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Sample records for mechanical properties performance

  1. Muscle - tendon unit mechanical and morphological properties and sprint performance.

    PubMed

    Stafilidis, Savvas; Arampatzis, Adamantios

    2007-07-01

    The objective of this study was to determine whether sprint performance is related to the mechanical (elongation - force relationship of the tendon and aponeurosis, muscle strength) and morphological (fascicle length, pennation angle, muscle thickness) properties of the quadriceps femoris and triceps surae muscle - tendon units. Two groups of sprinters (slow, n = 11; fast, n = 17) performed maximal isometric knee extension and plantar flexion contractions on a dynamometer at 11 different muscle - tendon unit lengths. Elongation of the tendon and aponeurosis of the gastrocnemius medialis and the vastus lateralis was measured using ultrasonography. We observed no significant differences in maximal joint moments at the ankle and knee joints or morphological properties of the gastrocnemius medialis and vastus lateralis between groups (P > 0.05). The fast group exhibited greater elongation of the vastus lateralis tendon and aponeurosis at a given tendon force, and greater maximal elongation of the vastus lateralis tendon and aponeurosis during maximum voluntary contraction (P < 0.05). Furthermore, maximal elongation of the vastus lateralis tendon and aponeurosis showed a significant correlation with 100-m sprint times (r = -0.567, P = 0.003). For the elongation - force relationship at the gastrocnemius medialis tendon and aponeurosis, the two groups recorded similar values. It is suggested that the greater elongation of the vastus lateralis tendon and aponeurosis of the fast group benefits energy storage and return as well as the shortening velocity of the muscle - tendon unit.

  2. MECHANICAL PROPERTY CHARACTERIZATIONS AND PERFORMANCE MODELING OF SOFC SEALS

    SciTech Connect

    Koeppel, Brian J.; Vetrano, John S.; Nguyen, Ba Nghiep; Sun, Xin; Khaleel, Mohammad A.

    2008-03-26

    This study provides modeling tools for the design of reliable seals for SOFC stacks. The work consists of 1) experimental testing to determine fundamental properties of SOFC sealing materials, and 2) numerical modeling of stacks and sealing systems. The material tests capture relevant temperature-dependent physical and mechanical data needed by the analytical models such as thermal expansion, strength, fracture toughness, and relaxation behavior for glass-ceramic seals and other materials. Testing has been performed on both homogenous specimens and multiple material assemblies to investigate the effect of interfacial reactions. A viscoelastic continuum damage model for a glass-ceramic seal was developed to capture the nonlinear behavior of this material at high temperatures. This model was implemented in the MSC MARC finite element code and was used for a detailed analysis of a planar SOFC stack under thermal cycling conditions. Realistic thermal loads for the stack were obtained using PNNL’s in-house multiphysics solver. The accumulated seal damage and component stresses were evaluated for multiple thermal loading cycles, and regions of high seal damage susceptible to cracking were identified. Selected test results, numerical model development, and analysis results will be presented.

  3. The Processing and Mechanical Properties of High Temperature/High Performance Composites. Book 5. Processing and Miscellaneous Properties

    DTIC Science & Technology

    1993-04-01

    Processing and Mechanical Properties of High Texniperature/ High Performance Composites by A.G. Evans & F. Leckie University of California, Santa Barbara...University Carnegie Mellon University University of Virginia 93- 13752 Book 5of 5: PROCESSING AND MISCELLANEOUS PROPERTIES 93e • • SUMMARY OF TABLE OF...CONTENTS EXECUTIVE SUMMARY BOOK 1: CONSTITUENT PROPERTIES OF COMPOSITES BOOK 2: CONSTITUENT PROPERTIES AND MACROSCOPIC PERFORMANCE: CMCs BOOK 3

  4. Environmental Effects on the Mechanical Properties of High Performance Fibres

    DTIC Science & Technology

    1976-08-01

    photochemically stable structure2 2 ; its high rate of photodegradation is related to the intense light absorption in the solar spectral region. Outdoor...exposure to sunlight has been shown to be due to photo-oxidationl 8 ; the mechanism of photodegradation in air "and vacuum has been studied by Wiles et a124... dyeing and color stabilization, Celanese Research Company Publication. 24. Carlsson, D.J., Parnell, R.D. and Wiles, D.M. (1973). J. Polym. Sci.,• :•; B

  5. Mechanical properties of high performance fibers vis-a-vis applications in flexible structural composites

    NASA Astrophysics Data System (ADS)

    Sharma, Varunesh

    Some of the critical properties of high performance organic fibers and fiber assemblies have been addressed vis-a-vis their applications in flexible structural composites. These include: tensile properties; mechanical properties under complex modes of deformation; creep at high tensile loads; changes in physical properties due to thermo-mechanical/chemical treatments used in manufacturing of reinforced rubber goods. The axial elastic modulus of fibers and tautly twisted filament assemblies of high performance organic polymers have been measured along with their crystalline orientation distributions. Based on well established procedures in continuum mechanics of axially symmetric structures, a quantitative relationship has been derived to relate the axial elastic modulus to the second and fourth moment of average crystalline orientation distribution. The latter was determined by X-ray diffraction measurements with yarns. This model, valid for single-phase materials, has been found to provide an excellent fit of data from twisted yams of aromatic polyamide and highly ordered polyethylene fibers, with a wide range of overall crystalline orientation distributions. An important property of concern in engineering applications of polymeric filament assemblies of high performance organic fibers is creep. In this study, creep deformation data of gel-spun Ultra High Molecular Weight Polyethylne (UHMWPE) SpectraRTM 1000 yams have been fitted to a model obtained through an empirical mechanical analog of the viscoelastic process. The non-linear viscoelastic model composed of stress-dependent non-linear mechanical analogs qualitatively predicted the creep response to a series of step-loads applied on the UHMWPE yarns. To understand the mechanical properties of high performance organic fibers under combined bending and extension, a simple pin-test procedure has been employed to characterize fibers and twisted yarns. The results obtained from the test have been interpreted with

  6. The Processing and Mechanical Properties of High Temperature/High Performance Composites. Book 3. Constituent Properties and Macroscopic Performance: MMCs

    DTIC Science & Technology

    1993-04-01

    program strategy concerned with design attempts to provide a balance of effort between properties and design by having studies of mechanisms and...ultimate strength of the fiber bundle without matrix. The applied stress exceeds Oc and the balance in excess of the amount borne by the intact...CONSIDERATIONS fiber radius. R. through the fiber volume fraction f, Statistical considerations dictate that some fibers in acordance with in the

  7. Evaluation of mechanical properties and durability performance of HDPE-wood composites

    SciTech Connect

    Tazi, M.; Erchiqui, F.; Kaddami, H.; Bouazara, M.; Poaty, B.

    2015-05-22

    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 used 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.

  8. Evaluation of mechanical properties and durability performance of HDPE-wood composites

    NASA Astrophysics Data System (ADS)

    Tazi, M.; Erchiqui, F.; Kaddami, H.; Bouazara, M.; Poaty, B.

    2015-05-01

    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 used 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

  9. MICROSTRUCTURE AND MECHANICAL PROPERTY PERFORMANCE OF COMMERCIAL GRADE API PIPELINE STEELS IN HIGH PRESSURE GASEOUS HYDROGEN

    SciTech Connect

    Stalheim, Mr. Douglas; Boggess, Todd; San Marchi, Chris; Jansto, Steven; Somerday, Dr. B; Muralidharan, Govindarajan; Sofronis, Prof. Petros

    2010-01-01

    The continued growth of the world s developing countries has placed an ever increasing demand on traditional fossil fuel energy sources. This development has lead to increasing research and development of alternative energy sources. Hydrogen gas is one of the potential alternative energy sources under development. Currently the most economical method of transporting large quantities of hydrogen gas is through steel pipelines. It is well known that hydrogen embrittlement has the potential to degrade steel s mechanical properties when hydrogen migrates into the steel matrix. Consequently, the current pipeline infrastructure used in hydrogen transport is typically operated in a conservative fashion. This operational practice is not conducive to economical movement of significant volumes of hydrogen gas as an alternative to fossil fuels. The degradation of the mechanical properties of steels in hydrogen service is known to depend on the microstructure of the steel. Understanding the levels of mechanical property degradation of a given microstructure when exposed to hydrogen gas under pressure can be used to evaluate the suitability of the existing pipeline infrastructure for hydrogen service and guide alloy and microstructure design for new hydrogen pipeline infrastructure. To this end, the 2 Copyright 2010 by ASME microstructures of relevant steels and their mechanical properties in relevant gaseous hydrogen environments must be fully characterized to establish suitability for transporting hydrogen. A project to evaluate four commercially available pipeline steels alloy/microstructure performance in the presences of gaseous hydrogen has been funded by the US Department of Energy along with the private sector. The microstructures of four pipeline steels were characterized and then tensile testing was conducted in gaseous hydrogen and helium at pressures of 800, 1600 and 3000 psi. Based on measurements of reduction of area, two of the four steels that performed the best

  10. The Processing and Mechanical Properties of High Temperature/ High Performance Composites. Stress Redistribution and Notch Properties. Book 2

    DTIC Science & Technology

    1994-03-01

    The Processing and Mechanical Properties of High Temperature/ High Performance Composites by A.G. Evans & F. Leckie - 4 University of California...Chan Ceramic Layered Composites M. Y He J. W. Hutchinson 20. Notch Sensitivity and Stress T. J. Mackin Redistribution in CMCs T. E. Purcell M. YHe A...G. Evans 2 1. Notch-Sensitivity and Shear Bands in M. -Y. He Brittle Matrix Composites B. Wu Z. Suo 22. On Large Scale Sliding in Fiber- Z. C. XMa

  11. Mechanical, hydric and thermal properties of fine-grained high performance concrete

    NASA Astrophysics Data System (ADS)

    KoÅáková, D.; Čáchová, M.; Doleželová, M.; Kočí, V.; Vejmelková, E.; Černý, R.

    2017-02-01

    The experimental analysis of several types of fine-grained high performance concretes is presented in this paper. Besides mechanical parameters, presented analysis aims also at determination of basic physical and heat and moisture transport and storage parameters. Within the frame of this paper, three different mixtures of fine-grained high performance concrete were designed, distinguished by the type of binder (unitary-, binary- or ternary-based) and their properties were compared with two types common concretes. Experimental results show that the compressive and bending strength, static modulus of elasticity of high performance concretes are significantly better than for other two concrete mixtures, regardless of the type of binder. Thermal conductivity of high performance concretes was higher in dry state, but due to lower open porosity and lower values of moisture diffusivity these concretes are more resistance to liquid moisture intake, therefore they evince better thermal properties in fully saturated state. Since the ternary-based high performance concrete contains also secondary raw materials as partial cement replacement and its properties were mostly better than other investigated concretes, it can be considered as an environmental friendly solution.

  12. Thrust chamber life prediction. Volume 1: Mechanical and physical properties of high performance rocket nozzle materials

    NASA Technical Reports Server (NTRS)

    Esposito, J. J.; Zabora, R. F.

    1975-01-01

    Pertinent mechanical and physical properties of six high conductivity metals were determined. The metals included Amzirc, NARloy Z, oxygen free pure copper, electroformed copper, fine silver, and electroformed nickel. Selection of these materials was based on their possible use in high performance reusable rocket nozzles. The typical room temperature properties determined for each material included tensile ultimate strength, tensile yield strength, elongation, reduction of area, modulus of elasticity, Poisson's ratio, density, specific heat, thermal conductivity, and coefficient of thermal expansion. Typical static tensile stress-strain curves, cyclic stress-strain curves, and low-cycle fatigue life curves are shown. Properties versus temperature are presented in graphical form for temperatures from 27.6K (-410 F) to 810.9K (1000 F).

  13. Toward intrinsically stretchable organic semiconductors: mechanical properties of high-performance conjugated polymers

    NASA Astrophysics Data System (ADS)

    Sawyer, Eric J.; Savagatrup, Suchol; O'Connor, Timothy F.; Makaram, Aditya S.; Burke, Daniel J.; Zaretski, Aliaksandr V.; Printz, Adam D.; Lipomi, Darren J.

    2014-10-01

    This paper describes several approaches to understanding and improving the response of π-conjugated (semiconducting) polymers to tensile strain. Our principal goal was to establish the design criteria for introducing elasticity and ductility in conjugated (semiconducting) polymers through a rigorous analysis of the structural determinants of the mechanical properties of this type of material. We elucidated the details of the effect of the alkyl side chain length on the mechanical properties of regioregular polythiophene and used this analysis to select materials for stretching and transfer printing of organic solar cells to hemispherical substrates. This demonstration represents the first time that a conjugated polymer device has ever been stretched and conformally bonded to a complex 3D surface (i.e., other than a cone or cylinder, for which flexibility—as opposed to stretchability—is sufficient). We then further explored the details of the dependence of the mechanical properties on the side chain of a semiconducting polymer by synthesizing a series of hybrid materials (block and random copolymers) containing both short and long side chains. This analysis revealed the unusual semiconducting polymer, poly(3-heptylthiophene), as having an excellent combination of mechanical and electronic properties. In parallel, we explored a new method of producing "blocky" copolymers using a new procedure based on random segmentation of conjugated monomers. We found that introduction of structural randomness increased the elasticity without having detrimental effects on the photovoltaic performance. We also describe methods of synthesizing large volumes of conjugated polymers in environmentally benign ways that were amenable to manufacturing.

  14. Charge storage mechanisms in electrochemical capacitors: Effects of electrode properties on performance

    NASA Astrophysics Data System (ADS)

    Dupont, Madeleine F.; Donne, Scott W.

    2016-09-01

    The capacitive behaviour of four commonly studied electrochemical capacitor systems has been analyzed using the step potential electrochemical spectroscopy (SPECS) method. Electrode-electrolyte combinations with different charge storage mechanisms were characterized, including activated carbon in aqueous (H2SO4) and organic (TEABF4 in acetonitrile) electrolytes, manganese dioxide (Na2SO4) and anhydrous ruthenium oxide (H2SO4). The SPECS method was used to separate the charge storage contributions from double layer capacitance (CDL) and diffusion-limited pseudo-capacitance (CD) at scan rates ranging from 0.08 to 125 mV/s. The relative contributions from each process are related to the physicochemical properties of the electrode. Additionally, the effects of these electrode properties on the overall performance of each system, in terms of specific power and energy, are identified.

  15. Mechanical performance and ultrasonic properties of cemented gangue backfill with admixture of fly ash.

    PubMed

    Wu, Di; Zhang, Yongliang; Liu, Yucheng

    2016-01-01

    Cemented gangue backfill (CGB) is prepared by mixing cement, coal gangue and water. Fly ash from the combustion of coal is commonly utilized as admixture to improve the mechanical performance and fluidity of CGB, as well as to reduce cost of preparing CGB. Uniaxial compressive strength (UCS) is one of the most commonly used indicators for evaluating the mechanical performance of CGB. Ultrasonic testing, which is a non-destructive measurement, can also be applied to determine the mechanical properties of cementitious materials such as CGB. So this paper investigates the UCS and ultrasonic pulse velocity (UPV) of CGB prepared at different fly ash dosage (19, 20 and 21 wt.%) and solid content (76.5, 77.5 and 78.5 wt.%), versus curing periods of 3-28 days. The UCS and UPV values of CGB increase with increasing fly ash dosage and solid content. In order to find out the correlation between the UCS and UPV values of CGB, different types (linear, logarithmic, exponential and power) of curve fitting are conducted on the CGB samples made at different solid content. An exponential relationship with the correlation coefficient of 0.959 appears to exist between the UCS and UPV for CGB samples. This obtained exponential relationship is validated to be available by performing the t- and F- tests. The results acquired by this paper are capable of providing guidance for utilizing UPV test to estimate the strength of underground CGB structures.

  16. Selection of helical braided flow diverter stents based on hemodynamic performance and mechanical properties.

    PubMed

    Suzuki, Takashi; Takao, Hiroyuki; Fujimura, Soichiro; Dahmani, Chihebeddine; Ishibashi, Toshihiro; Mamori, Hiroya; Fukushima, Naoya; Yamamoto, Makoto; Murayama, Yuichi

    2017-10-01

    Although flow diversion is a promising procedure for the treatment of aneurysms, complications have been reported and it remains poorly understood. The occurrence of adverse outcomes is known to depend on both the mechanical properties and flow reduction effects of the flow diverter stent. To clarify the possibility of designing a flow diverter stent considering both hemodynamic performance and mechanical properties. Computational fluid dynamics (CFD) simulations were conducted based on an ideal aneurysm model with flow diverters. Structural analyses of two flow diverter models exhibiting similar flow reduction effects were performed, and the radial stiffness and longitudinal flexibility were compared. In CFD simulations, two stents-Pore2-d35 (26.77° weave angle when fully expanded, 35 μm wire thickness) and Pore3-d50 (36.65°, 50 μm respectively)-demonstrated similar flow reduction rates (68.5% spatial-averaged velocity reduction rate, 85.0% area-averaged wall shear stress reduction rate for Pore2-d35, and 68.6%, 85.4%, respectively, for Pore3-d50). However, Pore3-d50 exhibited greater radial stiffness than Pore2-d35 (40.0 vs 21.0 mN/m at a 3.5 mm outer diameter) and less longitudinal flexibility (0.903 vs 0.104 N·mm bending moments at 90°). These measurements indicate that changing the wire thickness and weave angle allows adjustment of the mechanical properties while maintaining the same degree of flow reduction effects. The combination of CFD and structural analysis can provide promising solutions for an optimized stent. Stents exhibiting different mechanical properties but the same flow reduction effects could be designed by varying both the weave angle and wire thickness. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  17. Lower limb kinematic variability in dancers performing drop landings onto floor surfaces with varied mechanical properties.

    PubMed

    Reeve, Helen K; Hopper, Luke S; Elliott, Bruce C; Ackland, Timothy R

    2013-08-01

    Elite dancers perform highly skilled and consistent movements. These movements require effective regulation of the intrinsic and extrinsic forces acting within and on the body. Customized, compliant floors typically used in dance are assumed to enhance dance performance and reduce injury risk by dampening ground reaction forces during tasks such as landings. As floor compliance can affect the extrinsic forces applied to the body, secondary effects of floor properties may be observed in the movement consistency or kinematic variability exhibited during dance performance. The aim of this study was to investigate the effects of floor mechanical properties on lower extremity kinematic variability in dancers performing landing tasks. A vector coding technique was used to analyze sagittal plane knee and ankle joint kinematic variability, in a cohort of 12 pre-professional dancers, through discrete phases of drop landings from a height of 0.2m. No effect on kinematic variability was observed between floors, indicating that dancers could accommodate the changing extrinsic floor conditions. Future research may consider repeat analysis under more dynamic task constraints with a less experienced cohort. However, knee/ankle joint kinematic variability was observed to increase late in the landing phase which was predominantly comprised of knee flexion coupled with the terminal range of ankle dorsiflexion. These findings may be the result of greater neural input late in the landing phase as opposed to the suggested passive mechanical interaction of the foot and ankle complex at initial contact with a floor. Analysis of joint coordination in discrete movement phases may be of benefit in identifying intrinsic sources of variability in dynamic tasks that involve multiple movement phases. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Comparing the mechanical properties of high performances polymer nanocomposites from biological sources.

    PubMed

    Dufresne, Alain

    2006-02-01

    There are numerous examples where animals or plants synthesize extracellular high-performance skeletal biocomposites consisting of a matrix reinforced by fibrous biopolymers. Cellulose and chitin are classical examples of these reinforcing elements, which occur as whisker-like microfibrils that are biosynthesized and deposited in a continuous fashion. In many cases, this mode of biogenesis leads to crystalline microfibrils that are almost defect-free, with the consequence of axial physical properties approaching those of perfect crystals. Starch is another example of natural semicrystalline polymer that is produced by many plants and occurs as microscopic granules. It acts as a storage polymer in cereals and tubers. These abundant and natural polymers can be used to create high performance nanocomposites presenting outstanding properties. Aqueous suspensions of crystallites can be prepared by acid hydrolysis of the purified substrates. The object of this treatment is to dissolve away regions of low lateral order so that the water-insoluble, highly crystalline residue may be converted into a stable suspension by subsequent vigorous mechanical shearing action. For cellulose and chitin, these monocrystals appear as rod-like nanoparticles which dimensions depend on the biological source of the substrate. In the case of starch they consist of platelet-like nanoparticles. High reinforcing capability was reported resulting from the intrinsic chemical nature of these polymers and from their hierarchical structure. During the last decade, many works have been devoted to mimic biocomposites by blending cellulose whiskers from different sources with polymer matrices.

  19. Stunting delays maturation of triceps surae mechanical properties and motor performance in prepubertal children.

    PubMed

    Paiva, Maria das Graças; Souza, Thaysa O L; Canon, Francis; Pérot, Chantal; Xavier, Luciana C C; Ferraz, Karla M; Osório, Mônica M; Manhães-de-Castro, Raul; Lambertz, Daniel

    2012-12-01

    Malnutrition can lead to possible irreversible consequences in the development of muscle function and some of them are yet poorly characterized. The present study evaluated the mechanical properties of the triceps surae and motor performance in stunted (S) and eutrophic (E) prepubertal children (9 years ± 6 months). Height-for-age ratio was used as indicator of stunting due to early malnutrition, according to the World Health Organization. Torque was determined by maximal voluntary contractions (MVC) and musculotendinous (MT) stiffness was achieved through quick-release tests to obtain MT stiffness index (SI(MT)) and passive stiffness (K (p)) from linear MT stiffness-torque relationships. Percutaneous supramaximal electrically elicited contractions determined twitch torque (Pt) and electromechanical delay (EMD). Motor performance was evaluated by balance test. S group presented significantly lower MVC and a trend of lower Pt values indicating lower capacities to develop force under voluntary or induced conditions. Significantly higher SI(MT) and EMD values were observed, while K (p) and motor performance in balance were significantly lower. Higher SI(MT) values have been reported previously in youngest prepubertal children, indicating that immature activation capacities can mask MT stiffness assessment during voluntary contractions, taking into consideration the higher EMD values as a measure of muscle stiffness contribution. Lower K (p) may indicate a delay in the maturation of tendinous tissue in S group, influencing motor performance in balance. The present study shows that malnutrition leads to adaptation of intrinsic MT elastic properties, but depends on the level of the observed structure.

  20. Mechanical properties testing of candidate polymer matrix materials for use in high performance composites

    NASA Technical Reports Server (NTRS)

    Zimmerman, R. S.; Adams, D. F.

    1985-01-01

    The mechanical properties of four candidate neat resin systems for use in graphite/epoxy composites are characterized. This includes tensile and shear stiffnesses and strengths, coefficients of thermal and moisture expansion, and fracture toughness. Tests are conducted on specimens in the dry state and moisture-saturated, at temperatures of 23C, 82C and 121C. The neat resins tested are Hexcel HX-1504, Narmco 5245-C, American Cyanamid CYCOM 907, and Union Carbide ERX-4901A (MDA). Results are compared with those obtained for four other epoxy resins tested in a prior program, i.e., Hercules 3502, 2220-1, and 2220-3, and Ciba-Geigy Fibredux 914, as well as with available Hercules 3501-6 data. Scanning electron microscopic examination of fracture surfaces is performed to permit the correlation of observed failure modes with the environmental test conditions. A finite element micromechanics analysis is used to predict unidirectional composite response under various test conditions, using the measured neat resin properties as input data.

  1. Properties and Performance Attributes of Novel Co-Extruded Polyolefin Battery Separator Materials. Part 1; Mechanical Properties

    NASA Technical Reports Server (NTRS)

    Baldwin, Richard S.; Guzik, Monica; Skierski, Michael

    2011-01-01

    As NASA prepares for its next era of manned spaceflight missions, advanced energy storage technologies are being developed and evaluated to address future mission needs and technical requirements and to provide new mission-enabling technologies. Cell-level components for advanced lithium-ion batteries possessing higher energy, more reliable performance and enhanced, inherent safety characteristics are actively under development within the NASA infrastructure. A key component for safe and reliable cell performance is the cell separator, which separates the two energetic electrodes and functions to prevent the occurrence of an internal short-circuit while enabling ionic transport. Recently, a new generation of co-extruded separator films has been developed by ExxonMobil Chemical and introduced into their battery separator product portfolio. Several grades of this new separator material have been evaluated with respect to dynamic mechanical properties and safety-related performance attributes. This paper presents the results of these evaluations in comparison to a current state-ofthe-practice separator material. The results are discussed with respect to potential opportunities to enhance the inherent safety characteristics and reliability of future, advanced lithium-ion cell chemistries.

  2. Traits, properties, and performance: how woody plants combine hydraulic and mechanical functions in a cell, tissue, or whole plant.

    PubMed

    Lachenbruch, Barbara; McCulloh, Katherine A

    2014-12-01

    This review presents a framework for evaluating how cells, tissues, organs, and whole plants perform both hydraulic and mechanical functions. The morphological alterations that affect dual functionality are varied: individual cells can have altered morphology; tissues can have altered partitioning to functions or altered cell alignment; and organs and whole plants can differ in their allocation to different tissues, or in the geometric distribution of the tissues they have. A hierarchical model emphasizes that morphological traits influence the hydraulic or mechanical properties; the properties, combined with the plant unit's environment, then influence the performance of that plant unit. As a special case, we discuss the mechanisms by which the proxy property wood density has strong correlations to performance but without direct causality. Traits and properties influence multiple aspects of performance, and there can be mutual compensations such that similar performance occurs. This compensation emphasizes that natural selection acts on, and a plant's viability is determined by, its performance, rather than its contributing traits and properties. Continued research on the relationships among traits, and on their effects on multiple aspects of performance, will help us better predict, manage, and select plant material for success under multiple stresses in the future.

  3. Composition, structure and mechanical properties define performance of pulmonary surfactant membranes and films.

    PubMed

    Parra, Elisa; Pérez-Gil, Jesús

    2015-01-01

    The respiratory surface in the mammalian lung is stabilized by pulmonary surfactant, a membrane-based system composed of multiple lipids and specific proteins, the primary function of which is to minimize the surface tension at the alveolar air-liquid interface, optimizing the mechanics of breathing and avoiding alveolar collapse, especially at the end of expiration. The goal of the present review is to summarize current knowledge regarding the structure, lipid-protein interactions and mechanical features of surfactant membranes and films and how these properties correlate with surfactant biological function inside the lungs. Surfactant mechanical properties can be severely compromised by different agents, which lead to surfactant inhibition and ultimately contributes to the development of pulmonary disorders and pathologies in newborns, children and adults. A detailed comprehension of the unique mechanical and rheological properties of surfactant layers is crucial for the diagnostics and treatment of lung diseases, either by analyzing the contribution of surfactant impairment to the pathophysiology or by improving the formulations in surfactant replacement therapies. Finally, a short review is also included on the most relevant experimental techniques currently employed to evaluate lung surfactant mechanics, rheology, and inhibition and reactivation processes. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  4. Improved Mechanical Performance Fracture Properties and Reliability of Radical-Cured Thermosets

    SciTech Connect

    Redline, Erica Marie; Bolintineanu, Dan S.; Lane, J. Matthew; Stevens, Mark J.; Alam, Todd M.; Celina, Mathias C.

    2016-10-01

    The aim of this study was to alter polymerization chemistry to improve network homogeneity in free-radical crosslinked systems. It was hypothesized that a reduction in heterogeneity of the network would lead to improved mechanical performance. Experiments and simulations were carried out to investigate the connection between polymerization chemistry, network structure and mechanical properties. Experiments were conducted on two different monomer systems - the first is a single monomer system, urethane dimethacrylate (UDMA), and the second is a two-monomer system consisting of bisphenol A glycidyl dimethacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA) in a ratio of 70/30 BisGMA/TEGDMA by weight. The methacrylate systems were crosslinked using traditional radical polymeriza- tion (TRP) with azobisisobutyronitrile (AIBN) or benzoyl peroxide (BPO) as an initiator; TRP systems were used as the control. The monomers were also cross-linked using activator regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) as a type of controlled radical polymerization (CRP). FTIR and DSC were used to monitor reac- tion kinetics of the systems. The networks were analyzed using NMR, DSC, X-ray diffraction (XRD), atomic force microscopy (AFM), and small angle X-ray scattering (SAXS). These techniques were employed in an attempt to quantify differences between the traditional and controlled radical polymerizations. While a quantitative methodology for characterizing net- work morphology was not established, SAXS and AFM have shown some promising initial results. Additionally, differences in mechanical behavior were observed between traditional and controlled radical polymerized thermosets in the BisGMA/TEGDMA system but not in the UDMA materials; this finding may be the result of network ductility variations between the two materials. Coarse-grained molecular dynamics simulations employing a novel model of the CRP reaction were carried out for

  5. The Processing and Mechanical Properties of High Temperature/ High Performance Composites. Fatigue and Creep. Book 3

    DTIC Science & Technology

    1994-03-01

    Properties of High Temperature! High Performance Composites by A.G. Evans & F. Leckie AS’ University of California, Santa Barbara ... University of...MATRIX COMPOSITE D. P. WALLSt, G. BAO and F. W. ZOK Materials Department, University of California, Santa Barbara , CA 93106-5050, U.S.A. (Received 8 June...Zok Materials Department University of California Santa Barbara , California 93106 *Presently at United Technologies, Pratt & Whitney Mail Stop 707-22

  6. Direct correlation of single-molecule properties with bulk mechanical performance for the biomimetic design of polymers.

    PubMed

    Chung, Jaeyoon; Kushner, Aaron M; Weisman, Adam C; Guan, Zhibin

    2014-11-01

    For rational design of advanced polymeric materials, it is critical to establish a clear mechanistic link between the molecular structure of a polymer and the emergent bulk mechanical properties. Despite progress towards this goal, it remains a major challenge to directly correlate the bulk mechanical performance to the nanomechanical properties of individual constituent macromolecules. Here, we show a direct correlation between the single-molecule nanomechanical properties of a biomimetic modular polymer and the mechanical characteristics of the resulting bulk material. The multi-cyclic single-molecule force spectroscopy (SMFS) data enabled quantitative derivation of the asymmetric potential energy profile of individual module rupture and re-folding, in which a steep dissociative pathway accounted for the high plateau modulus, while a shallow associative well explained the energy-dissipative hysteresis and dynamic, adaptive recovery. These results demonstrate the potential for SMFS to serve as a guide for future rational design of advanced multifunctional materials.

  7. Influence of mechanical properties of alginate-based substrates on the performance of Schwann cells in culture.

    PubMed

    Ning, Liqun; Xu, Yitong; Chen, Xiongbiao; Schreyer, David J

    2016-06-01

    In tissue engineering, artificial tissue scaffolds containing living cells have been studied for tissue repair and regeneration. Notably, the performance of these encapsulated-in-scaffolds cells in terms of cell viability, proliferation, and expression of function during and after the scaffold fabrication process, has not been well documented because of the influence of mechanical, chemical, and physical properties of the scaffold substrate materials. This paper presents our study on the influence of mechanical properties of alginate-based substrates on the performance of Schwann cells, which are the major glial cells of peripheral nervous system. Given the fact that alginate polysaccharide hydrogel has poor cell adhesion properties, in this study, we examined several types of cell-adhesion supplements and found that alginate covalently modified with RGD peptide provided improved cell proliferation and adhesion. We prepared alginate-based substrates for cell culture using varying alginate concentrations for altering their mechanical properties, which were confirmed by compression testing. Then, we examined the viability, proliferation, morphology, and expression of the extracellular matrix protein laminin of Schwann cells that were seeded on the surface of alginate-based substrates (or 2D culture) or encapsulated within alginate-based substrates (3D cultures), and correlated the examined cell performance to the alginate concentration (or mechanical properties) of hydrogel substrates. Our findings suggest that covalent attachment of RGD peptide can improve the success of Schwann cell encapsulation within alginate-based scaffolds, and provide guidance for regulating the mechanical properties of alginate-based scaffolds containing Schwann cells for applications in peripheral nervous system regeneration and repair.

  8. Molecular dynamics study of binding energies, mechanical properties, and detonation performances of bicyclo-HMX-based PBXs.

    PubMed

    Qiu, Ling; Xiao, Heming

    2009-05-15

    To investigate the effect of polymer binders on the monoexplosive, molecular dynamics simulations were performed to study the binding energies, mechanical properties, and detonation performances of the bicyclo-HMX-based polymer-bonded explosives (PBXs). The results show that the binding energies on different crystalline surfaces of bicyclo-HMX decrease in the order of (010)>(100)>(001). On each crystalline surface, binding properties of different polymers with the same chain segment are different from each other, while those of the polymers in the same content decrease in the sequence of PVDF>F(2311)>F(2314) approximately PCTFE. The mechanical properties of a dozen of model systems (elastic coefficients, various moduli, Cauchy pressure, and Poisson's ratio) have been obtained. It is found that mechanical properties are effectively improved by adding small amounts of fluorine polymers, and the overall effect of fluorine polymers on three crystalline surfaces of bicyclo-HMX changes in the order of (010)>(001) approximately (100). In comparison with the base explosive, detonation performances of the PBXs decrease slightly, but they are still superior to TNT. These suggestions may be useful for the formulation design of bicyclo-HMX-based PBXs.

  9. Characterization of HTPB-based solid fuel formulations: Performance, mechanical properties, and pollution

    NASA Astrophysics Data System (ADS)

    DeLuca, L. T.; Galfetti, L.; Maggi, F.; Colombo, G.; Merotto, L.; Boiocchi, M.; Paravan, C.; Reina, A.; Tadini, P.; Fanton, L.

    2013-12-01

    Features such as safety, low-cost, and throttleability make hybrid rocket engines an attractive option for suborbital flights and space exploration missions in general. While the domain of possible liquid oxidizers is well characterized, the choice of a suitable solid fuel is still a matter of investigation. Space Propulsion Laboratory (SPLab) at Politecnico di Milano has developed a series of proprietary techniques to evaluate, on a relative grading, the quality of innovative solid fuels while visualizing at the same time their flame structure. But a serious alert was recently notified that soot emission from hydrocarbon fuels has the potential to contribute to global climate change. In this paper, HTPB polymer has been taken as baseline and characterized at laboratory level in terms of ballistic properties, mechanical testing, and thermochemical calculations.

  10. Hemodynamic Performance and Thrombogenic Properties of a Superhydrophobic Bileaflet Mechanical Heart Valve.

    PubMed

    Bark, David L; Vahabi, Hamed; Bui, Hieu; Movafaghi, Sanli; Moore, Brandon; Kota, Arun K; Popat, Ketul; Dasi, Lakshmi P

    2017-02-01

    In this study, we explore how blood-material interactions and hemodynamics are impacted by rendering a clinical quality 25 mm St. Jude Medical Bileaflet mechanical heart valve (BMHV) superhydrophobic (SH) with the aim of reducing thrombo-embolic complications associated with BMHVs. Basic cell adhesion is evaluated to assess blood-material interactions, while hemodynamic performance is analyzed with and without the SH coating. Results show that a SH coating with a receding contact angle (CA) of 160° strikingly eliminates platelet and leukocyte adhesion to the surface. Alternatively, many platelets attach to and activate on pyrolytic carbon (receding CA = 47), the base material for BMHVs. We further show that the performance index increases by 2.5% for coated valve relative to an uncoated valve, with a maximum possible improved performance of 5%. Both valves exhibit instantaneous shear stress below 10 N/m(2) and Reynolds Shear Stress below 100 N/m(2). Therefore, a SH BMHV has the potential to relax the requirement for antiplatelet and anticoagulant drug regimens typically required for patients receiving MHVs by minimizing blood-material interactions, while having a minimal impact on hemodynamics. We show for the first time that SH-coated surfaces may be a promising direction to minimize thrombotic complications in complex devices such as heart valves.

  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. 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)

  13. Mechanical and antibacterial properties of novel high performance chitosan/nanocomposite films.

    PubMed

    Youssef, Ahmed M; Abou-Yousef, Hussein; El-Sayed, Samah M; Kamel, Samir

    2015-05-01

    Zinc oxide (ZnO) nanoparticle was successfully synthesized using hydrothermal method as well as, silver (Ag) nanoparticle was direct prepared during chitosan nanocomposites preparation. Chitosan films were investigated by recognized the effect of kinds of acids (formic or acetic acid). Correspondingly, using of concentrated NaOH was checking for facilitating de-casting of the films. Utilization of formic acid arisen higher quality films than those films produced using acetic acid as solvent. Optimization was based on the mechanical properties for both types of acids solvent. Furthermore, the elasticity of the prepared films was enhanced by blending hydroxyl ethylcellulose (HEC) with chitosan. Loading the films by silver and zinc oxide nanoparticles (Ag-NPs and ZnO) was achieved during the preparation of films under the optimum conditions. Characterizations of the prepared ZnO nanoparticles and the prepared nanocomposites films were investigated by FT-IR, XRD, SEM, TEM and EDAX. Chitosan nanocomposite films displayed good Antimicrobial activity against Staphylococcus aureus, Escherichia coli, Salmonella typhamrium, Bacillus cereus, and Listeria monocyte. Therefore, these films can be used for packaging applications.

  14. Effect of expansive admixtures on the shrinkage and mechanical properties of high-performance fiber-reinforced cement composites.

    PubMed

    Choi, Won-Chang; Yun, Hyun-Do

    2013-01-01

    High-performance fiber-reinforced cement composites (HPFRCCs) are characterized by strain-hardening and multiple cracking during the inelastic deformation process, but they also develop high shrinkage strain. This study investigates the effects of replacing Portland cement with calcium sulfoaluminate-based expansive admixtures (CSA EXAs) to compensate for the shrinkage and associated mechanical behavior of HPFRCCs. Two types of CSA EXA (CSA-K and CSA-J), each with a different chemical composition, are used in this study. Various replacement ratios (0%, 8%, 10%, 12%, and 14% by weight of cement) of CSA EXA are considered for the design of HPFRCC mixtures reinforced with 1.5% polyethylene (PE) fibers by volume. Mechanical properties, such as shrinkage compensation, compressive strength, flexural strength, and direct tensile strength, of the HPFRCC mixtures are examined. Also, crack width and development are investigated to determine the effects of the EXAs on the performance of the HPFRCC mixtures, and a performance index is used to quantify the performance of mixture. The results indicate that replacements of 10% CSA-K (Type 1) and 8% CSA-J (Type 2) considerably enhance the mechanical properties and reduce shrinkage of HPFRCCs.

  15. Effect of Expansive Admixtures on the Shrinkage and Mechanical Properties of High-Performance Fiber-Reinforced Cement Composites

    PubMed Central

    Choi, Won-Chang; Yun, Hyun-Do

    2013-01-01

    High-performance fiber-reinforced cement composites (HPFRCCs) are characterized by strain-hardening and multiple cracking during the inelastic deformation process, but they also develop high shrinkage strain. This study investigates the effects of replacing Portland cement with calcium sulfoaluminate-based expansive admixtures (CSA EXAs) to compensate for the shrinkage and associated mechanical behavior of HPFRCCs. Two types of CSA EXA (CSA-K and CSA-J), each with a different chemical composition, are used in this study. Various replacement ratios (0%, 8%, 10%, 12%, and 14% by weight of cement) of CSA EXA are considered for the design of HPFRCC mixtures reinforced with 1.5% polyethylene (PE) fibers by volume. Mechanical properties, such as shrinkage compensation, compressive strength, flexural strength, and direct tensile strength, of the HPFRCC mixtures are examined. Also, crack width and development are investigated to determine the effects of the EXAs on the performance of the HPFRCC mixtures, and a performance index is used to quantify the performance of mixture. The results indicate that replacements of 10% CSA-K (Type 1) and 8% CSA-J (Type 2) considerably enhance the mechanical properties and reduce shrinkage of HPFRCCs. PMID:24376382

  16. Prediction of fish body's passive visco-elastic properties and related muscle mechanical performance in vivo during steady swimming

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Yu, YongLiang; Tong, BingGang

    2014-01-01

    For attaining the optimized locomotory performance of swimming fishes, both the passive visco-elastic properties of the fish body and the mechanical behavior of the active muscles should coordinate with the fish body's undulatory motion pattern. However, it is difficult to directly measure the visco-elastic constitutive relation and the muscular mechanical performance in vivo. In the present paper, a new approach based on the continuous beam model for steady swimming fish is proposed to predict the fish body's visco-elastic properties and the related muscle mechanical behavior in vivo. Given the lateral travelling-wave-like movement as the input condition, the required muscle force and the energy consumption are functions of the fish body's visco-elastic parameters, i.e. the Young's modulus E and the viscosity coefficient µ in the Kelvin model. After investigating the variations of the propagating speed of the required muscle force with the fish body's visco-elastic parameters, we analyze the impacts of the visco-elastic properties on the energy efficiencies, including the energy utilization ratios of each element of the kinematic chain in fish swimming and the overall efficiency. Under the constraints of reasonable wave speed of muscle activation and the physiological feasibility, the optimal design of the passive visco-elastic properties can be predicted aiming at maximizing the overall efficiency. The analysis is based on the small-amplitude steady swimming of the carangiform swimmer, with typical Reynolds number varying from 2.5×104 to 2.5×105, and the present results show that the non-dimensional Young's modulus is 112±34, and the non-dimensional viscosity coefficient is 13 approximately. In the present estimated ranges, the overall efficiency of the swimming fish is insensitive to the viscosity, and its magnitude is about 0.11±0.02, in the predicted range given by previous study.

  17. Mechanical properties of viruses.

    PubMed

    de Pablo, Pedro J; Mateu, Mauricio G

    2013-01-01

    Structural biology techniques have greatly contributed to unveil the relationships between structure, properties and functions of viruses. In recent years, classic structural approaches are being complemented by single-molecule techniques such as atomic force microscopy and optical tweezers to study physical properties and functions of viral particles that are not accessible to classic structural techniques. Among these features are mechanical properties such as stiffness, intrinsic elasticity, tensile strength and material fatigue. The field of virus mechanics is contributing to materials science by investigating some physical parameters of "soft" biological matter and biological nano-objects. Virus mechanics studies are also starting to unveil the biological implications of physical properties of viruses. Growing evidence indicate that viruses are subjected to internal and external forces, and that they may have adapted to withstand and even use those forces. This chapter describes what is known on the mechanical properties of virus particles, their structural determinants, and possible biological implications, of which several examples are provided.

  18. Relationship between Composition, Structure, Properties, Thermo-Mechanical Processing and Ballistic Performance of Tungsten Heavy Alloys

    DTIC Science & Technology

    1991-11-01

    87 20mm Balistic Testing Talor Anvil Tests Olin 20mm Phalanx Testing ABSTRACT...Penetrator 0.238" x 2.38"’ heminose (0.605 x 6.05 cm) Target 1" (2.54 cm) thick High Hard Armor (MIL-A-46100) Rockwell C 48.5 to 50 Target Angle 57" * 93...appendices of the report. Also in the appendices are the hardness and impact tests on the armor we used. V-50 Determination: The ballistic property we

  19. Effect of Surface and Mechanical Properties on Silicon Nitride Bearing Element Performance

    DTIC Science & Technology

    1975-02-01

    other abrasives such as silicon carbide and Borazon usod in this program. Silicon Ni.tride has a lower than normal abrasive wear resistance for ceramics...using 600 grit (25 um) SiC and 15 pm CBN Borazon (14) snowed that Borazon gives a higher material . A removal rate under identical lapping conditions...Since’ Borazon is similar to diamond in its cutting properties, the reason for the superiority of SiC over diamond found in Gielisse’s investigation is

  20. Structure-Property Relationships for Optimal Thermo-Mechanical Performance in Organic Cyanate Ester

    DTIC Science & Technology

    2013-02-05

    ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NO. Air Force Research Laboratory (AFMC) AFRL/RQRP 10 E. Saturn Blvd...close to the maximum possible extent of conversion (via in-situ cure) at the point where decomposition begins BADCy 10 ºC/min Cyanurate rings de...DISTRIBUTION A: Approved for public release; distribution is unlimite . Role of Co-Network Formation in Moisture Uptake 16 0.00% 0.50% 1.00% 1.50

  1. Microstructure evolution and tensile mechanical properties of thixoformed high performance Al-Zn-Mg-Cu alloy

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Chen, Qiang; Wang, Bo; Du, Zhi-ming

    2015-09-01

    Al-Zn-Mg-Cu alloys are the strongest aluminum alloys which have been widely used for aerospace applications. They are usually machined from the wrought state usually with a high waste percentage. To reduce waste, it is important to thixoform these alloys in near net shape. In this work, the thixoformability of a commercial high performance Al-Zn-Mg-Cu alloy 7075 was studied. A novel multistep reheating regime was developed in recrystallization and partial melting (RAP) route to obtain spheroidal semi-solid microstructures. The as-extruded 7075 alloy was fully recrystallized for a short holding time using the multistep reheating regime. Semi-solid microstructures with fine and spherical solid grains with a grain size of 40-50 μm embedded in liquid matrix were obtained. The advantage of the multistep reheating regimes over those conventional routes was also discussed. Some wheel-shaped components were thixoformed from the as-received 7075 alloy. The ultimate tensile strength, yield strength and elongation to fracture of the thixoformed component based on multistep reheating regime, are 510 MPa, 446 MPa and 17.5% respectively. These values are superior to those of the products manufactured with the conventional RAP route. As the results indicated, thixoforming could be conducted based on commercial extruded Al-Zn-Mg-Cu alloys, which has important practical significance.

  2. Theoretical insights into effects of molar ratios on stabilities, mechanical properties and detonation performance of CL-20/RDX cocrystal explosives by molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Hang, Gui-yun; Yu, Wen-li; Wang, Tao; Wang, Jin-tao; Li, Zhen

    2017-08-01

    The CL-20/RDX cocrystal models with different molar ratios were established by substitution method and molecular dynamics (MD) simulation method was applied to investigate the influences of molar ratios on mechanical properties, stabilities and detonation performance of cocrystal explosives. The crystal parameters, structures, binding energies, mechanical properties and some detonation parameters of different cocrystal explosives were got and compared. The results illustrate that the molar ratio has a direct influence on properties of cocrystal explosive and each of the cocrystal model holds different mechanical properties, binding energies and detonation parameters. The mechanical properties of CL-20/RDX cocrystal explosive can be effectively improved and the cocrystal model with molar ratio in 1:1 has the best mechanical properties. Besides, it has the highest binding energy, so the stability and compatibility is the best. The detonation parameters show that the cocrystal explosive has better detonation performance than RDX. In a word, the cocrystal explosive with molar ratio in 1:1 has the best mechanical properties, highest binding energy and excellent energy density and detonation performance, it is quite promising and can satisfy the requirements of high energy density compounds (HEDC). This paper could offer some theoretical instructions and novel insights for the CL-20 cocrystal explosive designing.

  3. 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...

  4. 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...

  5. 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.

  6. Mechanical Properties of Cells

    NASA Technical Reports Server (NTRS)

    Bradley, Robert; Becerril, Joseph; Jeevarajan, Anthony

    2007-01-01

    Many physiologic and pathologic processes alter the biomechanical properties of the tissue they affect, and these changes may be manifest at the single cell level. The normal and abnormal mechanical properties of a given cell type can be established with the aid of an atomic force microscope (AFM), nonetheless, consistency in the area of the tip has been a mayor limitation of using the AFM for quantitative measurements of mechanical properties. This project attempts to overcome this limitation by using materials with a known elastic modulus, which resembles the one of the cell, to create force-deformation curves to calculate the area of indentation by means of Hooke s Law (sigma = E(epsilon)), which states that stress (sigma) is proportional to the strain (epsilon) where the constant of proportionality, E, is called the Young s modulus, also referred as the elastic modulus. Hook s Law can be rearranged to find the area of indentation (Area= Force/ E(epsilon)), where the indentation force is defined by the means of the added mass spring calibration method.

  7. Mechanical Properties of Cells

    NASA Technical Reports Server (NTRS)

    Bradley, Robert; Becerril, Joseph; Jeevarajan, Anthony

    2007-01-01

    Many physiologic and pathologic processes alter the biomechanical properties of the tissue they affect, and these changes may be manifest at the single cell level. The normal and abnormal mechanical properties of a given cell type can be established with the aid of an atomic force microscope (AFM), nonetheless, consistency in the area of the tip has been a mayor limitation of using the AFM for quantitative measurements of mechanical properties. This project attempts to overcome this limitation by using materials with a known elastic modulus, which resembles the one of the cell, to create force-deformation curves to calculate the area of indentation by means of Hooke s Law (sigma = E(epsilon)), which states that stress (sigma) is proportional to the strain (epsilon) where the constant of proportionality, E, is called the Young s modulus, also referred as the elastic modulus. Hook s Law can be rearranged to find the area of indentation (Area= Force/ E(epsilon)), where the indentation force is defined by the means of the added mass spring calibration method.

  8. 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

  9. Mechanical properties of graphene papers

    NASA Astrophysics Data System (ADS)

    Liu, Yilun; Xie, Bo; Zhang, Zhong; Zheng, Quanshui; Xu, Zhiping

    2012-04-01

    Graphene-based paper materials attract particular interests recently owing to their outstanding properties, the key of which is their layer-by-layer hierarchical structures similar to many biological materials such as bone, teeth and nacre, combining intralayer strong sp2 bonds and interlayer crosslinks for efficient load transfer. Here we firstly study the mechanical properties of various interlayer and intralayer crosslinks through first-principles calculations, and then perform continuum model analysis for the overall mechanical properties of graphene-based paper materials. We find that there is a characteristic length scale l0, defined as √{Dh0/4G}, where D is the stiffness of the graphene sheet, h0 and G are height of interlayer crosslink and shear modulus respectively. When the size of the graphene sheets exceeds 3l0, the tension-shear (TS) chain model, which is widely used for nanocomposites, fails to predict the overall mechanical properties of the graphene-based papers. Instead we proposed here a deformable tension-shear (DTS) model by considering elastic deformation of graphene sheets, also the interlayer and intralayer crosslinks. The DTS is then applied to predict the mechanical properties of graphene papers under tensile loading. According to the results we thus obtain, optimal design strategies are proposed for graphene papers with ultrahigh stiffness, strength and toughness.

  10. Effect of dietary boron on growth performance, calcium and phosphorus metabolism, and bone mechanical properties in growing barrows.

    PubMed

    Armstrong, T A; Spears, J W

    2001-12-01

    An experiment was conducted to evaluate the effects of dietary boron (B) on growth performance, bone mechanical properties, and calcium (Ca) and phosphorus (P) metabolism in pigs. Thirty-six barrows were weaned at approximately 21 d of age and randomly assigned to receive one of three dietary treatments. Treatments consisted of 1) low-B basal diet (control), 2) basal + 5 mg B/kg diet, and 3) basal + 15 mg B/kg diet. Boron was supplemented as sodium borate. Barrows remained on their respective experimental diets throughout the nursery (35 d) and growing (30 d) phases of production. Blood samples were obtained from each barrow at the end of each phase. Following the 30-d growing period, eight barrows per treatment were transferred to stainless steel metabolism crates. Barrows had an adjustment period of 7 d, followed by a 7-d total collection of urine and feces. All barrows were fed at 90% of the previous ad libitum grower intake of the control animals during the adjustment and collection periods. At the end of the 7-d collection period, barrows were killed and femurs and fibulas were harvested for the assessment of bone mechanical properties. During the nursery phase, ADG and ADFI were increased (P < 0.05) by B supplementation. Boron did not affect (P = 0.34) feed efficiency during the nursery phase. During the growing phase, ADG and ADFI were increased (P < 0.05) by B supplementation. Boron did not affect (P = 0.97) feed efficiency during the growing phase. Boron did not affect (P = 0.44) bone ash percentage, but B supplementation increased (P < 0.05) bone ash P. Ultimate shear force of the fibula was increased (P < 0.05) in barrows supplemented with 15 mg B/kg diet compared to barrows fed diets supplemented with 5 mg B/kg diet. Apparent absorption and retention of Ca and P were not affected (P > 0.05) by dietary B. These data indicate that B supplementation to pigs can increase growth and bone strength without greatly affecting Ca and P metabolism.

  11. Dose effects of cross-linking polyethylene for total knee arthroplasty on wear performance and mechanical properties.

    PubMed

    Asano, Taiyo; Akagi, Masao; Clarke, Ian C; Masuda, Shingo; Ishii, Tsunehiro; Nakamura, Takashi

    2007-11-01

    Wear performance and mechanical properties of cross-linking polyethylene (XLPE) tibial inserts were investigated using a knee simulator, scanning electron microscopy (SEM), and a small punch test (SPT). Ultrahigh molecular weight PE made from GUR1050 resin was irradiated at doses ranging from 0 to 200 kGy and then machined into tibial inserts followed by annealing. The knee simulator was run for up to four million cycles. As the radiation dose increased from 0 to 100 kGy, the wear rate decreased dramatically, yielding 95% wear reduction at 100 kGy. The microwear features observed by SEM supported the dose-dependent wear reduction. The SPT for XLPE after the simulation test showed that, as the radiation dose increased from 0 to 200 kGy, the ultimate displacement decreased dose-dependently, while the ultimate load increased from 0 to 75 kGy and decreased from 75 to 200 kGy. The resulting toughness of the PE increased to its maximum at a dose of 50 kGy and then decreased with higher doses up to 200 kGy. PE cross-linked with radiation doses from 25 to 75 kGy had greater toughness than virgin, nonirradiated PE. However, PE irradiated with 100 kGy or more had lower toughness than virgin PE. These data suggest that a certain amount of irradiation enhances both wear performance and toughness of PE tibial inserts. Although a certain amount of cross-linking would be effective for clinical application of PE tibial inserts, an optimal radiation dose should be much smaller than that used in current XLPE in total hip arthroplasty.

  12. Nano-MgO reinforced chitosan nanocomposites for high performance packaging applications with improved mechanical, thermal and barrier properties.

    PubMed

    De Silva, R T; Mantilaka, M M M G P G; Ratnayake, S P; Amaratunga, G A J; de Silva, K M Nalin

    2017-02-10

    Chitosan nanocomposite thin films were fabricated by incorporating MgO nanoparticles to significantly improve its physical properties for potential packaging applications. A novel in-situ method was developed to synthesise spherical shaped MgO nanoparticles by heat-treating magnesium carbonate/poly(methyl methacrylate) (PMMA) composite precursor. Optimum mechanical properties of chitosan composites were yielded at 5 (w/w%) of MgO concentration, where tensile stress and elastic modulus significantly improved by 86% and 38%, respectively, compared to those of pure chitosan films. These improvements are due to the interaction of hydroxyl and amine groups of chitosan with MgO as confirmed by FTIR spectroscopy. Fracture surface morphology indicated the interplay between MgO dispersion and aggregation on the mechanical properties at different MgO concentrations. Furthermore, the chitosan/MgO nanocomposites displayed remarkable thermal stability, flame retardant properties (satisfied V0 rating according to the UL-94 standards), UV shielding and moisture barrier properties, which could certainly add value to the packaging material.

  13. 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

  14. Comparative acoustic performance and mechanical properties of silk membranes for the repair of chronic tympanic membrane perforations.

    PubMed

    Allardyce, Benjamin J; Rajkhowa, Rangam; Dilley, Rodney J; Xie, Zhigang; Campbell, Luke; Keating, Adrian; Atlas, Marcus D; von Unge, Magnus; Wang, Xungai

    2016-12-01

    The acoustic and mechanical properties of silk membranes of different thicknesses were tested to determine their suitability as a repair material for tympanic membrane perforations. Membranes of different thickness (10-100μm) were tested to determine their frequency response and their resistance to pressure loads in a simulated ear canal model. Their mechanical rigidity to pressure loads was confirmed by tensile testing. These membranes were tested alongside animal cartilage, currently the strongest available myringoplasty graft as well as paper, which is commonly used for simpler procedures. Silk membranes showed resonant frequencies within the human hearing range and a higher vibrational amplitude than cartilage, suggesting that silk may offer good acoustic energy transfer characteristics. Silk membranes were also highly resistant to simulated pressure changes in the middle ear, suggesting they can resist retraction, a common cause of graft failure resulting from chronic negative pressures in the middle ear. Part of this strength can be explained by the substantially higher modulus of silk films compared with cartilage. This allows for the production of films that are much thinner than cartilage, with superior acoustic properties, but that still provide the same level of mechanical support as thicker cartilage. Together, these in vitro results suggest that silk membranes may provide good hearing outcomes while offering similar levels of mechanical support to the reconstructed middle ear. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. 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.

