Dynamic and quantitative assessment of blood coagulation using optical coherence elastography

NASA Astrophysics Data System (ADS)

Xu, Xiangqun; Zhu, Jiang; Chen, Zhongping

2016-04-01

Reliable clot diagnostic systems are needed for directing treatment in a broad spectrum of cardiovascular diseases and coagulopathy. Here, we report on non-contact measurement of elastic modulus for dynamic and quantitative assessment of whole blood coagulation using acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE). In this system, acoustic radiation force (ARF) is produced by a remote ultrasonic transducer, and a shear wave induced by ARF excitation is detected by the optical coherence tomography (OCT) system. During porcine whole blood coagulation, changes in the elastic property of the clots increase the shear modulus of the sample, altering the propagating velocity of the shear wave. Consequently, dynamic blood coagulation status can be measured quantitatively by relating the velocity of the shear wave with clinically relevant coagulation metrics, including reaction time, clot formation kinetics and maximum shear modulus. The results show that the ARFOE-OCE is sensitive to the clot formation kinetics and can differentiate the elastic properties of the recalcified porcine whole blood, blood added with kaolin as an activator, and blood spiked with fibrinogen.

Tensile strength of aluminium nitride films

NASA Astrophysics Data System (ADS)

Zong, Deng Gang; Ong, Chung Wo; Aravind, Manju; Tsang, Mei Po; Loong Choy, Chung; Lu, Deren; Ma, Dejun

2004-11-01

Two-layered aluminium nitride (AlN)/silicon nitride microbridges were fabricated for microbridge tests to evaluate the elastic modulus, residual stress and tensile strength of the AlN films. The silicon nitride layer was added to increase the robustness of the structure. In a microbridge test, load was applied to the centre of a microbridge and was gradually increased by a nano-indenter equipped with a wedge tip until the sample was broken, while displacement was recorded coherently. Measurements were performed on single-layered silicon nitride microbridges and two-layered AlN/silicon nitride microbridges respectively. The data were fitted to a theory to derive the elastic modulus, residual stress and tensile strength of the silicon nitride films and AlN films. For the AlN films, the three parameters were determined to be 200, 0.06 and 0.3 GPa, respectively. The values of elastic modulus obtained were consistent with those measured by conventional nano-indentation method. The tensile strength value can be used as a reference to reflect the maximum tolerable tensile stress of AlN films when they are used in micro-electromechanical devices.

Mechanical response of the flux lines in ceramic YBa2Cu3O7-δ

NASA Astrophysics Data System (ADS)

Luzuriaga, J.; André, M.-O.; Benoit, W.

1992-06-01

We have studied the mechanical response of the flux-line lattice (FLL) in ceramic samples of YBa2Cu3O7 by means of a low-frequency forced pendulum. The internal friction and elastic modulus variation of the FLL have been measured as a function of temperature for different values of the applied stress. A somewhat different behavior was observed whether a zero-field-cooling or field-cooling procedure was followed. Measurements of the internal friction and elastic modulus as a function of the applied stress at constant temperature show amplitude-dependent dissipation, with a maximum dissipation at intermediate values of the stress. This dependence is well fitted by a rheological model of extended dry friction, if we restrict ourselves to the dissipation and modulus at fixed temperature. The agreement is not so good when attempting to extend the model to fit the temperature dependence.

Mapping of elasticity and damping in an α + β titanium alloy through atomic force acoustic microscopy

PubMed Central

Phani, M Kalyan; Kumar, Anish; Jayakumar, T; Samwer, Konrad

2015-01-01

Summary The distribution of elastic stiffness and damping of individual phases in an α + β titanium alloy (Ti-6Al-4V) measured by using atomic force acoustic microscopy (AFAM) is reported in the present study. The real and imaginary parts of the contact stiffness k * are obtained from the contact-resonance spectra and by using these two quantities, the maps of local elastic stiffness and the damping factor are derived. The evaluation of the data is based on the mass distribution of the cantilever with damped flexural modes. The cantilever dynamics model considering damping, which was proposed recently, has been used for mapping of indentation modulus and damping of different phases in a metallic structural material. The study indicated that in a Ti-6Al-4V alloy the metastable β phase has the minimum modulus and the maximum damping followed by α′- and α-phases. Volume fractions of the individual phases were determined by using a commercial material property evaluation software and were validated by using X-ray diffraction (XRD) and electron back-scatter diffraction (EBSD) studies on one of the heat-treated samples. The volume fractions of the phases and the modulus measured through AFAM are used to derive average modulus of the bulk sample which is correlated with the bulk elastic properties obtained by ultrasonic velocity measurements. The average modulus of the specimens estimated by AFAM technique is found to be within 5% of that obtained by ultrasonic velocity measurements. The effect of heat treatments on the ultrasonic attenuation in the bulk sample could also be understood based on the damping measurements on individual phases using AFAM. PMID:25977847

Mapping of elasticity and damping in an α + β titanium alloy through atomic force acoustic microscopy.

PubMed

Phani, M Kalyan; Kumar, Anish; Jayakumar, T; Arnold, Walter; Samwer, Konrad

2015-01-01

The distribution of elastic stiffness and damping of individual phases in an α + β titanium alloy (Ti-6Al-4V) measured by using atomic force acoustic microscopy (AFAM) is reported in the present study. The real and imaginary parts of the contact stiffness k (*) are obtained from the contact-resonance spectra and by using these two quantities, the maps of local elastic stiffness and the damping factor are derived. The evaluation of the data is based on the mass distribution of the cantilever with damped flexural modes. The cantilever dynamics model considering damping, which was proposed recently, has been used for mapping of indentation modulus and damping of different phases in a metallic structural material. The study indicated that in a Ti-6Al-4V alloy the metastable β phase has the minimum modulus and the maximum damping followed by α'- and α-phases. Volume fractions of the individual phases were determined by using a commercial material property evaluation software and were validated by using X-ray diffraction (XRD) and electron back-scatter diffraction (EBSD) studies on one of the heat-treated samples. The volume fractions of the phases and the modulus measured through AFAM are used to derive average modulus of the bulk sample which is correlated with the bulk elastic properties obtained by ultrasonic velocity measurements. The average modulus of the specimens estimated by AFAM technique is found to be within 5% of that obtained by ultrasonic velocity measurements. The effect of heat treatments on the ultrasonic attenuation in the bulk sample could also be understood based on the damping measurements on individual phases using AFAM.

Elastic modulus of phases in Ti–Mo alloys

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

Zhang, Wei-dong; Liu, Yong, E-mail: yonliu11@aliyun.com; Wu, Hong

2015-08-15

In this work, a series of binary Ti–Mo alloys with the Mo contents ranging from 3.2 to 12 at.% were prepared using non-consumable arc melting. The microstructures were investigated by X-ray diffraction and transmission electron microscope, and the elastic modulus was evaluated by nanoindentation testing technique. The evolution of the volume fractions of ω phase was investigated using X-ray photoelectron spectroscopy. The results indicated that the phase constitution and elastic modulus of the Ti–Mo alloys are sensitive to the Mo content. Ti–3.2Mo and Ti–8Mo alloys containing only α and β phases, respectively, have a low elastic modulus. In contrast, Ti–4.5Mo,more » Ti–6Mo, Ti–7Mo alloys, with different contents of ω phase, have a high elastic modulus. A simple micromechanical model was used to calculate the elastic modulus of ω phase (E{sub ω}), which was determined to be 174.354 GPa. - Highlights: • Ti–Mo alloys with the Mo contents ranging from 3.2 to 12 at.% were investigated. • XPS was used to investigate the volume fractions of ω phase. • The elastic modulus of Ti–Mo alloys is sensitive to the Mo content. • The elastic modulus of ω phase was determined to be 174.354 GPa.« less

Apparent elastic modulus and hysteresis of skeletal muscle cells throughout differentiation

NASA Technical Reports Server (NTRS)

Collinsworth, Amy M.; Zhang, Sarah; Kraus, William E.; Truskey, George A.

2002-01-01

The effect of differentiation on the transverse mechanical properties of mammalian myocytes was determined by using atomic force microscopy. The apparent elastic modulus increased from 11.5 +/- 1.3 kPa for undifferentiated myoblasts to 45.3 +/- 4.0 kPa after 8 days of differentiation (P < 0.05). The relative contribution of viscosity, as determined from the normalized hysteresis area, ranged from 0.13 +/- 0.02 to 0.21 +/- 0.03 and did not change throughout differentiation. Myosin expression correlated with the apparent elastic modulus, but neither myosin nor beta-tubulin were associated with hysteresis. Microtubules did not affect mechanical properties because treatment with colchicine did not alter the apparent elastic modulus or hysteresis. Treatment with cytochalasin D or 2,3-butanedione 2-monoxime led to a significant reduction in the apparent elastic modulus but no change in hysteresis. In summary, skeletal muscle cells exhibited viscoelastic behavior that changed during differentiation, yielding an increase in the transverse elastic modulus. Major contributors to changes in the transverse elastic modulus during differentiation were actin and myosin.

Large-diameter carbon-composite monofilaments. [production method and characteristics of carbon composite monofilaments

NASA Technical Reports Server (NTRS)

Bradshaw, W. G.; Pinoli, P. C.; Karlak, R. F.

1974-01-01

Large-diameter carbon composite monofilaments with high strength and high modulus were produced by pregging multifiber carbon bundles with suitable organic resins and pyrolysing them together. Two approaches were developed to increase the utilization of fiber tensile strength by minimizing stress concentration defects induced by dissimilar shrinkage during pyrolysis. These were matrix modification to improve char yield and strain-to-failure and fiber-matrix copyrolysis to alleviate matrix cracking. Highest tensile strength and modulus were obtained by heat treatments to 2873 K to match fiber and matrix strain-to-failure and develop maximum monofilament tensile-strength and elastic modulus.

Shear-wave elastography for breast masses: local shear wave speed (m/sec) versus Young modulus (kPa).

PubMed

Youk, Ji Hyun; Son, Eun Ju; Park, Ah Young; Kim, Jeong-Ah

2014-01-01

To evaluate and compare the performance of shear-wave elastography (SWE) for breast masses using the local shear wave speed (m/sec) vs. Young modulus (kPa). A total of 130 breast lesions in 123 women who underwent SWE before ultrasound- guided core needle biopsy or surgical excision were included. With the region-of-interest placed over the stiffest areas of the lesion on SWE, the quantitative mean, maximum, and standard deviation (SD) of the elasticity values were measured in kPa and m/sec for each lesion. The SD was also measured with the region-of-interest including the whole breast lesion (wSD). The area under the receiver operating characteristic curve (AUC), sensitivity, and specificity of each elasticity value measured in kPa and m/sec were compared. Of the 130 lesions, 49 (37.7%) were malignant and 81 (62.3%) were benign. The AUCs for the mean, maximum, and SD of the elasticity values using kPa and m/sec did not differ significantly: mean, 0.974 vs. 0.974; maximum, 0.960 vs. 0.976; SD, 0.916 vs. 0.916. However, the AUC for wSD showed a significant difference: 0.964 (kPa) vs. 0.960 (m/sec) (P=0.036). There was no significant difference in the sensitivity and specificity of the mean, maximum, and wSD of the elasticity values. However, the specificity of the SD was significantly different between the two different measurements: 95.1% (kPa) vs. 87.7% (m/sec) (P=0.031). The quantitative elasticity values measured in kPa and m/sec on SWE showed good diagnostic performance. The specificity of the SD and AUC of the wSD measured in kPa were significantly higher than those measured in m/sec.

Viscoelastic/damage modeling of filament-wound spherical pressure vessels

NASA Technical Reports Server (NTRS)

Hackett, Robert M.; Dozier, Jan D.

1987-01-01

A model of the viscoelastic/damage response of a filament-wound spherical vessel used for long-term pressure containment is developed. The matrix material of the composite system is assumed to be linearly viscoelastic. Internal accumulated damage based upon a quadratic relationship between transverse modulus and maximum circumferential strain is postulated. The resulting nonlinear problem is solved by an iterative routine. The elastic-viscoelastic correspondence is employed to produce, in the Laplace domain, the associated elastic solution for the maximum circumferential strain which is inverted by the method of collocation to yield the time-dependent solution. Results obtained with the model are compared to experimental observations.

Understanding the Effect of Plastic Deformation on Elastic Modulus of Metals Based on a Percolation Model with Electron Work Function

NASA Astrophysics Data System (ADS)

Li, Qingda; Hua, Guomin; Lu, Hao; Yu, Bin; Li, D. Y.

2018-05-01

The elastic modulus of materials is usually treated as a constant in engineering applications. However, plastic deformation may result in changes in the elastic modulus of metallic materials. Using brass, aluminum, and low-carbon steel as sample materials, it is demonstrated that plastic deformation decreased the elastic modulus of the materials by 10% to 20%. A percolation model incorporating the electron work function is proposed to correlate such plastic-strain-induced variations in the elastic modulus to corresponding changes in the electron work function. Efforts are made to understand the observed phenomenon on an electronic basis. The obtained experimental results are consistent with the theoretical analysis.

Effect of ceramic thickness and composite bases on stress distribution of inlays--a finite element analysis.

PubMed

Durand, Letícia Brandão; Guimarães, Jackeline Coutinho; Monteiro Junior, Sylvio; Baratieri, Luiz Narciso

2015-01-01

The purpose of this study was to determine the effect of cavity depth, ceramic thickness, and resin bases with different elastic modulus on von Mises stress patterns of ceramic inlays. Tridimensional geometric models were developed with SolidWorks image software. The differences between the models were: depth of pulpal wall, ceramic thickness, and presence of composite bases with different thickness and elastic modulus. The geometric models were constrained at the proximal surfaces and base of maxillary bone. A load of 100 N was applied. The stress distribution pattern was analyzed with von Mises stress diagrams. The maximum von Mises stress values ranged from 176 MPa to 263 MPa and varied among the 3D-models. The highest von Mises stress value was found on models with 1-mm-thick composite resin base and 1-mm-thick ceramic inlay. Intermediate values (249-250 MPa) occurred on models with 2-mm-thick composite resin base and 1-mm-thick ceramic inlay and 1-mm-thick composite resin base and 2-mm-thick ceramic inlay. The lowest values were observed on models restored exclusively with ceramic inlay (176 MPa to 182 MPa). It was found that thicker inlays distribute stress more favorably and bases with low elastic modulus increase stress concentrations on the internal surface of the ceramic inlay. The increase of ceramic thickness tends to present more favorable stress distribution, especially when bonded directly onto the cavity without the use of supporting materials. When the use of a composite base is required, composite resin with high elastic modulus and reduced thickness should be preferred.

Effects of ablation depth and repair time on the corneal elastic modulus after laser in situ keratomileusis.

PubMed

Wang, Xiaojun; Li, Xiaona; Chen, Weiyi; He, Rui; Gao, Zhipeng; Feng, Pengfei

2017-01-17

The biomechanical properties of the cornea should be taken into account in the refractive procedure in order to perform refractive surgery more accurately. The effects of the ablation depth and repair time on the elastic modulus of the rabbit cornea after laser in situ keratomileusis (LASIK) are still unclear. In this study, LASIK was performed on New Zealand rabbits with different ablation depth (only typical LASIK flaps were created; residual stroma bed was 50 or 30% of the whole cornea thickness respectively). The animals without any treatment were served as normal controls. The corneal thickness was measured by ultrasonic pachymetry before animals were humanly killed after 7 or 28 days post-operatively. The corneal elastic modulus was measured by uniaxial tensile testing. A mathematical procedure considering the actual geometrics of the cornea was created to analyze the corneal elastic modulus. There were no obvious differences among all groups in the elastic modulus on after 7 days post-operatively. However, after 28th days post-operatively, there was a significant increase in the elastic modulus with 50 and 30% residual stroma bed; only the elastic modulus of the cornea with 30% residual stroma bed was significantly higher than that of 7 days. Changes in elastic modulus after LASIK suggest that this biomechanical effect may correlate with the ablation depth and repair time.

Change and anisotropy of elastic modulus in sheet metals due to plastic deformation

NASA Astrophysics Data System (ADS)

Ishitsuka, Yuki; Arikawa, Shuichi; Yoneyama, Satoru

2015-03-01

In this study, the effect of the plastic deformation on the microscopic structure and the anisotropy of the elastic modulus in the cold-rolled steel sheet (SPCC) is investigated. Various uniaxial plastic strains (0%, 2.5%, 5%, 7.5%, and 10%) are applied to the annealed SPCC plates, then, the specimens for the tensile tests are cut out from them. The elastic moduli in the longitudinal direction and the transverse direction to the direction that are pre-strained are measured by the tensile tests. Cyclic tests are performed to investigate the effects of the internal friction caused by the movable dislocations in the elastic deformation. Also, the movable dislocations are quantified by the boundary tracking for TEM micrographs. In addition, the behaviors of the change of the elastic modulus in the solutionized and thermal aged aluminum alloy (A5052) are measured to investigate the effect on the movable dislocations with the amount of the depositions. As a result in SPCC, the elastic moduli of the 0° and 90° directions decrease more than 10% as 10% prestrain applied. On the other hand, the elastic modulus shows the recovery behavior after the strain aging and the annealing. The movable dislocation and the internal friction show a tendency to increase as the plastic strain increases. The marked anisotropy is not observed in the elastic modulus and the internal friction. The elastic modulus in A5052 with many and few depositions decreases similarly by the plastic deformation. From the above, the movable dislocations affect the elastic modulus strongly without depending on the deposition amount. Moreover, the elastic modulus recovers after the plastic deformation by reducing the effects of them with the strain aging and the heat treatment.

Determination of elastic modulus of ceramics using ultrasonic testing

NASA Astrophysics Data System (ADS)

Sasmita, Firmansyah; Wibisono, Gatot; Judawisastra, Hermawan; Priambodo, Toni Agung

2018-04-01

Elastic modulus is important material property on structural ceramics application. However, bending test as a common method for determining this property require particular specimen preparation. Furthermore, elastic modulus of ceramics could vary because it depends on porosity content. For structural ceramics industry, such as ceramic tiles, this property is very important. This drives the development of new method to improve effectivity or verification method as well. In this research, ultrasonic testing was conducted to determine elastic modulus of soda lime glass and ceramic tiles. The experiment parameter was frequency of probe (1, 2, 4 MHz). Characterization of density and porosity were also done for analysis. Results from ultrasonic testing were compared with elastic modulus resulted from bending test. Elastic modulus of soda-lime glass based on ultrasonic testing showed excellent result with error 2.69% for 2 MHz probe relative to bending test result. Testing on red and white ceramic tiles were still contained error up to 41% and 158%, respectively. The results for red ceramic tile showed trend that 1 MHz probe gave better accuracy in determining elastic modulus. However, testing on white ceramic tile showed different trend. It was due to the presence of porosity and near field effect.

Developing the elastic modulus measurement of asphalt concrete using the compressive strength test

NASA Astrophysics Data System (ADS)

Setiawan, Arief; Suparma, Latif Budi; Mulyono, Agus Taufik

2017-11-01

Elastic modulus is a fundamental property of an asphalt mixture. An analytical method of the elastic modulus is needed to determine the thickness of flexible pavement. It has a role as one of the input values on a stress-strain analysis in the finite element method. The aim of this study was to develop the measurement of the elastic modulus by using compressive strength testing. This research used a set of specimen mold tool and Delta Dimensi software to record strain changes occurring in the proving ring of compression machine and the specimens. The elastic modulus of the five types of aggregate gradation and 2 types of asphalt were measured at optimum asphalt content. Asphalt Cement 60/70 and Elastomer Modified Asphalt (EMA) were used as a binder. Manufacturing success indicators of the specimens used void-in-the-mix (VIM) 3-5 % criteria. The success rate of the specimen manufacturing was more than 76%. Thus, the procedure and the compressive strength test equipment could be used for the measurement of the elastic modulus. The aggregate gradation and asphalt types significantly affected the elastic modulus of the asphalt concrete.

Lattice Mechanical Properties of Noble and Transition Metals

NASA Astrophysics Data System (ADS)

Baria, J. K.

