microscopy, differential scanning calorimetry and mechanical tests. Based on these experiments, a grain refinement, finer and more S phases, and improved amount of Guinier-Preston-Bagaryatsky (GPB) zones produced by CS treatments are proposed. The deposition of aluminum coating on the joint, lead to hardness recovery in the stir zone and the development of two low hardness zones as the density of GPB increased. The tensile properties of FSWed AA2024-T3 joints improved with the application of the aluminum coatings. Experiments and analysis of the enhanced mechanical properties mechanism indicate that SPE with a high plastic deformation and HFE with an intensive heat flow are necessary for the production of refined grains and increased numbers of GPB zones.

  20. Sensitized gelatin as a versatile biomaterial with tailored mechanical and optical properties

    NASA Astrophysics Data System (ADS)

    Muric, B.; Pantelic, D.; Vasiljevic, D.; Zarkov, B.; Jelenkovic, B.; Pantovic, S.; Rosic, M.

    2013-11-01

    We have found that gelatin doped with tot'hema (medication used for curing anemia) and eosin becomes elastic, while retaining good optical properties. The mechanical properties of tot'hema-eosin-sensitized gelatin films (TESG) have been investigated for various concentrations of tot'hema (ranging from 5 to 30% v/v). TESG specimens were prepared according to the ASTM standards for elastic materials. Tensile strength, strain at break and Young's modulus were measured. The results show that the extensibility of TESG film increases with increasing tot'hema concentration, while the Young's modulus and stress at break exponentially decrease. Mechanical properties can be tailored to suit various biomedical applications such as blood vessels, human lens capsules and biosensors based on microlenses. Tunable (strain responsive) TESG microlenses were produced and a mechanical model of blood vessels was prepared.

  1. Advanced glycation products' levels and mechanical properties of vaginal tissue in pregnancy.

    PubMed

    Weli, Homayemem K; Akhtar, Riaz; Chang, Zhuo; Li, Wen-Wu; Cooper, Jason; Yang, Ying

    2017-07-01

    Non-enzymatic glycation is closely associated with altered mechanical properties of connective tissue. Pregnancy, marked with high levels of female hormones, confers unique alteration to the mechanical properties of pelvic connective tissues in order to meet their physiological demands. However, there are few studies on glycation content and its influence on the mechanical properties of pelvic connective tissues during pregnancy. We hypothesise that the glycation content in pelvic tissues will change with a corresponding alteration in their mechanical properties, and that these changes are influenced by hormone levels. This study aims to investigate the correlation of vaginal tissue glycation content and mechanical property changes during pregnancy in association with the expression of a key pregnancy hormone (oestrogen) receptor, and an antioxidant enzyme, glyoxalase I. A rat vaginal tissue model (tissues from non-pregnant and E15-E18 (last trimester) pregnant rats) was used in this study. Mechanical characteristics of vaginal tissues were analysed by a ball-indentation technique while modulus and morphology of the collagen fibrils within the tissues were measured with atomic force microscopy. A glycation marker, pentosidine, was quantified by a high performance liquid chromatography. The expression of oestrogen receptor and glyoxalase I in the tissue was qualified by immunochemical staining. The glycosaminoglycan (GAG) concentration difference in the tissues were quantified by a biochemical assay. Pregnant rat vaginal tissue was characterised by significantly lower amounts of pentosidine, higher oestrogen receptor and glyoxalase I expression with larger creep, lower elastic modulus, larger fibril diameter and higher GAG content than their non-pregnant counterpart. There was a negative correlation between pentosidine and vaginal tissue creep. There was a reduction in vaginal tissue pentosidine in pregnancy with an associated increase in oestrogen receptor and

  2. Influence of carbon nanotubes on mechanical properties and structure of rigid polyurethane foam

    NASA Astrophysics Data System (ADS)

    Ciecierska, E.; Jurczyk-Kowalska, M.; Bazarnik, P.; Kulesza, M.; Lewandowska, M.; Kowalski, M.; Krauze, S.

    2014-08-01

    In this work, the influence of carbon nanotubes addition on foam structure and mechanical properties of rigid polyurethane foam/nanotube composites was investigated. Scanning electron microscopy was performed to reveal the foam porous structure and distribution of carbon nanotubes. To determine the mechanical properties, three point bending tests were carried out.

  3. Microstructure, mechanical properties, bio-corrosion properties and cytotoxicity of as-extruded Mg-Sr alloys.

    PubMed

    Zhao, Chaoyong; Pan, Fusheng; Zhang, Lei; Pan, Hucheng; Song, Kai; Tang, Aitao

    2017-01-01

    In this study, as-extruded Mg-Sr alloys were studied for orthopedic application, and the microstructure, mechanical properties, bio-corrosion properties and cytotoxicity of as-extruded Mg-Sr alloys were investigated by optical microscopy, scanning electron microscopy with an energy dispersive X-ray spectroscopy, X-ray diffraction, tensile and compressive tests, immersion test, electrochemical test and cytotoxicity test. The results showed that as-extruded Mg-Sr alloys were composed of α-Mg and Mg 17 Sr 2 phases, and the content of Mg 17 Sr 2 phases increased with increasing Sr content. As-extruded Mg-Sr alloy with 0.5wt.% Sr was equiaxed grains, while the one with a higher Sr content was long elongated grains and the grain size of the long elongated grains decreased with increasing Sr content. Tensile and compressive tests showed an increase of both tensile and compressive strength and a decrease of elongation with increasing Sr content. Immersion and electrochemical tests showed that as-extruded Mg-0.5Sr alloy exhibited the best anti-corrosion property, and the anti-corrosion property of as-extruded Mg-Sr alloys deteriorated with increasing Sr content, which was greatly associated with galvanic couple effect. The cytotoxicity test revealed that as-extruded Mg-0.5Sr alloy did not induce toxicity to cells. These results indicated that as-extruded Mg-0.5Sr alloy with suitable mechanical properties, corrosion resistance and good cytocompatibility was potential as a biodegradable implant for orthopedic application. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Study on Thermal and Mechanical Properties of EPDM Insulation

    NASA Astrophysics Data System (ADS)

    Zhang, Zhong-Shui; Xu, Jin-Sheng; Chen, Xiong; Jiang, Jing

    As the most common insulation material of solid rocket motors, thermal and mechanical properties of ethylene propylene diene monomer (EPDM) composite are inspected in the study. Referring to the results of thermogravimetric analysis (TGA), composition and morphology of EPDM composite in different thermal degradation degree are investigated by scanning electron microscope (SEM) to inspect the mechanism of thermal insulation. Mechanical properties of EPDM composite in the state of pyrolysis are investigated by uniaxial tensile tests. At the state of initial pyrolysis, composite belongs to the category of hyperelastic-viscoelastic material. The tendency of tensile strength increased and elongation decreased with increasing of heating temperature. Composite behaves as the linear rule at the state of late pyrolysis, which belongs to the category of bittle. The elasticity modulus of curves are almost the same while the heating temperature ranges from 200°C to 300°C, and then gradually go down. The tensile strength of pyrolytic material reach the highest at the heating temperature of 300°C, and the virgin material has the largest elongation.

  5. Effects of Surface Modification on the Mechanical Properties of Flax/β-Polypropylene Composites

    PubMed Central

    Wu, Chang-Mou; Lai, Wen-You; Wang, Chen-Yu

    2016-01-01

    The effects of surface treatment of flax fibers featuring vinyltrimethoxy silane (VTMO) and maleic anhydride-polypropylene (MAPP) on the mechanical properties of flax/PP composites were investigated. α-polypropylene (α-PP) and β-polypropylene (β-PP) were used as matrices for measuring the mechanical properties of the flax fiber/polypropylene (flax/PP) composites. Flax/PP composites composed of double-covered uncommingled yarn (DCUY) were prepared using a film-stacking technique. The influence of surface treatment on the tensile, flexural, impact, and water uptake properties of Flax/PP composites were investigated. MAPP treatment was suitable for flax/PP composites in terms of superior tensile and impact properties. VTMO treatment showed superior flexural properties and less influence on the impact properties after moisture absorption. PMID:28773439

  6. Structures and Mechanical Properties of Natural and Synthetic Diamonds

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1998-01-01

    A revolution in the diamond technology is in progress, as the low-pressure process becomes an industrial reality. It will soon be possible to take advantage of the demanding properties of diamond to develop a myriad of new applications, particularly for self-lubricating, wear-resistant, and superhard coatings. The production of large diamond films or sheets at low cost, a distinct possibility in the not-too-distant future, may drastically change tribology technology, particularly regarding solid lubricants and lubricating materials and systems. This paper reviews the structures and properties of natural and synthetic diamonds to gain a better understanding of the tribological properties of diamond and related materials. Atomic and crystal structure, impurities, mechanical properties, and indentation hardness of diamond are described.

  7. Numerical investigation of the mechanical properties of the additive manufactured bone scaffolds fabricated by FDM: The effect of layer penetration and post-heating.

    PubMed

    Naghieh, S; Karamooz Ravari, M R; Badrossamay, M; Foroozmehr, E; Kadkhodaei, M

    2016-06-01

    In recent years, thanks to additive manufacturing technology, researchers have gone towards the optimization of bone scaffolds for the bone reconstruction. Bone scaffolds should have appropriate biological as well as mechanical properties in order to play a decisive role in bone healing. Since the fabrication of scaffolds is time consuming and expensive, numerical methods are often utilized to simulate their mechanical properties in order to find a nearly optimum one. Finite element analysis is one of the most common numerical methods that is used in this regard. In this paper, a parametric finite element model is developed to assess the effects of layers penetration׳s effect on inter-layer adhesion, which is reflected on the mechanical properties of bone scaffolds. To be able to validate this model, some compression test specimens as well as bone scaffolds are fabricated with biocompatible and biodegradable poly lactic acid using fused deposition modeling. All these specimens are tested in compression and their elastic modulus is obtained. Using the material parameters of the compression test specimens, the finite element analysis of the bone scaffold is performed. The obtained elastic modulus is compared with experiment indicating a good agreement. Accordingly, the proposed finite element model is able to predict the mechanical behavior of fabricated bone scaffolds accurately. In addition, the effect of post-heating of bone scaffolds on their elastic modulus is investigated. The results demonstrate that the numerically predicted elastic modulus of scaffold is closer to experimental outcomes in comparison with as-built samples. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Revisit to three-dimensional percolation theory: Accurate analysis for highly stretchable conductive composite materials

    PubMed Central

    Kim, Sangwoo; Choi, Seongdae; Oh, Eunho; Byun, Junghwan; Kim, Hyunjong; Lee, Byeongmoon; Lee, Seunghwan; Hong, Yongtaek

    2016-01-01

    A percolation theory based on variation of conductive filler fraction has been widely used to explain the behavior of conductive composite materials under both small and large deformation conditions. However, it typically fails in properly analyzing the materials under the large deformation since the assumption may not be valid in such a case. Therefore, we proposed a new three-dimensional percolation theory by considering three key factors: nonlinear elasticity, precisely measured strain-dependent Poisson’s ratio, and strain-dependent percolation threshold. Digital image correlation (DIC) method was used to determine actual Poisson’s ratios at various strain levels, which were used to accurately estimate variation of conductive filler volume fraction under deformation. We also adopted strain-dependent percolation threshold caused by the filler re-location with deformation. When three key factors were considered, electrical performance change was accurately analyzed for composite materials with both isotropic and anisotropic mechanical properties. PMID:27694856

  9. Physical, mechanical, and fire properties of oriented strandboard with fire retardant treated veneers

    Treesearch

    Nadir Ayrilmis; Zeki Candan; Robert White

    2007-01-01

    This study evaluated physical, mechanical and fire properties of oriented strand boards (OSB) covered with fire retardant treated veneers. The beech (Fagus orientalis Lipsky) veneers were treated with either monoammonium phosphate, diammonium phosphate, lime water or a borax/boric acid (1 : 1 by weight) mixture. Physical and mechanical properties of the specimens were...

  10. Effect of kenaf short fiber loading on mechanical properties of biocomposites

    NASA Astrophysics Data System (ADS)

    Andilolo, J.; Nikmatin, S.; Nugroho, N.; Alatas, H.; Wismogroho, A. S.

    2017-05-01

    The research of biocomposite product with kenaf (Hibiscus cannabinus) short fiber as a filler and Acrylonitrile Butadiene Styrene (ABS) as the matrix had been done to understand the mechanical properties of this material. Kenaf short fiber was obtained from mechanical sieving after doing the mechanical milling. TAPPI method has been done to determine the chemical properties. In order to form a granular biocomposite a single screw extruder was performed with a variation of particle loading 10 and 15%. The original of acrylonitrile butadiene styrene (ABS) has been used as matrix. The fabrication of speciment had been done by molding injection process. Mechanical properties test was done by ASTM standarization. The results showed the density of the fibers of 1.008 g/cm3 with a fiber length of 897.07 µm and a diameter of 66.38 µm. Tensile strength of kenaf short fiber loading 10 and 15% was 23.522 ± 8.36 MPa and 20.739 ± 6.79 MPa, respectively. The tensile properties showed a decreasing trend as the fiber loading was increased. The values of impact strength were 68.657 ± 4.89 kJ m-2 and 82.090 ± 5.56 kJ m-2, respectively and the hardness values were 96.60 ± 6.03 HR and 105.20 ± 13.17 HR, respectively. Kenaf fiber can be a good reinforcement candidate for high performance polymer bio-composites.

  11. Mechanical Properties of Mineralized Collagen Fibrils As Influenced By Demineralization

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Balooch, M.; Habelitz, S.; Kinney, J.H.

    2009-05-11

    Dentin and bone derive their mechanical properties from a complex arrangement of collagen type-I fibrils reinforced with nanocrystalline apatite mineral in extra- and intrafibrillar compartments. While mechanical properties have been determined for the bulk of the mineralized tissue, information on the mechanics of the individual fibril is limited. Here, atomic force microscopy was used on individual collagen fibrils to study structural and mechanical changes during acid etching. The characteristic 67 nm periodicity of gap zones was not observed on the mineralized fibril, but became apparent and increasingly pronounced with continuous demineralization. AFM-nanoindentation showed a decrease in modulus from 1.5 GPamore » to 50 MPa during acid etching of individual collagen fibrils and revealed that the modulus profile followed the axial periodicity. The nanomechanical data, Raman spectroscopy and SAXS support the hypothesis that intrafibrillar mineral etches at a substantially slower rate than the extrafibrillar mineral. These findings are relevant for understanding the biomechanics and design principles of calcified tissues derived from collagen matrices.« less

  12. Stimuli-responsive Materials and Structures with Electrically Tunable Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Auletta, Jeffrey Thomas

    Electricity, a convenient stimulus, was used to manipulate the mechanical properties of two classes of materials, each with a different mechanism. In the first system, macroscale electroplastic elastomer hydrogels (EPEs) were reversibly cycled through soft and hard states by sequential application of oxidative and reductive potentials. Electrochemically reversible crosslinks were switched between strongly binding Fe3+ and weak to non-binding Fe2+, as determined by potentiometric titration.With the incorporation of graphene oxide (GO) into the EPE, a significant enhancement in modulus and toughness was observed, allowing for the preparation of thinner EPE samples, which could be reversibly cycled between soft and hard states over 30 minutes. Further characterization of this EPE by magnetic susceptibility measurements suggested the formation of multinuclear iron clusters within the gel. Copper-derived EPEs which exploited the same redox-controlled mechanism for switching between hard and soft states were also prepared. Here, the density of temporary crosslinks and the mechanical properties were controlled by reversibly switching between the +1 and +2 oxidation states, using a combination of electrochemical/air oxidation and chemical reduction. In addition to undergoing redox-controlled changes in modulus, these EPEs exhibited shape memory. In the second system, electroadhesion between ionomer layers was exploited to create laminate structures whose rigidity depended on the reversible polarization of the dielectric polymers. The role of the counter-ion in determining the intrinsic and electroadhesive properties of poly(ethylene-co-acrylic acid) ionomers in bi- and tri-layered laminate structures was examined. PEAA ionomers were prepared with three tetraalkylammonium cations (NR4 +, R = methyl, TMA+; ethyl, TEA+; and propyl, TPA+). Reflecting the increasing hydrophobicity of the longer alkyl chains, water uptake changed as a function of counterion with TMA+ > TEA

  13. Thermal and mechanical properties of TPU/PBT reinforced by carbon fiber

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Huang, Jintao; Liu, Huanyu; Lu, Xiang

    2016-03-09

    In this study, thermal, mechanical properties and processability were performed on a series of carbon fiber (CF) filled thermoplastic polyurethane (TPU)/poly (butylene terephthalate) (PBT) composites to identify the effect of CF weight fraction on the properties of TPU/PBT. Scanning Electronic Microscope (SEM) show that CFs are uniformly dispersed in TPU/PBT matrix and there are no agglomerations. Melt flow index (MFI) show that the melt viscosity increased with the CF loading. Thermogravimetric analysis (TGA) revealed that the introduction of CF into organic materials tend to improve their thermal stability. The mechanical properties indicated that tensile strength and modulus, flexural strength andmore » modulus, improved with an increase in CF loading, but the impact strength decreased by the loading of CF.« less

  14. Impact of Desalination on Physical and Mechanical Properties of Lanzhou Loess

    NASA Astrophysics Data System (ADS)

    Bing, Hui; Zhang, Ying; Ma, Min

    2017-12-01

    Soluble salt in soil has a significant influence on the physical and mechanical properties of the soil. We performed desalination experiments on Lanzhou loess, a typical sulfate saline soil, to study the effects of salt on the physical and mechanical properties of the loess and compare variations in the soil properties after desalination. The Atterberg limits of the soil increased after desalination as a result of changes in the soil particle composition and grain refinement. The shear and uniaxial compressive strength of the soil increased as a result of decreased calcitic cementation and other changes to the soil structure. Scanning electron microstructure (SEM) and mercury intrusion porosimetry (MIP) procedures revealed changes to the microstructure and pore-size distribution of the Lanzhou loess after desalination.