  16. Inter-Batch Variation and the Effect of Casting Vacuum on Ballistic and Mechanical Properties of a High Performing Cast Composite Rocket Propellant

    DTIC Science & Technology

    2014-12-01

    Cast Composite Rocket Propellant Paul C. Smith Weapons and Combat Systems Division Defence Science and Technology Organisation DSTO-TR...Mechanical Properties of a High Performing Solid Composite Rocket Propellant Executive Summary A study was conducted to measure the...processing. 4. Conclusions The mixing and casting of three cast composite rocket propellant batches at DSTO using the same lot numbers

  17. Mechanically enhanced PES electrospun nanofiber membranes (ENMs) for microfiltration: The effects of ENM properties on membrane performance.

    PubMed

    Bae, Jiyeol; Baek, Inchan; Choi, Heechul

    2016-11-15

    The application of electrospun nanofiber membranes (ENMs) as microfilters for the process of water purification requires the substrate to possess suitable strength, permeability, and a smooth surface. Therefore, the fiber homogeneity, inter-fiber adhesion, and surface roughness of the ENMs must be carefully controlled. Concurrently, an understanding of the ENMs' rejection mechanism for contaminants is necessary for the effective application of ENMs. In this study, we demonstrate the fabrication of polyethersulfone (PES) ENMs, which are useful for water purification as water treatment membranes. An optimum fabrication condition that can significantly improve the mechanical property and surface roughness of the PES membrane is also illustrated. This technique induces the solvent remaining on the fiber's surface after the electrospinning process, and the mechanical properties and surface roughness of the membrane are improved by the solvent-induced fusion of the fiber. The fabricated PES ENMs also show higher clean water productivity. Additionally, we show that a particulate contaminant in water is mainly rejected on the ENM surface by using a water filtration test. Based on our conclusions, we suggest the appropriate ENM regeneration method and confirm that the fabricated ENMs show excellent regeneration ability.

  18. Fluid-structure interaction numerical simulation of thermal performance and mechanical property on plate-fins heat exchanger

    NASA Astrophysics Data System (ADS)

    Zhang, Lingjie; Qian, Zuoqin; Deng, Jun; Yin, Yuting

    2015-09-01

    A numerical simulation and experimental study of heat transfer, fluid flow and fins mechanical property on plate-fin heat exchanger has been presented in this paper. The methods used in this study are experiment, CFD analysis, fluid-structure interaction and finite element method. An air-oil wind tunnel is established for this experiment. The temperature difference, pressure drop, streamlines are obtained in overall model, and the heat transfer coefficient, j/ f factor, temperature and stress distribution of plate-fin body are obtained in different fin thickness and fin offset. The prediction from the CFD simulation shows reasonably good agreement with the experimental results.

  19. Mechanical properties and in vivo performance of load-bearing fiber-reinforced composite intramedullary nails with improved torsional strength.

    PubMed

    Moritz, N; Strandberg, N; Zhao, D S; Mattila, R; Paracchini, L; Vallittu, P K; Aro, H T

    2014-12-01

    Fiber-reinforced composites (FRC) could be feasible materials for fracture fixation devices if the mechanical properties of the composites are congruent with the local structural properties of bone. In a recently developed FRC implant, bisphenol A dimethacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA) resin was reinforced with unidirectional E-glass fibers. The addition of a braided glass fiber sleeving to the unidirectional fibers increased the torsional strength (99.5MPa) of the FRC implants at the expense of the flexural strength (602.0MPa). The flexural modulus was 15.3GPa. Two types of FRC intramedullary nails were prepared; first type was FRC as such, second type was FRC with a surface layer of bioactive glass (BG) granules. Experimental oblong subtrochanteric defect was created in 14 rabbits. The defect, which reduced the torsional strength of the bones by 66%, was fixed with an FRC intramedullary nail of either type. The contralateral intact femur served as the control. This model simulated surgical stabilization of bone metastasis. After 12 weeks of follow-up, the femurs were harvested and analyzed by torsional testing, micro-CT and hard tissue histology. Healed undisplaced peri-implant fractures were noticed in half of the animals irrespective of the type of FRC implant. Torsional testing showed no significant differences between the implantation groups. The torsional strength of the bones stabilized by either type of FRC implant was 83% of that of the contralateral femurs. In histological analysis, no implant debris and no adverse tissue reactions were observed. While the mechanical properties of the modified FRCs were suboptimal, the FRC intramedullary nails supported the femurs without structural failure, even in the cases of peri-implant fractures.

  20. Analytical, numerical, and experimental investigations on effective mechanical properties and performances of carbon nanotubes and nanotube based nanocomposites with novel three dimensional nanostructures

    NASA Astrophysics Data System (ADS)

    Askari, Davood

    The theoretical objectives and accomplishment of this work are the analytical and numerical investigation of material properties and mechanical behavior of carbon nanotubes (CNTs) and nanotube nanocomposites when they are subjected to various loading conditions. First, the finite element method is employed to investigate numerically the effective Young's modulus and Poisson's ratio of a single-walled CNT. Next, the effects of chirality on the effective Young's modulus and Poisson's ratio are investigated and then variations of their effective coefficient of thermal expansions and effective thermal conductivities are studied for CNTs with different structural configurations. To study the influence of small vacancy defects on mechanical properties of CNTs, finite element analyses are performed and the behavior of CNTs with various structural configurations having different types of vacancy defects is studied. It is frequently reported that nano-materials are excellent candidates as reinforcements in nanocomposites to change or enhance material properties of polymers and their nanocomposites. Second, the inclusion of nano-materials can considerably improve electrical, thermal, and mechanical properties of the bonding agent, i.e., resin. Note that, materials atomic and molecular level do not usually show isotropic behaviour, rather they have orthotropic properties. Therefore, two-phase and three-phase cylindrically orthotropic composite models consisting of different constituents with orthotropic properties are developed and introduced in this work to analytically predict the effective mechanical properties and mechanical behavior of such structures when they are subjected to various external loading conditions. To verify the analytically obtained exact solutions, finite element analyses of identical cylindrical structures are also performed and then results are compared with those obtained analytically, and excellent agreement is achieved. The third part of this

  1. Theoretical insights into the effects of molar ratios on stabilities, mechanical properties, and detonation performance of CL-20/HMX cocrystal explosives by molecular dynamics simulation.

    PubMed

    Hang, Gui-Yun; Yu, Wen-Li; Wang, Tao; Wang, Jin-Tao; Li, Zhen

    2017-01-01

    To research and estimate the effects of molar ratios on structures, stabilities, mechanical properties, and detonation properties of CL-20/HMX cocrystal explosive, the CL-20/HMX cocrystal explosive models with different molar ratios were established in Materials Studio (MS). The crystal parameters, structures, stabilities, mechanical properties, and some detonation parameters of different cocrystal explosives were obtained and compared. The molecular dynamics (MD) simulation results illustrate that the molar ratios of CL-20/HMX have a direct influence on the comprehensive performance of cocrystal explosive. The hardness and rigidity of the 1:1 cocrystal explosive was the poorest, while the plastic property and ductibility were the best, thus implying that the explosive has the best mechanical properties. Besides, it has the highest binding energy, so the stability and compatibility is the best. The cocrystal explosive has better detonation performance than HMX. In a word, the 1:1 cocrystal explosive is worth more attention and further research. This paper could offer some theoretical instructions and technological support, which could help in the design of the CL-20 cocrystal explosive.

  2. Mechanical Properties of MEMS Materials

    DTIC Science & Technology

    2004-03-01

    thermal strain for polysilicon (data points) compared with bulk silicon (Thermophysical Properties of Matter, Volume 13, Y. S. Touloukian , Editor...AFRL-IF-RS-TR-2004-76 Final Technical Report March 2004 MECHANICAL PROPERTIES OF MEMS MATERIALS Johns Hopkins University...TITLE AND SUBTITLE MECHANICAL PROPERTIES OF MEMS MATERIALS 6. AUTHOR(S) W. N. Sharpe, Jr., K. J. Hemker - Dept of Mechanical Engineering R. L

  3. Ionic supramolecular bonds preserve mechanical properties and enable synergetic performance at high humidity in water-borne, self-assembled nacre-mimetics

    NASA Astrophysics Data System (ADS)

    Das, Paramita; Walther, Andreas

    2013-09-01

    Although tremendous effort has been focused on enhancing the mechanical properties of nacre-mimetic materials, conservation of high stiffness and strength against hydration-induced decay of mechanical properties at high humidity remains a fundamental challenge in such water-borne high-performance materials. Herein, we demonstrate that ionic supramolecular bonds, introduced by infiltration of divalent Cu2+ ions, allow efficient stabilization of the mechanical properties of self-assembled water-borne nacre-mimetics based on sustainable sodium carboxymethylcellulose (Na+CMC) and natural sodium montmorillonite nanoclay (Na+MTM) against high humidity (95% RH). The mechanical properties in the highly hydrated state (Young's modulus up to 13.5 GPa and tensile strength up to 125 MPa) are in fact comparable to a range of non-crosslinked nacre-mimetic materials in the dry state. Moreover, the Cu2+-treated nacre-inspired materials display synergetic mechanical properties as found in a simultaneous improvement of stiffness, strength and toughness, as compared to the pristine material. Significant inelastic deformation takes place considering the highly reinforced state. This contrasts the typical behaviour of tight, covalent crosslinks and is suggested to originate from a sacrificial, dynamic breakage and rebinding of transient supramolecular ionic bonds. Considering easy access to a large range of ionic interactions and alteration of counter-ion charge via external stimuli, we foresee responsive and adaptive mechanical properties in highly reinforced and stiff bio-inspired bulk nanocomposites and in other bio-inspired materials, e.g. nanocellulose papers and peptide-based materials.Although tremendous effort has been focused on enhancing the mechanical properties of nacre-mimetic materials, conservation of high stiffness and strength against hydration-induced decay of mechanical properties at high humidity remains a fundamental challenge in such water-borne high-performance

  4. 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

  5. Mechanical properties of aspen

    Treesearch

    R.P.A. Johnson

    1947-01-01

    The clear wood of aspen has inherent properties of merit. Several of these properties are familiar to a large proportion of the general public, for some of the common types of matches are made of this wood. The requirements of wood for matches are exacting in that the wood must combine straightness of grain, ease of splitting, ease of working, and toughness. To meet...

  6. Hot environment effects on alloy mechanical properties

    NASA Technical Reports Server (NTRS)

    Davidson, J. M.; Aning, K.; Tien, J. K.

    1976-01-01

    Prolonged high temperature performance of structural alloys requires joint attention to both corrosion and mechanical properties, and to their possible interactions. In this interpretive review paper, we provide a systematic compaction of theories and key observations on corrosion-mechanical properties interactions, from early single crystal work in the 1930s to recent studies on superalloys in nonoxidizing, oxidizing and hot corrosive environments. Particular attention is paid to environmental effects on creep, stress rupture and fatigue properties.

  7. Correlating mechanical properties and anti-wear performance of tribofilms formed by ionic liquids, ZDDP and their combinations

    SciTech Connect

    Landauer, Alexander K.; Barnhill, William C.; Qu, Jun

    2016-03-10

    Here we examine the elasticity, hardness, and resistance-to-plastic-deformation (P/S2) measured via nanoindentation of several tribofilms and correlates these properties to friction and wear behavior. The tribofilms were generated by ball-on-plate reciprocating sliding lubricated by a base oil containing an ionic liquid, phosphonium-organophosphate or ammonium-organophosphate, zinc dialkyldithiophosphate (ZDDP), or combination of IL and ZDDP. Nanoindentation was conducted at room and elevated temperatures. While there seems little correlation between the tribofilm hardness and tribological behavior, a higher modulus generally leads to better friction and wear performance. Interestingly, a lower P/S2 ratio tends to reduce friction and improve wear protection, which is in an opposite trend as reported for bulk materials. Ultimately, this is likely attributable to the dynamic, self-healing characteristics of tribofilms.

  8. Correlating mechanical properties and anti-wear performance of tribofilms formed by ionic liquids, ZDDP and their combinations

    DOE PAGES

    Landauer, Alexander K.; Barnhill, William C.; Qu, Jun

    2016-03-10

    Here we examine the elasticity, hardness, and resistance-to-plastic-deformation (P/S2) measured via nanoindentation of several tribofilms and correlates these properties to friction and wear behavior. The tribofilms were generated by ball-on-plate reciprocating sliding lubricated by a base oil containing an ionic liquid, phosphonium-organophosphate or ammonium-organophosphate, zinc dialkyldithiophosphate (ZDDP), or combination of IL and ZDDP. Nanoindentation was conducted at room and elevated temperatures. While there seems little correlation between the tribofilm hardness and tribological behavior, a higher modulus generally leads to better friction and wear performance. Interestingly, a lower P/S2 ratio tends to reduce friction and improve wear protection, which is inmore » an opposite trend as reported for bulk materials. Ultimately, this is likely attributable to the dynamic, self-healing characteristics of tribofilms.« less

  9. Finite element analysis of effective mechanical properties, vibration and acoustic performance of auxetic chiral core sandwich structures

    NASA Astrophysics Data System (ADS)

    Joshi, Hrishikesh Ravindra

    Honeycomb cellular materials are widely used in engineering applications due to their high strength to weight ratio and controllable effective mechanical properties. The effective properties are controlled by varying the geometry of the repetitive unit cells of honeycomb structure. Sandwich panels made of honeycomb cores are beneficial in many applications including vibration isolation and sound transmission reduction. Sandwich panels with standard honeycomb core configurations have previously been studied with regards to sound transmission behavior. It has been established that the auxetic honeycomb cores, having negative in-plane Poisson's ratio, exhibit higher sound transmission loss as compared to regular honeycomb cores. In this study, the vibration and sound transmission response of novel auxetic chiral honeycomb structures (both hexa-chiral and anti-tetra chiral), have been investigated in detail using finite element analysis with two-dimensional plane elasticity elements. Chiral honeycomb structures are made up of a linear tessellation of periodic unit cell, which consists of circular nodes of radius ' r ' connected to each other by tangent ligaments of length ' L '. The distance between two adjacent circular nodes is ' R '. These geometric parameters are tailored to obtain the chiral structure with desired effective mechanical properties of in-plane Poisson's ratio, Young's modulus and shear modulus. Results show that, for both the hexa-chiral and anti-tetra-chiral configurations with same thickness, structures with smaller node radius 'r' have higher in-plane negative Poisson's ratio, effective Young's modulus, and shear modulus. The Poisson's ratio of anti-tetra-chiral structure with small node radius and thickness is found to approach the limit of -1. A steady state dynamic response of the chiral honeycomb sandwich panel subjected to uniform pressure load on the bottom face-sheet is also investigated over a frequency range of 1 Hz to 2000 Hz. It is

  10. Mechanical Properties of Axons

    NASA Astrophysics Data System (ADS)

    Bernal, Roberto; Pullarkat, Pramod A.; Melo, Francisco

    2007-07-01

    The mechanical response of PC12 neurites under tension is investigated using a microneedle technique. Elastic response, viscoelastic relaxation, and active contraction are observed. The mechanical model proposed by Dennerll et al. [J. Cell Biol. 109, 3073 (1989).JCLBA30021-952510.1083/jcb.109.6.3073], which involves three mechanical devices—a stiff spring κ coupled with a Voigt element that includes a less stiff spring k and a dashpot γ—has been improved by adding a new element to describe the main features of the contraction of axons. This element, which represents the action of molecular motors, acts in parallel with viscous forces defining a global tension response of axons T against elongation rates δ˙k. Under certain conditions, axons show a transition from a viscoelastic elongation to active contraction, suggesting the presence of a negative elongation rate sensitivity in the curve T vs δ˙k.

  11. MECHANICAL PROPERTIES OF WROUGHT TUNGSTEN

    DTIC Science & Technology

    Mechanical properties of wrought tungsten vol. II. Creep rupture test data from 1500 to 5000 F, and tensile test data from room temperature to 5000 F at various strain rates for tungsten sheet material.

  12. Graphene oxide/alginate beads as adsorbents: Influence of the load and the drying method on their physicochemical-mechanical properties and adsorptive performance.

    PubMed

    Platero, Emiliano; Fernandez, Maria Emilia; Bonelli, Pablo Ricardo; Cukierman, Ana Lea

    2017-04-01

    Graphene oxide/alginate beads were prepared from lab-synthesized graphene oxide, varying its content within the beads (0.05, 0.125, and 0.25wt.%). Ethanol-drying and lyophilization were compared as drying methods to obtain suitable adsorbents which were later tested to the removal of a model organic molecule (methylene blue). The morphological and textural properties of all the beads were characterized by scanning electron microscopy and N2 adsorption/desorption isotherms at -196°C, respectively. Limited porosity was obtained for all cases (SBET<60m(2)/g). Uniaxial compression tests were performed to assess the mechanical properties of the beads. Ethanol-dried ones exhibited higher Young's elasticity modulus (E=192kPa) than the lyophilized samples (twice at 0.25wt.% graphene oxide loading), which disclosed breakage points at lower deformation percentages. Adsorption experiments were conducted and dye adsorption isotherms were obtained for the beads with the best removal performance. The experimental data were better fitted by the Langmuir model. The highest maximum adsorption capacity (4.25mmol/g) was obtained for the lyophilized beads with the highest graphene oxide content. Mechanical properties were found to be affected also by the dye adsorption.

  13. Mechanical properties of nanophase metals

    SciTech Connect

    Siegel, R.W.; Fougere, G.E.

    1994-11-01

    Nanophase metals have grain-size dependent mechanical properties that are significantly different than those of their coarse-grained counterparts. Pure metals are much stronger and apparently less ductile than conventional ones; intermetallics are also strengthened, but they tend toward increased ductility at the smallest grain sizes. These property changes are primarily related to grain size limitations, but they are also affected by the large percentage of atoms in grain boundaries and other microstructural features. Strengthening appears to result from a limitation of dislocation activity, while increased ductility probably relates to grain boundary sliding. A brief overview of our present understanding of the mechanical properties of nanophase metals is presented.

  14. Mechanical properties of nanophase materials

    SciTech Connect

    Siegel, R.W.; Fougere, G.E.

    1993-11-01

    It has become possible in recent years to synthesize new materials under controlled conditions with constituent structures on a nanometer size scale (below 100 nm). These novel nanophase materials have grain-size dependent mechanical properties significantly different than those of their coarser-grained counterparts. For example, nanophase metals are much stronger and apparently less ductile than conventional metals, while nanophase ceramics are more ductile and more easily formed than conventional ceramics. The observed mechanical property changes are related to grain size limitations and/or the large percentage of atoms in grain boundary environments; they can also be affected by such features as flaw populations, strains and impurity levels that can result from differing synthesis and processing methods. An overview of what is presently known about the mechanical properties of nanophase materials, including both metals and ceramics, is presented. Some possible atomic mechanisms responsible for the observed behavior in these materials are considered in light of their unique structures.

  15. Plant material features responsible for bamboo's excellent mechanical performance: a comparison of tensile properties of bamboo and spruce at the tissue, fibre and cell wall levels.

    PubMed

    Wang, Xiaoqing; Keplinger, Tobias; Gierlinger, Notburga; Burgert, Ingo

    2014-12-01

    Bamboo is well known for its fast growth and excellent mechanical performance, but the underlying relationships between its structure and properties are only partially known. Since it lacks secondary thickening, bamboo cannot use adaptive growth in the same way as a tree would in order to modify the geometry of the stem and increase its moment of inertia to cope with bending stresses caused by wind loads. Consequently, mechanical adaptation can only be achieved at the tissue level, and this study aims to examine how this is achieved by comparison with a softwood tree species at the tissue, fibre and cell wall levels. The mechanical properties of single fibres and tissue slices of stems of mature moso bamboo (Phyllostachys pubescens) and spruce (Picea abies) latewood were investigated in microtensile tests. Cell parameters, cellulose microfibril angles and chemical composition were determined using light and electron microscopy, wide-angle X-ray scattering and confocal Raman microscopy. Pronounced differences in tensile stiffness and strength were found at the tissue and fibre levels, but not at the cell wall level. Thus, under tensile loads, the differing wall structures of bamboo (multilayered) and spruce (sandwich-like) appear to be of minor relevance. The superior tensile properties of bamboo fibres and fibre bundles are mainly a result of amplified cell wall formation, leading to a densely packed tissue, rather than being based on specific cell wall properties. The material optimization towards extremely compact fibres with a multi-lamellar cell wall in bamboo might be a result of a plant growth strategy that compensates for the lack of secondary thickening growth at the tissue level, which is not only favourable for the biomechanics of the plant but is also increasingly utilized in terms of engineering products made from bamboo culms. © The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For

  16. Plant material features responsible for bamboo's excellent mechanical performance: a comparison of tensile properties of bamboo and spruce at the tissue, fibre and cell wall levels

    PubMed Central

    Wang, Xiaoqing; Keplinger, Tobias; Gierlinger, Notburga; Burgert, Ingo

    2014-01-01

    Background and Aims Bamboo is well known for its fast growth and excellent mechanical performance, but the underlying relationships between its structure and properties are only partially known. Since it lacks secondary thickening, bamboo cannot use adaptive growth in the same way as a tree would in order to modify the geometry of the stem and increase its moment of inertia to cope with bending stresses caused by wind loads. Consequently, mechanical adaptation can only be achieved at the tissue level, and this study aims to examine how this is achieved by comparison with a softwood tree species at the tissue, fibre and cell wall levels. Methods The mechanical properties of single fibres and tissue slices of stems of mature moso bamboo (Phyllostachys pubescens) and spruce (Picea abies) latewood were investigated in microtensile tests. Cell parameters, cellulose microfibril angles and chemical composition were determined using light and electron microscopy, wide-angle X-ray scattering and confocal Raman microscopy. Key Results Pronounced differences in tensile stiffness and strength were found at the tissue and fibre levels, but not at the cell wall level. Thus, under tensile loads, the differing wall structures of bamboo (multilayered) and spruce (sandwich-like) appear to be of minor relevance. Conclusions The superior tensile properties of bamboo fibres and fibre bundles are mainly a result of amplified cell wall formation, leading to a densely packed tissue, rather than being based on specific cell wall properties. The material optimization towards extremely compact fibres with a multi-lamellar cell wall in bamboo might be a result of a plant growth strategy that compensates for the lack of secondary thickening growth at the tissue level, which is not only favourable for the biomechanics of the plant but is also increasingly utilized in terms of engineering products made from bamboo culms. PMID:25180290

  17. Material Performance and Animal Clinical Studies on Performance-Optimized Hwangtoh Mixed Mortar and Concrete to Evaluate Their Mechanical Properties and Health Benefits.

    PubMed

    Koo, Bon-Min; Kim, Jang-Ho Jay; Kim, Tae-Kyun; Kim, Byung-Yun

    2015-09-17

    In this study, the amount of cement used in a concrete mix is minimized to reduce the toxic effects on users by adjusting the concrete mixture contents. The reduction of cement is achieved by using various admixtures (ground granulated blast-furnace slag, flyash, ordinary Portland cement, and activated Hwangtoh powder). To apply the mix to construction, material property tests such as compressive strength, slump, and pH are performed. Preliminary experimental results showed that the Hwangtoh concrete could be used as a healthy construction material. Also, the health issues and effects of Hwangtoh mortar are quantitatively evaluated through an animal clinical test. Mice are placed in Hwangtoh mortar and cement mortar cages to record their activity. For the test, five cages are made with Hwangtoh and ordinary Portland cement mortar floors, using Hwangtoh powder replacement ratios of 20%, 40%, 60%, and 80% of the normal cement mortar mixing ratio, and two cages are made with Hwangtoh mortar living quarters. The activity parameter measurements included weight, food intake, water intake, residential space selection, breeding activity, and aggression. The study results can be used to evaluate the benefits of using Hwangtoh as a cement replacing admixture for lifestyle, health and sustainability.

  18. Material Performance and Animal Clinical Studies on Performance-Optimized Hwangtoh Mixed Mortar and Concrete to Evaluate Their Mechanical Properties and Health Benefits

    PubMed Central

    Koo, Bon-Min; Kim, Jang-Ho Jay; Kim, Tae-Kyun; Kim, Byung-Yun

    2015-01-01

    In this study, the amount of cement used in a concrete mix is minimized to reduce the toxic effects on users by adjusting the concrete mixture contents. The reduction of cement is achieved by using various admixtures (ground granulated blast-furnace slag, flyash, ordinary Portland cement, and activated Hwangtoh powder). To apply the mix to construction, material property tests such as compressive strength, slump, and pH are performed. Preliminary experimental results showed that the Hwangtoh concrete could be used as a healthy construction material. Also, the health issues and effects of Hwangtoh mortar are quantitatively evaluated through an animal clinical test. Mice are placed in Hwangtoh mortar and cement mortar cages to record their activity. For the test, five cages are made with Hwangtoh and ordinary Portland cement mortar floors, using Hwangtoh powder replacement ratios of 20%, 40%, 60%, and 80% of the normal cement mortar mixing ratio, and two cages are made with Hwangtoh mortar living quarters. The activity parameter measurements included weight, food intake, water intake, residential space selection, breeding activity, and aggression. The study results can be used to evaluate the benefits of using Hwangtoh as a cement replacing admixture for lifestyle, health and sustainability. PMID:28793563

  19. The Processing and Mechanical Properties of High Temperature/High Performance Composites. Book 4, Section 3: Flow and Creep Strength

    DTIC Science & Technology

    1989-10-15

    Strength and Ductility of an 1,.. J. Yang A1 Alloy Reinforced with SiC¢Partlculates C. Cady M.S. Hu F . Zok R. Mehrabian A.G. Evans 51. Some Aspects of...Materials Containing C.L. Horn a Cubic Array of Agid Spheres- R.M. McMeeking 57. The Influence of Pressure on Damage F . Zok Evoluticn and Fracture in...Metal-Matrix J.D. Embury Composites M.F. Ashby 0. Richmond 58. Fracture Mechanism Maps in Stress Space, D. Teirlinck F . Zok J.D. Embury M.F. Ashby

  20. Mechanical properties of active polyacrylonitrile gels

    NASA Astrophysics Data System (ADS)

    Marra, Steven P.; Ramesh, Kaliat T.; Douglas, Andrew S.

    1999-05-01

    The ability of some polymeric gels to shrink and swell with changes in their environment makes them of interest in many applications such as artificial muscles and drug delivery systems. While much work has been done to study the behavior and properties of these gels, little information is available regarding the full constitutive description of the mechanical and actuation properties. This work is focused on developing constitutive descriptions of the mechanical properties of such gels, and to determine how these properties change due to changes in the environment. Since these gels can undergo finite elastic deformations, uniaxial tests do not provide sufficient property information and a combination of loading conditions must be used. A biaxial testing system has been developed to test thin sheets of these films, and includes the ability to monitor and change the environmental conditions around the specimen. Initial tests were performed on latex to determine the quality of the testing apparatus. Preliminary results on a polyacrylonitrile gel are presented.

  1. [Mechanical properties of thermoplastic materials].

    PubMed

    Zhang, Ning; Bai, Yu-xing; Zhang, Kun-ya

    2010-09-14

    To investigate the mechanical properties of various brands of thermoplastic materials under different test conditions so as to analyze their influencing factors so as to provide a reference for improving the effect of invisible orthodontics. Three brands of thermoplastic materials, DR, Biolon and Erkodent, were selected. They were tested by Instron testing machine to measure their maximal stress and modulus under different processing modes, including pre-thermoforming, post-thermoforming and dipped in artificial saliva for two weeks after thermoforming. The data were analyzed by SPSS 11.5. Analyzed the mechanical properties change-trend under each test condition. The modulus (MPa) and maximum stress (MPa) of control group were significantly higher than those of thermoforming group (DR: 9.63±0.68 vs 7.85±0.61, 267±8 vs 199±6; Erkodent: 8.28±0.28 vs 7.59±0.45, 226±6 vs 199±6; Biolon: 8.85±0.41 vs 7.07±0.22, 237±6 vs 169±7, all P<0.05). The modulus (MPa) and maximum stress (MPa) of thermoforming group were significantly lower than those of saliva immersion group (DR: 7.85±0.61 vs 9.14±0.41, 199±6 vs 243±7; Erkodent: 7.59 ± 0.45 vs 8.38±0.29, 199±6 vs 212±7; Biolon: 7.07±0.22 vs 7.90±0.31, 169±7 vs 197±5, all P<0.05). The different brands of thermoplastic materials have different mechanical properties. The different processing modes influence the mechanical properties of thermoplastic materials. The mechanical properties decrease after thermoforming and increase after saliva immersion.

  2. 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).

  3. Influence of the mechanical properties of third-generation artificial turf systems on soccer players' physiological and physical performance and their perceptions.

    PubMed

    Sánchez-Sánchez, Javier; García-Unanue, Jorge; Jiménez-Reyes, Pedro; Gallardo, Ana; Burillo, Pablo; Felipe, José Luis; Gallardo, Leonor

    2014-01-01

    The aim of this research was to evaluate the influence of the mechanical properties of artificial turf systems on soccer players' performance. A battery of perceptive physiological and physical tests were developed on four different structural systems of artificial turf (System 1: Compacted gravel sub-base without elastic layer; System 2: Compacted gravel sub-base with elastic layer; System 3: Asphalt sub-base without elastic layer; System 4: Asphalt sub-base with elastic layer). The sample was composed of 18 soccer players (22.44±1.72 years) who typically train and compete on artificial turf. The artificial turf system with less rotational traction (S3) showed higher total time in the Repeated Sprint Ability test in comparison to the systems with intermediate values (49.46±1.75 s vs 47.55±1.82 s (S1) and 47.85±1.59 s (S2); p<0.001). The performance in jumping tests (countermovement jump and squat jump) and ball kicking to goal decreased after the RSA test in all surfaces assessed (p<0.05), since the artificial turf system did not affect performance deterioration (p>0.05). The physiological load was similar in all four artificial turf systems. However, players felt more comfortable on the harder and more rigid system (S4; visual analogue scale = 70.83±14.28) than on the softer artificial turf system (S2; visual analogue scale = 54.24±19.63). The lineal regression analysis revealed a significant influence of the mechanical properties of the surface of 16.5%, 15.8% and 7.1% on the mean time of the sprint, the best sprint time and the maximum mean speed in the RSA test respectively. Results suggest a mechanical heterogeneity between the systems of artificial turf which generate differences in the physical performance and in the soccer players' perceptions.

  4. Influence of the Mechanical Properties of Third-Generation Artificial Turf Systems on Soccer Players’ Physiological and Physical Performance and Their Perceptions

    PubMed Central

    Sánchez-Sánchez, Javier; García-Unanue, Jorge; Jiménez-Reyes, Pedro; Gallardo, Ana; Burillo, Pablo; Felipe, José Luis; Gallardo, Leonor

    2014-01-01

    The aim of this research was to evaluate the influence of the mechanical properties of artificial turf systems on soccer players’ performance. A battery of perceptive physiological and physical tests were developed on four different structural systems of artificial turf (System 1: Compacted gravel sub-base without elastic layer; System 2: Compacted gravel sub-base with elastic layer; System 3: Asphalt sub-base without elastic layer; System 4: Asphalt sub-base with elastic layer). The sample was composed of 18 soccer players (22.44±1.72 years) who typically train and compete on artificial turf. The artificial turf system with less rotational traction (S3) showed higher total time in the Repeated Sprint Ability test in comparison to the systems with intermediate values (49.46±1.75 s vs 47.55±1.82 s (S1) and 47.85±1.59 s (S2); p<0.001). The performance in jumping tests (countermovement jump and squat jump) and ball kicking to goal decreased after the RSA test in all surfaces assessed (p<0.05), since the artificial turf system did not affect performance deterioration (p>0.05). The physiological load was similar in all four artificial turf systems. However, players felt more comfortable on the harder and more rigid system (S4; visual analogue scale = 70.83±14.28) than on the softer artificial turf system (S2; visual analogue scale = 54.24±19.63). The lineal regression analysis revealed a significant influence of the mechanical properties of the surface of 16.5%, 15.8% and 7.1% on the mean time of the sprint, the best sprint time and the maximum mean speed in the RSA test respectively. Results suggest a mechanical heterogeneity between the systems of artificial turf which generate differences in the physical performance and in the soccer players’ perceptions. PMID:25354188

  5. Mechanical Properties of Crystalline Silicon Carbide Nanowires.

    PubMed

    Zhang, Huan; Ding, Weiqiang; Aidun, Daryush K

    2015-02-01

    In this paper, the mechanical properties of crystalline silicon carbide nanowires, synthesized with a catalyst-free chemical vapor deposition method, were characterized with nanoscale tensile testing and mechanical resonance testing methods inside a scanning electron microscope. Tensile testing of individual silicon carbide nanowire was performed to determine the tensile properties of the material including the tensile strength, failure strain and Young's modulus. The silicon carbide nanowires were also excited to mechanical resonance in the scanning electron microscope vacuum chamber using mechanical excitation and electrical excitation methods, and the corresponding resonance frequencies were used to determine the Young's modulus of the material according to the simple beam theory. The Young's modulus values from tensile tests were in good agreement with the ones obtained from the mechanical resonance tests.

  6. Biomolecular motor modulates mechanical property of microtubule.

    PubMed

    Kabir, Arif Md Rashedul; Inoue, Daisuke; Hamano, Yoshimi; Mayama, Hiroyuki; Sada, Kazuki; Kakugo, Akira

    2014-05-12

    The microtubule (MT) is the stiffest cytoskeletal filamentous protein that takes part in a wide range of cellular activities where its mechanical property plays a crucially significant role. How a single biological entity plays multiple roles in cell has been a mystery for long time. Over the recent years, it has been known that modulation of the mechanical property of MT by different cellular agents is the key to performing manifold in vivo activities by MT. Studying the mechanical property of MT thus has been a prerequisite in understanding how MT plays such diversified in vivo roles. However, the anisotropic structure of MT has been an impediment in obtaining a precise description of the mechanical property of MT along its longitudinal and lateral directions that requires employment of distinct experimental approach and has not been demonstrated yet. In this work, we have developed an experimental system that enabled us to investigate the effect of tensile stress on MT. By using our newly developed system, (1) we have determined the Young's modulus of MT considering its deformation under applied tensile stress and (2) a new role of MT associated motor protein kinesin in modulating the mechanical property of MT was revealed for the first time. Decrease in Young's modulus of MT with the increase in interaction with kinesin suggests that kinesin has a softening effect on MT and thereby can modulate the rigidity of MT. This work will be an aid in understanding the modulation of mechanical property of MTs by MT associated proteins and might also help obtain a clear insight of the endurance and mechanical instability of MTs under applied stress.

  7. Mechanical Properties of Viral Capsids

    NASA Astrophysics Data System (ADS)

    Zandi, Roya; Reguera, David

    2005-03-01

    Viral genomes, whether they involve RNA or DNA molecules, are invariably protected by a rigid, single-protein-thick, shell referred to as ``capsid.'' Viral capsids are known to tolerate wide ranges of pH and salt conditions and to withstand internal pressures as high as 100 atms. We study the mechanical properties of viral capsids, calling explicit attention to the inhomogeneity of the shells that is inherent in their being discrete/polyhedral rather than continuous/spherical. We analyze the distribution of stress in these capsids due to isotropic internal pressure (arising, for instance, from genome confinement and/or osmotic activity), and compare the results with appropriate generalizations of classical elasticity theory. We also examine the competing mechanisms for viral shell failure, e.g., in-plane crack formation vs radial bursting. The biological consequences of the special stabilities and stress distributions of viral capsids are also discussed.

  8. Mechanical Properties of Niobium Cavities

    SciTech Connect

    Ciovati, Gianluigi; Dhakal, Pashupati; Matalevich, Joseph R.; Myneni, Ganapati Rao

    2015-09-01

    The mechanical stability of bulk Nb cavity is an important aspect to be considered in relation to cavity material, geometry and treatments. Mechanical properties of Nb are typically obtained from uniaxial tensile tests of small samples. In this contribution we report the results of measurements of the resonant frequency and local strain along the contour of single-cell cavities made of ingot and fine-grain Nb of different purity subjected to increasing uniform differential pressure, up to 6 atm. Measurements have been done on cavities subjected to different heat treatments. Good agreement between finite element analysis simulations and experimental data in the elastic regime was obtained with a single set of values of Young’s modulus and Poisson’s ratio. The experimental results indicate that the yield strength of medium-purity ingot Nb cavities is higher than that of fine-grain, high-purity Nb.

  9. Mechanical properties of metal dihydrides

    SciTech Connect

    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, $\\text{M}{{\\text{H}}_{2}}$ {$\\text{M}$ = 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.

  10. 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

  11. Mechanical properties of crosslinked polymer coatings

    NASA Technical Reports Server (NTRS)

    Csernica, Jeffrey

    1994-01-01

    The objectives of this experiment are to: fabricate and test thin films to explore relations between a polymer's structure and its mechanical properties; expose students to testing methods for hardness and impact energy that are simple to perform and which have results that are easy to comprehend; show importance of polymer properties in materials that students frequently encounter; illustrate a system which displays a tradeoff between strength and impact resistance, the combination of which would need to be optimized for a particular application; and to expose students to coatings technology and testing.

  12. Mechanical properties of thermoelectric lanthanum telluride from quantum mechanics

    NASA Astrophysics Data System (ADS)

    Li, Guodong; Aydemir, Umut; Wood, Max; Goddard, William A., III; Zhai, Pengcheng; Zhang, Qingjie; Snyder, G. Jeffrey

    2017-07-01

    Lanthanum telluride (La3Te4) is an n-type high-performance thermoelectric material in the high temperature range, but its mechanical properties remain unknown. Since we want robust mechanical properties for their integration into industrial applications, we report here quantum mechanics (QM) simulations to determine the ideal strength and deformation mechanisms of La3Te4 under pure shear deformations. Among all plausible shear deformation paths, we find that shearing along the (0 0 1)/< \\text{1} 0 0> slip system has the lowest ideal shear strength of 0.99 GPa, making it the most likely slip system to be activated under pressure. We find that the long range La-Te ionic interactions play the predominant role in resisting shear deformation. To enhance the mechanical strength, we suggest improving the long ionic La-Te bond stiffness to strengthen the ionic La-Te framework in La3Te4 by a defect-engineering strategy, such as partial substitution of La by Ce or Pr having isotypic crystal structures. This work provides the fundamental information to understand the intrinsic mechanics of La3Te4.

  13. 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

  14. Mechanical performance of PPy helix tube microactuator

    NASA Astrophysics Data System (ADS)

    Bahrami Samani, Mehrdad; Spinks, Geoffrey M.; Cook, Christopher

    2004-02-01

    Conducting polymer actuators with favourable properties such as linearity, high power density and compliance are of increasing demand in micro applications. These materials generate forces over two times larger than produced by mammalian skeletal muscles. They operate to convert electro chemical energy to mechanical stress and strain. On the other hand, the application of conducting polymers is limited by the lack of a full description of the relation between four essential parameters: stress, strain, voltage and current. In this paper, polypyrrole helix tube micro actuator mechanical characteristics are investigated. The electrolyte is propylene carbonate and the dopant is TBA. PF6. The experiments are both in isotonic and isometric conditions and the input parameters are both electrical and mechanical. A dual mode force and length control and potentiostat / galvanostat are utilized for this purpose. Ultimately, the viscoelastic behaviour of the actuator is presented in this paper by a standard stress relaxation test. The effect of electrical stimulus on mechanical parameters is also explored by cyclic voltametry at different scan rates to obtain the best understanding of the actuation mechanism. The results demonstrate that the linear viscoelastic model, which performed well on conducting polymer film actuators, has to be modified to explain the mechanical behaviour of PPy helix tube fibre micro actuators. Secondly, the changes in mechanical properties of PPy need to be considered when modelling electromechanical behaviour.

  15. Mechanical Properties of Nanocrystal Supercrystals

    SciTech Connect

    Tam, Enrico; Podsiadlo, Paul; Shevchenko, Elena; Ogletree, D. Frank; Delplancke-Ogletree, Marie-Paule; Ashby, Paul D.

    2009-12-30

    Colloidal nanocrystals attract significant interest due to their potential applications in electronic, magnetic, and optical devices. Nanocrystal supercrystals (NCSCs) are particularly appealing for their well ordered structure and homogeneity. The interactions between organic ligands that passivate the inorganic nanocrystal cores critically influence their self-organization into supercrystals, By investigating the mechanical properties of supercrystals, we can directly characterize the particle-particle interactions in a well-defined geometry, and gain insight into both the self-assembly process and the potential applications of nanocrystal supercrystals. Here we report nanoindentation studies of well ordered lead-sulfide (Pbs) nanocrystal supercrystals. Their modulus and hardness were found to be similar to soft polymers at 1.7 GPa and 70 MPa respectively and the fractures toughness was 39 KPa/m1/2, revealing the extremely brittle nature of these materials.

  16. 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.

  17. Energy transfer properties and mechanisms

    SciTech Connect

    Barker, J.R.

    1992-10-20

    The overall objective of the research carried out under this program is to determine the principles of collisional energy transfer and use them in predictive models and theories. In order to accomplish this goal, energy transfer properties must be determined and then analyzed to discern the underlying principles involved. In this laboratory, the experimental determination of energy transfer parameters is based on techniques that use physical properties to monitor the amount of energy in excited molecules. These techniques differ from chemical methods, based on unimolecular reaction studies, which are susceptible to interferences from complex chemical mechanisms and other complications. The physical methods have their own weaknesses and limitations, however, and much of our effort has been directed toward gaining a better understanding of these deficiencies. Two physical techniques have been proved to be particularly useful: time-resolved infrared fluorescence (IRF) and time-dependent thermal lensing (TDTL). As described later, we will shortly begin work using resonance enhanced multiphoton ionization (REMPI) techniques to investigate energy transfer in bulbs and half collisions'' in free jets. We also have completed some experiments and model calculations which explore the approximations we previously have used in calculating infrared emission from highly excited molecules.

  18. 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.

  19. 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

  20. 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

  1. Realization and performance of cryogenic selection mechanisms

    NASA Astrophysics Data System (ADS)

    Aitink-Kroes, Gabby; Bettonvil, Felix; Kragt, Jan; Elswijk, Eddy; Tromp, Niels

    2014-07-01

    Within Infra-Red large wavelength bandwidth instruments the use of mechanisms for selection of observation modes, filters, dispersing elements, pinholes or slits is inevitable. The cryogenic operating environment poses several challenges to these cryogenic mechanisms; like differential thermal shrinkage, physical property change of materials, limited use of lubrication, high feature density, limited space etc. MATISSE the mid-infrared interferometric spectrograph and imager for ESO's VLT interferometer (VLTI) at Paranal in Chile coherently combines the light from 4 telescopes. Within the Cold Optics Bench (COB) of MATISSE two concepts of selection mechanisms can be distinguished based on the same design principles: linear selection mechanisms (sliders) and rotating selection mechanisms (wheels).Both sliders and wheels are used at a temperature of 38 Kelvin. The selection mechanisms have to provide high accuracy and repeatability. The sliders/wheels have integrated tracks that run on small, accurately located, spring loaded precision bearings. Special indents are used for selection of the slider/wheel position. For maximum accuracy/repeatability the guiding/selection system is separated from the actuation in this case a cryogenic actuator inside the cryostat. The paper discusses the detailed design of the mechanisms and the final realization for the MATISSE COB. Limited lifetime and performance tests determine accuracy, warm and cold and the reliability/wear during life of the instrument. The test results and further improvements to the mechanisms are discussed.

  2. Advanced Ceramics Property and Performance Measurements

    NASA Technical Reports Server (NTRS)

    Jenkins, Michael; Salem, Jonathan; Helfinstine, John; Quinn, George; Gonczy, Stephen

    2015-01-01

    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 committees 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 all of the standards in one volume.

  3. Mechanical properties of warped membranes

    NASA Astrophysics Data System (ADS)

    Kosmrlj, Andrej; Xiao, Kechao; Weaver, James C.; Vlassak, Joost J.; Nelson, David R.

    2014-03-01

    We explore how a frozen background metric affects the mechanical properties of solid planar membranes at zero temperature. Our focus is a special class of ``warped membranes'' with a preferred random height profile characterized by random Gaussian variables h(q) in Fourier space with zero mean and variance < | h(q) | 2 > q-m . Using statistical physics tools to treat this quenched random disorder, we find that in the linear response regime, similar to thermally fluctuating polymerized membranes, an increasing scale-dependent effective bending rigidity, while the Young and the shear moduli are reduced. Compared to flat plates of the same thickness t, the bending rigidity of warped membranes is increased by a factor hv / t while the in-plane elastic moduli are reduced by t /hv , where hv =√{< | h(x) | 2 > } describes the frozen height fluctuations. Interestingly, hv is system size dependent for warped membranes characterized with m > 2 . Numerical results show good agreement with theoretical predictions, which are now being tested experimentally, where warped membranes are prepared with 3D printers.

  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. Microstructure, mechanical properties and machining performance of hot-pressed Al2O3 - ZrO2 - TiC composites

    NASA Astrophysics Data System (ADS)

    Grigoriev, M.; Kotelnikov, N.; Buyakova, S.; Kulkov, S.

    2016-02-01

    The effect of adding nanocrystalline ZrO2 and submicron TiC to ultrafine Al2O3 on mechanical properties and the microstructure of the composites developed by hot pressing was investigated. It was shown that by means of hot pressing in an argon atmosphere at a sintering temperature of 1500 °C one can obtain the composites Al2O3 - ZrO2 - TiC with a fine structure and minimal porosity. It has been shown that in material a multi-scale hierarchical structure is formed, which possesses high physical and mechanical properties: the hardness and fracture toughness was 21.5 GPa and 5.2 MPa*m1/2 respectively, the modulus of elasticity was 500 GPa and bending strength was 390 MPa. Tests on composites’ cutting properties were carried out on interrupted cutting of hardened steel. All samples had wear of the cutting edge in the form of chips of the grain rear working surface of the tool, but the cutting tool which was made by Al2O3 - 10% ZrO2 - 10% TiC had a minimum width of wear.

  6. Design of monoliths through their mechanical properties.

    PubMed

    Podgornik, Aleš; Savnik, Aleš; Jančar, Janez; Krajnc, Nika Lendero

    2014-03-14

    Chromatographic monoliths have several interesting properties making them attractive supports for analytics but also for purification, especially of large biomolecules and bioassemblies. Although many of monolith features were thoroughly investigated, there is no data available to predict how monolith mechanical properties affect its chromatographic performance. In this work, we investigated the effect of porosity, pore size and chemical modification on methacrylate monolith compression modulus. While a linear correlation between pore size and compression modulus was found, the effect of porosity was highly exponential. Through these correlations it was concluded that chemical modification affects monolith porosity without changing the monolith skeleton integrity. Mathematical model to describe the change of monolith permeability as a function of monolith compression modulus was derived and successfully validated for monoliths of different geometries and pore sizes. It enables the prediction of pressure drop increase due to monolith compressibility for any monolith structural characteristics, such as geometry, porosity, pore size or mobile phase properties like viscosity or flow rate, based solely on the data of compression modulus and structural data of non-compressed monolith. Furthermore, it enables simple determination of monolith pore size at which monolith compressibility is the smallest and the most robust performance is expected. Data of monolith compression modulus in combination with developed mathematical model can therefore be used for the prediction of monolith permeability during its implementation but also to accelerate the design of novel chromatographic monoliths with desired hydrodynamic properties for particular application.

  7. Research on mechanical properties of corn stalk

    NASA Astrophysics Data System (ADS)

    Zhang, Kaifei; He, Yujing; Zhang, Hongmei; Li, He

    2017-03-01

    Many domestic scholars have studied on straw utilization from lodging resistance, by breeding agricultural experts to optimization parameters, which selected by agricultural mechanical experts and efficient utilization after the harvest crush. Therefore, the study of the mechanical properties of corn stalks has great prospects. It can provide the basis for the design of agricultural machinery and comprehensive utilization of straw that study the relationship between the properties of the corn stalk and the mechanical properties. In this paper, the radial compression and bending mechanical properties of corn stalk was conducted by universal material testing machine, which contributes to the increase of corn crop and provides basis for the development of equipment.

  8. Mechanical properties of CuNi films

    SciTech Connect

    Brueckner, W.; Macionczyk, F.; Reiss, G. |

    1997-05-01

    CuNi alloys are widely used for precision resistors and thermocouples. Recently, they have been applied to low resistance thin film components. The mechanical properties of resistive CuNi films sputtered on both silicon wafers and flexible Kapton foils are important for reliability and lifetime of resistors. Studies of stress-temperature dependence and stress relaxation, stress-strain measurements and scanning scratch tests were performed to investigate film stresses, elastic properties, plastic flow, stress for crack initiation and film adhesion. The growth and annealing stresses were found to be tensile and can be seen as the reason for resistance degradation by stress relaxation due to plastic flow. The strains for crack initiation of 0.2% to 0.7% depending on film thickness and annealing restrict the application in resistors on flexible substrates. The film adhesion can be improved by a NiCr base-layer.

  9. 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

  10. Mechanisms to improve the mechanical performance of surgical gloves

    NASA Astrophysics Data System (ADS)

    Watkins, Michelle Hoyt

    1997-11-01

    The use of gloves as a barrier to cross infection in the medical industry has increased substantially due to the heightened awareness of viral transmission, especially the human immunodeficiency virus and the hepatitis B virus. The glove must allow for tactile sensation, comfort and long use times, while providing equally critical mechanical performance. The majority of surgical gloves are made of natural rubber latex which do not give a critical level of cut-resistance or puncture-resistance. Natural rubber latex gloves are also known to cause latex allergy with hypersensitivity reactions ranging from mild skin rashes to more severe bronchial asthma, anaphylactic reactions, and even death. It has been postulated natural rubber latex (NRL) proteins cause these allergic reactions. The research that has been conducted comprises two approaches that have been explored for improving the cut-resistance of surgical gloves. The first method involves an integral fiber-latex structure that possesses the combination of high reversible extensibility, barrier performance and retention of tactile sense. Improvement in mechanical properties in excess of 85% has been achieved as well as an improvement in cut-resistance. The second method involves the incorporation of a low concentration of ultra high molecular weight (UHMW) polyacrylamide. Although the initial premise for using a UHMW polymer was that it would bridge the latex compound particulates to improve strength, an entirely different mechanism for the enhancement of strength was explored through a parallel investigation of the release of proteins from cured natural rubber. However, no mechanism was conclusively identified. To address the allergy aspects of NRL, a thorough examination of the release of naturally-occurring latex proteins from cured natural rubber latex glove material was conducted in order to identify mechanisms for eliminating and/or reducing the potential allergens. The initial study examined the release of

  11. 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.

  12. 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.

  13. Influence of liquid lubricant properties on their performance

    NASA Technical Reports Server (NTRS)

    Wedeven, V.

    1972-01-01

    The influence of lubricant properties on performance is considered in connection with various mechanisms of lubrication. The effects of temperature and pressure on viscosity, which is important in hydrodynamic and elastohydrodynamic lubrication, is presented using a correlation postulated by Roelands. Under elastohydrodynamic conditions it is important to distinguish between the influence of lubricant properties within the inlet region and the Hertz region since each performs different functions. The role of lubricant transport properties such as surface tension is considered in connection with lubricant starvation. Since the lubrication of practical surfaces usually involves boundary as well as hydrodynamic mechanisms, both the chemical and physical properties significantly influence the lubricant's performance.

  14. The spectroscopic properties of Er(3+)-doped TeO(2)-Nb(2)O(5) glasses with high mechanical strength performance.

    PubMed

    Dai, Shixun; Wu, Jialu; Zhang, Junjie; Wang, Guonian; Jiang, Zhonghong

    2005-11-01

    (100-x)TeO(2)-xNb(2)O(5) (x=5-20) niobic tellurite glasses doped with 0.5 mol.% Er(2)O(3) were synthesized, and their thermal, mechanical, and spectroscopic properties were measured and compared to the properties of the typical 75TeO(2)-20ZnO-5Na(2)O (TZN) tellurite glass. The refractive index (n(d)), density (rho), and glass transition temperature (T(g)) of bulk glasses increase with the Nb(2)O(5) content. The Vickers microhardness (H(v)) of bulk glass in niobic tellurite glasses also increases with the Nb(2)O(5) content. The values (2.5-3.2GPa) of H(v) in the niobic tellurite glasses are 47-88% larger than that (1.7GPa) in TZN glass. The effect of Nb(2)O(5) content on absorption spectra, the Judd-Ofelt parameters Omega(t) (t=2, 4, 6), fluorescence spectra and the lifetimes of Er(3+):I(13/2) level were also investigated, and the stimulated emission cross-section was calculated from McCumber theory. With increasing Nb(2)O(5) content in the glass composition, the Omega(t) (t=2, 4, 6) parameters, fluorescence full width at half maximum (FWHM) of I(13/2) of Er(3+) increase, while the (4)I(13/2) lifetimes of Er(3+) decreases. Compared with TZN glass, the gain bandwidth properties of Er(3+)-doped TeO(2)-Nb(2)O(5) glass is much larger than in tellurite glass based TeO(2)-ZnO-Na(2)O system, bismush-based glass, germanate, and silicate glasses, which indicates that TeO(2)-Nb(2)O(5) glasses are better choice as a practical available host material for broadband Er(3+)-doped amplifier.

  15. Braiding Simulation and Prediction of Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Pickett, Anthony K.; Sirtautas, Justas; Erber, Andreas

    2009-12-01

    Rotary braiding is a cost effective method to manufacture near net shaped preforms that generally have a closed section and may have an arbitrary shape if braiding is performed over a shaped mandrel. The reinforcement architecture can be varied by the number and spacing of active bobbins, and by the speeds used to ‘take-up’ the braid and move the circumferential bobbins. Analytical methods are available that can reliably predict yarn paths and the final braid meso-structure for simple regular sections, and further analytical methods have been proposed to estimate composite braid elastic mechanical properties. A full simulation chain using the explicit Finite Element (FE) technique is presented for composite braid manufacture and mechanical stiffness prediction of the final composite. First simulation of the braiding process provides detailed information on yarns paths and braid meso-structure, from which Representative Volume Elements (RVE) of the braid may be constructed for analysis of stiffness properties. The techniques are general and can be applied to any braid geometry. A specific problem of meshing the yarn structure and interspersed resin volumes is overcome using conventional solid elements for the yarns and Smooth Particle Hydrodynamics for the resin, with link element to join the two constituents. Details of the background theory, braid simulation methods, meso- model analysis and validation again analytical and test measurements are presented.

  16. Manufacturing and mechanical properties of calcium phosphate biomaterials

    NASA Astrophysics Data System (ADS)

    Laasri, S.; Taha, M.; Hlil, E. K.; Laghzizil, A.; Hajjaji, A.

    2012-10-01

    In this study, the influence of powder manufacturing and sintering temperature on densification, microstructure and mechanical properties of dense β-tricalcium phosphate (β-TCP) bioceramic has been studied. Densification results show that the β-TCP can be sintered at 1160 °C for 3 hours to have good density and high performance mechanic properties (Vickers hardness, toughness and Young's modulus). X-ray diffraction and SEM microscopy are used to check the microstructure changes during the sintering temperature. The used processing of β-TCP ceramic improved its densification, microstructure homogeneity and mechanical properties.

  17. 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

  18. 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.

  19. 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.

  20. Mechanical properties of 3D ceramic nanolattices

    NASA Astrophysics Data System (ADS)

    Meza, Lucas

    Developments in advanced nanoscale fabrication techniques have allowed for the creation of 3-dimensional hierarchical structural meta-materials that can be designed with arbitrary geometry. These structures can be made on length scales spanning multiple orders of magnitude, from tens of nanometers to hundreds of microns. The smallest features are controllable on length scales where materials have been shown to exhibit size effects in their mechanical properties. Combining novel nanoscale mechanical properties with a 3-dimensional architecture enables the creation of new classes of materials with tunable and unprecedented mechanical properties. We present the fabrication and mechanical deformation of hollow tube alumina nanolattices that were fabricated using two-photon lithography direct laser writing (DLW), atomic layer deposition (ALD), and oxygen plasma etching. Nanolattices were designed in a number of different geometries including octet-truss, octahedron, and 3D Kagome. Additionally, a number of structural parameters were varied including tube wall thickness (t) , tube major axis (a) , and unit cell size (L) . The resulting nanolattices had a range of densities from ρ = 4 to 250 mg/cm3. Uniaxial compression and cyclic loading tests were performed on the nanolattices to obtain the yield strength and modulus. In these tests, a marked change in the deformation response was observed when the wall thickness was reduced below 20nm; thick-walled nanolattices (t>20nm) underwent catastrophic, brittle failure, which transitioned to a gradual, ductile-like deformation as wall thickness was reduced. Thick-walled nanolattices also exhibited no recovery after compression, while thin-walled structures demonstrated notable recovery, with some recovering by 98% after compression to 50% strain and by 80% when compressed to 90% strain. Across all geometries, unit cell sizes, and wall thicknesses, we found a consistent power law relation between strength and modulus with

  1. Mechanical properties of low tantalum alloys

    NASA Technical Reports Server (NTRS)

    Kortovich, C. S.