2004-04-01

A model pseudopotential depending on an effective core radius but otherwise parameter free is used to study the interatomic interactions, phonon dispersion curves (in q and r-space analysis), phonon density of states, mode Grüneisen parameters, dynamical elastic constants ( C 11, C 12 and C 44), bulk modulus ( B), shear modulus ( C'), deviation from Cauchy relation ( C 12 C 44), Poisson’s ratio ( σ), Young’s modulus ( Y), behavior of phonon frequencies in the elastic limit independent of the direction ( Y 1), limiting value in the [110] direction ( Y 2), degree of elastic anisotropy ( A), maximum frequency ω max, mean frequency < ω>, < ω 2>1/2=(< ω>/< ω -1>)1/2, fundamental frequency < ω 2>, and propagation velocities of the elastic constants in Cu, Ag, Au, Ni, Pd, and Pt. The contribution of s-like electrons is calculated in the second-order perturbation theory for the model potential while that of d-like electrons is taken into account by introducing repulsive short-range Born-Mayer like term. Very recently proposed screening function due to Sarkar et al. has been used to obtain the screened form factor. The theoretical results are compared with experimental findings wherever possible. A good agreement between theoretical investigations and experimental findings has proved the ability of our model potential for predicting a large number of physical properties of transition metals.

Finite element analysis of stress-breaking attachments on maxillary implant-retained overdentures.

PubMed

Tanino, Fuminori; Hayakawa, Iwao; Hirano, Shigezo; Minakuchi, Shunsuke

2007-01-01

The purpose of this study was to examine the effect of stress-breaking attachments at the connections between maxillary palateless overdentures and implants. Three-dimensional finite element models were used to reproduce an edentulous human maxilla with an implant-retained overdenture. Two-implant models (in the canine tooth positions on both sides) and four-implant models (in the canine and second premolar tooth positions on both sides) were examined. Stress-breaking material connecting the implants and denture was included around each abutment. Axial loads of 100 N were applied to the occlusal surface at the left first molar tooth positions. In each model, the influence of the stress-breaking attachments was compared by changing the elastic modulus from 1 to 3,000 MPa and the thickness of the stress-breaking material from 1 to 3 mm. Maximum stress at the implant-bone interface and stress at the cortical bone surface just under the loading point were calculated. In all models, maximum stress at the implant-bone interface with implants located in the canine tooth position was generated at the peri-implant bone on the loading side. As the elastic modulus of the stress-breaking materials increased, the stress increased at the implant-bone interface and decreased at the cortical bone surface. Moreover, stress at the implant-bone interface with 3-mm-thick stress-breaking material was smaller than that with 1-mm-thick material. Within the limitations of this experiment, stress generated at the implant-bone interface could be controlled by altering the elastic modulus and thickness of the stress-breaking materials.

Indentation-derived elastic modulus of multilayer thin films: Effect of unloading induced plasticity

DOE PAGES

Jamison, Ryan Dale; Shen, Yu -Lin

2015-08-13

Nanoindentation is useful for evaluating the mechanical properties, such as elastic modulus, of multilayer thin film materials. A fundamental assumption in the derivation of the elastic modulus from nanoindentation is that the unloading process is purely elastic. In this work, the validity of elastic assumption as it applies to multilayer thin films is studied using the finite element method. The elastic modulus and hardness from the model system are compared to experimental results to show validity of the model. Plastic strain is shown to increase in the multilayer system during the unloading process. Additionally, the indentation-derived modulus of a monolayermore » material shows no dependence on unloading plasticity while the modulus of the multilayer system is dependent on unloading-induced plasticity. Lastly, the cyclic behavior of the multilayer thin film is studied in relation to the influence of unloading-induced plasticity. Furthermore, it is found that several cycles are required to minimize unloading-induced plasticity.« less

Modelling Pre-eruptive Progressive Damage in Basaltic Volcanoes: Consequences for the Pre-eruptive Process

NASA Astrophysics Data System (ADS)

Got, J. L.; Amitrano, D.; Carrier, A.; Marsan, D.; Jouanne, F.; Vogfjord, K. S.

2017-12-01

At Grimsvötn volcano, high-quality earthquake and continuous GPS data were recorded by the Icelandic Meteorological Office during its 2004-2011 inter-eruptive period and exhibited remarkable patterns : acceleration of the cumulated earthquake number, and a 2-year exponential decrease in displacement rate followed by a 4-year constant inflation rate. We proposed a model with one magma reservoir in a non-linear elastic damaging edifice, with incompressible magma and a constant pressure at the base of the magma conduit. We first modelled seismicity rate and damage as a function of time, and show that Kachanov's elastic brittle damage law may be used to express the decrease of the effective shear modulus with time. We then derived simple analytical expressions for the magma reservoir overpressure and the surface displacement as a function of time. We got a very good fit of the seismicity and surface displacement data by adjusting only three phenomenological parameters and computed magma reservoir overpressure, magma flow and strain power as a function of time. Overpressure decrease is controlled by damage and shear modulus decrease. Displacement increases, although overpressure is decreasing, because shear modulus decreases more than overpressure. Normalized strain power reaches a maximum 0.25 value. This maximum is a physical limit, after which the elasticity laws are no longer valid, earthquakes cluster, cumulative number of earthquakes departs from the model. State variable extrema provide four reference times that may be used to assess the mechanical state and dynamics of the volcanic edifice. We also performed the spatial modelling of the progressive damage and strain localization around a pressurized magma reservoir. We used Kachanov's damage law and finite element modelling of an initially elastic volcanic edifice pressurized by a spherical magma reservoir, with a constant pressure in the reservoir and various external boundary conditions. At each node of the model, Young's modulus is decreased if deviatoric stress locally reaches the Mohr-Coulomb plastic threshold. For a compressive horizontal stress, the result shows a complex strain localization pattern, showing reverse and normal faulting very similar to what is obtained from analog modelling and observed at volcanic resurgent domes.

Structural relaxation driven increase in elastic modulus for a bulk metallic glass

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

Arora, Harpreet Singh; Aditya, Ayyagari V.; Mukherjee, Sundeep, E-mail: sundeep.mukherjee@unt.edu

2015-01-07

The change in elastic modulus as a function of temperature was investigated for a zirconium-based bulk metallic glass. High temperature nano-indentation was done over a wide temperature range from room temperature to the glass-transition. At higher temperature, there was a transition from inhomogeneous to homogeneous deformation, with a decrease in serrated flow and an increase in creep displacement. Hardness was found to decrease, whereas elastic modulus was found to increase with temperature. The increase in elastic modulus for metallic glass at higher temperature was explained by diffusive rearrangement of atoms resulting in free volume annihilation. This is in contrast tomore » elastic modulus increase with temperature for silicate glasses due to compaction of its open three dimensional coordinated structure without any atomic diffusion.« less

Surface temperatures and glassy state investigations in tribology, part 2

NASA Technical Reports Server (NTRS)

Bair, S. S.; Winer, W. O.

1979-01-01

Measurements of lubricant shear rheological behavior in the amorphous solid region and near the liquid solid transition are reported. Elastic, plastic and viscous behavior was observed. The maximum yield shear stress (limiting shear stress) is a function of temperature and pressure and is believed to be the property which determines the maximum traction in elastohydrodynamic contacts such as traction drives. A shear rheological model based on primary laboratory data is proposed for concentrated contact lubrication. The model is Maxwell model modified with a limiting shear stress. Three material properties are required: low shear stress viscosity, limiting elastic shear modulus, and the limiting shear stress the material can withstand. All three are functions of temperature and pressure.

A biopulping mechanism : creation of acid groups on fiber

Treesearch

Chris Hunt; William Kenealy; Eric Horn; Carl Houtman

2004-01-01

We investigated how biopulping modifies chemical and physical properties of wood and how these changes affect the properties of the resulting fiber. Mechanical and chemical testing revealed wood cell changes during 2 weeks of colonization by Ceriporiopsis subvermispora. Typical mechanical properties, such as modulus of elasticity and maximum load, tracked reductions in...

Dynamic rheology of food protein networks

USDA-ARS?s Scientific Manuscript database

Small amplitude oscillatory shear analyses of samples containing protein are useful for determining the nature of the protein matrix without damaging it. Elastic modulus, viscous modulus, and loss tangent (the ratio of viscous modulus to elastic modulus) give information on the strength of the netw...

Nanomechanical properties of dental resin-composites.

PubMed

El-Safty, S; Akhtar, R; Silikas, N; Watts, D C

2012-12-01

To determine by nanoindentation the hardness and elastic modulus of resin-composites, including a series with systematically varied filler loading, plus other representative materials that fall into the categories of flowable, bulk-fill and conventional nano-hybrid types. Ten dental resin-composites: three flowable, three bulk-fill and four conventional were investigated using nanoindentation. Disc specimens (15mm×2mm) were prepared from each material using a metallic mold. Specimens were irradiated in the mold at top and bottom surfaces in multiple overlapping points (40s each) with light curing unit at 650mW/cm(2). Specimens were then mounted in 3cm diameter phenolic ring forms and embedded in a self-curing polystyrene resin. After grinding and polishing, specimens were stored in distilled water at 37°C for 7 days. Specimens were investigated using an Agilent Technologies XP nanoindenter equipped with a Berkovich diamond tip (100nm radius). Each specimen was loaded at one loading rate and three different unloading rates (at room temperature) with thirty indentations, per unloading rate. The maximum load applied by the nanoindenter to examine the specimens was 10mN. Dependent on the type of the resin-composite material, the mean values ranged from 0.73GPa to 1.60GPa for nanohardness and from 14.44GPa to 24.07GPa for elastic modulus. There was a significant positive non-linear correlation between elastic modulus and nanohardness (r(2)=0.88). Nonlinear regression revealed a significant positive correlation (r(2)=0.62) between elastic moduli and filler loading and a non-significant correlation (r(2)=0.50) between nanohardness and filler loading of the studied materials. Varying the unloading rates showed no consistent effect on the elastic modulus and nanohardness of the studied materials. For a specific resin matrix, both elastic moduli and nanohardness correlated positively with filler loading. For the resin-composites investigated, the group-average elastic moduli and nanohardnesses for bulk-fill and flowable materials were lower than those for conventional nano-hybrid composites. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Experimental and numerical study on frost heave of saturated rock under uniform freezing conditions

NASA Astrophysics Data System (ADS)

Lv, Zhitao; Xia, Caichu; Li, Qiang

2018-04-01

A series of freezing experiments are conducted on saturated sandstone and mortar specimens to investigate the frost heave of saturated rock under uniform freezing conditions. The experimental results show that the frost heave of saturated rock is isotropic under uniform freezing conditions. During the freezing process, three stages are observed in the curves of variation of total frost heaving strain versus time: the thermal contraction stage, the frost heaving stage and the steady stage. Moreover, the amount of final stable frost heave first increases and then decreases with decrease in freezing temperature, and the maximum final stable frost heave occurs at different freezing temperature in saturated sandstone and mortar. Furthermore, a coupled thermal-mechanical (TM) model of frost heave of saturated rock is proposed in which a constraint coefficient \\zeta is used to consider the susceptibility of the internal rock grain structure to the expansion of pore ice. Then, numerical simulations are implemented with COMSOL to solve the governing equations of the TM model. Comparisons of the numerical results with the experimental results are performed to demonstrate the reliability of the model. The influences of elastic modulus and porosity on frost heave are also investigated, and the results show that the total frost heaving strain decreases non-linearly with increasing elastic modulus, and the decrease is significant when the elastic modulus is less than 3000 MPa, or approximately five times the elastic modulus of ice. In addition, the total frost heaving strain increases linearly with increasing porosity. Finally, an empirical equation between total frost heaving strain and freezing temperature is proposed and the equation well describes the variation of total frost heaving strain with freezing temperature.

Muscle shear elastic modulus is linearly related to muscle torque over the entire range of isometric contraction intensity.

PubMed

Ateş, Filiz; Hug, François; Bouillard, Killian; Jubeau, Marc; Frappart, Thomas; Couade, Mathieu; Bercoff, Jeremy; Nordez, Antoine

2015-08-01

Muscle shear elastic modulus is linearly related to muscle torque during low-level contractions (<60% of Maximal Voluntary Contraction, MVC). This measurement can therefore be used to estimate changes in individual muscle force. However, it is not known if this relationship remains valid for higher intensities. The aim of this study was to determine: (i) the relationship between muscle shear elastic modulus and muscle torque over the entire range of isometric contraction and (ii) the influence of the size of the region of interest (ROI) used to average the shear modulus value. Ten healthy males performed two incremental isometric little finger abductions. The joint torque produced by Abductor Digiti Minimi was considered as an index of muscle torque and elastic modulus. A high coefficient of determination (R(2)) (range: 0.86-0.98) indicated that the relationship between elastic modulus and torque can be accurately modeled by a linear regression over the entire range (0% to 100% of MVC). The changes in shear elastic modulus as a function of torque were highly repeatable. Lower R(2) values (0.89±0.13 for 1/16 of ROI) and significantly increased absolute errors were observed when the shear elastic modulus was averaged over smaller ROI, half, 1/4 and 1/16 of the full ROI) than the full ROI (mean size: 1.18±0.24cm(2)). It suggests that the ROI should be as large as possible for accurate measurement of muscle shear modulus. Copyright © 2015 Elsevier Ltd. All rights reserved.

Stress distribution calculations through a snow slab of varying elastic modulus; comparison with stability evaluation in the field

NASA Astrophysics Data System (ADS)

Swinkels, Laura; Borstad, Chris

2017-04-01

Field observations are the main tools for assessing the snow stability concerning dry snow slab avalanche release. Often, theoretical studies cannot directly be translated into useful information for avalanche recreationists and forecasters in the field, and vice versa; field observations are not always objective and quantifiable for theoretical studies. Moreover, numerical models often simplify the snowpack and generally use an isotropic single layer slab which is not representative of the real-life situation. The aim of this study is to investigate the stress distribution in a snowpack with an elastic modulus that continuously varies with depth. The focus lies on the difference between a slab with a gradient in hardness and a slab with isotropic hardness and the effect on the calculated maximum stress and the stability evaluation in the field. Approximately 20 different snow pits were evaluated in the mountains around Tromsø, Norway and Longyearbyen, Svalbard. In addition to the standard snowpack observations, the hardness was measured using a thin-blade gauge. Extended column tests were executed for stability evaluation. Measurements from the field were used as input for stress calculations for each snow pit using a line load solution for a sloping half space with a non-homogeneous elastic modulus. The hardness measurements were used to calculate the elastic modulus and a power law relation was fit through the modulus in the slab. The calculated shear stress was compared to the estimated stability and character of the specific snowpack The results show that the approach used for this study improves the calculation of stress at a given depth, although many assumptions and simplifications were still needed. Comparison with the snow profiles indicate that calculated stresses correlate well with the observed snowpack properties and stability. The calculated shear stresses can be introduced in the standard stability index and give a better indication for the snowpack stability. Further research is required to delimit the stresses needed for propagation of a weak layer fracture.

Properties of medium-density fiberboard produced in an oil-heated laboratory press

Treesearch

O. Suchsland; G.E. Woodson

1976-01-01

Medium-density fiberboards from pressurized double-disk refined fibers have a close correlation between layer density and layer dynamic modulus of elasticity. Density distribution over the thickness was readily controlled by manipulating platen temperature and applied pressure. Thus, overall modulus of elasticity could be adjusted. In contrast to modulus of elasticity...

Effects of vitamin K2 (menatetrenone) and alendronate on bone mineral density and bone strength in rats fed a low-magnesium diet.

PubMed

Kobayashi, M; Hara, K; Akiyama, Y

2004-11-01

In this study, we examined changes in bone parameters and bone strength in rats fed low-Mg diets (experiment 1) and the effects of vitamin K2 (MK-4, experiment 3) and alendronate (ALN, experiment 2) in this model. In experiment 1, 5-week-old male Wistar rats were fed three low-Mg diets (Mg 9, 6, 3 mg/100 g diet) for 4 weeks. Although the cortical bone mineral content (CtBMC) and cortical thickness (CtTh) of the femoral diaphysis in all low-Mg-diet groups were the same as or greater than those in the intact group (Mg: 90 mg/100 g diet), the maximum load and elastic modulus were significantly reduced in the 3-mg-Mg group. In experiment 2, 4-week-old Wistar rats were fed a 6-mg-Mg diet for 8 weeks, and the effect of ALN (2, 20, and 200 microg/kg twice a week) was evaluated. The administration of ALN at 200 microg/kg increased the cortical bone mineral content (CtBMC), CtTh, and maximum load, but had no effect on the elastic modulus, as compared with the low-Mg-control group. In experiment 3, the effect of MK-4 was evaluated under the same conditions as in experiment 2. The administration of MK-4 had no effect on CtBMC, CtTh, or bone components of the femoral diaphysis. However, MK-4 inhibited the decreases in maximum load and elastic modulus due to the low-Mg diet. Since there is no other experimental model in which there is a decrease in bone mechanical properties without a decrease in bone mineral content, the low-Mg diet model is considered to be an excellent model for examining bone quality. Our results from this model suggest that MK-4 and ALN affect bone mechanical properties by different mechanisms.

Stress-strain state of reinforced bimodulus beam on an elastic foundation

NASA Astrophysics Data System (ADS)

Beskopylny, A. N.; Kadomtseva, E. E.; Strelnikov, G. P.; Berdnik, Y. A.

2017-10-01

The paper provides the calculation theory of an arbitrary supported and arbitrary loaded reinforced beam filled with bimodulus material. The formulas determining normal stresses, bending moments, shear forces, rotation angles and a deflection of a rectangular crosssection beam reinforced with any number of bars aligned parallel to the beam axis have been obtained. The numerical study has been carried out to investigate an influence of a modulus of subgrade reaction on values of maximum normal stresses, maximum bending moments and a maximum deflection of a hinged supported beam loaded with a point force or uniform distributed load. The estimation is based on the method of initial parameters for a beam on elastic foundation and the Bubnov-Galerkin method. Values of maximum deflections, maximum bending moments and maximum stresses obtained by these methods coincide. The numerical studies show that taking into consideration the bimodulus of material leads to the necessity to calculate the strength analysis of both tensile stresses and compressive stresses.

Influence of Selected Factors on the Relationship between the Dynamic Elastic Modulus and Compressive Strength of Concrete

PubMed Central

Jurowski, Krystian; Grzeszczyk, Stefania

2018-01-01

In this paper, the relationship between the static and dynamic elastic modulus of concrete and the relationship between the static elastic modulus and compressive strength of concrete have been formulated. These relationships are based on investigations of different types of concrete and take into account the type and amount of aggregate and binder used. The dynamic elastic modulus of concrete was tested using impulse excitation of vibration and the modal analysis method. This method could be used as a non-destructive way of estimating the compressive strength of concrete. PMID:29565830

Influence of Selected Factors on the Relationship between the Dynamic Elastic Modulus and Compressive Strength of Concrete.

PubMed

Jurowski, Krystian; Grzeszczyk, Stefania

2018-03-22

In this paper, the relationship between the static and dynamic elastic modulus of concrete and the relationship between the static elastic modulus and compressive strength of concrete have been formulated. These relationships are based on investigations of different types of concrete and take into account the type and amount of aggregate and binder used. The dynamic elastic modulus of concrete was tested using impulse excitation of vibration and the modal analysis method. This method could be used as a non-destructive way of estimating the compressive strength of concrete.

[Influence of sterilization treatments on continuous carbon-fiber reinforced polyolefin composite].