  15. Enhancement of the Mechanical Properties of Basalt Fiber-Wood-Plastic Composites via Maleic Anhydride Grafted High-Density Polyethylene (MAPE) Addition

    PubMed Central

    Chen, Jinxiang; Wang, Yong; Gu, Chenglong; Liu, Jianxun; Liu, Yufu; Li, Min; Lu, Yun

    2013-01-01

    This study investigated the mechanisms, using microscopy and strength testing approaches, by which the addition of maleic anhydride grafted high-density polyethylene (MAPE) enhances the mechanical properties of basalt fiber-wood-plastic composites (BF-WPCs). The maximum values of the specific tensile and flexural strengths areachieved at a MAPE content of 5%–8%. The elongation increases rapidly at first and then continues slowly. The nearly complete integration of the wood fiber with the high-density polyethylene upon MAPE addition to WPC is examined, and two models of interfacial behavior are proposed. We examined the physical significance of both interfacial models and their ability to accurately describe the effects of MAPE addition. The mechanism of formation of the Model I interface and the integrated matrix is outlined based on the chemical reactions that may occur between the various components as a result of hydrogen bond formation or based on the principle of compatibility, resulting from similar polarity. The Model I fracture occurred on the outer surface of the interfacial layer, visually demonstrating the compatibilization effect of MAPE addition. PMID:28809285

  16. Enhancement of the Mechanical Properties of Basalt Fiber-Wood-Plastic Composites via Maleic Anhydride Grafted High-Density Polyethylene (MAPE) Addition.

    PubMed

    Chen, Jinxiang; Wang, Yong; Gu, Chenglong; Liu, Jianxun; Liu, Yufu; Li, Min; Lu, Yun

    2013-06-18

    This study investigated the mechanisms, using microscopy and strength testing approaches, by which the addition of maleic anhydride grafted high-density polyethylene (MAPE) enhances the mechanical properties of basalt fiber-wood-plastic composites (BF-WPCs). The maximum values of the specific tensile and flexural strengths are achieved at a MAPE content of 5%-8%. The elongation increases rapidly at first and then continues slowly. The nearly complete integration of the wood fiber with the high-density polyethylene upon MAPE addition to WPC is examined, and two models of interfacial behavior are proposed. We examined the physical significance of both interfacial models and their ability to accurately describe the effects of MAPE addition. The mechanism of formation of the Model I interface and the integrated matrix is outlined based on the chemical reactions that may occur between the various components as a result of hydrogen bond formation or based on the principle of compatibility, resulting from similar polarity. The Model I fracture occurred on the outer surface of the interfacial layer, visually demonstrating the compatibilization effect of MAPE addition.

  17. Mechanical and thermal properties of irradiated films based on Tilapia ( Oreochromis niloticus) proteins

    NASA Astrophysics Data System (ADS)

    Sabato, S. F.; Nakamurakare, N.; Sobral, P. J. A.

    2007-11-01

    Proteins are considered potential material in natural films as alternative to traditional packaging. When gamma radiation is applied to protein film forming solution it resulted in an improvement in mechanical properties of whey protein films. The objective of this work was the characterization of mechanical and thermal properties of irradiated films based on muscle proteins from Nile Tilapia ( Oreochromis niloticus). The films were prepared according to a casting technique with two levels of plasticizer: 25% and 45% glycerol and irradiated in electron accelerator type Radiation Dynamics, 0.550 MeV at dose range from 0 to 200 kGy. Thermal properties and mechanical properties were determined using a differential scanning calorimeter and a texture analyzer, respectively. Radiation from electron beam caused a slightly increase on its tensile strength characteristic at 100 kGy, while elongation value at this dose had no reduction.

  18. Relationships among the structural topology, bond strength, and mechanical properties of single-walled aluminosilicate nanotubes.

    PubMed

    Liou, Kai-Hsin; Tsou, Nien-Ti; Kang, Dun-Yen

    2015-10-21

    Carbon nanotubes (CNTs) are regarded as small but strong due to their nanoscale microstructure and high mechanical strength (Young's modulus exceeds 1000 GPa). A longstanding question has been whether there exist other nanotube materials with mechanical properties as good as those of CNTs. In this study, we investigated the mechanical properties of single-walled aluminosilicate nanotubes (AlSiNTs) using a multiscale computational method and then conducted a comparison with single-walled carbon nanotubes (SWCNTs). By comparing the potential energy estimated from molecular and macroscopic material mechanics, we were able to model the chemical bonds as beam elements for the nanoscale continuum modeling. This method allowed for simulated mechanical tests (tensile, bending, and torsion) with minimum computational resources for deducing their Young's modulus and shear modulus. The proposed approach also enabled the creation of hypothetical nanotubes to elucidate the relative contributions of bond strength and nanotube structural topology to overall nanotube mechanical strength. Our results indicated that it is the structural topology rather than bond strength that dominates the mechanical properties of the nanotubes. Finally, we investigated the relationship between the structural topology and the mechanical properties by analyzing the von Mises stress distribution in the nanotubes. The proposed methodology proved effective in rationalizing differences in the mechanical properties of AlSiNTs and SWCNTs. Furthermore, this approach could be applied to the exploration of new high-strength nanotube materials.

  19. Mechanical Properties of Mg2Si/Mg Composites via Powder Metallurgy Process

    NASA Astrophysics Data System (ADS)

    Muramatsu, Hiroshi; Kondoh, Katsuyoshi; Yuasa, Eiji; Aizawa, Tatsuhiko

    The mechanical properties of the Mg2Si/Mg composites solid-state synthesized from the mixed Mg-Si powders have been investigated. The macro-hardness (HRE) and the tensile strength of the composites increase with increasing the Si content and decreasing the Si size. The particle size of the synthesized Mg2Si depends on the initial Si size; the mechanical properties of the Mg2Si/Mg composite are remarkably improved by using fine Si particles or by decreasing the grain size of Mg matrix grains when the powder mixture was prepared via bulk mechanical alloying process.

  20. Mechanical, thermal, and moisture properties of plastics with bean as filler

    USDA-ARS?s Scientific Manuscript database

    Experiments on polymers using beans as fillers are reported herein. We are looking for desirable mechanical, thermal and moisture properties at economical costs. Poly(lactic acid) (PLA) is studied as the polymeric matrix because it is available and biodegradable. Although the physical properties are...

  1. Bioinspired Bouligand cellulose nanocrystal composites: a review of mechanical properties

    NASA Astrophysics Data System (ADS)

    Natarajan, Bharath; Gilman, Jeffrey W.

    2017-12-01

    The twisted plywood, or Bouligand, structure is the most commonly observed microstructural motif in natural materials that possess high mechanical strength and toughness, such as that found in bone and the mantis shrimp dactyl club. These materials are isotropically toughened by a low volume fraction of soft, energy-dissipating polymer and by the Bouligand structure itself, through shear wave filtering and crack twisting, deflection and arrest. Cellulose nanocrystals (CNCs) are excellent candidates for the bottom-up fabrication of these structures, as they naturally self-assemble into `chiral nematic' films when cast from solutions and possess outstanding mechanical properties. In this article, we present a review of the fabrication techniques and the corresponding mechanical properties of Bouligand biomimetic CNC nanocomposites, while drawing comparison to the performance standards set by tough natural composite materials. This article is part of a discussion meeting issue `New horizons for cellulose nanotechnology'.

  2. Simulation Studies of Mechanical Properties of Novel Silica Nano-structures

    NASA Astrophysics Data System (ADS)

    Muralidharan, Krishna; Torras Costa, Joan; Trickey, Samuel B.

    2006-03-01

    Advances in nanotechnology and the importance of silica as a technological material continue to stimulate computational study of the properties of possible novel silica nanostructures. Thus we have done classical molecular dynamics (MD) and multi-scale quantum mechanical (QM/MD) simulation studies of the mechanical properties of single-wall and multi-wall silica nano-rods of varying dimensions. Such nano-rods have been predicted by Mallik et al. to be unusually strong in tensile failure. Here we compare failure mechanisms of such nano-rods under tension, compression, and bending. The concurrent multi-scale QM/MD studies use the general PUPIL system (Torras et al.). In this case, PUPIL provides automated interoperation of the MNDO Transfer Hamiltonian QM code (Taylor et al.) and a locally written MD code. Embedding of the QM-forces domain is via the scheme of Mallik et al. Work supported by NSF ITR award DMR-0325553.

  3. Environmental effects on the mechanical and thermomechanical properties of aspen fiber–polypropylene composites

    Treesearch

    Y. Xue; D.R. Veazie; C. Glinsey; M.F. Horstemeyer; R.M. Rowell

    2007-01-01

    The mechanical properties of newly developed aspen fiber–polypropylene composites (APC) were experimentally explored and numerically predicted at the temperatures and humidity that are typical for domestic housing applications. The mechanical properties of APCs with five different fiber-loadings were evaluated at the room temperature, 4 [degrees] C, and 40 [degrees] C...

  4. Mechanical properties and fracture behaviour of defective phosphorene nanotubes under uniaxial tension

    NASA Astrophysics Data System (ADS)

    Liu, Ping; Pei, Qing-Xiang; Huang, Wei; Zhang, Yong-Wei

    2017-12-01

    The easy formation of vacancy defects and the asymmetry in the two sublayers of phosphorene nanotubes (PNTs) may result in brand new mechanical properties and failure behaviour. Herein, we investigate the mechanical properties and fracture behaviour of defective PNTs under uniaxial tension using molecular dynamics simulations. Our simulation results show that atomic vacancies cause local stress concentration and thus significantly reduce the fracture strength and fracture strain of PNTs. More specifically, a 1% defect concentration is able to reduce the fracture strength and fracture strain by as much as 50% and 66%, respectively. Interestingly, the reduction in the mechanical properties is found to depend on the defect location: a defect located in the outer sublayer has a stronger effect than one located in the inner layer, especially for PNTs with a small diameter. Temperature is also found to strongly influence the mechanical properties of both defect-free and defective PNTs. When the temperature is increased from 0 K to 400 K, the fracture strength and fracture strain of defective PNTs with a defect concentration of 1% are reduced further by 71% and 61%, respectively. These findings are of great importance for the structural design of PNTs as building blocks in nanodevices.

  5. Mechanical properties of a bioabsorbable nerve guide tube for long nerve defects.

    PubMed

    Ichihara, S; Facca, S; Liverneaux, P; Inada, Y; Takigawa, T; Kaneko, K; Nakamura, T

    2015-09-01

    The mechanical properties of nerve guide tubes must be taken into consideration when they are being developed. We previously reported the feasibility of using 50:50 tubes in a canine 40mm peroneal nerve defect model, where 50:50 represents the proportion of poly(L-lactic) acid (PLLA) and polyglycolic acid (PGA). The aim of the current study was to show that 50:50 tubes have suitable mechanical properties for repairing long nerve defects. Four types of nerve guide tubes made with PLLA to PGA fiber ratios of 100:0 (i.e. 100% PLLA) (100:0 tube), 50:50 (50:50 tube), 10:90 (10:90 tube), and 0:100 (0:100 tube) were designed and created using a tubular braiding machine. Their mechanical properties were examined in vitro (up to 16 weeks). In compression testing, 50:50 tubes had the highest normalized force value, followed in order by the 100:0, 10:90, and 0:100 tubes up to 8 weeks after immersion. From the point of view of biomechanics and bioresorbability, out of the 4 tube types tested, 50:50 tubes appeared to have the optimal mechanical properties for longer nerve defects. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  6. Mechanical and hydraulic properties of Nankai accretionary prism sediments: Effect of stress path

    NASA Astrophysics Data System (ADS)

    Kitajima, Hiroko; Chester, Frederick M.; Biscontin, Giovanna

    2012-10-01

    We have conducted triaxial deformation experiments along different loading paths on prism sediments from the Nankai Trough. Different load paths of isotropic loading, uniaxial strain loading, triaxial compression (at constant confining pressure, Pc), undrained Pc reduction, drained Pc reduction, and triaxial unloading at constant Pc, were used to understand the evolution of mechanical and hydraulic properties under complicated stress states and loading histories in accretionary subduction zones. Five deformation experiments were conducted on three sediment core samples for the Nankai prism, specifically from older accreted sediments at the forearc basin, underthrust slope sediments beneath the megasplay fault, and overthrust Upper Shikoku Basin sediments along the frontal thrust. Yield envelopes for each sample were constructed based on the stress paths of Pc-reduction using the modified Cam-clay model, and in situ stress states of the prism were constrained using the results from the other load paths and accounting for horizontal stress. Results suggest that the sediments in the vicinity of the megasplay fault and frontal thrust are highly overconsolidated, and thus likely to deform brittle rather than ductile. The porosity of sediments decreases as the yield envelope expands, while the reduction in permeability mainly depends on the effective mean stress before yield, and the differential stress after yield. An improved understanding of sediment yield strength and hydromechanical properties along different load paths is necessary to treat accurately the coupling of deformation and fluid flow in accretionary subduction zones.

  7. Zirconia based dental ceramics: structure, mechanical properties, biocompatibility and applications.

    PubMed

    Gautam, Chandkiram; Joyner, Jarin; Gautam, Amarendra; Rao, Jitendra; Vajtai, Robert

    2016-12-06

    Zirconia (ZrO 2 ) based dental ceramics have been considered to be advantageous materials with adequate mechanical properties for the manufacturing of medical devices. Due to its very high compression strength of 2000 MPa, ZrO 2 can resist differing mechanical environments. During the crack propagation on the application of stress on the surface of ZrO 2 , a crystalline modification diminishes the propagation of cracks. In addition, zirconia's biocompatibility has been studied in vivo, leading to the observation of no adverse response upon the insertion of ZrO 2 samples into the bone or muscle. In vitro experimentation has exhibited the absence of mutations and good viability of cells cultured on this material leading to the use of ZrO 2 in the manufacturing of hip head prostheses. The mechanical properties of zirconia fixed partial dentures (FPDs) have proven to be superior to other ceramic/composite restorations and hence leading to their significant applications in implant supported rehabilitations. Recent developments were focused on the synthesis of zirconia based dental materials. More recently, zirconia has been introduced in prosthetic dentistry for the fabrication of crowns and fixed partial dentures in combination with computer aided design/computer aided manufacturing (CAD/CAM) techniques. This systematic review covers the results of past as well as recent scientific studies on the properties of zirconia based ceramics such as their specific compositions, microstructures, mechanical strength, biocompatibility and other applications in dentistry.

  8. Alzheimer's Aβ(1-40) Amyloid Fibrils Feature Size-Dependent Mechanical Properties

    PubMed Central

    Xu, Zhiping; Paparcone, Raffaella; Buehler, Markus J.

    2010-01-01

    Abstract Amyloid fibrils are highly ordered protein aggregates that are associated with several pathological processes, including prion propagation and Alzheimer's disease. A key issue in amyloid science is the need to understand the mechanical properties of amyloid fibrils and fibers to quantify biomechanical interactions with surrounding tissues, and to identify mechanobiological mechanisms associated with changes of material properties as amyloid fibrils grow from nanoscale to microscale structures. Here we report a series of computational studies in which atomistic simulation, elastic network modeling, and finite element simulation are utilized to elucidate the mechanical properties of Alzheimer's Aβ(1-40) amyloid fibrils as a function of the length of the protein filament for both twofold and threefold symmetric amyloid fibrils. We calculate the elastic constants associated with torsional, bending, and tensile deformation as a function of the size of the amyloid fibril, covering fibril lengths ranging from nanometers to micrometers. The resulting Young's moduli are found to be consistent with available experimental measurements obtained from long amyloid fibrils, and predicted to be in the range of 20–31 GPa. Our results show that Aβ(1-40) amyloid fibrils feature a remarkable structural stability and mechanical rigidity for fibrils longer than ≈100 nm. However, local instabilities that emerge at the ends of short fibrils (on the order of tens of nanometers) reduce their stability and contribute to their disassociation under extreme mechanical or chemical conditions, suggesting that longer amyloid fibrils are more stable. Moreover, we find that amyloids with lengths shorter than the periodicity of their helical pitch, typically between 90 and 130 nm, feature significant size effects of their bending stiffness due the anisotropy in the fibril's cross section. At even smaller lengths (⪅50 nm), shear effects dominate lateral deformation of amyloid fibrils

  9. Research of Mechanical Property Gradient Distribution of Al-Cu Alloy in Centrifugal Casting

    NASA Astrophysics Data System (ADS)

    Sun, Zhi; Sui, Yanwei; Liu, Aihui; Li, Bangsheng; Guo, Jingjie

    Al-Cu alloy castings are obtained using centrifugal casting. The regularity of mechanical property gradient distribution of Al-Cu alloy castings with the same centrifugal radius at different positions is investigated. The result shows that the tensile strength, yield strength, elongation and microscope hardness exhibit the following gradient distribution characteristic — high on both sides and low on the center. The trend of mechanical property gradient distribution of Al-Cu alloy increases with the increase in the rotation speed. Moreover, the mechanical properties of casting centerline two sides have asymmetry. The reason is that the grain size of casting centerline two sides and Al2Cu phase and Cu content change correspondingly.

  10. Static, rheological and mechanical properties of polymer nanocomposites studied by computer modeling and simulation.

    PubMed

    Liu, Jun; Zhang, Liqun; Cao, Dapeng; Wang, Wenchuan

    2009-12-28

    Polymer nanocomposites (PNCs) often exhibit excellent mechanical, thermal, electrical and optical properties, because they combine the performances of both polymers and inorganic or organic nanoparticles. Recently, computer modeling and simulation are playing an important role in exploring the reinforcement mechanism of the PNCs and even the design of functional PNCs. This report provides an overview of the progress made in past decades in the investigation of the static, rheological and mechanical properties of polymer nanocomposites studied by computer modeling and simulation. Emphases are placed on exploring the mechanisms at the molecular level for the dispersion of nanoparticles in nanocomposites, the effects of nanoparticles on chain conformation and glass transition temperature (T(g)), as well as viscoelastic and mechanical properties. Finally, some future challenges and opportunities in computer modeling and simulation of PNCs are addressed.

  11. Mechanical and hydraulic properties of rocks related to induced seismicity

    USGS Publications Warehouse

    Witherspoon, P.A.; Gale, J.E.