    1982-01-01

    The mechanical property behavior of equiaxed cast B-1900 + Hf alloy as a function of tantalum content was studied. Tensile and stress rupture characterization was conducted on cast to size test bars containing tantalum at the 4.3% (standard level), 2.2% and 0% levels. Casting parameters were selected to duplicate conditions used to prepare test specimens for master metal heat qualification. The mechanical property results as well as results of microstructural/phase analysis of failed test bars are presented.

  2. Mechanical deformation mechanisms and properties of amyloid fibrils.

    PubMed

    Choi, Bumjoon; Yoon, Gwonchan; Lee, Sang Woo; Eom, Kilho

    2015-01-14

    Amyloid fibrils have recently received attention due to their remarkable mechanical properties, which are highly correlated with their biological functions. We have studied the mechanical deformation mechanisms and properties of amyloid fibrils as a function of their length scales by using atomistic simulations. It is shown that the length of amyloid fibrils plays a role in their deformation and fracture mechanisms in such a way that the competition between shear and bending deformations is highly dependent on the fibril length, and that as the fibril length increases, so does the bending strength of the fibril while its shear strength decreases. The dependence of rupture force for amyloid fibrils on their length is elucidated using the Bell model, which suggests that the rupture force of the fibril is determined from the hydrogen bond rupture mechanism that critically depends on the fibril length. We have measured the toughness of amyloid fibrils, which is shown to depend on the fibril length. In particular, the toughness of the fibril with its length of ∼3 nm is estimated to be ∼30 kcal mol(-1) nm(-3), comparable to that of a spider silk crystal with its length of ∼2 nm. Moreover, we have shown the important effect of the pulling rate on the mechanical deformation mechanisms and properties of amyloid fibril. It is found that as the pulling rate increases, so does the contribution of the shear effect to the elastic deformation of the amyloid fibril with its length of <10 nm. However, we found that the deformation mechanism of the amyloid fibril with its length of >15 nm is almost independent of the pulling rate. Our study sheds light on the role of the length scale of amyloid fibrils and the pulling rate in their mechanical behaviors and properties, which may provide insights into how the excellent mechanical properties of protein fibrils can be determined.

  3. Effects of thermal aging on mechanical performance of paper

    Treesearch

    B.T. Hotle; J.M. Considine; M.J. Wald; R.E. Rowlands; K.T. Turner

    2008-01-01

    A missing element of paper aging research is a description of mechanical performance with aging. Tensile strength cannot be predicted directly from DP measurements, and existing models do not represent the effects of aging on strength and stiffness. The primary aim of the present work is to characterize changes of mechanical properties, such as tensile response and...

  4. Mechanical Properties of the Seismogenic Zone

    NASA Astrophysics Data System (ADS)

    Scuderi, Marco M.

    Understanding the processes that dictate the evolution of frictional strength during the seismic cycle is a central problem in characterizing the seismic potential of faults and in relating earthquake source parameters such as stress drop to recurrence interval and geologic and geodetic fault slip rates. Laboratory friction experiments provide insight into the mechanisms of fault healing, and results of these studies provide the fundamental underpinnings of the rate- and state-friction laws. Frictional healing is the mechanism(s) associated with fault restrengthening following failure, where time-, slip- and velocity-dependent processes dictate the evolution of real contact area at grain junctions within fault gouge. The objective of this work is to illuminate the micromechanics of frictional healing and the relation between mechanical and hydraulic properties of fault gouge. Four main dissertation chapters are combined with three additional collaborative works describing research on the fundamental processes that govern earthquakes and tectonic faulting. Chapter one is focused on the role of water during repetitive stick-slip frictional sliding, with particular emphasis on the grain scale mechanisms of frictional restrengthening. A micromechanical model for gouge deformation is developed, based on the interpretation of mechanical and microstructural observations. Chapter two describes the role of pore fluid pressure during earthquake nucleation and dynamic rupture. Experiments were performed on synthetic granular fault gouge under a range of hydrological boundary conditions from drained to undrained. The experiments demonstrate that when gouge layers are deformed under undrained boundary conditions, time-dependent strengthening and the magnitude of stress drop increase, when compared with drained conditions. I conclude that under undrained conditions, a series of feedback processes between pore fluid depressurization and stress enhanced pressure solution creep

  5. A comparative reliability and performance study of different stent designs in terms of mechanical properties: foreshortening, recoil, radial force, and flexibility.

    PubMed

    Kim, Dong Bin; Choi, Hyuk; Joo, Sang Min; Kim, Han Ki; Shin, Jae Hee; Hwang, Min Ho; Choi, Jaesoon; Kim, Dong-Gon; Lee, Kwang Ho; Lim, Chun Hak; Yoo, Sun Kook; Lee, Heung-Man; Sun, Kyung

    2013-04-01

    This study seeks to improve the mechanical performance of stents by conducting reliability performance testing and finite element method (FEM)-based simulations for coronary stents. Three commercially available stent designs and our own new design were tested to measure the factors affecting performance, specifically foreshortening, recoil, radial force, and flexibility. The stents used in the present experiments were 3 mm in working diameter and 18 mm of working length. The results of the experiments indicate that the foreshortening of stents A, B, C, and our new design, D, was equivalent to 2.25, 0.67, 0.46, and 0.41%, respectively. The recoil of stents A, B, C, and D was 6.00, 4.35, 3.50, and 4.36%, respectively. Parallel plate radial force measurements were A, 3.72 ± 0.28 N; B, 3.81 ± 0.32 N; C, 4.35 ± 0.18 N; and D, 4.02 ± 0.24 N. Radial forces determined by applying uniform pressure in the circumferential direction were A, 28.749 ± 0.81 N; B, 32.231 ± 1.80 N; C, 34.522 ± 3.06 N; and D, 42.183 ± 2.84 N. The maximum force of crimped stent at 2.2-mm deflection was 1.01 ± 0.08 N, 0.82 ± 0.08 N, 0.92 ± 0.12 N, and 0.68 ± 0.07 N for each of stents A, B, C and D. The results of this study enabled us to identify several factors to enhance the performance of stents. In comparing these stents, we found that our design, stent D, which was designed by a collaborative team from seven universities, performed better than the commercial stents across all parameter of foreshortening, recoil, radial force, and flexibility.

  6. Mechanical properties of semiconductors and their alloys

    NASA Astrophysics Data System (ADS)

    Sher, A.; Berding, M. A.; Paxton, A. T.; Krishnamurthy, S.; Chen, A.-B.

    1992-02-01

    A wide range of subjects have been treated in this contract. We have devoted time to the development and applications of two first principles computational methods: one, the full-potential linear muffin tin orbital (FP-LMTO) method is somewhat mature and highly accurate, while the other, linear combination of atomic orbitals (LCAO), is less accurate but more flexible and is easily incorporated into the other calculations we have in place, e.g., surface Green's function methods and CPA. Tight binding has also been used. These methods have been applied to solve a host of mechanical-property problems including elastic constants, cleavage energies, sublimation energies, interactions between surface atoms relating to their surface order-disorder state and growth theory, surface segregation, bulk order-disorder theory and phase stability, the effect of dislocations on electronic transport and electro-optic properties of semiconductors, the Ni-Al intermetallic phase diagram, planar fault energies in L12 alloys, high-performance structural metal alloy design, and a contribution to understanding the Jones theory of metal alloying. Many of these subjects have been brought to publishable conclusions. Whenever possible, we have presented our detailed results in the form of preprints and reprints, with only brief summaries of the work given here. In instances where the research is incomplete, we have given somewhat longer expositions.

  7. Building unique surface structure on aramid fibers through a green layer-by-layer self-assembly technique to develop new high performance fibers with greatly improved surface activity, thermal resistance, mechanical properties and UV resistance

    NASA Astrophysics Data System (ADS)

    Zhou, Lifang; Yuan, Li; Guan, Qingbao; Gu, Aijuan; Liang, Guozheng

    2017-07-01

    Combining green preparation and high performance is becoming the direction of sustainable development of materials. How to simultaneously overcome the two bottlenecks (poor surface activity and UV resistance) of aramid fibers (AFs) while improving thermal and mechanical properties through a green process is still an interesting issue with big challenge. Herein, new AFs (BL-AFs) were prepared by alternately self-assembling SiO2 and MgAlFe layered double hydroxide (LDH) on surfaces of AFs, successively, through a green layer-by-layer (LBL) self-assembly technique without using high temperature and organic solvent. The structures and properties of BL-AFs were systematically studied, which are controllable by adjusting the number of self-assembly cycle. The new fibers with three or more self-assembly cycles have remarkably improved surface activity, thermal resistance, mechanical properties and UV resistance compared with AFs. Typically, with three self-assembly cycles, the initial degradation temperature and char yield of the new fiber (3BL-AF) are as high as 552.9 °C and 81.2%, about 92 °C and 25.2% higher than those of AF, respectively; after 168 h-UV irradiation, the retention of tensile performances of 3BL-AF fiber is as high as 91-95%, about 29-14% higher than that of AF, showing the best overall performances among all modified AFs prepared using a green technique reported so far. The origin behind the attractive performances of BL-AFs is revealed through correlating with structures of original and modified fibers. The excellent comprehensive properties of BL-AFs demonstrate that the green method provided in this study is facile and effective to completely solve the bottlenecks of aramid fibers, and developing higher performance organic fibers.

  8. Physical and mechanical properties of stony meteorites

    NASA Astrophysics Data System (ADS)

    Slyuta, E. N.

    2017-01-01

    The method for experimental research of physical and mechanical properties of stony meteorites is considered. Experimental data on the physical and mechanical properties of samples of three ordinary chondrites are reported. Ordinary chondrites are characterized by a well-defined three-dimensional (spatial) anisotropy of physical and mechanical properties, when a compression strength in one of the directions significantly exceeds that in the other two directions. A measured compression strength of ordinary chondrites is in the range from 105 to 203 MPa, while a tensile strength is in the range from 18 to 31 MPa. As follows from the available published data on the strength of carbonaceous chondrites, they are drastically different in properties from ordinary chondrites. The observed critical aerodynamic loads do not exceed a measured tensile strength value of ordinary chondrites, which is actually the upper limit restricting the maximum aerodynamic load for ordinary chondrites.

  9. Tailoring of mechanical properties of hydroformed aluminum tubes

    SciTech Connect

    Hong, Sung-tae; Lavender, Curt A.

    2007-07-06

    Tailoring of the mechanical properties of hydroformed aluminum 6063-T4 tubes to those of aluminum 6063-T6 was performed by heat treatment. Quasi-static tensile tests and a SEM analysis were conducted to evaluate the change of the mechanical properties. The experimental results of the hydroformed tubes in T4 condition (before the heat treatment) show significant variations of the mechanical properties along the length due to the different extents of work hardening by hydroforming. The experimental results of the hydroformed tubes in T6 condition (after the heat treatment) show that the precipitation hardening successfully removed the effects of the non-uniform work hardening and resulted in the uniform mechanical properties in the tube.

  10. Characterising Mechanical Properties of Braided and Woven Textile Composite Beams

    NASA Astrophysics Data System (ADS)

    Dauda, Benjamin; Oyadiji, S. Olutunde; Potluri, Prasad

    2009-02-01

    The focus of this paper is on the manufacture of textile composite beams and on the determination of their mechanical properties. This includes investigating the effects of fibre orientation on the mechanical properties of braided and woven textile composites. Composites were manufactured from nominally identical constituents and identical consolidation processes, leaving as the only variables, variations caused by the different fibre architecture of the preform. The repeatability and, hence, reliability of this approach is demonstrated. Results obtained show that fibre architecture affects composite strength and extensibility. Composites with woven preforms are practically linear up to catastrophic failure while composites with braided preforms exhibit non-linearity prior to failure. Also the mechanical properties of the textile composite beams were determined. Results show that by tailoring the braid angle and pick density of braided and woven composite performs, the mechanical properties of the composite beams can be controlled to suit end-use requirement.

  11. Assessing mechanical properties from cone indentation hardness

    NASA Astrophysics Data System (ADS)

    Dicarlo, Anthony Albert

    This dissertation investigates methods for assessing the mechanical properties of materials using hardness values obtained from cone indentations. A broad range of isotropic metallic materials was simulated using finite element analysis. In particular, the elastic and plastic bulk properties, which define the stress-strain behavior of materials that exhibit power law hardening, are studied. Other investigators have found that the Young's modulus, E, can be determined from the unloading data of a cone indentation. Therefore, the remaining properties of interest, in this study, are the yield strength, Y, and the work hardening exponent, n. Atkins and Tabor have conducted pioneering work in the area of determining the stress-strain behavior of a metallic material from cone indentation experiments. This work has been re-visited in this study using computational models implementing an expanded range of mechanical properties. Consequently, discrepancies in this prediction method were uncovered when the mechanical properties were outside of the original range studied. As a result, two new prediction methods have been developed using the data collected from the finite element simulations in conjunction with a regression technique. The first method correlates the non-dimensional hardness values, H/E, collected from five cone indentations to the non-dimensional mechanical properties, Y/E and n. The second method is similar in principle, but uses two hardness values as opposed to five. The yield strength can be estimated with a priori knowledge of E. Both of these methods are compared to the method developed by Atkins and Tabor. Although the majority of the work mentioned is focused on the macro-scale, bulk mechanical properties, there is some investigation of meso-scale cone indentations. At the meso-scale, the number of geometric dislocations is significant enough to noticeably increase the strength of a material. This length scale effect is studied for various angled cone

  12. Mechanical Properties of Continuous Fiber Reinforced Zirconium Diboride Matrix Composites

    NASA Technical Reports Server (NTRS)

    Stuffle, Kevin; Creegan, Peter; Nowell, Steven; Bull, Jeffrey D.; Rasky, Daniel J. (Technical Monitor)

    1995-01-01

    Continuous fiber reinforced zirconium diboride matrix composites, SCS-9a-(RBSiCZrB2)matrix, are being developed for leading edge, rocket nozzle and turbine engine applications. Recently, the composite materials have been characterized for tensile properties to 1250 C, the highest temperature tested. The tensile properties are fiber dominated as the matrix is microcracked on fabrication, but favorable failure characteristic are observed. Compression and shear mechanical testing results will be reported if completed. The effects of fiber volume fraction and matrix density on mechanical properties will be discussed. The target applications of the materials will be discussed. Specific testing being performed towards qualification for these applications will be included.

  13. Mechanical Properties of Continuous Fiber Reinforced Zirconium Diboride Matrix Composites

    NASA Technical Reports Server (NTRS)

    Stuffle, Kevin; Creegan, Peter; Nowell, Steven; Bull, Jeffrey D.; Rasky, Daniel J. (Technical Monitor)

    1995-01-01

    Continuous fiber reinforced zirconium diboride matrix composites, SCS-9a-(RBSiCZrB2)matrix, are being developed for leading edge, rocket nozzle and turbine engine applications. Recently, the composite materials have been characterized for tensile properties to 1250 C, the highest temperature tested. The tensile properties are fiber dominated as the matrix is microcracked on fabrication, but favorable failure characteristic are observed. Compression and shear mechanical testing results will be reported if completed. The effects of fiber volume fraction and matrix density on mechanical properties will be discussed. The target applications of the materials will be discussed. Specific testing being performed towards qualification for these applications will be included.

  14. Mechanical properties of nanoparticles: basics and applications

    NASA Astrophysics Data System (ADS)

    Guo, Dan; Xie, Guoxin; Luo, Jianbin

    2014-01-01

    The special mechanical properties of nanoparticles allow for novel applications in many fields, e.g., surface engineering, tribology and nanomanufacturing/nanofabrication. In this review, the basic physics of the relevant interfacial forces to nanoparticles and the main measuring techniques are briefly introduced first. Then, the theories and important results of the mechanical properties between nanoparticles or the nanoparticles acting on a surface, e.g., hardness, elastic modulus, adhesion and friction, as well as movement laws are surveyed. Afterwards, several of the main applications of nanoparticles as a result of their special mechanical properties, including lubricant additives, nanoparticles in nanomanufacturing and nanoparticle reinforced composite coating, are introduced. A brief summary and the future outlook are also given in the final part.

  15. Mechanical properties of septal cartilage homografts

    SciTech Connect

    Glasgold, M.J.; Kato, Y.P.; Christiansen, D.; Hauge, J.A.; Glasgold, A.I.; Silver, F.H.

    1988-10-01

    The compressive mechanical properties of untreated and chemically and physically treated nasal septum homografts were determined. Mechanical properties of control, saline-, thimerosal (Merthiolate)- and Alcide-treated specimens were similar. At high strains, the stiffness of treated cartilage ranged from 12.8 to 22.5 MPa and was unaffected by storage time. In comparison, irradiated and freeze-dried nasal septum exhibited stiffnesses of 35 and 37.5 MPa, respectively, after approximately 1 month of storage. These values of stiffness were significantly different from controls at a 0.95 confidence level. On the basis of these results, it was concluded that Alcide and Merthiolate treatment did not alter the compressive mechanical properties of cartilage and that a combination of these treatments may adequately sterilize and preserve nasal septum homografts.

  16. Physical and mechanical properties of hemp seed

    NASA Astrophysics Data System (ADS)

    Taheri-Garavand, A.; Nassiri, A.; Gharibzahedi, S.

    2012-04-01

    The current study was conducted to investigate the effect of moisture content on the post-harvest physical and mechanical properties of hemp seed in the range of 5.39 to 27.12% d.b. Results showed that the effect of moisture content on the most physical properties of the grain was significant (P<0.05). The results of mechanical tests demonstrated that the effect of loading rate on the mechanical properties of hemp seed was not significant. However, the moisture content effect on rupture force and energy was significant (P<0.01). The lowest value of rupture force was obtained at the highest loading rate (3mm min-1)and in the moisture content of 27.12% d.b. Moreover, the interaction effects of loading rate and moisture content on the rupture force and energy of hemp seed were significant (P<0.05).

  17. 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.

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

    NASA Astrophysics Data System (ADS)

    Zubayar, Ali

    moduli, and Poisson's ratios) from the numerical solutions of the RVEs undergone these three load tests. Validation of the obtained micro-scale mechanical properties will be performed using rule of mixture (ROM), 1st, and 2nd order of the mathematical model and experimental data.

  19. Stainless Steel Microstructure and Mechanical Properties Evaluation

    SciTech Connect

    Switzner, Nathan T

    2010-06-01

    A nitrogen strengthened 21-6-9 stainless steel plate was spinformed into hemispherical test shapes. A battery of laboratory tests was used to characterize the hemispheres. The laboratory tests show that near the pole (axis) of a spinformed hemisphere the yield strength is the lowest because this area endures the least “cold-work” strengthening, i.e., the least deformation. The characterization indicated that stress-relief annealing spinformed stainless steel hemispheres does not degrade mechanical properties. Stress-relief annealing reduces residual stresses while maintaining relatively high mechanical properties. Full annealing completely eliminates residual stresses, but reduces yield strength by about 30%.

  20. Mechanical Properties of Ingot Nb Cavities

    SciTech Connect

    Ciovati, Gianluigi; Dhakal, Pashupati; Kneisel, Peter; Mammosser, John; Matalevich, Joseph; Rao Myneni, Ganapati

    2014-07-01

    This contribution presents the results of measurements of the resonant frequency and of strain along the contour of a single-cell cavity made of ingot Nb subjected to increasing uniform differential pressure, up to 6 atm. The data were used to infer mechanical properties of this material after cavity fabrication, by comparison with the results from simulation calculations done with ANSYS. The objective is to provide useful information about the mechanical properties of ingot Nb cavities which can be used in the design phase of SRF cavities intended to be built with this material.

  1. 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.

  2. Mechanical properties of polygonal carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Huang, Ling; Cao, Dapeng

    2012-08-01

    A group of polygonal carbon nanotubes (P-CNTs) have been designed and their mechanical behavior was investigated by classical molecular dynamics simulations. The research aimed at exploring the effects of structure, temperature, and strain rate on the mechanical properties. The results indicate that the Young's modulus of P-CNTs is lower than those of circumcircle carbon nanotubes (C-CNT). Moreover, with an increase in the number of sides to the polygons, the Young's modulus increases and is much closer to that of C-CNT. The effects of temperature and strain rate on the mechanical properties of P-CNTs show that the higher temperature and slower strain rate result in a lower critical strain and weaker tensile strength. In addition, it was found that the critical strains of P-CNTs are dependent on the tube size. Finally, we used the transition-state theory model to predict the critical strain of P-CNTs at given experimental conditions. It is expected that this work could provide feasible means to manipulate the mechanical properties of novel P-CNTs and facilitate the mechanical application of nanostructures as potential electronic devices.A group of polygonal carbon nanotubes (P-CNTs) have been designed and their mechanical behavior was investigated by classical molecular dynamics simulations. The research aimed at exploring the effects of structure, temperature, and strain rate on the mechanical properties. The results indicate that the Young's modulus of P-CNTs is lower than those of circumcircle carbon nanotubes (C-CNT). Moreover, with an increase in the number of sides to the polygons, the Young's modulus increases and is much closer to that of C-CNT. The effects of temperature and strain rate on the mechanical properties of P-CNTs show that the higher temperature and slower strain rate result in a lower critical strain and weaker tensile strength. In addition, it was found that the critical strains of P-CNTs are dependent on the tube size. Finally, we used the

  3. Laminar Tendon Composites with Enhanced Mechanical Properties

    PubMed Central

    Alberti, Kyle A.; Sun, Jeong-Yun; Illeperuma, Widusha R.; Suo, Zhigang; Xu, Qiaobing

    2015-01-01

    Purpose A strong isotropic material that is both biocompatible and biodegradable is desired for many biomedical applications, including rotator cuff repair, tendon and ligament repair, vascular grafting, among others. Recently, we developed a technique, called “bioskiving” to create novel 2D and 3D constructs from decellularized tendon, using a combination of mechanical sectioning, and layered stacking and rolling. The unidirectionally aligned collagen nanofibers (derived from sections of decellularized tendon) offer good mechanical properties to the constructs compared with those fabricated from reconstituted collagen. Methods In this paper, we studied the effect that several variables have on the mechanical properties of structures fabricated from tendon slices, including crosslinking density and the orientation in which the fibers are stacked. Results We observed that following stacking and crosslinking, the strength of the constructs is significantly improved, with crosslinked sections having an ultimate tens ile strength over 20 times greater than non-crosslinked samples, and a modulus nearly 50 times higher. The mechanism of the mechanical failure mode of the tendon constructs with or without crosslinking was also investigated. Conclusions The strength and fiber organization, combined with the ability to introduce transversely isotropic mechanical properties makes the laminar tendon composites a biocompatiable material that may find future use in a number of biomedical and tissue engineering applications. PMID:25691802

  4. Probing cell mechanical properties with microfluidic devices

    NASA Astrophysics Data System (ADS)

    Rowat, Amy

    2012-02-01

    Exploiting flow on the micron-scale is emerging as a method to probe cell mechanical properties with 10-1000x advances in throughput over existing technologies. The mechanical properties of cells and the cell nucleus are implicated in a wide range of biological contexts: for example, the ability of white blood cells to deform is central to immune response; and malignant cells show decreased stiffness compared to benign cells. We recently developed a microfluidic device to probe cell and nucleus mechanical properties: cells are forced to deform through a narrow constrictions in response to an applied pressure; flowing cells through a series of constrictions enables us to probe the ability of hundreds of cells to deform and relax during flow. By tuning the constriction width so it is narrower than the width of the cell nucleus, we can specifically probe the effects of nuclear physical properties on whole cell deformability. We show that the nucleus is the rate-limiting step in cell passage: inducing a change in its shape to a multilobed structure results in cells that transit more quickly; increased levels of lamin A, a nuclear protein that is key for nuclear shape and mechanical stability, impairs the passage of cells through constrictions. We are currently developing a new class of microfluidic devices to simultaneously probe the deformability of hundreds of cell samples in parallel. Using the same soft lithography techniques, membranes are fabricated to have well-defined pore distribution, width, length, and tortuosity. We design the membranes to interface with a multiwell plate, enabling simultaneous measurement of hundreds of different samples. Given the wide spectrum of diseases where altered cell and nucleus mechanical properties are implicated, such a platform has great potential, for example, to screen cells based on their mechanical phenotype against a library of drugs.

  5. Mechanical properties of cervical dura mater.

    PubMed

    Mazgajczyk, Emilia; Ścigała, Krzysztof; Czyż, Marcin; Jarmundowicz, Włodzimierz; Będziński, Romuald

    2012-01-01

    The aim of the study was to determine experimentally the stress as strain function as well as the orthotropy and heterogeneity of porcine dura mater of the cervical spinal cord. Material was divided into groups based on the place of collection, considering the dorsal side and ventral side, specifying the number of cervical vertebra, and the direction of tension of the sample - longitudinal or circumferential. Experimental studies were conducted with the MTS Synergie 100 testing machine. The tensile test was performed for each sample at a speed of 2 mm/min until the sample's break. There were determined the characteristics of stress as a function of strain in particular samples. Distribution maps of the stress and strain values at the characteristic points were then drawn (the beginning and the end of the linear range of the stress-strain characteristic and the point corresponding to the complete sample damage) for each set of samples, taking account of their collection place and direction of tension. The results confirmed the orthotropy of mechanical properties of dura mater. Stress and strain differed also in the value at the height of each vertebra and exhibited diversification on the ventral side compared to dorsal one.

  6. Mechanical properties of thermal protection system materials.

    SciTech Connect

    Hardy, Robert Douglas; Bronowski, David R.; Lee, Moo Yul; Hofer, John H.

    2005-06-01

    An experimental study was conducted to measure the mechanical properties of the Thermal Protection System (TPS) materials used for the Space Shuttle. Three types of TPS materials (LI-900, LI-2200, and FRCI-12) were tested in 'in-plane' and 'out-of-plane' orientations. Four types of quasi-static mechanical tests (uniaxial tension, uniaxial compression, uniaxial strain, and shear) were performed under low (10{sup -4} to 10{sup -3}/s) and intermediate (1 to 10/s) strain rate conditions. In addition, split Hopkinson pressure bar tests were conducted to obtain the strength of the materials under a relatively higher strain rate ({approx}10{sup 2} to 10{sup 3}/s) condition. In general, TPS materials have higher strength and higher Young's modulus when tested in 'in-plane' than in 'through-the-thickness' orientation under compressive (unconfined and confined) and tensile stress conditions. In both stress conditions, the strength of the material increases as the strain rate increases. The rate of increase in LI-900 is relatively small compared to those for the other two TPS materials tested in this study. But, the Young's modulus appears to be insensitive to the different strain rates applied. The FRCI-12 material, designed to replace the heavier LI-2200, showed higher strengths under tensile and shear stress conditions. But, under a compressive stress condition, LI-2200 showed higher strength than FRCI-12. As far as the modulus is concerned, LI-2200 has higher Young's modulus both in compression and in tension. The shear modulus of FRCI-12 and LI-2200 fell in the same range.

  7. A simple auxetic tubular structure with tuneable mechanical properties

    NASA Astrophysics Data System (ADS)

    Ren, Xin; Shen, Jianhu; Ghaedizadeh, Arash; Tian, Hongqi; Xie, Yi Min

    2016-06-01

    Auxetic materials and structures are increasingly used in various fields because of their unusual properties. Auxetic tubular structures have been fabricated and studied due to their potential to be adopted as oesophageal stents where only tensile auxetic performance is required. However, studies on compressive mechanical properties of auxetic tubular structures are limited in the current literature. In this paper, we developed a simple tubular structure which exhibits auxetic behaviour in both compression and tension. This was achieved by extending a design concept recently proposed by the authors for generating 3D metallic auxetic metamaterials. Both compressive and tensile mechanical properties of the auxetic tubular structure were investigated. It was found that the methodology for generating 3D auxetic metamaterials could be effectively used to create auxetic tubular structures as well. By properly adjusting certain parameters, the mechanical properties of the designed auxetic tubular structure could be easily tuned.

  8. Lithophysal Rock Mass Mechanical Properties of the Repository Host Horizon

    SciTech Connect

    D. Rigby

    2004-11-10

    The purpose of this calculation is to develop estimates of key mechanical properties for the lithophysal rock masses of the Topopah Spring Tuff (Tpt) within the repository host horizon, including their uncertainties and spatial variability. The mechanical properties to be characterized include an elastic parameter, Young's modulus, and a strength parameter, uniaxial compressive strength. Since lithophysal porosity is used as a surrogate property to develop the distributions of the mechanical properties, an estimate of the distribution of lithophysal porosity is also developed. The resulting characterizations of rock parameters are important for supporting the subsurface design, developing the preclosure safety analysis, and assessing the postclosure performance of the repository (e.g., drift degradation and modeling of rockfall impacts on engineered barrier system components).

  9. 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

  10. High-performance reactionless scan mechanism

    NASA Technical Reports Server (NTRS)

    Williams, Ellen I.; Summers, Richard T.; Ostaszewski, Miroslaw A.

    1995-01-01

    A high-performance reactionless scan mirror mechanism was developed for space applications to provide thermal images of the Earth. The design incorporates a unique mechanical means of providing reactionless operation that also minimizes weight, mechanical resonance operation to minimize power, combined use of a single optical encoder to sense coarse and fine angular position, and a new kinematic mount of the mirror. A flex pivot hardware failure and current project status are discussed.

  11. Diesel Mechanics. Performance Objectives. Basic Course.

    ERIC Educational Resources Information Center

    Tidwell, Joseph

    Several intermediate performance objectives and corresponding criterion measures are listed for each of 12 terminal objectives for a basic diesel mechanics course. The course is designed as a two-semester (2 hour daily) course for 10th graders interested in being diesel service and repair mechanics; it would serve as the first year of a 3-year…

  12. Mechanical properties of fully hydrogenated graphene sheets

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Mirnezhad, M.; Rouhi, H.

    2015-01-01

    Graphane is a two-dimensional structure consisting of a flat monolayer graphene sheet fully covered with hydrogen atoms attached to its carbon atoms in an alternating pattern. The unique properties of graphane make it suitable for different applications. In this paper, the mechanical properties of the most stable conformer of graphane, the so-called chair-like, are extensively investigated using density functional theory (DFT) scheme within the framework of the generalized gradient approximation (GGA) and the well-known Perdew-Burke-Ernzerhof (PBE) exchange correlation. It is shown that the hydrogenation has significant influences on the mechanical properties of graphene sheet. In particular, it is found that the elastic, bulk and shear moduli and Poisson's ratio of the chair-graphane are significantly smaller than those of graphene.

  13. Mechanical properties of jennite: A theoretical and experimental study

    SciTech Connect

    Moon, Juhyuk; Yoon, Seyoon; Monteiro, Paulo J.M.

    2015-05-15

    The objective of this study is to determine the mechanical properties of jennite. To date, several hypotheses have been proposed to predict the structural properties of jennite. For the first time as reported herein, the isothermal bulk modulus of jennite was measured experimentally. Synchrotron-based high-pressure x-ray diffraction experiments were performed to observe the variation of lattice parameters under pressure. First-principles calculations were applied to compare with the experimental results and predict additional structural properties. Accurately measured isothermal bulk modulus herein (K{sub 0} = 64(2) GPa) and the statistical assessment on experimental and theoretical results suggest reliable mechanical properties of shear and Young's modulus, Poisson's ratio, and elastic tensor coefficients. Determination of these fundamental structural properties is the first step toward greater understanding of calcium–silicate–hydrate, as well as provides a sound foundation for forthcoming atomic level simulations.

  14. Mechanical Properties of Doubly Stabilized Microtubule Filaments

    PubMed Central

    Hawkins, Taviare L.; Sept, David; Mogessie, Binyam; Straube, Anne; Ross, Jennifer L.

    2013-01-01

    Microtubules are cytoskeletal filaments responsible for cell morphology and intracellular organization. Their dynamical and mechanical properties are regulated through the nucleotide state of the tubulin dimers and the binding of drugs and/or microtubule-associated proteins. Interestingly, microtubule-stabilizing factors have differential effects on microtubule mechanics, but whether stabilizers have cumulative effects on mechanics or whether one effect dominates another is not clear. This is especially important for the chemotherapeutic drug Taxol, an important anticancer agent and the only known stabilizer that reduces the rigidity of microtubules. First, we ask whether Taxol will combine additively with another stabilizer or whether one stabilizer will dominate another. We call microtubules in the presence of Taxol and another stabilizer, doubly stabilized. Second, since Taxol is often added to a number of cell types for therapeutic purposes, it is important from a biomedical perspective to understand how Taxol added to these systems affects the mechanical properties in treated cells. To address these questions, we use the method of freely fluctuating filaments with our recently developed analysis technique of bootstrapping to determine the distribution of persistence lengths of a large population of microtubules treated with different stabilizers, including Taxol, guanosine-5′ [(α, β)-methyleno] triphosphate, guanosine-5′-O-(3-thiotriphosphate), tau, and MAP4. We find that combinations of these stabilizers have novel effects on the mechanical properties of microtubules. PMID:23561528

  15. Improvement of mechanical properties of glass substrates

    NASA Astrophysics Data System (ADS)

    Karbay, Ismail Hakki Cengizhan; Budakoglu, Refika; Zayim, Esra Ozkan

    2015-12-01

    This paper aims to enhance the mechanical and optical properties of glass substrates with thin films by the sol-gel method. TiO2-SiO2 binary system and Ta2O5 were deposited on glass substrates with high transparency. Ring-on-ring flexure and scratch tests were the main mechanical characterization tests. Herein, we report that the thin films can be used to enhance the mechanical properties of the glass substrates efficiently and effectively. TiO2-SiO2 binary system shows more than two times and Ta2O5 thin films show nearly three times better ultimate strength in the ring-on-ring flexure test. Besides, Ta2O5 thin film samples show superior scratch resistance. Additionally, the finite element method was also used to check the conformity in the application of mechanical properties of composite materials. It is also worth noting that, the finite element method can be used to accurately analyze the mechanical stability of composite materials. The use of the finite element method can reduce the total number of experimental trials without losing reliability.

  16. 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

  17. Mechanical properties of doubly stabilized microtubule filaments.

    PubMed

    Hawkins, Taviare L; Sept, David; Mogessie, Binyam; Straube, Anne; Ross, Jennifer L

    2013-04-02

    Microtubules are cytoskeletal filaments responsible for cell morphology and intracellular organization. Their dynamical and mechanical properties are regulated through the nucleotide state of the tubulin dimers and the binding of drugs and/or microtubule-associated proteins. Interestingly, microtubule-stabilizing factors have differential effects on microtubule mechanics, but whether stabilizers have cumulative effects on mechanics or whether one effect dominates another is not clear. This is especially important for the chemotherapeutic drug Taxol, an important anticancer agent and the only known stabilizer that reduces the rigidity of microtubules. First, we ask whether Taxol will combine additively with another stabilizer or whether one stabilizer will dominate another. We call microtubules in the presence of Taxol and another stabilizer, doubly stabilized. Second, since Taxol is often added to a number of cell types for therapeutic purposes, it is important from a biomedical perspective to understand how Taxol added to these systems affects the mechanical properties in treated cells. To address these questions, we use the method of freely fluctuating filaments with our recently developed analysis technique of bootstrapping to determine the distribution of persistence lengths of a large population of microtubules treated with different stabilizers, including Taxol, guanosine-5' [(α, β)-methyleno] triphosphate, guanosine-5'-O-(3-thiotriphosphate), tau, and MAP4. We find that combinations of these stabilizers have novel effects on the mechanical properties of microtubules.

  18. The Processing and Mechanical Properties of High Temperature/High Performance Composites. Book 5, Section 4: Processing: Matrices and Composites. Part 1

    DTIC Science & Technology

    1989-10-15

    PROCESSING: Matrices and Composites Partlof2 89 12 21 038 SUMMARY of TABLE OF CONTENTS EXECUTIVE SUMMARY SECTION 1: COATINGS AND INTERFACES Book 1...The first section in Book 1 is concerned with the properties and structure of bimaterial interfaces and the related problem of coating decohesion and...solidification products to provide a basis for microstructural development and alloy design in high temperature intermetallics in titanium and niobium base

  19. 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.

  20. Astronaut Scott Carpenter tests balance mechanism performance

    NASA Technical Reports Server (NTRS)

    1961-01-01

    Astronaut M. Scott Carpenter's balance mechanism performance is tested by his walking on a narrow board in his bare feet. He is performing this test at the School of Aviation Medicine, Pensicola, Florida (04570); Carpenter walks a straight line by putting one foot directly in front of the other to test his balance (04571).

  1. Correlation of Cell and Substrate Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Setton, Tedhar; Levine, Joshua; Levine, Joseph; Guan, E.; Collazo, Lourdes; Ge, Shouren; Entcheva, Emilia; Rafailovich, Miriam

    2003-03-01

    The mechanical properties of neonatal rat ventricular fibroblasts plated onto elastomer surfaces were studied in vitro and correlated to the mechanical response of the substrate. In order to differentiate the response of the cells to mechanical as opposed to mechanical modifications in their environment, only the rheological properties of the substrates were modified. In the case of entangled polymers this can be accomplished either by varying the molecular weight or the thickness of polymer films spun cast onto rigid supports. Scanning lateral force microscopy, which has been shown to be an effective technique for measuring relative modulii of surfaces(1) was used to track the mechanical response of the substrates as a function of processing procedures, molecular weight, both in liquid, air, and following fibronectin incubation. The response of the living cells was then compared to that of the underlying substrate. The samples were then stained and the distribution of actin correlated to the mechanical response. 1. S. Ge et al. Phys. Rev. Lett. 11, (2000)2340

  2. 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

  3. Loss mechanisms in high-efficiency solar cells: Study of material properties and high-efficiency solar-cell performance on material composition: Project tasks

    NASA Technical Reports Server (NTRS)

    Sah, C. T.

    1985-01-01

    Loss mechanisms in high-efficiency solar cells were discussed. Fundamental limitations and practical solutions were stressed. Present cell efficiency is limited by many recombination sites: emitter, base, contacts, and oxide/silicon interface. Use of polysilicon passivation was suggested. After reduction of these losses, a 25% efficient cell could be built. A floating emitter cell design was shown that had the potential of low recombination losses.

  4. 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

  5. Elastic proteins: biological roles and mechanical properties.

    PubMed Central

    Gosline, John; Lillie, Margo; Carrington, Emily; Guerette, Paul; Ortlepp, Christine; Savage, Ken

    2002-01-01

    The term 'elastic protein' applies to many structural proteins with diverse functions and mechanical properties so there is room for confusion about its meaning. Elastic implies the property of elasticity, or the ability to deform reversibly without loss of energy; so elastic proteins should have high resilience. Another meaning for elastic is 'stretchy', or the ability to be deformed to large strains with little force. Thus, elastic proteins should have low stiffness. The combination of high resilience, large strains and low stiffness is characteristic of rubber-like proteins (e.g. resilin and elastin) that function in the storage of elastic-strain energy. Other elastic proteins play very different roles and have very different properties. Collagen fibres provide exceptional energy storage capacity but are not very stretchy. Mussel byssus threads and spider dragline silks are also elastic proteins because, in spite of their considerable strength and stiffness, they are remarkably stretchy. The combination of strength and extensibility, together with low resilience, gives these materials an impressive resistance to fracture (i.e. toughness), a property that allows mussels to survive crashing waves and spiders to build exquisite aerial filters. Given this range of properties and functions, it is probable that elastic proteins will provide a wealth of chemical structures and elastic mechanisms that can be exploited in novel structural materials through biotechnology. PMID:11911769

  6. 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.

  7. Mechanical Properties of Degraded PMR-15 Resin

    NASA Technical Reports Server (NTRS)

    Tsuji, Luis C.; McManus, Hugh L.; Bowles, Kenneth J.

    1998-01-01

    Thermo-oxidative aging produces a non-uniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hours. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and Coefficient of Thermal Expansion (CTE) of nitrogen aged specimens were measured directly. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

  8. Auxetic oesophageal stents: structure and mechanical properties.

    PubMed

    Ali, Murtaza Najabat; Busfield, James J C; Rehman, Ihtesham U

    2014-02-01

    Oesophageal cancer is the ninth leading cause of malignant cancer death and its prognosis remains poor, ranking as the sixth most frequent cause of death in the world. This research work aims to adopt an Auxetic (rotating-squares) geometry device, that had previously been examined theoretically and analysed by Grima and Evans (J Mater Sci Lett 19(17):1563-1565, 2000), to produce a novel Auxetic oesophageal stent and stent-grafts relevant to the palliative treatment of oesophageal cancer and also for the prevention of dysphagia. This paper discusses the manufacture of a small diameter Auxetic oesophageal stent and stent-graft. The oral deployment of such an Auxetic stent would be simplest if a commercial balloon dilatational catheter was used as this obviates the need for an expensive dedicated delivery system. A novel manufacturing route was employed in this research to develop both Auxetic films and Auxetic oesophageal stents, which ranged from conventional subtractive techniques to a new additive manufacturing method. Polyurethane was selected as a material for the fabrication of Auxetic films and Auxetic oesophageal stents because of its good biocompatibility and non-toxicological properties. The Auxetic films were later used for the fabrication of seamed Auxetic oesophageal stents. The flexible polyurethane tubular grafts were also attached to the inner luminal side of the seamless Auxetic oesophageal stents, in order to prevent tumour in-growth. Scanning electron microscopy was used to conduct surface morphology study by using different Auxetic specimens developed from different conventional and new additive manufacturing techniques. Tensile testing of the Auxetic films was performed to characterise their mechanical properties. The stent expansion tests of the Auxetic stents were done to analyse the longitudinal extension and radial expansion of the Auxetic stent at a range of radial pressures applied by the balloon catheter, and to also identify the pressure

  9. Influence of liquid lubricant properties on their performance.

    NASA Technical Reports Server (NTRS)

    Wedeven, V.

    1972-01-01

    The influence of lubricant properties on performance is considered in connection with various mechanisms of lubrication. The effects of temperature and pressure on viscosity, which is important in hydrodynamic and elastohydrodynamic lubrication, is presented using a correlation postulated by Roelands. Under elastohydrodynamic conditions it is important to distinguish between the influence of lubricant properties within the inlet region and the Hertz region since each performs different functions. The role of lubricant transport properties such as surface tension is considered in connection with lubricant starvation.

  10. Mechanical properties of functionalized carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zhang, Z. Q.; Liu, B.; Chen, Y. L.; Jiang, H.; Hwang, K. C.; Huang, Y.

    2008-10-01

    Carbon nanotubes (CNTs) used to reinforce polymer matrix composites are functionalized to form covalent bonds with the polymer in order to enhance the CNT/polymer interfaces. These bonds destroy the perfect atomic structures of a CNT and degrade its mechanical properties. We use atomistic simulations to study the effect of hydrogenization on the mechanical properties of single-wall carbon nanotubes. The elastic modulus of CNTs gradually decreases with the increasing functionalization (percentage of C-H bonds). However, both the strength and ductility drop sharply at a small percentage of functionalization, reflecting their sensitivity to C-H bonds. The cluster C-H bonds forming two rings leads to a significant reduction in the strength and ductility. The effect of carbonization has essentially the same effect as hydrogenization.

  11. Advanced mechanical properties of graphene paper

    NASA Astrophysics Data System (ADS)

    Ranjbartoreh, Ali R.; Wang, Bei; Shen, Xiaoping; Wang, Guoxiu

    2011-01-01

    Graphene paper (GP) has been prepared by flow-directed assembly of graphene nanosheets. The mechanical properties of as-prepared GPs were investigated by tensile, indentation, and bending tests. Heat treated GPs demonstrate superior hardness, ten times that of synthetic graphite, and two times that of carbon steel; besides, their yielding strength is significantly higher than that of carbon steel. GPs show extremely high modulus of elasticity during bending test; in the range of a few terapascal. The high strength and stiffness of GP is ascribed to the interlocking-tile microstructure of individual graphene nanosheets in the paper. These outstanding mechanical properties of GPs could lead to a wide range of engineering applications.

  12. 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.

  13. Mechanical Properties of Palm Fiber Mattress

    NASA Astrophysics Data System (ADS)

    Li, Yu-Qian; Wu, Jia-Yu; Gu, Hao-Wei; Chen, Zong-Yong; Shi, Xiao-Bing; Liao, Ting-Mao; An, Cheng; Yuan, Hong; Liu, Ren-Huai

    2016-05-01

    Palm fiber mattress is increasingly accepted by many families. This study aims at evaluating the mechanical properties of palm fiber mattress. Two experiments were conduct to investigate the Young's modulus of palm fiber mattress in three directions. In addition, finite element models were established to characterize palm fiber mattress under uniform distributed pressure. Finally, results from finite element analysis are presented to illustrate that the thick mattress will stick with human body curve perfectly, which can support vertebral column effectively.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. The effects of replacing dicalcium phosphate with Busumbu rock phosphate on performance and the mechanical properties of bone in growing chicks.

    PubMed

    Odongo, N E; Plaizier, J; van Straaten, P; McBride, B

    2002-07-01

    Three hundred, day-old broiler chicks, with an average initial weight of 41.8 +/- 1.79 g, were used in a 15-day study (10 birds per battery cage) to characterize their performance and fluorine status when dicalcium phosphate (DCP) was replaced by Busumbu rock phosphate (BRP) as the source of phosphorus in the chicks' ration. The treatments comprised a standard ration with BRP replacing 0, 25%, 50%, 75% or 100% of DCP. Replacing DCP with BRP significantly reduced the final weight of the chicks (p < 0.01), feed intake (p < 0.01), weight gains (p < 0.01) and dry matter digestibility (p < 0.05) but increased (p < 0.05) the feed-to-gain ratio. True phosphorus absorption and the percentage of phosphorus in the tibia were not affected by increasing amounts of BRP in the diet. Increasing levels of BRP in the diet linearly reduced (p < 0.01) the percentage bone ash, calcium, Ca:P ratio, ultimate breaking force, bending moment, stress, and modulus of elasticity. Leg stiffness, lameness, reduced feed intake, and a decline in general health were recorded in 10-40% of the chicks on 75% and 100% BRP, respectively. These results suggest that excessive ingestion of fluorine from the BRP caused the reduction in the chicks' performance.

  19. 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.

  20. [Bone biopsy needles: mechanical properties, needle design and specimen quality].

    PubMed

    Keulers, A; Cunha-Cruz, V C; Bruners, P; Penzkofer, T; Braunschweig, T; Schmitz-Rode, T; Mahnken, A

    2011-03-01

    To quantitatively analyze differences in mechanical properties, needle design including signs of wear, subjective handling and specimen quality of bone biopsy needles. In this study 19 different bone biopsy systems (total 38; 2 /type) were examined. With each biopsy needle five consecutive samples were obtained from vertebral bodies of swine. During puncture a force-torques sensor measured the mechanical properties and subjective handling was assessed. Before and after each biopsy the needles were investigated using a profile projector and signs of wear were recorded. Afterwards, a pathologist semi-quantitatively examined the specimen regarding sample quality. The overall evaluation considered mechanical properties, needle wear, subjective handling and sample quality. Differences were assessed for statistical significance using ANOVA and t-test. Needle diameter (p = 0.003) as well as needle design (p = 0.008) affect the mechanical properties significantly. Franseen design is significantly superior to other needle designs. Besides, length reduction recorded by the profile projector, as a quality criterion showed notable distinctions in between the needle designs. Bone biopsy needles vary significantly in performance. Needle design has an important influence on mechanical properties, handling and specimen quality. Detailed knowledge of those parameters would improve selecting the appropriate bone biopsy needle. © Georg Thieme Verlag KG Stuttgart · New York.

  1. 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

    2016-09-16

    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.

  2. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Microstructure and Corrosion Performance of Carbonitriding Layers on Cast Iron by Plasma Electrolytic Carbonitriding

    NASA Astrophysics Data System (ADS)

    Pang, Hua; Lv, Guo-Hua; Chen, Huan; Wang, Xin-Quan; Zhang, Gu-Ling; Yang, Si-Ze

    2009-08-01

    The surface carbonitriding of cast iron is investigated in an aqueous solution of acetamide and glycerin. Microstructure, chemical and phase composition and corrosion performance of the carbonitriding layers are investigated by scanning electron microscopy, energy dispersive spectroscopy and x-ray diffraction, as well as potentiodynamic polarization testing. X-ray diffraction results show that the carbonitriding coatings are composed of martensite, austenite(γ-Fe), Fe2C, Fe3C, Fe5C2, FeN and in-Fe2-3N. After the plasma electrolytic carbonitriding treatment the corrosion resistance of cast iron is clearly improved compared to the substrate, and the coatings produced at 350 V for 30s give the best corrosion resistance.

  3. Stretchable polyurethane sponge reinforced magnetorheological material with enhanced mechanical properties

    NASA Astrophysics Data System (ADS)

    Ge, Lin; Xuan, Shouhu; Liao, Guojiang; Yin, Tiantian; Gong, Xinglong

    2015-03-01

    A stretchable magnetorheological material (SMRM) consisting of micro-meter carbonyl iron (CI) particles, low cross-linking polyurethane (PU) polymer and porous PU sponge has been developed. Due to the presence of the PU sponge, the high-performance MR material can be reversibly stretched or bent, just as MR elastomers. When the CI content increases to 80 wt%, the magnetic induced modulus of the MR material can reach as high as 7.34 MPa and the corresponding relative MR effect increases to 820%. A possible strengthening mechanism of the SMRM was proposed. The attractive mechanical properties make the SMRM a promising candidate for future high-performance devices.

  4. Machining as a mechanical property test revisited

    NASA Astrophysics Data System (ADS)

    Smith, David L.

    There is much need for data on mechanical behavior of metals at high strains and strain rates. This need is dictated by modeling of processes like forming and machining, wherein the material in the deformation zone is subjected to severe deformation conditions atypical of conventional material property tests such as tension and torsion. Accurate flow stress data is an essential input for robust prediction of process outputs. Similar requirements arise from applications in high speed ballistic penetration and design of materials for armor. Since the deformation zone in cutting of metals is characterized by unique and extreme combinations of strain, strain rate and temperature, an opportunity exists for using plane-strain cutting as a mechanical property test for measuring flow properties of metals. The feasibility of using plane-strain cutting to measure flow properties of metals is revisited in the light of recent data showing controllability of the deformation conditions in chip formation by systematic variation of process input parameters. A method is outlined as to how the deformation conditions can be varied by changing the process parameters. The method is applied to cutting of commercially pure copper (FCC), iron (BCC) and zinc (HCP). Forces and chip geometries are measured, in conjunction with particle image velocimetry characterization of the deformation using high speed image sequences. The flow stresses are estimated from these measurements. The measured flow stress and its dependence on strain are shown to agree well with prior measurements of these parameters using conventional tests, and flow stress inferred from hardness characterization. The method is also demonstrated to be able to measure properties of metals that recrystallize at room temperature (zinc), wherein quasi-static tests predict much lower strength. Sources of variability and uncertainty in the application of this measurement technique are discussed. Future work in the context of further

  5. The effect of dietary calcium concentration and particle size on performance, eggshell quality, bone mechanical properties and tibia mineral contents in moulted laying hens.

    PubMed

    Cufadar, Y; Olgun, O; Yildiz, A Ö

    2011-12-01

    1. A total of 72 H&N Brown Nick laying hens, 76 weeks of age (moulted at 60 weeks of age), were randomly assigned into a 3 × 3 factorial arrangement with three limestone particle sizes and three dietary Ca concentrations (30, 36 and 42 g/kg Ca); with 8 replicates per treatments, and one hen (individual) per experimental unit. 2. Particle sizes of the limestone were: distributions smaller than 2 mm (Fine), between 2 to 5 mm (Medium), and larger than 5 mm (Large). The fine, medium and large limestone particles were all obtained from the same source, and sieve sizes used had screen sizes 2 mm and 5 mm. 3. The different concentrations of dietary Ca, particle size or interactions had no significant effect on egg production, egg weight, egg mass, feed intake or feed conversion ratio. 4. The concentrations of dietary Ca and particle sizes had no significant effect on egg breaking strength, eggshell as % by weight of whole egg or eggshell thickness. The interactions between Ca concentrations and particle sizes had a significant effect on eggshell breaking strength, but not on other parameters. 5. Different dietary particle sizes had no significant effect on the Ca, P and Mg mineral contents of eggshell. While the different concentrations of Ca in diets had a significant effect on the P content of eggshell, they had no significant effect on Ca and Mg contents. 6. Different dietary concentrations of Ca had a significant effect on shear stress, and Ca and Mg contents of tibiae, but not other parameters. Also, dietary particle sizes had a significant effect on shear stress and Ca contents of tibiae. The interaction between Ca concentrations and particle sizes had a significant effect on tibia shear force and Ca content. 7. According to the results of this study, moulted brown laying hens should be fed 36 g/kg Ca and a medium limestone particle size (2-5 mm) in the diet to maintain performance, eggshell and bone quality.

  6. Auto Mechanics. Performance Objectives. Basic Course.

    ERIC Educational Resources Information Center

    Carter, Thomas G., Sr.

    Several intermediate performance objectives and corresponding criterion measures are listed for each of 14 terminal objectives for a basic automotive mechanics course. The materials were developed for a two-semester course (2 hours daily) designed to provide training in the basic fundamentals in diagnosis and repair including cooling system and…

  7. Gasoline Engine Mechanics. Performance Objectives. Basic Course.

    ERIC Educational Resources Information Center

    Jones, Marion

    Several intermediate performance objectives and corresponding criterion measures are listed for each of five terminal objectives presented in this curriculum guide for a basic gasoline engine mechanics course at the secondary level. (For the intermediate course guide see CE 010 946.) The materials were developed for a two semester (2 hours daily)…

  8. Diesel Mechanics. Performance Objectives. Intermediate Course.

    ERIC Educational Resources Information Center

    Tidwell, Joseph

    Several intermediate performance objectives and corresponding criterion measures are listed for each of six terminal objectives for an intermediate diesel mechanics course (two semesters, 3 hours daily) designed for high school students who upon completion would be ready for an on-the-job training experience in diesel service and repair. Through…

  9. Gasoline Engine Mechanics. Performance Objectives. Intermediate Course.

    ERIC Educational Resources Information Center

    Jones, Marion

    Several intermediate performance objectives and corresponding criterion measures are listed for each of six terminal objectives presented in this curriculum guide for an intermediate gasoline engine mechanics course at the secondary level. (For the beginning course guide see CE 010 947.) The materials were developed for a two-semester (2 hour…

  10. Mechanical performance of aquatic rowing and flying.

    PubMed Central

    Walker, J A; Westneat, M W

    2000-01-01

    Aquatic flight, performed by rowing or flapping fins, wings or limbs, is a primary locomotor mechanism for many animals. We used a computer simulation to compare the mechanical performance of rowing and flapping appendages across a range of speeds. Flapping appendages proved to be more mechanically efficient than rowing appendages at all swimming speeds, suggesting that animals that frequently engage in locomotor behaviours that require energy conservation should employ a flapping stroke. The lower efficiency of rowing appendages across all speeds begs the question of why rowing occurs at all. One answer lies in the ability of rowing fins to generate more thrust than flapping fins during the power stroke. Large forces are necessary for manoeuvring behaviours such as accelerations, turning and braking, which suggests that rowing should be found in slow-swimming animals that frequently manoeuvre. The predictions of the model are supported by observed patterns of behavioural variation among rowing and flapping vertebrates. PMID:11052539

  11. Mechanical excavator performance in Yucca Mountain tuffs

    SciTech Connect

    Ozdemir, L.; Hansen, F.D.