PubMed

Guan, Shi-bing; Hou, Chun-lin; Chen, Ai-min; Zhang, Wei; Wang, Ji-e

2007-08-21

To evaluate the influence of sterilization treatment on continuous carbon-fiber reinforced polyolefin composite (CFRP) so as to provide experimental reference for selection of sterilization method for CFRP. Seventy bars of CFRP were divided into 7 equal groups to undergo sterilization by autoclave, 2% glutaraldehyde soaking, 75% alcohol soaking, ethylene oxide sterilization, and Co-60 gamma ray irradiation of the dosages 11 kGy, 25 kGy, and 18 kGy respectively, and another 10 bars were used as blank controls. Then the bars underwent three-point bending test and longitudinal compression test so as to measure the biomechanical changes after sterilization treatment, including the maximum load, ultimate strength, and elastic modulus. Three-point bending test showed that the levels of maximum load of the all experimental groups were lower than that of the control group, however, only those of the 3 Co-60 irradiation groups were significantly lower than that of the control group and that Co-60 radiation lowered the level of maximum load dose-dependently; and that the levels of ultimate strength of all the all experimental groups were lower than that of the control group, however, only those of the 3 Co-60 groups were significantly lower than that of the control group and that the higher the dosage of Co-60 radiation the lower the level of ultimate strength, however, not dose-dependently. The elastic modulus of the Co-60 25 KGy group was significantly higher than that of the control group, and there was no significant difference in the level of ultimate strength among the other groups. Longitudinal compression test showed that the levels of maximum load and ultimate strength of the 3 Co-60 irradiation groups, autoclave group, and circular ethylene groups were significantly lower than that of the control group, and there was no significant difference in elastic modulus among different groups. During sterilized package of CFRP products produced in quantity autoclave sterilization and Co-60 gamma ray irradiation sterilization should be avoided. Ethylene oxide is proposed as the best sterilization method. If gamma ray irradiation is to be used further technology improvement is necessary.

Oscillatory shear response of moisture barrier coatings containing clay of different shape factor.

PubMed

Kugge, C; Vanderhoek, N; Bousfield, D W

2011-06-01

Oscillatory shear rheology of barrier coatings based on dispersed styrene-butadiene latex and clay of various shape factors or aspect ratio has been explored. Barrier performance of these coatings when applied to paperboard has been assessed in terms of water vapour transmission rates and the results related to shape factor, dewatering and critical strain. It has been shown that a system based on clay with high shape factor gives a lower critical strain, dewatering and water vapour transmission rate compared with clays of lower shape factor. The dissipated energy, as calculated from an amplitude sweep, indicated no attractive interaction between clay and latex implying a critical strain that appears to be solely dependent on the shape factor at a constant volume fraction. Particle size distribution was shown to have no effect on the critical strain while coatings of high elasticity exhibited high yield strains as expected. The loss modulus demonstrated strain hardening before the elastic to viscous transition. The loss modulus peak was identified by a maximum strain which was significantly lower for a coating based on clay with a high shape factor. The characteristic elastic time was found to vary between 0.6 and 1.3s. The zero shear viscosity of barrier dispersion coatings were estimated from the characteristic elastic time and the characteristic modulus to be of the order of 25-100 Pa s. Copyright © 2011 Elsevier Inc. All rights reserved.

Elastic modulus of single cellulose microfibrils from tunicate measured by atomic force microscopy.

PubMed

Iwamoto, Shinichiro; Kai, Weihua; Isogai, Akira; Iwata, Tadahisa

2009-09-14

The elastic modulus of single microfibrils from tunicate ( Halocynthia papillosa ) cellulose was measured by atomic force microscopy (AFM). Microfibrils with cross-sectional dimensions 8 x 20 nm and several micrometers in length were obtained by oxidation of cellulose with 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) as a catalyst and subsequent mechanical disintegration in water and by sulfuric acid hydrolysis. The nanocellulosic materials were deposited on a specially designed silicon wafer with grooves 227 nm in width, and a three-point bending test was applied to determine the elastic modulus using an AFM cantilever. The elastic moduli of single microfibrils prepared by TEMPO-oxidation and acid hydrolysis were 145.2 +/- 31.3 and 150.7 +/- 28.8 GPa, respectively. The result showed that the experimentally determined modulus of the highly crystalline tunicate microfibrils was in agreement with the elastic modulus of native cellulose crystals.

Development of Nondestructive Non-Contact Acousto-Thermal Evaluation Technique for Damage Detection in Materials (Postprint)

DTIC Science & Technology

2012-09-01

and the sample to obtain a repeatable excitation for detec- tion of the damage of interest. Varieties of materials, includ- ing card stock, leather ...2) where Tan δ is the internal friction in the material, E is the Young’s modulus, and σmax is the maximum amplitude of the acoustic wave. Assuming...interior of a linear elastic material can be seen to depend on both the elastic properties (E and Tan δ) and the thermal properties (k, Cp) of the

A reassessment of the compressive strength properties of southern yellow pine bark

Treesearch

Thomas L. Eberhardt

2007-01-01

Samples of southern yellow pine outer bark and wood were tested in compression to determine values for modulus of elasticity, stress at proportional limit, and maximum crushing strength. Results reported here resolve inconsistencies in the compressive strength data previously reported by others for pine bark. Testing of solvent-treated bark blocks suggests that...

Micromechanical analysis on anisotropy of structured magneto-rheological elastomer

NASA Astrophysics Data System (ADS)

Li, R.; Zhang, Z.; Chen, S. W.; Wang, X. J.

2015-07-01

This paper investigates the equivalent elastic modulus of structured magneto-rheological elastomer (MRE) in the absence of magnetic field. We assume that both matrix and ferromagnetic particles are linear elastic materials, and ferromagnetic particles are embedded in matrix with layer-like structure. The structured composite could be divided into matrix layer and reinforced layer, in which the reinforced layer is composed of matrix and the homogenously distributed ferromagnetic particles in matrix. The equivalent elastic modulus of reinforced layer is analysed by the Mori-Tanaka method. Finite Element Method (FEM) is also carried out to illustrate the relationship between the elastic modulus and the volume fraction of ferromagnetic particles. The results show that the anisotropy of elastic modulus becomes noticeable, as the volume fraction of particles increases.

Ab-initio study of electronic structure and elastic properties of ZrC

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

Mund, H. S., E-mail: hmoond@gmail.com; Ahuja, B. L.

2016-05-23

The electronic and elastic properties of ZrC have been investigated using the linear combination of atomic orbitals method within the framework of density functional theory. Different exchange-correlation functionals are taken into account within generalized gradient approximation. We have computed energy bands, density of states, elastic constants, bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, lattice parameters and pressure derivative of the bulk modulus by calculating ground state energy of the rock salt structure type ZrC.

Lipid Neuroprotectants and Traumatic Glaucomatous Neurodegeneration

DTIC Science & Technology

2016-05-01

alter elastic TM, modulus and binding and functional assays with potential protein targets. Endogenous lipids, Aqueous humor, Trabecular meshwork...Intraocular pressure, sphingolipids, primary cell culture, elastic modulus, protein targets. Major goal 1. Test the hypothesis that selected lipids...glaucomatous TM with and without these lipids and atomic force microscope (AFM). Further elastic modulus using high flow and low flow areas of glaucomatous

Influence of Waste Tyre Crumb Rubber on Compressive Strength, Static Modulus of Elasticity and Flexural Strength of Concrete

NASA Astrophysics Data System (ADS)

Haridharan, M. K.; Bharathi Murugan, R.; Natarajan, C.; Muthukannan, M.

2017-07-01

In this paper, the experimental investigations was carried out to find the compressive strength, static modulus of elasticity and flexural strength of concrete mixtures, in which natural sand was partially replaced with Waste Tyre Crumb Rubber (WTCR). River sand was replaced with five different percentages (5%, 10%, 15%, 20% and 25%) of WTCR by volume. The main objective of the experimental investigation is to find the relationship between static modulus of elasticity and flexural strength with compressive strength of concrete with WTCR. The experimentally obtainedstatic modulus of elasticity and flexural strength results comparing with the theoretical values (various country codes recommendations).

Prediction study of structural, elastic and electronic properties of FeMP (M = Ti, Zr, Hf) compounds

NASA Astrophysics Data System (ADS)

Tanto, A.; Chihi, T.; Ghebouli, M. A.; Reffas, M.; Fatmi, M.; Ghebouli, B.

2018-06-01

First principles calculations are applied in the study of FeMP (M = Ti, Zr, Hf) compounds. We investigate the structural, elastic, mechanical and electronic properties by combining first-principles calculations with the CASTEP approach. For ideal polycrystalline FeMP (M = Ti, Zr, Hf) the shear modulus, Young's modulus, Poisson's ratio, elastic anisotropy indexes, Pugh's criterion, elastic wave velocities and Debye temperature are also calculated from the single crystal elastic constants. The shear anisotropic factors and anisotropy are obtained from the single crystal elastic constants. The Debye temperature is calculated from the average elastic wave velocity obtained from shear and bulk modulus as well as the integration of elastic wave velocities in different directions of the single crystal.

Shear elastic modulus estimation from indentation and SDUV on gelatin phantoms

PubMed Central

Amador, Carolina; Urban, Matthew W.; Chen, Shigao; Chen, Qingshan; An, Kai-Nan; Greenleaf, James F.

2011-01-01

Tissue mechanical properties such as elasticity are linked to tissue pathology state. Several groups have proposed shear wave propagation speed to quantify tissue mechanical properties. It is well known that biological tissues are viscoelastic materials; therefore velocity dispersion resulting from material viscoelasticity is expected. A method called Shearwave Dispersion Ultrasound Vibrometry (SDUV) can be used to quantify tissue viscoelasticity by measuring dispersion of shear wave propagation speed. However, there is not a gold standard method for validation. In this study we present an independent validation method of shear elastic modulus estimation by SDUV in 3 gelatin phantoms of differing stiffness. In addition, the indentation measurements are compared to estimates of elasticity derived from shear wave group velocities. The shear elastic moduli from indentation were 1.16, 3.40 and 5.6 kPa for a 7, 10 and 15% gelatin phantom respectively. SDUV measurements were 1.61, 3.57 and 5.37 kPa for the gelatin phantoms respectively. Shear elastic moduli derived from shear wave group velocities were 1.78, 5.2 and 7.18 kPa for the gelatin phantoms respectively. The shear elastic modulus estimated from the SDUV, matched the elastic modulus measured by indentation. On the other hand, shear elastic modulus estimated by group velocity did not agree with indentation test estimations. These results suggest that shear elastic modulus estimation by group velocity will be bias when the medium being investigated is dispersive. Therefore a rheological model should be used in order to estimate mechanical properties of viscoelastic materials. PMID:21317078

The effect of the addition of sorbitol and glycerol towards the edible film characteristics of the belitung taro starch and the lime leaves as antimicrobial

NASA Astrophysics Data System (ADS)

Asria, Merry; Elizarni, Samah, dan Selfa Dewati

2015-12-01

Plastics have been generally used for food packaging, but plastics using causing environmental problem for as non biodegradable. Resolving the problem need another alternative packaging that environmental friendly such as the edible film as biodegradable packing material. This research intend to determination the effects of sorbitol and glycerol (concentration of 1%, 2%, 3%, and 4%) as addition to the edible film characteristics from the belitung taro starch (Xanthosoma sagitifolium). Lime leaves (Citrus aurantifolia) extract used as an antimicrobial film (2%, 4%, 6%, 8%, and 10% respectively). From the research obtained that using sorbitol has given more rigid and hard film texture, while glycerol provides more elastic and flexible texture. Sorbitol give best performance at 2% where thickness 0.17 mm; tensile strength 41.60 MPa; yield strength 34.28 MPa; modulus of elasticity 7983.71 MPa; and maximum strain 29,8%. While, glycerol (2%) provides thickness 0.18 mm; tensile strength 35.72 MPa; yield strength 30.78 MPa; modulus of elasticity 9065.90 MPa; and maximum strain 14.4% for best performance. SEM and FTIR analysis applied to determine film surface morphology's characterization and determine the functional groups of the film materials. The addition of lime leaves extract as antimicrobial gives the growth inhibition activity against the Staphylococcus aureus bacteria.

Ultrasound - Aided ejection in micro injection molding

NASA Astrophysics Data System (ADS)

Masato, D.; Sorgato, M.; Lucchetta, G.

2018-05-01

In this work, an ultrasound-aided ejection system was designed and tested for different polymers (PS, COC and POM) and mold topographies. The proposed solution aims at reducing the ejection friction by decreasing the adhesion component of the frictional force, which is controlled by the contact area developed during the filling stage of the injection molding process. The experimental results indicate a positive effect of ultrasound vibration on the friction force values, with a maximum reduction of 16. Moreover, it is demonstrated that the ultrasound effect is strictly related to both polymer selection and mold roughness. The combined effect on the ejection force of mold surface roughness, melt viscosity during filling and polymer elastic modulus at ejection was modeled to the experimental data, in order to demonstrate that the effect of ultrasound vibration on the ejection friction reduction is due to the heating of the contact interface and the consequent reduction of the polymer elastic modulus.

The effect of woven and non-woven fiber structure on mechanical properties polyester composite reinforced kenaf

NASA Astrophysics Data System (ADS)

Ratim, S.; Bonnia, N. N.; Surip, S. N.

2012-07-01

The effects of woven and non-woven kenaf fiber on mechanical properties of polyester composites were studied at different types of perform structures. Composite polyester reinforced kenaf fiber has been prepared via hand lay-up process by varying fiber forms into plain weave, twill and mats structure. The reinforcing efficiency of different fiber structure was compared with control of unreinforced polyester sample. It was found that the strength and stiffness of the composites are largely affected by fiber structure. A maximum value for tensile strength of composite was obtained for twill weave pattern of fiber structure while no significant different for plain weave and mat structure. The elastic modulus of composite has shown some improvement on plain and twill weave pattern. Meanwhile, lower value of modulus elasticity achieved by mats structure composite as well as control sample. The modulus of rupture and impact resistance were also analyzed. The improvement of modulus of rupture value can be seen on plain and twill weave pattern. However impact resistance doesn't show significant improvement in all types of structure except for mat fiber. The mechanical properties of kenaf fiber reinforced polyester composite found to be increased with woven and non-woven fiber structures in composite.

Ab initio predictions of structural and elastic properties of struvite: contribution to urinary stone research.

PubMed

Piechota, Jacek; Prywer, Jolanta; Torzewska, Agnieszka

2012-01-01

In the present work, we carried out density functional calculations of struvite--the main component of the so-called infectious urinary stones--to study its structural and elastic properties. Using a local density approximation and a generalised gradient approximation, we calculated the equilibrium structural parameters and elastic constants C(ijkl). At present, there is no experimental data for these elastic constants C (ijkl) for comparison. Besides the elastic constants, we also present the calculated macroscopic mechanical parameters, namely the bulk modulus (K), the shear modulus (G) and Young's modulus (E). The values of these moduli are found to be in good agreement with available experimental data. Our results imply that the mechanical stability of struvite is limited by the shear modulus, G. The study also explores the energy-band structure to understand the obtained values of the elastic constants.

Effects of strain rate, mixing ratio, and stress-strain definition on the mechanical behavior of the polydimethylsiloxane (PDMS) material as related to its biological applications.

PubMed

Khanafer, Khalil; Duprey, Ambroise; Schlicht, Marty; Berguer, Ramon

2009-04-01

Tensile tests on Polydimethylsiloxane (PDMS) materials were conducted to illustrate the effects of mixing ratio, definition of the stress-strain curve, and the strain rate on the elastic modulus and stress-strain curve. PDMS specimens were prepared according to the ASTM standards for elastic materials. Our results indicate that the physiological elastic modulus depends strongly on the definition of the stress-strain curve, mixing ratio, and the strain rate. For various mixing ratios and strain rates, true stress-strain definition results in higher stress and elastic modulus compared with engineering stress-strain and true stress-engineering strain definitions. The elastic modulus increases as the mixing ratio increases up-to 9:1 ratio after which the elastic modulus begins to decrease even as the mixing ratio continues to increase. The results presented in this study will be helpful to assist the design of in vitro experiments to mimic blood flow in arteries and to understand the complex interaction between blood flow and the walls of arteries using PDMS elastomer.

Modulus of Elasticity and Thermal Expansion Coefficient of ITO Film

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

Carter, Austin D.; Elhadj, S.

2016-06-24

The purpose of this experiment was to determine the modulus of elasticity (E) and thermal expansion coefficient (α) of RF sputtered Indium Tin Oxide (ITO) as a function of temperature (T), and to collect ITO film stress data. In order to accomplish that goal, the Toho FLX-2320-S thin film stress measurement machine was used to collect both single stress and stress-temperature data for ITO coated fused silica and sapphire substrates. The stress measurement function of the FLX-2320-S cannot be used to calculate the elastic modulus of the film because the Stoney formula incorporates the elastic modulus of the substrate, rathermore » than of the film itself.« less

Snake fangs: 3D morphological and mechanical analysis by microCT, simulation, and physical compression testing.

PubMed

du Plessis, Anton; Broeckhoven, Chris; le Roux, Stephan G

2018-01-01

This Data Note provides data from an experimental campaign to analyse the detailed internal and external morphology and mechanical properties of venomous snake fangs. The aim of the experimental campaign was to investigate the evolutionary development of 3 fang phenotypes and investigate their mechanical behaviour. The study involved the use of load simulations to compare maximum Von Mises stress values when a load is applied to the tip of the fang. The conclusions of this study have been published elsewhere, but in this data note we extend the analysis, providing morphological comparisons including details such as curvature comparisons, thickness, etc. Physical compression results of individual fangs, though reported in the original paper, were also extended here by calculating the effective elastic modulus of the entire snake fang structure including internal cavities for the first time. This elastic modulus of the entire fang is significantly lower than the locally measured values previously reported from indentation experiments, highlighting the possibility that the elastic modulus is higher on the surface than in the rest of the material. The micro-computed tomography (microCT) data are presented both in image stacks and in the form of STL files, which simplifies the handling of the data and allows its re-use for future morphological studies. These fangs might also serve as bio-inspiration for future hypodermic needles. © The Author 2017. Published by Oxford University Press.

Properties of southern pine needles

Treesearch

E.T. Howard

1973-01-01

To investigate properties that might be related to utilization, needles were sampled on one tree of each of the four major species. Tensile strength was measured on loblolly needles only; it ranged from 4,630 to 6,980 psi. Maximum load averaged 4.1 pounds per needle, with a modulus of elasticity of 220,000 psi. Specific gravity (ovendry weight, green volume of...

Cell wall elasticity: I. A critique of the bulk elastic modulus approach and an analysis using polymer elastic principles

NASA Technical Reports Server (NTRS)

Wu, H. I.; Spence, R. D.; Sharpe, P. J.; Goeschl, J. D.

1985-01-01

The traditional bulk elastic modulus approach to plant cell pressure-volume relations is inconsistent with its definition. The relationship between the bulk modulus and Young's modulus that forms the basis of their usual application to cell pressure-volume properties is demonstrated to be physically meaningless. The bulk modulus describes stress/strain relations of solid, homogeneous bodies undergoing small deformations, whereas the plant cell is best described as a thin-shelled, fluid-filled structure with a polymer base. Because cell walls possess a polymer structure, an alternative method of mechanical analysis is presented using polymer elasticity principles. This initial study presents the groundwork of polymer mechanics as would be applied to cell walls and discusses how the matrix and microfibrillar network induce nonlinear stress/strain relationships in the cell wall in response to turgor pressure. In subsequent studies, these concepts will be expanded to include anisotropic expansion as regulated by the microfibrillar network.

The Effect of Annealing on the Elastic Modulus of Orthodontic Wires

NASA Astrophysics Data System (ADS)

Higginbottom, Kyle

Introduction: Nickel Titanium orthodontic wires are currently used in orthodontic treatment due to their heat activated properties and their delivery of constant force. The objective of this study was to determine the effect of annealing on the elastic modulus of Nickel Titanium, Stainless Steel and Beta-titanium (TMA) wires. Different points along the wire were tested in order to determine how far from the annealed ends the elastic modulus of the wires was affected. Methods: Eighty (80) orthodontic wires consisting of 4 equal groups (SS/TMA/Classic NitinolRTM/Super Elastic NitinolRTM) were used as the specimens for this study. All wires were measured and marked at 5mm measurements, and cut into 33.00mm sections. The wires were heated with a butane torch until the first 13.00mm of the wires were red hot. Load deflection tests using an InstronRTM universal testing machine were run at 5mm distances from the end of the wire that had been annealed. The change in elastic modulus was then determined. Results: There was a significant difference (F = 533.001, p = 0.0005) in the change in elastic modulus for the four distances. There was also a significant difference (F = 57.571, p = 0.0005) in the change in elastic modulus for the four wire types. There was a significant interaction (F = 19.601, p = 0.005) between wire type and distance, however this interaction negated the differences between the wires. Conclusion: 1) There are significant differences in the changes in elastic modulus between the areas of the wires within the annealed section and those areas 5mm and 10mm away from the annealed section. The change in elastic modulus within the annealed section was significantly greater at 8 mm than it was at 13mm, and this was significantly greater than 18mm and 23mm (5mm and 10mm beyond the annealed section). However, there was no statistical difference in the change in elastic modulus between 5mm and 10mm away from the annealed section (18mm and 23mm respectively). 2) Regardless of the wire type, no clinically important effects were seen 5mm and 10mm beyond the annealed portion.