    1977-01-01

    Witherspoon, P.A. and Gale, J.E., 1977. Mechanical and hydraulic properties of rocks related to induced seismicity. Eng. Geol., 11(1): 23-55. The mechanical and hydraulic properties of fractured rocks are considered with regard to the role they play in induced seismicity. In many cases, the mechanical properties of fractures determine the stability of a rock mass. The problems of sampling and testing these rock discontinuities and interpreting their non-linear behavior are reviewed. Stick slip has been proposed as the failure mechanism in earthquake events. Because of the complex interactions that are inherent in the mechanical behavior of fractured rocks, there seems to be no simple way to combine the deformation characteristics of several sets of fractures when there are significant perturbations of existing conditions. Thus, the more important fractures must be treated as individual components in the rock mass. In considering the hydraulic properties, it has been customary to treat a fracture as a parallel-plate conduit and a number of mathematical models of fracture systems have adopted this approach. Non-steady flow in fractured systems has usually been based on a two-porosity model, which assumes the primary (intergranular) porosity contributes only to storage and the secondary (fracture) porosity contributes only to the overall conductivity. Using such a model, it has been found that the time required to achieve quasi-steady state flow in a fractured reservoir is one or two orders of magnitude greater than it is in a homogeneous system. In essentially all of this work, the assumption has generally been made that the fractures are rigid. However, it is clear from a review of the mechanical and hydraulic properties that not only are fractures easily deformed but they constitute the main flow paths in many rock masses. This means that one must consider the interaction of mechanical and hydraulic effects. A considerable amount of laboratory and field data is now

  12. Accurate forced-choice recognition without awareness of memory retrieval.

    PubMed

    Voss, Joel L; Baym, Carol L; Paller, Ken A

    2008-06-01

    Recognition confidence and the explicit awareness of memory retrieval commonly accompany accurate responding in recognition tests. Memory performance in recognition tests is widely assumed to measure explicit memory, but the generality of this assumption is questionable. Indeed, whether recognition in nonhumans is always supported by explicit memory is highly controversial. Here we identified circumstances wherein highly accurate recognition was unaccompanied by hallmark features of explicit memory. When memory for kaleidoscopes was tested using a two-alternative forced-choice recognition test with similar foils, recognition was enhanced by an attentional manipulation at encoding known to degrade explicit memory. Moreover, explicit recognition was most accurate when the awareness of retrieval was absent. These dissociations between accuracy and phenomenological features of explicit memory are consistent with the notion that correct responding resulted from experience-dependent enhancements of perceptual fluency with specific stimuli--the putative mechanism for perceptual priming effects in implicit memory tests. This mechanism may contribute to recognition performance in a variety of frequently-employed testing circumstances. Our results thus argue for a novel view of recognition, in that analyses of its neurocognitive foundations must take into account the potential for both (1) recognition mechanisms allied with implicit memory and (2) recognition mechanisms allied with explicit memory.

  13. Dynamic Mechanical Properties of Bio-Polymer Graphite Thin Films

    NASA Astrophysics Data System (ADS)

    Saddam Kamarudin, M.; Rus, Anika Zafiah M.; Munirah Abdullah, Nur; Abdullah, M. F. L.

    2017-08-01

    Waste cooking oil is used as the main substances in producing graphite biopolymer thin films. Biopolymer is produce from the reaction of bio-monomer and cross linker with the ratio of 2:1 and addition of graphite with an increment of 2% through a slip casting method. The morphological surface properties of the samples are observed by using Scanning Electron Microscope (SEM). It is shown that the graphite particle is well mixed and homogenously dispersed in biopolymer matrix. Meanwhile, the mechanical response of materials by monitoring the change in the material properties in terms of frequency and temperature of the samples were determined using Dynamic Mechanical Analysis (DMA). The calculated cross-linked density of biopolymer composites revealed the increment of graphite particle loading at 8% gives highest results with 260.012 x 103 M/m3.

  14. Traceable measurements of small forces and local mechanical properties

    NASA Astrophysics Data System (ADS)

    Campbellová, Anna; Valtr, Miroslav; Zůda, Jaroslav; Klapetek, Petr

    2011-09-01

    Measurement of local mechanical properties is an important topic in the fields of nanoscale device fabrication, thin film deposition and composite material development. Nanoindentation instruments are commonly used to study hardness and related mechanical properties at the nanoscale. However, traceability and uncertainty aspects of the measurement process often remain left aside. In this contribution, the use of a commercial nanoindentation instrument for metrology purposes will be discussed. Full instrument traceability, provided using atomic force microscope cantilevers and a mass comparator (normal force), interferometer (depth) and atomic force microscope (area function) is described. The uncertainty of the loading/unloading curve measurements will be analyzed and the resulting uncertainties for quantities, that are computed from loading curves such as hardness or elastic modulus, are studied. For this calculation a combination of uncertainty propagation law and Monte Carlo uncertainty evaluations are used.

  15. Influence of cross-link structure, density and mechanical properties in the mesoscale deformation mechanisms of collagen fibrils.

    PubMed

    Depalle, Baptiste; Qin, Zhao; Shefelbine, Sandra J; Buehler, Markus J

    2015-12-01

    Collagen is a ubiquitous protein with remarkable mechanical properties. It is highly elastic, shows large fracture strength and enables substantial energy dissipation during deformation. Most of the connective tissue in humans consists of collagen fibrils composed of a staggered array of tropocollagen molecules, which are connected by intermolecular cross-links. In this study, we report a three-dimensional coarse-grained model of collagen and analyze the influence of enzymatic cross-links on the mechanics of collagen fibrils. Two representatives immature and mature cross-links are implemented in the mesoscale model using a bottom-up approach. By varying the number, type and mechanical properties of cross-links in the fibrils and performing tensile test on the models, we systematically investigate the deformation mechanisms of cross-linked collagen fibrils. We find that cross-linked fibrils exhibit a three phase behavior, which agrees closer with experimental results than what was obtained using previous models. The fibril mechanical response is characterized by: (i) an initial elastic deformation corresponding to the collagen molecule uncoiling, (ii) a linear regime dominated by molecule sliding and (iii) the second stiffer elastic regime related to the stretching of the backbone of the tropocollagen molecules until the fibril ruptures. Our results suggest that both cross-link density and type dictate the stiffness of large deformation regime by increasing the number of interconnected molecules while cross-links mechanical properties determine the failure strain and strength of the fibril. These findings reveal that cross-links play an essential role in creating an interconnected fibrillar material of tunable toughness and strength. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

  16. Influence of gaseous hydrogen on the mechanical properties of high temperature alloys

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Tensile tests of six nickel-base and one cobalt-base alloy were conducted in 34.5 MN/sq m helium and hydrogen environments at temperatures from 297 K to 1,088 K. Mechanical properties tests of the nickel-base alloy MAR M-246 (Hf modified), in two cast conditions, were conducted in gaseous environments at temperatures from 297 K to 1,144 K and pressures from one atmosphere to 34.5 MN/sq m. The objective of this program was to obtain the mechanical properties of the various alloys proposed for use in space propulsion systems in a pure hydrogen environment at different temperatures and to compare with the mechanical properties in helium at the same conditions. All testing was conducted on solid specimens exposed to external gaseous pressure. Smooth and notched tensile properties were determined using ASTM tensile testing techniques, and creep-rupture life was determined using ASTM creep-rupture techniques. Low-cycle fatigue life was established by constant total strain and constant stress testing using smooth specimens and a closed-loop test machine.

  17. Review of the physical and mechanical properties and potential applications of the B2 compound NiAl: Unabridged version of a paper published in International materials review

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald D.; Bowman, Randy R.; Nathal, Michael V.

    1992-01-01

    Considerable work has been performed on NiAl over the last three decades, with an extremely rapid growth in research on this intermetallic occurring in the last few years due to recent interest in this material for electronic and high temperature structural applications. However, many physical properties and the controlling fracture and deformation mechanisms over certain temperature regimes are still in question. Part of this problem lies in the incomplete characterization of many of the alloys previously investigated. Fragmentary data on processing conditions, chemistry, microstructure and the apparent difficulty in accurately measuring composition has made direct comparison between individual studies sometimes tenuous. Therefore, the purpose of this review is to summarize all available mechanical and pertinent physical properties on NiAl, stressing the most recent investigations, in an attempt to understand the behavior of NiAl and its alloys over a broad temperature range.

  18. Quantum Mechanical Approach to Understanding Structural, Electronic and Mechanical Properties of Intermetallics

    DTIC Science & Technology

    1989-01-26

    Understanding Structural , Electronic and Mechanical Properties of Tntermetallics by A.J. Freeman, Principal Investigator ABSTRACT The primary goal of...like LI or Mg would lower EF into the minimum in the DOS and hence stabilize the L1 2 . A. Structural Phase Stability of Titanium Aluminides Most...34 Structural Stability Calculations in the Titanium -Aluminium System", Conf. on Titanium Aluminides , Wright-Patterson Air Force Base, Nov. 1986

  19. Injection Molding and Mechanical Properties of Bio-Based Polymer Nanocomposites.

    PubMed

    Mistretta, Maria Chiara; Botta, Luigi; Morreale, Marco; Rifici, Sebastiano; Ceraulo, Manuela; La Mantia, Francesco Paolo

    2018-04-17

    The use of biodegradable/bio-based polymers is of great importance in addressing several issues related to environmental protection, public health, and new, stricter legislation. Yet some applications require improved properties (such as barrier or mechanical properties), suggesting the use of nanosized fillers in order to obtain bio-based polymer nanocomposites. In this work, bionanocomposites based on two different biodegradable polymers (coming from the Bioflex and MaterBi families) and two different nanosized fillers (organo-modified clay and hydrophobic-coated precipitated calcium carbonate) were prepared and compared with traditional nanocomposites with high-density polyethylene (HDPE) as matrix. In particular, the injection molding processability, as well as the mechanical and rheological properties of the so-obtained bionanocomposites were investigated. It was found that the processability of the two biodegradable polymers and the related nanocomposites can be compared to that of the HDPE-based systems and that, in general, the bio-based systems can be taken into account as suitable alternatives.

  20. Controlling the mechanical properties of carbon steel by thermomechanical treatment

    NASA Astrophysics Data System (ADS)

    Balavar, Mohsen; Mirzadeh, Hamed

    2018-01-01

    The effect of thermomechanical processing and heat treatment on the microstructure and mechanical properties of low carbon steel was studied. It was revealed that the dual phase ferritic-martensitic microstructure shows a good combination of tensile strength and ductility along with superior work hardening response. On the other hand, the bimodal-sized structure containing ultrafine grained (UFG) and micron-sized ferrite phase can be easily produced by cold rolling and annealing of the dual phase starting microstructure. This steel showed high yield stress, tensile strength, and ductility, but poor work hardening ability. The full annealed ferritic-pearlitic sheet with banded morphology exhibited low strength and high total elongation with the appearance of the yield point phenomenon. The martensitic steels, however, had high tensile strength and low ductility. By comparing the tensile properties of these steels, it was shown that it is possible to control the mechanical properties of low carbon steel by simple processing routes.

  1. Injection Molding and Mechanical Properties of Bio-Based Polymer Nanocomposites

    PubMed Central

    Mistretta, Maria Chiara; Rifici, Sebastiano; Ceraulo, Manuela

    2018-01-01

    The use of biodegradable/bio-based polymers is of great importance in addressing several issues related to environmental protection, public health, and new, stricter legislation. Yet some applications require improved properties (such as barrier or mechanical properties), suggesting the use of nanosized fillers in order to obtain bio-based polymer nanocomposites. In this work, bionanocomposites based on two different biodegradable polymers (coming from the Bioflex and MaterBi families) and two different nanosized fillers (organo-modified clay and hydrophobic-coated precipitated calcium carbonate) were prepared and compared with traditional nanocomposites with high-density polyethylene (HDPE) as matrix. In particular, the injection molding processability, as well as the mechanical and rheological properties of the so-obtained bionanocomposites were investigated. It was found that the processability of the two biodegradable polymers and the related nanocomposites can be compared to that of the HDPE-based systems and that, in general, the bio-based systems can be taken into account as suitable alternatives. PMID:29673143

  2. Mechanical properties and the electronic structure of transition of metal alloys

    NASA Technical Reports Server (NTRS)

    Arsenault, R. J.; Drew, H. D.

    1977-01-01

    This interdiscipline research program was undertaken in an effort to investigate the relationship between the mechanical strength of Mo based alloys with their electronic structure. Electronic properties of these alloys were examined through optical studies, and the classical solid solution strengthening mechanisms were considered, based on size and molecular differences to determine if these mechanisms could explain the hardness data.

  3. Quantification and comparison of the mechanical properties of four human cardiac valves.

    PubMed

    Pham, Thuy; Sulejmani, Fatiesa; Shin, Erica; Wang, Di; Sun, Wei

    2017-05-01

    Although having the same ability to permit unidirectional flow within the heart, the four main valves-the mitral valve (MV), aortic (AV), tricuspid (TV) and pulmonary (PV) valves-experience different loading conditions; thus, they exhibit different structural integrity from one another. Most research on heart valve mechanics have been conducted mainly on MV and AV or an individual valve, but none quantify and compare the mechanical and structural properties among the four valves from the same aged patient population whose death was unrelated to cardiovascular disease. A total of 114 valve leaflet samples were excised from 12 human cadavers whose death was unrelated to cardiovascular disease (70.1±3.7years old). Tissue mechanical and structural properties were characterized by planar biaxial mechanical testing and histological methods. The experimental data were then fitted with a Fung-type constitutive model. The four valves differed substantially in thickness, degree of anisotropy, and stiffness. The leaflets of the left heart (the AV leaflets and the anterior mitral leaflets, AML) were significantly stiffer and less compliant than their counterparts in the right heart. TV leaflets were the most extensible and isotropic, while AML and AV leaflets were the least extensible and the most anisotropic. Age plays a significant role in the reduction of leaflet stiffness and extensibility with nearly straightened collagen fibers observed in the leaflet samples from elderly groups (65years and older). Results from 114 human leaflet samples not only provided a baseline quantification of the mechanical properties of aged human cardiac valves, but also offered a better understanding of the age-dependent differences among the four valves. It is hoped that the experimental data collected and the associated constitutive models in this study can facilitate future studies of valve diseases, treatments and the development of interventional devices. Most research on heart valve

  4. Hydrothermal effect and mechanical stress properties of carboxymethylcellulose based hydrogel food packaging.

    PubMed

    Gregorova, Adriana; Saha, Nabanita; Kitano, Takeshi; Saha, Petr

    2015-03-06

    The PVP-CMC hydrogel film is biodegradable, transparent, flexible, hygroscopic and breathable material which can be used as a food packaging material. The hygroscopic character of CMC and PVP plays a big role in the changing of their mechanical properties where load carrying capacity is one of important criteria for packaging materials. This paper reports about the hydrothermal effect on the mechanical and viscoelastic properties of neat CMC, and PVP-CMC (20:80) hydrogel films under the conditions of combined multiple stress factors such as temperature, time, load, frequency and humidity. The dry films were studied by transient and dynamic oscillatory experiments using dynamic mechanical analyser combined with relative humidity chamber (DMA-RH). The mechanical properties of PVP-CMC hydrogel film at room temperature (25 °C), in the range of 0-30%RH remain steady. The 20 wt% of PVP in PVP-CMC hydrogel increases the stiffness of CMC from 2940 to 3260 MPa at 25 °C and 10%RH. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Temperature effects on nanostructure and mechanical properties of single-nanoparticle thick membranes.

    DOE PAGES

    Salerno, Kenneth Michael; Grest, Gary S.

    2015-04-30

    In this study, the properties of mechanically stable single-nanoparticle (NP)-thick membranes have largely been studied at room temperature. How these membranes soften as nanoparticle ligands disorder with increasing temperature is unknown. Molecular dynamics simulations are used to probe the temperature dependence of the mechanical and nanostructural properties of nanoparticle membranes made of 6 nm diameter Au nanoparticles coated with dodecanethiol ligands and terminated with either methyl (CH 3) or carboxyl (COOH) terminal groups. For methyl-terminated ligands, interactions along the alkane chain provide mechanical stiffness, with a Young's modulus of 1.7 GPa at 300 K. For carboxyl-terminated chains, end-group interactions aremore » significant, producing stiffer membranes at all temperatures, with a Young's modulus of 3.8 GPa at 300 K. For both end-group types, membrane stiffness is reduced to zero at about 400 K. Ligand structure and mechanical properties of membranes at 300 K that have been annealed at 400 K are comparable to samples that do not undergo thermal annealing.« less

  6. Optimisation of mechanical properties of bamboo fibre reinforced-PLA biocomposites

    NASA Astrophysics Data System (ADS)

    Nurnadia M., J.; Fazita, M. R. Nurul; Abdul Khalil H. P., S.; Mohamad Haafiz M., K.

    2017-12-01

    The majority of the raw materials that have been widely used in industries are petroleum-based. Growing environmental awareness, the depletion of fossil fuels, and climate change are the key drivers to seek more ecologically friendly materials, such as natural fibres to replace synthetic fibres in polymeric composite. Among the natural fibres available, bamboo fibre has relatively high strength. Poly (lactic) acid (PLA), one of the well-known biopolymers, has been used as a matrix in order to produce totally biodegradable biocomposites. In this study, bamboo fibres were compounded with PLA by a twin screw extruder. The bamboo fibre reinforced PLA composites were then manufactured via the compression moulding method. The influences of screw speed and die temperature during extrusion on the mechanical properties, the tensile and flexural of the biocomposites, were studied. The effects of fibre content and fibre length were also investigated. Taguchi experimental design approach was adopted to determine the optimum set of conditions to achieve the "best" mechanical properties of the composites. Tensile and flexural properties were characterised based on the D638-10 and D790-10 standards, respectively. It was observed that the fibre aspect ratio and fibre content significantly affected the mechanical performance of bamboo fibres reinforced PLA composites.