    1991-12-31

    A research effort of four phases is in progress at the Colorado School of Mines. The overall program will evaluate the cutability of welded tuff and other lithologies likely to be excavated at Yucca Mountain in the site characterization process. Several mechanical systems are considered with emphasis given to the tunnel boring machine. The research comprises laboratory testing, linear drag bit and disc cutter tests, and potentially large-scale lab. demonstrations to support potential use of a tunnel boring machine in welded tuff. Preliminary estimates of mechanical excavator performance in Yucca Mountain tuff are presented here. As phases of the research project are completed, well-quantified estimates will be made of performance of mechanical excavators in the Yucca Mountain tuffs.

  12. Mechanical excavator performance in Yucca Mountain tuffs

    SciTech Connect

    Ozdemir, L.; Hansen, F.D.

    1991-01-01

    A research effort of four phases is in progress at the Colorado School of Mines. The overall program will evaluate the cutability of welded tuff and other lithologies likely to be excavated at Yucca Mountain in the site characterization process. Several mechanical systems are considered with emphasis given to the tunnel boring machine. The research comprises laboratory testing, linear drag bit and disc cutter tests and potentially large-scale laboratory demonstrations to support potential use of a tunnel boring machine in welded tuff. Preliminary estimates of mechanical excavator performance in Yucca Mountain tuff are presented here. As phases of the research project are completed, well quantified estimates will be made of performance of mechanical excavators in the Yucca Mountain tuffs. 3 refs., 2 tabs.

  13. Mechanical Properties Characterization at the Nanoscale

    NASA Astrophysics Data System (ADS)

    Fong, Hanson; Sopp, Jeffery; Sarikaya, Mehmet

    2001-05-01

    Nanoindentation is an unique technique that characterizes mechanical properties of materials down to the nanometer scale. With a force range from nanoNewtons to milliNewtons, unique properties of surface structures and thin films in the mesoscale can be routinely quantifieds. With technology continually pushing toward smaller feature size in electronic and mechanical devices as well as biomaterials applications, nanoindentation has become an invaluable method to measure these characteristic features. Here, we report its application in the study the biological hard tissues. For example, using engineered metallic indentation tips, the elastic properties of the 20 nm protein layer in the biocomposite of the abalone shell was measured. The elastic modulus was found to be exceptionally high compared to most synthetic polymers. With the combination of AFM imaging nanoindentation, we were able to measure the difference in deformation behavior at the mesoscale between normal and genetically altered mouse enamel. These measurements were complementary in determining the growth defects resulting from genetically modified enamel proteins. Details of these results and future prospects will be discussed.

  14. Mechanical Properties of Infrared Transmitting Materials

    DTIC Science & Technology

    1978-01-01

    William L. Gaiser, Eglin Air Force Base Dr. George Hayes, Naval Weapons Center, China Lake Dr. Dale Holter , U.S. Army Missile Command Prof. Ray...Laboratory; and numerical work has been performed at Systems, Science and Software ; California Research Technology; shock Hydrodynamics; General Atomic...Hageman, 6. A. Gurtman, and M. Baker, "Influence of ABM Material Properties on Erosion Resulting from Particle Impact," Systems, Science, and Software

  15. Physical and Mechanical Properties of Niobium for SRF Science and Technology

    SciTech Connect

    Ganapati Rao Myneni

    2006-10-31

    Optimized mechanical and physical properties of high purity niobium are crucial for obtaining high performance SRF particle beam accelerator structures consistently. This paper summarizes these important material properties for both high purity polycrystalline and single crystal niobium.

  16. Mechanical Properties of Degraded PMR-15 Resin

    NASA Technical Reports Server (NTRS)

    Tsuji, Luis C.

    2000-01-01

    Thermo-oxidative aging produces a nonuniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hr. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and coefficient of thermal expansion (CTE) of nitrogen aged specimens were measured directly. The nitrogen-aged specimens were assumed to have the same properties as the interior material in the air-aged specimens. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

  17. 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

  18. 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.

  19. Electrical and Mechanical Properties of Graphene

    NASA Astrophysics Data System (ADS)

    Bao, Wenzhong

    Graphene is an exciting new atomically-thin two-dimensional (2D) system of carbon atoms organized in a hexagonal lattice structure. This "wonder material" has been extensively studied in the last few years since it's first isolation in 2004. Its rapid rise to popularity in scientific and technological communities can be attributed to a number of its exceptional properties. In this thesis I will present several topics including fabrication of graphene devices, electrical and mechanical properties of graphene. I will start with a brief introduction of electronic transport in nanosclae system including quantum Hall effect, followed by a discussion of fundamental electrical and mechanical properties of graphene. Next I will describe how graphene devices are produced: from the famous "mechnical exfoliation" to our innovative "scratching exfoliation" method, together with the traditional lithography fabrication for graphene devices. We also developed a lithography-free technique for making electrical contacts to suspended graphene devices. Most of the suspended devices presented in this thesis are fabricated by this technique. Graphene has remarkable electrical properties thanks to its crystal and band structures. In Chapter 3, I will first focus on proximity-induced superconductivity in graphene Josephson transistors. In this section we investigate electronic transport in single layer graphene coupled to superconducting electrodes. We observe significant suppression in the critical current I c and large variation in the product IcR n in comparison to theoretic prediction; both phenomena can be satisfactorily accounted for by premature switching in underdamped Josephson junctions. Another focus of our studies is quantum Hall effect and many body physics in graphene in suspended bilayer and trilayer graphene. We demonstrate that symmetry breaking of the first 3 Landau levels and fractional quantum Hall states are observed in both bilayer and trilayer suspended graphene

  20. 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.

  1. 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.

  2. Mechanical properties of carbon fiber composites for applications in space

    NASA Astrophysics Data System (ADS)

    Hana, P.; Inneman, A.; Daniel, V.; Sieger, L.; Petru, M.

    2015-01-01

    This article describes method of measurement mechanical properties of carbon fiber composites in space. New material structures are specifically designed for use on space satellites. Composite structures will be exposed to cosmic radiation in Earth orbit on board of a '2U CubeSat' satellite. Piezoelectric ceramic sensors are used for detection mechanical vibrations of composite test strip. A great deal of attention is paid to signal processing using 8-bit microcontroler. Fast Fourier Transformation is used. Fundamental harmonic frequencies and damping from on-board measurements will serve as the input data for terrestrial data processing. The other step of elaboration data is creation of the physical model for evaluating mechanical properties of Carbon composite - Piezoelectric ceramic system. Evaluation of anisotropic mechanical properties of piezoelectric ceramics is an interesting secondary outcome of the investigation. Extreme changes in temperature and the effect of cosmic rays will affect the mechanical properties and durability of the material used for the external construction of satellites. Comparative terrestrial measurements will be performed.

  3. Mechanical properties of phosphorene nanoribbons and oxides

    SciTech Connect

    Hao, Feng; Chen, Xi

    2015-12-21

    Mechanical properties of phosphorene nanoribbons and oxides are investigated by using density functional theory. It is found that the ideal strength of nanoribbon decreases in comparison with that of 2D phosphorene. The Young's modulus of armchair nanoribbon has a remarkable size effect because of the edge relaxations. The analysis of the stress-strain relation indicates that, owing to chemisorbed oxygen atoms, the ideal strength and Young's modulus of 2D phosphorene oxide are greatly reduced along the zigzag direction, especially upon high oxidation ratios. In addition, strain and oxidation have significant impacts on phonon dispersion.

  4. Passive mechanical properties of ovine rumen tissue

    NASA Astrophysics Data System (ADS)

    Waite, Stephen J.; Cater, John E.; Walker, Cameron G.; Amirapu, Satya; Waghorn, Garry C.; Suresh, Vinod

    2016-05-01

    Mechanical and structural properties of ovine rumen tissue have been determined using uniaxial tensile testing of tissue from four animals at five rumen locations and two orientations. Animal and orientation did not have a significant effect on the stress-strain response, but there was a significant difference between rumen locations. Histological studies showed two orthogonal muscle layers in all regions except the reticulum, which has a more isotropic structure. A quasi-linear viscoelastic model was fitted to the relaxation stage for each region. Model predictions of the ramp stage had RMS errors of 13-24% and were within the range of the experimental data.

  5. Physical and Mechanical Properties of Glass--Reinforced Plastics,

    DTIC Science & Technology

    REINFORCED PLASTICS , REVIEWS), GLASS TEXTILES, MECHANICAL PROPERTIES, ELECTRICAL PROPERTIES, SILICONE PLASTICS , POLYESTER PLASTICS , PHENOLIC... PLASTICS , EPOXY RESINS, TEST METHODS, NONDESTRUCTIVE TESTING, FIRE RESISTANT MATERIALS, POLYVINYL CHLORIDE, USSR

  6. Mechanical Properties of Nanotextured Titanium Orthopedic Screws for Clinical Applications.

    PubMed

    Descamps, Stephane; Awitor, Komla O; Raspal, Vincent; Johnson, Matthew B; Bokalawela, Roshan S P; Larson, Preston R; Doiron, Curtis F

    2013-06-01

    In this work, we modified the topography of commercial titanium orthopedic screws using electrochemical anodization in a 0.4 wt% hydrofluoric acid solution to produce titanium dioxide nanotube layers. The morphology of the nanotube layers were characterized using scanning electron microscopy. The mechanical properties of the nanotube layers were investigated by screwing and unscrewing an anodized screw into several different types of human bone while the torsional force applied to the screwdriver was measured using a torque screwdriver. The range of torsional force applied to the screwdriver was between 5 and [Formula: see text]. Independent assessment of the mechanical properties of the same surfaces was performed on simple anodized titanium foils using a triboindenter. Results showed that the fabricated nanotube layers can resist mechanical stresses close to those found in clinical situations.

  7. Coronal Jet Plasma Properties and Acceleration Mechanisms

    NASA Astrophysics Data System (ADS)

    Farid, Samaiyah; Reeves, Kathy; Savcheva, Antonia; Soto, Natalia

    2017-08-01

    Coronal jets are transient eruptions of plasma typically characterized by aprominent long spire and a bright base, and sometimes accompanied by a small filament. Jets are thought to be produced by magnetic reconnection when small-scale bipolar magnetic fields emerge into an overlying coronal field or move into a locally unipolar region. Coronal jets are commonly divided into two categories: standard jets and blowout jets, and are found in both quiet and active regions. The plasma properties of jets vary across type and location, therefore understanding the underlying acceleration mechanisms are difficult to pin down. In this work, we examine both blow-out and standard jets using high resolution multi-wavelength data. Although reconnection is commonly accepted as the primary acceleration mechanism, we also consider the contribution chromospheric evaporation to jet formation. We use seven coronal channels from SDO/AIA , Hinode/XRT Be-thin and IRIS slit-jaw data. In addition, we separate the Fe-XVIII line from the SDO/94Å channel. We calculate plasma properties including velocity, Alfven speed, and density as a function of wavelength and Differential Emission Measure (DEM). Finally, we explore the magnetic topology of the jets using Coronal Modeling System (CMS) to construct potential and non-linear force free models based on the flux rope insertion method.

  8. Lunar surface mechanical properties from Surveyor data.

    NASA Technical Reports Server (NTRS)

    Jones, R. H.

    1971-01-01

    During the Surveyor program spacecraft were successfully landed at five widely separated lunar locations. Recent computer simulations of each landing have provided more comprehensive data on the mechanical properties of the lunar surface than have been obtained previously by this method of analysis. Results show that the variations in surface bearing pressure observed at the various lunar sites are probably due to surface slope effects and do not necessarily indicate differences in soil properties at these sites. Estimates of cohesion at two sites give almost identical results and further support the conclusion that the soil properties at all sites are probably very similar. Surface pressures that resist horizontal (plowing) motion are largely due to cohesion, and density and gravitational contributions are small. It is concluded that the lunar surface bearing strength is essentially zero at the surface and, for zero surface slope, increases with penetration depth at a rate of 1.87 (plus or minus 0.33) N/cu cm. The cohesion of the lunar soil is estimated to be between 0.11 and 0.17 N/sq cm.

  9. The mechanical properties of density graded hemp/polyethylene composites

    NASA Astrophysics Data System (ADS)

    Dauvegis, Raphaël; Rodrigue, Denis

    2015-05-01

    In this work, the production and mechanical characterization of density graded biocomposites based on high density polyethylene and hemp fibres was performed. The effect of coupling agent addition (maleated polyethylene) and hemp content (0-30%) was studied to determine the effect of hemp distribution (graded content) inside the composite (uniform, linear, V and Λ). Tensile and flexural properties are reported to compare the structures, especially in terms of their stress-strain behaviors under tensile loading.

  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. Computational studies on the crystal structure, thermodynamic properties, detonation performance, and pyrolysis mechanism of 2,4,6,8-tetranitro-1,3,5,7-tetraazacubane as a novel high energy density material.

    PubMed

    Wang, Fang; Du, Hongchen; Zhang, Jianying; Gong, Xuedong

    2011-10-27

    Studies have suggested that octanitrocubane (ONC) is one of the most powerful non-nuclear high energy density material (HEDM) currently known. 2,4,6,8-Tetranitro-1,3,5,7-tetraazacubane (TNTAC) studied in this work may also be a novel HEDM due to its high nitrogen content and crystal density. Density functional theory and molecular mechanics methods have been employed to study the crystal structure, IR spectrum, electronic structure, thermodynamic properties, gas-phase and condensed-phase heat of formation, detonation performance, and pyrolysis mechanism of TNTAC. The TNTAC has a predicted density of about 2.12 g/cm(3), and its detonation velocity (10.42 km/s) and detonation pressure (52.82 GPa) are higher than that of ONC. The crystalline packing is P2(1)2(1)2(1), and the corresponding cell parameters are Z = 4, a = 8.87 Å, b = 8.87 Å, and c = 11.47 Å. Both the density of states of the predicted crystal and the bond dissociation energy of the molecule in gas phase show that the cage C-N bond is the trigger bond during thermolysis. The activation energy of the pyrolysis initiation reaction obtained from the B3LYP/6-311++G(2df,2p) level is 125.98 kJ/mol, which indicates that TNTAC meets the thermal stability request as an exploitable HEDM.

  12. 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...

  13. Engineered disulfides improve mechanical properties of recombinant spider silk.

    PubMed

    Grip, S; Johansson, J; Hedhammar, M

    2009-05-01

    Nature's high-performance polymer, spider silk, is composed of specific proteins, spidroins, which form solid fibers. So far, fibers made from recombinant spidroins have failed in replicating the extraordinary mechanical properties of the native material. A recombinant miniature spidroin consisting of four poly-Ala/Gly-rich tandem repeats and a nonrepetitive C-terminal domain (4RepCT) can be isolated in physiological buffers and undergoes self assembly into macrofibers. Herein, we have made a first attempt to improve the mechanical properties of 4RepCT fibers by selective introduction of AA --> CC mutations and by letting the fibers form under physiologically relevant redox conditions. Introduction of AA --> CC mutations in the first poly-Ala block in the miniature spidroin increases the stiffness and tensile strength without changes in ability to form fibers, or in fiber morphology. These improved mechanical properties correlate with degree of disulfide formation. AA --> CC mutations in the forth poly-Ala block, however, lead to premature aggregation of the protein, possibly due to disulfide bonding with a conserved Cys in the C-terminal domain. Replacement of this Cys with a Ser, lowers thermal stability but does not interfere with dimerization, fiber morphology or tensile strength. These results show that mutagenesis of 4RepCT can reveal spidroin structure-activity relationships and generate recombinant fibers with improved mechanical properties.

  14. Mechanical properties of kenaf composites using dynamic mechanical analysis

    NASA Astrophysics Data System (ADS)

    Loveless, Thomas A.

    Natural fibers show potential to replace glass fibers in thermoset and thermoplastic composites. Kenaf is a bast-type fiber with high specific strength and great potential to compete with glass fibers. In this research kenaf/epoxy composites were analyzed using Dynamic Mechanical Analysis (DMA). A three-point bend apparatus was used in the DMA testing. The samples were tested at 1 hertz, at a displacement of 10 ?m, and at room temperature. The fiber volume content of the kenaf was varied from 20% - 40% in 5% increments. Ten samples of each fiber volume fraction were manufactured and tested. The flexural storage modulus, the flexural loss modulus, and the loss factor were reported. Generally as the fiber volume fraction of kenaf increased, the flexural storage and flexural loss modulus increased. The loss factor remained relatively constant with increasing fiber volume fraction. Woven and chopped fiberglass/epoxy composites were manufactured and tested to be compared with the kenaf/epoxy composites. Both of the fiberglass/epoxy composites reported higher flexural storage and flexural loss modulus values. The kenaf/epoxy composites reported higher loss factor values. The specific flexural storage and specific flexural loss modulus were calculated for both the fiberglass and kenaf fiber composites. Even though the kenaf composites reported a lower density, the fiberglass composites reported higher specific mechanical properties.

  15. 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.

  16. Metal Additive Manufacturing: A Review of Mechanical Properties (Postprint)

    DTIC Science & Technology

    2016-04-21

    AFRL-RX-WP-JA-2017-0156 METAL ADDITIVE MANUFACTURING : A REVIEW OF MECHANICAL PROPERTIES (POSTPRINT) John J. Lewandowski and...2012 – 19 March 2016 4. TITLE AND SUBTITLE METAL ADDITIVE MANUFACTURING : A REVIEW OF MECHANICAL PROPERTIES (POSTPRINT) 5a. CONTRACT NUMBER...data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples

  17. Environmental properties set cell mechanics and morphology

    NASA Astrophysics Data System (ADS)

    Janmey, Paul

    2012-02-01

    Many cell types are sensitive to mechanical signals that are produced either by application of exogenous force to their surfaces, or by the resistance that their surroundings place on forces generated by the cells themselves. Cell morphology, motility, proliferation, and protein expression all change in response to substrate stiffness. Changing the elastic moduli of substrates alters the formation of focal adhesions, the assembly of actin filaments into bundles, and the stability of intermediate filaments. The range of stiffness over which different primary cell types respond can vary over a wide range and generally reflects the elastic modulus of the tissue from which these cells were isolated. Mechanosensing depends on the type of adhesion receptor by which the cell binds, and therefore on both the molecular composition of the extracellular matrix and the nature of its link to the cytoskeleton. Many cell types can alter their own stiffness to match that of the substrate to which they adhere. The maximal elastic modulus that cells such as fibroblasts can attain is similar to that of crosslinked actin networks at the concentrations in the cell cortex. The precise mechanisms of mechanosensing are not well defined, but they presumably require an elastic connection between cell and substrate, mediated by transmembrane proteins. The viscoelastic properties of different extracellular matrices and cytoskeletal elements strongly influence the response of cells to mechanical signals, and the unusual non-linear elasticity of many biopolymer gels, characterized by strain-stiffening, leads to novel mechanisms by which cells alter their stiffness by engagement of molecular motors that produce internal stresses. Cell cortical elasticity is dominated by cytoskeletal polymer networks and can be modulated by internal tension. Simultaneous control of substrate stiffness and adhesive patterns suggests that stiffness sensing occurs on a length scale much larger than single molecular

  18. Elastic properties and mechanical tension of graphene

    NASA Astrophysics Data System (ADS)

    Ramírez, R.; Herrero, C. P.

    2017-01-01

    Room-temperature simulations of graphene have been performed as a function of the mechanical tension of the layer. Finite-size effects are accurately reproduced by an acoustic dispersion law for the out-of-plane vibrations that, in the long-wave limit, behaves as ρ ω2=σ k2+κ k4 . The fluctuation tension σ is finite (˜0.1 N/m) even when the external mechanical tension vanishes. Transverse vibrations imply a duplicity in the definition of the elastic constants of the layer, as observables related to the real area of the surface may differ from those related to the in-plane projected area. This duplicity explains the variability of experimental data on the Young modulus of graphene based on electron spectroscopy, interferometric profilometry, and indentation experiments.

  19. Performance of demining sensors and soil properties

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazunori; Preetz, Holger; Igel, Jan

    2011-06-01

    Metal detector has commonly been used for landmine detection and ground-penetrating radar (GPR) is about to be deployed as dual sensor that is in combination with metal detector. Since both devices employ electromagnetic techniques, they are influenced by magnetic and dielectric properties of soil. To observe the influence, various soil properties as well as their spatial distributions were measured in four types of soil where a field test of metal detectors and GPRs took place. By analyzing soil properties these four types of soil were graded based on the estimated amount of influence on the detection techniques. The classification was compared to the detection performance of devices obtained from the blind test and a clear correlation between the difficulty of soil and the performance was observed; the detection and identification performance were degraded in soils that were classified as problematic. Therefore, it was demonstrated that the performance of metal detector and GPR for landmine detection can qualitatively be assessed by geophysical analyses.

  20. Mechanical properties of high-strength concrete

    NASA Astrophysics Data System (ADS)

    Mokhtarzadeh, Alireza

    This report summarizes an experimental program conducted to investigate production techniques and mechanical properties of high strength concrete in general and to provide recommendations for using these concretes in manufacturing precast/prestressed bridge girders. Test variables included total amount and composition of cementitious material (portland cement, fly ash, and silica fume), type and brand of cement, type of silica fume (dry densified and slurry), type and brand of high-range water-reducing admixture, type of aggregate, aggregate gradation, maximum aggregate size, and curing. Tests were conducted to determine the effects of these variables on changes in compressive strength and modulus of elasticity over time, splitting tensile strength, modulus of rupture, creep, shrinkage, and absorption potential (as an indirect indicator of permeability). Also investigated were the effects of test parameters such as mold size, mold material, and end condition. Over 6,300 specimens were cast from approximately 140 mixes over a period of 3 years.

  1. Mechanical properties of icosahedral virus capsids

    NASA Astrophysics Data System (ADS)

    Vliegenthart, G. A.; Gompper, G.

    2007-12-01

    Virus capsids are self-assembled protein shells in the size range of 10 to 100 nanometers. The shells of DNA-viruses have to sustain large internal pressures while encapsulating and protecting the viral DNA. We employ computer simulations to study the mechanical properties of crystalline shells with icosahedral symmetry that serve as a model for virus capsids. The shells are positioned on a substrate and deformed by a uni-axial force excerted by a small bead. We predict the elastic response for small deformations, and the buckling transitions at large deformations. Both are found to depend strongly on the number N of elementary building blocks (capsomers), and the Föppl-von Kármán number γ which characterizes the relative importance of shear and bending elasticity.

  2. Material modeling of biofilm mechanical properties.

    PubMed

    Laspidou, C S; Spyrou, L A; Aravas, N; Rittmann, B E

    2014-05-01

    A biofilm material model and a procedure for numerical integration are developed in this article. They enable calculation of a composite Young's modulus that varies in the biofilm and evolves with deformation. The biofilm-material model makes it possible to introduce a modeling example, produced by the Unified Multi-Component Cellular Automaton model, into the general-purpose finite-element code ABAQUS. Compressive, tensile, and shear loads are imposed, and the way the biofilm mechanical properties evolve is assessed. Results show that the local values of Young's modulus increase under compressive loading, since compression results in the voids "closing," thus making the material stiffer. For the opposite reason, biofilm stiffness decreases when tensile loads are imposed. Furthermore, the biofilm is more compliant in shear than in compression or tension due to the how the elastic shear modulus relates to Young's modulus. Copyright © 2014 Elsevier Inc. All rights reserved.

  3. Mechanical properties of nanostructure of biological materials

    NASA Astrophysics Data System (ADS)

    Ji, Baohua; Gao, Huajian

    2004-09-01

    Natural biological materials such as bone, teeth and nacre are nanocomposites of protein and mineral with superior strength. It is quite a marvel that nature produces hard and tough materials out of protein as soft as human skin and mineral as brittle as classroom chalk. What are the secrets of nature? Can we learn from this to produce bio-inspired materials in the laboratory? These questions have motivated us to investigate the mechanics of protein-mineral nanocomposite structure. Large aspect ratios and a staggered alignment of mineral platelets are found to be the key factors contributing to the large stiffness of biomaterials. A tension-shear chain (TSC) model of biological nanostructure reveals that the strength of biomaterials hinges upon optimizing the tensile strength of the mineral crystals. As the size of the mineral crystals is reduced to nanoscale, they become insensitive to flaws with strength approaching the theoretical strength of atomic bonds. The optimized tensile strength of mineral crystals thus allows a large amount of fracture energy to be dissipated in protein via shear deformation and consequently enhances the fracture toughness of biocomposites. We derive viscoelastic properties of the protein-mineral nanostructure and show that the toughness of biocomposite can be further enhanced by the viscoelastic properties of protein.

  4. Mechanical properties of nanocrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Shen, Z. H.; Hess, P.; Huang, J. P.; Lin, Y. C.; Chen, K. H.; Chen, L. C.; Lin, S. T.

    2006-06-01

    Nanocrystalline diamond (NCD) films with thicknesses in the range of 0.12-1.5 μm were deposited on silicon substrates in CH4/H2/O2 gas mixtures by microwave plasma-enhanced chemical vapor deposition. The morphology and structure of these NCD films were analyzed by field-emission scanning electron microscopy, x-ray diffraction (XRD), and ultraviolet-Raman spectroscopy. The lower limit of the grain size in the NCD films was estimated to be 10 nm from the XRD measurements. These grains are embedded in a columnar-type structure. The elastic and mechanical properties of the NCD films were determined by measuring the dispersion of laser-induced surface acoustic waves. The densities were in the range of 3.41+/-0.11 g/cm3 and Young's moduli varied between 674+/-34 and 953+/-48 GPa, depending on the growth time and deposition conditions. It is concluded that oxygen may have a significant positive effect on the elastic properties of NCD films. The growth rate decreases sharply for an oxygen content in the source gas in excess of about 4%.

  5. Biodegradable compounds: Rheological, mechanical and thermal properties

    NASA Astrophysics Data System (ADS)

    Nobile, Maria Rossella; Lucia, G.; Santella, M.; Malinconico, M.; Cerruti, P.; Pantani, R.

    2015-12-01

    Recently great attention from industry has been focused on biodegradable polyesters derived from renewable resources. In particular, PLA has attracted great interest due to its high strength and high modulus and a good biocompatibility, however its brittleness and low heat distortion temperature (HDT) restrict its wide application. On the other hand, Poly(butylene succinate) (PBS) is a biodegradable polymer with a low tensile modulus but characterized by a high flexibility, excellent impact strength, good thermal and chemical resistance. In this work the two aliphatic biodegradable polyesters PBS and PLA were selected with the aim to obtain a biodegradable material for the industry of plastic cups and plates. PBS was also blended with a thermoplastic starch. Talc was also added to the compounds because of its low cost and its effectiveness in increasing the modulus and the HDT of polymers. The compounds were obtained by melt compounding in a single screw extruder and the rheological, mechanical and thermal properties were investigated. The properties of the two compounds were compared and it was found that the values of the tensile modulus and elongation at break measured for the PBS/PLA/Talc compound make it interesting for the production of disposable plates and cups. In terms of thermal resistance the compounds have HDTs high enough to contain hot food or beverages. The PLA/PBS/Talc compound can be, then, considered as biodegradable substitute for polystyrene for the production of disposable plates and cups for hot food and beverages.

  6. 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.

  7. How Molecular Structure Affects Mechanical Properties of an Advanced Polymer

    NASA Technical Reports Server (NTRS)

    Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.; Hinkley, Jeffrey A.

    2000-01-01

    density was performed over a range of temperatures below the glass transition temperature. The physical characterization, elastic properties and notched tensile strength all as a function of molecular weight and test temperature were determined. For the uncrosslinked SI material, it was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature. For the crosslinked PETI-SI material, it was shown that the effect of crosslinking significantly enhances the mechanical performance of the low molecular weight material; comparable to that exhibited by the high molecular weight material.

  8. Mechanical performance of novel bioactive glass containing dental restorative composites

    PubMed Central

    Khvostenko, D.; Mitchell, J. C.; Hilton, T. J.; Ferracane, J. L.; Kruzic, J. J.

    2013-01-01

    Objectives Bioactive glass (BAG) is known to possess antimicrobial properties and release ions needed for remineralization of tooth tissue, and therefore may be a strategic additive for dental restorative materials. The objective of this study was to develop BAG containing dental restorative composites with adequate mechanical properties comparable to successful commercially available composites, and to confirm the stability of these materials when exposed to a biologically challenging environment. Methods Composites with 72 wt.% total filler content were prepared while substituting 0–15% of the filler with ground BAG. Flexural strength, fracture toughness, and fatigue crack growth tests were performed after several different soaking treatments: 24 hours in DI water (all experiments), two months in brain-heart infusion (BHI) media+S. mutans bacteria (all experiments) and two months in BHI media (only for flexural strength). Mechanical properties of new BAG composites were compared along with the commercial composite Heliomolar by two-way ANOVA and Tukey’s multiple comparison test (p≤0.05). Results Flexural strength, fracture toughness, and fatigue crack growth resistance for the BAG containing composites were unaffected by increasing BAG content up to 15% and were superior to Heliomolar after all post cure treatments. The flexural strength of the BAG composites was unaffected by two months exposure to aqueous media and a bacterial challenge, while some decreases in fracture toughness and fatigue resistance were observed. The favorable mechanical properties compared to Heliomolar were attributed to higher filler content and a microstructure morphology that better promoted the toughening mechanisms of crack deflection and bridging. Significance Overall, the BAG containing composites developed in this study demonstrated adequate and stable mechanical properties relative to successful commercial composites. PMID:24050766

  9. 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

  10. Photopatterning the mechanical properties of polydimethylsiloxane films

    NASA Astrophysics Data System (ADS)

    Cotton, D. P. J.; Popel, A.; Graz, I. M.; Lacour, S. P.

    2011-03-01

    Silicone rubber films with graded and localized mechanical properties are prepared using two-part polydimethylsiloxane (PDMS) elastomer, photoinhibitor compounds and conventional photolithography. First the un-cross-linked PDMS is mixed with benzophenone. The resulting positive photosensitive material is then exposed through a mask to UV light from a conventional mask aligner. Cross-linking of the UV exposed elastomer is inhibited, leading to softer regions than the surrounding unexposed matrix. By empirically fitting the nonlinear, hyperelastic Mooney-Rivlin model to experimentally measured stress-strain curves we determine the equivalent tensile modulus (E) of the rubber film. We show the PDMS tensile modulus can then be adjusted in the 0.65-2.9 MPa range by decreasing the UV exposure dose (from 24 000 to 0 mJ cm-2). Further, using a patterned UV mask, we can locally define differential regions of tensile modulus within a single PDMS rubber film. We demonstrate that "hard islands" (E ≈ 2.9 MPa) of 100 μm minimum diameter can be patterned within a 100-μm-thick, single "soft" PDMS rubber membrane (E ≈ 0.65 MPa) cured at 150 °C for 24 h. Thin gold film conductors patterned directly onto the photopatterned PDMS are stretchable and withstand uniaxial cycling to tens of percent strain. The mechanically "pixellated" PDMS rubber film provides an improved substrate with built-in strain relief for stretchable electronics.

  11. Bulk Mechanical Properties of Single Walled Carbon Nanotube Electrodes

    NASA Astrophysics Data System (ADS)

    Giarra, Matthew; Landi, Brian; Cress, Cory; Raffaelle, Ryne

    2007-03-01

    The unique properties of single walled carbon nanotubes (SWNTs) make them especially well suited for use as electrodes in power devices such as lithium ion batteries, hydrogen fuel cells, solar cells, and supercapacitors. The performances of such devices are expected to be influenced, at least in part, by the mechanical properties of the SWNTs used in composites or in stand alone ``papers.'' Therefore, the elastic moduli and ultimate tensile strengths of SWNT papers were measured as functions of temperature, SWNT purity, SWNT length, and SWNT bundling. The SWNTs used to produce the papers were synthesized in an alexandrite laser vaporization reactor at 1100^oC and purified using conventional acid-reflux conditions. Characterization of the SWNTs was performed using SEM, BET, TGA, and optical and Raman spectroscopy. The purified material was filtered and dried to yield papers of bundled SWNTs which were analyzed using dynamic mechanical analysis (DMA). It was observed that the mechanical properties of acid-refluxed SWNT papers were significantly improved by controlled thermal oxidation and strain-hardening. Elastic moduli of SWNT papers were measured between 3 and 6 GPa. Ultimate (breaking) tensile stresses were measured between 45 and 90 MPa at 1-3% strain. These results and their implications in regard to potential applications in power devices will be discussed.

  12. 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

  13. Mechanical properties and microstructure of centrifugally cast alloy 718

    NASA Astrophysics Data System (ADS)

    Michel, D. J.; Smith, H. H.

    1985-07-01

    The relationship between the microstructure and mechanical properties of alloy 718 was investigated for two discs centrifugally cast at 50 and 200 rpm and given a duplex age heat treatment. The results of mechanical property tests at temperatures from 426 to 649 °C showed that the tensile yield and ultimate strength levels of both castings were similar. However, the creep-rupture properties were considerably enhanced for the casting produced at 200 rpm. Comparison of the radial and transverse creep properties of each disc indicated that creep life was generally independent of orientation, but ductility was greatest for specimens oriented transverse to the radial direction of the casting. Fatigue crack propagation performance was not greatly influenced by orientation or mold speed parameters and was comparable to wrought alloy 718 when compared on the basis of stress intensity factor range. The centrifugal casting process was found to produce a homogeneous microstructure free of porosity but with the expected segregation of solute alloying elements to Laves and carbide phases. The effect of the as-cast microstructure on the mechanical behavior and the potential influence of hot isostatic pressing to improve the microstructure are discussed.

  14. Mechanical Properties of Low Density Alloys at Cryogenic Temperatures

    NASA Astrophysics Data System (ADS)

    Jiao, X. D.; Li, L. F.; Liu, H. J.; Yang, K.

    2006-03-01

    Low-density alloys include aluminum alloys, titanium alloys and magnesium alloys. Aluminum alloys and titanium alloys have been widely investigated and used as structural materials for cryogenic applications because of their light weight and good low-temperature mechanical properties. For aerospace applications, persistent efforts are being devoted to reducing weight and improving performance. Magnesium alloys are the lightest structural alloys among those mentioned above. Therefore, it is necessary to pay attention to magnesium alloys and to investigate their behaviors at cryogenic temperatures. In this paper, we have investigated the mechanical properties and microstructures of some magnesium alloys at cryogenic temperatures. Experimental results on both titanium and magnesium alloys are taken into account in considering these materials for space application.

  15. Mechanical Properties of Low Density Alloys at Cryogenic Temperatures

    SciTech Connect

    Jiao, X. D.; Liu, H. J.; Li, L. F.; Yang, K.

    2006-03-31

    Low-density alloys include aluminum alloys, titanium alloys and magnesium alloys. Aluminum alloys and titanium alloys have been widely investigated and used as structural materials for cryogenic applications because of their light weight and good low-temperature mechanical properties.For aerospace applications, persistent efforts are being devoted to reducing weight and improving performance. Magnesium alloys are the lightest structural alloys among those mentioned above. Therefore, it is necessary to pay attention to magnesium alloys and to investigate their behaviors at cryogenic temperatures. In this paper, we have investigated the mechanical properties and microstructures of some magnesium alloys at cryogenic temperatures. Experimental results on both titanium and magnesium alloys are taken into account in considering these materials for space application.

  16. On modeling performance of open-loop mechanisms. [control of mechanisms for performing complex sequential tasks

    NASA Technical Reports Server (NTRS)

    Sheridan, T. B.

    1973-01-01

    A technique is presented for modeling the performance of open-loop mechanisms or systems, where performance is measured by success or failure as a function of the selected target for movement along a constrained trajectory and without corrective feedback. A modification of signal detection theory is used, which normalizes dissimilar data and indicates two independent parameters of performance: (1) discriminability and (2) optimality of the distribution of selected moves. An illustrative application is made to experimental data.

  17. 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

  18. Modification of Propellant Binder Network for Improvement of Mechanical Properties

    DTIC Science & Technology

    1984-12-01

    Propellant November 1982 to Binder Network for 71 November 1984 Improvement of Mechanical Properties December 1984 Author: Polymer Research Institute 4...determine the possibility of improving mechanical properties of energetic propellants via bimodal and/or multimodal * binder network formation. * 3.0... mechanical properties . 4.5 Effect of Temperature Improvements in stress/strain properties of all the polymer/PEG 8000 bimodal systems tend to be griater at 25

  19. Mechanism-Based Design for High-Temperature, High-Performance Composites. Book 3.

    DTIC Science & Technology

    1997-09-01

    presented elsewhere [2]. Background on the mechanical properties of unclad unidirectional TMCs, including fatigue, creep and tensile fracture , can...PERFORMANCE OF MMC Section B: CONSTITUTIVE LAWS AND DESIGN BOOK 4: MEASUREMENT AND MICRO- MECHANISMS BOOK 3 Section A CONSTITUENT PROPERTIES ... Mechanical Properties of SCS6/Ti 15-3 Metal Matrix Composite After Debond On the Behaviour of Metal Matrix Composites Subjected to Cyclic Thermal

  20. Mechanical properties of orbital fat and its encapsulating connective tissue.

    PubMed

    Chen, Kinon; Weiland, James D

    2011-06-01

    There is an increasing need to understand the mechanical properties of human orbital fat and its encapsulating connective tissue (OFCT), but such knowledge is not available in the current literature. The purpose of the present study is to examine the mechanical properties of the OFCT. From 5 pairs of 76- to 92-year-old Caucasian human eyes and 33 5- to 7-month-old porcine eyes, 5 human and 11 porcine OFCT samples were dissected at the posterior pole or adjacent to the pole in the vertical, horizontal, and radial directions. Sample dimensions were fixed or measured. Tensile tests were performed on the samples in body-temperature saline. The stress-strain relationship was first approximately linear and then became nonlinear. The linear, the neo-Hookean, and the Mooney-Rivlin constants are reported in Tables 1 and 2. No statistical difference was found among their properties in the different directions in either the human or the porcine samples. Statistical differences were found between the human and the porcine material constants in the horizontal and radial directions. Among our material models, only the Mooney-Rivlin model was able to capture the mechanical properties of the OFCT in large deformation properly. The Mooney-Rivlin model was especially adaptive to the human data. This is the first time the mechanical properties of the human and porcine OFCT have been examined in the literature. We believe our data will provide valuable information to others regarding designing implant biomaterials in orbital treatments and developing computer models to study orbital biomechanics.

  1. Mechanical properties of β-HMX.

    PubMed

    Gallagher, Hugh G; Miller, John C; Sheen, David B; Sherwood, John N; Vrcelj, Ranko M

    2015-01-01

    For a full understanding of the mechanical properties of a material, it is essential to understand the defect structures and associated properties and microhardness indentation is a technique that can aid this understanding. The Vickers hardness on (010), {011} and {110} faces lay in the range of 304-363 MPa. The Knoop Hardnesses on the same faces lay in the range 314-482 MPa. From etching of three indented surfaces, the preferred slip planes have been identified as (001) and (101). For a dislocation glide, the most likely configuration for dislocation movement on the (001) planes is (001) [100] (|b| = 0.65 nm) and for the (101) plane as (101) [Formula: see text] (|b| = 1.084 nm) although (101) [010] (|b| = 1.105 nm) is possible. Tensile testing showed that at a stress value of 2.3 MPa primary twinning occurred and grew with increasing stress. When the stress was relaxed, the twins decreased in size, but did not disappear. The twinning shear strain was calculated to be 0.353 for the (101) twin plane. HMX is considered to be brittle, compared to other secondary explosives. Comparing HMX with a range of organic solids, the values for hardness numbers are similar to those of other brittle systems. Under the conditions developed beneath a pyramidal indenter, dislocation slip plays a major part in accommodating the local deformation stresses. Graphical abstractHMX undergoing tensile testing.

  2. Mechanical properties of three types of high RRR niobium

    SciTech Connect

    Myneni, Ganapati; Rao Myneni, Ganapati; Kneisel, Peter

    2004-12-01

    Several future particle accelerator projects such as the International Linear Collider (ILC), the Rare Isotope Accelerator (RIA), Energy Recovery Linacs (ERL) and Free Electron Lasers (FEL) make use of Superconducting Radio Frequency (SRF) technology. The accelerating devices (cavities) are manufactured from bulk high purity (RRR) niobium and are being operated at cryogenic temperatures. Jefferson Lab has partnered with Reference Metals Company to optimize not only the properties of the RRR z niobium for high performance accelerating structures but also to reduce the manufacturing costs for the material and the devices.tIn this paper we present the mechanical properties of three types of high RRR niobium: a) standard high RRR niobium presently used in the production of the cavities b) niobium with 150, 500 and 1200 wt. ppm tantalum content and c) high RRR single crystal niobium sliced directly from ingots.We will also briefly compare the performance of cavities made from these di

  3. Mechanical properties of gutta-percha sulfide modified asphalt

    NASA Astrophysics Data System (ADS)

    Zou, X. Y.; Gu, X. Y.; Wang, X. W.

    2017-01-01

    Gutta-percha is the isomer of caoutchouc and can be used to enhance the performance of asphalt. In this paper, the produce proceedings of gutta-percha sulfide and gutta-percha sulfide modified asphalt are introduced. The performance indices of gutta-percha sulfide modified asphalt samples with different proportions are examined based on laboratory tests and the optimum ratio of gutta-percha and sulfur is decided.The micromechanism, temperature sensitivity, high and low temperature properties and viscoelasticity of the polymer modified asphalt are analyzed to discuss the modified mechanism and to decide the optimal polymer content. Low temperature bending tests are carried out to verify the low temperature performance of gutta-percha sulfide modified asphalt mixture. Research results showed that gutta-percha sulfide modified asphalt has good low temperature performance and a promising application prospect in the cold regions.

  4. Mechanical Properties of Nuclear Fuel Surrogates using Picosecond Laser Ultrasonics

    SciTech Connect

    David Hurley; Marat Khafizov; Farhad Farzbod; Eric Burgett

    2013-05-01

    Detailed understanding between microstructure evolution and mechanical properties is important for designing new high burnup nuclear fuels. In this presentation we discuss the use of picosecond ultrasonics to measure localize changes in mechanical properties of fuel surrogates. We develop measurement techniques that can be applied to investigate heterogeneous elastic properties caused by localize changes in chemistry, grain microstructure caused by recrystallization, and mechanical properties of small samples prepared using focused ion beam sample preparation. Emphasis is placed on understanding the relationship between microstructure and mechanical properties

  5. Mechanical Properties of Gradient Structure Mg Alloy

    NASA Astrophysics Data System (ADS)

    Chen, Hongliang; Yang, Jiang; Zhou, Hao; Moering, Jordan; Yin, Zhe; Gong, Yulan; Zhao, KunYu

    2017-09-01

    In this work, a surface mechanical attrition treatment (SMAT) process was applied to AZ31B magnesium alloy at room temperature. This method produced a gradient structure on the treated AZ31B, in which the grains of the topmost layer are refined to nanoscale sizes. A combination of nanocrystallites at the surface and coarse-grains in the center are the main features of this structure. This structure results in an excellent combination of both strength and ductility. The highest yield strength for the 30 minutes SMAT AZ31B samples increased to 249 ± 5 MPa and the uniform elongation decreased to 9.3 ± 0.8 pct, whereas the original yield strength was only 147 ± 4 MPa and the uniform elongation was 15.4 ± 1.1 pct. Microstructural observations, stress relaxation tests, and hardness tests were used to verify the results. Additionally, there is a specific volume fraction of gradient structure to achieve the best mechanical performance, which is shown to be in the range of 9.3 to 14 pct for the AZ31B alloy.

  6. Mechanical Properties of Gradient Structure Mg Alloy

    NASA Astrophysics Data System (ADS)

    Chen, Hongliang; Yang, Jiang; Zhou, Hao; Moering, Jordan; Yin, Zhe; Gong, Yulan; Zhao, KunYu

    2017-07-01

    In this work, a surface mechanical attrition treatment (SMAT) process was applied to AZ31B magnesium alloy at room temperature. This method produced a gradient structure on the treated AZ31B, in which the grains of the topmost layer are refined to nanoscale sizes. A combination of nanocrystallites at the surface and coarse-grains in the center are the main features of this structure. This structure results in an excellent combination of both strength and ductility. The highest yield strength for the 30 minutes SMAT AZ31B samples increased to 249 ± 5 MPa and the uniform elongation decreased to 9.3 ± 0.8 pct, whereas the original yield strength was only 147 ± 4 MPa and the uniform elongation was 15.4 ± 1.1 pct. Microstructural observations, stress relaxation tests, and hardness tests were used to verify the results. Additionally, there is a specific volume fraction of gradient structure to achieve the best mechanical performance, which is shown to be in the range of 9.3 to 14 pct for the AZ31B alloy.

  7. Fluid Mechanical Properties of Silkworm Fibroin Solutions

    NASA Astrophysics Data System (ADS)

    Matsumoto, Akira

    2005-11-01

    The aqueous solution behavior of silk fibroin is of interest due to the assembly and processing of this protein related to the spinning of protein fibers that exhibit remarkable mechanical properties. To gain insight into the origins of this functional feature, it is desired to determine how the protein behaves under a range of solution conditions. Pure fibroin at different concentrations in water was studied for surface tension, as a measure of surfactancy. In addition, shear induced changes on these solutions in terms of structure and morphology was also determined. Fibroin solutions exhibited shear rate-sensitive viscosity changes and precipitated at a critical shear rate where a dramatic increase of 75-150% of the initial value was observed along with a decrease in viscosity. In surface tension measurements, critical micelle concentrations were in the range of 3-4% w/v. The influence of additional factors, such as sericin protein, divalent and monovalent cations, and pH on the solution behavior in relation to structural and morphological features will also be described.

  8. Mechanical properties of lattice grid composites

    NASA Astrophysics Data System (ADS)

    Fan, Hualin; Fang, Daining; Jin, Fengnian

    2008-08-01

    An equivalent continuum method only considering the stretching deformation of struts was used to study the in-plane stiffness and strength of planar lattice grid composite materials. The initial yield equations of lattices were deduced. Initial yield surfaces were depicted separately in different 3D and 2D stress spaces. The failure envelope is a polyhedron in 3D spaces and a polygon in 2D spaces. Each plane or line of the failure envelope is corresponding to the yield or buckling of a typical bar row. For lattices with more than three bar rows, subsequent yield of the other bar row after initial yield made the lattice achieve greater limit strength. The importance of the buckling strength of the grids was strengthened while the grids were relative sparse. The integration model of the method was used to study the nonlinear mechanical properties of strain hardening grids. It was shown that the integration equation could accurately model the complete stress-strain curves of the grids within small deformations.

  9. Mechanical Properties of the Upper Airway

    PubMed Central

    Strohl, Kingman P.; Butler, James P.; Malhotra, Atul

    2013-01-01

    The importance of the upper airway (nose, pharynx, and larynx) in health and in the pathogenesis of sleep apnea, asthma, and other airway diseases, discussed elsewhere in the Comprehensive Physiology series, prompts this review of the biomechanical properties and functional aspects of the upper airway. There is a literature based on anatomic or structural descriptions in static circumstances, albeit studied in limited numbers of individuals in both health and disease. As for dynamic features, the literature is limited to studies of pressure and flow through all or parts of the upper airway and to the effects of muscle activation on such features; however, the links between structure and function through airway size, shape, and compliance remain a topic that is completely open for investigation, particularly through analyses using concepts of fluid and structural mechanics. Throughout are included both historically seminal references, as well as those serving as signposts or updated reviews. This article should be considered a resource for concepts needed for the application of biomechanical models of upper airway physiology, applicable to understanding the pathophysiology of disease and anticipated results of treatment interventions. PMID:23723026

  10. AFM Manipulation of Viruses: Substrate Interactions and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Falvo, M. R.; Superfine, R.; Washburn, S.; Finch, M.; Taylor, R. M.; Chi, V.; Brooks, F. P.; Ferrari, F.; Samulski, R.

    1996-03-01

    Using an AFM tip as a manipulation tool, we have translated, rotated, and dissected individual Tobacco Mosaic Virus (TMV) and Adenovirus particles. We have implemented a teleoperation system which allows manual control of the relative tip-sample position while also allowing conventional AFM operation for imaging resulting structure. Using simple tip trajectories to bend the rod-shaped TMV, we observed a variety of resulting structures and mechanical failures. The distributed adhesive interaction between the virus and the sample surface, as well as the local tip-virus interaction affect the distortion in the shape of the virus. Experiments were performed in air as well as in liquid on graphite and Si substrates. The in-liquid experiments allow tuning of the environmental conditions, including osmolarity and pH, which are known to profoundly affect the virus structure. A continuum mechanical model relating mechanical properties to observations provides insight into the constraints for successful nondestructive manipulation.

  11. 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.

  12. PERFORMANCE ANALYSIS OF MECHANICAL DRAFT COOLING TOWER

    SciTech Connect

    Lee, S; Alfred Garrett, A; James02 Bollinger, J; Larry Koffman, L

    2009-02-10

    Industrial processes use mechanical draft cooling towers (MDCT's) to dissipate waste heat by transferring heat from water to air via evaporative cooling, which causes air humidification. The Savannah River Site (SRS) has cross-flow and counter-current MDCT's consisting of four independent compartments called cells. Each cell has its own fan to help maximize heat transfer between ambient air and circulated water. The primary objective of the work is to simulate the cooling tower performance for the counter-current cooling tower and to conduct a parametric study under different fan speeds and ambient air conditions. The Savannah River National Laboratory (SRNL) developed a computational fluid dynamics (CFD) model and performed the benchmarking analysis against the integral measurement results to accomplish the objective. The model uses three-dimensional steady-state momentum, continuity equations, air-vapor species balance equation, and two-equation turbulence as the basic governing equations. It was assumed that vapor phase is always transported by the continuous air phase with no slip velocity. In this case, water droplet component was considered as discrete phase for the interfacial heat and mass transfer via Lagrangian approach. Thus, the air-vapor mixture model with discrete water droplet phase is used for the analysis. A series of parametric calculations was performed to investigate the impact of wind speeds and ambient conditions on the thermal performance of the cooling tower when fans were operating and when they were turned off. The model was also benchmarked against the literature data and the SRS integral test results for key parameters such as air temperature and humidity at the tower exit and water temperature for given ambient conditions. Detailed results will be published here.

  13. High performance stepper motors for space mechanisms

    NASA Technical Reports Server (NTRS)

    Sega, Patrick; Estevenon, Christine

    1995-01-01

    Hybrid stepper motors are very well adapted to high performance space mechanisms. They are very simple to operate and are often used for accurate positioning and for smooth rotations. In order to fulfill these requirements, the motor torque, its harmonic content, and the magnetic parasitic torque have to be properly designed. Only finite element computations can provide enough accuracy to determine the toothed structures' magnetic permeance, whose derivative function leads to the torque. It is then possible to design motors with a maximum torque capability or with the most reduced torque harmonic content (less than 3 percent of fundamental). These later motors are dedicated to applications where a microstep or a synchronous mode is selected for minimal dynamic disturbances. In every case, the capability to convert electrical power into torque is much higher than on DC brushless motors.

  14. High performance stepper motors for space mechanisms

    NASA Astrophysics Data System (ADS)

    Sega, Patrick; Estevenon, Christine

    1995-05-01

    Hybrid stepper motors are very well adapted to high performance space mechanisms. They are very simple to operate and are often used for accurate positioning and for smooth rotations. In order to fulfill these requirements, the motor torque, its harmonic content, and the magnetic parasitic torque have to be properly designed. Only finite element computations can provide enough accuracy to determine the toothed structures' magnetic permeance, whose derivative function leads to the torque. It is then possible to design motors with a maximum torque capability or with the most reduced torque harmonic content (less than 3 percent of fundamental). These later motors are dedicated to applications where a microstep or a synchronous mode is selected for minimal dynamic disturbances. In every case, the capability to convert electrical power into torque is much higher than on DC brushless motors.

  15. 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

    the MRE procedures were repeated on the same day. Cardiac pulsation, termed intrinsic activation, produces sufficient motion to allow mechanical properties to be recovered. The poroelastic model is more consistent with the measured data from brain at low frequencies than the linear elastic model. Intrinsic activation allows MR elastography to be performed without a device shaking the head so the patient notices no differences between it and the other sequences in an MR examination. PMID:23079508

  16. 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.

  17. 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

  18. Enhanced mechanical properties of nanocomposites at low graphene content.

    PubMed

    Rafiee, Mohammad A; Rafiee, Javad; Wang, Zhou; Song, Huaihe; Yu, Zhong-Zhen; Koratkar, Nikhil

    2009-12-22

    In this study, the mechanical properties of epoxy nanocomposites with graphene platelets, single-walled carbon nanotubes, and multi-walled carbon nanotube additives were compared at a nanofiller weight fraction of 0.1 +/- 0.002%. The mechanical properties measured were the Young's modulus, ultimate tensile strength, fracture toughness, fracture energy, and the material's resistance to fatigue crack propagation. The results indicate that graphene platelets significantly out-perform carbon nanotube additives. The Young's modulus of the graphene nanocomposite was approximately 31% greater than the pristine epoxy as compared to approximately 3% increase for single-walled carbon nanotubes. The tensile strength of the baseline epoxy was enhanced by approximately 40% with graphene platelets compared to approximately 14% improvement for multi-walled carbon nanotubes. The mode I fracture toughness of the nanocomposite with graphene platelets showed approximately 53% increase over the epoxy compared to approximately 20% improvement for multi-walled carbon nanotubes. The fatigue resistance results also showed significantly different trends. While the fatigue suppression response of nanotube/epoxy composites degrades dramatically as the stress intensity factor amplitude is increased, the reverse effect is seen for graphene-based nanocomposites. The superiority of graphene platelets over carbon nanotubes in terms of mechanical properties enhancement may be related to their high specific surface area, enhanced nanofiller-matrix adhesion/interlocking arising from their wrinkled (rough) surface, as well as the two-dimensional (planar) geometry of graphene platelets.

  19. ACCESS: Thermal Mechanical Design, Performance, and Status

    NASA Astrophysics Data System (ADS)

    Kaiser, Mary Elizabeth; Morris, M. J.; McCandliss, S. R.; Rauscher, B. J.; Kimble, R. A.; Kruk, J. W.; Wright, E. L.; Bohlin, R.; Kurucz, R. L.; Riess, A. G.; Pelton, R.; Deustua, S. E.; Dixon, W. V.; Sahnow, D. J.; Benford, D. J.; Gardner, J. P.; Feldman, P. D.; Moos, H. W.; Lampton, M.; Perlmutter, S.; Woodgate, B. E.

    2014-01-01

    Systematic errors associated with astrophysical data used to probe fundamental astrophysical questions, such as SNeIa observations used to constrain dark energy theories, are now rivaling and exceeding the statistical errors associated with these measurements. ACCESS: Absolute Color Calibration Experiment for Standard Stars is a series of rocket-borne sub-orbital missions and ground-based experiments designed to enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35 - 1.7μm bandpass. Achieving this level of accuracy requires characterization and stability of the instrument and detector including a thermal background that contributes less than 1% to the flux per resolution element in the NIR. We will present the instrument and calibration status with a focus on the thermal mechanical design and associated performance data. The detector control and performance will be presented in a companion poster (Morris, et al). NASA APRA sounding rocket grant NNX08AI65G supports this work.

  20. Effect of cellulose fiber reinforcement on the temperature dependent mechanical performance of nylon 6

    Treesearch

    Mehdi Tajvidi; Mokhtar Feizmand; Robert H. Falk; Colin Felton

    2009-01-01

    In order to quantify the effect of temperature on the mechanical properties of pure nylon 6 and its composite with cellulose fibers (containing 25 wt% cellulose fibers), the materials were sampled and tested at three representative temperatures of 256, 296, and 336 K. Flexural and tensile tests were performed and the reductions in mechanical properties were evaluated....