Abnormal elastic modulus behavior in a crystalline-amorphous core-shell nanowire system.

PubMed

Lee, Jeong Hwan; Choi, Su Ji; Kwon, Ji Hwan; Van Lam, Do; Lee, Seung Mo; Kim, An Soon; Baik, Hion Suck; Ahn, Sang Jung; Hong, Seong Gu; Yun, Yong Ju; Kim, Young Heon

2018-06-13

We investigated the elastic modulus behavior of crystalline InAs/amorphous Al2O3 core-shell heterostructured nanowires with shell thicknesses varying between 10 and 90 nm by conducting in situ tensile tests inside a transmission electron microscope (TEM). Counterintuitively, the elastic modulus behaviors of InAs/Al2O3 core-shell nanowires differ greatly from those of bulk-scale composite materials, free from size effects. According to our results, the elastic modulus of InAs/Al2O3 core-shell nanowires increases, peaking at a shell thickness of 40 nm, and then decreases in the range of 50-90 nm. This abnormal behavior is attributed to the continuous decrease in the elastic modulus of the Al2O3 shell as the thickness increases, which is caused by changes in the atomic/electronic structure during the atomic layer deposition process and the relaxation of residual stress/strain in the shell transferred from the interfacial mismatch between the core and shell materials. A novel method for estimating the elastic modulus of the shell in a heterostructured core-shell system was suggested by considering these two effects, and the predictions from the suggested method coincided well with the experimental results. We also found that the former and latter effects account for 89% and 11% of the change in the elastic modulus of the shell. This study provides new insight by showing that the size dependency, which is caused by the inhomogeneity of the atomic/electronic structure and the residual stress/strain, must be considered to evaluate the mechanical properties of heterostructured nanowires.

Nanostructure and elastic modulus of single trabecula in bovine cancellous bone.

PubMed

Yamada, Satoshi; Tadano, Shigeru; Fukuda, Sakurako

2014-11-07

We aimed to investigate the elastic modulus of trabeculae using tensile tests and assess the effects of nanostructure at the hydroxyapatite (HAp) crystal scale on the elastic modulus. In the experiments, 18 trabeculae that were at least 3mm in length in the proximal epiphysis of three adult bovine femurs were used. Tensile tests were conducted using a small tensile testing device coupled with microscopy under air-dried condition. The c-axis orientation of HAp crystals and the degree of orientation were measured by X-ray diffraction. To observe the deformation behavior of HAp crystals under tensile loading, the same tensile tests were conducted in X-ray diffraction measurements. The mineral content of specimens was evaluated using energy dispersive X-ray spectrometry. The elastic modulus of a single trabecula varied from 4.5 to 23.6 GPa, and the average was 11.5 ± 5.0 GPa. The c-axis of HAp crystals was aligned with the trabecular axis and the crystals were lineally deformed under tensile loading. The ratio of the HAp crystal strain to the tissue strain (strain ratio) had a significant correlation with the elastic modulus (r=0.79; P<0.001). However, the mineral content and the degree of orientation did not vary widely and did not correlate with the elastic modulus in this study. It suggests that the strain ratio may represent the nanostructure of a single trabecula and would determine the elastic modulus as well as mineral content and orientation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Random field assessment of nanoscopic inhomogeneity of bone

PubMed Central

Dong, X. Neil; Luo, Qing; Sparkman, Daniel M.; Millwater, Harry R.; Wang, Xiaodu

2010-01-01

Bone quality is significantly correlated with the inhomogeneous distribution of material and ultrastructural properties (e.g., modulus and mineralization) of the tissue. Current techniques for quantifying inhomogeneity consist of descriptive statistics such as mean, standard deviation and coefficient of variation. However, these parameters do not describe the spatial variations of bone properties. The objective of this study was to develop a novel statistical method to characterize and quantitatively describe the spatial variation of bone properties at ultrastructural levels. To do so, a random field defined by an exponential covariance function was used to present the spatial uncertainty of elastic modulus by delineating the correlation of the modulus at different locations in bone lamellae. The correlation length, a characteristic parameter of the covariance function, was employed to estimate the fluctuation of the elastic modulus in the random field. Using this approach, two distribution maps of the elastic modulus within bone lamellae were generated using simulation and compared with those obtained experimentally by a combination of atomic force microscopy and nanoindentation techniques. The simulation-generated maps of elastic modulus were in close agreement with the experimental ones, thus validating the random field approach in defining the inhomogeneity of elastic modulus in lamellae of bone. Indeed, generation of such random fields will facilitate multi-scale modeling of bone in more pragmatic details. PMID:20817128

Elastic modulus of nanomaterials: resonant contact-AFM measurement and reduced-size effects (Invited Paper)

NASA Astrophysics Data System (ADS)

Nysten, Bernard; Fretigny, Christian; Cuenot, Stephane

2005-05-01

Resonant contact atomic force microscopy (resonant C-AFM) is used to quantitatively measure the elastic modulus of polymer nanotubes and metallic nanowires. To achieve this, an oscillating electric field is applied between the sample holder and the microscope head to excite the oscillation of the cantilever in contact with the nanostructures suspended over the pores of a membrane. The resonance frequency of the cantilever with the tip in contact with a nanostructure is shifted to higher values with respect to the resonance frequency of the free cantilever. It is demonstrated that the system can simply be modeled by a cantilever with the tip in contact with two springs. The measurement of the frequency shift enables the direct determination of the spring stiffness, i.e. the nanowires or nanotube stiffness. The method also enables the determination of the boundary conditions of the nanobeam on the membrane. The tensile elastic modulus is then simply determined using the classical theory of beam deflection. The obtained results for the larger nanostructures fairly agree to the values reported in the literature for the macroscopic elastic modulus of the corresponding materials. The measured modulus of the nanomaterials with smaller diameters is significantly higher than that of the larger ones. The increase of the apparent elastic modulus for the smaller diameters is attributed to the surface tension effects. It is thus demonstrated that resonant C-AFM enables the measurement of the elastic modulus and of the surface tension of nanomaterials.

Mechanical modeling and characteristic study for the adhesive contact of elastic layered media

NASA Astrophysics Data System (ADS)

Zhang, Yuyan; Wang, Xiaoli; Tu, Qiaoan; Sun, Jianjun; Ma, Chenbo

2017-11-01

This paper investigates the adhesive contact between a smooth rigid sphere and a smooth elastic layered medium with different layer thicknesses, layer-to-substrate elastic modulus ratios and adhesion energy ratios. A numerical model is established by combining elastic responses of the contact system and an equation of equivalent adhesive contact pressure which is derived based on the Hamaker summation method and the Lennard-Jones intermolecular potential law. Simulation results for hard layer cases demonstrate that variation trends of the pull-off force with the layer thickness and elastic modulus ratio are complex. On one hand, when the elastic modulus ratio increases, the pull-off force decreases at smaller layer thicknesses, decreases at first and then increases at middle layer thicknesses, while increases monotonously at larger layer thicknesses. On the other hand, the pull-off force decreases at first and then increases with the increase in the layer thickness. Furthermore, a critical layer thickness above which the introduction of hard layer cannot reduce adhesion and an optimum layer thickness under which the pull-off force reaches a minimum are found. Both the critical and optimum layer thicknesses become larger with an increase in the Tabor parameter, while they tend to decrease with the increase in the elastic modulus ratio. In addition, the pull-off force increases sublinearly with the adhesion energy ratio if the layer thickness and elastic modulus ratio are fixed.

Quantitative estimation of muscle shear elastic modulus of the upper trapezius with supersonic shear imaging during arm positioning.

PubMed

Leong, Hio-Teng; Ng, Gabriel Yin-Fat; Leung, Vivian Yee-Fong; Fu, Siu Ngor

2013-01-01

Pain and tenderness of the upper trapezius are the major complaints among people with chronic neck and shoulder disorders. Hyper-activation and increased muscle tension of the upper trapezius during arm elevation will cause imbalance of the scapular muscle force and contribute to neck and shoulder disorders. Assessing the elasticity of the upper trapezius in different arm positions is therefore important for identifying people at risk so as to give preventive programmes or for monitoring the effectiveness of the intervention programmes for these disorders. This study aimed to establish the reliability of supersonic shear imaging (SSI) in quantifying upper trapezius elasticity/shear elastic modulus and its ability to measure the modulation of muscle elasticity during arm elevation. Twenty-eight healthy adults (15 males, 13 females; mean age = 29.6 years) were recruited to participate in the study. In each participant, the shear elastic modulus of the upper trapezius while the arm was at rest and at 30° abduction was measured by two operators and twice by operator 1 with a time interval between the measurements. The results showed excellent within- and between-session intra-operator (ICC = 0.87-0.97) and inter-observer (ICC = 0.78-0.83) reliability for the upper trapezius elasticity with the arm at rest and at 30° abduction. An increase of 55.23% of shear elastic modulus from resting to 30° abduction was observed. Our findings demonstrate the possibilities for using SSI to quantify muscle elasticity and its potential role in delineating the modulation of upper trapezius elasticity, which is essential for future studies to compare the differences in shear elastic modulus between normal elasticity and that of individuals with neck and shoulder disorders.

Quantitative Estimation of Muscle Shear Elastic Modulus of the Upper Trapezius with Supersonic Shear Imaging during Arm Positioning

PubMed Central

Leong, Hio-Teng; Ng, Gabriel Yin-fat; Leung, Vivian Yee-fong; Fu, Siu Ngor

2013-01-01

Pain and tenderness of the upper trapezius are the major complaints among people with chronic neck and shoulder disorders. Hyper-activation and increased muscle tension of the upper trapezius during arm elevation will cause imbalance of the scapular muscle force and contribute to neck and shoulder disorders. Assessing the elasticity of the upper trapezius in different arm positions is therefore important for identifying people at risk so as to give preventive programmes or for monitoring the effectiveness of the intervention programmes for these disorders. This study aimed to establish the reliability of supersonic shear imaging (SSI) in quantifying upper trapezius elasticity/shear elastic modulus and its ability to measure the modulation of muscle elasticity during arm elevation. Twenty-eight healthy adults (15 males, 13 females; mean age = 29.6 years) were recruited to participate in the study. In each participant, the shear elastic modulus of the upper trapezius while the arm was at rest and at 30° abduction was measured by two operators and twice by operator 1 with a time interval between the measurements. The results showed excellent within- and between-session intra-operator (ICC = 0.87–0.97) and inter-observer (ICC = 0.78–0.83) reliability for the upper trapezius elasticity with the arm at rest and at 30° abduction. An increase of 55.23% of shear elastic modulus from resting to 30° abduction was observed. Our findings demonstrate the possibilities for using SSI to quantify muscle elasticity and its potential role in delineating the modulation of upper trapezius elasticity, which is essential for future studies to compare the differences in shear elastic modulus between normal elasticity and that of individuals with neck and shoulder disorders. PMID:23825641

Random field assessment of nanoscopic inhomogeneity of bone.

PubMed

Dong, X Neil; Luo, Qing; Sparkman, Daniel M; Millwater, Harry R; Wang, Xiaodu

2010-12-01

Bone quality is significantly correlated with the inhomogeneous distribution of material and ultrastructural properties (e.g., modulus and mineralization) of the tissue. Current techniques for quantifying inhomogeneity consist of descriptive statistics such as mean, standard deviation and coefficient of variation. However, these parameters do not describe the spatial variations of bone properties. The objective of this study was to develop a novel statistical method to characterize and quantitatively describe the spatial variation of bone properties at ultrastructural levels. To do so, a random field defined by an exponential covariance function was used to represent the spatial uncertainty of elastic modulus by delineating the correlation of the modulus at different locations in bone lamellae. The correlation length, a characteristic parameter of the covariance function, was employed to estimate the fluctuation of the elastic modulus in the random field. Using this approach, two distribution maps of the elastic modulus within bone lamellae were generated using simulation and compared with those obtained experimentally by a combination of atomic force microscopy and nanoindentation techniques. The simulation-generated maps of elastic modulus were in close agreement with the experimental ones, thus validating the random field approach in defining the inhomogeneity of elastic modulus in lamellae of bone. Indeed, generation of such random fields will facilitate multi-scale modeling of bone in more pragmatic details. Copyright © 2010 Elsevier Inc. All rights reserved.

Correlation between macro- and nano-scopic measurements of carbon nanostructured paper elastic modulus

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

Omar, Yamila M.; Al Ghaferi, Amal, E-mail: aalghaferi@masdar.ac.ae, E-mail: mchiesa@masdar.ac.ae; Chiesa, Matteo, E-mail: aalghaferi@masdar.ac.ae, E-mail: mchiesa@masdar.ac.ae

2015-07-20

Extensive work has been done in order to determine the bulk elastic modulus of isotropic samples from force curves acquired with atomic force microscopy. However, new challenges are encountered given the development of new materials constructed of one-dimensional anisotropic building blocks, such as carbon nanostructured paper. In the present work, we establish a reliable framework to correlate the elastic modulus values obtained by amplitude modulation atomic force microscope force curves, a nanoscopic technique, with that determined by traditional macroscopic tensile testing. In order to do so, several techniques involving image processing, statistical analysis, and simulations are used to find themore » appropriate path to understand how macroscopic properties arise from anisotropic nanoscale components, and ultimately, being able to calculate the value of bulk elastic modulus.« less

A Finite Element Model to Predict the Effect of Porosity on Elastic Modulus in Low-Porosity Materials

NASA Astrophysics Data System (ADS)

Morrissey, Liam S.; Nakhla, Sam

2018-07-01

The effect of porosity on elastic modulus in low-porosity materials is investigated. First, several models used to predict the reduction in elastic modulus due to porosity are compared with a compilation of experimental data to determine their ranges of validity and accuracy. The overlapping solid spheres model is found to be most accurate with the experimental data and valid between 3 and 10 pct porosity. Next, a FEM is developed with the objective of demonstrating that a macroscale plate with a center hole can be used to model the effect of microscale porosity on elastic modulus. The FEM agrees best with the overlapping solid spheres model and shows higher accuracy with experimental data than the overlapping solid spheres model.

Measurement of the temperature dependence of Young's modulus of cartilage by phase-sensitive optical coherence elastography

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

Liu, C H; Li, J; Singh, M

2014-08-31

The development of an effective system to monitor the changes in the elastic properties of cartilage tissue with increasing temperature in laser reconstruction is an urgent practical task. In this paper, the use of phase-sensitive optical coherence elastography for detection of elastic waves in the sample has allowed Young's modulus of cartilage tissue to be measured directly during heating. Young's modulus was calculated from the group velocity of propagation of elastic waves excited by means of a system supplying focused air pulses. The measurement results are in agreement with the results of measurements of the modulus of elasticity under mechanicalmore » compression. The technique developed allows for noninvasive measurements; its development is promising for the use in vivo. (laser biophotonics)« less

Acoustic evaluation of loblolly pine tree- and lumber-length logs allows for segregation of lumber modulus of elasticity, not for modulus of rupture

Treesearch

Mark Alexander Butler; Joseph Dahlen; Thomas L. Eberhardt; Cristian Montes; Finto Antony; Richard F. Daniels

2017-01-01

Key message Loblolly pine (Pinus taeda) logs can be evaluated using acoustic velocity whereby threshold acoustic velocity values can be set to ensure lumber meets specified mechanical property design values for modulus of elasticity. Context...

Earlywood and latewood elastic properties in loblolly pine

Treesearch

Steven Cramer; David Kretschmann; Roderic Lakes; Troy Schmidt

2005-01-01

The elastic properties of earlywood and latewood and their variability were measured in 388 specimens from six loblolly pine trees in a commercial plantation. Properties measured included longitudinal modulus of elasticity, shear modulus, specific gravity, microfibril angle and presence of compression wood. Novel testing procedures were developed to measure properties...

Measurement of the elastic modulus of a multi-wall boron nitride nanotube

NASA Astrophysics Data System (ADS)

Chopra, Nasreen G.; Zettl, A.

1998-02-01

We have experimentally determined the elastic properties of an individual multi-wall boron nitride (BN) nanotube. From the thermal vibration amplitude of a cantilevered BN nanotube observed in a transmission electron microscope, we find the axial Young's modulus to be 1.22 ± 0.24 TPa, a value consistent with theoretical estimates. The observed Young's modulus exceeds that of all other known insulating fibers. Our elasticity results confirm that BN nanotubes are highly crystalline with very few defects.

Cálculo del esfuerzo ideal de metales nobles mediante primeros principios en la dirección <100>

NASA Astrophysics Data System (ADS)

Bautista-Hernández, A.; López-Fuentes, M.; Pacheco-Espejel, V.; Rivas-Silva, J. F.

2005-04-01

We present calculations of the ideal strength on the < 100 > direction for noble metals (Cu, Ag and Au), by means of first principles calculations. First, we obtain the structural parameters (cell parameters, bulk modulus) for each studied metal. We deform on the < 100 > direction calculating the total energy and the stress tensor through the Hellman-Feynman theorem, by the relaxation of the unit cell in the perpendicular directions to the deformation one. The calculated cell constants differ 1.3 % from experimental data. The maximum ideal strength are 29.6, 17 and 19 GPa for Cu, Ag and Au respectively. Meanwhile, the calculated elastic modulus are 106 (Cu), 71 (Ag), and 45 GPa (Au) and are in agreement with the experimental values for polycrystalline samples. The values of maximum strength are explained by the optimum volume values due to the atomic radius size for each element.

Variations in local elastic modulus along the length of the aorta as observed by use of a scanning haptic microscope (SHM).

PubMed

Moriwaki, Takeshi; Oie, Tomonori; Takamizawa, Keiichi; Murayama, Yoshinobu; Fukuda, Toru; Omata, Sadao; Kanda, Keiichi; Nakayama, Yasuhide

2011-12-01

Variations in microscopic elastic structures along the entire length of canine aorta were evaluated by use of a scanning haptic microscope (SHM). The total aorta from the aortic arch to the abdominal aorta was divided into 6 approximately equal segments. After embedding the aorta in agar, it was cut into horizontal circumferential segments to obtain disk-like agar portions containing ring-like samples of aorta with flat surfaces (thickness, approximately 1 mm). The elastic modulus and topography of the samples under no-load conditions were simultaneously measured along the entire thickness of the wall by SHM by using a probe with a diameter of 5 μm and a spatial resolution of 2 μm at a rate of 0.3 s/point. The elastic modulus of the wall was the highest on the side of the luminal surface and decreased gradually toward the adventitial side. This tendency was similar to that of the change in the elastin fiber content. During the evaluation of the mid-portion of each tunica media segment, the highest elastic modulus (40.8 ± 3.5 kPa) was identified at the thoracic section of the aorta that had the highest density of elastic fibers. Under no-load conditions, portions of the aorta with high elastin density have a high elastic modulus.

Damage of the Interface Between an Orthodontic Bracket and Enamel - the Effect of Some Elastic Properties of the Adhesive Material

NASA Astrophysics Data System (ADS)

Durgesh, B. H.; Alkheraif, A. A.; Al Sharawy, M.; Varrela, J.; Vallittu, P. K.