  7. Study of the microstructure and mechanical properties of white clam shell.

    PubMed

    Liang, Yunhong; Zhao, Qian; Li, Xiujuan; Zhang, Zhihui; Ren, Luquan

    2016-08-01

    The microstructure and mechanical properties of white clam shell were investigated, respectively. It can be divided into horny layer, prismatic layer and nacreous layer. Crossed-lamellar structure was the microstructural characteristic. The extension direction of lamellae in prismatic layer was different from that in nacreous layer, which formed an angle on the interface between prismatic layer and nacreous layer. The phase component of three layers was CaCO3 with crystallization morphology of aragonite, which confirmed the crossed-lamellar structural characteristic. White calm shell exhibited perfect mechanical properties. The microhardness values of three layers were 273HV, 240HV and 300HV, respectively. The average values of flexure and compression strength were 110.2MPa and 80.1MPa, respectively. The macroscopical cracks crossed the lamellae and finally terminated within the length range of about 80μm. It was the microstructure characteristics, the angle on the interface between prismatic and nacreous layer and the hardness diversity among the different layers that enhanced mechanical properties of white calm shell. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Mechanical properties of the in vivo adolescent human brain.

    PubMed

    McIlvain, Grace; Schwarb, Hillary; Cohen, Neal J; Telzer, Eva H; Johnson, Curtis L

    2018-06-10

    Viscoelastic mechanical properties of the in vivo human brain, measured noninvasively with magnetic resonance elastography (MRE), have recently been shown to be affected by aging and neurological disease, as well as relate to performance on cognitive tasks in adults. The demonstrated sensitivity of brain mechanical properties to neural tissue integrity make them an attractive target for examining the developing brain; however, to date, MRE studies on children are lacking. In this work, we characterized global and regional brain stiffness and damping ratio in a sample of 40 adolescents aged 12-14 years, including the lobes of the cerebrum and subcortical gray matter structures. We also compared the properties of the adolescent brain to the healthy adult brain. Temporal and parietal cerebral lobes were softer in adolescents compared to adults. We found that of subcortical gray matter structures, the caudate and the putamen were significantly stiffer in adolescents, and that the hippocampus and amygdala were significantly less stiff than all other subcortical structures. This study provides the first detailed characterization of adolescent brain viscoelasticity and provides baseline data to be used in studying development and pathophysiology. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

  9. Effect of extrusion processing on the microstructure, mechanical properties, biocorrosion properties and antibacterial properties of Ti-Cu sintered alloys.

    PubMed

    Zhang, Erlin; Li, Shengyi; Ren, Jing; Zhang, Lan; Han, Yong

    2016-12-01

    Ti-Cu sintered alloys, Ti-Cu(S) alloy, have exhibited good anticorrosion resistance and strong antibacterial properties, but low ductility in previous study. In this paper, Ti-Cu(S) alloys were subjected to extrusion processing in order to improve the comprehensive property. The phase constitute, microstructure, mechanical property, biocorrosion property and antibacterial activity of the extruded alloys, Ti-Cu(E), were investigated in comparison with Ti-Cu(S) by X-ray diffraction (XRD), optical microscopy (OM), scanning electronic microscopy (SEM) with energy disperse spectroscopy (EDS), mechanical testing, electrochemical testing and plate-count method in order to reveal the effect of the extrusion process. XRD, OM and SEM results showed that the extrusion process did not change the phase constitute but refined the grain size and Ti2Cu particle significantly. Ti-Cu(E) alloys exhibited higher hardness and compressive yield strength than Ti-Cu(S) alloys due to the fine grain and Ti2Cu particles. With the consideration of the total compressive strain, it was suggested that the extrusion process could improve the ductility of Ti-Cu alloy(S) alloys. Electrochemical results have indicated that the extrusion process improved the corrosion resistance of Ti-Cu(S) alloys. Plate-count method displayed that both Ti-Cu(S) and Ti-Cu(E) exhibited strong antibacterial activity (>99%) against S. aureus. All these results demonstrated that hot forming processing, such as the extrusion in this study, refined the microstructure and densified the alloy, in turn improved the ductility and strength as well as anticorrosion properties without reduction in antibacterial properties. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Optical properties of hydroxyapatite obtained by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Silva, C. C.; Thomazini, D.; Pinheiro, A. G.; Lanciotti, F.; Sasaki, J. M.; Góes, J. C.; Sombra, A. S. B.

    2002-09-01

    Calcium phosphate based bioceramics, mainly in the form of hydroxyapatite (HA), have been in use in medicine and dentistry for the last 20 years. Applications include coatings of orthopaedic and dental implants, alveolar ridge augmentation, maxillofacial surgery, otolaryngology, and scaffolds for bone growth and as powders in total hip and knee surgery. These materials exhibit several problems of handling and fabrication, which can be overcome by mixing with a suitable binder. In this paper, mechanical alloying has been used successfully to produce nanocrystalline powders of HA using five different experimental procedures. The milled HA were studied by X-ray powder diffraction, infrared and Raman scattering spectroscopy. For four different procedures, HA was obtained after a couple of hours of milling (on an average, 20 h of milling depending on the reaction procedure). The XRD patterns indicate that the grain size is within the range of 29-103 nm. This milling process, used to produce HA, presents the advantage that melting is not necessary and the powder obtained is nanocrystalline with extraordinary mechanical properties. The material can be compacted and transformed in solid ceramic samples. The high efficiency of the process opens a way to produce commercial amount of nanocrystalline HA. Due to the nanocrystalline character of this powder, their mechanical properties have changed and for this reason a pressure of 1 GPa is enough to shape the sample into any geometry.

  11. Mechanical and wear properties of aluminum coating prepared by cold spraying

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yusof, Siti Nurul Akmal, E-mail: em-leo277@yahoo.com; Manap, Abreeza, E-mail: Abreeza@uniten.edu.my; Afandi, Nurfanizan Mohd

    In this study, aluminum (Al) powders were deposited onto Al substrates using cold spray to form a coating. The main objective is to investigate and compare the microstructure, mechanical and wear properties of Al coating to that of the Al substrate. The microstructure of the coating and substrate were observed using Scanning Electron Microscope (SEM). Hardness was evaluated using the Vickers Hardness test and wear properties were investigated using a pin-on-disk wear test machine. The elemental composition of the coating and substrate was determined using Energy-dispersive X-ray spectroscopy (EDX). Results showed that the friction coefficient and specific wear rate decreasedmore » while wear rate increased linearly with increasing load. It was found that the coating exhibit slightly better mechanical and wear properties compared to the substrate.« less

  12. Mass production of bulk artificial nacre with excellent mechanical properties.

    PubMed

    Gao, Huai-Ling; Chen, Si-Ming; Mao, Li-Bo; Song, Zhao-Qiang; Yao, Hong-Bin; Cölfen, Helmut; Luo, Xi-Sheng; Zhang, Fu; Pan, Zhao; Meng, Yu-Feng; Ni, Yong; Yu, Shu-Hong

    2017-08-18

    Various methods have been exploited to replicate nacre features into artificial structural materials with impressive structural and mechanical similarity. However, it is still very challenging to produce nacre-mimetics in three-dimensional bulk form, especially for further scale-up. Herein, we demonstrate that large-sized, three-dimensional bulk artificial nacre with comprehensive mimicry of the hierarchical structures and the toughening mechanisms of natural nacre can be facilely fabricated via a bottom-up assembly process based on laminating pre-fabricated two-dimensional nacre-mimetic films. By optimizing the hierarchical architecture from molecular level to macroscopic level, the mechanical performance of the artificial nacre is superior to that of natural nacre and many engineering materials. This bottom-up strategy has no size restriction or fundamental barrier for further scale-up, and can be easily extended to other material systems, opening an avenue for mass production of high-performance bulk nacre-mimetic structural materials in an efficient and cost-effective way for practical applications.Artificial materials that replicate the mechanical properties of nacre represent important structural materials, but are difficult to produce in bulk. Here, the authors exploit the bottom-up assembly of 2D nacre-mimetic films to fabricate 3D bulk artificial nacre with an optimized architecture and excellent mechanical properties.

  13. Microstructure and Mechanical Properties of Laser Welded Titanium 6Al-4V

    NASA Astrophysics Data System (ADS)

    Mazumder, J.; Steen, W. M.

    1982-05-01

    Laser butt welds were fabricated in a titanium alloy (Ti-6A1-4V, AMS 4911-Tal0 BSS, annealed) using a Control Laser 2 kW CW CO2 laser. The relationships between the weld microstructure and mechanical properties are described and compared to the theoretical thermal history of the weld zone as calculated from a three-dimensional heat transfer model of the process. The structure of the weld zone was examined by radiography to detect any gross porosity as well as by both optical and electron microscopy in order to identify the microstructure. The oxygen pick-up during gas shielded laser welding was analyzed to correlate further with the observed mechanical properties. It was found that optimally fabricated laser welds have a very good combination of weld microstructure and mechanical properties, ranking this process as one which can produce high quality welds.

  14. Centrifugal forming and mechanical properties of silicone-based elastomers for soft robotic actuators

    NASA Astrophysics Data System (ADS)

    Kulkarni, Parth

    This thesis describes the centrifugal forming and resulting mechanical properties of silicone-based elastomers for the manufacture of soft robotic actuators. This process is effective at removing bubbles that get entrapped within 3D-printed, enclosed molds. Conventional methods for rapid prototyping of soft robotic actuators to remove entrapped bubbles typically involve degassing under vacuum, with open-faced molds that limit the layout of formed parts to raised 2D geometries. As the functionality and complexity of soft robots increase, there is a need to mold complete 3D structures with controlled thicknesses or curvatures on multiples surfaces. In addition, characterization of the mechanical properties of common elastomers for these soft robots has lagged the development of new designs. As such, relationships between resulting material properties and processing parameters are virtually non-existent. One of the goals of this thesis is to provide guidelines and physical insights to relate the design, processing conditions, and resulting properties of soft robotic components to each other. Centrifugal forming with accelerations on the order of 100 g's is capable of forming bubble-free, true 3D components for soft robotic actuators, and resulting demonstrations in this work include an aquatic locomotor, soft gripper, and an actuator that straightens when pressurized. Finally, this work shows that the measured mechanical properties of 3D geometries fabricated within enclosed molds through centrifugal forming possess comparable mechanical properties to vacuumed materials formed from open-faced molds with raised 2D features.

  15. Thermodynamics and statistical mechanics. [thermodynamic properties of gases

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The basic thermodynamic properties of gases are reviewed and the relations between them are derived from the first and second laws. The elements of statistical mechanics are then formulated and the partition function is derived. The classical form of the partition function is used to obtain the Maxwell-Boltzmann distribution of kinetic energies in the gas phase and the equipartition of energy theorem is given in its most general form. The thermodynamic properties are all derived as functions of the partition function. Quantum statistics are reviewed briefly and the differences between the Boltzmann distribution function for classical particles and the Fermi-Dirac and Bose-Einstein distributions for quantum particles are discussed.

  16. Fractography and Mechanical Properties of Urethane Dimethacrylate Dental Composites Reinforced with Glass Nanoparticles.

    PubMed

    M, Monfared; Me, Bahrololoom

    2016-12-01

    Dental resin composites are becoming prevalent in restorative dentistry and have almost replaced amalgam nowadays. Consequently, their mechanical properties and durability are critical. The aim of this study was to produce Pyrex glass nano-particles by wet milling process and use them as reinforcement in dental resins for anterior restorations and then examination of fractographic properties of these composites. The glass nano-particles were achieved via wet milling. The surface of the particles was modified with 3-(Trimethoxysilyl) propyl methacrylate (γ-MPTMS) silane in order to improve their surface. Fourier transform infra-red (FTIR) analysis showed that the silane groups provided double bonds to the surface of the particles and prevented agglomeration. Then, the composite resins were made with different weight percentages of Pyrex glass. The mechanical properties of samples flexural test were evaluated. The required energy for fracture of the specimens was achieved via this test. The fracture surfaces of the samples were analyzed using a scanning electron microscope (SEM) in order to explain the mechanisms of fracture. The results and analysis showed that increasing the glass nano-particles mass fraction had a great effect on mechanical properties of the composites due to the mechanisms of crack propagation and crack deflection as well as preventing void formation. The effective energy dissipation mechanisms such as crack pinning and deflection, was observed in SEM micrographs. Void formation in the low filler content composite is one of the mechanisms to decrease the energy required for fracture of these composites and eventually weaken them.

  17. Fractography and Mechanical Properties of Urethane Dimethacrylate Dental Composites Reinforced with Glass Nanoparticles

    PubMed Central

    M*, Monfared; ME, Bahrololoom

    2016-01-01

    Statement of Problem: Dental resin composites are becoming prevalent in restorative dentistry and have almost replaced amalgam nowadays. Consequently, their mechanical properties and durability are critical. Objectives: The aim of this study was to produce Pyrex glass nano-particles by wet milling process and use them as reinforcement in dental resins for anterior restorations and then examination of fractographic properties of these composites. Materials and Methods: The glass nano-particles were achieved via wet milling. The surface of the particles was modified with 3-(Trimethoxysilyl) propyl methacrylate (γ-MPTMS) silane in order to improve their surface. Fourier transform infra-red (FTIR) analysis showed that the silane groups provided double bonds to the surface of the particles and prevented agglomeration. Then, the composite resins were made with different weight percentages of Pyrex glass. The mechanical properties of samples flexural test were evaluated. The required energy for fracture of the specimens was achieved via this test. The fracture surfaces of the samples were analyzed using a scanning electron microscope (SEM) in order to explain the mechanisms of fracture. Results: The results and analysis showed that increasing the glass nano-particles mass fraction had a great effect on mechanical properties of the composites due to the mechanisms of crack propagation and crack deflection as well as preventing void formation. The effective energy dissipation mechanisms such as crack pinning and deflection, was observed in SEM micrographs. Conclusions: Void formation in the low filler content composite is one of the mechanisms to decrease the energy required for fracture of these composites and eventually weaken them. PMID:28959761

  18. Microstructure, Mechanical and Corrosion Properties of Friction Stir-Processed AISI D2 Tool Steel

    NASA Astrophysics Data System (ADS)

    Yasavol, Noushin; Jafari, Hassan

    2015-05-01

    In this study, AISI D2 tool steel underwent friction stir processing (FSP). The microstructure, mechanical properties, and corrosion resistance of the FSPed materials were then evaluated. A flat WC-Co tool was used; the rotation rate of the tool varied from 400 to 800 rpm, and the travel speed was maintained constant at 385 mm/s during the process. FSP improved mechanical properties and produced ultrafine-grained surface layers in the tool steel. Mechanical properties improvement is attributed to the homogenous distribution of two types of fine (0.2-0.3 μm) and coarse (1.6 μm) carbides in duplex ferrite-martensite matrix. In addition to the refinement of the carbides, the homogenous dispersion of the particles was found to be more effective in enhancing mechanical properties at 500 rpm tool rotation rate. The improved corrosion resistance was observed and is attributed to the volume fraction of low-angle grain boundaries produced after friction stir process of the AISI D2 steel.

  19. Statistical Analysis on the Mechanical Properties of Magnesium Alloys

    PubMed Central

    Liu, Ruoyu; Jiang, Xianquan; Zhang, Hongju; Zhang, Dingfei; Wang, Jingfeng; Pan, Fusheng

    2017-01-01

    Knowledge of statistical characteristics of mechanical properties is very important for the practical application of structural materials. Unfortunately, the scatter characteristics of magnesium alloys for mechanical performance remain poorly understood until now. In this study, the mechanical reliability of magnesium alloys is systematically estimated using Weibull statistical analysis. Interestingly, the Weibull modulus, m, of strength for magnesium alloys is as high as that for aluminum and steels, confirming the very high reliability of magnesium alloys. The high predictability in the tensile strength of magnesium alloys represents the capability of preventing catastrophic premature failure during service, which is essential for safety and reliability assessment. PMID:29113116

  20. Effect of sintering process on the magnetic and mechanical properties of sintered Nd-Fe-B magnets

    NASA Astrophysics Data System (ADS)

    Hu, Z. H.; Qu, H. J.; Zhao, J. Q.; Yan, C. J.; Liu, X. M.

    2014-11-01

    The magnetic and mechanical properties of sintered Nd-Fe-B magnets prepared by different sintering processes were investigated. The results showed that the intrinsic coercivity and fracture toughness of sintered Nd-Fe-B magnets first increased, and then declined with increasing annealing temperature. The optimum magnetic properties and fracture toughness of sintered Nd-Fe-B magnets were obtained at the annealing temperature of 540 °C. Sintering temperature increasing from 1047 °C to 1071 °C had hardly effect on the magnetic properties of sintered Nd-Fe-B magnets. The variation of Vickers hardness and fracture toughness was not the same with increasing sintering temperature, and the effect of sintering temperature on the mechanical properties was complex and irregular. The reasons for the variation on magnetic and mechanical properties were analyzed, and we presumed that the effect of microstructure on the mechanical properties was more sensitive than the magnetic properties through analyzing the microstructure of sintered Nd-Fe-B magnets.

  1. Determining Tension-Compression Nonlinear Mechanical Properties of Articular Cartilage from Indentation Testing.

    PubMed

    Chen, Xingyu; Zhou, Yilu; Wang, Liyun; Santare, Michael H; Wan, Leo Q; Lu, X Lucas

    2016-04-01

    The indentation test is widely used to determine the in situ biomechanical properties of articular cartilage. The mechanical parameters estimated from the test depend on the constitutive model adopted to analyze the data. Similar to most connective tissues, the solid matrix of cartilage displays different mechanical properties under tension and compression, termed tension-compression nonlinearity (TCN). In this study, cartilage was modeled as a porous elastic material with either a conewise linear elastic matrix with cubic symmetry or a solid matrix reinforced by a continuous fiber distribution. Both models are commonly used to describe the TCN of cartilage. The roles of each mechanical property in determining the indentation response of cartilage were identified by finite element simulation. Under constant loading, the equilibrium deformation of cartilage is mainly dependent on the compressive modulus, while the initial transient creep behavior is largely regulated by the tensile stiffness. More importantly, altering the permeability does not change the shape of the indentation creep curves, but introduces a parallel shift along the horizontal direction on a logarithmic time scale. Based on these findings, a highly efficient curve-fitting algorithm was designed, which can uniquely determine the three major mechanical properties of cartilage (compressive modulus, tensile modulus, and permeability) from a single indentation test. The new technique was tested on adult bovine knee cartilage and compared with results from the classic biphasic linear elastic curve-fitting program.