  1. Mechanical Property of HVOF Inconel 718 Coating for Aeronautic Repair

    NASA Astrophysics Data System (ADS)

    Lyphout, Christophe; Fasth, Angelica; Nylen, Per

    2014-02-01

    The module of elasticity is one of the most important mechanical properties defining the strength of a material which is a prerequisite to design a component from its early stage of conception to its field of application. When a material is to be thermally sprayed, mechanical properties of the deposited layers differ from the bulk material, mainly due to the anisotropy of the highly textured coating microstructure. The mechanical response of the deposited layers significantly influences the overall performance of the coated component. It is, therefore, of importance to evaluate the effective module of elasticity of the coating. Conventional experimental methods such as microindentation, nanoindentation and four-point bending tests have been investigated and their results vary significantly, mainly due to inhomogeneous characteristics of the coating microstructure. Synchrotron radiation coupled with a tensile test rig has been proposed as an alternative method to determine the coating anisotropic elastic behavior dependence on crystallographic orientations. The investigation was performed on Inconel 718 (IN718) HVOF coatings sprayed on IN718 substrates. Combining these experimental techniques yield a deeper understanding of the nature of the HVOF coating Young's modulus and thus a tool for Design Practice for repair applications.

  2. Effect of Preheating on the Mechanical Properties of Resin Composites

    PubMed Central

    Uctasli, Mine Betül; Arisu, Hacer Deniz; Lasilla, Lippo VJ; Valittu, Pekka K.

    2008-01-01

    Objectives The purpose of this study was to compare the flexural strength and modulus of two commercial resin composites, at room temperature and 40, 45 and 50°C prior to light polymerization with standard and step-cure protocols. Methods One nanohybrid (Grandio, VOCO, Cuxhaven, Germany), and microhybrid composite resin (Filtek Z250, 3M ESPE, St. Paul, MN, USA) were used. The materials were inserted into rectangular moulds at room temperature or preheated to a temperature of 40, 45 or 50°C and cured with standard or step-cure protocols with high intensity halogen (Elipar Highlight, 3M-ESPE, St. Paul, MN, USA). Ten specimens were prepared for each preheating and light curing protocol. A three-point bending test was performed using a universal testing machine at a crosshead speed of 1 mm/min. The data were analyzed by one-way analysis of variance and Tukey’s post hoc tests (P<.05) to examine the effect of curing protocol and preheating. Pearson’s correlation test was used to determine the correlation between tested mechanical properties and preheating. Results There were no statistically significant difference between tested mechanical properties of the materials, curing protocols and temperature of the materials. No significant correlation was found between preheating and tested mechanical properties. Conclusions The mechanical properties of the tested materials did not changed by preheating so the tested materials could be preheated because of the other potential clinical advantages like more adaptation to the cavity walls. PMID:19212532

  3. Mechanical and biological properties of oxidized horn keratin.

    PubMed

    Zhang, Quanbin; Shan, Guanghua; Cao, Ping; He, Jia; Lin, Zhongshi; Huang, Yaoxiong; Ao, Ningjian

    2015-02-01

    The goal of this study was to investigate the mechanical and biological properties of oxidized keratin materials, which were obtained by using buffalo horns to oxidize. It could provide a way to evaluate their potential for clinical translatability. The characterization on their composition, mechanical properties, and biological responses was performed. It is found that the oxidation process could lead the disulfide bond to break down and then to form sulfonic acid, or even make partial peptide chain to be fragment for the new modification of amino acid. Hence the oxidized horn keratins have lower thermal stability and hydrolytic stability in comparison with horn keratin, but the degradation products of oxidized horn keratins have no significant difference. In addition, the mechanical properties of oxidized horn keratins are poorer than that of horn keratin, but the oxidized horn keratins still have disulfide bonds to form a three-dimensional structure, which benefits for their mechanical properties. The fracture toughness of oxidized horn keratins increases with the increase in the degree of oxidation. After oxidation, the oxidized horn keratins have lower cytotoxicity and lower hemolysis ratio. Moreover, when the oxidized horn keratins, as well as different concentration of degradation products of oxidized horn keratins, are directly in contact with platelet-rich plasma, platelets are not activated. It suggests that the oxidized horn keratins have good hemocompatibility, without triggering blood thrombosis. The implantation experiment in vivo also demonstrates that the oxidized horn keratins are compatible with the tissue, because there are minimal fibrous capsule and less of infiltration of host cells, without causing serious inflammation. In summary, the oxidized horn keratins can act as implanted biomaterial devices that are directly in contact with blood and tissue. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Asteroid Regolith Mechanical Properties: Laboratory Experiments With Cohesive Powders

    NASA Astrophysics Data System (ADS)

    Durda, Daniel D.; Scheeres, D. J.; Roark, S. E.; Dissly, R.; Sanchez, P.

    2012-10-01

    Despite clear evidence that small asteroids undergo drastic physical evolution, the geophysics and mechanics of many of the processes governing that evolution remain a mystery due to a lack of scientific data, both on the sub-surface and global geophysics of these small bodies and on the mechanical properties of regoliths in the unique micro-gravity regime they inhabit. We are beginning a three-year effort to study regolith properties and processes on low-gravity, small asteroids by conducting analog experiments with cohesive powders in a 1-g laboratory environment. Based on a rigorous comparison of forces it can be shown that van der Waals cohesive forces between millimeter to centimeter-sized grains on asteroids ranging in size from Eros to Itokawa, respectively, may exceed their ambient weight several-fold. This observation implies that regoliths composed of impact debris of those sizes should behave on the microgravity surfaces of small asteroids like flour or other cohesive powders do in the 1-g environment here on Earth. Our goal is to develop an improved understanding of the role of cohesion in affecting regolith processes and surface morphology of small Solar System bodies, some the targets of ongoing and proposed NASA New Frontiers and Discovery missions, and to quantify the range of expected mechanical properties of such regoliths. Our experiments will be conducted in ambient and vacuum conditions within an environmental test chamber at Ball Aerospace & Technologies Corporation (BATC) in Boulder, CO. To aid in validating our experiment chamber and support equipment performance, and before proceeding with experiments on geologic regolith simulant materials, we will perform a series of comparative, ‘calibration’ experiments with micro glass spheres; all primary experiments will be performed with at least one non-idealized regolith simulant, like JSC-1, that more realistically simulates the angular particle shapes expected in actual geologic fragments

  5. 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

  6. Cell mechanosensitivity: mechanical properties and interaction with gravitational field.

    PubMed

    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.

  7. 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.

  8. An Experimental Investigation of Shale Mechanical Properties Through Drained and Undrained Test Mechanisms

    NASA Astrophysics Data System (ADS)

    Islam, Md. Aminul; Skalle, Paal

    2013-11-01

    Shale mechanical properties are evaluated from laboratory tests after a complex workflow that covers tasks from sampling to testing. Due to the heterogeneous nature of shale, it is common to obtain inconsistent test results when evaluating the mechanical properties. In practice, this variation creates errors in numerical modeling when test results differ significantly, even when samples are from a similar core specimen. This is because the fundamental models are based on the supplied test data and a gap is, therefore, always observed during calibration. Thus, the overall goal of this study was to provide additional insight regarding the organization of the non-linear model input parameters in borehole simulations and to assist other researchers involved in the rock physics-related research fields. To achieve this goal, the following parallel activities were carried out: (1) perform triaxial testing with different sample orientations, i.e., 0°, 45°, 60°, and 90°, including the Brazilian test and CT scans, to obtain a reasonably accurate description of the anisotropic properties of shale; (2) apply an accurate interpretative method to evaluate the elastic moduli of shale; (3) evaluate and quantify the mechanical properties of shale by accounting for the beddings plane, variable confinement pressures, drained and undrained test mechanisms, and cyclic versus monotonic test effects. The experimental results indicate that shale has a significant level of heterogeneity. Postfailure analysis confirmed that the failure plane coincides nicely with the weak bedding plane. The drained Poisson’s ratios were, on average, 40 % or lower than the undrained rates. The drained Young’s modulus was approximately 48 % that of the undrained value. These mechanical properties were significantly impacted by the bedding plane orientation. Based on the Brazilian test, the predicted tensile strength perpendicular to the bedding plane was 12 % lower than the value obtained using the

  9. Mechanical properties of Inconel 617 and 618

    SciTech Connect

    McCoy, H E; King, J F

    1985-02-01

    Inconel 617 and 618 were evaluated for application in high-temperature gas-cooled reactors (HTGRs). Techniques were developed for making sound welds, and tests were performed on base and weld metals. Specimens of both materials were aged to 20,000 h to evaluate thermal stability. Short-term tensile tests on alloy 617 showed that aging severely reduced the strain at fracture at both ambient and elevated temperatures. The impact energy at ambient temperature was severely degraded by aging. Creep tests showed that fracture occurred at 593 through 704{sup 0}C after only 1 to 2% strain, and higher strains were noted at higher temperatures. There was no detectable difference between the creep behavior in air and that in HTGR helium environments. Inconel alloy 618 had excellent stability during aging. Fracture strains in short-term tensile tests and impact energies in impact tests remained high after aging. The creep properties of alloy 618 were equivalent in air and in HTGR helium. Both alloys were carburized during creep testing in HTGR helium, and the rate of carburization became rather high at 760{sup 0}C and higher temperatures. 49 figures, 20 tables.

  10. 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

  11. Equivalent mechanical properties of textile monolayers from discrete asymptotic homogenization

    NASA Astrophysics Data System (ADS)

    Goda, Ibrahim; Assidi, Mohamed; Ganghoffer, Jean-François

    2013-12-01

    The determination of the effective mechanical moduli of textiles from mechanical measurements is usually difficult due to their discrete architecture, which makes micromechanical analyses a relevant alternative to access those properties. Micropolar continuum models describing the effective mechanical behavior of woven fabric monolayers are constructed from the homogenization of an identified repetitive pattern of the textile within a representative unit cell. The interwoven yarns within the textile are represented as a network of trusses connected by nodes at their crossover points. These trusses have extensional and bending rigidities to allow for yarn stretching and flexion, and a transverse shear deformation is additionally considered. Interactions between yarns at the crossover points are captured by beam segments connecting the nodes. The woven fabric is modeled after homogenization as an anisotropic planar continuum with two preferred material directions in the mean plane of the textile. Based on the developed methodology, the effective mechanical properties of plain weave and twill are evaluated, including their bending moduli and characteristic flexural lengths. A satisfactory agreement is obtained between the effective moduli obtained by homogenization and numerical values obtained by finite element simulations performed over periodic unit cells.

  12. Mechanical Properties of Oil Palm Empty Fruit Bunch Fiber

    NASA Astrophysics Data System (ADS)

    Gunawan, Fergyanto E.; Homma, Hiroomi; Brodjonegoro, Satryo S.; Hudin, Afzer Bin Baseri; Zainuddin, Aryanti Binti

    In tropical countries such as Indonesia and Malaysia, the empty fruit bunches are wastes of the oil palm industry. The wastes are abundantly available and has reached a level that severely threats the environment. Therefore, it is a great need to find useful applications of those waste materials; but firstly, the mechanical properties of the EFB fiber should be quantified. In this work, a small tensile test machine is manufactured, and the tensile test is performed on the EFB fibers. The results show that the strength of the EFB fiber is strongly affected by the fiber diameter; however, the fiber strength is relatively low in comparison to other natural fibers.

  13. Modeling of Mechanical Properties of Advanced Nanostructured Ceramic Composites

    DTIC Science & Technology

    2010-03-15

    technical report 3. DATES COVERED (From - To) From Ol-Jan-2007 to 31 -Dec-2009 4. TITLE AND SUBTITLE Modeling of Mechanical Properties of Advanced ...for puj^Ux^ r^Wse_- dC5+rvioockd>v^ <JMT4MTLC4<JSI . 13. SUPPLEMENTARY NOTES 14. ABSTRACT Mechanical properties of advanced nanostructured...Modeling of Mechanical Properties of Advanced Nanostructured Ceramic Composites Program Officer: Larry Kabacoff CO-PI Information Number of Co-PIs

  14. Mechanical Properties of Several Magnesium and Aluminum Composites

    DTIC Science & Technology

    1992-12-01

    34AD-A262 481 ARMY RESEARCH LABORATORY Mechanical Properties of Several Magnesium and Aluminum Composites Nikos Tsangarakis and Barmac Taleghani ARL...ESJEI L .PwmOM N.ajmns Mechanical Properties of Several Magnesium and Aluminum Composites 2.AUIwORU Nikos Tsangarakis and Barmac Taleghani 7. PERONUMMN...Several composites of magnesiumn and aluminum alloys were tested In order to assess and evaluate their mechanical properties . The magnesium alloys were

  15. Mechanical Properties of Ceramics for High Temperature Applications

    DTIC Science & Technology

    1976-12-01

    U.S. DEPARTMENT OF COMMERCE National Technical Information Service AD-A034 262 MFIHANICAL PROPERTIES OF CERAMICS FOR HIGH TEMPERATURE APPLICATIONS...Atlantic Treaty Organization 7 rue Ancelle, 92200 Neujily sur Seinle, France 6.TtlcMECHANICAL PROPERTIES OF CERAMICS FOR HIGH TEMPERATURE APPLICATIONS...whlichi are outlined onl thle Outside Back Covers of all AGARI) publications. 13. Key words/Descriptors . Ceramics Fracture properties Mechanical properties

  16. An Experimental Evaluation of Mechanical Properties of Hybrid Reinforcements

    NASA Astrophysics Data System (ADS)

    Sai Kumar, A.; Ganesan, G.; Karthikeyan, K.

    2017-07-01

    This paper presents the mechanical properties of unidirectional hybrid reinforcements formed from continuous fibres impregnated with a fibre binding material which are used for reinforcing the concrete. Recently FRP (Fibre Reinforced Polymer) manufacturers and suppliers have been increased all over the world because of the superior performance of FRP products in the construction industry. Its non-corrosive nature has turned the attention of many researchers to make several studies on different type of FRP products. Through a vast research, several standards also have been formulated. In this regard a new combination of FRP materials is tried in this paper and its properties have been derived. Carbon fibre and glass fibres fuse in this study to form a new hybrid rebar. The design properties such as tensile strength, tensile modulus, and compressive strength have been studied as per ASTM standards and it has been identified that the Hybrid rebar show a superior performance in comparison with GFRP (Glass FRP) and Steel rebars. This extraordinary performance of hybrid composite material increases the extensive engineering applications such as transport industry, aeronautics, naval, automotive industries.

  17. Mechanism of Tennis Racket Spin Performance

    NASA Astrophysics Data System (ADS)

    Kawazoe, Yoshihiko; Okimoto, Kenji; Okimoto, Keiko

    Players often say that some strings provide a better grip and more spin than others, but ball spin did not depend on string type, gauge, or tension in pervious laboratory experiments. There was no research work on spin to uncover what is really happening during an actual tennis impact because of the difficulty of performing the appropriate experiments. The present paper clarified the mechanism of top spin and its improvement by lubrication of strings through the use of high-speed video analysis. It also provided a more detailed explanation of spin behavior by comparing a racket with lubricated strings with the famous “spaghetti” strung racket, which was banned in 1978 by the International Tennis Federation because it used plastic spaghetti tubing over the strings to reduce friction, resulting in excessive ball spin. As the main strings stretch and slide sideways more, the ball is given additional spin due to the restoring force parallel to the string face when the main strings spring back and the ball is released from the strings. Herein, we also showed that the additional spin results in a reduction of shock vibrations of the wrist joint during impact.

  18. Evaluation of the mechanical and architectural properties of glenoid bone.

    PubMed

    Mimar, Raghad; Limb, David; Hall, Richard M

    2008-01-01

    Successful glenoid fixation in shoulder arthroplasty is partly dependent on the properties of the underlying bone. Therefore, mapping of the glenoid surface and locating the bone with the highest quality, in terms of mechanical properties and morphology, is a key requirement in ensuring effective fixation. To this end, an investigation was undertaken to study the relationship between indentation behavior and the quality of the glenoid bone. Nineteen embalmed glenoids were obtained from human cadavers (mean age at death, 82 years). Each specimen was tested using a cylindrical indentor at 11 predetermined points to investigate load-displacement behavior. Microcomputed tomography analysis was performed to ascertain the bone volume (BV)/total volume (TV) fraction of the trabecular bone and the subchondral thickness. Statistical analysis showed that both strength and modulus varied with indentation position. Significant relationships were found between either strength or modulus and BV/TV or subchondral thickness, although the explained variance was relatively low.

  19. Mechanical properties of micro-injected HDPE composites

    NASA Astrophysics Data System (ADS)

    Bongiorno, A.; Pagano, C.; Agnelli, S.; Baldi, F.; Fassi, I.

    2016-03-01

    Micro-injection moulding is one of the key manufacturing technologies for the mass production of high value polymeric miniaturized-components. However, this process is not just a straightforward down scaling of the conventional injection moulding technique. Indeed, during the micro-injection the polymer melt is forced to flow at high strain rates through very small channels in non-isothermal conditions, and this can lead to complex microstructures and to parts with unexpected performances. In this work, the relationships among the processing conditions, the mechanical properties and the microstructural characteristics of miniaturized specimens obtained by injection moulding were investigated. Two model systems were considered with the same filler content of 15% wt. (HDPE-talc and HDPE-glass beads), representative of two different types of micro-composites: containing lamellar and spherical micro-particles, respectively. The attention was focused on the influence of the filler type and the process conditions on the mechanical behaviour, examined by uniaxial tensile tests and dynamic-mechanical analyses, and on the morphological characteristics of the specimens, examined by microscopy analyses. The results highlight that mechanical response of the miniaturized specimens is significantly affected by both the filler and the process conditions that can have an influence on the polymer microstructure. Lamellar composites showed the best performance due to the orientation of the talc particles during the micro-injection process, while, different morphologies of the skin/core transition region in dependence on the process temperatures were observable.

  20. Mechanical and physical properties of nanostructured polymer films

    NASA Astrophysics Data System (ADS)

    Fabbroni, Elizabeth Frances

    Methods for studying the adhesive and mechanical nature of polymer films using the JKR (Johnson, Kendall, and Roberts) theory to describe contact mechanics and the Maugis model for interfacial fracture are employed in the study of commercial and model polymer systems. Axissymmetric adhesion tests were performed on both bimodal acrylic latex films and micellar thin films cast on an elastomeric block of poly(dimethyl siloxane) to investigate the fracture properties due to adhesive contact. A characterization of the viscoelastic nature of thin films has been conducted for both systems. The properties of bimodal latex films consisting of a mixture of hard and soft particles have been investigated. The properties of the bimodal film are attributed to soft particles when there is a lower hard volume fraction, a function that is depedant upon the modulus of the constituent materials and varies as a power law. Conversely, it is shown that for high volume fractions of hard materials, the film properties depended strongly upon the nature of the rigid constituent in the bimodal coatings. Diblock copolymer micelles, with a core of poly(methyl methacrylate) and a corona of poly(n-butyl) acrylate were investigated on both the nanoscale and macroscale as a model latex film. The solution properties of the micelles were studied by dynamic light scattering. Dry micellar thin films were studied by atomic force microscopy, and the effects of micellar annealing were observed. Subsequent adhesive and mechanical testing of the micellar thin films were performed by utilizing poly(dimethyl siloxane) as an elastomeric base layer for the films. The effects of surface oxidation of the PDMS were studied. These data were used to investigate the velocity, v*, at which viscoelastic properties become apparent. This value depended upon the micellar layer thickness when values were on the order of 1mum or smaller. Finally, a technique was developed for the study of the AC response of poly

  1. Mechanical properties of non-woven glass fiber geopolymer composites

    NASA Astrophysics Data System (ADS)

    Rieger, D.; Kadlec, J.; Pola, M.; Kovářík, T.; Franče, P.

    2017-02-01

    This experimental research focuses on mechanical properties of non-woven glass fabric composites bound by geopolymeric matrix. This study investigates the effect of different matrix composition and amount of granular filler on the mechanical properties of final composites. Matrix was selected as a metakaolin based geopolymer hardened by different amount of potassium silicate activator. The ceramic granular filler was added into the matrix for investigation of its impact on mechanical properties and workability. Prepared pastes were incorporated into the non-woven fabrics by hand roller and final composites were stacked layer by layer to final thickness. The early age hardening of prepared pastes were monitored by small amplitude dynamic rheology approach and after 28 days of hardening the mechanical properties were examined. The electron microscopy was used for detail description of microstructural properties. The imaging methods revealed good wettability of glass fibers by geopolymeric matrix and results of mechanical properties indicate usability of these materials for constructional applications.

  2. Some mechanical and molecular aspects of the performance of composites.

    PubMed

    Eirich, F R

    1984-01-01

    Starting from known features of the mechanical behavior of macromolecular materials, and from how reinforcement affords compound properties, a thesis is advanced how composite performance and endurance may be based on a fine tuning of the properties of reinforcer, interphase, and matrix. The importance of their relative moduli and extensibilities and the critical role of the interphase are emphasized. It is proposed that the latter's ability to strain harden is crucial. Thus, the interphase should be only slightly crosslinked, its wetting of filler and matrix aided only by a small extent of interfacial covalent-bonding, and its modulus be raised by the addition of well-submicron size reinforcing filler. In this context, the meaning of some published data is discussed.

  3. Synthetic fuels handbook: properties, process and performance

    SciTech Connect

    Speight, J.

    2008-07-01

    The handbook is a comprehensive guide to the benefits and trade-offs of numerous alternative fuels, presenting expert analyses of the different properties, processes, and performance characteristics of each fuel. It discusses the concept systems and technology involved in the production of fuels on both industrial and individual scales. Chapters 5 and 7 are of special interest to the coal industry. Contents: Chapter 1. Fuel Sources - Conventional and Non-conventional; Chapter 2. Natural Gas; Chapter 3. Fuels From Petroleum and Heavy Oil; Chapter 4. Fuels From Tar Sand Bitumen; Chapter 5. Fuels From Coal; Chapter 6. Fuels From Oil Shale; Chapter 7. Fuels From Synthesis Gas; Chapter 8. Fuels From Biomass; Chapter 9. Fuels From Crops; Chapter 10. Fuels From Wood; Chapter 11. Fuels From Domestic and Industrial Waste; Chapter 12. Landfill Gas. 3 apps.

  4. MECHANICAL PROPERTIES OF SHIRASU TUNNEL TAKEN ACCOUNT OF GEOTECHNICAL PROPERTIES OF SHIRASU GROUND

    NASA Astrophysics Data System (ADS)

    Taho, Toru; Suzuki, Masayuki; Sugawara, Kentaro; Kitamura, Ryosuke

    Shirasu which is defined as the non-welded part of pyroclastic flow deposits is widely distributed in the southern part of Kyushu Island. Shirasu is regarded as a soft ground when the mountain tunneling method is applied because its unconfined compression strength is only 20-100 kN/m2. Nevertheless, it is well known among the practical engineers that Shirasu tunnel is stable. In this paper the mechanical properties of Shirasu tunnel was analyzed, taking account of the geotechnical properties of Shirasu ground, where the laboratory and in-situ tests were carried out with the field measurement in tunnel. Furthermore the numerical experiment by FDM was also performed by using the proposed nonlinear mechanical model for Shirasu ground to compare the numerical results with those obtained from the field measurement.

  5. Mechanical properties determination of AM components

    NASA Astrophysics Data System (ADS)

    Dzugan, J.; Sibr, M.; Konopík, P.; Procházka, R.; Rund, M.

    2017-02-01

    Characterisation of engineering materials and components is a crucial part for design and save service life utilization. Due to components processing technologies and exploitation conditions local properties can significantly vary from location to location over larger components as well as over small material volumes with gradual material changes such as welds, coatings or additively manufactured parts. The current paper is dealing with local properties characterisation for additively manufacture (AM) components by micro tensile test (M-TT). Components produced by additive manufacturing techniques yield properties variation in dependence of the considered location within the component regarding to direction in relation to deposition process. Properties vary over the thickness, length, angle or contacts with the supporting structures necessary for a successful components production by additive manufacturing techniques. The properties differences are mainly related to varying heating/reheating and cooling conditions at various locations of usually very complex parts produced mainly by these technologies. The standard testing procedures fail to characterize such local properties of complex shaped objects due to large size requirements on specimens. Therefore, new techniques have to be established for such detailed local characterizations. Results of miniaturized tensile tests application for local properties and orientations are shown here.

  6. Microstructural and Mechanical Properties of Alkali Activated Colombian Raw Materials.

    PubMed

    Criado, Maria; Aperador, Willian; Sobrados, Isabel

    2016-03-05

    Microstructural and mechanical properties of alkali activated binders based on blends of Colombian granulated blast furnace slag (GBFS) and fly ash (FA) were investigated. The synthesis of alkali activated binders was conducted at 85 °C for 24 h with different slag/fly ash ratios (100:0, 80:20, 60:40, 40:60, 20:80, and 0:100). Mineralogical and microstructural characterization was carried out by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) and Nuclear magnetic resonance (NMR). Mechanical properties were evaluated through the compressive strength, modulus of elasticity and Poisson's ratio. The results show that two different reaction products were detected in the slag/fly ash mixtures, a calcium silicate hydrate with Al in its structure (C-A-S-H gel) and a sodium aluminosilicate hydrate (N-A-S-H gel) with higher number of polymerized species and low content in Ca. It was found that with the increase of the amount of added slag, the amount of C-A-S-H gel increased and the amount of N-A-S-H gel decreased. The matrix was more dense and compact with almost absence of pores. The predominance of slag affected positively the compressive strength, Young's modulus and Poisson's ratio, with 80% slag and 20% fly ash concrete being the best mechanical performance blend.

  7. Microstructural and Mechanical Properties of Alkali Activated Colombian Raw Materials

    PubMed Central

    Criado, Maria; Aperador, Willian; Sobrados, Isabel

    2016-01-01

    Microstructural and mechanical properties of alkali activated binders based on blends of Colombian granulated blast furnace slag (GBFS) and fly ash (FA) were investigated. The synthesis of alkali activated binders was conducted at 85 °C for 24 h with different slag/fly ash ratios (100:0, 80:20, 60:40, 40:60, 20:80, and 0:100). Mineralogical and microstructural characterization was carried out by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) and Nuclear magnetic resonance (NMR). Mechanical properties were evaluated through the compressive strength, modulus of elasticity and Poisson’s ratio. The results show that two different reaction products were detected in the slag/fly ash mixtures, a calcium silicate hydrate with Al in its structure (C-A-S-H gel) and a sodium aluminosilicate hydrate (N-A-S-H gel) with higher number of polymerized species and low content in Ca. It was found that with the increase of the amount of added slag, the amount of C-A-S-H gel increased and the amount of N-A-S-H gel decreased. The matrix was more dense and compact with almost absence of pores. The predominance of slag affected positively the compressive strength, Young’s modulus and Poisson’s ratio, with 80% slag and 20% fly ash concrete being the best mechanical performance blend. PMID:28773294

  8. Investigation of properties and performance of ceramic composite components

    SciTech Connect

    Stinchcomb, W.W.; Reifsnider, K.L.; Dunyak, T.J. . Dept. of Engineering Science and Mechanics)

    1992-06-15

    The objective of the work reported herein is to develop an understanding of the mechanical behavior of advanced ceramic composites subjected to elevated temperature and dynamic (cyclic) loading, to develop a test system and test methods to obtain the properties and performance information required to design engineering components made from ceramic composite materials, and to provide critical and comprehensive evaluations of such materials to material synthesizers and developers to support and enhance progress in ceramic composite material development. The accomplishments of the investigation include the design, development, and demonstration of a high temperature, biaxial mechanical test facility for ceramic composite tubes and the development and validation of a performance simulation model (MRLife) for ceramic composites.

  9. Investigation of properties and performance of ceramic composite components

    SciTech Connect

    Stinchcomb, W.W.; Reifsnider, K.L.; Dunyak, T.J.

    1992-06-15

    The objective of the work reported herein is to develop an understanding of the mechanical behavior of advanced ceramic composites subjected to elevated temperature and dynamic (cyclic) loading, to develop a test system and test methods to obtain the properties and performance information required to design engineering components made from ceramic composite materials, and to provide critical and comprehensive evaluations of such materials to material synthesizers and developers to support and enhance progress in ceramic composite material development. The accomplishments of the investigation include the design, development, and demonstration of a high temperature, biaxial mechanical test facility for ceramic composite tubes and the development and validation of a performance simulation model (MRLife) for ceramic composites.

  10. 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

    2017-08-30

    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.

  11. Energetic Particle Synthesis of Metastable Layers for Superior Mechanical Properties

    SciTech Connect

    Follstaedt, D.M.; Knapp, J.A.; Myers, S.M.; Dugger, M.T.; Friedmann, T.A.; Sullivan, J.P.; Monteiro, O.R.; Ager, J.W. III; Brown, I.G.; Christenson, T.

    1998-01-01

    Energetic particle methods have been used to synthesize two metastable layers with superior mechanical properties: amorphous Ni implanted with overlapping Ti and C, and amorphous diamond-like carbon (DLC) formed by vacuum-arc deposition or pulsed laser deposition. Elastic modulus, yield stress and hardness were reliably determined for both materials by fitting finite-element simulations to the observed layer/substrate responses during nanoindentation. Both materials show exceptional properties, i.e., the yield stress of amorphous Ni(Ti,C) exceeds that of hardened steels and other metallic glasses, and the hardness of DLC (up to 88 GPa) approaches that of crystalline diamond (approx. 100 GPa). Tribological performance of the layers during unlubricated sliding contact appears favorable for treating Ni-based micro-electromechanical systems: stick-slip adhesion to Ni is eliminated, giving a low coefficient of friction (approx. 0.3-0.2) and greatly reduced wear. We discuss how energetic particle synthesis is critical to forming these phases and manipulating their properties for optimum performance.

  12. Comparing the microstructure and mechanical properties of Bombyx mori and Antheraea pernyi cocoon composites.

    PubMed

    Guan, Juan; Zhu, Wenshu; Liu, Binghe; Yang, Kang; Vollrath, Fritz; Xu, Jun

    2017-01-01

    Silkworm cocoon material is a natural composite consisting of silk fibres and sericin glues. Both domestic and wild silkworms produce cocoons but with different functionality - one selected by man for textile manufacture whereas the other selected by Nature to provide damage-tolerant housing. To understand the structure--property relationship of cocoons, we evaluated and compared the microstructure and mechanical properties of two representative cocoon walls. It appears that a "brittle and weak" composite is produced by domestic Bombyx mori (B. mori) while a "tough and strong" composite is made by wild Antheraea pernyi (A. pernyi). The superior mechanical performance of A. pernyi cocoons can be attributed to both the material properties and the fibre network microstructures. Failure mechanisms and different failure modes for cocoon fibre composites were also proposed. A finite element model revealed qualitatively the effect of fibre properties and inter-fibre bonding strength on the mechanical properties of the fibre network. It emerged that both good mechanical properties of fibres and robust inter-fibre bonding were required for tough and strong fibre composites. The new insights could inspire new designs of synthetic fibre composites with enhanced mechanical properties. Natural cocoons are an important group of natural fibre composites with versatile functionalities. Previous studies have focused on the diversity of cocoon species and different morphological and mechanical features. It was suggested that the cocoon network structure determined the final mechanical properties of the cocoon composite. Nevertheless, the full structure-propertyfunction relationships for the cocoon composite are not understood. By studying two distinct cocoon species with specific functionalities, we prove that the mechanical properties of two cocoons are determined by both network properties and fibre properties. A robust fibre network is the prerequisite, within which the good

  13. 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

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

    PubMed

    Etcheverry, Mariana; Barbosa, Silvia E

    2012-06-18

    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.

  15. Wave-Mechanical Properties of Stationary States.

    ERIC Educational Resources Information Center

    Holden, Alan

    This monograph is a review of the quantum mechanical concepts presented in two other monographs, "The Nature of Atoms" and "Bonds Between Atoms," by the same author. It is assumed the reader is familiar with these ideas. The monograph sketches only those aspects of quantum mechanics that are of most direct use in picturing and calculating the…

  16. 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...

  17. Decoupling Mechanical and Ion Transport Properties in Polymer Electrolyte Membranes

    NASA Astrophysics Data System (ADS)

    McIntosh, Lucas D.

    Polymer electrolytes are mixtures of a polar polymer and salt, in which the polymer replaces small molecule solvents and provides a dielectric medium so that ions can dissociate and migrate under the influence of an external electric field. Beginning in the 1970s, research in polymer electrolytes has been primarily motivated by their promise to advance electrochemical energy storage and conversion devices, such as lithium ion batteries, flexible organic solar cells, and anhydrous fuel cells. In particular, polymer electrolyte membranes (PEMs) can improve both safety and energy density by eliminating small molecule, volatile solvents and enabling an all-solid-state design of electrochemical cells. The outstanding challenge in the field of polymer electrolytes is to maximize ionic conductivity while simultaneously addressing orthogonal mechanical properties, such as modulus, fracture toughness, or high temperature creep resistance. The crux of the challenge is that flexible, polar polymers best-suited for polymer electrolytes (e.g., poly(ethylene oxide)) offer little in the way of mechanical robustness. Similarly, polymers typically associated with superior mechanical performance (e.g., poly(methyl methacrylate)) slow ion transport due to their glassy polymer matrix. The design strategy is therefore to employ structured electrolytes that exhibit distinct conducting and mechanically robust phases on length scales of tens of nanometers. This thesis reports a remarkably simple, yet versatile synthetic strategy---termed polymerization-induced phase separation, or PIPS---to prepare PEMs exhibiting an unprecedented combination of both high conductivity and high modulus. This performance is enabled by co-continuous, isotropic networks of poly(ethylene oxide)/ionic liquid and highly crosslinked polystyrene. A suite of in situ, time-resolved experiments were performed to investigate the mechanism by which this network morphology forms, and it appears to be tied to the

  18. Mechanical properties of a polyamide 6-reinforced PTFE composite

    NASA Astrophysics Data System (ADS)

    Li, J.

    2009-05-01

    Polytetrafluoroethylene (PTFE) blends with polyamide 6 (PA6) in various ratios were prepared in a corotating twin-screw extruder, where PTFE acted as a polymer matrix and PA6 as a disperse phase, and the morphology and mechanical properties of the blends were investigated by using SEM. With increasing content of PA6 in the blends, their flexural properties improved. The interfacial adhesion promoted the creation of an interphase between the PTFE and PA6 and led to improved mechanical properties of the material. The mechanical properties of the blends were optimum at 30 vol.% PA6.

  19. Investigation on mechanical properties of contemporary metallic bone plates: towards the development of composite bone plates.

    PubMed

    Hoque, M E; Zainal, N H; Syarif, J

    2008-07-01

    This study aims at investigating the mechanical properties of the contemporary metallic bone plates determining the effect of their length, width and thickness on the properties and compares with the composite bone plates. Three-points bending test was performed over the stainless steel plates of different length, width and thickness. The test results showed that different plates had different mechanical properties. However, the properties are still much higher than that of particular bones intended to be treated. Therefore, the reported findings strongly encourage developing composite bone plates with biocompatible polymers/fibers that would have modulated properties according to the requirements.

  20. 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...

  1. Mechanical and physical properties of plasma-sprayed stabilized zirconia

    NASA Technical Reports Server (NTRS)

    Siemers, P. A.; Mehan, R. L.

    1983-01-01

    Physical and mechanical properties were determined for plasma-sprayed MgO- or Y2O3-stabilized ZrO2 thermal barrier coatings. Properties were determined for the ceramic coating in both the freestanding condition and as-bonded to a metal substrate. The properties of the NiCrAlY bond coating were also investigated.

  2. Electronic, thermal and mechanical properties of carbon nanotubes.

    PubMed

    Dresselhaus, M S; Dresselhaus, G; Charlier, J C; Hernández, E

    2004-10-15

    A review of the electronic, thermal and mechanical properties of nanotubes is presented, with particular reference to properties that differ from those of the bulk counterparts and to potential applications that might result from the special structure and properties of nanotubes. Both experimental and theoretical aspects of these topics are reviewed.

  3. Mechanical properties of UV irradiated rat tail tendon (RTT) collagen.

    PubMed

    Sionkowska, Alina; Wess, Tim

    2004-04-01

    The mechanical properties of RTT collagen tendon before and after UV irradiation have been investigated by mechanical testing (Instron). Air-dried tendon were submitted to treatment with UV irradiation (wavelength 254 nm) for different time intervals. The changes in such mechanical properties as breaking strength and percentage elongation have been investigated. The results have shown, that the mechanical properties of the tendon were greatly affected by time of UV irradiation. Ultimate tensile strength and ultimate percentage elongation decreased after UV irradiation of the tendon. Increasing UV irradiation leads to a decrease in Young's modulus of the tendon.

  4. How divergence mechanisms influence disassortative mixing property in biology

    NASA Astrophysics Data System (ADS)

    Xu, Chunsui; Liu, Zengrong; Wang, Ruiqi

    2010-02-01

    The duplication-divergence mechanism of network growth has been widely investigated, especially in gene and protein networks. Both the duplication and divergence have a key role in biological network evolution. However, the relative roles of these mechanisms in the influence of disassortative property in protein interaction networks remain to be clarified. It has been shown that duplication can indeed make protein networks evolve towards disassortative networks. To make the relationship between the disassortative property and the duplication-divergence mechanism more clear, we further discuss how the divergence mechanism influences the disassortative property. We tested four different divergence mechanisms, i.e., node deletion, edge deletion, edge addition, and edge rewiring to study their effects on disassortative property. Our study highlights the crucial roles of different divergence evolution mechanisms.

  5. Mechanical properties of natural cartilage and tissue-engineered constructs.

    PubMed

    Little, Christopher James; Bawolin, Nahshon Kenneth; Chen, Xiongbiao

    2011-08-01

    There has been much research over the past two decades with the aim of engineering cartilage constructs for repairing or restoring damaged cartilage. To engineer healthy neocartilage, the constructs must have mechanical properties matching those of native cartilage as well as appropriate for the loading conditions of the joint. This article discusses the mechanical behavior of native cartilage and surveys different types of tensile, compressive, and shear tests with their limitations. It also comprehensively reviews recent work and achievements in developing the mathematical models representing the mechanical properties of both native and engineered cartilage. Different methods for enhancing the mechanical properties of engineered cartilage are also discussed, including scaffold design, mechanical stimulation, and chemical stimulation. This article concludes with recommendations for future research aimed at achieving engineered cartilage with mechanical properties matching those found in native cartilage.

  6. Lunar soil properties and soil mechanics

    NASA Technical Reports Server (NTRS)

    Mitchell, J. K.; Houston, W. N.

    1974-01-01

    The long-range objectives were to develop methods of experimentation and analysis for the determination of the physical properties and engineering behavior of lunar surface materials under in situ environmental conditions. Data for this purpose were obtained from on-site manned investigations, orbiting and softlanded spacecraft, and terrestrial simulation studies. Knowledge of lunar surface material properties are reported for the development of models for several types of lunar studies and for the investigation of lunar processes. The results have direct engineering application for manned missions to the moon.

  7. Scanning Probe Evaluation of Electronic, Mechanical and Structural Material Properties

    NASA Astrophysics Data System (ADS)

    Virwani, Kumar

    2011-03-01

    We present atomic force microscopy (AFM) studies of a range of properties from three different classes of materials: mixed ionic electronic conductors, low-k dielectrics, and polymer-coated magnetic nanoparticles. (1) Mixed ionic electronic conductors are being investigated as novel diodes to drive phase-change memory elements. Their current-voltage characteristics are measured with direct-current and pulsed-mode conductive AFM (C-AFM). The challenges to reliability of the C-AFM method include the electrical integrity of the probe, the sample and the contacts, and the minimization of path capacitance. The role of C-AFM in the optimization of these electro-active materials will be presented. (2) Low dielectric constant (low-k) materials are used in microprocessors as interlayer insulators, a role directly affected by their mechanical performance. The mechanical properties of nanoporous silicate low-k thin films are investigated in a comparative study of nanomechanics measured by AFM and by traditional nanoindentation. Both methods are still undergoing refinement as reliable analytical tools for determining nanomechanical properties. We will focus on AFM, the faster of the two methods, and its developmental challenges of probe shape, cantilever force constant, machine compliance and calibration standards. (3) Magnetic nanoparticles are being explored for their use in patterned media for magnetic storage. Current methods for visualizing the core-shell structure of polymer-coated magnetic nanoparticles include dye-staining the polymer shell to provide contrast in transmission electron microscopy. AFM-based fast force-volume measurements provide direct visualization of the hard metal oxide core within the soft polymer shell based on structural property differences. In particular, the monitoring of adhesion and deformation between the AFM tip and the nanoparticle, particle-by-particle, provides a reliable qualitative tool to visualize core-shell contrast without the use

  8. The Effect of Defects on Mechanical Properties and Failure Mechanisms of Graphene

    NASA Astrophysics Data System (ADS)

    Willman, Jonathan; Gonzalez, Joseph; Perriot, Romain; Oleynik, Ivan

    Recent experiments involving nanoindentation of graphene have demonstrated counterintuitive increasing of Young's modulus with increasing concentrations of point defects in graphene. To fully resolve this controversy we perform large-scale molecular dynamics simulations of graphene nanoindentation. The relaible description of interatomic interactions is achieved by using recently developed screened environment-dependent bond order (SED-REBO) potential. The elastic properties of the defective graphene, the breaking strength and the mechanisms of fracture under indenter are investigated as a function of defect concentration and other factors specific to Atomic Force Microscopy (AFM) nanoindentation experiments.

  9. Astronaut John Glenn tests balance mechanism performance

    NASA Image and Video Library

    1962-02-01

    S64-14849 (1962) --- Astronaut John H. Glenn Jr.'s balance mechanism (semi-circular-canals) is tested by running cool water into his ear and measuring effect on eye motions (nystagmus). Photo credit: NASA

  10. Integrated design of castings: effect of porosity on mechanical performance

    NASA Astrophysics Data System (ADS)

    Hardin, R. A.; Beckermann, C.

    2012-07-01

    Porosity can significantly reduce the strength and durability of castings in service. An integrated design approach has been developed where casting simulation is combined with mechanical performance simulations. Predictions of the porosity distribution from the casting process simulation are transferred to and used in stress and fatigue life simulations. Thus, the effect of casting quality on service performance can be evaluated. Results of a study are presented where the measured porosity distribution in cast steel specimens is transferred to an elasto-plastic finite-element stress analysis model. Methods are developed to locally reduce the mechanical properties according to the porosity present, without having to resolve individual pores. Plastic deformation is modeled using porous metal plasticity theory. The predictions are compared to tensile measurements performed on the specimens. The complex deformations and the reductions in the ductility of the specimens due to porosity are predicted well. The predicted stresses are transferred to a fatigue analysis code that takes the porosity distribution into account as well. The measured and predicted fatigue lives are also in good agreement. Finally, the results of a case study are presented that illustrate the utility of the present integrated approach in optimizing the design of a steel casting.

  11. Investigation of the Mechanical Performance of Compliant Thermal Barriers

    NASA Technical Reports Server (NTRS)

    DeMange, Jeffrey J.; Bott, Robert J.; Dunlap, Patrick H.

    2011-01-01

    Compliant thermal barriers play a pivotal role in the thermal protection systems of advanced aerospace vehicles. Both the thermal properties and mechanical performance of these barriers are critical in determining their successful implementation. Due to the custom nature of many thermal barriers, designers of advanced spacecraft have little guidance as to the design, selection, and implementation of these elements. As part of an effort to develop a more fundamental understanding of the interrelationship between thermal barrier design and performance, mechanical testing of thermal barriers was conducted. Two different types of thermal barriers with several core insulation density levels ranging from 62 to 141 kg/cu m were investigated. Room-temperature compression tests were conducted on samples to determine load performance and assess thermal barrier resiliency. Results showed that the loading behavior of these thermal barriers was similar to other porous, low-density, compliant materials, such as elastomeric foams. Additionally, the insulation density level had a significant non-linear impact on the stiffness and peak loads of the thermal barriers. In contrast, neither the thermal barrier type nor the level of insulation density significantly influenced the room-temperature resiliency of the samples.

  12. Attention Theory and Mechanisms for Skilled Performances.

    DTIC Science & Technology

    1982-07-01

    ADA’V69 ILLINO IS UNIV CHAMPAIGN HUMAN ATTENTION RESEARCH LAS F/G 5/10 A IR ATTENTION THORY AND M ECHANISMS FOR SKILLED PERFORMANCES(U) UNISqIFO 2...TYPE OF REPORT & PERIOD COVERED Attent ion Theory and Mechanismrs for Technical Report .SkiledPerfrmacesS. PERFORMING ORG. REPORT NUMBER 7. AU THOR(a) S...WORDS (Geiffere en revere, aide if necessary end Identfy by block niumber) - Attention , skilled performance, human information processing, dual process

  13. Physical and mechanical properties of icebergs

    SciTech Connect

    Gammon, P.H.; Bobby, W.; Gagnon, R.E.; Russell, W.E.

    1983-05-01

    Physical and mechanical characteristics of iceberg ice were studied from samples collected near the shores of eastern Newfoundland. Although the physical characteristics show considerable diversity, iceberg ice has some common features and is generally porous, lacks significant concentrations of dissolved materials, contains internal cracks and has an irregular interlocking grain structure. A review of mechanical testing of ice was carried out and an experimental setup was devised to reduce effects of improper contact between specimen and loading apparatus. Uniaxial compressive strength for iceberg ice was determined and compared with that for lake ice. The strength of iceberg ice was higher than that of lake ice but Young's Modulus for lake ice was higher.

  14. Mechanical Properties of Normal and Diseased Cerebrovascular System

    PubMed Central

    Ebrahimi, Ali P.

    2009-01-01

    Background: Blood vessel mechanics has traditionally been of interest to researchers and clinicians. Changes in mechanical properties of arteries have been associated with various diseases. Objective: To provide a comprehensive review directed towards understanding the basic biomechanical properties of cerebral arteries under normal and diseased conditions. Methods: Literature review supplemented by personal knowledge. Results: The mechanical properties of vascular tissue may depend on several factors including macromolecular volume fraction, molecular orientation, and volume or number of cells such as smooth muscle cells. Mechanical properties of a blood vessel have been characterized using different methods such as in vitro tensile testing, non-invasive ultrasound examination, and mathematical models. Experiments are complicated by the variation in properties and content of materials that make up the vessel wall and more challenging as the size of the vessel of interest decreases. Therapeutic interventions aiming to alter the mechanical response are either pharmaceutical: including calcium channel blockers, angiotensin converting enzyme inhibitors (ACEI), angiotensin receptor blockers (ARB), and β-blockers; or, mechanical interventions such as angioplasty, stent placement, mechanical thrombectomy, or embolization procedures. Conclusion: It is apparent from the literature that macromolecular and cellular mechanics of blood vessels are not fully understood. Therefore, further studies are necessary to better understand contribution of these mechanisms to the overall mechanics of the vascular tissue. PMID:22518247

  15. Mechanical and Electrical Properties of Aluminum/Epoxy Nanocomposites

    NASA Astrophysics Data System (ADS)

    Dong, Lina; Zhou, Wenying; Sui, Xuezhen; Wang, Zijun; Cai, Huiwu; Wu, Peng; Zhang, Yating; Zhou, Anning

    2016-11-01

    Surface-modified self-passivated aluminum (Al) nanoparticles were used for reinforcing epoxy (EP) resin, and the curing behavior, mechanical and electrical properties of the Al/EP nanocomposites were investigated. The incorporation of Al nanoparticles into EP significantly decreases the cure reaction enthalpy of the nancomposites, and the apparent activation energy of Al/EP systems is 64.96 kJ/mol. The coefficient of thermal expansion of the nanocomposites decreases with increasing the Al loading due to the strong interaction between the Al and the EP matrix. The storage modulus of the nanocomposites increases continuously with Al content, whereas, the glass transition temperature declines slightly. With increasing the Al content, the tensile modulus, flexural modulus and compressive modulus of the nanocomposites increase continuously compared with the neat one. The mechanical properties are improved by Al nanoparticles at low Al contents. The best overall dielectric and electrical performance are achieved about at 1 wt.% of Al concentration. The enhanced dielectric breakdown strength is mainly related to the insulating alumina shell on the surface of core Al and the strong interfacial interactions.

  16. Mechanical properties of continuously spun fibers of carbon nanotubes.

    PubMed

    Motta, Marcelo; Li, Ya-Li; Kinloch, Ian; Windle, Alan

    2005-08-01

    We report on the mechanical properties of fibers consisting of pure carbon nanotube fibers directly spun from an aerogel formed during synthesis by chemical vapor deposition. The continuous withdrawal of product from the gas phase imparts a high commercial potential to the process, either for the production of particularly strong fibers or for the economic production of bulk quantities of carbon nanotubes. Tensile tests were performed on fibers produced from the dissociation of three different hydrocarbons, namely, ethanol, ethylene glycol, and hexane, with a range of iron (catalyst) concentrations. The conditions were chosen to lie within the range known to enable satisfactory continuous spinning, the iron concentration being varied within this range. Increasing proportions of single wall nanotubes were found as the iron concentration was decreased, conditions which also produced fibers of best strength and stiffness. The maximum tensile strength obtained was 1.46 GPa (equivalent to 0.70 N/tex assuming a density of 2.1 g/cm(3)). The experiments indicate that significant improvements in the mechanical properties can be accomplished by optimizing the process conditions.

  17. Robotic palpation and mechanical property characterization for abnormal tissue localization.

    PubMed

    Ahn, Bummo; Kim, Yeongjin; Oh, Cheol Kyu; Kim, Jung

    2012-09-01

    Palpation is an intuitive examination procedure in which the kinesthetic and tactile sensations of the physician are used. Although it has been widely used to detect and localize diseased tissues in many clinical fields, the procedure is subjective and dependent on the experience of the individual physician. Palpation results and biomechanics-based mechanical property characterization are possible solutions that can enable the acquisition of objective and quantitative information on abnormal tissue localization during diagnosis and surgery. This paper presents an integrated approach for robotic palpation combined with biomechanical soft tissue characterization. In particular, we propose a new palpation method that is inspired by the actual finger motions that occur during palpation procedures. To validate the proposed method, robotic palpation experiments on silicone soft tissue phantoms with embedded hard inclusions were performed and the force responses of the phantoms were measured using a robotic palpation system. Furthermore, we carried out a numerical analysis, simulating the experiments and estimating the objective and quantitative properties of the tissues. The results indicate that the proposed approach can differentiate diseased tissue from normal tissue and can characterize the mechanical information of diseased tissue, which means that this method can be applied as a means of abnormality localization to diagnose prostate cancers.

  18. Investigation into mechanical properties of bone and its main constituents

    NASA Astrophysics Data System (ADS)

    Evdokimenko, Ekaterina

    Bone is a hierarchically structured natural composite material, consisting of organic phase (type-I collagen), inorganic phase (hydroxyapatite), and water. Studies of the two main bone constituents, utilizing controlled demineralization and deproteinization, can shed light on mineral-collagen interaction which makes bone such a unique biological material. This knowledge is necessary for computational analysis of bone structure to identify preferential sites in the collagen matrix and mineral network that degrade more easily. The main goal of this work is to develop a comprehensive picture of mechanical properties of bone and its main constituents. Following the Introduction, Chapter 2 presents an investigation of microstructure and compressive mechanical properties of bovine femur cortical bone carried out on completely demineralized, completely deproteinized, and untreated bone samples in three anatomical directions. Anisotropic nature of bone was clearly identified in all cases. Extra levels of porosity along with microstructural differences for the three directions were found to be the main sources of the anisotropy. In Chapter 3, a new theoretical model of cortical and trabecular bone as composite materials with hierarchical structure spanning from nanometer (collagen-mineral) level to millimeter (bone) level was developed. Compression testing was performed on untreated, demineralized, and deproteinized cortical and trabecular bovine femur bone samples to verify the model. The experimental data were compared with theoretical predictions; excellent agreement was found between the theory and experiments for all bone phases. Optical microscopy, scanning electron microscopy, and micro-computed tomography techniques were applied to characterize the structure of the samples at multiple length scales and provide further inputs for the modeling. Chapter 4 presents a comparative study of mechanical properties, microstructure, and porosity of mature and young bovine

  19. Effective Mechanical Properties of Fuzzy Fiber Composites

    DTIC Science & Technology

    2012-03-16

    fibers’’. Numerical examples of compositesmade of epoxy resin , carbonfibers and carbon nanotubes are presented and the impact of the carbon nanotubes...allows us to compute effective properties of composites with multiple types of ??fuzzy fibers??. Numerical examples of composites made of epoxy resin ...length (Fig. 1 in [42]). The CNTs have inter- nal radius 0.51 nm and external radius 0.85 nm. The ‘‘fuzzy fibers’’ are embedded in EPIKOTE 862 resin . The

  20. Composite propellant technology research: Mechanical property characterization

    NASA Technical Reports Server (NTRS)

    Bower, Mark V.

    1991-01-01

    Proof for the existence of a single Poisson's ratio function in isotropic linear viscoelastic materials is presented. An in-depth discussion is given of three dimensional viscoelastic material properties and their relationships to linear isotropic and orthotropic viscoelastic materials. A discussion of the alternate invariant definition as used by Abaqus and how it relates to the form used by Dr. S. Peng is presented.

  1. Ion plated gold films: Properties, tribological behavior and performance

    NASA Technical Reports Server (NTRS)

    Spalvins, Talivaldis

    1987-01-01

    The glow discharge energizing favorably modifies and controls the coating/substrate adherence and the nucleation and growth sequence of ion plated gold films. As a result the adherence, coherence, internal stresses, and morphology of the films are significantly improved. Gold ion plated films because of their graded coating/substrate interface and fine uniform densely packed microstructure not only improve the tribological properties but also induce a surface strengthening effect which improves the mechanical properties such as yield, tensile, and fatigue strength. Consequently significant improvements in the tribological performance of ion plated gold films as compared to vapor deposited gold films are shown in terms of decreased friction/wear and prolonged endurance life.

  2. Supramolecular Polymer Nanocomposites - Improvement of Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Hinricher, Jesse; Neikirk, Colin; Priestley, Rodney

    2015-03-01

    Supramolecular polymers differ from traditional polymers in that their repeat units are connected by hydrogen bonds that can reversibly break and form under various stimuli. They can be more easily recycled than conventional materials, and their highly temperature dependent viscosities result in reduced energy consumption and processing costs. Furthermore, judicious selection of supramolecular polymer architecture and functionality allows the design of advanced materials including shape memory and self-healing materials. Supramolecular polymers have yet to see widespread use because they can't support much weight due to their inherent mechanical weakness. In order to address this issue, the mechanical strength of supramolecular polymer nanocomposites based on ureidopyrmidinone (UPy) telechelic poly(caprolactone) doped with surface activated silica nanoparticles was investigated by tensile testing and dynamic mechanical analysis. The effects of varying amounts and types of nanofiller surface functionality were investigated to glean insight into the contributions of filler-filler and filler-matrix interactions to mechanical reinforcement in supramolecular polymer nanocomposites. MRSEC NSF DMR 0819860 (PI: Prof. N. Phuan Ong) REU Site Grant: NSF DMR-1156422 (PI: Prof. Mikko Haataja)

  3. Mechanical properties of artificial tracheas composed of a mesh cylinder and a spiral stent.

    PubMed

    Kawaguchi, S; Nakamura, T; Shimizu, Y; Masuda, T; Takigawa, T; Liu, Y; Ueda, H; Sekine, T; Matsumoto, K

    2001-12-01

    Much work has been done on the materials used for mesh-type artificial tracheas, but a precise mechanical evaluation of these structures has not yet been performed. In the present study, we determined the mechanical properties of typical mesh-type artificial tracheas and compared them with those of native trachea. Four types of artificial trachea were made and used for the mechanical tests. The basic frame of all the specimens was composed of a mesh cylinder and a spiral stent. The specimen whose mesh was sealed with collagen sponge showed almost the same behavior in the force-strain curve under compression, suggesting that collagen sealing has little effect on mechanical properties. Agreement between measured and estimated mechanical properties was good, especially in the low strain region, suggesting that artificial tracheas can be designed in terms of mechanical properties by mainly considering the basic frame structure.

  4. Mechanical and thermal properties of bulk ZrB2

    NASA Astrophysics Data System (ADS)

    Nakamori, Fumihiro; Ohishi, Yuji; Muta, Hiroaki; Kurosaki, Ken; Fukumoto, Ken-ichi; Yamanaka, Shinsuke

    2015-12-01

    ZrB2 appears to have formed in the fuel debris at the Fukushima Daiichi nuclear disaster site, through the reaction between Zircaloy cladding materials and the control rod material B4C. Since ZrB2 has a high melting point of 3518 K, the ceramic has been widely studied as a heat-resistant material. Although various studies on the thermochemical and thermophysical properties have been performed for ZrB2, significant differences exist in the data, possibly due to impurities or the porosity within the studied samples. In the present study, we have prepared a ZrB2 bulk sample with 93.1% theoretical density by sintering ZrB2 powder. On this sample, we have comprehensively examined the thermal and mechanical properties of ZrB2 by the measurement of specific heat, ultrasonic sound velocities, thermal diffusivity, and thermal expansion. Vickers hardness and fracture toughness were also measured and found to be 13-23 GPa and 1.8-2.8 MPa m0.5, respectively. The relationships between these properties were carefully examined in the present study.