2016-01-01

The aim of this study was to investigate the magnitude of debonding stress of an orthodontic bracket bonded to the enamel with resin systems having different elastic properties. For the same purpose, sixty human premolars were randomly divided into four groups according to the adhesive system used for bonding brackets: G Fix flowable resin (GFI) with Everstick NET (ESN), GFI, G Aenial Universal Flow (GAU) with ESN, and GAU. The brackets were stressed in the occlusogingival direction on a universal testing machine. The values of debonding load and displacement were determined at the point of debonding. The elastic modulus of the tested materials was determined using nanoindentation. An analysis of variance showed a significant difference in the loads required to debond the bracket among the groups tested. The GAU group had the highest elastic modulus, followed by the GFI and ESN groups. ARI (Adhesive Remnant Index) scores demonstrated more remnants of the adhesive material on the bracket surface with adhesives having a higher elastic modulus. Taking into consideration results of the present in-vitro study, it can be concluded that the incorporation of a glass-fiber-reinforced composite resin (FRC) with a low elastic modulus between the orthodontic bracket and enamel increases the debonding force and strain more than with adhesive systems having a higher elastic modulus.

The influence of low temperatures on dynamic mechanical properties of animal bone

NASA Astrophysics Data System (ADS)

Mardas, Marcin; Kubisz, Leszek; Mielcarek, Slawomir; Biskupski, Piotr

2009-01-01

Different preservation methods are currently used in bone banks, even though their effects on allograft quality are not fully understood. Freezing is one of the most popular methods of preservation in tissue banking. Yet, there is not a lot of data on dynamic mechanical properties of frozen bone. Material used in this study was femoral bones from adult bovine that were machine cut and frozen to the temperature 140°C. Both elastic modulus and loss modulus were measured at 1, 3, 5, 10, and 20 Hz in the temperature range of 30-200°C. Differences between frozen and control samples were observed. The frequency increase always led to the increase in elastic modulus values and decrease in loss modulus values. Freezing reduced the elastic modulus values of about 25% and the loss modulus values of about 45% when measured at 20°C.

Comparison of the wear and flexural characteristics of flowable resin composites for posterior lesions.

PubMed

Sumino, Natsu; Tsubota, Keishi; Takamizawa, Toshiki; Shiratsuchi, Koji; Miyazaki, Masashi; Latta, Mark A

2013-01-01

To determine the localized wear and flexural properties of flowable resin composites for posterior lesions compared with universal resin composites produced by the same manufacturers. Ten specimens of each of three flowable resins, G-ænial Universal Flo, G-ænial Flo and Clearfil Majesty Flow, and the corresponding resin composite materials, Kalore and Clearfil Majesty Esthetics, were prepared in custom fixtures and subjected to 400,000 wear machine cycles to simulate localized wear. The total maximum depth and volume loss of the wear facets was calculated for each specimen using a profilometer. A three-point bending test was performed to determine the flexural strength, modulus of elasticity and resilience. Values were statistically compared using one-way analysis of variance (ANOVA) followed by Tukey's Honestly Significant Difference (HSD) test. The wear depth ranged from 58.3-126.9 m and the volumetric loss ranged from 0.019-0.049 mm(3), with significant differences observed between restorative materials. The wear depth of G-ænial Universal Flo was significantly smaller than those of the other resin composites tested. The flexural strengths and elastic modulus ranged from 90.5-135.1 MPa and from 4.7-7.6 GPa, respectively. A significantly greater flexural strength and higher elastic modulus was found for G-ænial Universal Flo than the other composites. The wear and mechanical properties of the flowable resin composites tested suggested improved performance compared with universal resin composites.

Elastic modulus affects the growth and differentiation of neural stem cells

PubMed Central

Jiang, Xian-feng; Yang, Kai; Yang, Xiao-qing; Liu, Ying-fu; Cheng, Yuan-chi; Chen, Xu-yi; Tu, Yue

2015-01-01

It remains poorly understood if carrier hardness, elastic modulus, and contact area affect neural stem cell growth and differentiation. Tensile tests show that the elastic moduli of Tiansu and SMI silicone membranes are lower than that of an ordinary dish, while the elastic modulus of SMI silicone membrane is lower than that of Tiansu silicone membrane. Neural stem cells from the cerebral cortex of embryonic day 16 Sprague-Dawley rats were seeded onto ordinary dishes as well as Tiansu silicone membrane and SMI silicone membrane. Light microscopy showed that neural stem cells on all three carriers show improved adherence. After 7 days of differentiation, neuron specific enolase, glial fibrillary acidic protein, and myelin basic protein expression was detected by immunofluorescence. Moreover, flow cytometry revealed a higher rate of neural stem cell differentiation into astrocytes on Tiansu and SMI silicone membranes than on the ordinary dish, which was also higher on the SMI than the Tiansu silicone membrane. These findings confirm that all three cell carrier types have good biocompatibility, while SMI and Tiansu silicone membranes exhibit good mechanical homogenization. Thus, elastic modulus affects neural stem cell differentiation into various nerve cells. Within a certain range, a smaller elastic modulus results in a more obvious trend of cell differentiation into astrocytes. PMID:26604916

Theoretical investigations on structural, elastic and electronic properties of thallium halides

NASA Astrophysics Data System (ADS)

Singh, Rishi Pal; Singh, Rajendra Kumar; Rajagopalan, Mathrubutham

2011-04-01

Theoretical investigations on structural, elastic and electronic properties, viz. ground state lattice parameter, elastic moduli and density of states, of thallium halides (viz. TlCl and TlBr) have been made using the full potential linearized augmented plane wave method within the generalized gradient approximation (GGA). The ground state lattice parameter and bulk modulus and its pressure derivative have been obtained using optimization method. Young's modulus, shear modulus, Poisson ratio, sound velocities for longitudinal and shear waves, Debye average velocity, Debye temperature and Grüneisen parameter have also been calculated for these compounds. Calculated structural, elastic and other parameters are in good agreement with the available data.

In situ elasticity modulation with dynamic substrates to direct cell phenotype

PubMed Central

Kloxin, April M.; Benton, Julie A.; Anseth, Kristi S.

2009-01-01

Microenvironment elasticity influences critical cell functions such as differentiation, cytoskeletal organization, and process extension. Unfortunately, few materials allow elasticity modulation in real-time to probe its direct effect on these dynamic cellular processes. Here, a new approach is presented for the photochemical modulation of elasticity within the cell's microenvironment at any point in time. A photodegradable hydrogel was irradiated and degraded under cytocompatible conditions to generate a wide range of elastic moduli similar to soft tissues and characterized using rheometry and atomic force microscopy (AFM). The effect of the elastic modulus on valvular interstitial cell (VIC) activation into myofibroblasts was explored. In these studies, gradient samples were used to identify moduli that either promote or suppress VIC myofibroblastic activation. With this knowledge, VICs were cultured on a high modulus, activating hydrogel substrate, and uniquely, results show that decreasing the substrate modulus with irradiation reverses this activation, demonstrating that myofibroblasts can be de-activated solely by changing the modulus of the underlying substrate. This finding is important for the rational design of biomaterials for tissue regeneration and offers insight into fibrotic disease progression. These photodegradable hydrogels demonstrate the capability to both probe and direct cell function through dynamic changes in substrate elasticity. PMID:19788947

Pulsatile flow of non-Newtonian blood fluid inside stenosed arteries: Investigating the effects of viscoelastic and elastic walls, arteriosclerosis, and polycythemia diseases.

PubMed

Nejad, A Abbas; Talebi, Z; Cheraghali, D; Shahbani-Zahiri, A; Norouzi, M

2018-02-01

In this study, the interaction of pulsatile blood flow with the viscoelastic walls of the axisymmetric artery is numerically investigated for different severities of stenosis. The geometry of artery is modeled by an axisymmetric cylindrical tube with a symmetric stenosis in a two-dimensional case. The effects of stenosis severity on the axial velocity profile, pressure distribution, streamlines, wall shear stress, and wall radial displacement for the viscoelastic artery are also compared to the elastics artery. Furthermore, the effects of atherosclerosis and polycythemia diseases on the hemodynamics and the mechanical behavior of arterial walls are investigated. The pulsatile flow of non-Newtonian blood is simulated inside the viscoelastic artery using the COMSOL Multiphysics software (version 5) and by employing the fluid-structure interaction (FSI) method and the arbitrary Lagrangian-Eulerian (ALE) method. Moreover, finite element method (FEM) is used to solve the governing equations on the unstructured grids. For modeling the non-Newtonian blood fluid and the viscoelastic arterial wall, the modified Casson model, and generalized Maxwell model are used, respectively. According to the results, with stenosis severity increasing from 25% to 75% at the time of maximum volumetric flow rate, the maximum value of axial velocity and its gradient increase 7.9 and 19.6 times, and the maximum wall shear stress of viscoelastic wall increases 24.2 times in the constriction zone. With the progression of the atherosclerosis disease (fivefold growth of arterial elastic modulus), the wall radial displacement of viscoelastic arterial walls decreases nearly 40%. In this study, axial velocity profile, pressure distribution, streamlines, wall radial displacement, and wall shear stress were examined for different percentages of stenosis (25%, 50%, and 75%). The atherosclerosis disease was investigated by the fivefold growth of viscoelastic arterial elastic modulus and polycythemia disease was examined by the 21-fold increase in the yield stress of the blood fluid. Furthermore, the comparison of results between the elastic and viscoelastic arterial walls shows that the wall radial displacement for viscoelastic artery is lower than that for the elastic artery as much as 21.7% for the severe stenosis of 75%. Copyright © 2017 Elsevier B.V. All rights reserved.

Fabrication and mechanical characterization of a polyvinyl alcohol sponge for tissue engineering applications.

PubMed

Karimi, A; Navidbakhsh, M; Faghihi, S

2014-05-01

Polyvinyl alcohol (PVA) sponges are widely used for clinical applications, including ophthalmic surgical treatments, wound healing and tissue engineering. There is, however, a lack of sufficient data on the mechanical properties of PVA sponges. In this study, a biomechanical method is used to characterize the elastic modulus, maximum stress and strain as well as the swelling ratio of a fabricated PVA sponge (P-sponge) and it is compared with two commercially available PVA sponges (CENEFOM and EYETEC). The results indicate that the elastic modulus of the P-sponge is 5.32% and 13.45% lower than that of the CENEFOM and EYETEC sponges, while it bears 4.11% more and 10.37% less stress compared to the CENEFOM and EYETEC sponges, respectively. The P-sponge shows a maximum strain of 32% more than the EYETEC sponge as well as a 26.78% higher swelling ratio, which is a significantly higher absorbency compared to the CENEFOM. It is believed that the results of this study would help for a better understanding of the extension, rupture and swelling mechanism of PVA sponges, which could lead to crucial improvement in the design and application of PVA-based materials in ophthalmic and plastic surgeries as well as wound healing and tissue engineering.

Regional variation in wood modulus of elasticity (stiffness) and modulus of rupture (strength) of planted loblolly pine in the United States

Treesearch

Antony Finto; Lewis Jordan; Laurence R. Schimleck; Alexander Clark; Ray A. Souter; Richard F. Daniels

2011-01-01

Modulus of elasticity (MOE), modulus of rupture (MOR), and specific gravity (SG) are important properties for determining the end-use and value of a piece of lumber. This study addressed the variation in MOE, MOR, and SG with physiographic region, tree height, and wood type. Properties were measured from two static bending samples (dimensions 25.4 mm × 25.4 mm × 406.4...

Coagulation monitoring based on blood elastic measurement using optical coherence tomography

NASA Astrophysics Data System (ADS)

Xu, Xiangqun; Zhu, Jiang; Chen, Zhongping

2017-02-01

Blood coagulation monitoring is important to diagnose hematological diseases and cardiovascular diseases and to predict the risk of bleeding and excessive clotting. In this study, we developed a system to dynamically monitor blood coagulation and quantitatively determine the coagulation function by blood elastic measurement. When blood forms a clot from a liquid, ultrasonic force induces a shear wave, which is detected by optical coherence tomography (OCT). The coagulation of porcine whole blood recalcified by calcium chloride is assessed using the metrics of reaction time, clot formation kinetics and maximum shear modulus. The OCE system can noninvasively monitor the blood coagulation and quantitatively determine the coagulation function.

Preparation and mechanical characterization of a PNIPA hydrogel composite.

PubMed

Liu, Kaifeng; Ovaert, Timothy C; Mason, James J

2008-04-01

A poly (N-isopropylacrylamide) (PNIPA) hydrogel was synthesized by free radical polymerization and reinforced with a polyurethane foam to make a hydrogel composite. The temperature dependence of the elastic modulus of the PNIPA hydrogel and the composite due to volume phase transition was found using a uniaxial compression test, and the swelling property was investigated using an equilibrium swelling ratio experiment. The gel composite preserves the ability to undergo the volume phase transition and its elastic modulus has strong temperature dependence. The temperature dependence of the elastic modulus and swelling ratio of the gel composite were compared to the PNIPA hydrogel. Not surprisingly, the modulus and swelling ratio of the composite were less dramatic than in the gel.

Nanoindentation mapping of a wood-adhesive bond

NASA Astrophysics Data System (ADS)

Konnerth, J.; Valla, A.; Gindl, W.

2007-08-01

A mapping experiment of a wood phenol-resorcinol-formaldehyde adhesive bond was performed by means of grid nanoindentation. The variability of the modulus of elasticity and the hardness was evaluated for an area of 17 μm by 90 μm. Overall, the modulus of elasticity of the adhesive was clearly lower than the modulus of wood cell walls, whereas the hardness of the adhesive was slightly higher compared to cell walls. A very slight trend of decreasing modulus of elasticity was found with increasing distance from the immediate bond line. However, the trend was superimposed by a high variability of the modulus of elasticity in dependence on the position in the wood cell wall. The unexpectedly high variation of the modulus between 12 and 24 GPa may be explained by the interaction between the helical orientation of the cellulose microfibrils in the S2 layer of the wood cell wall and the geometry of the three-sided Berkovich type indenter pyramid used. Corresponding to the very slight decrease in modulus with increasing distance from the bond line, a similar but clearer trend was found for hardness. Both trends of changing mechanical properties of wood cell walls with varying distance from the bond line are attributed to effects of adhesive penetration into the wood cell wall.

Effects of ion irradiation on the surface mechanical behavior of hybrid sol-gel derived silicate thin films

NASA Astrophysics Data System (ADS)

Ghisleni, Rudy

A study on the effects of ion irradiation on the surface mechanical behavior of hybrid sol-gel derived thin films has been performed. Hybrid organic/inorganic modified silicate thin films were synthesized by sol-gel processing from tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) precursors and spin-coated onto (100) Si substrates. The synthesized films were investigated by nanoindentation, photoluminescence spectroscopy, and Raman spectroscopy. Hybrid TEOS/MTES sol-gel films modified by ion irradiation with deposited electronic energies of 1.87 x 1025 eV/cm3 or higher showed higher values of reduced elastic modulus and hardness than 800°C heat treated films. Thus, ion irradiation was found to be an effective means in converting the polymer sol into ceramic type coatings. The ions used in this study were Cu2+, N2+, Si+, O+, N+, He+, and H+, with incident energies ranging from 100 keV to 2 MeV, and fluences ranging from 1 x 1014 to 1 x 1017 ions/cm2. Both the reduced elastic modulus and hardness were seen to increase monotonically with the increase in ion fluence, with an observed maximum hardness of 7.7 GPa (an unirradiated film hardness was 0.4 GPa) and a maximum reduced elastic modulus of 84.0 GPa (an unirradiated film reduced elastic modulus was 7.1 GPa) for 250 keV N2+ irradiation with a 5 x 1016 ions/cm2 fluence. The electronic stopping power was found to be principally responsible for the film hardening, while the role of nuclear stopping power was minimal. A monotonic increase in hardness with increase in electronic energy deposited to the film surface was found. A model describing the hardening of ion irradiated films was developed. This model characterizes the hardening effectiveness of the ion species considered by two parameters: the constant hardening cross-section and the hardening coefficient. Where the hardening cross-section represents the cross-sectional area hardened by the interaction of an incident ion with the target, and the hardening coefficient represents an index of the cross-sectional area gradient as a function of fluence. The increase in hardness of hybrid sol-gel films following ion irradiation was linked to structural changes. Ion irradiation results in a cross-linked silica film as well as the segregation of amorphous carbon clusters, both of which contributed to increase the mechanical properties of the films.

A traveling wave ultrasonic motor with a metal/polymer-matrix material compound stator

NASA Astrophysics Data System (ADS)

Li, Jinbang; Liu, Shuo; Zhou, Ningning; Yu, Aibing; Cui, Yuguo; Chen, Pengfei

2018-01-01

This study proposes a traveling wave ultrasonic motor with a metal/polymer-matrix material compound stator. The stator is composed of a metal ring and polymer-matrix teeth. The resonance frequency of the stator with different structural dimensions was analyzed by the finite element method. From the results, the structure parameters of the metal ring were obtained. The effects of the density and elastic modulus of the tooth material on the resonance frequency were also investigated. A viscoelastic contact model was built to explore the contact state between the compound stator and rotor. Considering the density, elastic modulus and tribological properties, the tooth material was prepared by a molding process. The load-torque and efficiency-torque characteristics of the motor with different tooth thicknesses were measured under different preloads using a preload controlled ultrasonic motor test device. The maximum no-load speed of the motor was about 85 r min-1 with a tooth thickness of 3 mm and a preload of 100 N, the maximum stall torque of the motor was about 0.5 N · m with a tooth thickness of 4 mm and a preload of 125 N, and a maximum efficiency of about 5.5% occurred with a tooth thickness of 4 mm, a preload of 100 N and a torque of 0.3 N · m. The main merits of the proposed ultrasonic motor are low cost, light weight, high processing efficiency and long life.

Influence of nanomechanical crystal properties on the comminution process of particulate solids in spiral jet mills.

PubMed

Zügner, Sascha; Marquardt, Karin; Zimmermann, Ingfried

2006-02-01

Elastic-plastic properties of single crystals are supposed to influence the size reduction process of bulk materials during jet milling. According to Pahl [M.H. Pahl, Zerkleinerungstechnik 2. Auflage. Fachbuchverlag, Leipzig (1993)] and H. Rumpf: [Prinzipien der Prallzerkleinerung und ihre Anwendung bei der Strahlmahlung. Chem. Ing. Tech., 3(1960) 129-135.] fracture toughness, maximum strain or work of fracture for example are strongly dependent on mechanical parameters like hardness (H) and young's modulus of elasticity (E). In addition the dwell time of particles in a spiral jet mill proved to correlate with the hardness of the feed material [F. Rief: Ph. D. Thesis, University of Würzburg (2001)]. Therefore 'near-surface' properties have a direct influence on the effectiveness of the comminution process. The mean particle diameter as well as the size distribution of the ground product may vary significantly with the nanomechanical response of the material. Thus accurate measurement of crystals' hardness and modulus is essential to determine the ideal operational micronisation conditions of the spiral jet mill. The recently developed nanoindentation technique is applied to examine subsurface properties of pharmaceutical bulk materials, namely calcite, sodium ascorbate, lactose and sodium chloride. Pressing a small sized tip into the material while continuously recording load and displacement, characteristic diagrams are derived. The mathematical evaluation of the force-displacement-data allows for calculation of the hardness and the elastic modulus of the investigated material at penetration depths between 50-300 nm. Grinding experiments performed with a modified spiral jet mill (Type Fryma JMRS 80) indicate the strong impact of the elastic-plastic properties of a given substance on its breaking behaviour. The fineness of milled products produced at constant grinding conditions but with different crystalline powders varies significantly as it is dependent on the nanohardness and the elasticity of the feed material. The analysis of this correlation gives new insights into the size reduction process.

First-principles investigations on structural, elastic, electronic properties and Debye temperature of orthorhombic Ni3Ta under pressure

NASA Astrophysics Data System (ADS)

Li, Pan; Zhang, Jianxin; Ma, Shiyu; Jin, Huixin; Zhang, Youjian; Zhang, Wenyang

2018-06-01

The structural, elastic, electronic properties and Debye temperature of Ni3Ta under different pressures are investigated using the first-principles method based on density functional theory. Our calculated equilibrium lattice parameters at 0 GPa well agree with the experimental and previous theoretical results. The calculated negative formation enthalpies and elastic constants both indicate that Ni3Ta is stable under different pressures. The bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν are calculated by the Voigt-Reuss-Hill method. The bigger ratio of B/G indicates Ni3Ta is ductile and the pressure can improve the ductility of Ni3Ta. In addition, the results of density of states and the charge density difference show that the stability of Ni3Ta is improved by the increasing pressure. The Debye temperature ΘD calculated from elastic modulus increases along with the pressure.