  2. Effect of casting geometry on mechanical properties of two nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Johnston, J. R.; Dreshfield, R. L.; Collins, H. E.

    1976-01-01

    An investigation was performed to determine mechanical properties of two rhenium-free modifications of alloy TRW, and to evaluate the suitability of the alloy for use in a small integrally cast turbine rotor. The two alloys were initially developed using stress rupture properties of specimens machined from solid gas turbine blades. Properties in this investigation were determined from cast to size bars and bars cut from 3.8 by 7.6 by 17.8 cm blocks. Specimens machined from blocks had inferior tensile strength and always had markedly poorer rupture lives than cast to size bars. At 1,000 C the cast to size bars had shorter rupture lives than those machined from blades. Alloy R generally had better properties than alloy S in the conditions evaluated. The results show the importance of casting geometry on mechanical properties of nickel base superalloys and suggest that the geometry of a component can be simulated when developing alloys for that component.

  3. Shedding light on the variability of optical skin properties: finding a path towards more accurate prediction of light propagation in human cutaneous compartments

    PubMed Central

    Mignon, C.; Tobin, D. J.; Zeitouny, M.; Uzunbajakava, N. E.

    2018-01-01

    Finding a path towards a more accurate prediction of light propagation in human skin remains an aspiration of biomedical scientists working on cutaneous applications both for diagnostic and therapeutic reasons. The objective of this study was to investigate variability of the optical properties of human skin compartments reported in literature, to explore the underlying rational of this variability and to propose a dataset of values, to better represent an in vivo case and recommend a solution towards a more accurate prediction of light propagation through cutaneous compartments. To achieve this, we undertook a novel, logical yet simple approach. We first reviewed scientific articles published between 1981 and 2013 that reported on skin optical properties, to reveal the spread in the reported quantitative values. We found variations of up to 100-fold. Then we extracted the most trust-worthy datasets guided by a rule that the spectral properties should reflect the specific biochemical composition of each of the skin layers. This resulted in the narrowing of the spread in the calculated photon densities to 6-fold. We conclude with a recommendation to use the identified most robust datasets when estimating light propagation in human skin using Monte Carlo simulations. Alternatively, otherwise follow our proposed strategy to screen any new datasets to determine their biological relevance. PMID:29552418

  4. A Review of the Mechanical Properties of Concrete Containing Biofillers

    NASA Astrophysics Data System (ADS)

    Ezdiani Mohamad, Mazizah; Mahmood, Ali A.; Min, Alicia Yik Yee; Khalid, Nur Hafizah A.

    2016-11-01

    Sustainable construction is a rapidly increasing research area. Investigators of all backgrounds are using industrial and agro wastes to replace Portland cement in concrete to reduce greenhouse emissions and the corresponding decline in general health. Many types of wastes have been used as cement replacements in concrete including: fly ash, slag and rice husk ash in addition to others. This study investigates the possibility of producing a sustainable approach to construction through the partial replacement of concrete using biofillers. This will be achieved by studying the physical and mechanical properties of two widely available biological wastes in Malaysia; eggshell and palm oil fuel ash (POFA). The mechanical properties tests that were studied and compared are the compression, tensile and flexural tests.

  5. Optimising mechanical properties of hot forged nickel superalloy 625 components

    NASA Astrophysics Data System (ADS)

    Singo, Nthambe; Coles, John; Rosochowska, Malgorzata; Lalvani, Himanshu; Hernandez, Jose; Ion, William

    2018-05-01

    Hot forging and subsequent heat treatment were resulting in substandard mechanical properties of nickel superalloy, Alloy 625, components. The low strength was found to be due to inadequate deformation during forging, excessive grain growth and precipitation of carbides during subsequent heat treatment. Experimentation in a drop forging company and heat treatment facility led to the establishment of optimal parameters to minimise grain size and mitigate the adverse effects of carbide precipitation, leading to successful fulfilment of mechanical property specifications. This was achieved by reducing the number of operations, maximising the extent of deformation by changing the slug dimensions and its orientation in the die, and minimising the time of exposure to elevated temperatures in both the forging and subsequent heat treatment processes to avoid grain growth.

  6. Improved dielectric properties, mechanical properties, and thermal conductivity properties of polymer composites via controlling interfacial compatibility with bio-inspired method

    NASA Astrophysics Data System (ADS)

    Ruan, Mengnan; Yang, Dan; Guo, Wenli; Zhang, Liqun; Li, Shuxin; Shang, Yuwei; Wu, Yibo; Zhang, Min; Wang, Hao

    2018-05-01

    Surface functionalization of Al2O3 nano-particles by mussel-inspired poly(dopamine) (PDA) was developed to improve the dielectric properties, mechanical properties, and thermal conductivity properties of nitrile rubber (NBR) matrix. As strong adhesion of PDA to Al2O3 nano-particles and hydrogen bonds formed by the catechol groups of PDA and the polar acrylonitrile groups of NBR, the dispersion of Al2O3-PDA/NBR composites was improved and the interfacial force between Al2O3-PDA and NBR matrix was enhanced. Thus, the Al2O3-PDA/NBR composites exhibited higher dielectric constant, better mechanical properties, and larger thermal conductivity comparing with Al2O3/NBR composites at the same filler content. The largest thermal conductivity of Al2O3-PDA/NBR composite filled with 30 phr Al2O3-PDA was 0.21 W/m K, which was 122% times of pure NBR. In addition, the Al2O3-PDA/NBR composite filled with 30 phr Al2O3-PDA displayed a high tensile strength about 2.61 MPa, which was about 255% of pure NBR. This procedure is eco-friendly and easy handling, which provides a promising route to polymer composites in application of thermal conductivity field.

  7. Improvement in Mechanical Properties through Structural Hierarchies in Bio-Inspired Materials

    DTIC Science & Technology

    2011-02-01

    alloys , ceramics and their composites which show improvement in one mechanical property (e.g. stiffness) at the cost of another disparate one (e.g... properties of their base constituents. This is in contrast to many engineering materials, such as metals, alloys , ceramics and their composites which show...mnechanical properties seen in many synthetic nanoma- Collagen (a) Ccellous bone Collagen Collagen Lamella fibr ibi Cortical nBone Osteon C Crystak H I nm

  8. Modeling the mechanical properties of DNA nanostructures.

    PubMed

    Arbona, Jean Michel; Aimé, Jean-Pierre; Elezgaray, Juan

    2012-11-01

    We discuss generalizations of a previously published coarse-grained description [Mergell et al., Phys. Rev. E 68, 021911 (2003)] of double stranded DNA (dsDNA). The model is defined at the base-pair level and includes the electrostatic repulsion between neighbor helices. We show that the model reproduces mechanical and elastic properties of several DNA nanostructures (DNA origamis). We also show that electrostatic interactions are necessary to reproduce atomic force microscopy measurements on planar DNA origamis.

  9. Investigating the dental toolkit of primates based on food mechanical properties: Feeding action does matter.

    PubMed

    Thiery, Ghislain; Guy, Franck; Lazzari, Vincent

    2017-06-01

    Although conveying an indisputable morphological and behavioral signal, traditional dietary categories such as frugivorous or folivorous tend to group a wide range of food mechanical properties together. Because food/tooth interactions are mostly mechanical, it seems relevant to investigate the dental morphology of primates based on mechanical categories. However, existing mechanical categories classify food by its properties but cannot be used as factors to classify primate dietary habits. This comes from the fact that one primate species might be adapted to a wide range of food mechanical properties. To tackle this issue, what follows is an original framework based on action-related categories. The proposal here is to classify extant primates based on the range of food mechanical properties they can process through one given action. The resulting categories can be used as factors to investigate the dental tools available to primates. Furthermore, cracking, grinding, and shearing categories assigned depending on the hardness and the toughness of food are shown to be supported by morphological data (3D relative enamel thickness) and topographic data (relief index, occlusal complexity, and Dirichlet normal energy). Inferring food mechanical properties from dental morphology is especially relevant for the study of extinct primates, which are mainly documented by dental remains. Hence, we use action-related categories to investigate the molar morphology of an extinct colobine monkey Mesopithecus pentelicus from the Miocene of Pikermi, Greece. Action-related categories show contrasting results compared with classical categories and give us new insights into the dietary adaptations of this extinct primate. Finally, we provide some possible directions for future research aiming to test action-related categories. In particular, we suggest acquiring more data on mechanically challenging fallback foods and advocate the use of other food mechanical properties such as

  10. Physical and mechanical properties of PMMA bone cement reinforced with nano-sized titania fibers.

    PubMed

    Khaled, S M Z; Charpentier, Paul A; Rizkalla, Amin S

    2011-02-01

    X-ray contrast medium (BaSO(4) or ZrO(2)) used in commercially available PMMA bone cements imparts a detrimental effect on mechanical properties, particularly on flexural strength and fracture toughness. These lower properties facilitate the chance of implant loosening resulting from cement mantle failure. The present study was performed to examine the mechanical properties of a commercially available cement (CMW1) by introducing novel nanostructured titania fibers (n-TiO(2) fibers) into the cement matrix, with the fibers acting as a reinforcing phase. The hydrophilic nature of the n-TiO(2) fibers was modified by using a bifunctional monomer, methacrylic acid. The n-TiO(2) fiber content of the cement was varied from 0 to 2 wt%. Along with the mechanical properties (fracture toughness (K (IC)), flexural strength (FS), and flexural modulus (FM)) of the reinforced cements the following properties were investigated: complex viscosity-versus-time, maximum polymerization temperature (T (max)), dough time (t (dough)), setting time (t (set)), radiopacity, and in vitro biocompatibility. On the basis of the determined mechanical properties, the optimized composition was found at 1 wt% n-TiO(2) fibers, which provided a significant increase in K (IC) (63%), FS (20%), and FM (22%), while retaining the handling properties and in vitro biocompatibility compared to that exhibited by the control cement (CMW1). Moreover, compared to the control cement, there was no significant change in the radiopacity of any of the reinforced cements at p = 0.05. This study demonstrated a novel pathway to augment the mechanical properties of PMMA-based cement by providing an enhanced interfacial interaction and strong adhesion between the functionalized n-TiO( 2) fibers and PMMA matrix, which enhanced the effective load transfer within the cement.

  11. Barrier and Mechanical Properties of Starch-Clay Nanocomposite Films

    USDA-ARS?s Scientific Manuscript database

    The poor barrier and mechanical properties of biopolymer-based food packaging can potentially be enhanced by the use of layered silicates (nanoclay) to produce nanocomposites. In this study, starch-clay nano-composites were synthesized by a melt extrusion method. Natural (MMT) and organically modifi...

  12. Enhanced mechanical properties of self-polymerized polydopamine-coated recycled PLA filament used in 3D printing

    NASA Astrophysics Data System (ADS)

    Zhao, Xing Guan; Hwang, Kyung-Jun; Lee, Dongoh; Kim, Taemin; Kim, Namsu

    2018-05-01

    Dopamine readily adsorbs onto almost all kinds of surfaces and develops cohesive strength through self-polymerization; hence, aqueous solutions of dopamine can be used as adhesives. These properties were used to prevent the degradation in the mechanical properties of recycled PLA fabricated by 3D printer. The mechanical properties of 3D printed PLA play a critical role in determining its applications. To reduce the manufacturing cost as well as environmental pollutants, recycling of 3D printed materials has attracted many attentions. However, recycling of polymeric materials causes the degradation of the mechanical properties. Our study is aimed at advancing the current knowledge on the adhesion behavior of polydopamine coatings on PLA pellets used in 3D printing process. Polydopamine was synthesized by oxidative polymerization and used to coat PLA specimens. The adhesion behavior and mechanical properties of the 3D printed specimens were evaluated by tensile tests. It was found that the mechanical properties of recycled specimen with polydopamine coating have been improved. Microstructural and chemical characterization of the coated specimens was carried out using FE-SEM, FTIR, and XPS analyses.

  13. Dynamic-mechanical and thermomechanical properties of cellulose nanofiber/polyester resin composites.

    PubMed

    Lavoratti, Alessandra; Scienza, Lisete Cristine; Zattera, Ademir José

    2016-01-20

    Composites of unsaturated polyester resin (UPR) and cellulose nanofibers (CNFs) obtained from dry cellulose waste of softwood (Pinus sp.) and hardwood (Eucalyptus sp.) were developed. The fiber properties and the influence of the CNFs in the dynamic-mechanical and thermomechanical properties of the composites were evaluated. CNFs with a diameter of 70-90 nm were obtained. Eucalyptus sp. has higher α-cellulose content than Pinus sp. fibers. The crystallinity of the cellulose pulps decreased after grinding. However, high values were still obtained. The chemical composition of the fibers was not significantly altered by the grinding process. Eucalyptus sp. CNF composites had water absorption close to the neat resin at 1 wt% filler. The dynamic-mechanical properties of Eucalyptus sp. CNFs were slightly increased and the thermal stability was improved. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Mechanical properties of lunar regolith and lunar soil simulant

    NASA Technical Reports Server (NTRS)

    Perkins, Steven W.

    1989-01-01

    Through the Surveyor 3 and 7, and Apollo 11-17 missions a knowledge of the mechanical properties of Lunar regolith were gained. These properties, including material cohesion, friction, in-situ density, grain-size distribution and shape, and porosity, were determined by indirect means of trenching, penetration, and vane shear testing. Several of these properties were shown to be significantly different from those of terrestrial soils, such as an interlocking cohesion and tensile strength formed in the absence of moisture and particle cementation. To characterize the strength and deformation properties of Lunar regolith experiments have been conducted on a lunar soil simulant at various initial densities, fabric arrangements, and composition. These experiments included conventional triaxial compression and extension, direct tension, and combined tension-shear. Experiments have been conducted at low levels of effective confining stress. External conditions such as membrane induced confining stresses, end platten friction and material self weight have been shown to have a dramatic effect on the strength properties at low levels of confining stress. The solution has been to treat these external conditions and the specimen as a full-fledged boundary value problem rather than the idealized elemental cube of mechanics. Centrifuge modeling allows for the study of Lunar soil-structure interaction problems. In recent years centrifuge modeling has become an important tool for modeling processes that are dominated by gravity and for verifying analysis procedures and studying deformation and failure modes. Centrifuge modeling is well established for terrestrial enginering and applies equally as well to Lunar engineering. A brief review of the experiments is presented in graphic and outline form.

  15. Investigation on mechanical properties of basalt composite fabrics (experiment study)

    NASA Astrophysics Data System (ADS)

    Talebi Mazraehshahi, H.; Zamani, H.

    2010-06-01

    To fully appreciate the role and application of composite materials to structures, correct understanding of mechanical behaviors required for selection of optimum material. Fabric reinforced composites are composed of a matrix that is reinforced with pliable fabric, glass fabric is most popular reinforcement for different application specially in aircraft structure, although other fabric material are also used. At this study new fabric material called basalt with epoxy resin introduced and mechanical behaviors of this material investigated from view point of testing. For this study two type of fabric with different thickness used. Comparison between this composite reinforcement with popular reinforcement as carbon, glass, kevlar performed. To determine mechanical properties of epoxy based basalt fabric following test procedure performed : 1). Tensile testing according to ASTM D3039 in 0° and 90° direction to find ultimate strength in tension and shear, modulus of elasticity, elangation and ultimate strain. 2). Compression testing according to EN 2850 ultimate compression strength and maximum deformation under compression loading. 3). Shear testing according to ASTM D3518-94 to find in plane shear response of polymer matrix composites materials. 4). Predict flexural properties of sandwich construction which manufactured from basalt facing with PVC foam core according to ASTM C393-94. Material strength properties must be based on enough tests of material to meet the test procedure specifications [1]. For this reason six specimens were manufactured for testing and the tests were performed on them using an INSTRON machine model 5582. In the study, the effect of percent of resin in basalt reinforced composite was investigated. Also the weights of the ballast based composites with different percent of resin were measured with conventional composites. As the weight is an important parameter in aerospace industry when the designer wants to replace one material with

  16. Cation solvation with quantum chemical effects modeled by a size-consistent multi-partitioning quantum mechanics/molecular mechanics method.

    PubMed

    Watanabe, Hiroshi C; Kubillus, Maximilian; Kubař, Tomáš; Stach, Robert; Mizaikoff, Boris; Ishikita, Hiroshi

    2017-07-21

    In the condensed phase, quantum chemical properties such as many-body effects and intermolecular charge fluctuations are critical determinants of the solvation structure and dynamics. Thus, a quantum mechanical (QM) molecular description is required for both solute and solvent to incorporate these properties. However, it is challenging to conduct molecular dynamics (MD) simulations for condensed systems of sufficient scale when adapting QM potentials. To overcome this problem, we recently developed the size-consistent multi-partitioning (SCMP) quantum mechanics/molecular mechanics (QM/MM) method and realized stable and accurate MD simulations, using the QM potential to a benchmark system. In the present study, as the first application of the SCMP method, we have investigated the structures and dynamics of Na + , K + , and Ca 2+ solutions based on nanosecond-scale sampling, a sampling 100-times longer than that of conventional QM-based samplings. Furthermore, we have evaluated two dynamic properties, the diffusion coefficient and difference spectra, with high statistical certainty. Furthermore the calculation of these properties has not previously been possible within the conventional QM/MM framework. Based on our analysis, we have quantitatively evaluated the quantum chemical solvation effects, which show distinct differences between the cations.