  5. Solar Sail Material Performance Property Response to Space Environmental Effects

    NASA Technical Reports Server (NTRS)

    Edwards, David L.; Semmel, Charles; Hovater, Mary; Nehls, Mary; Gray, Perry; Hubbs, Whitney; Wertz, George

    2004-01-01

    The National Aeronautics and Space Administration's (NASA) Marshall Space Flight Center (MSFC) continues research into the utilization of photonic materials for spacecraft propulsion. Spacecraft propulsion, using photonic materials, will be achieved using a solar sail. A solar sail operates on the principle that photons, originating from the sun, impart pressure to the sail and therefore provide a source for spacecraft propulsion. The pressure imparted to a solar sail can be increased, up to a factor of two, if the sun-facing surface is perfectly reflective. Therefore, these solar sails are generally composed of a highly reflective metallic sun-facing layer, a thin polymeric substrate and occasionally a highly emissive back surface. Near term solar sail propelled science missions are targeting the Lagrange point 1 (Ll) as well as locations sunward of L1 as destinations. These near term missions include the Solar Polar Imager and the L1 Diamond. The Environmental Effects Group at NASA s Marshall Space Flight Center (MSFC) continues to actively characterize solar sail material in preparation for these near term solar sail missions. Previous investigations indicated that space environmental effects on sail material thermo-optical properties were minimal and would not significantly affect the propulsion efficiency of the sail. These investigations also indicated that the sail material mechanical stability degrades with increasing radiation exposure. This paper will further quantify the effect of space environmental exposure on the mechanical properties of candidate sail materials. Candidate sail materials for these missions include Aluminum coated Mylar[TM], Teonex[TM], and CPl (Colorless Polyimide). These materials were subjected to uniform radiation doses of electrons and protons in individual exposures sequences. Dose values ranged from 100 Mrads to over 5 Grads. The engineering performance property responses of thermo-optical and mechanical properties were

  6. Solar Sail Material Performance Property Response to Space Environmental Effects

    NASA Technical Reports Server (NTRS)

    Edwards, David L.; Semmel, Charles; Hovater, Mary; Nehls, Mary; Gray, Perry; Hubbs, Whitney; Wertz, George

    2004-01-01

    The National Aeronautics and Space Administration's (NASA) Marshall Space Flight Center (MSFC) continues research into the utilization of photonic materials for spacecraft propulsion. Spacecraft propulsion, using photonic materials, will be achieved using a solar sail. A solar sail operates on the principle that photons, originating from the sun, impart pressure to the sail and therefore provide a source for spacecraft propulsion. The pressure imparted to a solar sail can be increased, up to a factor of two, if the sun-facing surface is perfectly reflective. Therefore, these solar sails are generally composed of a highly reflective metallic sun-facing layer, a thin polymeric substrate and occasionally a highly emissive back surface. Near term solar sail propelled science missions are targeting the Lagrange point 1 (Ll) as well as locations sunward of L1 as destinations. These near term missions include the Solar Polar Imager and the L1 Diamond. The Environmental Effects Group at NASA s Marshall Space Flight Center (MSFC) continues to actively characterize solar sail material in preparation for these near term solar sail missions. Previous investigations indicated that space environmental effects on sail material thermo-optical properties were minimal and would not significantly affect the propulsion efficiency of the sail. These investigations also indicated that the sail material mechanical stability degrades with increasing radiation exposure. This paper will further quantify the effect of space environmental exposure on the mechanical properties of candidate sail materials. Candidate sail materials for these missions include Aluminum coated Mylar[TM], Teonex[TM], and CPl (Colorless Polyimide). These materials were subjected to uniform radiation doses of electrons and protons in individual exposures sequences. Dose values ranged from 100 Mrads to over 5 Grads. The engineering performance property responses of thermo-optical and mechanical properties were

  7. Automotive Mechanics Occupational Performance Survey. Interim Report.

    ERIC Educational Resources Information Center

    Borcher, Sidney D.; Leiter, Paul B.

    The purpose of this federally-funded interim report is to present the results of a task inventory analysis survey of automotive mechanics completed by project staff within the Instructional Systems Design Program at the Center for Vocational and Technical Education. Intended for use in curriculum development for vocational education programs in…

  8. 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.

  9. Optical and mechanical properties of cellulose nanopaper structures

    NASA Astrophysics Data System (ADS)

    Tsalagkas, Dimitrios; Zhai, Lindong; Kim, Hyun Chan; Kim, Jaehwan

    2017-04-01

    The objectives of this study are to prepare and investigate the optical and tensile properties of the obtained cellulose nanopaper structures. A ball mill mechanical pretreatment combined with a wet pulverization process by using an aqueous counter collision machine were used to extract CNFs from softwood and hardwood bleached kraft pulps. Cellulose nanofiber (CNF) nanopapers were fabricated via vacuum filtration and oven drying method. The mechanical and optical properties of the fabricated nanopaper were investigated by using tensile test and UV-vis spectrometer. Results have shown that the softwood sample demonstrated better mechanical properties than the hardwood sample. UV-vis transmittance measurements did not indicate significant differences.

  10. Fine-Scale Mechanical Properties of Sliding Solids.

    DTIC Science & Technology

    1987-02-28

    UNCLASSIFIED DRJ45-4-C-0006 F/0 26/11 ML E~Em***smRn loI 1.05 w4 AV. -w q ! WvI% %111.2nE~% 03TI ElLE CP - 1NE-CALE MECHANICAL PROPERTIES OF - 0 SLIDING...LAI 4Th Approved for Public Release; distribution unlimited f 4,rm 6mw "%U FINE-SCALE MECHANICAL PROPERTIES OF SLIDING SOLIDS Final Technical Report by...experiments specifically designed to -investigate the mechanical properties of materials at the submicroscopic level. The first part deals with

  11. Geometrical and mechanical properties control actin filament organization.

    PubMed

    Letort, Gaëlle; Politi, Antonio Z; Ennomani, Hajer; Théry, Manuel; Nedelec, Francois; Blanchoin, Laurent

    2015-05-01

    The different actin structures governing eukaryotic cell shape and movement are not only determined by the properties of the actin filaments and associated proteins, but also by geometrical constraints. We recently demonstrated that limiting nucleation to specific regions was sufficient to obtain actin networks with different organization. To further investigate how spatially constrained actin nucleation determines the emergent actin organization, we performed detailed simulations of the actin filament system using Cytosim. We first calibrated the steric interaction between filaments, by matching, in simulations and experiments, the bundled actin organization observed with a rectangular bar of nucleating factor. We then studied the overall organization of actin filaments generated by more complex pattern geometries used experimentally. We found that the fraction of parallel versus antiparallel bundles is determined by the mechanical properties of actin filament or bundles and the efficiency of nucleation. Thus nucleation geometry, actin filaments local interactions, bundle rigidity, and nucleation efficiency are the key parameters controlling the emergent actin architecture. We finally simulated more complex nucleation patterns and performed the corresponding experiments to confirm the predictive capabilities of the model.

  12. Geometrical and Mechanical Properties Control Actin Filament Organization

    PubMed Central

    Ennomani, Hajer; Théry, Manuel; Nedelec, Francois; Blanchoin, Laurent

    2015-01-01

    The different actin structures governing eukaryotic cell shape and movement are not only determined by the properties of the actin filaments and associated proteins, but also by geometrical constraints. We recently demonstrated that limiting nucleation to specific regions was sufficient to obtain actin networks with different organization. To further investigate how spatially constrained actin nucleation determines the emergent actin organization, we performed detailed simulations of the actin filament system using Cytosim. We first calibrated the steric interaction between filaments, by matching, in simulations and experiments, the bundled actin organization observed with a rectangular bar of nucleating factor. We then studied the overall organization of actin filaments generated by more complex pattern geometries used experimentally. We found that the fraction of parallel versus antiparallel bundles is determined by the mechanical properties of actin filament or bundles and the efficiency of nucleation. Thus nucleation geometry, actin filaments local interactions, bundle rigidity, and nucleation efficiency are the key parameters controlling the emergent actin architecture. We finally simulated more complex nucleation patterns and performed the corresponding experiments to confirm the predictive capabilities of the model. PMID:26016478

  13. Mechanical Properties of Triaxial Braided Carbon/Epoxy Composites

    NASA Technical Reports Server (NTRS)

    Bowman, C. L.; Roberts, G. D.; Braley, M. S.; Xie, M.; Booker, M. J.

    2003-01-01

    In an on-going effort to increase the safety and efficiency of turbine engines, the National Aeronautics and Space Administration is exploring lightweight alternatives to the metal containment structures that currently encase commercial jet engines. Epoxy reinforced with braided carbon fibers is a candidate structural material which may be suitable for an engine case. This paper reports flat-coupon mechanical-property experiments performed to compliment previously reported subcomponent impact testing and analytical simulation of containment structures. Triaxial-braid T700/5208 epoxy and triaxial-braid T700/M36 toughened epoxy composites were evaluated. Also, two triaxial-braid architectures (0 +/- 60 deg., 0 +/- 45 deg.) with the M36 resin were evaluated through tension, compression, and shear testing. Tensile behavior was compared between standard straight-sided specimens (ASTM D3039) and bowtie specimens. Both double-notch shear (ASTM D3846) and Iosepescu (ASTM D5379) tests were performed as well. The M36/0 +/- 45 deg. configuration yield the best response when measurements were made parallel to the axial tows. Conversely, the M36/0 +/- 60 deg. configuration was best when measurements were made perpendicular to the axial tows. The results were used to identify critical properties and to augment the analysis of impact experiments.

  14. Mechanical Properties of Triaxial Braided Carbon/Epoxy Composites

    NASA Technical Reports Server (NTRS)

    Bowman, C. L.; Roberts, G. D.; Braley, M. S.; Xie, M.; Booker, M. J.

    2003-01-01

    In an on-going effort to increase the safety and efficiency of turbine engines, the National Aeronautics and Space Administration is exploring lightweight alternatives to the metal containment structures that currently encase commercial jet engines. Epoxy reinforced with braided carbon fibers is a candidate structural material which may be suitable for an engine case. This paper reports flat-coupon mechanical-property experiments performed to compliment previously reported subcomponent impact testing and analytical simulation of containment structures. Triaxial-braid T700/5208 epoxy and triaxial-braid T700h436 toughened epoxy composites were evaluated. Also, two triaxial-braid architectures (0 degrees plus or minus 60 degrees, and 0 degrees plus or minus 45 degrees) with the M36 resin were evaluated through tension, compression, and shear testing. Tensile behavior was compared between standard straight-sided specimens (ASTM D3039) and bow-tie specimens. Both double-notch shear (ASTM D3846) and Iosepescu (ASTM D5379) tests were performed as well. The M36/O degrees plus or minus 45 degrees configuration yield the best response when measurements were made parallel to the axial tows. Conversely, the M36/0 degrees plus or minus 60 degrees configuration was best when measurements were made perpendicular to the axial tows. The results were used to identify critical properties and to augment the analysis of impact experiments.

  15. Properties and Performance of Alkali-Activated Concrete

    NASA Astrophysics Data System (ADS)

    Thomas, Robert J.

    Alkali-activated concrete (AAC) made with industrial byproducts as the sole binder is rapidly emerging as a sustainable alternative to ordinary portland cement concrete (PCC). Despite its exemplary mechanical performance and durability, there remain several barriers to widespread commercialization of AAC. This dissertation addresses several of these barriers. Mathematical models are proposed which efficiently and accurately predict the compressive strength of AAC as a function of activator composition, binder type, and curing condition. The relationships between compressive strength and other mechanical properties (i.e., tensile strength and modulus of elasticity) are discussed, as are stress-strain relationships. Several aspects related to the durability of AAC are also discussed, including dimensional stability under drying conditions, alkali-silica reactivity, and chloride permeability. The results of these experimental investigations are disseminated in the context of real-world applicability.

  16. The mechanical and strength properties of diamond.

    PubMed

    Field, J E

    2012-12-01

    Diamond is an exciting material with many outstanding properties; see, for example Field J E (ed) 1979 The Properties of Diamond (London: Academic) and Field J E (ed) 1992 The Properties of Natural and Synthetic Diamond (London: Academic). It is pre-eminent as a gemstone, an industrial tool and as a material for solid state research. Since natural diamonds grew deep below the Earth's surface before their ejection to mineable levels, they also contain valuable information for geologists. The key to many of diamond's properties is the rigidity of its structure which explains, for example, its exceptional hardness and its high thermal conductivity. Since 1953, it has been possible to grow synthetic diamond. Before then, it was effectively only possible to have natural diamond, with a small number of these found in the vicinity of meteorite impacts. Techniques are now available to grow gem quality synthetic diamonds greater than 1 carat (0.2 g) using high temperatures and pressures (HTHP) similar to those found in nature. However, the costs are high, and the largest commercially available industrial diamonds are about 0.01 carat in weight or about 1 mm in linear dimension. The bulk of synthetic diamonds used industrially are 600 µm or less. Over 75% of diamond used for industrial purposes today is synthetic material. In recent years, there have been two significant developments. The first is the production of composites based on diamond; these materials have a significantly greater toughness than diamond while still maintaining very high hardness and reasonable thermal conductivity. The second is the production at low pressures by metastable growth using chemical vapour deposition techniques. Deposition onto non-diamond substrates was first demonstrated by Spitsyn et al 1981 J. Cryst. Growth 52 219-26 and confirmed by Matsumoto et al 1982 Japan J. Appl. Phys. 21 L183-5. These developments have added further to the versatility of diamond. Two other groups of

  17. The mechanical and strength properties of diamond

    NASA Astrophysics Data System (ADS)

    Field, J. E.

    2012-12-01

    Diamond is an exciting material with many outstanding properties; see, for example Field J E (ed) 1979 The Properties of Diamond (London: Academic) and Field J E (ed) 1992 The Properties of Natural and Synthetic Diamond (London: Academic). It is pre-eminent as a gemstone, an industrial tool and as a material for solid state research. Since natural diamonds grew deep below the Earth's surface before their ejection to mineable levels, they also contain valuable information for geologists. The key to many of diamond's properties is the rigidity of its structure which explains, for example, its exceptional hardness and its high thermal conductivity. Since 1953, it has been possible to grow synthetic diamond. Before then, it was effectively only possible to have natural diamond, with a small number of these found in the vicinity of meteorite impacts. Techniques are now available to grow gem quality synthetic diamonds greater than 1 carat (0.2 g) using high temperatures and pressures (HTHP) similar to those found in nature. However, the costs are high, and the largest commercially available industrial diamonds are about 0.01 carat in weight or about 1 mm in linear dimension. The bulk of synthetic diamonds used industrially are 600 µm or less. Over 75% of diamond used for industrial purposes today is synthetic material. In recent years, there have been two significant developments. The first is the production of composites based on diamond; these materials have a significantly greater toughness than diamond while still maintaining very high hardness and reasonable thermal conductivity. The second is the production at low pressures by metastable growth using chemical vapour deposition techniques. Deposition onto non-diamond substrates was first demonstrated by Spitsyn et al 1981 J. Cryst. Growth 52 219-26 and confirmed by Matsumoto et al 1982 Japan J. Appl. Phys. 21 L183-5. These developments have added further to the versatility of diamond. Two other groups of materials

  18. The Effect of Aptitude and Experience on Mechanical Job Performance.

    ERIC Educational Resources Information Center

    Mayberry, Paul W.; Carey, Neil B.

    1997-01-01

    The validity of the Armed Services Vocational Aptitude Battery (ASVAB) in predicting mechanical job performance was studied with 891 automotive and 522 helicopter mechanics. The mechanical maintenance component of the ASVAB predicted hands-on performance, job knowledge, and training grades quite well, but experience was more predictive of…

  19. Mechanical properties of intermediate filament proteins

    PubMed Central

    Charrier, Elisabeth E.; Janmey, Paul A.

    2016-01-01

    Purified intermediate filament proteins can be reassembled in vitro to produce polymers closely resembling those found in cells, and these filament form viscoelastic gels. The crosslinks holding IFs together in the network include specific bonds between polypeptides extending from the filament surface and ionic interactions mediated by divalent cations. IF networks exhibit striking non-linear elasticity with stiffness, as quantified by shear modulus, increasing an order of magnitude as the networks are deformed to large stains resembling those that soft tissues undergo in vivo. Individual Ifs can be stretched to more than 2 or 3 times their resting length without breaking. At least ten different rheometric methods have been used to quantify the viscoelasticity of IF networks over a wide range of timescales and strain magnitudes. The mechanical roles of different classes of IF on mesenchymal and epithelial cells in culture have also been studied by an even wider range of microrheological methods. These studies have documented the effects on cell mechanics when IFs are genetically or pharmacologically disrupted or when normal or mutant IF proteins are exogenously expressed in cells. Consistent with in vitro rheology, the mechanical role of IFs is more apparent as cells are subjected to larger and more frequent deformations. PMID:26795466

  20. Mechanical properties of alumina porcelain during heating

    NASA Astrophysics Data System (ADS)

    Šín, Peter; Podoba, Rudolf; ŠtubÅa, Igor; Trník, Anton

    2014-11-01

    The mechanical strength and Young's modulus of green alumina porcelain (50 wt. % of kaolin, 25 wt. % of Al2O3, and 25 wt. % of feldspar) were measured during heating up to 900 °C and 1100 °C, respectively. To this end, we used the three point-bending method and modulated force thermomechanical analysis (mf-TMA). The loss liberation - of the physically bound water (20 - 250 °C) strengthens the sample and Young's modulus increases its values significantly. The dehydroxylation that takes place in the range of 400 - 650 °C causes a slight decrease in Young's modulus. On the other hand, the mechanical strength slightly increases in this temperature range, although it has a sudden drop at 420 °C. Beyond the dehydroxylation range, above 650 °C, both Young's modulus and mechanical strength increase. Above 950 °C, a sharp increase of Young's modulus is caused by the solid-state sintering and the new structure created by the high-temperature reactions in metakaolinite.

  1. Quantifying tissue mechanical properties using photoplethysmography

    SciTech Connect

    Akl, Tony; Wilson, Mark A.; Ericson, Milton Nance; Cote, Gerard L.

    2014-01-01

    Photoplethysmography (PPG) is a non-invasive optical method that can be used to detect blood volume changes in the microvascular bed of tissue. The PPG signal comprises two components; a pulsatile waveform (AC) attributed to changes in the interrogated blood volume with each heartbeat, and a slowly varying baseline (DC) combining low frequency fluctuations mainly due to respiration and sympathetic nervous system activity. In this report, we investigate the AC pulsatile waveform of the PPG pulse for ultimate use in extracting information regarding the biomechanical properties of tissue and vasculature. By analyzing the rise time of the pulse in the diastole period, we show that PPG is capable of measuring changes in the Young s Modulus of tissue mimicking phantoms with a resolution of 4 KPa in the range of 12 to 61 KPa. In addition, the shape of the pulse can potentially be used to diagnose vascular complications by differentiating upstream from downstream complications. A Windkessel model was used to model changes in the biomechanical properties of the circulation and to test the proposed concept. The modeling data confirmed the response seen in vitro and showed the same trends in the PPG rise and fall times with changes in compliance and vascular resistance.

  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. 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

  4. Tribomaterial factors in space mechanism brake performance

    NASA Technical Reports Server (NTRS)

    Hawthorne, H. M.

    1990-01-01

    The asbestos/phenolic pads of Shuttle Remote Manipulator System (SRMS) brakes are unsuitable for use in long life space mechanisms because their friction decreases on extended sliding in high vacuum. Dehydration of the material and accumulation of wear debris in the conforming interface of this tribosystem induces the permanent friction changes. Other polymer and some ceramic based materials exhibit similar frictional torque behavior due to the development of minimal contact patches by the interfacial debris. In contrast, high friction occurs when other ceramics form many small contacts throughout fine debris beds. Generating this latter interfacial structure during run-in ensures that the in-vacuo friction remains stable thereafter. Such materials with low wear rates are potential candidates for friction elements in SSRMS and similar mechanisms.

  5. Acousto-mechanical and thermal properties of clotted blood

    NASA Astrophysics Data System (ADS)

    Nahirnyak, Volodymyr M.; Yoon, S. Wang; Holland, Christy K.

    2005-04-01

    The efficacy of ultrasound-assisted thrombolysis as an adjunct treatment of ischemic stroke is being widely investigated. In order to determine the role of ultrasound hyperthermia in the process of blood clot disruption, the thermal and acousto-mechanical properties of clotted blood were measured in vitro. Whole blood clots were prepared from either fresh porcine or human blood by aliquoting 1.5 or 2.0 ml into 10 ml glass tubes (BD VacutainerTM, Franklin Lakes, NJ), immersing the tubes in a 37°C water bath for three hours and storing the clots at 5°C for at least three days prior to assessment of the properties, which ensured complete clot retraction. Direct calorimetric measurements using calibrated E-type thermocouples (Omega Engineering, Inc., Stanford, CT) were performed to determine the heat capacity and thermal conductivity of the human and porcine thrombi against a standard fluid, saline [0.9%]. The amplitude coefficient of attenuation of the clots was determined from 120 kHz to 3.5 MHz with a calibrated hydrophone (TC4038, RESON, Inc., Goleta, CA) in a 20+/-2°C water bath using the substitution method. The experimentally measured values of heat capacity, density, and thermal conductivity of porcine clotted blood are 3.23+/-0.46 J/g.K, 1.058+/-0.014 g/cm3, and 0.52+/-0.14 W/m.K. The attenuation coefficient ranged from 0.10 to 0.30 Nepers/cm over 120 kHz to 3.5 MHz. Measurements of the acousto-mechanical and thermal properties of clotted blood can be helpful in theoretical modeling of ultrasound hyperthermia in ultrasound-assisted thrombolysis.

  6. 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.

  7. Mechanical properties of lipid bilayers and regulation of mechanosensitive function

    PubMed Central

    Balleza, Daniel

    2012-01-01

    Material properties of lipid bilayers, including thickness, intrinsic curvature and compressibility regulate the function of mechanosensitive (MS) channels. This regulation is dependent on phospholipid composition, lateral packing and organization within the membrane. Therefore, a more complete framework to understand the functioning of MS channels requires insights into bilayer structure, thermodynamics and phospholipid structure, as well as lipid-protein interactions. Phospholipids and MS channels interact with each other mainly through electrostatic forces and hydrophobic matching, which are also crucial for antimicrobial peptides. They are excellent models for studying the formation and stabilization of membrane pores. Importantly, they perform equivalent responses as MS channels: (1) tilting in response to tension and (2) dissipation of osmotic gradients. Lessons learned from pore forming peptides could enrich our knowledge of mechanisms of action and evolution of these channels. Here, the current state of the art is presented and general principles of membrane regulation of mechanosensitive function are discussed. PMID:22790280

  8. Mechanical Properties of Particulate Reinforced Aluminium Alloy Matrix Composite

    SciTech Connect

    Sayuti, M.; Sulaiman, S.; Baharudin, B. T. H. T.; Arifin, M. K. A.; Suraya, S.; Vijayaram, T. R.

    2011-01-17

    This paper discusses the mechanical properties of Titanium Carbide (TiC) particulate reinforced aluminium-silicon alloy matrix composite. TiC particulate reinforced LM6 alloy matrix composites were fabricated by carbon dioxide sand molding process with different particulate weight fraction. Tensile strength, hardness and microstructure studies were conducted to determine the maximum load, tensile strength, modulus of elasticity and fracture surface analysis have been performed to characterize the morphological aspects of the test samples after tensile testing. Hardness values are measured for the TiC reinforced LM6 alloy composites and it has been found that it gradually increases with increased addition of the reinforcement phase. The tensile strength of the composites increased with the increase percentage of TiC particulate.

  9. Selected mechanical properties of fluoride-releasing restorative materials.

    PubMed

    Iazzetti, G; Burgess, J O; Gardiner, D

    2001-01-01

    Mechanical properties, diametral tensile strength (DTS) and flexural strength (FS) of six fluoride releasing materials were measured and compared. The samples were prepared and tested according to ISO specifications. The materials included a glass ionomer (Fuji IX), a resin-modified glass ionomer (Photac-Fil), two compomers (F 2000; Dyract AP) and two composites (Solitaire; Tetric Ceram). The tests were performed after the materials were stored in distilled water (DTS) and phosphate buffered saline solution (FS) at 37 degrees C for 24 hours and one week. Fluoride-releasing composite resin had the highest flexural and diametral tensile strengths and were statistically stronger than compomers, followed by resin-modified glass ionomer and conventional glass ionomer. However, a notable exception to this general trend was Solitaire, a fluoride-releasing composite resin.

  10. Effect of microstructure on mechanical properties in tungsten-titanium

    SciTech Connect

    Lo, C.F.

    1996-06-01

    A study was performed on the influence of the formation and distribution of W-rich ({beta}-Ti, W) phase on fracture resistance and hardness of powder-consolidated tungsten-10 wt.% titanium. The effect of density on the mechanical properties was also measured. The flexural stress and strain and hardness linearly increased with increasing density in the density range of 86% to 97% of theoretical density, 14.53 g/cc. In this range the generation of the W-rich ({beta}-Ti, W) was negligible. As the amount of W-rich ({beta}-Ti, W) increased for nearly, fully densified materials, a pronounced drop was found both in the flexural stress and strain. However, the hardness showed no correlation to the amount of W-rich ({beta}-Ti, W) phase present.

  11. Mechanical property measurements on ion-irradiated metals

    SciTech Connect

    Zinkle, S.J.; Oliver, W.C.

    1986-08-01

    A recently developed mechanical properties microprobe (MPM) has been used to investigate strength and elastic modulus changes in ion-irradiated metals. The indenter load and its displacement are simultaneously monitored while the indentation is being made and also during unloading. Microindentation hardness measurements have been performed on ion-irradiated copper and Cu-0.15% Zr (AMZIRC). The depth dependence of the ion damage has been investigated in selected specimens which were prepared using a cross-section technique. This procedure allows a direct comparison to be made of hardness data from different irradiation depths while the indent size is held constant. The displacement damage associated with ion irradiation caused either hardening or softening, depending on the irradiation conditions and the material.

  12. Mechanical Properties of Particulate Reinforced Aluminium Alloy Matrix Composite

    NASA Astrophysics Data System (ADS)

    Sayuti, M.; Sulaiman, S.; Baharudin, B. T. H. T.; Arifin, M. K. A.; Suraya, S.; Vijayaram, T. R.

    2011-01-01

    This paper discusses the mechanical properties of Titanium Carbide (TiC) particulate reinforced aluminium-silicon alloy matrix composite. TiC particulate reinforced LM6 alloy matrix composites were fabricated by carbon dioxide sand molding process with different particulate weight fraction. Tensile strength, hardness and microstructure studies were conducted to determine the maximum load, tensile strength, modulus of elasticity and fracture surface analysis have been performed to characterize the morphological aspects of the test samples after tensile testing. Hardness values are measured for the TiC reinforced LM6 alloy composites and it has been found that it gradually increases with increased addition of the reinforcement phase. The tensile strength of the composites increased with the increase percentage of TiC particulate.

  13. Effect of radiation on topopah spring tuff mechanical properties

    SciTech Connect

    Berge, P.A.; Blair, S.C.

    1996-11-01

    The effect of radiation on the mechanical properties of Topopah Spring tuff was investigated by performing uniaxial compressive tests on irradiated and control samples of the tuff from the potential repository horizon at Yucca Mountain. Test results are presented, including stress-strain curves and peak strength and Young`s modulus values. These results show that for homogeneous uncracked samples of Topopah Spring tuff, exposure to gamma radiation had no discernible effect on the unconfined partially healed subvertical caracks indicate that exposure may reduce the strength and Young`s modulus significantly. This is attributed to weakening of the cementing materials in the cracks and fractures of the samples that were irradiated. These results are preliminary, and additional studies are warranted to evaluate whether radiation weakens cementing materials in welded tuff.

  14. Loops Determine the Mechanical Properties of Mitotic Chromosomes

    PubMed Central

    Zhang, Yang; Heermann, Dieter W.

    2011-01-01

    We introduce a new polymer model for mitotic chromosomes. The key assumption of the model is the ability of the chromatin fibre to cross-link to itself due to binding proteins. These protein-chromatin interactions are included by a probabilistic and dynamic mechanism. The hypothesis is motivated by the observation of high repulsive forces between ring polymers. We performed computer simulations to validate our model. Our results show that the presence of loops leads to a tight compaction and contributes significantly to the bending rigidity of chromosomes. Moreover, our qualitative prediction of the force elongation behaviour is close to experimental findings. The Dynamic Loop Model presented here indicates that the internal structure of mitotic chromosomes is based on self-organization of the chromatin fibre rather than attachment of chromatin to a protein scaffold. It also shows that the number and size of loops have a strong influence on the mechanical properties. We suggest that changes in the mechanical characteristics of chromosomes in different stages of the cell cycle, for example, can be explained by an altered internal loop structure. PMID:22216220

  15. Mechanical properties of ISABELLE superconducting coils

    SciTech Connect

    Thompson, P.; Bertsche, A.; Fuhrmann, J.; Greene, A.; Grove, E.; Repeta, L.; Short, F.; Tannenbaum, M.; Wanderer, P.

    1981-01-01

    As a part of the manufacturing processes, several mechanical measurements are made on ISABELLE dipoles. These are done both to control the process and to provide information for the evaluation of the behavior of the completed magnets. This paper discusses the Young's Modulus (E = 1-3 x 10/sup 6/ psi), the thermal contraction of the coil assembly (..delta..L/L = 290 +- 17 x 10/sup -5/ at 77/sup 0/K), and the loss of applied prestress with time (approx. 20% for times 20 days).

  16. Porosity and mechanical properties of zirconium ceramics

    SciTech Connect

    Kalatur, Ekaterina Narikovich, Anton; Buyakova, Svetlana E-mail: kulkov@ispms.tsc.ru; Kulkov, Sergey E-mail: kulkov@ispms.tsc.ru

    2014-11-14

    The article studies the porous ceramics consisting of ultra-fine ZrO{sub 2} powders. The porosity of ceramic samples varied from 15% to 80%. The structure of the ceramic materials had a cellular configuration. The distinctive feature of all experimentally obtained strain diagrams is their nonlinearity at low deformations characterized by the parabolic law. It was shown that the observed nonlinear elasticity for low deformations shown in strain diagrams is due to the mechanical instability of cellular elements of the ceramic framework.

  17. Annealing and Mechanical Properties of ECAP Tantalum

    DTIC Science & Technology

    2011-03-01

    deformation. 9.0 References 1 J. M. O’Brien and W. F. Hosford . “Grain Refinement of Tantalum, Copper and Zirconium by Equal Channal Angular...pp. 205-217. 10 S. Nemat-Nasser and J.B. Isaacs, Acta Materialia 45 (3) (1997) pp.907-919. 11 W. F. Hosford , The Mechanics of Crystals and...O’Brien and W. F. Hosford , AFRL-MN-EG-TR-2007-7000, Technical Report, Eglin AFB, FL, November 2006, Contract No. F08651-02-C-0023. 17 P. S

  18. Mechanical properties of plastics predetermined by empirical method

    NASA Technical Reports Server (NTRS)

    Lohr, J. J.; Parker, J. A.

    1964-01-01

    To predetermine the mechanical properties of rigid plastics as a function of plasticizer content and composition, a set of equations has been empirically derived. These relate strain rate, yield stress, temperature, and weight fraction of the plasticizer.

  19. Influence of initial flaws on the mechanical properties of nacre.

    PubMed

    Anup, S

    2015-06-01

    Nacre is a bio-composite made up of hard mineral and soft protein, and has excellent mechanical properties. This paper examines the effect of naturally occurring defects (initial flaws) in nacre on its mechanical properties such as toughness and strength. A random fuse model is developed incorporating initial flaws. Numerical simulations show that initial flaws affect different mechanical properties at different rates. The variation in the experimentally obtained mechanical properties of nacre reported in the literature is shown to be due to initial flaws. The stress in the mineral and protein increases due to initial flaws, but by different amounts. The results obtained in this study are useful for gaining insight into the failure of nacre and development of nacre-inspired composites.

  20. 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)

  1. Modified Polypropylene with Improved Physical-Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Chervakov, D. O.; Bashtanyk, P. I.; Burmistr, M. V.

    2015-03-01

    The use of mixtures of benzoyl peroxide and polysiloxane polyol compounds as polypropylene modifiers is suggested. It is established that, in such a way, its physical-mechanical properties can be changed purposefully.

  2. Marine Engine Mechanics. Performance Objectives. Intermediate Course.

    ERIC Educational Resources Information Center

    Jones, Marion

    Several intermediate performance objectives and corresponding criterion measures are presented for each of ten terminal objectives for a two-semester course (3 hours daily). This 540-hour intermediate course includes advanced troubleshooting techniques on outboard marine engines, inboard-outboard marine engines, inboard marine engines, boat…

  3. Marine Engine Mechanics. Performance Objectives. Basic Course.

    ERIC Educational Resources Information Center

    Jones, Marion

    Several intermediate performance objectives and corresponding criterion measures are presented for each of six terminal objectives for a two-semester course (2 hours daily) which provides training in the terminology, construction, and function of both two- and four-cycle fuel-air mixture internal combustion engines with emphasis on outboard marine…

  4. Applying Mechanics to Swimming Performance Analysis.

    ERIC Educational Resources Information Center

    Barthels, Katharine

    1989-01-01

    Swimming teachers and coaches can improve their feedback to swimmers, when correcting or refining swim movements, by applying some basic biomechanical concepts relevant to swimming. This article focuses on the biomechanical considerations used in analyzing swimming performance. Techniques for spotting and correcting problems that impede…

  5. Mechanical Properties of Four Human Longbones.

    DTIC Science & Technology

    1981-11-30

    torsion. RT3793 had compressive strains parallel to the torsional axis and, since the gages were in the medio - anterior surface, these strains...bending toward the latero-posterior side while LT3782 was twisted eversively and tended to bend medio -anteriorly. This is opposite to the indications of the... ambient conditions of the laboratory for periods of time in excess of that allowed for 390 smAll scale tests of bone tissue, the performance of the four

  6. Microstructure and mechanical properties of neoprene montmorillonite nanocomposites

    NASA Astrophysics Data System (ADS)

    Yeh, Meng-Heng; Hwang, Weng-Sing; Cheng, Lin-Ri

    2007-03-01

    To investigate the microstructure and mechanical properties of neoprene-montmorillonite nanocomposite, three modified montmorillonite are used. An X-ray diffractometer is used to measure the corresponding change in d-spacing. Scanning electron microscopy is employed to investigate the morphology of the various composites. Transmission electron microscopy is employed to investigate the composite of montmorillonite and neoprene. The results indicate that the addition of montmorillonite enhances the mechanical properties of neoprene significantly.

  7. Processing effects on the mechanical properties of tungsten heavy alloys

    NASA Technical Reports Server (NTRS)

    Kishi, Toshihito; German, R. M.

    1990-01-01

    Tungsten heavy alloys exhibit significant mechanical property sensitivities to the fabrication variables. These sensitivities are illustrated in this examination of vacuum sintering and the effects of composition, sintering temperature, and sintering time on the mechanical properties of tungsten heavy alloys. Measurements were conducted to assess the density, strength, hardness, and elongation dependencies. A detrimental aspect of vacuum sintering is matrix phase evaporation, although vacuum sintering does eliminate the need for postsintering heat treatments.

  8. Primate dietary ecology in the context of food mechanical properties.

    PubMed

    Coiner-Collier, Susan; Scott, Robert S; Chalk-Wilayto, Janine; Cheyne, Susan M; Constantino, Paul; Dominy, Nathaniel J; Elgart, Alison A; Glowacka, Halszka; Loyola, Laura C; Ossi-Lupo, Kerry; Raguet-Schofield, Melissa; Talebi, Mauricio G; Sala, Enrico A; Sieradzy, Pawel; Taylor, Andrea B; Vinyard, Christopher J; Wright, Barth W; Yamashita, Nayuta; Lucas, Peter W; Vogel, Erin R

    2016-09-01

    Substantial variation exists in the mechanical properties of foods consumed by primate species. This variation is known to influence food selection and ingestion among non-human primates, yet no large-scale comparative study has examined the relationships between food mechanical properties and feeding strategies. Here, we present comparative data on the Young's modulus and fracture toughness of natural foods in the diets of 31 primate species. We use these data to examine the relationships between food mechanical properties and dietary quality, body mass, and feeding time. We also examine the relationship between food mechanical properties and categorical concepts of diet that are often used to infer food mechanical properties. We found that traditional dietary categories, such as folivory and frugivory, did not faithfully track food mechanical properties. Additionally, our estimate of dietary quality was not significantly correlated with either toughness or Young's modulus. We found a complex relationship among food mechanical properties, body mass, and feeding time, with a potential interaction between median toughness and body mass. The relationship between mean toughness and feeding time is straightforward: feeding time increases as toughness increases. However, when considering median toughness, the relationship with feeding time may depend upon body mass, such that smaller primates increase their feeding time in response to an increase in median dietary toughness, whereas larger primates may feed for shorter periods of time as toughness increases. Our results emphasize the need for additional studies quantifying the mechanical and chemical properties of primate diets so that they may be meaningfully compared to research on feeding behavior and jaw morphology. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Mechanical properties of henequen fibre/epoxy resin composites

    NASA Astrophysics Data System (ADS)

    Gonzalez-Murillo, C.; Ansell, M. P.

    2009-07-01

    By using surface-treated and untreated henequen fibres and an epoxy resin, composites were made by compression moulding, and their mechanical properties and failure modes were determined experimentally in tension, bending, and impact loading. The results obtained show that the treatment of fibre surface does not improve the bond between the fibres and the resin matrix, and the general mechanical properties of the composites are similar.

  10. Effects of high energy radiation on the mechanical properties of epoxy graphite fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Gilbert, R. D.; Fornes, R. E.; Memory, J. D.

    1983-01-01

    The effects of high energy radiation on mechanical properties and on the molecular and structural properties of graphite fiber reinforced composites are assessed so that durability in space applications can be predicted. A listing of composite systems irradiated along with the maximum radiation dose applied and type of mechanical tests performed is shown. These samples were exposed to 1/2 MeV electrons.

  11. Microscopic Electronic and Mechanical Properties of Ultra-Thin Layered Materials

    DTIC Science & Technology

    2016-07-25

    AFRL-AFOSR-VA-TR-2016-0264 MICROSCOPIC ELECTRONIC AND MECHANICAL PROPERTIES OF ULTRA-THIN LAYERED MATERIALS Abhay Pasupathy THE TRUSTEES OF COLUMBIA...MECHANICAL PROPERTIES OF ULTRA-THIN LAYERED MATERIALS 5b. GRANT NUMBER FA9550-11-1-0010 5c. PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) Abhay...of ultra-thin (few layer) crystalline materials , commonly referred to as 2D materials . The technical approach used was to perform atomic-resolution

  12. Measuring the mechanical properties of molecular conformers

    NASA Astrophysics Data System (ADS)

    Jarvis, S. P.; Taylor, S.; Baran, J. D.; Champness, N. R.; Larsson, J. A.; Moriarty, P.

    2015-09-01

    Scanning probe-actuated single molecule manipulation has proven to be an exceptionally powerful tool for the systematic atomic-scale interrogation of molecular adsorbates. To date, however, the extent to which molecular conformation affects the force required to push or pull a single molecule has not been explored. Here we probe the mechanochemical response of two tetra(4-bromophenyl)porphyrin conformers using non-contact atomic force microscopy where we find a large difference between the lateral forces required for manipulation. Remarkably, despite sharing very similar adsorption characteristics, variations in the potential energy surface are capable of prohibiting probe-induced positioning of one conformer, while simultaneously permitting manipulation of the alternative conformational form. Our results are interpreted in the context of dispersion-corrected density functional theory calculations which reveal significant differences in the diffusion barriers for each conformer. These results demonstrate that conformational variation significantly modifies the mechanical response of even simple porpyhrins, potentially affecting many other flexible molecules.

  13. Mechanical properties of rare earth stannate pyrochlores

    NASA Astrophysics Data System (ADS)

    Feng, J.; Xiao, B.; Qu, Z. X.; Zhou, R.; Pan, W.

    2011-11-01

    The RE2Sn2O7 series compounds (RE = La, Nb, Sm, Gd, Er, Yb) with a pyrochlore structure are prepared by co-precipitation method. The bulk, shear, Young's moduli, B/G, and Poisson's ratios are calculated using density functional theory and also measured by ultrasonic resonance method. The theoretical values of lattice constants and mechanical moduli are smaller than experimental results. The electronic structures of RE2Sn2O7 are analogous to RE2Zr2O7. La2Sn2O7 exhibits stronger ionic bonds than others. The covalent interactions are slightly enhanced in the heavy rare earth stannate pyrochlores. The Vickers harnesses of RE2Sn2O7 are measured experimentally, which are smaller than theoretical predictions.

  14. Measuring the mechanical properties of molecular conformers.

    PubMed

    Jarvis, S P; Taylor, S; Baran, J D; Champness, N R; Larsson, J A; Moriarty, P

    2015-09-21

    Scanning probe-actuated single molecule manipulation has proven to be an exceptionally powerful tool for the systematic atomic-scale interrogation of molecular adsorbates. To date, however, the extent to which molecular conformation affects the force required to push or pull a single molecule has not been explored. Here we probe the mechanochemical response of two tetra(4-bromophenyl)porphyrin conformers using non-contact atomic force microscopy where we find a large difference between the lateral forces required for manipulation. Remarkably, despite sharing very similar adsorption characteristics, variations in the potential energy surface are capable of prohibiting probe-induced positioning of one conformer, while simultaneously permitting manipulation of the alternative conformational form. Our results are interpreted in the context of dispersion-corrected density functional theory calculations which reveal significant differences in the diffusion barriers for each conformer. These results demonstrate that conformational variation significantly modifies the mechanical response of even simple porpyhrins, potentially affecting many other flexible molecules.

  15. Mechanical properties of hydroxyapatite/mica composite.

    PubMed

    Nordström, E G; Herø, H; Jørgensen, R B

    1994-01-01

    Bend specimens of the inorganic synthetic materials hydroxyapatite (HA) and a composite of hydroxyapatite/muscovite mica have been prepared and tested mechanically. Sintering followed by hot isostatic pressing (HIP) without encapsulation gave an increased strength for HA alone, but no significant increase in strength compared with sintering alone for HA/mica composites. The bend strength of the HA/mica composite was inferior to that of HA alone, the reason being inadequate bonding between HA and mica. HIP in glass capsules and an increased cold compaction pressure tended to improve the bend strength of the composite. Corrosion in tris for 7 d did not affect the bend strength of the investigated materials significantly.

  16. Effective elastic mechanical properties of single layer graphene sheets.

    PubMed

    Scarpa, F; Adhikari, S; Srikantha Phani, A

    2009-02-11

    The elastic moduli of single layer graphene sheet (SLGS) have been a subject of intensive research in recent years. Calculations of these effective properties range from molecular dynamic simulations to use of structural mechanical models. On the basis of mathematical models and calculation methods, several different results have been obtained and these are available in the literature. Existing mechanical models employ Euler-Bernoulli beams rigidly jointed to the lattice atoms. In this paper we propose truss-type analytical models and an approach based on cellular material mechanics theory to describe the in-plane linear elastic properties of the single layer graphene sheets. In the cellular material model, the C-C bonds are represented by equivalent mechanical beams having full stretching, hinging, bending and deep shear beam deformation mechanisms. Closed form expressions for Young's modulus, the shear modulus and Poisson's ratio for the graphene sheets are derived in terms of the equivalent mechanical C-C bond properties. The models presented provide not only quantitative information about the mechanical properties of SLGS, but also insight into the equivalent mechanical deformation mechanisms when the SLGS undergoes small strain uniaxial and pure shear loading. The analytical and numerical results from finite element simulations show good agreement with existing numerical values in the open literature. A peculiar marked auxetic behaviour for the C-C bonds is identified for single graphene sheets under pure shear loading.

  17. Mechanical properties of a porous mullite material

    NASA Technical Reports Server (NTRS)

    Viens, Michael J.

    1991-01-01

    Modulus of rupture specimens were used to determine crack growth parameters of a porous mullite material. Strength testing was performed in ambient and moist environments. The power law crack growth rate parameters n and 1n B in 50 percent relative humidity were found to be 44.98 and 0.94, respectively. The inert strength, fracture toughness, and elastic modulus were also determined and found to be 19 MPa, 055 MPa(m) exp 1/2, and 11.6 GPa, respectively.

  18. Analgesic Drugs Alter Connective Tissue Remodeling and Mechanical Properties

    PubMed Central

    Carroll, Chad C.

    2015-01-01

    Exercising individuals commonly consume analgesics but these medications alter tendon and skeletal muscle connective tissue properties, possibly limiting a person from realizing the full benefits of exercise training. I detail the novel hypothesis that analgesic medications alter connective tissue structure and mechanical properties by modifying fibroblast production of growth factors and matrix enzymes, which are responsible for extracellular matrix remodeling. PMID:26509485

  19. Analgesic Drugs Alter Connective Tissue Remodeling and Mechanical Properties.

    PubMed

    Carroll, Chad C

    2016-01-01

    Exercising individuals commonly consume analgesics, but these medications alter tendon and skeletal muscle connective tissue properties, possibly limiting a person from realizing the full benefits of exercise training. I detail the novel hypothesis that analgesic medications alter connective tissue structure and mechanical properties by modifying fibroblast production of growth factors and matrix enzymes, which are responsible for extracellular matrix remodeling.

  20. 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...

  1. 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...

  2. Effects of Composition and Crystallinity on the Mechanical Properties of Reactive Ternary Blends

    NASA Astrophysics Data System (ADS)

    Zeng, Xiguo; Krishnamoorthy, Jayaraman; Hsu, Shaw L.; Paul, Charles W.; Wang, Brigitte

    2007-03-01

    Studies were conducted to elucidate the effects of composition, morphology and crystallinity on the mechanical properties of reactive ternary blends. The blends, used as the model system of high performance hot-melt adhesives, contain functionalized crystallizable polyester, functionalized noncrystallizable polyether and an acrylic random copolymer. When mixed, the prepolymers offer a wide range of physical properties. Results indicate the mechanical properties, discussed in terms of tensile strength and modulus, are strongly dependent on morphological features such as degree of crystallinity, crystal size and blend composition. Apart from the bulk mechanical properties, adhesive strength of the blends were also studied on different substrates having different surface energies. From the failure mechanisms and surface analyses of the newly-created surfaces, a correlation was drawn between migration of polymers, surface energy of the substrate and deformation mechanism of the polymer components.

  3. 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.

  4. 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.

  5. 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.

  6. Mechanical performance of hemp fiber polypropylene composites at different operating temperatures

    Treesearch

    Mehdi Tajvidi; Nazanin Motie; Ghonche Rassam; Robert H. Falk; Colin Felton

    2010-01-01

    In order to quantify the effect of temperature on the mechanical properties of hemp fiber polypropylene composites, formulations containing 25% and 40% (by weight) hemp fiber were produced and tested at three representative temperatures of 256, 296, and 336 K. Flexural, tensile, and impact tests, as well as dynamic mechanical analysis, were performed and the reduction...

  7. Mechanical Properties of Gels; Stress from Confined Fluids

    SciTech Connect

    George W. Scherer

    2009-12-01

    Abstract for Grant DE-FG02-97ER45642 Period: 1997-2002 Mechanical Properties of Gels 2002-2008 Stress from Confined Fluids Principal investigator: Prof. George W. Scherer Dept. Civil & Env. Eng./PRISM Eng. Quad. E-319 Princeton, NJ 08544 USA Recipient organization: Trustees of Princeton University 4 New South Princeton, NJ 08544 USA Abstract: The initial stage of this project, entitled Mechanical Properties of Gels, was dedicated to characterizing and explaining the properties of inorganic gels. Such materials, made by sol-gel processing, are of interest for fabrication of films, fibers, optical devices, advanced insulation and other uses. However, their poor mechanical properties are an impediment in some applications, so understanding the origin of these properties could lead to enhanced performance. Novel experimental methods were developed and applied to measure the stiffness and permeability of gels and aerogels. Numerical simulations were developed to reproduce the growth process of the gels, resulting in structures whose mechanical properties matched the measurements. The models showed that the gels are formed by the growth of relatively robust clusters of molecules that are joined by tenuous links whose compliance compromises the stiffness of the structure. Therefore, synthetic methods that enhance the links could significantly increase the rigidity of such gels. The next stage of the project focused on Stress from Confined Fluids. The first problem of interest was the enhanced thermal expansion coefficient of water that we measured in the nanometric pores of cement paste. This could have a deleterious effect on the resistance of concrete to rapid heating in fires, because the excessive thermal expansion of water in the pores of the concrete could lead to spalling and collapse. A series of experiments demonstrated that the expansion of water increases as the pore size decreases. To explain this behavior, we undertook a collaboration with Prof. Stephen

  8. Mechanical properties of human trabecular bone lamellae quantified by nanoindentation.

    PubMed

    Zysset, P K; Guo, X E; Hoffler, C E; Moore, K E; Goldstein, S A

    1998-12-01

    Improved preventive and therapeutic strategies for skeletal diseases such as osteoporosis rely on a better understanding of the mechanical properties of trabecular bone and their influence on cell mediated adaptation processes. The mechanical properties of trabecular bone are determined by composition as well as structural (trabecular architecture), microstructural (trabecular packets) and nanostructural (lamellae) organization. Density is the major predictor of the mechanical properties of trabecular structures and has been extended to the concept of fabric to include architectural anisotropy and improve even further the power of prediction. Recent advances in QCT and MRI technologies allow for precise assessment of 3D trabecular architecture and the mechanical consequences of structural changes can be increasingly well quantified by the means of computational methods. While single trabeculae have been tested using various techniques with contrasting results, little is known about the intrinsic mechanical properties of trabecular bone lamellae on which these computational methods rely. For instance, water and mineral content have a significant effect on the elastic, viscous, yield and postyield properties of bone tissue. In addition, collagen fiber orientation affects the mechanics of single remodeling units. Variations in composition and organization determined by age, accumulated damage or disease may therefore reduce the mechanical integrity of trabecular bone and deserve more attention. The aim of this work was to utilize a nanoindentation technique to quantify elastic modulus and hardness of human trabecular bone lamellae.

  9. Mechanical properties of dental investment materials.

    PubMed

    Low, D; Swain, M V

    2000-07-01

    Measurement of the elastic modulus (E) of investment materials has been difficult because of their low strength. However, these values are essential for engineering simulation and there are many methods available to assess the elasticity of materials. The present study compared two different methods with one of the methods being non-destructive in nature and can be used for specimens prepared for other tests. Two different types of investment materials were selected, gypsum-and phosphate-bonded. Method 1 is a traditional three-point bending test. Twelve rectangular bars with dimension of (70 x 9 x 3 mm) were prepared and placed on supports 56.8 mm apart. The test was conducted at a cross-head speed of 1 mm/min by use of a universal testing machine. The load applied to the test specimen and the corresponding deflection were measured until the specimen fractured. The E value was calculated from a linear part of the stress-strain plot. Method 2 is an ultra micro-indentation system to determine near surface properties of materials with nanometer resolution. The measurement procedure was programmed such that the specimens were indented with an initial contact force of 5 mN then followed by a maximum force of 500 mN. Measurement consisted of 10 indentations conducted with a spherical stainless steel indenter (R = 250 microm) that were equally spaced (500 microm). The E value rose asymptotically with depth of penetration and would approach the three-point bending test value at approximately four time's maximum contact depth for both materials. Both methods are practical ways of measuring the E of investment materials.

  10. Fluid mechanical properties of flames in enclosures

    SciTech Connect

    Rotman, D.A.; Pindera, M.Z.; Oppenheim, A.K.

    1988-07-01

    In an enclosure where the reacting medium is initially at rest, the flame first generates a flowfield that then gets stretched, i.e., its front is pulled along the surface by the flowfield in which it then finds itself residing. A methodology developed for numerical modeling of such fields is described. Of key significance in this respect is the zero Mach number model/endash/a reasonable idealization in view of the relatively high temperature, and hence sound speed, that exists, concomitantly with a comparatively low particle velocity, in the confinement of a combustion chamber. According to this model, the density gradient in the field is nullified, while across the flame front it approaches infinity. One has thus two regimes: one of the unburned medium and the other of the burned gas, each of spatially uniform density, separated by a flame front interface. The latter is endowed with four properties, of which the first two are purely kinematic and the others dynamic in nature, namely: 1) it is advected at the local velocity of flow; 2) it self-advances at the normal burning speed, the eigenvalue of the system; 3) it acts as the velocity source due to the exothermicity of the combustion process; and 4) it acts as the vorticity source due to the baroclinic effect generated by the pressure gradient along its surface and the density gradient across it. A solution obtained for a flame propagating in an oblong rectangular enclosure demonstrates that the latter has a significant influence upon the formation of the well known tulip shape. 12 refs., 4 figs.

  11. Mechanical properties of lanthanum and yttrium chromites

    SciTech Connect

    Paulik, S.W.; Armstrong, T.R.

    1996-12-31

    In an operating high-temperature (1000{degrees}C) solid oxide fuel cell (SOFC), the interconnect separates the fuel (P(O{sub 2}){approx}10{sup -16} atm) and the oxidant (P(O2){approx}10{sup 0.2} atm), while being electrically conductive and connecting the cells in series. Such severe atmospheric and thermal demands greatly reduce the number of viable candidate materials. Only two materials, acceptor substituted lanthanum chromite and yttrium chromite, meet these severe requirements. In acceptor substituted chromites (Sr{sup 2+} or Ca{sup 2+} for La{sup 3+}), charge compensation is primarily electronic in oxidizing conditions (through the formation of Cr{sup 4+}). Under reducing conditions, ionic charge compensation becomes significant as the lattice becomes oxygen deficient. The formation of oxygen vacancies is accompanied by the reduction of Cr{sup 4+} ions to Cr{sup 3+} and a resultant lattice expansion. The lattice expansion observed in large chemical potential gradients is not desirable and has been found to result in greatly reduced mechanical strength.

  12. Measuring the mechanical properties of molecular conformers

    PubMed Central

    Jarvis, S. P.; Taylor, S.; Baran, J. D.; Champness, N. R.; Larsson, J. A.; Moriarty, P.

    2015-01-01

    Scanning probe-actuated single molecule manipulation has proven to be an exceptionally powerful tool for the systematic atomic-scale interrogation of molecular adsorbates. To date, however, the extent to which molecular conformation affects the force required to push or pull a single molecule has not been explored. Here we probe the mechanochemical response of two tetra(4-bromophenyl)porphyrin conformers using non-contact atomic force microscopy where we find a large difference between the lateral forces required for manipulation. Remarkably, despite sharing very similar adsorption characteristics, variations in the potential energy surface are capable of prohibiting probe-induced positioning of one conformer, while simultaneously permitting manipulation of the alternative conformational form. Our results are interpreted in the context of dispersion-corrected density functional theory calculations which reveal significant differences in the diffusion barriers for each conformer. These results demonstrate that conformational variation significantly modifies the mechanical response of even simple porpyhrins, potentially affecting many other flexible molecules. PMID:26388232

  13. Porosity and mechanical properties of zirconium ceramics

    SciTech Connect

    Buyakova, S. Kulkov, S.; Sablina, T.