Linear analysis using secants for materials with temperature dependent nonlinear elastic modulus and thermal expansion properties

NASA Astrophysics Data System (ADS)

Pepi, John W.

2017-08-01

Thermally induced stress is readily calculated for linear elastic material properties using Hooke's law in which, for situations where expansion is constrained, stress is proportional to the product of the material elastic modulus and its thermal strain. When material behavior is nonlinear, one needs to make use of nonlinear theory. However, we can avoid that complexity in some situations. For situations in which both elastic modulus and coefficient of thermal expansion vary with temperature, solutions can be formulated using secant properties. A theoretical approach is thus presented to calculate stresses for nonlinear, neo-Hookean, materials. This is important for high acuity optical systems undergoing large temperature extremes.

High elastic modulus nanopowder reinforced resin composites for dental applications

NASA Astrophysics Data System (ADS)

Wang, Yijun

2007-12-01

Dental restorations account for more than $3 billion dollars a year on the market. Among them, all-ceramic dental crowns draw more and more attention and their popularity has risen because of their superior aesthetics and biocompatibility. However, their relatively high failure rate and labor-intensive fabrication procedure still limit their application. In this thesis, a new family of high elastic modulus nanopowder reinforced resin composites and their mechanical properties are studied. Materials with higher elastic modulus, such as alumina and diamond, are used to replace the routine filler material, silica, in dental resin composites to achieve the desired properties. This class of composites is developed to serve (1) as a high stiffness support to all-ceramic crowns and (2) as a means of joining independently fabricated crown core and veneer layers. Most of the work focuses on nano-sized Al2O3 (average particle size 47 nm) reinforcement in a polymeric matrix with 50:50 Bisphenol A glycidyl methacrylate (Bis-GMA): triethylene glycol dimethacrylate (TEGDMA) monomers. Surfactants, silanizing agents and primers are examined to obtain higher filler levels and enhance the bonding between filler and matrix. Silane agents work best. The elastic modulus of a 57.5 vol% alumina/resin composite is 31.5 GPa compared to current commercial resin composites with elastic modulus <15 GPa. Chemical additives can also effectively raise the hardness to as much as 1.34 GPa. Besides>alumina, diamond/resin composites are studied. An elastic modulus of about 45 GPa is obtained for a 57 vol% diamond/resin composite. Our results indicate that with a generally monodispersed nano-sized high modulus filler, relatively high elastic modulus resin-based composite cements are possible. Time-dependent behavior of our resin composites is also investigated. This is valuable for understanding the behavior of our material and possible fatigue testing in the future. Our results indicate that with effective coupling agents and higher filler loading, viscous flow can be greatly decreased due to the attenuation of mobility of polymer chains. Complementary studies indicate that our resin composites are promising for the proposed applications as a stiff support to all-ceramic crowns.

Confinement Effect on Material Properties of RC Beams Under Flexure

NASA Astrophysics Data System (ADS)

Kulkarni, Sumant; Shiyekar, Mukund Ramchandra; Shiyekar, Sandip Mukund

2017-12-01

In structural analysis, especially in indeterminate structures, it becomes essential to know the material and geometrical properties of members. The codal provisions recommend elastic properties of concrete and steel and these are fairly accurate enough. The stress-strain curve for concrete cylinder or a cube specimen is plotted. The slope of this curve is modulus of elasticity of plain concrete. Another method of determining modulus of elasticity of concrete is by flexural test of a beam specimen. The modulus of elasticity most commonly used for concrete is secant modulus. The modulus of elasticity of steel is obtained by performing a tension test of steel bar. While performing analysis by any software for high rise building, cross area of plain concrete is taken into consideration whereas effects of reinforcement bars and concrete confined by stirrups are neglected. Present aim of study is to determine elastic properties of reinforced cement concrete beam. Two important stiffness properties such as AE and EI play important role in analysis of high rise RCC building idealized as plane frame. The experimental program consists of testing of beams (model size 150 × 150 × 700 mm) with percentage of reinforcement varying from 0.54 to 1.63% which commensurate with existing Codal provisions of IS:456-2000 for flexural member. The effect of confinement is considered in this study. The experimental results are verified by using 3D finite element techniques.

Study on axial strength of a channel-shaped pultruded GFRP member

NASA Astrophysics Data System (ADS)

Matsumoto, Yukihiro; Satake, Chito; Nisida, Kenji

2017-10-01

Fiber reinforced polymers (FRP) are widely used in vehicle and aerospace applications because of their lightweight and high-strength characteristics. Additionally, FRPs are increasingly applied to building structures. However, the elastic modulus of glass fiber reinforced polymers (GFRPs) is lower than that of steel. Hence, the evaluating the buckling strength of GFRP members for design purpose is necessary. The buckling strength is determined by Euler buckling mode as well as local buckling. In this study investigated the compressive strength of GFRP members subjected to axial compression through experiments and theoretical calculations. The adopted GFRP member was a channel-shaped GFRP, which was molded via pultrusion, at various lengths. Although, the mechanical properties as longitudinal elastic modulus and fiber volume fraction and strength of GFRP members subjected, to axial can be easily evaluated, evaluating transverse elastic modulus and shear modulus in typical material tests is difficult in standard section. Therefore the composite law was used in this study. As a result, we confirmed that the axial strength of a GFRP member could be calculated by a theoretical evaluation method utilizing longitudinal elastic modulus and fiber volume fraction.

Study of low-modulus biomedical β Ti-Nb-Zr alloys based on single-crystal elastic constants modeling.

PubMed

Wang, Xing; Zhang, Ligang; Guo, Ziyi; Jiang, Yun; Tao, Xiaoma; Liu, Libin

2016-09-01

CALPHAD-type modeling was used to describe the single-crystal elastic constants of the bcc solution phase in the ternary Ti-Nb-Zr system. The parameters in the model were evaluated based on the available experimental data and first-principle calculations. The composition-elastic properties of the full compositions were predicted and the results were in good agreement with the experimental data. It is found that the β phase can be divided into two regions which are separated by a critical dynamical stability composition line. The corresponding valence electron number per atom and the polycrystalline Young׳s modulus of the critical compositions are 4.04-4.17 and 30-40GPa respectively. Orientation dependencies of single-crystal Young׳s modulus show strong elastic anisotropy on the Ti-rich side. Alloys compositions with a Young׳s modulus along the <100> direction matching that of bone were found. The current results present an effective strategy for designing low modulus biomedical alloys using computational modeling. Copyright © 2016 Elsevier Ltd. All rights reserved.

Tuning the Elastic Modulus of Hydrated Collagen Fibrils

PubMed Central

Grant, Colin A.; Brockwell, David J.; Radford, Sheena E.; Thomson, Neil H.

2009-01-01

Abstract Systematic variation of solution conditions reveals that the elastic modulus (E) of individual collagen fibrils can be varied over a range of 2–200 MPa. Nanoindentation of reconstituted bovine Achilles tendon fibrils by atomic force microscopy (AFM) under different aqueous and ethanol environments was carried out. Titration of monovalent salts up to a concentration of 1 M at pH 7 causes E to increase from 2 to 5 MPa. This stiffening effect is more pronounced at lower pH where, at pH 5, e.g., there is an ∼7-fold increase in modulus on addition of 1 M KCl. An even larger increase in modulus, up to ∼200 MPa, can be achieved by using increasing concentrations of ethanol. Taken together, these results indicate that there are a number of intermolecular forces between tropocollagen monomers that govern the elastic response. These include hydration forces and hydrogen bonding, ion pairs, and possibly the hydrophobic effect. Tuning of the relative strengths of these forces allows rational tuning of the elastic modulus of the fibrils. PMID:19948128

Elastic-mathematical theory of cells and mitochondria in swelling process. II. Effect of temperature upon modulus of elasticity of membranous material of egg cells of sea urchin, Strongylocentrotus purpuratus, and of oyster, Crassostrea virginica.

PubMed

Mela, M J

1968-01-01

The elastic behavior of the cell wall as a function of the temperature has been studied with particular attention being given to the swelling of egg cells of Strongylocentrotus purpuratus and Crassostrea virginica in different sea water concentrations at different temperatures. It was found that the modulus of elasticity is a nonlinear function of temperature. At about 12-13 degrees C the modulus of elasticity (E) is constant, independent of the stress (sigma) and strain (epsilon(nu)) which exist at the cell wall; the membranous material follows Hooke's law, and E approximately 3 x 10(7) dyn/cm(2) for S. purpuratus and C. virginica. When the temperature is higher or lower than 12-13 degrees C, the modulus of elasticity increases, and the membranous material does not follow Hooke's law, but is almost directly proportional to the stresses existing at the cell wall. On increasing the stress, the function E(sigma) = E(sigma) approaches saturation. The corresponding stress-strain diagrams, sigma = sigma(epsilon(nu)), and the graphs, E(sigma) = E(sigma) and E(sigma) = E(t) are given. The cyto-elastic phenomena at the membrane are discussed.

Film thickness for different regimes of fluid-film lubrication

NASA Technical Reports Server (NTRS)

Hamrock, B. J.

1980-01-01

Film thickness equations are provided for four fluid-film lubrication regimes found in elliptical contacts. These regimes are isoviscous-rigid; viscous-rigid; elastohydrodynamic lubrication of low-elastic-modulus materials (soft EHL), or isoviscous-elastic; and elastohydrodynamic lubrication of high-elastic-modulus materials (hard EHL), or viscous-elastic. The influence or lack of influence of elastic and viscous effects is the factor that distinguishes these regimes. The results are presented as a map of the lubrication regimes, with film thickness contours on a log-log grid of the viscosity and elasticity for three values of the ellipticity parameter.

Effects of biaxial strains on electronic and elastic properties of hexagonal XSi2 (X = Cr, Mo, W) from first-principles

NASA Astrophysics Data System (ADS)

Zhu, Haiyan; Shi, Liwei; Li, Shuaiqi; Zhang, Shaobo; Xia, Wangsuo

2018-02-01

Structural, electronic properties and elastic anisotropy of hexagonal C40 XSi2 (X = Cr, Mo, W) under equibiaxial in-plane strains are systematically studied using first-principle calculations. The energy gaps show significant changes with biaxial strains, whereas they are always indirect band-gap materials for -6% <ɛxx < 6%. All elastic constants, bulk modulus, shear modulus, Young's modulus increase (decrease) almost linearly with increasing compressive (tensile) strains. The evolutions of BH /GH ratio and Poisson's ratio indicate that these compounds have a better (worse) ductile behaviour under compressive (tensile) strains. A set of 3D plots show a larger directional variability in the Young's modulus E and shear modulus G at different strains for the three compounds, which is consist with the values of anisotropy factors. Moreover, the evolution of Debye temperature and anisotropy of sound velocities with biaxial strains are discussed.

Elastic Modulus Measurement of ORNL ATF FeCrAl Alloys

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

Thompson, Zachary T.; Terrani, Kurt A.; Yamamoto, Yukinori

2015-10-01

Elastic modulus and Poisson’s ratio for a number of wrought FeCrAl alloys, intended for accident tolerant fuel cladding application, are determined via resonant ultrasonic spectroscopy. The results are reported as a function of temperature from room temperature to 850°C. The wrought alloys were in the fully annealed and unirradiated state. The elastic modulus for the wrought FeCrAl alloys is at least twice that of Zr-based alloys over the temperature range of this study. The Poisson’s ratio of the alloys was 0.28 on average and increased very slightly with increasing temperature.

Radiation-damage-induced transitions in zircon: Percolation theory applied to hardness and elastic moduli as a function of density

NASA Astrophysics Data System (ADS)

Beirau, Tobias; Nix, William D.; Ewing, Rodney C.; Pöllmann, Herbert; Salje, Ekhard K. H.

2018-05-01

Two in literature predicted percolation transitions in radiation-damaged zircon (ZrSiO4) were observed experimentally by measurement of the indentation hardness as a function of density and their correlation with the elastic moduli. Percolations occur near 30% and 70% amorphous fractions, where hardness deviates from its linear correlation with the elastic modulus (E), the shear modulus (G) and the bulk modulus (K). The first percolation point pc1 generates a cusp in the hardness versus density evolution, while the second percolation point is seen as a change of slope.

Nanoscale characterization of the biomechanical properties of collagen fibrils in the sclera

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

Papi, M.; Paoletti, P.; Geraghty, B.

We apply the PeakForce Quantitative Nanomechanical Property Mapping (PFQNM) atomic force microscopy mode for the investigation of regional variations in the nanomechanical properties of porcine sclera. We examine variations in the collagen fibril diameter, adhesion, elastic modulus and dissipation in the posterior, equatorial and anterior regions of the sclera. The mean fibril diameter, elastic modulus and dissipation increased from the posterior to the anterior region. Collagen fibril diameter correlated linearly with elastic modulus. Our data matches the known macroscopic mechanical behavior of the sclera. We propose that PFQNM has significant potential in ocular biomechanics and biophysics research.

Relationship between tendon stiffness and failure: a metaanalysis

PubMed Central

LaCroix, Andrew S.; Duenwald-Kuehl, Sarah E.; Lakes, Roderic S.

2013-01-01

Tendon is a highly specialized, hierarchical tissue designed to transfer forces from muscle to bone; complex viscoelastic and anisotropic behaviors have been extensively characterized for specific subsets of tendons. Reported mechanical data consistently show a pseudoelastic, stress-vs.-strain behavior with a linear slope after an initial toe region. Many studies report a linear, elastic modulus, or Young's modulus (hereafter called elastic modulus) and ultimate stress for their tendon specimens. Individually, these studies are unable to provide a broader, interstudy understanding of tendon mechanical behavior. Herein we present a metaanalysis of pooled mechanical data from a representative sample of tendons from different species. These data include healthy tendons and those altered by injury and healing, genetic modification, allograft preparation, mechanical environment, and age. Fifty studies were selected and analyzed. Despite a wide range of mechanical properties between and within species, elastic modulus and ultimate stress are highly correlated (R2 = 0.785), suggesting that tendon failure is highly strain-dependent. Furthermore, this relationship was observed to be predictable over controlled ranges of elastic moduli, as would be typical of any individual species. With the knowledge gained through this metaanalysis, noninvasive tools could measure elastic modulus in vivo and reasonably predict ultimate stress (or structural compromise) for diseased or injured tendon. PMID:23599401

Use of an ultrasonic device for the determination of elastic modulus of dentin.

PubMed

Miyazaki, Masashi; Inage, Hirohiko; Onose, Hideo

2002-03-01

The mechanical properties of dentin substrate are one of the important factors in determining bond strength of dentin bonding systems. The purpose of this study was to determine the elastic modulus of dentin substrate with the use of an ultrasonic device. The dentin disks of about 1 mm thickness were obtaining from freshly extracted human third molars, and the dentin disk was shaped in a rectangular form with a line diamond point. The size and weight of each specimen was measured to calculate the density of the specimen. The ultrasonic equipment employed in this study was composed of a Pulser-Receiver (Model 5900PR, Panametrics), transducers (V155, V156, Panametrics) and an oscilloscope. The measured two-way transit time through the dentin disk was divided by two to account for the down-and-back travel path, and then multiplied by the velocity of sound in the test material. Measuring the longitudinal and share wave sound velocity determine elastic modulus. The mean elastic modulus of horizontally sectioned specimens was 21.8 GPa and 18.5 GPa for the vertically sectioned specimens, and a significant difference was found between the two groups. The ultrasonic method used in this study shows considerable promise for determination of the elastic modulus of the tooth substrate.

Influence of Ce addition on biomedical porous Ti-51 atomic percentage (at. %) Ni shape memory alloy fabricated by microwave sintering

NASA Astrophysics Data System (ADS)

Ibrahim, Mustafa K.; Hamzah, E.; Saud, Safaa N.; Nazim, E. M.; Bahador, A.

2017-12-01

Ti-Ni and Ti-Ni-Ce shape memory alloys (SMAs) were successfully fabricated by microwave sintering. The improvement of the mechanical properties especially the elastic modulus is the most important criterion in this research. The high elastic modulus problems are the most critical issues frequently encountered in hard tissue replacement applications. The effect of Ce addition with four atomic percentages (0 %, 0.19 %, 0.385 % and, 1.165 %) on the microstructure, phase composition, transformation temperatures and mechanical properties was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Differential Scanning Calorimeter (DSC), and compression test. The microstructure shows plates-like with needles-like inside the titanium-rich region. The compression strain was improved, but reduces the compression strength. The addition of cerium improved the properties by reducing the elastic modulus to be very close to the natural human bone, also the microwave sintering gives TiNi SMAs with low elastic modulus comparing with other methods. Based on the results, the 0.385 at. % Ce exhibited a remarkable highest compressive strain and lower elastic modulus compared with the other percentages. In conclusion, the present results indicate that Ti-Ni-Ce SMAs could be a potential alternative to improve Ti-51 at %Ni SMAs for certain biomedical applications.

Fabrication and mechanical characterization of graphene oxide-reinforced poly (acrylic acid)/gelatin composite hydrogels

NASA Astrophysics Data System (ADS)

Faghihi, Shahab; Gheysour, Mahsa; Karimi, Alireza; Salarian, Reza

2014-02-01

Hydrogels have found many practical uses in drug release, wound dressing, and tissue engineering. However, their applications are restricted due to their weak mechanical properties. The role of graphene oxide nanosheets (GONS) as reinforcement agent in poly (acrylic acid) (PAA)/Gelatin (Gel) composite hydrogels is investigated. Composite hydrogels are synthesized by thermal initiated redox polymerization method. Samples are then prepared with 20 and 40 wt. % of PAA, an increasing amount of GONS (0.1, 0.2, and 0.3 wt. %), and a constant amount of Gel. Subsequently, cylindrical hydrogel samples are subjected to a series of compression tests in order to measure their elastic modulus, maximum stress and strain. The results exhibit that the addition of GONS increases the Young's modulus and maximum stress of hydrogels significantly as compared with control (0.0 wt. % GONS). The highest Young's modulus is observed for hydrogel with GO (0.2 wt. %)/PAA (20 wt. %), whereas the highest maximum stress is detected for GO (0.2 wt. %)/PAA (40 wt. %) specimen. The addition of higher amounts of GONS leads to a decrease in the maximum stress of the hydrogel GO (0.3 wt. %)/PAA (40 wt. %). No significant differences are detected for the maximum strain among the hydrogel samples, as the amount of GONS increased. These results suggest that the application of GONS could be used to improve mechanical properties of hydrogel materials. This study may provide an alternative for the fabrication of low-cost graphene/polymer composites with enhanced mechanical properties beneficial for tissue engineering applications.

Endothelial, cardiac muscle and skeletal muscle exhibit different viscous and elastic properties as determined by atomic force microscopy

NASA Technical Reports Server (NTRS)

Mathur, A. B.; Collinsworth, A. M.; Reichert, W. M.; Kraus, W. E.; Truskey, G. A.

2001-01-01

This study evaluated the hypothesis that, due to functional and structural differences, the apparent elastic modulus and viscous behavior of cardiac and skeletal muscle and vascular endothelium would differ. To accurately determine the elastic modulus, the contribution of probe velocity, indentation depth, and the assumed shape of the probe were examined. Hysteresis was observed at high indentation velocities arising from viscous effects. Irreversible deformation was not observed for endothelial cells and hysteresis was negligible below 1 microm/s. For skeletal muscle and cardiac muscle cells, hysteresis was negligible below 0.25 microm/s. Viscous dissipation for endothelial and cardiac muscle cells was higher than for skeletal muscle cells. The calculated elastic modulus was most sensitive to the assumed probe geometry for the first 60 nm of indentation for the three cell types. Modeling the probe as a blunt cone-spherical cap resulted in variation in elastic modulus with indentation depth that was less than that calculated by treating the probe as a conical tip. Substrate contributions were negligible since the elastic modulus reached a steady value for indentations above 60 nm and the probe never indented more than 10% of the cell thickness. Cardiac cells were the stiffest (100.3+/-10.7 kPa), the skeletal muscle cells were intermediate (24.7+/-3.5 kPa), and the endothelial cells were the softest with a range of elastic moduli (1.4+/-0.1 to 6.8+/-0.4 kPa) depending on the location of the cell surface tested. Cardiac and skeletal muscle exhibited nonlinear elastic behavior. These passive mechanical properties are generally consistent with the function of these different cell types.