  17. Mechanical properties of Municipal Solid Waste by SDMT

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Castelli, Francesco, E-mail: francesco.castelli@unikore.it; Maugeri, Michele

    2014-02-15

    Highlights: • The adoption of the SDMT for the measurements of MSW properties is proposed. • A comparison between SDMT results and laboratory tests was carried out. • A good reliability has been found in deriving waste properties by SDMT. • Results seems to be promising for the friction angle and Young’s modulus evaluation. - Abstract: In the paper the results of a geotechnical investigation carried on Municipal Solid Waste (MSW) materials retrieved from the “Cozzo Vuturo” landfill in the Enna area (Sicily, Italy) are reported and analyzed. Mechanical properties were determined both by in situ and laboratory large-scale onemore » dimensional compression tests. While among in situ tests, Dilatomer Marchetti Tests (DMT) is used widely in measuring soil properties, the adoption of the DMT for the measurements of MSW properties has not often been documented in literature. To validate its applicability for the estimation of MSW properties, a comparison between the seismic dilatometer (SDMT) results and the waste properties evaluated by laboratory tests was carried out. Parameters for “fresh” and “degraded waste” have been evaluated. These preliminary results seems to be promising as concerns the assessment of the friction angle of waste and the evaluation of the S-wave in terms of shear wave velocity. Further studies are certainly required to obtain more representative values of the elastic parameters according to the SDMT measurements.« less

  18. Influence of heat treatment on structural, mechanical and wear properties of crosslinked UHMWPE.

    PubMed

    Chiesa, R; Moscatelli, M; Giordano, C; Siccardi, F; Cigada, A

    2004-01-01

    New crosslinked ultra high molecular weight polyethylenes (UHMWPEs) have recently been developed, characterized and introduced in clinical applications. UHMWPE cross-linking treatments are very promising for reducing osteolysis induced by wear debris. The irradiation type, gamma or beta, the dosage and the thermal treatment performed during or following the irradiation process are all factors affecting polyethylene wear resistance. Thermal stabilization treatments performed after or during the irradiation process at a temperature above melting point (i.e. >130 degrees C) have been proven to effectively remove the free radicals generated during irradiation from UHMWPE, but their effect on the mechanical properties of UHMWPE are not completely clear. In addition to wear rate reduction, maintaining good mechanical properties is fundamental aspect in designing the new generation of crosslinked UHMWPE for artificial load bearing materials, especially considering the application in total knee replacements. In this study, we investigated the influence of different stabilization treatments, performed after gamma irradiation, on structural, wear and mechanical properties of UHMWPE. We performed four different stabilization treatments, with different temperatures and cooling rates, on 100 kGy gamma irradiated UHMWPE. Structural properties of UHMWPE were assessed by differential scanning calorimetry (DSC). To assess the mechanical performance of the materials, uni-axial tensile tests were performed according to the ASTM D638 standard, bi-axial tension performance was evaluated by small punch tests (ASTM F2183-02), toughness resistance was evaluated by the Izod method (ASTM F648), and cold flow resistance was analysed by a dynamic compressive test. Evaluation of wear resistance was by a multidirectional pin-on-disk screening machine. Materials considered were in "aged" and "non-aged" conditions. Results confirmed that cross-linking greatly enhances UHMWPE wear resistance, but

  19. Dynamic mechanical analysis of compatibilizer effect on the mechanical properties of wood flour/high-density polyethylene composites

    Treesearch

    Mehdi Behzad; Medhi Tajvidi; Ghanbar Ehrahimi; Robert H. Falk

    2004-01-01

    In this study, effect of MAPE (maleic anhydride polyethylene) as the compatibilizer on the mechanical properties of wood-flour polyethylene composites has been investigated by using Dynamic Mechanical Analysis (DMA). Composites were made at 25% and 50% by weight fiber contents and 1% and 2% compatibilizer respectively. Controls were also made at the same fiber contents...

  20. Proton dissociation properties of arylphosphonates: Determination of accurate Hammett equation parameters.

    PubMed

    Dargó, Gergő; Bölcskei, Adrienn; Grün, Alajos; Béni, Szabolcs; Szántó, Zoltán; Lopata, Antal; Keglevich, György; Balogh, György T

    2017-09-05

    Determination of the proton dissociation constants of several arylphosphonic acid derivatives was carried out to investigate the accuracy of the Hammett equations available for this family of compounds. For the measurement of the pK a values modern, accurate methods, such as the differential potentiometric titration and NMR-pH titration were used. We found our results significantly different from the pK a values reported before (pK a1 : MAE = 0.16 pK a2 : MAE=0.59). Based on our recently measured pK a values, refined Hammett equations were determined that might be used for predicting highly accurate ionization constants of newly synthesized compounds (pK a1 =1.70-0.894σ, pK a2 =6.92-0.934σ). Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Particle morphology influence on mechanical and biocompatibility properties of injection molded Ti alloy powder.

    PubMed

    Gülsoy, H Özkan; Gülsoy, Nagihan; Calışıcı, Rahmi

    2014-01-01

    Titanium and Titanium alloys exhibits properties that are excellent for various bio-applications. Metal injection molding is a processing route that offers reduction in costs, with the added advantage of near net-shape components. Different physical properties of Titanium alloy powders, shaped and processed via injection molding can achieve high complexity of part geometry with mechanical and bioactivity properties, similar or superior to wrought material. This study describes that the effect of particle morphology on the microstructural, mechanical and biocompatibility properties of injection molded Ti-6Al-4V (Ti64) alloy powder for biomaterials applications. Ti64 powders irregular and spherical in shape were injection molded with wax based binder. Binder debinding was performed in solvent and thermal method. After debinding the samples were sintered under high vacuum. Metallographic studies were determined to densification and the corresponding microstructural changes. Sintered samples were immersed in a simulated body fluid (SBF) with elemental concentrations that were comparable to those of human blood plasma for a total period of 15 days. Both materials were implanted in fibroblast culture for biocompatibility evaluations were carried out. The results show that spherical and irregular powder could be sintered to a maximum theoretical density. Maximum tensile strength was obtained for spherical shape powder sintered. The tensile strength of the irregular shape powder sintered at the same temperature was lower due to higher porosity. Finally, mechanical tests show that the irregular shape powder has lower mechanical properties than spherical shape powder. The sintered irregular Ti64 powder exhibited better biocompatibility than sintered spherical Ti64 powder. Results of study showed that sintered spherical and irregular Ti64 powders exhibited high mechanical properties and good biocompatibility properties.

  2. Influence of the grade on the variability of the mechanical properties of polypropylene waste.

    PubMed

    Jmal, Hamdi; Bahlouli, Nadia; Wagner-Kocher, Christiane; Leray, Dimitri; Ruch, Frédéric; Munsch, Jean-Nicolas; Nardin, Michel

    2018-05-01

    The prior properties of recycled polypropylene depend on the origin of waste deposits and its chemical constituents. To obtain specific properties with a predefine melt flow index of polypropylene, the suppliers of polymer introduce additives and fillers. However, the addition of additives and/or fillers can modify strongly the mechanical behaviour of recycled polypropylene. To understand the impact of the additives and fillers on the quasi-static mechanical behaviour, we consider, in this study, three different recycled polypropylenes with three different melt flow index obtained from different waste deposits. The chemical constituents of the additives and filler contents of the recycled polypropylenes are determined through thermo-physico-chemical analysis. Tensile and bending tests performed at different strain rates allow identifying the mechanical properties such as the elastic modulus, the yield stress, the maximum stress, and the failure mechanisms. The results obtained are compared with non-recycled polypropylene and with few researches to explain the combined effect of additives. Finally, a post-mortem analysis of the samples was carried out to make the link between the obtained mechanical properties and microstructure. Copyright © 2018 Elsevier Ltd. All rights reserved.

  3. The Effect of Adhesion Interaction on the Mechanical Properties of Thermoplastic Basalt Plastics

    NASA Astrophysics Data System (ADS)

    Bashtannik, P. I.; Kabak, A. I.; Yakovchuk, Yu. Yu.

    2003-01-01

    The effect of temperature, adhesion time, and surface treatment of a reinforcing filler on the mechanical properties of thermoplastic basalt plastics based on a high-density polyethylene and a copolymer of 1,3,5-trioxane with 1,3-dioxolan is investigated. An extreme dependence for the adhesive strength in a thermoplastic-basalt fiber system is established and its effect on the mechanical properties of basalt plastics and the influence of the adhesion contact time on the adhesive strength in the system are clarified. The surface modification of basalt fibers in acidic and alkaline media intensifies the adhesion of thermoplastics to them owing to a more developed surface of the reinforcing fibers after etching. It is found that the treatment in the acidic medium is more efficient and considerably improves the mechanical properties of basalt plastics.

  4. Effect of electron beam irradiation on thermal and mechanical properties of epoxy polymer

    NASA Astrophysics Data System (ADS)

    Nguyen, A. T.; Visakh, P. M.; Nazarenko, O. B.; Chandran, C. S.; Melnikova, T. V.

    2017-01-01

    This study investigates the thermal and mechanical properties of epoxy polymer after exposure to different doses of electron beam irradiation. The epoxy polymer was prepared using epoxy-diane resin ED-20 cured by polyethylenepolyamine. The irradiation of the samples was carried out with doses of 30, 100 and 300 kGy. The effects of doses on thermal and mechanical properties of the epoxy polymer were investigated by the methods of thermal gravimetric analysis, tensile test, and dynamic mechanical analysis. The thermal properties of the epoxy polymer slightly increased after irradiation at the heating in air. The tensile strength and Young’s modulus of the epoxy polymer increased by the action of electron beam up to dose of 100 kGy and then decreased. The elongation at break decreased with increasing the irradiation dose.

  5. Mechanical properties of neutron-irradiated model and commercial FeCrAl alloys

    NASA Astrophysics Data System (ADS)

    Field, Kevin G.; Briggs, Samuel A.; Sridharan, Kumar; Howard, Richard H.; Yamamoto, Yukinori

    2017-06-01

    The development and understanding of the mechanical properties of neutron-irradiated FeCrAl alloys is increasingly a critical need as these alloys continue to become more mature for nuclear reactor applications. This study focuses on the mechanical properties of model FeCrAl alloys and of a commercial FeCrAl alloy neutron-irradiated to up to 13.8 displacements per atom (dpa) at irradiation temperatures between 320 and 382 °C. Tensile tests were completed at room temperature and at 320 °C, and a subset of fractured tensile specimens was examined by scanning electron microscopy. Results showed typical radiation hardening and embrittlement indicative of high chromium ferritic alloys with strong chromium composition dependencies at lower doses. At and above 7.0 dpa, the mechanical properties saturated for both the commercial and model FeCrAl alloys, although brittle cleavage fracture was observed at the highest dose in the model FeCrAl alloy with the highest chromium content (18 wt %). The results suggest the composition and microstructure of FeCrAl alloys plays a critical role in the mechanical response of FeCrAl alloys irradiated near temperatures relevant to light water reactors.

  6. Flake Orientation Effects On Physical and Mechanical Properties of Sweetgum Flakeboard

    Treesearch

    T.F. Shupe; Chung-Yun Hse; E.W. Price

    2001-01-01

    Research was initiated to determine the effect of flake orientation on the physical and mechanical properties offlakeboard. The panel fabrication techniques investigated were single-layer panels with random and oriented flake distribution, three-layer, five-layer, and seven-layer panels. Single-layer oriented panels had panel directional property ratios of 11.8 and 12....

  7. Accurate Determination of the Quasiparticle and Scaling Properties Surrounding the Quantum Critical Point of Disordered Three-Dimensional Dirac Semimetals.

    PubMed

    Fu, Bo; Zhu, Wei; Shi, Qinwei; Li, Qunxiang; Yang, Jinlong; Zhang, Zhenyu

    2017-04-07

    Exploiting the enabling power of the Lanczos method in momentum space, we determine accurately the quasiparticle and scaling properties of disordered three-dimensional Dirac semimetals surrounding the quantum critical point separating the semimetal and diffusive metal regimes. We unveil that the imaginary part of the quasiparticle self-energy obeys a common power law before, at, and after the quantum phase transition, but the power law is nonuniversal, whose exponent is dependent on the disorder strength. More intriguingly, whereas a common power law is also found for the real part of the self-energy before and after the phase transition, a distinctly different behavior is identified at the critical point, characterized by the existence of a nonanalytic logarithmic singularity. This nonanalytical correction serves as the very basis for the unusual power-law behaviors of the quasiparticles and many other physical properties surrounding the quantum critical point. Our approach also allows the ready and reliable determination of the scaling properties of the correlation length and dynamical exponents. We further show that the central findings are valid for both uncorrelated and correlated disorder distributions and should be directly comparable with future experimental observations.

  8. Accurate Determination of the Quasiparticle and Scaling Properties Surrounding the Quantum Critical Point of Disordered Three-dimensional Dirac Semimetals

    DOE PAGES

    Fu, Bo; Zhu, Wei; Shi, Qinwei; ...

    2017-04-03

    Exploiting the enabling power of the Lanczos method in momentum space, we determine accurately the quasiparticle and scaling properties of disordered three-dimensional Dirac semimetals surrounding the quantum critical point separating the semimetal and diffusive metal regimes. We unveil that the imaginary part of the quasiparticle self-energy obeys a common power law before, at, and after the quantum phase transition, but the power law is nonuniversal, whose exponent is dependent on the disorder strength. More intriguingly, whereas a common power law is also found for the real part of the self-energy before and after the phase transition, a distinctly different behaviormore » is identified at the critical point, characterized by the existence of a nonanalytic logarithmic singularity. This nonanalytical correction serves as the very basis for the unusual power-law behaviors of the quasiparticles and many other physical properties surrounding the quantum critical point. Our approach also allows the ready and reliable determination of the scaling properties of the correlation length and dynamical exponents. Furthermore, we show that the central findings are valid for both uncorrelated and correlated disorder distributions and should be directly comparable with future experimental observations.« less

  9. Defective boron nitride nanotubes: mechanical properties, electronic structures and failure behaviors

    NASA Astrophysics Data System (ADS)

    Wang, Huan; Ding, Ning; Zhao, Xian; Wu, Chi-Man Lawrence

    2018-03-01

    Due to their excellent physical and chemical characteristics, boron nitride nanotubes (BNNTs) are regarded as a complementary addition to carbon nanotubes. Pioneer studies have demonstrated that defects in carbon nanotubes are considered tools for tuning the physical properties of these materials. In the present work, investigation on the mechanical and electronic properties of pristine and defective BNNTs was performed using the density functional theory method. The analysis on the intrinsic strength, stiffness, and failure critical strain of different types of BNNTs was conducted systematically. The computing results showed that the intrinsic strength of BNNTs decreased linearly with the increased Stone-Wales (SW) defect density around the axis. The SW defect density along the axis played a minor role on the changing of mechanical properties of BNNTs. The BNNT with a B vacancy expressed higher intrinsic strength than that of the N vacancy model. The final failure of the pristine BNNTs was due to the fracture of the Type1 bonds under the mechanical strain. Defects like SW or vacancy are served as the initial break site of BNNTs. Applying strain or creating defects are both effective methods for reducing the band gap of BNNTs.

  10. First-principles investigation of mechanical and electronic properties of tetragonal NbAl3 under tension

    NASA Astrophysics Data System (ADS)

    Jiao, Zhen; Liu, Qi-Jun; Liu, Fu-Sheng; Tang, Bin

    2018-06-01

    Using the density functional theory calculations, the mechanical and electronic properties of NbAl3 under different tensile loads were investigated. The calculated lattice parameters, elastic constants and mechanical properties (bulk modulus, shear modulus, Young's modulus, Poisson's ratio, Pugh's criterion and Cauchy's pressure) indicated that our results were in agreement with the published experimental and theoretical data at zero tension. With respect to NbAl3 under tension in this paper, the crystal structure was changed from tetragonal to orthorhombic under tension along the [100] and [101] directions. The NbAl3 crystal has been classified as brittle material under tension from 0 to 20 GPa. The obtained Young's modulus and Debye temperature monotonically decreased with increasing tension stress. Combining with mechanical and electronic properties in detail, the decreased mechanical properties were mainly due to the weakening of covalency.

  11. (Invited) Effect of Aging on Mechanical Properties of Lithium Ion Cell Components

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wu, Zenan; Cao, Lei; Hartig, Julia

    The mechanical properties of aged and fresh lithium ion cell components are evaluated in this paper. Cells components were obtained from destructive physical analysis of 40Ah NMC/Graphite-based pouch cells before and after cycling and were subjected to mechanical testing. The aging tests comprised of cycling the cell across a voltage window of 4.1V to 3.0V at room temperature (25?). Using a 2C charging rate and 1C discharging rate, the cells were subjected to over 5600 cycles before a 80% drop in the name-plate capacity was observed. Mechanical tests, including compression test, tensile test and indentation test, were conducted on themore » cell components to investigate differences in the mechanical performance. Comparison of the fresh and aged cells components shows that cycling the cells has different degrees of impact on the different cell components. Anodes suffered the most serious deterioration in mechanical properties while separators remained intact under the test condition investigated.« less

  12. Electro-mechanical properties of hydrogel composites with micro- and nano-cellulose fillers

    NASA Astrophysics Data System (ADS)

    N, Mohamed Shahid U.; Deshpande, Abhijit P.; Lakshmana Rao, C.

    2015-09-01

    Stimuli responsive cross-linked hydrogels are of great interest for applications in diverse fields such as sensors and biomaterials. In this study, we investigate polymer composites filled with cellulose fillers. The celluloses used in making the composites were a microcrystalline cellulose of commercial grade and cellulose nano-whiskers obtained through acid hydrolysis of microcrystalline cellulose. The filler concentration was varied and corresponding physical, mechanical and electro-mechanical characterization was carried out. The electro-mechanical properties were determined using a quasi-static method. The fillers not only enhance the mechanical properties of the composite by providing better reinforcement but also provide a quantitative electric potential in the composite. The measurements reveal that the polymer composites prepared from two different cellulose fillers possess a quantitative electric potential which can be utilized in biomedical applications. It is argued that the mechanism behind the quantitative electric potential in the composites is due to streaming potentials arising due to electrical double layer formation.

  13. Hydrolytically degradable poly(ethylene glycol) hydrogel scaffolds with tunable degradation and mechanical properties

    PubMed Central

    Zustiak, Silviya P.