    2015-11-17

    Has been studied a porous ceramics obtained from ultra-fine powders. Porous ceramic ZrO{sub 2}(MgO), ZrO{sub 2}(Y{sub 2}O{sub 3}) powder was prepared by pressing and subsequent sintering of compacts homologous temperatures ranging from 0.63 to 0.56 during the isothermal holding duration of 1 to 5 hours. The porosity of ceramic samples was from 15 to 80%. The structure of the ceramic materials produced from plasma-sprayed ZrO{sub 2} powder was represented as a system of cell and rod structure elements. Cellular structure formed by stacking hollow powder particles can be easily seen at the images of fracture surfaces of obtained ceramics. There were three types of pores in ceramics: large cellular hollow spaces, small interparticle pores which are not filled with powder particles and the smallest pores in the shells of cells. The cells generally did not have regular shapes. The size of the interior of the cells many times exceeded the thickness of the walls which was a single-layer packing of ZrO{sub 2} grains. A distinctive feature of all deformation diagrams obtained in the experiment was their nonlinearity at low deformations which was described by the parabolic law. It was shown that the observed nonlinear elasticity for low deformation on deformation diagrams is due to mechanical instability of the cellular elements in the ceramic carcass.

  14. Porosity and mechanical properties of zirconium ceramics

    NASA Astrophysics Data System (ADS)

    Buyakova, S.; Sablina, T.; Kulkov, S.

    2015-11-01

    Has been studied a porous ceramics obtained from ultra-fine powders. Porous ceramic ZrO2(MgO), ZrO2(Y2O3) powder was prepared by pressing and subsequent sintering of compacts homologous temperatures ranging from 0.63 to 0.56 during the isothermal holding duration of 1 to 5 hours. The porosity of ceramic samples was from 15 to 80%. The structure of the ceramic materials produced from plasma-sprayed ZrO2 powder was represented as a system of cell and rod structure elements. Cellular structure formed by stacking hollow powder particles can be easily seen at the images of fracture surfaces of obtained ceramics. There were three types of pores in ceramics: large cellular hollow spaces, small interparticle pores which are not filled with powder particles and the smallest pores in the shells of cells. The cells generally did not have regular shapes. The size of the interior of the cells many times exceeded the thickness of the walls which was a single-layer packing of ZrO2 grains. A distinctive feature of all deformation diagrams obtained in the experiment was their nonlinearity at low deformations which was described by the parabolic law. It was shown that the observed nonlinear elasticity for low deformation on deformation diagrams is due to mechanical instability of the cellular elements in the ceramic carcass.

  15. Mechanical Properties of Nanoscopic Lipid Domains

    SciTech Connect

    Nickels, Jonathan D.; Cheng, Xiaolin; Mostofian, Barmak; Stanley, Christopher; Lindner, Benjamin; Heberle, Frederick A.; Perticaroli, Stefania; Feygenson, Mikhail; Egami, Takeshi; Standaert, Robert F.; Smith, Jeremy C.; Myles, Dean A. A.; Ohl, Michael; Katsaras, John

    2015-09-28

    We found that the lipid raft hypothesis presents insight into how the cell membrane organizes proteins and lipids to accomplish its many vital functions. Yet basic questions remain about the physical mechanisms that lead to the formation, stability, and size of lipid rafts. Thus, much interest has been generated in the study of systems that contain similar lateral heterogeneities, or domains. In the current work we present an experimental approach that is capable of isolating the bending moduli of lipid domains. This is accomplished using neutron scattering and its unique sensitivity to the isotopes of hydrogen. Combining contrast matching approaches with inelastic neutron scattering, we isolate the bending modulus of ~13 nm diameter domains residing in 60 nm unilamellar vesicles, whose lipid composition mimics the mammalian plasma membrane outer leaflet. Importantly, the bending modulus of the nanoscopic domains differs from the modulus of the continuous phase surrounding them. Moreover, from additional structural measurements and all-atom simulations, we also determine that nanoscopic domains are in-register across the bilayer leaflets. Taken together, these results inform a number of theoretical models of domain/raft formation and highlight the fact that mismatches in bending modulus must be accounted for when explaining the emergence of lateral heterogeneities in lipid systems and biological membranes.

  16. Mechanical Properties of Nanoscopic Lipid Domains

    DOE PAGES

    Nickels, Jonathan D.; Cheng, Xiaolin; Mostofian, Barmak; ...

    2015-09-28

    We found that the lipid raft hypothesis presents insight into how the cell membrane organizes proteins and lipids to accomplish its many vital functions. Yet basic questions remain about the physical mechanisms that lead to the formation, stability, and size of lipid rafts. Thus, much interest has been generated in the study of systems that contain similar lateral heterogeneities, or domains. In the current work we present an experimental approach that is capable of isolating the bending moduli of lipid domains. This is accomplished using neutron scattering and its unique sensitivity to the isotopes of hydrogen. Combining contrast matching approachesmore » with inelastic neutron scattering, we isolate the bending modulus of ~13 nm diameter domains residing in 60 nm unilamellar vesicles, whose lipid composition mimics the mammalian plasma membrane outer leaflet. Importantly, the bending modulus of the nanoscopic domains differs from the modulus of the continuous phase surrounding them. Moreover, from additional structural measurements and all-atom simulations, we also determine that nanoscopic domains are in-register across the bilayer leaflets. Taken together, these results inform a number of theoretical models of domain/raft formation and highlight the fact that mismatches in bending modulus must be accounted for when explaining the emergence of lateral heterogeneities in lipid systems and biological membranes.« less

  17. 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...

  18. 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.

  19. Mechanical and biological properties of keratose biomaterials.

    PubMed

    de Guzman, Roche C; Merrill, Michelle R; Richter, Jillian R; Hamzi, Rawad I; Greengauz-Roberts, Olga K; Van Dyke, Mark E

    2011-11-01

    The oxidized form of extractable human hair keratin proteins, commonly referred to as keratose, is gaining interest as a biomaterial for multiple tissue engineering studies including those directed toward peripheral nerve, spinal cord, skin, and bone regeneration. Unlike its disulfide cross-linked counterpart, kerateine, keratose does not possess a covalently cross-linked network structure and consequently displays substantially different characteristics. In order to understand its mode(s) of action and potential for clinical translatability, detailed characterization of the composition, physical properties, and biological responses of keratose biomaterials are needed. Keratose was obtained from end-cut human hair fibers by peracetic acid treatment, followed by base extraction, and subsequent dialysis. Analysis of lyophilized keratose powder determined that it contains 99% proteins by mass with amino acid content similar to human hair cortex. Metallic elements were also found in minute quantities. Protein oxidation led to disulfide bond cleavage and drastic reduction of free thiols due to conversion of sulfhydryl to sulfonic acid, chain fragmentation, and amino acid modifications. Mass spectrometry identified the major protein constituents as a heterogeneous mixture of 15 hair keratins (type I: K31-35 and K37-39, and type II: K81-86) with small amounts of epithelial keratins which exist in monomeric, dimeric, multimeric, and even degraded forms. Re-hydration with PBS enabled molecular assembly into an elastic solid-like hydrogel. Highly-porous scaffolds formed by lyophilization of the gel had the compression behavior of a cellular foam material and reverted back to gel upon wetting. Cytotoxicity assays showed that the EC50 for various cell lines were attained at 8-10 mg/mL keratose, indicating the non-toxic nature of the material. Implantation in mouse subcutaneous tissue pockets demonstrated that keratose resorption follows a rectangular hyperbolic regression

  20. Dynamic monitoring of cell mechanical properties using profile microindentation

    PubMed Central

    Guillou, L.; Babataheri, A.; Puech, P.-H.; Barakat, A. I.; Husson, J.

    2016-01-01

    We have developed a simple and relatively inexpensive system to visualize adherent cells in profile while measuring their mechanical properties using microindentation. The setup allows simultaneous control of cell microenvironment by introducing a micropipette for the delivery of soluble factors or other cell types. We validate this technique against atomic force microscopy measurements and, as a proof of concept, measure the viscoelastic properties of vascular endothelial cells in terms of an apparent stiffness and a dimensionless parameter that describes stress relaxation. Furthermore, we use this technique to monitor the time evolution of these mechanical properties as the cells’ actin is depolymerized using cytochalasin-D. PMID:26857265

  1. ACCESS: thermal mechanical design and performance

    NASA Astrophysics Data System (ADS)

    Kaiser, Mary E.; Morris, Matthew J.; Hansen, Jason; Jensen, Scott; McCandliss, Stephan R.; Rauscher, Bernard J.; Kimble, Randy A.; Kruk, Jeffrey W.; Pelton, Russell; Mott, D. Brent; Wen, Yiting; Gardner, Jonathan P.; Benford, Dominic J.; Woodgate, Bruce E.; Wright, Edward L.; Feldman, Paul D.; Moos, H. Warren; Riess, Adam G.; Bohlin, Ralph; Deustua, Susana E.; Dixon, W. V.; Sahnow, David J.; Kurucz, Robert; Lampton, Michael; Perlmutter, Saul

    2013-09-01

    Establishing improved spectrophotometric standards is important for a broad range of missions and is relevant to many astrophysical problems. ACCESS, "Absolute Color Calibration Experiment for Standard Stars", is a series of rocket-borne sub-orbital missions and ground-based experiments designed to enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35-1.7μm bandpass. Achieving a calibration accuracy of 1% not only requires an accurate calibration transfer from the detector standards to the instrument, but it also requires characterization and stability of the detector as well as a thermal background that contributes less than 1% to the flux per resolution element in the near-infrared (1.7μm) spectral region of the ACCESS bandpass. This paper describes the thermal mechanical design for achieving a low thermal background across the ACCESS spectral bandpass.

  2. Electronic, optical, mechanical and thermoelectric properties of graphene

    NASA Astrophysics Data System (ADS)

    Muley, Sarang Vilas

    Graphene, a two-dimensional allotrope of graphite with sp2 bonded carbon atoms, is arranged in honeycomb structure. Its quasi one-dimensional form is graphene nanoribbon (GNR). Graphene related materials have been found to display excellent electronic, chemical, mechanical properties along with uniquely high thermal conductivity, electrical conductivity and high optical transparency. With excellent electrical characteristics such as high carrier transport properties, quantum Hall effect at room temperature and unusual magnetic properties, graphene has applications in optoelectronic devices. Electronically, graphene is a zero bandgap semiconductor making it essential to tailor its structure for obtaining specific band structure. Narrow GNRs are known to open up bandgap and found to exhibit variations for different chiralities i.e., armchair and zigzag. Doping graphene, with p- or n- type elements, is shown to exhibit bandgap in contrast to pristine graphene. In this study, optical properties including dielectric functions, absorption coefficient, transmittance, and reflectance, as a function of wavelength and incident energy, are studied. Refractive index and extinction coefficient of pristine graphene are presented. A key optical property in the infrared region, emissivity, is studied as a function of wavelength for various multilayered configurations having graphene as one of the constituent layers. Application of such a structure is in the fabrication of a Hot Electron Bolometer (a sensor that operates on the basis of temperature-dependent electrical resistance). Graphene is found to have very high elastic modulus and intrinsic strength. Nanoindentation of graphene sheet is simulated to study the force versus displacement curves. Effects of variation of diameter of indenter, speed of indentation and number of layers of graphene on the mechanical properties are presented. Shrinking size of electronic devices has led to an acute need for thermal management. This

  3. Electronic, mechanical, and thermodynamic properties of americium dioxide

    NASA Astrophysics Data System (ADS)

    Lu, Yong; Yang, Yu; Zheng, Fawei; Wang, Bao-Tian; Zhang, Ping

    2013-10-01

    By performing density functional theory (DFT) +U calculations, we systematically study the electronic, mechanical, tensile, and thermodynamic properties of AmO2. It is found that the chemical bonding character in AmO2 is similar to that in PuO2, with smaller charge transfer and stronger covalent interactions between americium and oxygen atoms. The stress-strain relationship of AmO2 is examined along the three low-index directions, showing that the [1 0 0] and [1 1 1] directions are the strongest and weakest tensile directions, respectively, but the theoretical tensile strengths of AmO2 are smaller than those of PuO2. The phonon dispersion curves of AmO2 are calculated and the heat capacities as well as lattice expansion curve are subsequently determined. The lattice thermal conductivity of AmO2 is further evaluated and compared with attainable experiments. Our present work integrally reveals various physical properties of AmO2 and can be referenced for technological applications of AmO2 based materials.

  4. Solar Sail Material Performance Property Response to Space Environmental Effects

    NASA Technical Reports Server (NTRS)

    Edwards, David L.; Semmel, Charles; Hovater, Mary; Nehls, Mary; Gray, Perry; Hubbs, Whitney; Wertz, George

    2004-01-01

    The National Aeronautics and Space Administration's (NASA) Marshall Space Flight Center (MSFC) continues research into the utilization of photonic materials for spacecraft propulsion. Spacecraft propulsion, using photonic materials, will be achieved using a solar sail. A solar sail operates on the principle that photons, originating from the sun, impart pressure to the sail and therefore provide a source for spacecraft propulsion. The pressure imparted to a solar sail can be increased, up to a factor of two if the sun-facing surface is perfectly reflective. Therefore, these solar sails are generally composed of a highly reflective metallic sun-facing layer, a thin polymeric substrate and occasionally a highly emissive back surface. Near term solar sail propelled science missions are targeting the Lagrange point 1 (L1) as well as locations sunward of L1 as destinations. These near term missions include the Solar Polar Imager' and the L1 Diamond '. The Environmental Effects Group at NASA's Marshall Space Fliglit Center (MSFC) continues to actively characterize solar sail material in preparation for these near term solar sail missions. Previous investigations indicated that space environmental effects on sail material thermo-optical properties were minimal and would not significantly affect the propulsion efficiency of the sail3-'. These investigations also indicated that the sail material mechanical stability degrades with increasing radiation exposure. This paper will further quantify the effect of space environmental exposure on the mechanical properties of candidate sail materials. Candidate sail materials for these missions include Aluminum coated Mylar TM, Teonexm, and CP1 (Colorless Polyimide). These materials were subjected to uniform radiation doses of electrons and protons in individual exposures sequences. Dose values ranged from 100 Mrads to over 5 Grads. The engineering performance property responses of thermo-optical and mechanical properties were

  5. Solar Sail Material Performance Property Response to Space Environmental Effects

    NASA Technical Reports Server (NTRS)

    Edwards, David L.; Semmel, Charles; Hovater, Mary; Nehls, Mary; Gray, Perry; Hubbs, Whitney; Wertz, George

    2004-01-01

    The National Aeronautics and Space Administration's (NASA) Marshall Space Flight Center (MSFC) continues research into the utilization of photonic materials for spacecraft propulsion. Spacecraft propulsion, using photonic materials, will be achieved using a solar sail. A solar sail operates on the principle that photons, originating from the sun, impart pressure to the sail and therefore provide a source for spacecraft propulsion. The pressure imparted to a solar sail can be increased, up to a factor of two if the sun-facing surface is perfectly reflective. Therefore, these solar sails are generally composed of a highly reflective metallic sun-facing layer, a thin polymeric substrate and occasionally a highly emissive back surface. Near term solar sail propelled science missions are targeting the Lagrange point 1 (L1) as well as locations sunward of L1 as destinations. These near term missions include the Solar Polar Imager' and the L1 Diamond '. The Environmental Effects Group at NASA's Marshall Space Fliglit Center (MSFC) continues to actively characterize solar sail material in preparation for these near term solar sail missions. Previous investigations indicated that space environmental effects on sail material thermo-optical properties were minimal and would not significantly affect the propulsion efficiency of the sail3-'. These investigations also indicated that the sail material mechanical stability degrades with increasing radiation exposure. This paper will further quantify the effect of space environmental exposure on the mechanical properties of candidate sail materials. Candidate sail materials for these missions include Aluminum coated Mylar TM, Teonexm, and CP1 (Colorless Polyimide). These materials were subjected to uniform radiation doses of electrons and protons in individual exposures sequences. Dose values ranged from 100 Mrads to over 5 Grads. The engineering performance property responses of thermo-optical and mechanical properties were

  6. Mechanical properties of laser welded aluminum alloys

    SciTech Connect

    Douglass, D.M.; Mazumder, J.

    1996-12-31

    The demand for lighter weight vehicles has prompted accelerated development in processing aluminum alloys for automobile structural applications. One of the current research initiatives centers on laser beam welding of aluminum alloys. Autogenous butt welds have been performed on Al 3003, 5754, 6111, and 6061-T6 plates with a 6 kW CO2 laser. For 6061, tensile data indicate about 60% of the base metal strength was attained in the as-welded condition, with a brittle fracture occurring through the weld. A post-weld heat treatment to the T6 condition resulted in a recovery of original ultimate tensile strengths, although these also failed in the weld. Hardness measurements of the post-weld T6 reveal a uniform hardness across the HAZ and fusion zone that is comparable to the original hardness. All 3003 welds fractured in the parent material in a ductile fashion. A high quality bead was consistently achieved with the 3003 alloy, whereas the other alloys demonstrated bead irregularities. SEM photographs reveal large, spherical pores, suggesting that they were formed by gas entrapment rather than by shrinkage.

  7. Mechanical Properties of Shock-Damaged Rocks

    NASA Technical Reports Server (NTRS)

    He, Hongliang; Ahrens, T. J.

    1994-01-01

    Stress-strain tests were performed both on shock-damaged gabbro and limestone. The effective Young's modulus decreases with increasing initial damage parameter value, and an apparent work-softening process occurs prior to failure. To further characterize shock-induced microcracks, the longitudinal elastic wave velocity behavior of shock-damaged gabbro in the direction of compression up to failure was measured using an acoustic transmission technique under uniaxial loading. A dramatic increase in velocity was observed for the static compressive stress range of 0-50 MPa. Above that stress range, the velocity behavior of lightly damaged (D(sub 0) less than 0.1) gabbro is almost equal to unshocked gabbro. The failure strength of heavily-damaged (D(sub 0) greater than 0.1) gabbro is approx. 100-150 MPa, much lower than that of lightly damaged and unshocked gabbros (approx. 230-260 MPa). Following Nur's theory, the crack shape distribution was analyzed. The shock-induced cracks in gabbro appear to be largely thin penny-shaped cracks with c/a values below 5 x 10(exp -4). Moreover, the applicability of Ashby and Sammis's theory relating failure strength and damage parameter of shock-damaged rocks was examined and was found to yield a good estimate of the relation of shock-induced deficit in elastic modulus with the deficit in compressive strength.

  8. Mechanical Properties and Durability of "Waterless Concrete"

    NASA Technical Reports Server (NTRS)

    Toutanji, Houssam; Grugel, Richard N.

    2008-01-01

    Waterless concrete consists of molten elementary sulfur and aggregate. The aggregates in lunar environment will be lunar rocks and soil. Sulfur is present on the Moon in Troilite soil (FeS) and by oxidation soil iron and sulfur can be produced. Iron can be used to reinforce the sulfur concrete. Sulfur concrete specimens were cycled between liquid nitrogen (approximately 191 C) and room temperature (approximately 21 C) to simulate exposure to a lunar environment. Cycled and control specimens were subsequently tested in compression at room temperatures (approximately 21 C) and approximately 101 C. Test results showed that due to temperature cycling, compressive strength of cycled specimens was 20% of those non-cycled. Microscopic examination of the fracture surfaces from the cycled samples showed clear de-bonding of the sulfur from the aggregate material whereas it was seen well bonded in those non-cycled. This reduction in strength can be attributed to the large differences in thermal coefficients of expansion of the materials constituting the concrete which promoted cracking. Similar sulfur concrete mixtures were strengthened with short and long glass fibers. The glass fibers from lunar regolith simulant was melted in a 25 cc Pt-Rh crucible in a Sybron Thermoline high temperature MoSi2 furnace at melting temperatures of 1450 to 1600 C for times of 30 min to 1 hour. Glass fibers were cast from the melt into graphite crucibles and were annealed for a couple of hours at 600 C. Glass fibers and small rods were pulled from the melt. The glass melt wets the ceramic rod and long continuous glass fibers were easily hand drawn. The glass fibers were immediately coated with a protective polymer to maintain the mechanical strength. The glass fibers were used to reinforce sulfur concrete plated to improve the flexural strength of the sulfur concrete. Prisms beams strengthened with glass fibers were tested in 4-point bending test. Beams strengthened with glass fiber showed to

  9. Mechanical Properties and Durability of "Waterless Concrete"

    NASA Technical Reports Server (NTRS)

    Toutanji, Houssam; Grugel, Richard N.

    2008-01-01

    Waterless concrete consists of molten elementary sulfur and aggregate. The aggregates in lunar environment will be lunar rocks and soil. Sulfur is present on the Moon in Troilite soil (FeS) and by oxidation soil iron and sulfur can be produced. Iron can be used to reinforce the sulfur concrete. Sulfur concrete specimens were cycled between liquid nitrogen (approximately 191 C) and room temperature (approximately 21 C) to simulate exposure to a lunar environment. Cycled and control specimens were subsequently tested in compression at room temperatures (approximately 21 C) and approximately 101 C. Test results showed that due to temperature cycling, compressive strength of cycled specimens was 20% of those non-cycled. Microscopic examination of the fracture surfaces from the cycled samples showed clear de-bonding of the sulfur from the aggregate material whereas it was seen well bonded in those non-cycled. This reduction in strength can be attributed to the large differences in thermal coefficients of expansion of the materials constituting the concrete which promoted cracking. Similar sulfur concrete mixtures were strengthened with short and long glass fibers. The glass fibers from lunar regolith simulant was melted in a 25 cc Pt-Rh crucible in a Sybron Thermoline high temperature MoSi2 furnace at melting temperatures of 1450 to 1600 C for times of 30 min to 1 hour. Glass fibers were cast from the melt into graphite crucibles and were annealed for a couple of hours at 600 C. Glass fibers and small rods were pulled from the melt. The glass melt wets the ceramic rod and long continuous glass fibers were easily hand drawn. The glass fibers were immediately coated with a protective polymer to maintain the mechanical strength. The glass fibers were used to reinforce sulfur concrete plated to improve the flexural strength of the sulfur concrete. Prisms beams strengthened with glass fibers were tested in 4-point bending test. Beams strengthened with glass fiber showed to

  10. Mechanical properties of carbon nanotube/polymer composites

    NASA Astrophysics Data System (ADS)

    Arash, B.; Wang, Q.; Varadan, V. K.

    2014-10-01

    The remarkable mechanical properties of carbon nanotubes, such as high elastic modulus and tensile strength, make them the most ideal and promising reinforcements in substantially enhancing the mechanical properties of resulting polymer/carbon nanotube composites. It is acknowledged that the mechanical properties of the composites are significantly influenced by interfacial interactions between nanotubes and polymer matrices. The current challenge of the application of nanotubes in the composites is hence to determine the mechanical properties of the interfacial region, which is critical for improving and manufacturing the nanocomposites. In this work, a new method for evaluating the elastic properties of the interfacial region is developed by examining the fracture behavior of carbon nanotube reinforced poly (methyl methacrylate) (PMMA) matrix composites under tension using molecular dynamics simulations. The effects of the aspect ratio of carbon nanotube reinforcements on the elastic properties, i.e. Young's modulus and yield strength, of the interfacial region and the nanotube/polymer composites are investigated. The feasibility of a three-phase micromechanical model in predicting the elastic properties of the nanocomposites is also developed based on the understanding of the interfacial region.

  11. Mechanical properties of carbon nanotube/polymer composites

    PubMed Central

    Arash, B.; Wang, Q.; Varadan, V. K.

    2014-01-01

    The remarkable mechanical properties of carbon nanotubes, such as high elastic modulus and tensile strength, make them the most ideal and promising reinforcements in substantially enhancing the mechanical properties of resulting polymer/carbon nanotube composites. It is acknowledged that the mechanical properties of the composites are significantly influenced by interfacial interactions between nanotubes and polymer matrices. The current challenge of the application of nanotubes in the composites is hence to determine the mechanical properties of the interfacial region, which is critical for improving and manufacturing the nanocomposites. In this work, a new method for evaluating the elastic properties of the interfacial region is developed by examining the fracture behavior of carbon nanotube reinforced poly (methyl methacrylate) (PMMA) matrix composites under tension using molecular dynamics simulations. The effects of the aspect ratio of carbon nanotube reinforcements on the elastic properties, i.e. Young's modulus and yield strength, of the interfacial region and the nanotube/polymer composites are investigated. The feasibility of a three-phase micromechanical model in predicting the elastic properties of the nanocomposites is also developed based on the understanding of the interfacial region. PMID:25270167

  12. Mechanical properties of carbon nanotubes and their polymer nanocomposites.

    PubMed

    Miyagawa, Hiroaki; Misra, Manjusri; Mohanty, Amar K

    2005-10-01

    More than 10 years have passed since carbon nanotubes (CNT) have been found during observations by transmission electron microscopy (TEM). Since then, one of the major applications of the CNT is the reinforcements of plastics in processing composite materials, because it was found by experiments that CNT possessed splendid mechanical properties. Various experimental methods are conducted in order to understand the mechanical properties of varieties of CNT and CNT-based composite materials. The systematized data of the past research results of CNT and their nanocomposites are extremely useful to improve processing and design criteria for new nanocomposites in further studies. Before the CNT observations, vapor grown carbon fibers (VGCF) were already utilized for composite applications, although there have been only few experimental data about the mechanical properties of VGCF. The structure of VGCF is similar to that of multi-wall carbon nanotubes (MWCNT), and the major benefit of VGCF is less commercial price. Therefore, this review article overviews the experimental results regarding the various mechanical properties of CNT, VGCF, and their polymer nanocomposites. The experimental methods and results to measure the elastic modulus and strength of CNT and VGCF are first discussed in this article. Secondly, the different surface chemical modifications for CNT and VGCF are reviewed, because the surface chemical modifications play an important role for polymer nanocomposite processing and properties. Thirdly, fracture and fatigue properties of CNT/polymer nanocomposites are reviewed, since these properties are important, especially when these new nanocomposite materials are applied for structural applications.

  13. Salt-leached silk scaffolds with tunable mechanical properties.

    PubMed

    Yao, Danyu; Dong, Sen; Lu, Qiang; Hu, Xiao; Kaplan, David L; Zhang, Bingbo; Zhu, Hesun

    2012-11-12

    Substrate mechanical properties have remarkable influences on cell behavior and tissue regeneration. Although salt-leached silk scaffolds have been used in tissue engineering, applications in softer tissue regeneration can be encumbered with excessive stiffness. In the present study, silk-bound water interactions were regulated by controlling processing to allow the preparation of salt-leached porous scaffolds with tunable mechanical properties. Increasing silk-bound water interactions resulted in reduced silk II (β-sheet crystal) formation during salt-leaching, which resulted in a modulus decrease in the scaffolds. The microstructures as well as degradation behavior were also changed, implying that this water control and salt-leaching approach can be used to achieve tunable mechanical properties. Considering the utility of silk in various fields of biomedicine, the results point to a new approach to generate silk scaffolds with controllable properties to better mimic soft tissues by combining scaffold preparation methods and silk self-assembly in aqueous solutions.

  14. Mechanical Properties and Tableting Behavior of Amorphous Solid Dispersions.

    PubMed

    Patel, Sarsvat; Kou, Xiang; Hou, Hao Helen; Huang, Ye Bill; Strong, John C; Zhang, Geoff G Z; Sun, Changquan Calvin

    2017-01-01

    Amorphous solid dispersions (ASDs) consisting of acetaminophen (APAP) and copovidone were systematically studied to identify effects of drug loading and moisture content on mechanical properties, thermal properties, and tableting behavior. ASDs containing APAP at different levels were prepared by film casting and characterized by differential scanning calorimetry and nanoindentation. The glass transition temperature (Tg) continuously decreased with increasing amount of APAP, but the hardness of ASDs was increased at a low APAP content and reduced at high APAP content. This in turn significantly influenced tablet quality. Water reduced both the hardness and Tg of ASDs, and the APAP loading level corresponding to the transition to the softening mechanism was lower at a higher relative humidity. Overall, the mechanical properties, rather than the thermal properties, better represent the plasticization/antiplasticization effect of small molecule to ASDs. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  15. Mechanical Properties of Isotactic Polypropylene Modified with Thermoplastic Potato Starch

    NASA Astrophysics Data System (ADS)

    Knitter, M.; Dobrzyńska-Mizera, M.

    2015-05-01

    In this paper selected mechanical properties of isotactic polypropylene (iPP) modified with potato starch have been presented. Thermoplastic starch (TPS) used as a modifier in the study was produced from potato starch modified with glycerol. Isotactic polypropylene/thermoplastic potato starch composites (iPP/TPS) that contained 10, 30, 50 wt.% of modified starch were examined using dynamic mechanical-thermal analysis, static tensile, Brinell hardness, and Charpy impact test. The studies indicated a distinct influence of a filler content on the mechanical properties of composites in comparison with non-modified polypropylene.

  16. Statistical properties of high performance cesium standards

    NASA Technical Reports Server (NTRS)

    Percival, D. B.

    1973-01-01

    The intermediate term frequency stability of a group of new high-performance cesium beam tubes at the U.S. Naval Observatory were analyzed from two viewpoints: (1) by comparison of the high-performance standards to the MEAN(USNO) time scale and (2) by intercomparisons among the standards themselves. For sampling times up to 5 days, the frequency stability of the high-performance units shows significant improvement over older commercial cesium beam standards.

  17. Mechanical Properties Comparing Composite Fiber Length to Amalgam

    PubMed Central

    Petersen, Richard C.; Liu, Perng-Ru

    2016-01-01

    Photocure fiber-reinforced composites (FRCs) with varying chopped quartz-fiber lengths were incorporated into a dental photocure zirconia-silicate particulate-filled composite (PFC) for mechanical test comparisons with a popular commercial spherical-particle amalgam. FRC lengths included 0.5-mm, 1.0 mm, 2.0 mm, and 3.0 mm all at a constant 28.2 volume percent. Four-point fully articulated fixtures were used according to American Standards Test Methods with sample dimensions of 2×2×50 mm3 across a 40 mm span to provide sufficient Euler flexural bending and prevent top-load compressive shear error. Mechanical properties for flexural strength, modulus, yield strength, resilience, work of fracture, critical strain energy release, critical stress intensity factor, and strain were obtained for comparison. Fiber length subsequently correlated with increasing all mechanical properties, p < 1.1×10−5. Although the modulus was significantly statistically higher for amalgam than all composites, all FRCs and even the PFC had higher values than amalgam for all other mechanical properties. Because amalgams provide increased longevity during clinical use compared to the standard PFCs, modulus would appear to be a mechanical property that might sufficiently reduce margin interlaminar shear stress and strain-related microcracking that could reduce failure rates. Also, since FRCs were tested with all mechanical properties that statistically significantly increased over the PFC, new avenues for future development could be provided toward surpassing amalgam in clinical longevity. PMID:27642629

  18. Effects of Microwave Radiation on Selected Mechanical Properties of Silk

    NASA Astrophysics Data System (ADS)

    Reed, Emily Jane

    Impressive mechanical properties have served to peak interest in silk as an engineering material. In addition, the ease with which silk can be altered through processing has led to its use in various biomaterial applications. As the uses of silk branch into new territory, it is imperative (and inevitable) to discover the boundary conditions beyond which silk no longer performs as expected. These boundary conditions include factors as familiar as temperature and humidity, but may also include other less familiar contributions, such as exposure to different types of radiation. The inherent variations in mechanical properties of silk, as well as its sensitivity to moisture, suggest that in an engineering context silk is best suited for use in composite materials; that way, silk can be shielded from ambient moisture fluctuations, and the surrounding matrix allows efficient load transfer from weaker fibers to stronger ones. One such application is to use silk as a reinforcing fiber in epoxy composites. When used in this way, there are several instances in which exposure to microwave radiation is likely (for example, as a means of speeding epoxy cure rates), the effects of which remain mostly unstudied. It will be the purpose of this dissertation to determine whether selected mechanical properties of B. mori cocoon silk are affected by exposure to microwave radiation, under specified temperature and humidity conditions. Results of our analyses are directly applicable wherever exposure of silk to microwave radiation is possible, including in fiber reinforced epoxy composites (the entire composite may be microwaved to speed epoxy cure time), or when silk is used as a component in the material used to construct the radome of an aircraft (RADAR units use frequencies in the microwave range of the electromagnetic spectrum), or when microwave energy is used to sterilize biomaterials (such as cell scaffolds) made of silk. In general, we find that microwave exposure does not

  19. Mechanical Properties and Microstructure Investigation of Lead Free Solder

    NASA Technical Reports Server (NTRS)

    Wang, Qing; Gail, William F.; Johnson, R. Wayne; Strickland, Mark; Blanche, Jim

    2005-01-01

    While the electronics industry appears to be focusing on Sn-Ag-Cu as the alloy of choice for lead free electronics assembly, ,the exact composition varies by geographic region, supplier and user. Add to that dissolved copper and silver from the printed circuit board traces and surface finish, and there can be significant variation in the final solder joint composition. A systematic study of the mechanical and microstructural properties of Sn-Ag-Cu alloys with Ag varying from 2wt% to 4wt% and Cu varying from 0.5wt% to lSwt%, was undertaken in this research study. Different sample preparation techniques (water quenched, oil quenched and water quenched followed by reflow) were explored and the resulting microstructure compared to that of a typical reflowed lead free chip scale package (CSP) solder joint. Tensile properties (modulus, 0.2% yield strength and the ultimate tensile strength) and creep behavior of selected alloy compositions (Sn-4Ag-1 X u , Sn-4Ag-OSCu, Sn- 2Ag-1 X u , Sn-2Ag-OSCu, Sn-3.5Ag-O.SCu) were determined for three conditions: as- cast; aged for 100 hours at 125OC; and aged for 250 hours at 125OC. There was no significant difference in Young's Modulus as a function of alloy composition. After an initial decrease in modulus after 100 hours at 125"C, there was an insignificant change with further aging. The distribution of 0.2% strain yield stress and ultimate tensile strength as a function of alloy composition was more significant and decreased with aging time and temperature. The microstructures of these alloys were examined using light and scanning electron microscopy (LM and SEM) respectively and SEM based energy dispersive x-ray spectroscopy (EDS). Fracture surface and cross-section analysis were performed on the specimens after creep testing. The creep testing results and the effect of high temperature aging on mechanical properties is presented for the oil quenched samples. In general the microstructure of oil quenched specimen exhibited a

  20. Mechanical Properties of High Purity Niobium - Novel Measurements

    SciTech Connect

    Ganapati Myneni

    2003-09-01

    One of the procedures to improve the performance of superconducting niobium cavities is a heat treatment for several hours in an ultrahigh vacuum at temperatures between 800C and 1400C for hydrogen degassing or post-purification, respectively. However, it was recently observed with Spallation Neutron Source Project (SNS) prototype cavities, that a heat treatment at 800 C for even 1 hour degraded the mechanical properties of RRR niobium, in particular the yield strength. This lower strength resulted in cavity deformations during handling thus affecting both their resonant frequency and field profile. In addition to lowering the yield strength, it was observed in some lots of material that the Young's modulus was also apparently reduced by a factor of 2 as a result of the hydrogen outgassing at 800 C. Surprisingly, material received at other national laboratories exhibited similar anomalous behavior even without any heat treatments in vacuum. Based on these observations a multi-institutional collaborative basic research activity on high RRR niobium (determination of Nb yield strength as a function of grain size, work hardening, chemical composition, and heat treatment temperature) has been initiated by JLAB to gain a better understanding of the material properties affecting the mechanical behavior In this contribution, a brief review of the measurements at JLAB, at the Materials Science and Engineering Department of the University of Virginia, at the Analytical Chemistry and Metallurgy Divisions of the National Institute of Standard and Technology, Gaithersburg and in the Department of Physics, SUNY, Albany are presented. The measurements include yield strength, hardness, ultrasonic velocity, crystallographic structure, microstructure, determination of interstitial contents using internal friction; particular emphasis is placed on determining the hydrogen concentration in the niobium via Cold Neutron Prompt Gamma-Ray Activation Analysis and Neutron Incoherent

  1. Preparation and Mechanical Properties of Graphene Oxide: Cement Nanocomposites

    PubMed Central

    Babak, Fakhim; Abolfazl, Hassani; Alimorad, Rashidi; Parviz, Ghodousi

    2014-01-01

    We investigate the performance of graphene oxide (GO) in improving mechanical properties of cement composites. A polycarboxylate superplasticizer was used to improve the dispersion of GO flakes in the cement. The mechanical strength of graphene-cement nanocomposites containing 0.1–2 wt% GO and 0.5 wt% superplasticizer was measured and compared with that of cement prepared without GO. We found that the tensile strength of the cement mortar increased with GO content, reaching 1.5%, a 48% increase in tensile strength. Ultra high-resolution field emission scanning electron microscopy (FE-SEM) used to observe the fracture surface of samples containing 1.5 wt% GO indicated that the nano-GO flakes were well dispersed in the matrix, and no aggregates were observed. FE-SEM observation also revealed good bonding between the GO surfaces and the surrounding cement matrix. In addition, XRD diffraction data showed growth of the calcium silicate hydrates (C-S-H) gels in GO cement mortar compared with the normal cement mortar. PMID:24574878

  2. Mechanical properties of copper octet-truss nanolattices

    NASA Astrophysics Data System (ADS)

    He, ZeZhou; Wang, FengChao; Zhu, YinBo; Wu, HengAn; Park, Harold S.

    We investigate the mechanical properties of copper (Cu) octet-truss nanolattices through a combination of classical molecular dynamics (MD) simulations and theoretical analysis. The MD simulations show that Cu nanolattices with high relative density are stronger than bulk Cu, while also achieving higher strength at a lower relative density as compared to Cu meso-lattices. We demonstrate that modifying the classical octet-truss lattice model by accounting for nodal volume and bending effects through the free body diagram method is critical to obtaining good agreement between the theoretical model and the MD simulations. In particular, we find that as the relative density increases, nodal volume is the key factor governing the stiffness scaling of the nanolattices, while bending dominates the strength scaling. Most surprisingly, our analytic modeling shows that surface effects have little influence on the stiffness and strength scaling of the nanolattices, even though the cross sectional sizes of the nanowires that act as the lattice struts are on the order of 6 nm or smaller. This is because, unlike for individual nanowires, the mechanical response of the nanowire struts that form the nanolattice structure is also a function of bending and nodal volume effects, all of which depend nonlinearly on the nanolattice relative density. Overall, these results imply that nanoscale architected materials can access a new regime of architected material performance by simultaneously achieving ultrahigh strength and low density.

  3. Bioactive glass/hydroxyapatite composites: mechanical properties and biological evaluation.

    PubMed

    Bellucci, Devis; Sola, Antonella; Anesi, Alexandre; Salvatori, Roberta; Chiarini, Luigi; Cannillo, Valeria

    2015-06-01

    Bioactive glass/hydroxyapatite composites for bone tissue repair and regeneration have been produced and discussed. The use of a recently developed glass, namely BG_Ca/Mix, with its low tendency to crystallize, allowed one to sinter the samples at a relatively low temperature thus avoiding several adverse effects usually reported in the literature, such as extensive crystallization of the glassy phase, hydroxyapatite (HA) decomposition and reaction between HA and glass. The mechanical properties of the composites with 80wt.% BG_Ca/Mix and 20wt.% HA are sensibly higher than those of Bioglass® 45S5 reference samples due to the presence of HA (mechanically stronger than the 45S5 glass) and to the thermal behaviour of the BG_Ca/Mix, which is able to favour the sintering process of the composites. Biocompatibility tests, performed with murine fibroblasts BALB/3T3 and osteocites MLO-Y4 throughout a multi-parametrical approach, allow one to look with optimism to the produced composites, since both the samples themselves and their extracts do not induce negative effects in cell viability and do not cause inhibition in cell growth.

  4. Preparation and mechanical properties of graphene oxide: cement nanocomposites.

    PubMed

    Babak, Fakhim; Abolfazl, Hassani; Alimorad, Rashidi; Parviz, Ghodousi

    2014-01-01

    We investigate the performance of graphene oxide (GO) in improving mechanical properties of cement composites. A polycarboxylate superplasticizer was used to improve the dispersion of GO flakes in the cement. The mechanical strength of graphene-cement nanocomposites containing 0.1-2 wt% GO and 0.5 wt% superplasticizer was measured and compared with that of cement prepared without GO. We found that the tensile strength of the cement mortar increased with GO content, reaching 1.5%, a 48% increase in tensile strength. Ultra high-resolution field emission scanning electron microscopy (FE-SEM) used to observe the fracture surface of samples containing 1.5 wt% GO indicated that the nano-GO flakes were well dispersed in the matrix, and no aggregates were observed. FE-SEM observation also revealed good bonding between the GO surfaces and the surrounding cement matrix. In addition, XRD diffraction data showed growth of the calcium silicate hydrates (C-S-H) gels in GO cement mortar compared with the normal cement mortar.

  5. Mechanical properties of an artificial vascularized human skin

    NASA Astrophysics Data System (ADS)

    Passot, A.; Cabodevila, G.

    2011-05-01

    In order to make blood sample tests an artificial skin similar to that of the baby's heel is modeled and realized. The most superficial bloodstream and the two main layers of the skin -epidermis and dermis- have to be recreated. Studies and capillaroscopies of the baby's heel give characteristics of these layers and the bloodstream. The skin is viscohyperelastic, but the choice of materials that will be used is based on the Young's modulus. The epidermis layer is based on a stronger less adhesive silicon rubber Elastosil. The dermis layer is composed of a mixture based on a very soft sticky silicon rubber Silgel and Sylgard. The mixture of Silgel with 5% Sylgard has an elastic modulus of 48 kPa which is similar to that of the dermis. The artificial skin is an assembly of several layers including a layer of Sylgard that is structured by a mold representing the capillary network and adapted to manufacturing processes in a clean room. Each layer is deposited by spin coating and is combined with the other through adhesion. Mechanical tests such as tension are performed to verify the mechanical properties of the artificial skin.

  6. Mechanical Properties of Single Collagen Fibrils Revealed by Force Spectroscopy

    NASA Astrophysics Data System (ADS)

    Graham, John; Phillips, Charlotte; Grandbois, Michel

    2004-03-01

    In the field of biomechanics, collagen fibrils are believed to be robust mechanical structures characterized by a low extensibility. Until very recently, information on the mechanical properties of collagen fibrils could only be derived from ensemble measurements performed on complete tissues such as bone, skin and tendon. Here we measure force-elongation/relaxation profiles of single collagen fibrils using atomic force microscopy-based force spectroscopy. The elongation profiles indicate that in vitro assembled heterotrimeric type I collagen fibrils are characterized by a large extensibility. Numerous discontinuities and a plateau in the force profile indicate major reorganization occurs within the fibrils in the 1.5 -- 4.5 nN range. Our study demonstrates that newly assembled collagen fibrils are robust structures with a significant reserve of elasticity that could play a determinant role in cellular motion in the context of tissue growth and morphogenesis. In contrast, homotrimeric collagen fibrils corresponding to osteogenesis imperfecta pathology exhibit a marked difference in their elasticity profile.

  7. Mechanical performance improvement of electroactive papers

    NASA Astrophysics Data System (ADS)

    Kim, Jaehwan; Seo, Yung B.; Jung, Eunmi

    2001-07-01

    Electro-Active Paper (EAPap) is a paper that produces large displacement with small force under electrical excitation. EAPap is made with a chemically treated paper by bonding thin aluminum foils on both sides of the paper to comprise electrodes. When electric voltage is applied on the electrodes the EAPap produces bending displacement. However, the displacement output has been unstable and degraded with time scale. To improve the bending performance of EAPap, different paper fibers-broad-leaf, needle-leaf, bacteria cellulose and Korean traditional paper, and additive chemicals are tested. It was observed that needle-leaf paper exhibits better results then others. By eliminating the effect of adhesive layer and selecting a proper paper fiber, the displacement output has been stable with long time scale. The operational principle of EAPap is, we believe, based on the electrostriction effect associated with intermolecular interaction of the constituents of the paper. To confirm this result, more investigation of the paper quality should be followed in the beginning of paper manufacturing process. Since EAPaps are quite simple to fabricate and lightweight, various applications including flexible speakers, active sound absorbing materials and smart shape control devices can be possible.

  8. Coupling of mechanical and electronic properties of carbon nanotubes.

    PubMed

    Cristancho, Dahiyana; Benitez, Laura; Seminario, Jorge M

    2013-12-01

    Because of the potential importance of carbon nanotubes (CNT) in renewable energy and other fields, molecular orbital ab initio calculations are used to study the relation between mechanical and electronic properties of such structures. We estimate a modulus of elasticity of 1.3 TPa and find out that the mechanism of CNT structure deformation is dependent on their chirality. Armchair and chiral nanotubes have ductile deformation fracture while zigzag have both ductile and brittle; on the other hand armchair nanotubes fracture and form two caps while chiral nanotubes adopt a helical-structure conformation. In addition, the energy gap between occupied and unoccupied molecular orbitals increases when nanotubes are under plastic deformation. This strong coupling between mechanical and electrical properties can be used to tune CNT mechanically to specific electronic bandgaps, affecting directly their electromagnetic absorption properties.

  9. Mechanics of intraply hybrid composites - Properties, analysis and design

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1979-01-01

    A mechanics theory is developed for predicting the physical thermal, hygral and mechanical properties (including various strengths) of unidirectional intraply hybrid composites (UIHC) based on unidirectional properties of the constituent composites. Procedures are described which can use this theory in conjunction with composite mechanics computer codes and general purpose structural analysis finite element programs for the analysis/design of structural components made from intraply hybrid angleplied laminates (IHAL). Comparisons with limited data show that this theory predicts mechanical properties of UIHC and flexural stiffnesses of IHAL which are in good agreement with experimental data. The theory developed herein makes it possible to design and optimize structural components from IHAL based on a large class of available constituent fibers.

  10. Significantly enhanced mechanical properties in AlN helix

    NASA Astrophysics Data System (ADS)

    Zhang, Xinghong; Zhao, Chaoliang; Yao, Tai; Zhou, Shanbao; Han, Jiecai; Li, Jiajie; Gao, Tangling; Wang, Xianjie; Zheng, Kun; Song, Bo

    2017-07-01

    To safely and reliably use aluminum nitride (AlN) helices in the fabrication of novel micro/nanodevices, it is very important to know their mechanical properties. Herein, we investigate the mechanical properties of individual AlN helices using an in situ tensile-bending test. Tensile tests reveal that an AlN helix has an average ε of ∼4.7 ± 0.8% elastic deformation before a typical brittle fracture occurs. The bending test shows a two-step mechanical feature—linear-elastic followed by an elastic-plastic process—with an average ε bent of ∼54.5 ± 0.6%. Our results provide direct cognition about the mechanical properties of AlN helices and their benefit to the design of AlN-based flexible micro/nanodevices.

  11. Processing, texture and mechanical properties of sintered silicon carbide

    NASA Technical Reports Server (NTRS)

    Landfermann, H.; Hausner, H.

    1988-01-01

    With regard to its favorable properties, in particular those shown at high temperatures, silicon carbide is of great interest for applications related to the construction of engines and turbines. Thus, silicon carbide could replace heat-resisting alloys with the objective to achieve a further increase in operational temperature. The present investigation is concerned with approaches which can provide silicon carbide material with suitable properties for the intended applications, taking into account the relations between characteristics of the raw material, material composition, sinter conditions, and results of the sintering process. The effects of density and texture formation on the mechanical properties are studied. It is found that a dense material with a fine-grained microstructure provides optimal mechanical properties, while any deviation from this ideal condition can lead to a considerable deterioration with respect to the material properties.

  12. Relating Interface Evolution to Interface Mechanics Based on Interface Properties

    NASA Astrophysics Data System (ADS)

    Verma, Devendra; Biswas, Sudipta; Prakash, Chandra; Tomar, Vikas

    2017-01-01

    The current article focuses on recent work done in understanding the role of processing techniques on interface evolution and connecting interface evolution to interface thickness-dependent properties. Special emphasis is placed on interface evolution during the sintering process of tungsten ( W). Sintering with additives such as nickel significantly changes grain boundary properties in W, leading to issues such as grain boundary embrittlement. When one has to mechanically describe properties of polycrystalline W with an account of the influence of grain boundary embrittlement, one must explicitly consider grain boundary properties. This issue is the focus of the present work on the mechanical properties of interfaces. Overall, a phase field modeling-based approach is shown to be an excellent computational tool for predicting the interface evolution. The influences of the interface thickness, chemistry, and orientation of phases around interfaces are analyzed using extended finite element simulations for polycrystalline W.

  13. The global mechanical properties and multi-scale failure mechanics of heterogeneous human stratum corneum.

    PubMed

    Liu, X; Cleary, J; German, G K

    2016-10-01

    The outermost layer of skin, or stratum corneum, regulates water loss and protects underlying living tissue from environmental pathogens and insults. With cracking, chapping or the formation of exudative lesions, this functionality is lost. While stratum corneum exhibits well defined global mechanical properties, macroscopic mechanical testing techniques used to measure them ignore the structural heterogeneity of the tissue and cannot provide any mechanistic insight into tissue fracture. As such, a mechanistic understanding of failure in this soft tissue is lacking. This insight is critical to predicting fracture risk associated with age or disease. In this study, we first quantify previously unreported global mechanical properties of isolated stratum corneum including the Poisson's ratio and mechanical toughness. African American breast stratum corneum is used for all assessments. We show these parameters are highly dependent on the ambient humidity to which samples are equilibrated. A multi-scale investigation assessing the influence of structural heterogeneities on the microscale nucleation and propagation of cracks is then performed. At the mesoscale, spatially resolved equivalent strain fields within uniaxially stretched stratum corneum samples exhibit a striking heterogeneity, with localized peaks correlating closely with crack nucleation sites. Subsequent crack propagation pathways follow inherent topographical features in the tissue and lengthen with increased tissue hydration. At the microscale, intact corneocytes and polygonal shaped voids at crack interfaces highlight that cracks propagate in superficial cell layers primarily along intercellular junctions. Cellular fracture does occur however, but is uncommon. Human stratum corneum protects the body against harmful environmental pathogens and insults. Upon mechanical failure, this barrier function is lost. Previous studies characterizing the mechanics of stratum corneum have used macroscopic testing

  14. Mechanical properties that influence antimicrobial peptide activity in lipid membranes.

    PubMed

    Marín-Medina, Nathaly; Ramírez, Diego Alejandro; Trier, Steve; Leidy, Chad

    2016-12-01

    Antimicrobial peptides are small amphiphilic proteins found in animals and plants as essential components of the innate immune system and whose function is to control bacterial infectious activity. In order to accomplish their function, antimicrobial peptides use different mechanisms of action which have been deeply studied in view of their potential exploitation to treat antibiotic-resistant bacterial infections. One of the main mechanisms of action of these peptides is the disruption of the bacterial membrane through pore formation, which, in some cases, takes place via a monomer to oligomer cooperative transition. Previous studies have shown that lipid composition, and the presence of exogenous components, such as cholesterol in model membranes or carotenoids in bacteria, can affect the potency of distinct antimicrobial peptides. At the same time, considering the membrane as a two-dimensional material, it has been shown that membrane composition defines its mechanical properties which might be relevant in many membrane-related processes. Nevertheless, the correlation between the mechanical properties of the membrane and antimicrobial peptide potency has not been considered according to the importance it deserves. The relevance of these mechanical properties in membrane deformation due to peptide insertion is reviewed here for different types of pores in order to elucidate if indeed membrane composition affects antimicrobial peptide activity by modulation of the mechanical properties of the membrane. This would also provide a better understanding of the mechanisms used by bacteria to overcome antimicrobial peptide activity.

  15. 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

  16. Process for predicting structural performance of mechanical systems

    DOEpatents

    Gardner, David R.; Hendrickson, Bruce A.; Plimpton, Steven J.; Attaway, Stephen W.; Heinstein, Martin W.; Vaughan, Courtenay T.

    1998-01-01

    A process for predicting the structural performance of a mechanical system represents the mechanical system by a plurality of surface elements. The surface elements are grouped according to their location in the volume occupied by the mechanical system so that contacts between surface elements can be efficiently located. The process is well suited for efficient practice on multiprocessor computers.

  17. Process for predicting structural performance of mechanical systems

    DOEpatents

    Gardner, D.R.; Hendrickson, B.A.; Plimpton, S.J.; Attaway, S.W.; Heinstein, M.W.; Vaughan, C.T.

    1998-05-19

    A process for predicting the structural performance of a mechanical system represents the mechanical system by a plurality of surface elements. The surface elements are grouped according to their location in the volume occupied by the mechanical system so that contacts between surface elements can be efficiently located. The process is well suited for efficient practice on multiprocessor computers. 12 figs.

  18. Cardiac Tissue Structure, Properties, and Performance: A Materials Science Perspective

    PubMed Central

    Golob, Mark; Moss, Richard L.; Chesler, Naomi C.

    2014-01-01

    From an engineering perspective, many forms of heart disease can be thought of as a reduction in biomaterial performance, in which the biomaterial is the tissue comprising the ventricular wall. In materials science, the structure and properties of a material are recognized to be interconnected with performance. In addition, for most measurements of structure, properties, and performance, some processing is required. Here, we review the current state of knowledge regarding cardiac tissue structure, properties, and performance as well as the processing steps taken to acquire those measurements. Understanding the impact of these factors and their interactions may enhance our understanding of heart function and heart failure. We also review design considerations for cardiac tissue property and performance measurements because, to date, most data on cardiac tissue has been obtained under non-physiological loading conditions. Novel measurement systems that account for these design considerations may improve future experiments and lead to greater insight into cardiac tissue structure, properties, and ultimately performance. PMID:25081385

  19. The effects of different size gold nanoparticles on mechanical properties of vascular smooth muscle cells under mechanical stretching

    NASA Astrophysics Data System (ADS)

    Kieu, Tri Minh

    Nanotechnology is an emerging and promising frontier for medicine and biomedical research due to its potential for applications such as drug delivery, imaging enhancement, and cancer treatment. While these materials may possess significant possibilities, the effects of these particles in the body and how the particles affect the cells is not fully understood. In this study, vascular smooth muscle cells (VSMCs) will be exposed to 5 and 20 nm diameter citrate AuNPs under mechanical conditions. The cytotoxicity properties of these particles will be investigated using LDH and MTT assays. Atomic force microscopy will be used to study how the size of the nanoparticles affect the mechanical properties of the VSMCs. Immunofluorescence staining for alpha actin will also be performed to enhance understanding of the phenotypic shift. The LDH and MTT cytotoxicity assay results demonstrated that neither 5 nor 20 nm diameter nanoparticles are cytotoxic to the cells. However, the mechanical properties and cell morphology of the VSMCs was altered. Under static conditions, both AuNP treatments decreased the mechanical properties of the cells. The size of the nanoparticles had a softening effect on elastic modulus of the cell and sign of a synthetic phenotype was observed. The VSMCs subjected to mechanical stretching exhibited higher elastic modulus compared to the static experimental groups. Again, both AuNPs treatments decreased the mechanical properties of the cells and signs of more synthetic phenotype was seen. However, the size of the nanoparticles did not have any influence on cell's elastic modulus unlike the static treated cells. The mechanical testing condition provided a better look at how these particles would affect the cells in vivo. While the nanoparticles are not cytotoxic to the VSMCs, they are altering the mechanical properties and phenotype of the cell.

  20. Structural properties for determining mechanisms of toxic action

    SciTech Connect

    Bradbury, S.P.; Lipnick, R.L.

    1989-01-01

    The results of a workshop co-sponsored by EPA through the Health and Environmental Review Division, Office of Toxic Substances and the Environmental Research Laboratory-Duluth, of the Office of Research and Development are briefly summarized as an introduction to a series of manuscripts dealing with the structural properties of chemicals that determine their toxic mechanisms. Results of the workshop are intended to be incorporated in an expert system to predict mechanisms from chemical structure and aid in predictive toxicology applications in the Agency. The goal of the workshop was to review current understanding of fundamental mechanisms, and develop an initial knowledge base on chemical features and properties from which toxic mechanisms could be predicted from structure. Areas addressed included general anesthesia, or narcosis, oxidative phosphorylation uncoupling, electrophile and free-radical reactivity, and a variety of pesticide-based mechanisms.

  1. 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.