Finite element investigation of temperature dependence of elastic properties of carbon nanotube reinforced polypropylene

NASA Astrophysics Data System (ADS)

Ahmadi, Masoud; Ansari, Reza; Rouhi, Saeed

2017-11-01

This paper aims to investigate the elastic modulus of the polypropylene matrix reinforced by carbon nanotubes at different temperatures. To this end, the finite element approach is employed. The nanotubes with different volume fractions and aspect ratios (the ratio of length to diameter) are embedded in the polymer matrix. Besides, random and regular algorithms are utilized to disperse carbon nanotubes in the matrix. It is seen that as the pure polypropylene, the elastic modulus of carbon nanotube reinforced polypropylene decreases by increasing the temperature. It is also observed that when the carbon nanotubes are dispersed parallelly and the load is applied along the nanotube directions, the largest improvement in the elastic modulus of the nanotube/polypropylene nanocomposites is obtained.

Elasticity, slowness, thermal conductivity and the anisotropies in the Mn3Cu1-xGexN compounds

NASA Astrophysics Data System (ADS)

Li, Guan-Nan; Chen, Zhi-Qian; Lu, Yu-Ming; Hu, Meng; Jiao, Li-Na; Zhao, Hao-Ting

2018-03-01

We perform the first-principles to systematically investigate the elastic properties, minimum thermal conductivity and anisotropy of the negative thermal expansion compounds Mn3Cu1-xGexN. The elastic constant, bulk modulus, shear modulus, Young’s modulus and Poisson ratio are calculated for all the compounds. The results of the elastic constant indicate that all the compounds are mechanically stable and the doped Ge can adjust the ductile character of the compounds. According to the values of the percent ratio of the elastic anisotropy AB, AE and AG, shear anisotropic factors A1, A2 and A3, all the Mn3Cu1-xGexN compounds are elastic anisotropy. The three-dimensional diagrams of elastic moduli in space also show that all the compounds are elastic anisotropy. In addition, the acoustic wave speed, slowness, minimum thermal conductivity and Debye temperature are also calculated. When the ratio of content for Cu and Ge arrived to 1:1, the compound has the lowest thermal conductivity and the highest Debye temperature.

Extensor indicis proprius tendon transfer using shear wave elastography.

PubMed

Lamouille, J; Müller, C; Aubry, S; Bensamoun, S; Raffoul, W; Durand, S

2017-06-01

The means for judging optimal tension during tendon transfers are approximate and not very quantifiable. The purpose of this study was to demonstrate the feasibility of quantitatively assessing muscular mechanical properties intraoperatively using ultrasound elastography (shear wave elastography [SWE]) during extensor indicis proprius (EIP) transfer. We report two cases of EIP transfer for post-traumatic rupture of the extensor pollicis longus muscle. Ultrasound acquisitions measured the elasticity modulus of the EIP muscle at different stages: rest, active extension, active extension against resistance, EIP section, distal passive traction of the tendon, after tendon transfer at rest and then during active extension. A preliminary analysis was conducted of the distribution of values for this modulus at the various transfer steps. Different shear wave velocity and elasticity modulus values were observed at the various transfer steps. The tension applied during the transfer seemed close to the resting tension if a traditional protocol were followed. The elasticity modulus varied by a factor of 37 between the active extension against resistance step (565.1 kPa) and after the tendon section (15.3 kPa). The elasticity modulus values were distributed in the same way for each patient. The therapeutic benefit of SWE elastography was studied for the first time in tendon transfers. Quantitative data on the elasticity modulus during this test may make it an effective means of improving intraoperative adjustments. Copyright © 2017 SFCM. Published by Elsevier Masson SAS. All rights reserved.

Synergetic effect of graphene oxide-carbon nanotube on nanomechanical properties of acrylonitrile butadiene styrene nanocomposites

NASA Astrophysics Data System (ADS)

Jyoti, Jeevan; Pratap Singh, Bhanu; Chockalingam, Sreekumar; Joshi, Amish G.; Gupta, Tejendra K.; Dhakate, S. R.

2018-04-01

Herein, multiwall carbon nanotubes (MWCNTs), reduced graphene oxide (rGO), graphene oxide-carbon nanotubes (GCNTs) hybrid reinforced acrylonitrile butadiene styrene (ABS) nanocomposites have been prepared by micro twin screw extruder with back flow channel and the effect of different type of fillers on the nanomechanical properties are studied. The combination of both graphene oxide and CNT has enhanced the dispersion in polymer matrix and lower the probability of CNTs aggregation. GCNTs hybrid have been synthesized via novel chemical route and well characterized using Raman spectroscopic technique. The nanoindentation hardness and elastic modulus of GCNTs-ABS hybrid nanocomposites were improved from 211.3 MPa and 4.12 GPa of neat ABS to 298.9 MPa and 6.02 GPa, respectively at 5wt% GCNTs loading. In addition to hardness and elastic modulus, other mechanical properties i.e. plastic index parameter, elastic recovery, ratio of residual displacement after load removal and displacement at the maximum load and plastic deformation energy have also been investigated. These results were correlated with Raman and X-ray photoelectron spectroscopic (XPS) techniques and microstructural characterizations (scanning electron microscopy). Our demonstration would provide guidelines for the fabrication of hard and scratches nanocomposite materials for potential use in, automotive trim components and bumper bars, carrying cases and electronic industries and electromagnetic interference shielding.

Attenuation and Dispersion Analysis in Laboratory Measured Elastic Properties in the Middle East Carbonate Reservoir Rocks

NASA Astrophysics Data System (ADS)

Sharma, R.

2016-12-01

Carbonate rocks are sensitive to circulation of fluid types that leads to diagenetic alterations and therefore to heterogeneity in distribution of porosity and permeability. These heterogeneities in turn, lead to heterogeneity in saturations varying from partial to patchy to uniform. Depending on the interaction between fluids and rock matrix, a weakening or strengthening in shear modulus of carbonate rocks can also develop (Eberli et al., 2003; Adam et al., 2006; Sharma et al., 2009; Sharma et al., 2013). Thus the elastic response over the production life of the carbonate reservoirs can change considerably. Efforts to couple fluid flow with varying seismic properties of these reservoirs are limited in success due to the differences between static elastic properties derived from reservoir simulation and dynamic elastic properties derived from inverted seismic. An additional limitation arises from the assumption that shear modulus does not change with fluid type and saturations. To overcome these limitations, we need to understand the relationships between the static and the dynamic elastic properties using laboratory measurements made at varying pressures, frequencies and with varying saturants. I will present the following results: 1) errors associated with using dynamic (2 - 2000 Hz and 1 MHz) elastic properties data for static ( 0 Hz) reservoir properties, 2) shear modulus variation in carbonates upon saturation with varying saturants The results will enable us to estimate, 1) distribution of stress-strain relations in reservoir rocks and 2) modulus dispersion to correct seismic-derived moduli as inputs for reservoir simulators. The results are critical to estimate, 1) modulus dispersion correction and 2) occurrence and amount of shear modulus variation with fluid change vital for rock stability analysis

Bulk modulus of two-dimensional liquid dusty plasmas and its application

NASA Astrophysics Data System (ADS)

Li, Wei; Lin, Wei; Feng, Yan

2017-04-01

From the recently obtained equation of state [Feng et al., J. Phys. D: Appl. Phys. 49, 235203 (2016) and Feng et al., Phys. Plasmas 23, 093705 (2016); Erratum 23, 119904 (2016)], the bulk modulus of elasticity K of 2D liquid dusty plasmas is analytically derived as the expression of the temperature and the screening parameter. Exact values of the obtained bulk modulus of elasticity K are reported and also plotted in the 2D plane of the temperature and the screening parameter. As the temperature and the screening parameter change, the variation trend of K is reported and the corresponding interpretation is suggested. It has been demonstrated that the obtained bulk modulus of elasticity K can be used to predict the longitudinal sound speed, which agrees well with previous studies.

Effects of Cu and Ag as ternary and quaternary additions on some physical properties of SnSb7 bearing alloy

NASA Astrophysics Data System (ADS)

El-Bediwi, A. B.

2004-02-01

The structure, electrical resistivity, and elastic modulus of SnSb7 and SnSb7X (X = Cu , Ag, or Cu and Ag) rapidly solidified alloys have been investigated using X-ray diffractometer, double bridge, and dynamic resonance techniques. Copper and silver additions to SnSb result in the formation of a eutectic matrix containing embedded crystals (intermetallic phases) of SnCu, SnAg, and SnSb. The hard crystals SnCu, SnAg, and SnSb increase the overall hardness and wear resistance of SnSb bearing alloys. Addition of copper and silver improves internal friction, electrical conductivity, and elastic modulus values of SnSb rapidly solidified bearing alloys. The internal friction, elastic modulus, and electrical resistivity values are relatively sensitive to the composition of the intermediate phases in the matrix. The SbSb(7)Cu(2)g(2) has better properties (lowest internal friction, cost, adequate elastic modulus, and electrical resistivity) for bearing alloys as compared to cast iron and bronzes.

Elastic modulus of tree frog adhesive toe pads.

PubMed

Barnes, W Jon P; Goodwyn, Pablo J Perez; Nokhbatolfoghahai, Mohsen; Gorb, Stanislav N

2011-10-01

Previous work using an atomic force microscope in nanoindenter mode indicated that the outer, 10- to 15-μm thick, keratinised layer of tree frog toe pads has a modulus of elasticity equivalent to silicone rubber (5-15 MPa) (Scholz et al. 2009), but gave no information on the physical properties of deeper structures. In this study, micro-indentation is used to measure the stiffness of whole toe pads of the tree frog, Litoria caerulea. We show here that tree frog toe pads are amongst the softest of biological structures (effective elastic modulus 4-25 kPa), and that they exhibit a gradient of stiffness, being stiffest on the outside. This stiffness gradient results from the presence of a dense network of capillaries lying beneath the pad epidermis, which probably has a shock absorbing function. Additionally, we compare the physical properties (elastic modulus, work of adhesion, pull-off force) of the toe pads of immature and adult frogs.

Optimization of custom cementless stem using finite element analysis and elastic modulus distribution for reducing stress-shielding effect.

PubMed

Saravana Kumar, Gurunathan; George, Subin Philip

2017-02-01

This work proposes a methodology involving stiffness optimization for subject-specific cementless hip implant design based on finite element analysis for reducing stress-shielding effect. To assess the change in the stress-strain state of the femur and the resulting stress-shielding effect due to insertion of the implant, a finite element analysis of the resected femur with implant assembly is carried out for a clinically relevant loading condition. Selecting the von Mises stress as the criterion for discriminating regions for elastic modulus difference, a stiffness minimization method was employed by varying the elastic modulus distribution in custom implant stem. The stiffness minimization problem is formulated as material distribution problem without explicitly penalizing partial volume elements. This formulation enables designs that could be fabricated using additive manufacturing to make porous implant with varying levels of porosity. Stress-shielding effect, measured as difference between the von Mises stress in the intact and implanted femur, decreased as the elastic modulus distribution is optimized.

Mechanical evaluation of quad-helix appliance made of low-nickel stainless steel wire.

PubMed

dos Santos, Rogério Lacerda; Pithon, Matheus Melo

2013-01-01

The objective of this study was to test the hypothesis that there is no difference between stainless steel and low-nickel stainless steel wires as regards mechanical behavior. Force, resilience, and elastic modulus produced by Quad-helix appliances made of 0.032-inch and 0.036-inch wires were evaluated. Sixty Quad-helix appliances were made, thirty for each type of alloy, being fifteen for each wire thickness, 0.032-in and 0.036-in. All the archwires were submitted to mechanical compression test using an EMIC DL-10000 machine simulating activations of 4, 6, 9, and 12 mm. Analysis of variance (ANOVA) with multiple comparisons and Tukey's test were used (p < 0.05) to assess force, resilience, and elastic modulus. Statistically significant difference in the forces generated, resilience and elastic modulus were found between the 0.032-in and 0.036-in thicknesses (p < 0.05). Appliances made of low-nickel stainless steel alloy had force, resilience, and elastic modulus similar to those made of stainless steel alloy.

Compressive Strength and Modulus of Elasticity of Concrete with Cubed Waste Tire Rubbers as Coarse Aggregates

NASA Astrophysics Data System (ADS)

Haryanto, Y.; Hermanto, N. I. S.; Pamudji, G.; Wardana, K. P.

2017-11-01

One feasible solution to overcome the issue of tire disposal waste is the use of waste tire rubber to replace aggregate in concrete. We have conducted an experimental investigation on the effect of rubber tire waste aggregate in cuboid form on the compressive strength and modulus of elasticity of concrete. The test was performed on 72 cylindrical specimens with the height of 300 mm and diameter of 150 mm. We found that the workability of concrete with waste tire rubber aggregate has increased. The concrete density with waste tire rubber aggregate was decreased, and so was the compressive strength. The decrease of compressive strength is up to 64.34%. If the content of waste tire rubber aggregate is more than 40%, then the resulting concrete cannot be categorized as structural concrete. The modulus of elasticity decreased to 59.77%. The theoretical equation developed to determine the modulus of elasticity of concrete with rubber tire waste aggregate has an accuracy of 84.27%.

Bendable Electro-Acoustic Transducer Fabricated Utilizing Frequency Dispersion of Elastic Modulus

NASA Astrophysics Data System (ADS)

Miyoshi, Tetsu; Ohga, Juro

2013-09-01

To realize the speaker diaphragm that can be united with a flexible display without deteriorating lightweight properties and flexibility, a novel bendable electro-acoustic transducer (BEAT) based on 0-3-type piezoelectric composites has been developed. To overcome the trade-off between flexibility and the transmission efficiency of vibration energy, a viscoelastic polymer that has local maximum points in the loss factor as well as large frequency dispersion in the storage modulus near room temperature was employed as the matrix of the piezoelectric composite layer. Against the comparatively slow (10 Hz or less) deformation from the outside, the viscoelastic matrix is viscous enough to prevent cracking and delamination. On the other hand, in the audible range (20 Hz to 20 kHz), the matrix is elastic enough to transmit piezoelectric vibration energy, maintaining a moderately large loss factor as well as a high sound velocity. For the first time, we successfully demonstrated a rollable speaker that can continue to generate a high-quality sound while being rolled and unrolled repeatedly onto a cylinder with a curvature radius of 4 mm.

Effects of Cryogenic Temperature on Fracture Toughness of Core-Shell Rubber (CSR) Toughened Epoxy Nanocomposites

NASA Technical Reports Server (NTRS)

Wang, J.; Cannon, S. A.; Magee, D.; Schneider, J. A.

2008-01-01

This study investigated the effects of core-shell rubber (CSR) nanoparticles on the mechanical properties and fracture toughness of an epoxy resin at ambient and liquid nitrogen (LN2) temperatures. Varying amounts of Kane Ace MX130 toughening agent were added to a commercially available EPON 862/Epikure W epoxy resin. Elastic modulus was calculated using quasi-static tensile data. Fracture toughness was evaluated by the resulting breaking energy measured in Charpy impact tests conducted on an instrumented drop tower. The size and distribution of the CSR nanoparticles were characterized using Transmission Electron Microscopy (TEM) and Small Angle X-ray Scattering (SAXS). Scanning Electron Microscopy (SEM) was used to study the fracture surface morphology. The addition of the CSR nanoparticles increased the breaking energy with negligible change in elastic modulus and ultimate tensile stress (UTS). At ambient temperature the breaking energy increased with increasing additions of the CSR nanoparticles, while at LN2 temperatures, it reached a maximum at 5 wt% CSR concentration. KEY WORDS: liquid nitrogen (LN2) properties, fracture toughness, core-shell rubber (CSR).

A novel method to determine the elastic modulus of extremely soft materials.

PubMed

Stirling, Tamás; Zrínyi, Miklós

2015-06-07

Determination of the elastic moduli of extremely soft materials that may deform under their own weight is a rather difficult experimental task. A new method has been elaborated by means of which the elastic modulus of such materials can be determined. This method is generally applicable to all soft materials with purely neo-Hookean elastic deformation behaviour with elastic moduli lower than 1 kPa. Our novel method utilises the self-deformation of pendent gel cylinders under gravity. When suspended, the material at the very top bears the weight of the entire gel cylinder, but that at the bottom carries no load at all. Due to the non-uniform stress distribution along the gel sample both the stress and the resulting strain show position dependence. The cross-sectional area of the material is lowest at the top of the sample and gradually increases towards its bottom. The equilibrium geometry of the pendant gel is used to evaluate the elastic modulus. Experimental data obtained by the proposed new method were compared to the results obtained from underwater measurements. The parameters affecting the measurement uncertainty were studied by a Pareto analysis of a series of adaptive Monte Carlo simulations. It has been shown that our method provides an easily achievable method to provide an accurate determination of the elastic modulus of extremely soft matter typically applicable for moduli below 1 kPa.

Measuring the elastic properties of fine wire.

PubMed

Fallen, C T; Costello, J; Crawford, G; Schmidt, J A

2001-01-01

The elastic moduli of fine wires made from MP35N and 304SS used in implantable biomedical devices are assumed to be the same as those published in the literature. However, the cold working required to manufacture the wire significantly alters the elastic moduli of the material. We describe three experiments performed on fine wire made from MP35N and 304SS. The experimentally determined Young's and shear modulus of both wire types were significantly less than the moduli reported in the literature. Young's modulus differed by as much as 26%, and the shear modulus differed by as much as 14% from reported values.

The first principles study of elastic and thermodynamic properties of ZnSe

NASA Astrophysics Data System (ADS)

Khatta, Swati; Kaur, Veerpal; Tripathi, S. K.; Prakash, Satya

2018-05-01

The elastic and thermodynamic properties of ZnSe are investigated using thermo_pw package implemented in Quantum espresso code within the framework of density functional theory. The pseudopotential method within the local density approximation is used for the exchange-correlation potential. The physical parameters of ZnSe bulk modulus and shear modulus, anisotropy factor, Young's modulus, Poisson's ratio, Pugh's ratio and Frantsevich's ratio are calculated. The sound velocity and Debye temperature are obtained from elastic constant calculations. The Helmholtz free energy and internal energy of ZnSe are also calculated. The results are compared with available theoretical calculations and experimental data.

Structural, elastic and electronic properties of transition metal carbides ZnC, NbC and their ternary alloys ZnxNb1-xC

NASA Astrophysics Data System (ADS)

Zidi, Y.; Méçabih, S.; Abbar, B.; Amari, S.

2018-02-01

We have investigated the structural, electronic and elastic properties of transition-metal carbides ZnxNb1-xC alloys in the range of 0 ≤ x ≤ 1 using the density functional theory (DFT). The full potential linearized augmented plane wave (FP-LAPW) method within a framework of the generalized gradient approximation (GGA) and GGA + U (where U is the Hubbard correlation terms) approach is used to perform the calculations presented here. The lattice parameters, the bulk modulus, its pressure derivative and the elastic constants were determined. We have obtained Young's modulus, shear modulus, Poisson's ratio, anisotropy factor by the aid of the calculated elastic constants. We discuss the total and partial densities of states and charge densities.

3D Modeling Effect of Spherical Inclusions on the Magnetostriction of Bulk Superconductors

NASA Astrophysics Data System (ADS)

Zhao, Yufeng; Pan, Baocai

2018-02-01

In this paper, the dependence of the effective magnetostriction of bulk superconductors on the elastic parameters including the volume fraction and elastic modulus ratio is studied by a three-dimensional model consisting of a spherical inclusion-superconducting matrix system. The effect of the elastic modulus and volume fraction on the magnetostriction is also obtained through the magnetostriction loop. The results indicate that the elastic modulus and volume fraction have obvious effects on the effective magnetostriction of the superconducting composite, which gives an explanation about the differences between the experimental and the theoretical results. Furthermore, it is worth pointing out that the linear field dependence of magnetostriction is unique to the Bean model by comparing the curve shapes of the magnetostriction loop with and without inclusion.