    2011-01-01

    The objective of this work was to create three-dimensional (3D) hydrogel matrices with defined mechanical properties, as well as tunable degradability for use in applications involving protein delivery and cell encapsulation. Thus, we report the synthesis and characterization of a novel hydrolytically degradable poly(ethylene glycol) (PEG) hydrogel composed of PEG vinyl sulfone (PEG-VS) cross-linked with PEG-diester-dithiol. Unlike previously reported degradable PEG-based hydrogels, these materials are homogeneous in structure, fully hydrophilic and have highly specific cross-linking chemistry. We characterized hydrogel degradation and associated trends in mechanical properties, i.e., storage modulus (G′), swelling ratio (QM), and mesh size (ξ). Degradation time and the monitored mechanical properties of the hydrogel correlated with cross-linker molecular weight, cross-linker functionality, and total polymer density; these properties changed predictably as degradation proceeded (G′ decreased, whereas QM and ξ increased) until the gels reached complete degradation. Balb/3T3 fibroblast adhesion and proliferation within the 3D hydrogel matrices were also verified. In sum, these unique properties indicate that the reported degradable PEG hydrogels are well poised for specific applications in protein and cell delivery to repair soft tissue. PMID:20355705

  14. Sensing, Measuring and Modelling the Mechanical Properties of Sandstone

    NASA Astrophysics Data System (ADS)

    Antony, S. J.; Olugbenga, A.; Ozerkan, N. G.

    2018-02-01

    We present a hybrid framework for simulating the strength and dilation characteristics of sandstone. Where possible, the grain-scale properties of sandstone are evaluated experimentally in detail. Also, using photo-stress analysis, we sense the deviator stress (/strain) distribution at the micro-scale and its components along the orthogonal directions on the surface of a V-notch sandstone sample under mechanical loading. Based on this measurement and applying a grain-scale model, the optical anisotropy index K 0 is inferred at the grain scale. This correlated well with the grain contact stiffness ratio K evaluated using ultrasound sensors independently. Thereafter, in addition to other experimentally characterised structural and grain-scale properties of sandstone, K is fed as an input into the discrete element modelling of fracture strength and dilation of the sandstone samples. Physical bulk-scale experiments are also conducted to evaluate the load-displacement relation, dilation and bulk fracture strength characteristics of sandstone samples under compression and shear. A good level of agreement is obtained between the results of the simulations and experiments. The current generic framework could be applied to understand the internal and bulk mechanical properties of such complex opaque and heterogeneous materials more realistically in future.

  15. Biodegradable Zein-Based Blend Films: Structural, Mechanical and Barrier Properties

    PubMed Central

    Filho, José Francisco Lopes

    2015-01-01

    Summary The effect of adding a hydrocolloid on the structural, mechanical and barrier properties of zein-based blend films is evaluated. Zein-oleic acid blend film with added xanthan gum (Z-OA-XG) showed higher water solubility (13.09%) and opacity (8.49 AU/mm) than zein-oleic acid (Z-OA) film (10.80% and 5.19 AU/mm, respectively). Furthermore, Z-OA film had greater flexibility with lower Young’s Modulus (YM=5.02 MPa) and higher elongation at break (η=10.62%); nonetheless, it was less resistant to tension (tensile strength σ=8.5 MPa) than Z-OA-XG film, which showed YM, η and σ of 6.38 MPa, 6.66% and 10.485 MPa, respectively. Both films had glossy and homogeneous structure with comparable water vapour and oxygen barrier properties around 4.39·10–11 and 1.82·10–13 g/(Pa·s·m), respectively. Based on that, xanthan gum structure influenced mainly mechanical and light barrier properties of zein-oleic acid blend films. PMID:27904368

  16. Semicrystalline Ionomer-Metal Carboxylate Composite: Phase Behavior and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Wakabayashi, Katsuyuki

    2005-03-01

    We have shown previously that the thermal and mechanical behavior of ethylene-methacrylic acid (E-MAA) ionomers can be tuned by the addition of certain magnesium carboxylates, such as magnesium stearate (MgSt). The property modifications result from coassembly of the two components, both co-aggregation of the ionic groups and co-crystallization of the methylene sequences, as revealed by X-ray scattering. When MgSt is replaced by sodium stearate (NaSt), a different suite of mechanical properties is obtained. NaSt, with its high melting and clearing (288 ^oC) points, readily crystallizes out of solution in the molten polymer and forms an effective composite upon cooling from a single-phase melt. The NaSt crystals in the composite resemble the rectangular polymorph in pure NaSt, though with some differences in lattice parameters and transition temperatures due to interaction with the acid groups of the copolymer. The different physical properties of the NaSt vs. MgSt modified ionomers are traced to these microstructural differences, elucidated through a combination of X-ray scattering and microscopy.

  17. Study on Mechanical Properties of Hybrid Fiber Reinforced Concrete

    NASA Astrophysics Data System (ADS)

    He, Dongqing; Wu, Min; Jie, Pengyu

    2017-12-01

    Several common high elastic modulus fibers (steel fibers, basalt fibers, polyvinyl alcohol fibers) and low elastic modulus fibers (polypropylene fiber) are incorporated into the concrete, and its cube compressive strength, splitting tensile strength and flexural strength are studied. The test result and analysis demonstrate that single fiber and hybrid fiber will improve the integrity of the concrete at failure. The mechanical properties of hybrid steel fiber-polypropylene fiber reinforced concrete are excellent, and the cube compressive strength, splitting tensile strength and flexural strength respectively increase than plain concrete by 6.4%, 3.7%, 11.4%. Doped single basalt fiber or polypropylene fiber and basalt fibers hybrid has little effect on the mechanical properties of concrete. Polyvinyl alcohol fiber and polypropylene fiber hybrid exhibit ‘negative confounding effect’ on concrete, its splitting tensile and flexural strength respectively are reduced by 17.8% and 12.9% than the single-doped polyvinyl alcohol fiber concrete.

  18. Enabling real-time ultrasound imaging of soft tissue mechanical properties by simplification of the shear wave motion equation.

    PubMed

    Engel, Aaron J; Bashford, Gregory R

    2015-08-01

    Ultrasound based shear wave elastography (SWE) is a technique used for non-invasive characterization and imaging of soft tissue mechanical properties. Robust estimation of shear wave propagation speed is essential for imaging of soft tissue mechanical properties. In this study we propose to estimate shear wave speed by inversion of the first-order wave equation following directional filtering. This approach relies on estimation of first-order derivatives which allows for accurate estimations using smaller smoothing filters than when estimating second-order derivatives. The performance was compared to three current methods used to estimate shear wave propagation speed: direct inversion of the wave equation (DIWE), time-to-peak (TTP) and cross-correlation (CC). The shear wave speed of three homogeneous phantoms of different elastic moduli (gelatin by weight of 5%, 7%, and 9%) were measured with each method. The proposed method was shown to produce shear speed estimates comparable to the conventional methods (standard deviation of measurements being 0.13 m/s, 0.05 m/s, and 0.12 m/s), but with simpler processing and usually less time (by a factor of 1, 13, and 20 for DIWE, CC, and TTP respectively). The proposed method was able to produce a 2-D speed estimate from a single direction of wave propagation in about four seconds using an off-the-shelf PC, showing the feasibility of performing real-time or near real-time elasticity imaging with dedicated hardware.

  19. Indentation damage and mechanical properties of human enamel and dentin.

    PubMed

    Xu, H H; Smith, D T; Jahanmir, S; Romberg, E; Kelly, J R; Thompson, V P; Rekow, E D

    1998-03-01

    Understanding the mechanical properties of human teeth is important to clinical tooth preparation and to the development of "tooth-like" restorative materials. Previous studies have focused on the macroscopic fracture behavior of enamel and dentin. In the present study, we performed indentation studies to understand the microfracture and deformation and the microcrack-microstructure interactions of teeth. It was hypothesized that crack propagation would be influenced by enamel rods and the dentino-enamel junction (DEJ), and the mechanical properties would be influenced by enamel rod orientation and tooth-to-tooth variation. Twenty-eight human third molars were used for the measurement of hardness, fracture toughness, elastic modulus, and energy absorbed during indentation. We examined the effect of enamel rod orientation by propagating cracks in the occlusal surface, and in the axial section in directions parallel and perpendicular to the occlusal surface. The results showed that the cracks in the enamel axial section were significantly longer in the direction perpendicular to the occlusal surface than parallel. The cracks propagating toward the DEJ were always arrested and unable to penetrate dentin. The fracture toughness of enamel was not single-valued but varied by a factor of three as a function of enamel rod orientation. The elastic modulus of enamel showed a significant difference between the occlusal surface and the axial section. It is concluded that the cracks strongly interact with the DEJ and the enamel rods, and that the mechanical properties of teeth are functions of microstructural orientations; hence, single values of properties (e.g., a single toughness value or a single modulus value) should not be used without information on microstructural orientation.

  20. Mechanical properties of silk: interplay of deformation on macroscopic and molecular length scales.

    PubMed

    Krasnov, Igor; Diddens, Imke; Hauptmann, Nadine; Helms, Gesa; Ogurreck, Malte; Seydel, Tilo; Funari, Sérgio S; Müller, Martin

    2008-02-01

    Using an in situ combination of tensile tests and x-ray diffraction, we have determined the mechanical properties of both the crystalline and the disordered phase of the biological nanocomposite silk by adapting a model from linear viscoelastic theory to the semicrystalline morphology of silk. We observe a strong interplay between morphology and mechanical properties. Silk's high extensibility results principally from the disordered phase; however, the crystals are also elastically deformed.

  1. Bioinspired Cellular Structures: Additive Manufacturing and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Stampfl, J.; Pettermann, H. E.; Liska, R.

    Biological materials (e.g., wood, trabecular bone, marine skeletons) rely heavily on the use of cellular architecture, which provides several advantages. (1) The resulting structures can bear the variety of "real life" load spectra using a minimum of a given bulk material, featuring engineering lightweight design principles. (2) The inside of the structures is accessible to body fluids which deliver the required nutrients. (3) Furthermore, cellular architectures can grow organically by adding or removing individual struts or by changing the shape of the constituting elements. All these facts make the use of cellular architectures a reasonable choice for nature. Using additive manufacturing technologies (AMT), it is now possible to fabricate such structures for applications in engineering and biomedicine. In this chapter, we present methods that allow the 3D computational analysis of the mechanical properties of cellular structures with open porosity. Various different cellular architectures including disorder are studied. In order to quantify the influence of architecture, the apparent density is always kept constant. Furthermore, it is shown that how new advanced photopolymers can be used to tailor the mechanical and functional properties of the fabricated structures.

  2. Mechanical properties of porous and cellular materials

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sieradzki, K.; Green, D.J.; Gibson, L.J.

    1991-01-01

    This symposium successfully brought scientists together from a wide variety of disciplines to focus on the mechanical behavior of porous and cellular solids composed of metals, ceramics, polymers, or biological materials. For cellular materials, papers ranged from processing techniques through microstructure-mechanical property relationships to design. In an overview talk, Mike Ashby (Cambridge Univ.) showed how porous cellular materials can be more efficient than dense materials in designs that require minimum weight. He indicated that many biological materials have been able to accomplish such efficiency but there exists an opportunity to design even more efficient, manmade materials controlling microstructures at differentmore » scale levels. In the area of processing, James Aubert (Sandia National Laboratories) discussed techiques for manipulating polymersolvent phase equilibria to control the microstructure of microcellular foams. Other papers on processing discussed the production of cellular ceramics by CVD, HIPing and sol- gel techniques. Papers on the mechanical behavior of cellular materials considered various ceramics microcellular polymers, conventional polymer foams and apples. There were also contributions that considered optimum design procedures for cellular materials. Steven Cowin (City Univ. of New York) discussed procedures to match the discrete microstructural aspects of cellular materials with the continuum mechanics approach to their elastic behavior.« less

  3. Research Update: Mechanical properties of metal-organic frameworks - Influence of structure and chemical bonding

    NASA Astrophysics Data System (ADS)

    Li, Wei; Henke, Sebastian; Cheetham, Anthony K.

    2014-12-01

    Metal-organic frameworks (MOFs), a young family of functional materials, have been attracting considerable attention from the chemistry, materials science, and physics communities. In the light of their potential applications in industry and technology, the fundamental mechanical properties of MOFs, which are of critical importance for manufacturing, processing, and performance, need to be addressed and understood. It has been widely accepted that the framework topology, which describes the overall connectivity pattern of the MOF building units, is of vital importance for the mechanical properties. However, recent advances in the area of MOF mechanics reveal that chemistry plays a major role as well. From the viewpoint of materials science, a deep understanding of the influence of chemical effects on MOF mechanics is not only highly desirable for the development of novel functional materials with targeted mechanical response, but also for a better understanding of important properties such as structural flexibility and framework breathing. The present work discusses the intrinsic connection between chemical effects and the mechanical behavior of MOFs through a number of prototypical examples.

  4. Determination of orthotropic mechanical properties of 3D printed parts for structural health monitoring

    NASA Astrophysics Data System (ADS)

    Poissenot-Arrigoni, Bastien; Scheyer, Austin; Anton, Steven R.

    2017-04-01

    The evolution of additive manufacturing has allowed engineers to use 3D printing for many purposes. As a natural consequence of the 3D printing process, the printed object is anisotropic. As part of an ongoing project to embed piezoelectric devices in 3D printed structures for structural health monitoring (SHM), this study aims to find the mechanical properties of the 3D printed material and the influence of different external factors on those properties. The orthotropic mechanical properties of a 3D printed structure are dependent on the printing parameters used to create the structure. In order to develop an orthotropic material model, mechanical properties will be found experimentally from additively manufactured samples created from polylactic acid (PLA) using a consumer-level fused deposition modeling (FDM) printer; the Lulzbot TAZ 6. Nine mechanical constants including three Young's moduli, three Poisson's ratios, and three shear moduli are needed to fully describe the 3D elastic behavior of the material. Printed specimens with different raster orientations and print orientations allow calculation of the different material constants. In this work, seven of the nine mechanical constants were found. Two shear moduli were unable to be measured due to difficulties in printing two of the sample orientations. These mechanical properties are needed in order to develop orthotropic material models of systems employing 3D printed PLA. The results from this paper will be used to create a model of a piezoelectric transducer embedded in a 3D printed structure for structural health monitoring.

  5. Material properties of biofilms – key methods for understanding permeability and mechanics

    PubMed Central

    Billings, Nicole; Birjiniuk, Alona; Samad, Tahoura S.; Doyle, Patrick S.; Ribbeck, Katharina

    2015-01-01

    Microorganisms can form biofilms, which are multicellular communities surrounded by a hydrated extracellular matrix of polymers. Central properties of the biofilm are governed by this extracellular matrix, which provides mechanical stability to the three-dimensional biofilm structure, regulates the ability of the biofilm to adhere to surfaces, and determines the ability of the biofilm to adsorb gasses, solutes, and foreign cells. Despite their critical relevance for understanding and eliminating of biofilms, the materials properties of the extracellular matrix are understudied. Here, we offer the reader a guide to current technologies that can be utilized to specifically assess the permeability and mechanical properties of the biofilm matrix and its interacting components. In particular, we highlight technological advances in instrumentation and interactions between multiple disciplines that have broadened the spectrum of methods available to conduct these studies. We review pioneering work that furthers our understanding of the material properties of biofilms. PMID:25719969

  6. Thermal and mechanical treatments for nickel and some nickel-base alloys: Effects on mechanical properties

    NASA Technical Reports Server (NTRS)

    Hall, A. M.; Beuhring, V. F.

    1972-01-01

    This report deals with heat treating and working nickel and nickel-base alloys, and with the effects of these operations on the mechanical properties of the materials. The subjects covered are annealing, solution treating, stress relieving, stress equalizing, age hardening, hot working, cold working, combinations of working and heat treating (often referred to as thermomechanical treating), and properties of the materials at various temperatures. The equipment and procedures used in working the materials are discussed, along with the common problems that may be encountered and the precautions and corrective measures that are available.

  7. Mechanical properties of porcine brain tissue in vivo and ex vivo estimated by MR elastography.

    PubMed

    Guertler, Charlotte A; Okamoto, Ruth J; Schmidt, John L; Badachhape, Andrew A; Johnson, Curtis L; Bayly, Philip V

    2018-03-01

    The mechanical properties of brain tissue in vivo determine the response of the brain to rapid skull acceleration. These properties are thus of great interest to the developers of mathematical models of traumatic brain injury (TBI) or neurosurgical simulations. Animal models provide valuable insight that can improve TBI modeling. In this study we compare estimates of mechanical properties of the Yucatan mini-pig brain in vivo and ex vivo using magnetic resonance elastography (MRE) at multiple frequencies. MRE allows estimations of properties in soft tissue, either in vivo or ex vivo, by imaging harmonic shear wave propagation. Most direct measurements of brain mechanical properties have been performed using samples of brain tissue ex vivo. It has been observed that direct estimates of brain mechanical properties depend on the frequency and amplitude of loading, as well as the time post-mortem and condition of the sample. Using MRE in the same animals at overlapping frequencies, we observe that porcine brain tissue in vivo appears stiffer than porcine brain tissue samples ex vivo at frequencies of 100 Hz and 125 Hz, but measurements show closer agreement at lower frequencies. Copyright © 2018 Elsevier Ltd. All rights reserved.

  8. The challenges of achieving good electrical and mechanical properties when making structural supercapacitors

    NASA Astrophysics Data System (ADS)

    Ciocanel, C.; Browder, C.; Simpson, C.; Colburn, R.

    2013-04-01

    The paper presents results associated with the electro-mechanical characterization of a composite material with power storage capability, identified throughout the paper as a structural supercapacitor. The structural supercapacitor uses electrodes made of carbon fiber weave, a separator made of Celgard 3501, and a solid PEG-based polymer blend electrolyte. To be a viable structural supercapacitor, the material has to have good mechanical and power storage/electrical properties. The literature in this area is inconsistent on which electrical properties are evaluated, and how those properties are assessed. In general, measurements of capacitance or specific capacitance (i.e. capacitance per unit area or per unit volume) are made, without considering other properties such as leakage resistance and equivalent series resistance of the supercapacitor. This paper highlights the significance of these additional electrical properties, discusses the fluctuation of capacitance over time, and proposes methods to improve the stability of the material's electric properties over time.