  2. Mechanical properties of basement membrane in health and disease.

    PubMed

    Miller, R Tyler

    2017-01-01

    Physical properties are differentiated characteristics of tissues that are essential to their function. For example, the function of bone depends on its rigidity, and the function of skin depends on its elasticity. The aggregate physical properties of tissues are determined by a collaborative relationship between their cells and matrix and are the product of genetic programs, circulating chemical signals, physical signals, and age. The mechanical properties of matrix and basement membranes in biologic systems are difficult to understand in detail because of their complexity and technical limitations of measurements. Matrix may contain fibrillary collagens, network collagens, other fibrillar proteins such as elastin, fibronectin, and laminins, proteoglycans, and can be a reservoir for growth factors. In each tissue and in different regions of the same tissue, matrix composition can vary. The goal of measuring the mechanical properties of matrix is to understand the physical environment experienced by specific cell types to be able to control cell behavior in vivo and for tissue engineering. At this time, such precise analysis is not possible. The general elastic properties of tissues are now better characterized, and model systems using limited numbers of matrix constituents permit improved understanding of the physical behavior of matrix and its effects on cells. This review will describe model systems for understanding problems of matrix elasticity, focus on a relatively new aspect of matrix mechanics, strain-stiffening, and the interactions of cells with matrix to produce overall tissue mechanical properties.

  3. Mechanical and thermal properties of composite material system reinforced with micro glass balloons

    NASA Astrophysics Data System (ADS)

    Ozawa, Y.; Watanabe, M.; Kikuchi, T.; Ishiwatari, H.

    2010-06-01

    The mechanical and thermal properties of polymer composites reinforced with micro glass balloons are investigated in temperature conditions. The matrix resin of the composite is epoxy resin and its dispersion is micro glassy spherical shells of Sirasu Balloon. The composite system developed is a kind of micro porous materials with lightweight. From the experimental data of bending and tension tests, mechanical behaviours of the composites were clarified, and the effects of material properties and configurations on the mechanical properties of composites were discussed from the viewpoint of micromechanical study. A homogenization theory with multi-scale analytical method has been applied in order to evaluate the composite material system in temperature conditions. Numerical calculations were performed by using a model of micro porous materials and setting properties of each material at the temperature. Analytical results for the mechanical behaviour made a good agreement with experimental result of the composites in temperature conditions.

  4. Modeling of dynamic mechanical properties of polymer composites reinforced by one dimensional nanofillers

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Lu, M.; Chen, M. H.; Wang, L. S.; Bu, Z. X.; Song, G.; Sun, L.

    2016-11-01

    Owing to their high aspect ratio, large specific surface area, high axial Young's modulus/strength, and low density, one dimensional carbon nanomaterials can introduce significant change to the mechanical properties of polymer matrices, both static and dynamic. Thus, one of the most important potential applications of carbon nanotubes or nanofibers is to utilize the enhanced dynamic damping properties of polymer nanocomposites for improved vibration, acoustic, and fatigue performances. This study focuses on calculating the nanocomposite energy dissipation under dynamic mechanical loading. A micromechanical model based on quasi-static stick-slip analysis has been developed to quantify the dynamic mechanical properties of the nanocomposites as a function of external strain in the elastic region. Storage and loss moduli are used to characterize such dynamic mechanical behaviors. Influences of nanotube bundling and nanotube alignment on the damping property of composites have been quantified. Simulation results are in good agreement with the reported experimental measurements.

  5. Mechanical properties of different types of space maintainers

    NASA Astrophysics Data System (ADS)

    Beldiman, M.-A.; Mârţu, I.; Leiţoiu, B.; Luchian, I.; Lupescu, O.; Bârcă, E. S.

    2015-11-01

    Currently, inside the oral cavity, the dental space maintainers are subjected to forces exerted on them when performing various functions; therefore, it is important to know how each of these mechanisms behave and respond to forces that are applied directly to them. The mechanical properties of the materials used in dentistry are defined by a set of characteristics representing the behaviour of their particular working conditions and it is qualitatively expressed by a number of parameters.The study aimed to determine the pressing force that can be taken by four 4 types of space maintainers frequently used in practice - fixed and removable, applied on four samples realized with human teeth extracted for orthodontic purposes. Static tests were carried out on a machine type short WDW-5 EC with a maximum force of 5 kN and a loading speed of 5 mm/min by a special testing machine, with an innovative appliance; data recording was automatically performed, using a computer with a special program that present the specific diagrams. Experimental determinations included the following aspects: to determine the maximum force that can be supported by each sample, and to observe the deformations. The values obtained indicate that the best option in terms of behavior under the conditions specified is the removable appliance, and the less functional version is the fixed space maintainer using brackets. According to tests conducted, the fracture strength was found to be more important for fixed space maintainers (band and loop, for example) so, in practice is using more frequent these types of space maintainers.

  6. The fracture properties and toughening mechanisms of bone and dentin

    NASA Astrophysics Data System (ADS)

    Koester, Kurt John

    The mechanical properties of bone and dentin and in particular their fracture properties, are the subject of intense research. The relevance of these properties is increasing as our population ages and fracture incidence impacts the lives of a greater portion of the population. A robust framework is needed to understand the fracture properties of bone and dentin to guide researchers as they attempt to characterize the effects of aging, disease, and pharmaceutical treatments on the properties of these mineralized tissues. In the present work, this framework is provided and applied to human bone, human dentin, and animal bone. In situ electron microscopy was also used to identify the salient toughening mechanisms in bone and dentin. It was found that bone and dentin are extrinsically toughened materials and consequently their fracture properties are best characterized utilizing a crack-growth resistance approach. A description of the different mechanical measurements commonly employed when using small animal models (rats and mice) to evaluate the influence of drug therapies on bone fragility is provided. A study where these properties were measured for a large population of wild-type rats and mice was also conducted. Given my findings, it was determined that for the most complete understanding of small animal bone it was necessary to measure strength and toughness. Strength measurements probe the flaw distribution and toughness measurements to evaluate the resistance to facture in the presence of a single dominant worst-case flaw.

  7. Mechanical properties of bimetallic crystalline and nanostructured nanowires.

    PubMed

    Hou, Marc; Melikhova, Oksana; Pisov, Stoyan

    2008-01-01

    Nanowires are basic components of interconnects at the nanoscale level in electronic as well as in electromechanical devices. Presently, there is a fast growing interest in their synthesis as well as in their mechanical testing. Focused ion beams now allow machining pillars with diameters as small as a few tens of nanometres and nanoindenter systems allow measuring strains at the atomic scale and compressive stresses up to the 10 GPa range. Such pillars typically contain less than millions of atoms, which makes their modelling and the modelling of their mechanical properties at the atomic scale realistic. A few Molecular Dynamics studies are presently available, discussing deformation mechanisms in thin narrow crystalline nanowires, but the literature about nanoalloy wires and nanostructured wires, as they can be synthesized from clusters, is almost non-existent. In the latter, the dislocation activity may be inhibited, leading to specific mechanical properties. By means of large scale computations, we use Ni3A1 to discuss the mechanical properties of crystalline and nanostructured nanowires. We also compare wires to their bulk counterparts. Both isothermal and isoenergetic whereby mechanical work converts into heat in the system-deformation mechanisms are considered. The comparison between pair correlation functions, stress distributions, configuration analysis and strain stress relations capture most of the stress-induced evolution mechanisms of nanowires with different diameters and structures, including elastic properties, dislocation activity, grain rotation and boundary motion, local melting, superplasticity and fracture. A structural transition which may be martensitic is predicted for the first time at the nanoscale level, suggesting possible shape memory properties of nanoalloy nanowires.

  8. Microstructural influences on the mechanical properties of solder

    SciTech Connect

    Morris, J.W. Jr.; Goldstein, J.L.F.; Mei, Z.

    1993-04-01

    Intent of this book is to review analytic methods for predicting behavior of solder joints, based on continuum mechanics. The solder is treated as a continuous, homogeneous body, or composite of such bodies, whose mechanical behavior is uniform and governed by simple constitutive equations. The microstructure of a solder joint influences its mechanical properties in 3 ways: it governs deformation and failure; common solders deform inhomogeneously; and common solders are microstructurally unstable. The variety of microstructures often found in solder joints are briefly reviewed, and some of the ways are discussed in which the microstructure influences the common types of high-temperature mechanical behavior. 25 figs, 40 refs.

  9. FRAPCON-3: Modifications to fuel rod material properties and performance models for high-burnup application

    SciTech Connect

    Lanning, D.D.; Beyer, C.E.; Painter, C.L.

    1997-12-01

    This volume describes the fuel rod material and performance models that were updated for the FRAPCON-3 steady-state fuel rod performance code. The property and performance models were changed to account for behavior at extended burnup levels up to 65 Gwd/MTU. The property and performance models updated were the fission gas release, fuel thermal conductivity, fuel swelling, fuel relocation, radial power distribution, solid-solid contact gap conductance, cladding corrosion and hydriding, cladding mechanical properties, and cladding axial growth. Each updated property and model was compared to well characterized data up to high burnup levels. The installation of these properties and models in the FRAPCON-3 code along with input instructions are provided in Volume 2 of this report and Volume 3 provides a code assessment based on comparison to integral performance data. The updated FRAPCON-3 code is intended to replace the earlier codes FRAPCON-2 and GAPCON-THERMAL-2. 94 refs., 61 figs., 9 tabs.

  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. Relating chemical structure to the mechanical and electrical properties in organic crystalline semiconductors

    NASA Astrophysics Data System (ADS)

    Reyes-Martinez, Marcos; Crosby, Alfred; Briseno, Alejandro

    2015-03-01

    The study of the physical properties of organic single crystals (OSCs) has allowed the advent of a new generation of high-performance organic electronic devices. Despite the profound knowledge of the structural and electrical properties of OSCs, there is little research on their mechanical properties and the effects of strain on their electrical properties. This presentation brings new understanding of the intrinsic mechanical properties of organic semiconductors and the effect of deformation in charge transport phenomena. We utilize rubrene single crystals as model systems. Due to the limited dimensions of crystals and the associated handling difficulty, the wrinkling instability is chosen as a metrology tool for the in-plane elastic constants. To elucidate the effects of mechanical strain on charge transport, we take advantage of wrinkling as a unique way to strain the conducting channel of field-effect transistors in a non-destructive, reversible, and predictable manner and demonstrate the mechanical modulation of field-effect mobility. Our contributions are the first to quantitatively correlate the crystal structure and the mechanical properties of OSCs, as well as the first to study their electro-mechanical behavior. They also represent a significant step forward in structure-function relationships in organic semiconductors and lay the foundation for the effective use of organic semiconductors in mechanically demanding applications such as pressure sensors and electronic skins.

  12. Bioinspired Reductionistic Peptide Engineering for Exceptional Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Avinash, M. B.; Raut, Devaraj; Mishra, Manish Kumar; Ramamurty, Upadrasta; Govindaraju, T.

    2015-11-01

    A simple solution-processing and self-assembly approach that exploits the synergistic interactions between multiple hydrogen bonded networks and aromatic interactions was utilized to synthesize molecular crystals of cyclic dipeptides (CDPs), whose molecular weights (~0.2 kDa) are nearly three orders of magnitude smaller than that of natural structural proteins (50-300 kDa). Mechanical properties of these materials, measured using the nanoindentation technique, indicate that the stiffness and strength are comparable and sometimes better than those of natural fibres. The measured mechanical responses were rationalized by recourse to the crystallographic structural analysis and intermolecular interactions in the self-assembled single crystals. With this work we highlight the significance of developing small molecule based bioinspired design strategies to emulate biomechanical properties. A particular advantage of the successfully demonstrated reductionistic strategy of the present work is its amenability for realistic industrial scale manufacturing of designer biomaterials with desired mechanical properties.

  13. 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.

  14. Bioinspired Reductionistic Peptide Engineering for Exceptional Mechanical Properties

    PubMed Central

    Avinash, M. B.; Raut, Devaraj; Mishra, Manish Kumar; Ramamurty, Upadrasta; Govindaraju, T.

    2015-01-01

    A simple solution-processing and self-assembly approach that exploits the synergistic interactions between multiple hydrogen bonded networks and aromatic interactions was utilized to synthesize molecular crystals of cyclic dipeptides (CDPs), whose molecular weights (~0.2 kDa) are nearly three orders of magnitude smaller than that of natural structural proteins (50–300 kDa). Mechanical properties of these materials, measured using the nanoindentation technique, indicate that the stiffness and strength are comparable and sometimes better than those of natural fibres. The measured mechanical responses were rationalized by recourse to the crystallographic structural analysis and intermolecular interactions in the self-assembled single crystals. With this work we highlight the significance of developing small molecule based bioinspired design strategies to emulate biomechanical properties. A particular advantage of the successfully demonstrated reductionistic strategy of the present work is its amenability for realistic industrial scale manufacturing of designer biomaterials with desired mechanical properties. PMID:26525957

  15. Build-in Electric Field Induced Mechanical Property Change

    NASA Astrophysics Data System (ADS)

    Chien, Te-Yu; Liu, Jian; Yost, Andrew J.; Chakhalian, Jacques; Freeland, John W.; Guisinger, Nathan P.

    Mechanical properties describe how materials respond to external stress. Microscopically, many intrinsic and extrinsic factors, such as bond length and strength (intrinsic) and grain boundaries (extrinsic), may affect the mechanical property of the materials. In this study, we observed a change of fracturing behavior of Nb-doped SrTiO3 in a Schottky barrier near the interfaces with metallic LaNiO3 films. Through cross-sectional scanning tunneling microscopy and spectroscopy (XSTM/S) experiments and theoretical analysis, the observed fractured topography could be explained by the change of the bond length caused alternation of mechanical property inside the Schottky barrier. Same model could also explain the widely observed dielectric dead layer for SrTiO3 in contact with metal electrodes.

  16. Bioinspired Reductionistic Peptide Engineering for Exceptional Mechanical Properties.

    PubMed

    Avinash, M B; Raut, Devaraj; Mishra, Manish Kumar; Ramamurty, Upadrasta; Govindaraju, T

    2015-11-03

    A simple solution-processing and self-assembly approach that exploits the synergistic interactions between multiple hydrogen bonded networks and aromatic interactions was utilized to synthesize molecular crystals of cyclic dipeptides (CDPs), whose molecular weights (~0.2 kDa) are nearly three orders of magnitude smaller than that of natural structural proteins (50-300 kDa). Mechanical properties of these materials, measured using the nanoindentation technique, indicate that the stiffness and strength are comparable and sometimes better than those of natural fibres. The measured mechanical responses were rationalized by recourse to the crystallographic structural analysis and intermolecular interactions in the self-assembled single crystals. With this work we highlight the significance of developing small molecule based bioinspired design strategies to emulate biomechanical properties. A particular advantage of the successfully demonstrated reductionistic strategy of the present work is its amenability for realistic industrial scale manufacturing of designer biomaterials with desired mechanical properties.

  17. Microstructure and mechanical properties of Al-1050 during incremental ECAP

    NASA Astrophysics Data System (ADS)

    Salamati, M.; Tamimi, S.; Moturu, S.; Sivaswamy, G.; Qarni, M.; Rosochowski, A.

    2017-05-01

    Incremental ECAP is a new method of ECAP process were the severe shear deformation is incrementally applied on the sample resulting in grain refining and new texture developing. The fundamental objective of the present work is an observation of effect of different passes of I-ECAP on microstructure and mechanical properties of AA1050 billet. To that end, 8 pass of I-ECAP have been carried out using Bc route and microstructure evolution and mechanical properties of the I-ECAPed samples have been studied. The EBSD and TEM analyses indicates that I-ECAP is as capable as conventional ECAP to grain refinements and a UFG structure is resulted after I-ECAP cycles. Tensile testing and hardness measurements indicates that mechanical properties of the Al-1050 billets increases dramatically by increasing the I-ECAP passes.

  18. 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.

  19. 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.

  20. 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.

  1. Does pH influence soil hydro-mechanical properties?

    NASA Astrophysics Data System (ADS)

    Chaplain, V.; Défossez, P.; Delarue, G.; Dexter, A. R.; Richard, G.; Tessier, D.

    2009-04-01

    Does pH influence soil hydro-mechanical properties ? V. Chaplain1, P. Défossez2, G. Delarue1, A.R. Dexter3, G. Richard3 and D. Tessier1. 1 UR INRA PESSAC RD 10, F-78026 Versailles cedex 2 UMR INRA/URCA FARE, 2 Esplanade Roland Garros, BP 224 F-51686 Reims cedex 2 3 UR INRA Sols 2163 Avenue de la Pomme de Pin - CS 40001 ARDON F-45075 Orléans Cedex 2 Corresponding author : chaplain@versailles.inra.fr Structure of soils and its dynamic, physico-chemistry of the interface are of a great importance in the fate of organic pollutants because it governs the accessibility of pollutants to micro-organisms. The soil structure of soils is related to physical parameters (texture, density, water content) but the physico-chemical properties of the interface is not considered. In this study we performed hydro-mechanical measurements on soil samples taken from the 42-plot long-term experiment in Versailles. Indeed six plots were selected to cover a large range of pH values from acid (3.5) to alkaline (8.2) due to the repeated application of fertilizers. Soils were taken in the 0-20 cm and in the 30-35 cm layer out of the ploughed zone. All soils had similar texture and composition with low organic carbon. Therefore pH changes the surface charges and hydrophobicity that are implied in aggregation process. The two layers had the same pH values. The precompression stress Pc and the compression index Cc were derived from confined compression tests performed on remoulded soil samples (density 1.45 g/cm3) at saturation. Results shows that the precompression stress increased at pH lower than 4. In acid case, precompression stress was higher in subsoil. This increase of Pc was attributed to the hydrophobicity due in part to the condensation of charges probably sensitive to the humectation/dessication processes.

  2. Relating secondary structure to the mechanical properties of polypeptide hydrogels

    NASA Astrophysics Data System (ADS)

    Hagan, Sharon Anne

    Biomimetic hydrogels are being developed for use in medicine as drug delivery devices and tissue engineering matrices, and the mechanical properties of the materials play an important role in their performance. For example, in tissue engineering, gene expression and cell adhesion have been closely linked to the mechanical properties of the surrounding hydrogel matrix. In poly-L-lysine hydrogels, a five-fold increase in storage modulus, a 50% increase in equilibrium modulus, and a 62% decrease in swelling degree are shown to occur as the hydrogel network chains transition from an alpha-helix to a beta-sheet conformation. The manipulation of the network's mechanical behavior through changes in the secondary structure of the polymer chains offers an additional design variable in the development of biosynthetic materials. Analogous to poly-L-lysine, elastin-mimetic proteins based on the consensus repeat sequence of elastin (VPGVG) undergo a temperature-dependent secondary structure transition from a random coil to a beta-spiral. In this research, chemically-crosslinked poly[(VPGVG)4(VPGKG)] hydrogels are shown to possess temperature- and pH-dependent swelling. Following scaling law predictions (G ˜ φ2n), the hydrogels have been shown to behave as ideal elastic networks when the crosslink density is varied at synthesis (theory: n = 9/4, experimental: n = 2.0 +/- 0.1), and behave as flexible networks above and below their structural transition temperature of 35°C (theory: n = 1/3, experimental: n = 0.45 +/- 0.06). Evaluation of published data on elastin-mimetic hydrogels shows that the hydrogels behave as ideal elastic networks for all crosslinking techniques, crosslink spacings, and crosslink functionalities reported. As a contrast to chemically-crosslinked hydrogels, a novel elastin-mimetic triblock (EMT) copolymer was evaluated because of its potential use in cell encapsulation without potentially harmful side reactions. Unlike other thermally gelling copolymers

  3. Coating Microstructure-Property-Performance Issues

    SciTech Connect

    Terry C. Totemeier; Richard N. Wright

    2005-05-01

    Results of studies on the relationships between spray parameters and performance of thermally-sprayed intermetallic coatings for high-temperature oxidation and corrosion resistance are presented. Coating performance is being assessed by corrosion testing of free-standing coatings, thermal cycling of coating substrates, and coating ductility measurement. Coating corrosion resistance was measured in a simulated coal combustion gas environment (N2-CO-CO2-H2O-H2S) at temperatures from 500 to 800°C using thermo-gravimetric analysis (TGA). TGA testing was also performed on a typical ferritic-martensitic steel, austenitic stainless steel, and a wrought Fe3Al-based alloy for direct comparison to coating behavior. FeAl and Fe3Al coatings showed corrosion rates slightly greater than that of wrought Fe3Al, but markedly lower than the steels at all temperatures. The corrosion rates of the coatings were relatively independent of temperature. Thermal cycling was performed on coated 316SS and nickel alloy 600 substrates from room temperature to 800°C to assess the relative effects of coating microstructure, residual stress, and thermal expansion mismatch on coating cracking by thermal fatigue. Measurement of coating ductility was made by acoustic emission monitoring of coated 316SS tensile specimens during loading.

  4. 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.

  5. Mechanical Properties of Lower Limb Tendons and Ligaments in Primates.

    DTIC Science & Technology

    1982-07-01

    AD-Ri28 797 MECHANICAL PROPERTIES OF LOWER LIMB TENDONS AND i/i LIGAMENTS IN PRIMATES(U) MICHIGAN STATE UNIV EAST LANSING DEPT OF BIOMECHAlNICS D J...filottifj by &task ember) Lower Limb Tendons and Ligaments Hysteresis Chimpanzee 316io"chanical. Response Relaxation 1bratory Loads Miechanical Stress...tweoey an Idwoth, by Week Member) Ibis report covers a study of the material property characteristics of four ligaments and tendons from the lover limbs

  6. Development of data base with mechanical properties of un- and pre-irradiated VVER cladding

    SciTech Connect

    Asmolov, V.; Yegorova, L.; Kaplar, E.; Lioutov, K.; Smirnov, V.; Prokhorov, V.; Goryachev, A.

    1998-03-01

    Analysis of recent RIA test with PWR and VVER high burnup fuel, performed at CABRI, NSRR, IGR reactors has shown that the data base with mechanical properties of the preirradiated cladding is necessary to interpret the obtained results. During 1997 the corresponding cycle of investigations for VVER clad material was performed by specialists of NSI RRC KI and RIAR in cooperation with NRC (USA), IPSN (France) in two directions: measurements of mechanical properties of Zr-1%Nb preirradiated cladding versus temperature and strain rate; measurements of failure parameters for gas pressurized cladding tubes. Preliminary results of these investigations are presented in this paper.

  7. Impact and dynamic mechanical thermal properties of textile silk reinforced epoxy resin composites

    NASA Astrophysics Data System (ADS)

    Yang, K.; Guan, J.

    2016-07-01

    Silk fabric reinforced epoxy resin composites (SFRPs) were prepared using simple techniques of hand lay-up, hot-press and vacuum treatment, and a series of volume fractions of silk reinforcements were achieved. The impact properties and dynamic mechanical properties of SFRPs were investigated using a pendulum impact testing method and dynamic mechanical thermal analysis (DMTA). The results suggest that silk reinforcement could greatly enhance the mechanical performances of SFRPs. The impact strength reached a maximum of 71 kJ/m2 for 60%-silk SFRP, which demonstrated a potential of silk composites for defence and impact- resistant materials.

  8. Selective laser melting of titanium alloy: investigation of mechanical properties and microstructure

    NASA Astrophysics Data System (ADS)

    Agapovichev, A. V.; Kokareva, V. V.; Smelov, V. G.; Sotov, A. V.

    2016-11-01

    This article presents the mechanical properties and microstructure of titanium alloy after selective laser melting (SLM). Titanium alloys are ideal material for selective laser melting (SLM), because they are expensive and difficult to machinery using traditional technologies. The application of SLM in the biomedical area has been slow due to the stringent performance criteria and concerns related to personification and part quality. In this article we focused on the manufacture by SLM and determination of microstructure and mechanical properties of titanium alloy (Ti Grade 2 Powder) using tensile tests and X-ray diffraction. The results reveal that the alloy exhibits a pronounced the homogeneous microstructure and high mechanical strength.

  9. Investigation of properties and performance of ceramic composite components. Final report on Phase 2

    SciTech Connect

    Curtin, W.A.; Reifsnider, K.L.; Oleksuk, L.L.S.; Stinchcomb, W.W.

    1994-10-31

    The purpose of Phase 2 of the Investigation of Properties and Performance of Ceramic Composite Components has been to build on and extend the work completed during Phase 1 to further advance the transition from properties of ceramic composite materials to performance of ceramic composite components used in fossil energy environments. The specific tasks of Phase 2 were: (1) develop and validate reliable and accurate high temperature, biaxial mechanical tests methods for structural ceramic composite components; (2) test and evaluate ceramic composite components, specifically tubes; (3) characterize long-term, mechanical performance of ceramic composite tubes at high temperatures; (4) develop a fundamental understanding of the mechanical degradation and performance limitations of ceramic composite components under service conditions; (5) develop predictive models for damage tolerance and reliability; and (6) relate component performance to microstructure and, thereby, provide feedback to the associated process-development effort, to improve performance. Accomplishments for each task are given.

  10. Transient dynamic mechanical properties of resilin-based elastomeric hydrogels

    PubMed Central

    Li, Linqing; Kiick, Kristi L.

    2014-01-01

    The outstanding high-frequency properties of emerging resilin-like polypeptides (RLPs) have motivated their development for vocal fold tissue regeneration and other applications. Recombinant RLP hydrogels show efficient gelation, tunable mechanical properties, and display excellent extensibility, but little has been reported about their transient mechanical properties. In this manuscript, we describe the transient mechanical behavior of new RLP hydrogels investigated via both sinusoidal oscillatory shear deformation and uniaxial tensile testing. Oscillatory stress relaxation and creep experiments confirm that RLP-based hydrogels display significantly reduced stress relaxation and improved strain recovery compared to PEG-based control hydrogels. Uniaxial tensile testing confirms the negligible hysteresis, reversible elasticity and superior resilience (up to 98%) of hydrated RLP hydrogels, with Young's modulus values that compare favorably with those previously reported for resilin and that mimic the tensile properties of the vocal fold ligament at low strain (<15%). These studies expand our understanding of the properties of these RLP materials under a variety of conditions, and confirm the unique applicability, for mechanically demanding tissue engineering applications, of a range of RLP hydrogels. PMID:24809044

  11. 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.

  12. Membrane mechanical properties of synthetic asymmetric phospholipid vesicles.

    PubMed

    Lu, Li; Doak, William J; Schertzer, Jeffrey W; Chiarot, Paul R

    2016-09-13

    Synthetic lipid vesicles have served as important model systems to study cellular membrane biology. Research has shown that the mechanical properties of bilayer membranes significantly affects their biological behavior. The properties of a lipid bilayer are governed by lipid acyl chain length, headgroup type, and the presence of membrane proteins. However, few studies have explored how membrane architecture, in particular trans-bilayer lipid asymmetry, influences membrane mechanical properties. In this study, we investigated the effects of lipid bilayer architecture (i.e. asymmetry) on the mechanical properties of biological membranes. This was achieved using a customized micropipette aspiration system and a novel microfluidic technique previously developed by our team for building asymmetric phospholipid vesicles with tailored bilayer architecture. We found that the bending modulus and area expansion modulus of the synthetic asymmetric bilayers were up to 50% larger than the values acquired for symmetric bilayers. This was caused by the dissimilar lipid distribution in each leaflet of the bilayer for the asymmetric membrane. To the best of our knowledge, this is the first report on the impact of trans-bilayer asymmetry on the area expansion modulus of synthetic bilayer membranes. Since the mechanical properties of bilayer membranes play an important role in numerous cellular processes, these results have significant implications for membrane biology studies.

  13. 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.

  14. Mechanical Properties and Fractography of Electroslag Remelted 300M Steel.

    DTIC Science & Technology

    1983-03-01

    the minimum requirements. Charpy impact energy values shown in Table 3 varied from a high of 22 ft-lb for the L-T orientation to 9 ft-lb for the S-L...specimen orientations are shown in Figures la and lb. 3 ’ab 4. MECHANICAL PROPERTIES OF 300M AND 4340 STEELS Impact emp. Orien- i.?% Y.S. U.T.S. Eon...AMMRC TR 83-13 IAD II MECHANICAL PROPERTIES AND FRACTOGRAPHY OF ELECTROSLAG REMELTED 300M STEEL 0 f ALBERT A. ANCTIL METALS RESEARCH DIVISION March

  15. Mechanical Properties and Durability of CNT Cement Composites

    PubMed Central

    Camacho, María del Carmen; Galao, Oscar; Baeza, Francisco Javier; Zornoza, Emilio; Garcés, Pedro

    2014-01-01

    In the present paper, changes in mechanical properties of Portland cement-based mortars due to the addition of carbon nanotubes (CNT) and corrosion of embedded steel rebars in CNT cement pastes are reported. Bending strength, compression strength, porosity and density of mortars were determined and related to the CNT dosages. CNT cement paste specimens were exposed to carbonation and chloride attacks, and results on steel corrosion rate tests were related to CNT dosages. The increase in CNT content implies no significant variations of mechanical properties but higher steel corrosion intensities were observed. PMID:28788536

  16. Elastic properties of graphene obtained by computational mechanical tests

    NASA Astrophysics Data System (ADS)

    Hartmann, Markus A.; Todt, Melanie; Rammerstorfer, Franz G.; Fischer, Franz D.; Paris, Oskar

    2013-09-01

    The basic building block of many carbon nanostructures like fullerenes, carbon onions or nanotubes is the truly two-dimensional material graphene. Commercial finite element codes, widely used to predict the mechanical properties of these structures, rely on the knowledge of the mechanical properties of the basic material. In this paper using an atomistic simulation approach we determine the membrane and bending stiffness of graphene, as well as the corresponding effective parameters: the effective elastic modulus E=2.4\\ \\text{TPa} , Poisson ratio \

  17. Physical and mechanical properties of Tunisian women hair.

    PubMed

    Sayahi, E; Harizi, T; Msahli, S; Sakli, F

    2016-10-01

    Mechanical analysis of human hair may provide the dermatologists with several markers of considerable diagnostic importance. The aim of this study was to analyse the physical and mechanical properties of Tunisian women's hair. Surface characteristics were determined with scanning electron microscopy (SEM). Mechanical properties were studied using the Miniature Tensile Tester Model 675 (MTT675), and the Fibre Dimensional Analysis Unit Model 765 (FDAS765) of Dia-Stron, UK, was used to measure the cross-sectional area. The cross-sectional area, stress at break, strain at break, elastic modulus and total work were 4643.21 ± 817 μm(2) , 201 ± 11.26 MPa, 47.3 ± 3.6%, 3.1 ± 0.16 GPa, and 9 ± 2.2 mJ, respectively. The effects of the factors 'hair curliness' and 'age' on the physical and mechanical properties were studied. The cross-sectional area and the break load are influenced by the factors 'age' and 'curl type', whereas Young's modulus shows a significant dependency only on the age. Tunisian women hair presented good mechanical properties as shown by a greater breaking stress and higher breaking strain. Both curl type and age are important factors to consider when evaluating the behaviour of hair. © 2016 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  18. 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.

  19. Effect of sodium hypochlorite on dentine mechanical properties. A review.

    PubMed

    Pascon, Fernanda Miori; Kantovitz, Kamila Rosamilia; Sacramento, Patrícia Almada; Nobre-dos-Santos, Marinês; Puppin-Rontani, Regina Maria

    2009-12-01

    The aim of this study was to carry out a review on the effect of sodium hypochlorite (NaOCl) on the mechanical properties of root dentine. The authors searched the Cochrane Library, Embase, PubMed and the Web of Science for papers published from 1984 to 2008. The main search terms used were: dentine, root canal dentine, sodium hypochlorite, mechanical analysis, elastic modulus, hardness, roughness, flexural strength, compressive strength. The inclusion criteria were studies that evaluated the effect of NaOCl solution, used as an irrigant in endodontics, on the mechanical properties of root dentine. Those studies that were considered to be unrelated to the question addressed, that had investigated NaOCl as a deproteinizing agent, had not evaluated the effect of NaOCl on the mechanical properties of dentine, and that indirectly verified the effect of NaOCl on endodontically treated teeth were excluded. The selected papers were assigned to a score (A-C), according to predetermined criteria. A total of 16 papers were selected, and nine papers were included in the critical appraisal. Five papers were classified as grade A, 4 as grade B, and no paper was classified as grade C. Based on this review, the authors suggest that there is strong evidence showing that sodium hypochlorite adversely alters the mechanical properties of root dentine, when used as an endodontic irrigant.

  20. Characterization of High Temperature Mechanical Properties Using Laser Ultrasound

    SciTech Connect

    David Hurley; Stephen Reese; Farhad Farzbod; Rory Kennedy

    2012-05-01

    Mechanical properties are controlled to a large degree by defect structures such as dislocations and grain boundaries. These microstructural features involve a perturbation of the perfect crystal lattice (i.e. strain fields). Viewed in this context, high frequency strain waves (i.e. ultrasound) provide a natural choice to study microstructure mediated mechanical properties. In this presentation we use laser ultrasound to probe mechanical properties of materials. This approach utilizes lasers to excite and detect ultrasonic waves, and as a consequence has unique advantages over other methods—it is noncontacting, requires no couplant or invasive sample preparation (other than that used in metallurgical analysis), and has the demonstrated capability to probe microstructure on a micron scale. Laser techniques are highly reproducible enabling sophisticated, microstructurally informed data analysis. Since light is being used for generation and detection of the ultrasonic wave, the specimen being examined is not mechanically coupled to the transducer. As a result, laser ultrasound can be carried out remotely, an especially attractive characteristic for in situ measurements in severe environments. Several examples involving laser ultrasound to measure mechanical properties in high temperature environments will be presented. Emphasis will be place on understanding the role of grain microstructure.

  1. Influence of Moisture on Mechanical Properties of Cellulose Insulation Paper

    NASA Astrophysics Data System (ADS)

    Wang, Y. Y.; Tian, M.; Xu, H. X.; Fan, P.

    2014-01-01

    This paper aims to investigate the impact of moisture on mechanical properties of insulation paper. According to the molecular modeling approach proposed by Theodorou, the amorphous cellulose models of insulation paper with different moisture contents were built up to calculate mechanical parameters and hydrogen bond networks. And relevant conclusions could be drawn through further analysis on these calculation results: water molecules can destroy hydrogen bond network between the neighboring cellulose molecules, which might be responsible for the significant decrease of Young's modulus and other mechanical parameters, while no appreciable effect of intramolecular hydrogen bonds on mechanical properties was detected. Thus tensile tests were also carried out to study the moisture influence on the Young's modulus, by which the result of the simulation was approved.

  2. Mechanical and Electrical Properties of Cryo-worked Cu

    NASA Astrophysics Data System (ADS)

    Bettinali, Livio; Tosti, Silvano; Pizzuto, Aldo

    2014-01-01

    For manufacturing the magnets of fusion machines pure copper of both high mechanical resistance and electrical conductivity is required. Though high purity copper guarantees high electrical conductivity, its mechanical properties may be not suitable for the applications in tokamaks. In this view, a new procedure developed for obtaining high purity copper with excellent mechanical strength is described in this work. Samples of oxygen free copper (OFC) have been worked by pressing in liquid nitrogen (77 K). It has been verified that the mechanical properties of the worked metal are strongly dependent on the strain rate. Very low strain rates permitted to attain values of tensile yield strength (550 MPa) significantly higher than those obtained by traditional cold-working at room temperature (450 MPa). The electrical conductivity of the cryo-worked Cu decreases with the tensile yield strength even though the hardest samples of tensile yield strength of 550 MPa exhibit still acceptable values of conductivity (about 94 % IACS at room temperature).

  3. Surface Effects on the Mechanical Properties of Si-nanorods

    NASA Astrophysics Data System (ADS)

    Wu, Shi-Yu; Liu, Shudun; Jayanthi, C. S.; Zhang, Zhenyu

    2000-03-01

    Mechanical properties of Si-nanorods of various sizes are studied using an order(N) non-orthogonal tight-binding molecular dynamics [1]. As the size of the nanorod decreases, we find an evolution in the surface reconstruction pattern and change in the structural and elastic properties. In particular, we examine how the surface effects modify and eventually lead to the break down of the scaling behavior of the elastic properties of Si-nanorods. [1] C.S. Jayanthi, S.Y. Wu, J. Cocks, N.S. Luo, Z.L. Xie, M. Menon and G. Yang, Phys. Rev. B57, 3799(1998).

  4. Mechanical properties of sorbents depending on nanopore sizes

    NASA Astrophysics Data System (ADS)

    Kolesnikova, A. S.

    2017-07-01

    The effect of the nanopore size on the mechanical properties of a porous carbon material with the density of 1.4 g/cm3 is discussed. The atomistic models of porous carbon materials depending on the nanopore size are constructed. The numerical experiments are implemented with using the molecular mechanical method based on the Brenner potential. The Young's moduli are evaluated for porous carbon structures at certain nanopore dimensions and are found to decrease with the enlarging nanopores.

  5. Microstructure and mechanical properties of SPD processed nanocrystalline tantalum

    NASA Astrophysics Data System (ADS)

    Li, Gang

    In this study, the refractory metal, Tantalum (Ta), having a Body Centered Cubic (BCC) structure is selected as a model material. Bulk nanocrystalline Ta (NC-Ta) is used to study the process-microstructure-property relationship for a nano-structured BCC metal. For the first time, high pressure torsion (HPT) technique was applied to produce NC-Ta. Microstructural features of HPT NC-Ta were characterized by X-ray Diffraction (XRD) and Transmission Electron Microcopy (TEM). The resulting microstructures show nano-size grains (grain size smaller than 100 nm) together with high angle grain boundaries. The grain size was estimated to be around 35 nm based on the broadening of the (110) peak of XRD, while a few tens of nanometers based on TEM observation. A high density of atomic steps and ledges were observed along the grain boundaries while a large population of edge dislocations within the grains by high resolution TEM. It shows the non-equilibrium and high-energy nature of the grain boundaries. The mechanical properties of HPT NC-Ta were investigated using instrumented nanoindentation and micro-compression techniques, respectively. Instrumented nanoindentation intends to study the uniformity of the distribution of mechanical properties, the strain rate effect, and the thermally activated processes associated with plastic deformation. The results show that the elastic modulus of HPT NC-Ta is considerably reduced compared to the coarse-grain counterparts. The results are explained based on the hypothesis that in the HPT NC-Ta greatly increased populations of grain boundaries (GBs) and triple junctions (TJs) have been induced along with a high concentration of lattice vacancies in the severely deformed metal. The microhardness measurement shows a peak across the radial direction. It is believed this indicates an inverse Hall-Petch effect. Also, the nanoindentation hardness measurement, independent of the indentation depth, indicates the absence of indentation size effect

  6. Quadriceps Muscle Mechanical Simulator for Training of Vastus Medialis Obliquus and Vastus Lateralis Obliquus Mechanical Properties

    PubMed Central

    Irmak, Rafet; Irmak, Ahsen; Biçer, Gökhan

    2014-01-01

    Objectives: In classical anatomy quadriceps muscle has four heads. Clinical studies have demostrated 6 heads of this muscle. These heads were demostrated seperately not only by their functional properties,but also by innervation and kinesiological properties. In our previous study we have developed and demostrated electrophysiological properties of vastus medialis obliquus by an electronic patient simulator. The purpose of this study is to develop a mechanical simulator which can be used to demostrate mechanical properties of 6 heads of quadriceps muscle and the screw home mechanism. Methods: Quadriceps femoris muscle has 6 heads: rectus femoris, vastus intermedius, vastus medialis obliquus, vastus medialis longus, vastus lateralis obliquus and vastus lateralis longus. The fundamental mechanical properties of each head is seperated by insersio and angle of pull. Main design principle was to demostrate all heads with insersio and angle of pull properties. Second design principle was to demostrate the screw-home mechanism which is the result of difference in articular surfaces of medial and lateral of condyles of femur. Results: Final design of the simulator consists of three planes for demostration of angle of pull and pulling forces (patellar plane, proximal and distal planes) of each heads. On each plane channels were graved as origo and insersio for demostration of angle of pull. Distal plane was movable for demostration of pulling forces in different angels of knee flexion and extention. Also proximal plane was adjustable to demostrate different sitting and standing positions. Srew home mechanism was demostrated by specially designed hingle mechanism. Left and right side hingle mechanisms have different radii as femoral condyles and this difference can cause rotation in terminal extension as in the screw home mechanism. Conclusion: Vastus medialis obliquus, vastus lateralis obliquus and screw-home mechanism have clinical significance. We were not able to find

  7. Modified Gellan Gum hydrogels with tunable physical and mechanical properties

    PubMed Central

    Coutinho, Daniela F.; Sant, Shilpa; Shin, Hyeongho; Oliveira, João T.; Gomes, Manuela E.; Neves, Nuno M.; Khademhosseini, Ali; Reis, Rui L.

    2010-01-01

    Gellan Gum (GG) has been recently proposed for tissue engineering applications. GG hydrogels are produced by physical crosslinking methods induced by temperature variation or by the presence of divalent cations. However, physical crosslinking methods may yield hydrogels that become weaker in physiological conditions due to the exchange of divalent cations by monovalent ones. Hence, this work presents a new class of GG hydrogels crosslinkable by both physical and chemical mechanisms. Methacrylate groups were incorporated in the GG chain, leading to the production of a methacrylated gellan gum (MeGG) hydrogel with highly tunable physical and mechanical properties. The chemical modification was confirmed by proton nuclear magnetic resonance (1H-NMR) and Fourier transform infrared spectroscopy (FTIR-ATR). The mechanical properties of the developed hydrogel networks, with Young’s modulus values between 0.15 and 148 kPa, showed to be tuned by the different crosslinking mechanisms used. The in vitro swelling kinetics and hydrolytic degradation rate was dependent on the crosslinking mechanisms used to form the hydrogels. Three-dimensional (3D) encapsulation of NIH-3T3 fibroblast cells in MeGG networks demonstrated in vitro biocompatibility confirmed by high cell survival. Given the highly tunable mechanical and degradation properties of MeGG, it may be applicable for a wide range of tissue engineering approaches. PMID:20663552

  8. Designed biomaterials to mimic the mechanical properties of muscles.

    PubMed

    Lv, Shanshan; Dudek, Daniel M; Cao, Yi; Balamurali, M M; Gosline, John; Li, Hongbin

    2010-05-06

    The passive elasticity of muscle is largely governed by the I-band part of the giant muscle protein titin, a complex molecular spring composed of a series of individually folded immunoglobulin-like domains as well as largely unstructured unique sequences. These mechanical elements have distinct mechanical properties, and when combined, they provide the desired passive elastic properties of muscle, which are a unique combination of strength, extensibility and resilience. Single-molecule atomic force microscopy (AFM) studies demonstrated that the macroscopic behaviour of titin in intact myofibrils can be reconstituted by combining the mechanical properties of these mechanical elements measured at the single-molecule level. Here we report artificial elastomeric proteins that mimic the molecular architecture of titin through the combination of well-characterized protein domains GB1 and resilin. We show that these artificial elastomeric proteins can be photochemically crosslinked and cast into solid biomaterials. These biomaterials behave as rubber-like materials showing high resilience at low strain and as shock-absorber-like materials at high strain by effectively dissipating energy. These properties are comparable to the passive elastic properties of muscles within the physiological range of sarcomere length and so these materials represent a new muscle-mimetic biomaterial. The mechanical properties of these biomaterials can be fine-tuned by adjusting the composition of the elastomeric proteins, providing the opportunity to develop biomaterials that are mimetic of different types of muscles. We anticipate that these biomaterials will find applications in tissue engineering as scaffold and matrix for artificial muscles.

  9. Characterization of mechanical and biochemical properties of developing embryonic tendon

    PubMed Central

    Marturano, Joseph E.; Arena, Jeffrey D.; Schiller, Zachary A.; Georgakoudi, Irene; Kuo, Catherine K.

    2013-01-01

    Tendons have uniquely high tensile strength, critical to their function to transfer force from muscle to bone. When injured, their innate healing response results in aberrant matrix organization and functional properties. Efforts to regenerate tendon are challenged by limited understanding of its normal development. Consequently, there are few known markers to assess tendon formation and parameters to design tissue engineering scaffolds. We profiled mechanical and biological properties of embryonic tendon and demonstrated functional properties of developing tendon are not wholly reflected by protein expression and tissue morphology. Using force volume-atomic force microscopy, we found that nano- and microscale tendon elastic moduli increase nonlinearly and become increasingly spatially heterogeneous during embryonic development. When we analyzed potential biochemical contributors to modulus, we found statistically significant but weak correlation between elastic modulus and collagen content, and no correlation with DNA or glycosaminoglycan content, indicating there are additional contributors to mechanical properties. To investigate collagen cross-linking as a potential contributor, we inhibited lysyl oxidase-mediated collagen cross-linking, which significantly reduced tendon elastic modulus without affecting collagen morphology or DNA, glycosaminoglycan, and collagen content. This suggests that lysyl oxidase-mediated cross-linking plays a significant role in the development of embryonic tendon functional properties and demonstrates that changes in cross-links alter mechanical properties without affecting matrix content and organization. Taken together, these data demonstrate the importance of functional markers to assess tendon development and provide a profile of tenogenic mechanical properties that may be implemented in tissue engineering scaffold design to mechanoregulate new tendon regeneration. PMID:23576745

  10. Characterization of mechanical and biochemical properties of developing embryonic tendon.

    PubMed

    Marturano, Joseph E; Arena, Jeffrey D; Schiller, Zachary A; Georgakoudi, Irene; Kuo, Catherine K

    2013-04-16

    Tendons have uniquely high tensile strength, critical to their function to transfer force from muscle to bone. When injured, their innate healing response results in aberrant matrix organization and functional properties. Efforts to regenerate tendon are challenged by limited understanding of its normal development. Consequently, there are few known markers to assess tendon formation and parameters to design tissue engineering scaffolds. We profiled mechanical and biological properties of embryonic tendon and demonstrated functional properties of developing tendon are not wholly reflected by protein expression and tissue morphology. Using force volume-atomic force microscopy, we found that nano- and microscale tendon elastic moduli increase nonlinearly and become increasingly spatially heterogeneous during embryonic development. When we analyzed potential biochemical contributors to modulus, we found statistically significant but weak correlation between elastic modulus and collagen content, and no correlation with DNA or glycosaminoglycan content, indicating there are additional contributors to mechanical properties. To investigate collagen cross-linking as a potential contributor, we inhibited lysyl oxidase-mediated collagen cross-linking, which significantly reduced tendon elastic modulus without affecting collagen morphology or DNA, glycosaminoglycan, and collagen content. This suggests that lysyl oxidase-mediated cross-linking plays a significant role in the development of embryonic tendon functional properties and demonstrates that changes in cross-links alter mechanical properties without affecting matrix content and organization. Taken together, these data demonstrate the importance of functional markers to assess tendon development and provide a profile of tenogenic mechanical properties that may be implemented in tissue engineering scaffold design to mechanoregulate new tendon regeneration.

  11. Mechanical properties of cast Ti-Hf alloys.

    PubMed

    Sato, Hideki; Kikuchi, Masafumi; Komatsu, Masashi; Okuno, Osamu; Okabe, Toru

    2005-02-15

    This study examined the mechanical properties of a series of Ti-Hf alloys. Titanium alloys with 10 to 40 mass % Hf were made with titanium and hafnium sponge in an argon-arc melting furnace. Specimens cast into magnesia-based investment molds were tested for yield strength, tensile strength, percentage elongation, and modulus of elasticity. Vickers microhardness was determined at 25 to 600 microm from the cast surface. X-ray diffractometry was also performed. Commercially pure Ti (CP Ti) and pure Ti prepared from titanium sponge were used as controls. The data (n = 5) were analyzed with a one-way ANOVA and the Student-Newman-Keuls test (alpha = 0.05). The diffraction peaks of all the metals matched those for alpha Ti; no beta phase peaks were found. Alloys with Hf > or = 25% had significantly (p < 0.05) higher yield and tensile strength compared to the CP Ti and pure Ti. There were no significant differences (p > 0.05) in elongation among all the Ti-Hf alloys and CP Ti, whereas the elongation of alloys with Hf > or = 30% was significantly (p < 0.05) lower than that of the pure Ti. The cast Ti-Hf alloys tested can be considered viable alternatives to CP Ti because they were stronger than CP Ti and had similar elongation.

  12. Mechanical Properties of Composite Material Using Coal Ash and Clay

    NASA Astrophysics Data System (ADS)

    Fukumoto, Isao; Kanda, Yasuyuki

    Coal ash is industry waste exhausted lots of amount by electric power plant. The particle sizes of coal ash, especially coal fly ash are very fine, and the chemical component are extremely resemble with Okinawa-Kucha clay. From the point of view that clay is composed of particles of micro meter size in diameter, we should try the application for fabrication of composite material using coal fly ash and clay. The comparison of the mechanical properties of composite material using coal fly ash and clay were performed during electric furnace burning and spark plasma sintering. As a result, the bending strength of composite material containing the coal ash 10% and fired at 1423K using the electric furnace after press forming at 30 MPa showed the highest value of 47 MPa. This phenomenon suggests a reinforcement role of coal ash particles to clay base material. In spark plasma sintering process, the bending strength of the composite material containing the clay 5-10% to fly ash base material fired at 1473K and pressured at 20 MPa showed the highest value of 88 MPa. This result indicates a binder effect of clay according to the liquid phase sintering of melted clay surrounding around coal fly ash particles surface.

  13. Mechanical properties of biodegradable soy-protein plastics

    SciTech Connect

    Schilling, C.H.; Babcock, T.; Wang, S.; Jane, J.

    1995-09-01

    Experiments were performed to evaluate the room-temperature mechanical properties of soy-protein plastics that were compression-molded with varying concentrations of glycerin plasticizer. Specimens exhibited stiff and brittle behavior with good tensile strength reliability based on Weibull statistics analysis. Raising the glycerin concentration from 0 to 20% progressively increased the tensile strain-to-failure from 1.1 to 1.8% and reduced the tensile strength from 42.1 to 23.6 MPa, the tangent modulus from 4.56 to 1.79 GPa, and the Rockwell hardness from R118.4 to R75.7. Ultrasonic measurements indicated that raising the glycerin concentration from 0 to 20% increased Poisson`s ratio from 0.348 to 0.409 and reduced Young`s Modulus from 7.01 to 5.4 GPa and the shear modulus from 2.5 to 1.8 GPa. Significant increases in the tensile strength and the strength reliability resulted from eliminating Griffith`s flaws by sieving the press powder before compression molding. Rockwell hardness rapidly decreased upon immersing these plastics in water at 25 {degree}C, an effect which was pronounced for the glycerin-containing specimens.

  14. Synthetic melanin films: Assembling mechanisms, scaling behavior, and structural properties

    NASA Astrophysics Data System (ADS)

    Lorite, Gabriela S.; Coluci, Vitor R.; da Silva, Maria Ivonete N.; Dezidério, Shirlei N.; Graeff, Carlos Frederico O.; Galva~O, Douglas S.; Cotta, Mônica A.

    2006-06-01

    In this work we report on the surface characterization of melanin thin films prepared using both water-based and organic solvent-based melanin syntheses. Atomic force microscopy (AFM) analysis of these films suggests that the organic solvent synthesis provides relatively planar basic melanin structures; these basic structures generate surface steps with height in the range of 2-3 nm and small tendency to form larger aggregates. The scaling properties obtained from the AFM data were used to infer the assembling mechanisms of these thin films which depend on the solvent used for melanin synthesis. The behavior observed in organic solvent-based melanin suggests a diffusion-limited aggregation process. Thus films with good adhesion to the substrate and smoother morphologies than water-prepared melanin films are obtained. Electronic structure calculations using a conductorlike screening model were also performed in order to elucidate the microscopic processes of thin film formation. Our results suggest that the agglomerates observed in hydrated samples originate from reaction with water at specific locations on the surface most likely defects on the planar structure.

  15. Mechanical Properties of Aluminum Tailor Welded Blanks at Superplastic Temperatures

    SciTech Connect

    Davies, Richard W.; Vetrano, John S.; Smith, Mark T.; Pitman, Stan G.

    2002-10-06

    This paper describes an investigation of the mechanical properties of weld material in aluminum tailor welded blanks (TWB) at superplastic temperatures and discusses the potential application of TWBs in superplastic forming operations. Aluminum TWBs consist of multiple sheet materials of different thickness or alloy that are butt-welded together into a single, variable thickness blank. To evaluate the performance of the weld material in TWBs, a series of tensile tests were conducted at superplastic temperatures with specimens that contained weld material in the gage area. The sheet material used in the study was Sky 5083 aluminum alloy, which was joined to produce the TWBs by gas tungsten arc welding using an AA5356 filler wire. The experimental results show that, in the temperature range of 500?C to 550?C and at strain rates ranging from 10-4 sec-1 to 10-2 sec-1, the weld material has a higher flow stress and lower ductility than the monolithic sheet material. The weld material exhibited elongations of 40% to 60% under these conditions, whereas the monolithic sheet achieved 220% to 360% elongation. At the same temperatures and strain rates, the weld material exhibited flow stresses 1.3 to 4 times greater than the flow stress in the monolithic sheet. However, the weld material did show a substantial increase in the strain rate sensitivity and ductility when compared to the same material formed at room temperature.

  16. Probing the mechanical properties of dental porcelain through nanoindentation

    NASA Astrophysics Data System (ADS)

    Manda, Marianthi; Moschakis, Nikolaos; Konstantinidis, Avraam; Christophilos, Demetrios; Papadopoulou, Lambrini; Koidis, Petros; Aifantis, Elias

    2012-11-01

    The purpose of this short communication is to report on some micro/nanoscale aspects of the mechanical behavior of dental porcelain. Specimens were characterized by micro-Raman spectroscopy and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). Massive nanoindentation experiments on the surface of the specimens were performed, and typical load-displacement or load-depth (P-h) curves were obtained, which in turn were used to determine the Young modulus (E) and nanoindentation hardness (n-H), based on the Oliver-Pharr method [1]. Statistical analyses were carried out to determine the Spearman’s rank correlation coefficient (Spearman’s ρ), along with non-parametric linear regression analysis by employing Kolmogorov-Smirnov and Two-Step Cluster tests. Densification due to grain boundary diffusion and open-pore elimination was revealed by SEM. EDS analysis indicated a leucite-dispersed silicate glass matrix, as well as its contamination by traces of other minerals. Raman spectroscopy supported the EDS assignments. The P-h curves suggested that inelastic deformation and material flow increases at larger depths. Spearman’s ρ value showed strong dependence of E and n-H on h, indicating the occurrence of a size effect. The logarithmic data of E and n-H as functions of h were fitted by using linear regression analysis. The data did not obey a normal distribution (as the Kolmogorov-Smirnov test showed) due to the chemical heterogeneity involved. The Two-Step Cluster analysis indicated clustering in four groups associated with the chemical heterogeneity of the surface. Similar works using nanoindentation to determine the mechanical properties of dental materials can be found, for example, in [2, 3]. Corresponding methods for extracting the values of E and n-H from P-h experimental curves can be found, for example, in [4-6].

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

    NASA Astrophysics Data System (ADS)

    Hajilar, Shahin; Shafei, Behrouz

    2016-12-01

    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 mechanical 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.

  18. Modeling the Mechanical Performance of Die Casting Dies

    SciTech Connect

    R. Allen Miller

    2004-02-27

    The following report covers work performed at Ohio State on modeling the mechanical performance of dies. The focus of the project was development and particularly verification of finite element techniques used to model and predict displacements and stresses in die casting dies. The work entails a major case study performed with and industrial partner on a production die and laboratory experiments performed at Ohio State.

  19. Relationship of the optical absorption and scattering properties with mechanical and structural properties of apple tissue

    USDA-ARS?s Scientific Manuscript database

    Optical absorption and scattering properties of fruit change with the physiological and biochemical activities in the tissue during ripening and postharvest storage. But it has not been well understood on how these changes are related to the structural and mechanical properties of fruit. This resear...

  20. The structure and mechanical properties of dragonfly wings and their role on flyability

    NASA Astrophysics Data System (ADS)

    Sun, Jiyu; Bhushan, Bharat

    2012-01-01

    Dragonfly wings possess great stability and high load-bearing capacity during flapping flight, glide, and hover. Scientists have been intrigued by them and have carried out research for biomimetic applications. Relative to the large number of works on its flight aerodynamics, few researchers have focused on the insect wing structure and its mechanical properties. The wings of dragonflies are mainly composed of veins and membranes, a typical nanocomposite material. The veins and membranes have a complex design within the wing that give rise to whole-wing characteristics which result in dragonflies being supremely versatile, maneuverable fliers. The wing structure, especially corrugation, on dragonflies is believed to enhance aerodynamic performance. The mechanical properties of dragonfly wings need to be understood in order to perform simulated models. This paper focuses on the effects of structure, mechanical properties, and morphology of dragonfly wings on their flyability, followed by the implications in fabrication and modeling.