  9. Three types of dermal grafts in rats: the importance of mechanical property and structural design.

    PubMed

    You, Chuangang; Wang, Xingang; Zheng, Yurong; Han, Chunmao

    2013-12-04

    To determine how the mechanical property and micro structure affect tissue regeneration and angiogenesis, three types of scaffolds were studied. Acellular dermal matrices (ADM), produced from human skin by removing the epidermis and cells, has been widely used in wound healing because of its high mechanical strength. Collagen scaffolds (CS) incorporated with poly(glycolide-co-L-lactide) (PLGA) mesh forms a well-supported hybrid dermal equivalent poly(glycolide-co-L-lactide) mesh/collagen scaffolds (PMCS). We designed this scaffold to enhance the CS mechanical property. These three different dermal substitutes-ADM, CS and PMCSs are different in the tensile properties and microstructure. Several basic physical characteristics of dermal substitutes were investigated in vitro. To characterize the angiogenesis and tissue regeneration, the materials were embedded subcutaneously in Sprague-Dawley (SD) rats. At weeks 1, 2, 4 and 8 post-surgery, the tissue specimens were harvested for histology, immunohistochemistry and real-time quantitative PCR (RT-qPCR). In vitro studies demonstrated ADM had a higher Young's modulus (6.94 MPa) rather than CS (0.19 MPa) and PMCS (3.33 MPa) groups in the wet state. Compared with ADMs and CSs, PMCSs with three-dimensional porous structures resembling skin and moderate mechanical properties can promote tissue ingrowth more quickly after implantation. In addition, the vascularization of the PMCS group is more obvious than that of the other two groups. The incorporation of a PLGA knitted mesh in CSs can improve the mechanical properties with little influence on the three-dimensional porous microstructure. After implantation, PMCSs can resist the contraction and promote cell infiltration, neotissue formation and blood vessel ingrowth, especially from the mesh side. Although ADM has high mechanical strength, its vascularization is poor because the pore size is too small. In conclusion, the mechanical properties of scaffolds are important for

  10. Influence of mannitol concentration on the physicochemical, mechanical and pharmaceutical properties of lyophilised mannitol.

    PubMed

    Kaialy, Waseem; Khan, Usman; Mawlud, Shadan

    2016-08-20

    Mannitol is a pharmaceutical excipient that is receiving increased popularity in solid dosage forms. The aim of this study was to provide comparative evaluation on the effect of mannitol concentration on the physicochemical, mechanical, and pharmaceutical properties of lyophilised mannitol. The results showed that the physicochemical, mechanical and pharmaceutical properties of lyophilised mannitol powders are strong functions of mannitol concentration. By decreasing mannitol concentration, the true density, bulk density, cohesivity, flowability, netcharge-to-mass ratio, and relative degree of crystallinity of LM were decreased, whereas the breakability, size distribution, and size homogeneity of lyophilised mannitol particles were increased. The mechanical properties of lyophilised mannitol tablets improved with decreasing mannitol concentration. The use of lyophilised mannitol has profoundly improved the dissolution rate of indomethacin from tablets in comparison to commercial mannitol. This improvement exhibited an increasing trend with decreasing mannitol concentration. In conclusion, mannitols lyophilised from lower concentrations are more desirable in tableting than mannitols from higher concentrations due to their better mechanical and dissolution properties. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Ligand structure and mechanical properties of single-nanoparticle-thick membranes.

    PubMed

    Salerno, K Michael; Bolintineanu, Dan S; Lane, J Matthew D; Grest, Gary S

    2015-06-01

    The high mechanical stiffness of single-nanoparticle-thick membranes is believed to result from the local structure of ligand coatings that mediate interactions between nanoparticles. These ligand structures are not directly observable experimentally. We use molecular dynamics simulations to observe variations in ligand structure and simultaneously measure variations in membrane mechanical properties. We have shown previously that ligand end group has a large impact on ligand structure and membrane mechanical properties. Here we introduce and apply quantitative molecular structure measures to these membranes and extend analysis to multiple nanoparticle core sizes and ligand lengths. Simulations of nanoparticle membranes with a nanoparticle core diameter of 4 or 6 nm, a ligand length of 11 or 17 methylenes, and either carboxyl (COOH) or methyl (CH(3)) ligand end groups are presented. In carboxyl-terminated ligand systems, structure and interactions are dominated by an end-to-end orientation of ligands. In methyl-terminated ligand systems large ordered ligand structures form, but nanoparticle interactions are dominated by disordered, partially interdigitated ligands. Core size and ligand length also affect both ligand arrangement within the membrane and the membrane's macroscopic mechanical response, but are secondary to the role of the ligand end group. Moreover, the particular end group (COOH or CH(3)) alters the nature of how ligand length, in turn, affects the membrane properties. The effect of core size does not depend on the ligand end group, with larger cores always leading to stiffer membranes. Asymmetry in the stress and ligand density is observed in membranes during preparation at a water-vapor interface, with the stress asymmetry persisting in all membranes after drying.

  12. Ligand structure and mechanical properties of single-nanoparticle thick membranes

    DOE PAGES

    Salerno, Kenneth Michael; Bolintineanu, Dan S.; Lane, J. Matthew D.; ...

    2015-06-16

    We believe that the high mechanical stiffness of single-nanoparticle-thick membranes is the result of the local structure of ligand coatings that mediate interactions between nanoparticles. These ligand structures are not directly observable experimentally. We use molecular dynamics simulations to observe variations in ligand structure and simultaneously measure variations in membrane mechanical properties. We have shown previously that ligand end group has a large impact on ligand structure and membrane mechanical properties. Here we introduce and apply quantitative molecular structure measures to these membranes and extend analysis to multiple nanoparticle core sizes and ligand lengths. Simulations of nanoparticle membranes with amore » nanoparticle core diameter of 4 or 6 nm, a ligand length of 11 or 17 methylenes, and either carboxyl (COOH) or methyl (CH 3) ligand end groups are presented. In carboxyl-terminated ligand systems, structure and interactions are dominated by an end-to-end orientation of ligands. In methyl-terminated ligand systems large ordered ligand structures form, but nanoparticle interactions are dominated by disordered, partially interdigitated ligands. Core size and ligand length also affect both ligand arrangement within the membrane and the membrane's macroscopic mechanical response, but are secondary to the role of the ligand end group. Additionally, the particular end group (COOH or CH 3) alters the nature of how ligand length, in turn, affects the membrane properties. The effect of core size does not depend on the ligand end group, with larger cores always leading to stiffer membranes. Asymmetry in the stress and ligand density is observed in membranes during preparation at a water-vapor interface, with the stress asymmetry persisting in all membranes after drying.« less

  13. POSS-Containing Bioinspired Adhesives with Enhanced Mechanical and Optical Properties for Biomedical Applications.

    PubMed

    Pramudya, Irawan; Rico, Catalina G; Lee, Choogon; Chung, Hoyong

    2016-12-12

    A new terpolymer adhesive, poly(2-methoxyethyl acrylate-co-N-methacryloyl 3,4-dihydroxyl-l-phenylalanine-co-heptaisobutyl substituted polyhedral oligomeric silsesquioxane propyl methacrylate) (poly(MEA-co-MDOPA-co-MPOSS) was synthesized by thermally initiated radical polymerization. In this study, we investigated the effect of the POSS component on adhesion, mechanical, and optical properties of the catechol-group containing bioinspired adhesives. The terpolymer contains the catechol group which is known to improve the adhesion properties of polymers. Only a very small amount of the POSS-containing monomer, MPOSS, was included, 0.5 mol %. In the presence of POSS, the synthesized poly(MEA-co-MDOPA-co-MPOSS) demonstrated strong adhesion properties, 23.2 ± 6.2 J/m 2 with 0.05 N preloading and 300 s holding time, compared to many previously prepared catechol-containing adhesives. The mechanical properties (Young's modulus and stress at 10% strain) of the POSS-containing terpolymer showed significant increases (6-fold higher) over the control polymer, which does not contain POSS. Optical transmittance of the synthesized terpolymer was also improved significantly in the visible light range, 450-750 nm. Cell testing with human embryonic kidney cells (HEK293A) indicates that the new terpolymer is a promising candidate in biomedical adhesives without acute cytotoxicity. The synthesized poly(MEA-co-MDOPA-co-MPOSS) is the first example of POSS-containing pressure sensitive bioinspired adhesive for biomedical applications. The study of poly(MEA-co-MDOPA-co-MPOSS) demonstrated a convenient method to enhance two important properties, mechanical and optical properties, by the addition of a very small amount of POSS. Based on this study, it was found that POSS can be used to strengthen mechanical properties of bioinspired adhesive without the need for a covalent cross-linking step.

  14. Structure-to-property Relationships in Addition Cured Polymers 2: Resin Tg Composite Initial Mechanical Properties of Norbornenyl Cured Polyimide Resins

    NASA Technical Reports Server (NTRS)

    Alston, W. B.

    1986-01-01

    PRM (polymerization of monomeric reactants) methodology was used to prepare thirty different polyimide oligomeric resins. Monomeric composition as well as chain length between sites of crosslinks were varied to examine their effects on glass transition temperature (Tg) of the cured/postcured resins. An almost linear correlation of Tg versus molecular distance between the crosslinks was observed. An attempt was made to correlate Tg with initial mechanical properties (flexural strength and interlaminar shear strength) of unidirectional graphite fiber composites prepared with these resins. However, the scatter in mechanical strength data prevented obtaining as clear a correlation as was observed for the structural modification/crosslink distance versus Tg. Instead, only a range of composite mechanical properties was obtained at the test temperatures studied (room temperature, 288 and 316 C). Perhaps more importantly, what did become apparent during the attempted correlation study was: (1) that PMR methodology could be used to prepare composites from resins that contain a wide variety of monomer modifications, and (2) that these composites almost invariably provided satisfactory initial mechanical properties as long as the resins selected were melt processable.

  15. Mechanical properties of DNA-like polymers

    PubMed Central

    Peters, Justin P.; Yelgaonkar, Shweta P.; Srivatsan, Seergazhi G.; Tor, Yitzhak; James Maher, L.

    2013-01-01

    The molecular structure of the DNA double helix has been known for 60 years, but we remain surprisingly ignorant of the balance of forces that determine its mechanical properties. The DNA double helix is among the stiffest of all biopolymers, but neither theory nor experiment has provided a coherent understanding of the relative roles of attractive base stacking forces and repulsive electrostatic forces creating this stiffness. To gain insight, we have created a family of double-helical DNA-like polymers where one of the four normal bases is replaced with various cationic, anionic or neutral analogs. We apply DNA ligase-catalyzed cyclization kinetics experiments to measure the bending and twisting flexibilities of these polymers under low salt conditions. Interestingly, we show that these modifications alter DNA bending stiffness by only 20%, but have much stronger (5-fold) effects on twist flexibility. We suggest that rather than modifying DNA stiffness through a mechanism easily interpretable as electrostatic, the more dominant effect of neutral and charged base modifications is their ability to drive transitions to helical conformations different from canonical B-form DNA. PMID:24013560

  16. An investigation of the microstructure, mechanical properties, and tribological performance of ultra high molecular weight polyethylene for applications in total joint arthroplasty

    NASA Astrophysics Data System (ADS)

    van Citters, Douglas W.

    Ultra high molecular weight polyethylene (UHMWPE) is the most common bearing material in joint arthroplasty due to its biocompatibility, its wear resistance, and its mechanical toughness. Despite the favorable properties of UHMWPE and its success as a biomaterial, billions of dollars are spent annually to revise tens of thousands of failed artificial joints. Over half of these revision procedures are related to mechanical failure of the polymer bearing or osteolysis resulting from polymer wear. Contemporary material processing steps involving thermal treatment and/or radiation treatment seek to improve outcomes through improving the tribological properties of UHMWPE. However, it is widely recognized that achieving wear resistance through radiation-induced crosslinking comes at the cost of reduced mechanical properties. Moreover, current wear theories for orthopaedic UHMWPE are incomplete in that they predict zero wear in the absence of crossing motion. Wear nonetheless occurs in linear reciprocation, necessitating an alternate theory. The present work explains the effects of thermal treatments and radiation treatments on the properties of GUR1050 UHMWPE. A test matrix allows comparisons of different treatments across different test platforms. Characterization techniques include DSC, FTIR spectroscopy, tensile testing, x-ray diffraction, and electron microscopy. A novel quantitative stereology technique is developed to quantify crystallite size in the semicrystalline material. Seven clinically relevant materials are subjected to rolling-sliding tribotesting to determine polyethylene wear behavior in linear reciprocation. The multi-station tribotester employed for this work enables high throughput testing, and the specimen geometry allows direct measurement of wear rates without a gravimetric soak control. The results of the material characterization tests can be used to accurately predict the rolling-sliding wear behavior of UHMWPE. Wear rate is directly related to

  17. Prediction of Mechanical Properties of Polymers With Various Force Fields

    NASA Technical Reports Server (NTRS)

    Odegard, Gregory M.; Clancy, Thomas C.; Gates, Thomas S.

    2005-01-01

    The effect of force field type on the predicted elastic properties of a polyimide is examined using a multiscale modeling technique. Molecular Dynamics simulations are used to predict the atomic structure and elastic properties of the polymer by subjecting a representative volume element of the material to bulk and shear finite deformations. The elastic properties of the polyimide are determined using three force fields: AMBER, OPLS-AA, and MM3. The predicted values of Young s modulus and shear modulus of the polyimide are compared with experimental values. The results indicate that the mechanical properties of the polyimide predicted with the OPLS-AA force field most closely matched those from experiment. The results also indicate that while the complexity of the force field does not have a significant effect on the accuracy of predicted properties, small differences in the force constants and the functional form of individual terms in the force fields determine the accuracy of the force field in predicting the elastic properties of the polyimide.

  18. Enhanced mechanical properties of epoxy nanocomposites by mixing noncovalently functionalized boron nitride nanoflakes.

    PubMed

    Lee, Dongju; Song, Sung Ho; Hwang, Jaewon; Jin, Sung Hwan; Park, Kwang Hyun; Kim, Bo Hyun; Hong, Soon Hyung; Jeon, Seokwoo

    2013-08-12

    The influence of surface modifications on the mechanical properties of epoxy-hexagonal boron nitride nanoflake (BNNF) nanocomposites is investigated. Homogeneous distributions of boron nitride nanoflakes in a polymer matrix, preserving intrinsic material properties of boron nitride nanoflakes, is the key to successful composite applications. Here, a method is suggested to obtain noncovalently functionalized BNNFs with 1-pyrenebutyric acid (PBA) molecules and to synthesize epoxy-BNNF nanocomposites with enhanced mechanical properties. The incorporation of noncovalently functionalized BNNFs into epoxy resin yields an elastic modulus of 3.34 GPa, and 71.9 MPa ultimate tensile strength at 0.3 wt%. The toughening enhancement is as high as 107% compared to the value of neat epoxy. The creep strain and the creep compliance of the noncovalently functionalized BNNF nanocomposite is significantly less than the neat epoxy and the nonfunctionalized BNNF nanocomposite. Noncovalent functionalization of BNNFs is effective to increase mechanical properties by strong affinity between the fillers and the matrix. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Setting Mechanical Properties of High Strength Steels for Rapid Hot Forming Processes

    PubMed Central

    Löbbe, Christian; Hering, Oliver; Hiegemann, Lars; Tekkaya, A. Erman

    2016-01-01

    Hot stamping of sheet metal is an established method for the manufacturing of light weight products with tailored properties. However, the generally-applied continuous roller furnace manifests two crucial disadvantages: the overall process time is long and a local setting of mechanical properties is only feasible through special cooling techniques. Hot forming with rapid heating directly before shaping is a new approach, which not only reduces the thermal intervention in the zones of critical formability and requested properties, but also allows the processing of an advantageous microstructure characterized by less grain growth, additional fractions (e.g., retained austenite), and undissolved carbides. Since the austenitization and homogenization process is strongly dependent on the microstructure constitution, the general applicability for the process relevant parameters is unknown. Thus, different austenitization parameters are analyzed for the conventional high strength steels 22MnB5, Docol 1400M, and DP1000 in respect of the mechanical properties. In order to characterize the resulting microstructure, the light optical and scanning electron microscopy, micro and macro hardness measurements, and the X-ray diffraction are conducted subsequent to tensile tests. The investigation proves not only the feasibility to adjust the strength and ductility flexibly, unique microstructures are also observed and the governing mechanisms are clarified. PMID:28773354

  20. Thermo-mechanical properties of boron nitride nanoribbons: A molecular dynamics simulation study.

    PubMed

    Mahdizadeh, Sayyed Jalil; Goharshadi, Elaheh K; Akhlamadi, Golnoosh

    2016-07-01

    Thermo-mechanical properties of boron nitride nanoribbons (BNNRs) were computed using molecular dynamics simulation with optimized Tersoff empirical potential. Thermal conductivity (TC) and heat transport properties of BNNRs were calculated as functions of both temperature and nanoribbon's length. The results show that TC of BNNRs decreases with raising temperature by T(-1.5) up to 1000K. The phonon-phonon scattering relaxation time, mean free path of phonons, and contribution of high frequency optical phonons in TC of BNNRs were calculated at various temperatures. TC decreases as nanoribbon size increases and it converges to ∼500Wm(-1)K(-1) for nanoribbons with length longer than 30nm. The mechanical properties, including Gruneisen parameter, stress-strain response curves, Young's modulus, intrinsic strength, critical strain, and poisson's ratio were calculated in the temperature range of 137-1000K. The simulation results show that Gruneisen parameter and poisson's ratio of BNNRs are -0.092 and 0.245, respectively. The Young's modulus of BNNRs decreases with raising temperature and its value is 630GPa at 300K. According to the results, BNNRs duo to their extraordinary thermo-mechanical properties, are the promising candidate for the future nano-device manufacturing. Copyright © 2016 Elsevier Inc. All rights reserved.