Equilibrium structures of carbon diamond-like clusters and their elastic properties

NASA Astrophysics Data System (ADS)

Lisovenko, D. S.; Baimova, Yu. A.; Rysaeva, L. Kh.; Gorodtsov, V. A.; Dmitriev, S. V.

2017-04-01

Three-dimensional carbon diamond-like phases consisting of sp 3-hybridized atoms, obtained by linking of carcasses of fullerene-like molecules, are studied by methods of molecular dynamics modeling. For eight cubic and one hexagonal diamond-like phases on the basis of four types of fullerene-like molecules, equilibrium configurations are found and the elastic constants are calculated. The results obtained by the method of molecular dynamics are used for analytical calculations of the elastic characteristics of the diamond- like phases with the cubic and hexagonal anisotropy. It is found that, for a certain choice of the dilatation axis, three of these phases have negative Poisson's ratio, i.e., are partial auxetics. The variability of the engineering elasticity coefficients (Young's modulus, Poisson's ratio, shear modulus, and bulk modulus) is analyzed.

Development of Polydimethylsiloxane Substrates with Tunable Elastic Modulus to Study Cell Mechanobiology in Muscle and Nerve

PubMed Central

Palchesko, Rachelle N.; Zhang, Ling; Sun, Yan; Feinberg, Adam W.

2012-01-01

Mechanics is an important component in the regulation of cell shape, proliferation, migration and differentiation during normal homeostasis and disease states. Biomaterials that match the elastic modulus of soft tissues have been effective for studying this cell mechanobiology, but improvements are needed in order to investigate a wider range of physicochemical properties in a controlled manner. We hypothesized that polydimethylsiloxane (PDMS) blends could be used as the basis of a tunable system where the elastic modulus could be adjusted to match most types of soft tissue. To test this we formulated blends of two commercially available PDMS types, Sylgard 527 and Sylgard 184, which enabled us to fabricate substrates with an elastic modulus anywhere from 5 kPa up to 1.72 MPa. This is a three order-of-magnitude range of tunability, exceeding what is possible with other hydrogel and PDMS systems. Uniquely, the elastic modulus can be controlled independently of other materials properties including surface roughness, surface energy and the ability to functionalize the surface by protein adsorption and microcontact printing. For biological validation, PC12 (neuronal inducible-pheochromocytoma cell line) and C2C12 (muscle cell line) were used to demonstrate that these PDMS formulations support cell attachment and growth and that these substrates can be used to probe the mechanosensitivity of various cellular processes including neurite extension and muscle differentiation. PMID:23240031

A two-layered mechanical model of the rat esophagus. Experiment and theory

PubMed Central

Fan, Yanhua; Gregersen, Hans; Kassab, Ghassan S

2004-01-01

Background The function of esophagus is to move food by peristaltic motion which is the result of the interaction of the tissue forces in the esophageal wall and the hydrodynamic forces in the food bolus. The structure of the esophagus is layered. In this paper, the esophagus is treated as a two-layered structure consisting of an inner collagen-rich submucosa layer and an outer muscle layer. We developed a model and experimental setup for determination of elastic moduli in the two layers in circumferential direction and related the measured elastic modulus of the intact esophagus to the elastic modulus computed from the elastic moduli of the two layers. Methods Inflation experiments were done at in vivo length and pressure-diameters relations were recorded for the rat esophagus. Furthermore, the zero-stress state was taken into consideration. Results The radius and the strain increased as function of pressure in the intact as well as in the individual layers of the esophagus. At pressures higher than 1.5 cmH2O the muscle layer had a larger radius and strain than the mucosa-submucosa layer. The strain for the intact esophagus and for the muscle layer was negative at low pressures indicating the presence of residual strains in the tissue. The stress-strain curve for the submucosa-mucosa layer was shifted to the left of the curves for the muscle layer and for the intact esophagus at strains higher than 0.3. The tangent modulus was highest in the submucosa-mucosa layer, indicating that the submucosa-mucosa has the highest stiffness. A good agreement was found between the measured elastic modulus of the intact esophagus and the elastic modulus computed from the elastic moduli of the two separated layers. PMID:15518591

Quantitative photoacoustic elastography of Young's modulus in humans

NASA Astrophysics Data System (ADS)

Hai, Pengfei; Zhou, Yong; Gong, Lei; Wang, Lihong V.

2017-03-01

Elastography can noninvasively map the elasticity distribution of biological tissue, which is often altered in pathological states. In this work, we report quantitative photoacoustic elastography (QPAE), capable of measuring Young's modulus of human tissue in vivo. By combining photoacoustic elastography with a stress sensor having known stress-strain behavior, QPAE can simultaneously measure strain and stress, from which Young's modulus is calculated. We first applied QPAE to quantify the Young's modulus of tissue-mimicking agar phantoms with different concentrations. The measured values fitted well with both the empirical expectations based on the agar concentrations and those measured in independent standard compression tests. We then demonstrated the feasibility of QPAE by measuring the Young's modulus of human skeletal muscle in vivo. The data showed a linear relationship between muscle stiffness and loading. The results proved that QPAE can noninvasively quantify the absolute elasticity of biological tissue, thus enabling longitudinal imaging of tissue elasticity. QPAE can be exploited for both preclinical biomechanics studies and clinical applications.

Effect of pH on the rheological properties of borate crosslinked hydroxypropyl guar gum hydrogel and hydroxypropyl guar gum.

PubMed

Wang, Shibin; Tang, Hongbiao; Guo, Jianchun; Wang, Kunjie

2016-08-20

pH is an important factor affecting the performance of polymer fluid. The rheological properties of hydroxypropyl guar gum (HPG) base fluid and the structural strength, rheological properties, viscoelastic properties and thixotropy properties of HPG gel depend largely on the pH values. For the base fluid, an apparent viscosity-increasing effect was observed over the pH range from 7 to 11, and the apparent viscosity gradually decreased at pH 11.5-14, exhibiting electrostatic repulsion behavior and steric effects. For the HPG gel, at pH 7-12.5, the gel possessed higher apparent viscosity, higher elastic modulus (G'), lower tanδ (the ratio of the viscous modulus to the elastic modulus) and an "8"-shaped hysteresis loop, indicating stronger gel structure strength and the elastic dominant property. At pH 13-13.5, the gel samples exhibited the transition from a pseudoplastic fluid to a Newtonian fluid, and their viscosity, elastic modulus decreased but tanδ increased with the increase in pH values, exhibiting gradually weakened elastic properties. When the pH was 14, the gel mainly exhibited viscous characteristics. Copyright © 2016 Elsevier Ltd. All rights reserved.

Southern pine veneer laminates at various moduli of elasticity

Treesearch

George E. Woodson

1972-01-01

Modulus of rigidity (GLT) of veneer laminates was shown to be unrelated to dynamic modulus of elasticity (Ed) of single veneers and also, within the range of samples tested, unrelated to specific gravity. Values determined by flexure test (GLR) were consistent with those from standard plate shear...

Elasticity and inelasticity of silicon nitride/boron nitride fibrous monoliths.

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

Smirnov, B. I.; Burenkov, Yu. A.; Kardashev, B. K.

A study is reported on the effect of temperature and elastic vibration amplitude on Young's modulus E and internal friction in Si{sub 3}N{sub 4} and BN ceramic samples and Si{sub 3}N{sub 4}/BN monoliths obtained by hot pressing of BN-coated Si{sub 3}N{sub 4} fibers. The fibers were arranged along, across, or both along and across the specimen axis. The E measurements were carried out under thermal cycling within the 20-600 C range. It was found that high-modulus silicon-nitride specimens possess a high thermal stability; the E(T) dependences obtained under heating and cooling coincide well with one another. The low-modulus BN ceramicmore » exhibits a considerable hysteresis, thus indicating evolution of the defect structure under the action of thermoelastic (internal) stresses. Monoliths demonstrate a qualitatively similar behavior (with hysteresis). This behavior of the elastic modulus is possible under microplastic deformation initiated by internal stresses. The presence of microplastic shear in all the materials studied is supported by the character of the amplitude dependences of internal friction and the Young's modulus. The experimental data obtained are discussed in terms of a model in which the temperature dependences of the elastic modulus and their features are accounted for by both microplastic deformation and nonlinear lattice-atom vibrations, which depend on internal stresses.« less

Soft-tissue allografts terminally sterilized with an electron beam are biomechanically equivalent to aseptic, nonsterilized tendons.

PubMed

Elenes, Egleide Y; Hunter, Shawn A

2014-08-20

Allograft safety is contingent on effective sterilization. However, current sterilization methods have been associated with decreased biomechanical strength and higher failure rates of soft-tissue allografts. In this study, electron beam (e-beam) sterilization was explored as an alternative sterilization method to preserve biomechanical integrity. We hypothesized that e-beam sterilization would not significantly alter the biomechanical properties of tendon allograft compared with aseptic, nonsterilized controls and gamma-irradiated grafts. Separate sets of forty fresh-frozen tibialis tendon allografts (four from each of ten donors) and forty bisected bone-patellar tendon-bone (BTB) allografts (four from each of ten donors) were randomly assigned to four study groups. One group received a 17.1 to 21.0-kGy gamma radiation dose; two other groups were sterilized with an e-beam at either a high (17.1 to 21.0-kGy) or low (9.2 to 12.2-kGy) dose. A fourth group served as nonsterilized controls. Each graft was cyclically loaded to 200 N of tension for 2000 cycles at a frequency of 2 Hz, allowed to relax for five minutes, and then tested in tension until failure at a 100%/sec strain rate. One-way analysis of variance testing was used to identify significant differences. Tibialis tendons sterilized with both e-beam treatments and with gamma irradiation exhibited values for cyclic tendon elongation, maximum load, maximum displacement, stiffness, maximum stress, maximum strain, and elastic modulus that were not significantly different from those of nonsterilized controls. BTB allografts sterilized with the high e-beam dose and with gamma irradiation were not significantly different in cyclic tendon elongation, maximum load, maximum displacement, stiffness, maximum stress, maximum strain, and elastic modulus from nonsterilized controls. BTB allografts sterilized with the e-beam at the lower dose were significantly less stiff than nonsterilized controls (p = 0.014) but did not differ from controls in any other properties. The difference in stiffness likely resulted from variations in tendon size rather than the treatments, as the elastic moduli of the groups were similar. The biomechanical properties of tibialis and BTB allografts sterilized with use of an e-beam at a dose range of 17.1 to 21.0 kGy were not different from those of aseptic, nonsterilized controls or gamma-irradiated allografts. E-beam sterilization can be a viable method to produce safe and biomechanically uncompromised soft-tissue allografts. Copyright © 2014 by The Journal of Bone and Joint Surgery, Incorporated.

Magneto-elastic modeling of composites containing chain-structured magnetostrictive particles

NASA Astrophysics Data System (ADS)

Yin, H. M.; Sun, L. Z.; Chen, J. S.

2006-05-01

Magneto-elastic behavior is investigated for two-phase composites containing chain-structured magnetostrictive particles under both magnetic and mechanical loading. To derive the local magnetic and elastic fields, three modified Green's functions are derived and explicitly integrated for the infinite domain containing a spherical inclusion with a prescribed magnetization, body force, and eigenstrain. A representative volume element containing a chain of infinite particles is introduced to solve averaged magnetic and elastic fields in the particles and the matrix. Effective magnetostriction of composites is derived by considering the particle's magnetostriction and the magnetic interaction force. It is shown that there exists an optimal choice of the Young's modulus of the matrix and the volume fraction of the particles to achieve the maximum effective magnetostriction. A transversely isotropic effective elasticity is derived at the infinitesimal deformation. Disregarding the interaction term, this model provides the same effective elasticity as Mori-Tanaka's model. Comparisons of model results with the experimental data and other models show the efficacy of the model and suggest that the particle interactions have a considerable effect on the effective magneto-elastic properties of composites even for a low particle volume fraction.

The effect of porosity on the mechanical properties of porous titanium scaffolds: comparative study on experimental and analytical values

NASA Astrophysics Data System (ADS)

Khodaei, Mohammad; Fathi, Mohammadhossein; Meratian, Mahmood; Savabi, Omid

2018-05-01

Reducing the elastic modulus and also improving biological fixation to the bone is possible by using porous scaffolds. In the present study, porous titanium scaffolds containing different porosities were fabricated using the space holder method. Pore distribution, formed phases and mechanical properties of titanium scaffolds were studied by Scanning Electron Microscope (SEM), x-ray diffraction (XRD) and cold compression test. Then the results of compression test were compared to the Gibson-Ashby model. Both experimentally measured and analytically calculated elastic modulus of porous titanium scaffolds decreased by porosity increment. The compliance between experimentally measured and analytically calculated elastic modulus of titanium scaffolds are also increased by porosity increment.

Development of a Nondestructive Non-Contact Acousto-Thermal Evaluation Technique for Damage Detection in Materials (Preprint)

DTIC Science & Technology

2011-11-01

horn and the sample to obtain a repeatable excitation for detection of the damage of interest. Varieties of materials, including card stock, leather ...per cycle is, (2). where Tan , is the internal friction in the material, E is the Young’s modulus and σmax is the maximum amplitude of the...of acoustic energy to thermal energy depends on both the elastic properties (E and tan ) and the thermal properties (k, Cp) of the material. It

Fatigue behavior of a cross-ply ceramic matrix composite at elevated temperature under tension-tension loading. Master`s thesis

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

Steiner, C.D.

This study investigated the fatigue behavior and damage mechanisms of a (0/90)4s SiC/MAS ceramic matrix composite under tension-tension loading at two elevated temperatures and two frequencies. Stress and strain hystereses, maximum and minimum strain, and modulus of elasticity were evaluated to characterize the material behavior. Microscopy and fractography were used to evaluate damage progression and mechanisms. Fatigue life was independent of frequency at both temperatures.

Structural, magnetic, elastic, dielectric and electrical properties of hot-press sintered Co1-xZnxFe2O4 (x = 0.0, 0.5) spinel ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Singh Yadav, Raghvendra; Kuřitka, Ivo; Havlica, Jaromir; Hnatko, Miroslav; Alexander, Cigáň; Masilko, Jiri; Kalina, Lukas; Hajdúchová, Miroslava; Rusnak, Jaroslav; Enev, Vojtěch

2018-02-01

In this article, Co1-xZnxFe2O4 (x = 0.0 and 0.5) disc-shaped pellets were formed by hot-press sintering of nanoparticles at temperature 925 °C for 10 min in vacuum atmosphere under 30 MPa mechanical pressure. X-ray diffraction study confirmed the formation of spinel cubic ferrite structure of hot-press sintered spinel ferrite Co1-xZnxFe2O4 (x = 0.0 and 0.5) samples. The scanning electron microscopy image indicated that the growth and densification of smaller ferrite nanoparticles were higher than larger ferrite nanoparticles. Magnetic properties of sintered samples were investigated by the superconducting quantum interface device (SQUID) magnetometer at room temperature. The hot press sintered Co1-xZnxFe2O4 (x = 0.0 and 0.5) pellet samples exhibited magnetic properties dependent on the grain size of spinel ferrite particles. The maximum saturation magnetization 82.47 emu/g was obtained for Co0.5Zn0.5Fe2O4 hot press sintered sample of ball-milled ferrite particles. Further, the impact of grain size and density of sample on hardness, dielectric property and ac conductivity of hot-press sintered samples was investigated. In addition, the longitudinal wave velocity (Vl), transverse wave velocity (Vt), mean elastic wave velocity (Vm), bulk modulus (B), rigidity modulus (G), Young's modulus (E), Poisson ratio (σ) and Debye temperature (θD) were calculated. The elastic moduli of hot press sintered ferrite samples were corrected to zero porosity using Hosselman and Fulrath model.

Mechanical properties of the human scalp in tension.

PubMed

Falland-Cheung, Lisa; Scholze, Mario; Lozano, Pamela F; Ondruschka, Benjamin; Tong, Darryl C; Brunton, Paul A; Waddell, J Neil; Hammer, Niels

2018-08-01

Mechanical properties of the human scalp have not been investigated to a great extent with limited information available. The purpose of this study was to provide new baseline material data for human scalp tissue of various ages, which can be applied to experimental and constitutive models, such as in the area of impact biomechanics. This study used specimens from the left and right temporal, fronto-parietal and occipital regions of the human scalp. It investigated the tensile behavior of scalp tissue using tissues harvested from unfixed, fresh cadavers. These samples were subjected to an osmotic stress analysis and upon testing, cyclic loading followed by stretching until failure in a universal testing machine. Strain evaluation was conducted using digital image correlation in a highly standardized approach. Elastic modulus, tensile strength, strain at maximum load and strain to failure were evaluated computationally. No significant differences were observed comparing the tensile strength between males and females. In contrast to that, a sex-dependent difference was found for the elastic modulus of the occipital scalp region and for the elongation properties. Additionally, regional differences within the male group, as well as an age dependent correlation for females were found in the elastic modulus and tensile strength. Scanning electron microscope analyses have shown the ultrastructural failure patterns, indicated by damaged keratin plates, as well as partially disrupted and retraced collagens at the failure site. The novel data obtained in this study could add valuable information to be used for modeling purposes, as well as provide baseline data for simulant materials and comparisons of tissue properties following head injury or forensic investigations. Copyright © 2018 Elsevier Ltd. All rights reserved.

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

Moraes, Paulo E.L., E-mail: pauloeduardo.leitedemoraes@gmail.com; Contieri, Rodrigo J., E-mail: contieri@fem.unicamp.br; Lopes, Eder S.N., E-mail: ederlopes@fem.unicamp.br

Ti and Ti alloys are widely used in restorative surgery because of their good biocompatibility, enhanced mechanical behavior and high corrosion resistance in physiological media. The corrosion resistance of Ti-based materials is due to the spontaneous formation of the TiO{sub 2} oxide film on their surface, which exhibits elevated stability in biological fluids. Ti–Nb alloys, depending on the composition and the processing routes to which the alloys are subjected, have high mechanical strength combined with low elastic modulus. The addition of Sn to Ti–Nb alloys allows the phase transformations to be controlled, particularly the precipitation of ω phase. The aimmore » of this study is to discuss the microstructure, mechanical properties and corrosion behavior of cast Ti–Nb alloys to which Sn has been added. Samples were centrifugally cast in a copper mold, and the microstructure was characterized using optical microscopy, scanning electron microscopy and X-ray diffractometry. Mechanical behavior evaluation was performed using Berkovich nanoindentation, Vickers hardness and compression tests. The corrosion behavior was evaluated in Ringer's solution at room temperature using electrochemical techniques. The results obtained suggested that the physical, mechanical and chemical behaviors of the Ti–Nb–Sn alloys are directly dependent on the Sn content. - Graphical abstract: Effects of Sn addition to the Ti–30Nb alloy on the elastic modulus. - Highlights: • Sn addition causes reduction of the ω phase precipitation. • Minimum Vickers hardness and elastic modulus occurred for 6 wt.% Sn content. • Addition of 6 wt.% Sn resulted in maximum ductility and minimum compression strength. • All Ti–30Nb–XSn (X = 0, 2, 4, 6, 8 and 10%) alloys are passive in Ringer's solution. • Highest corrosion resistance was observed for 6 wt.% Sn content.« less

Concentration Dependent Physical Properties of Ge1-xSnx Solid Solution

NASA Astrophysics Data System (ADS)

Jivani, A. R.; Jani, A. R.

2011-12-01

Our own proposed potential is used to investigate few physical properties like total energy, bulk modulus, pressure derivative of bulk modulus, elastic constants, pressure derivative of elastic constants, Poisson's ratio and Young's modulus of Ge1-xSnx solid solution with x is atomic concentration of α-Sn. The potential combines linear plus quadratic types of electron-ion interaction. First time screening function proposed by Sarkar et al is used to investigate the properties of the Ge-Sn solid solution system.

Improving the estimate of the effective elastic modulus derived from three-point bending tests of long bones.

PubMed

Kourtis, Lampros C; Carter, Dennis R; Beaupre, Gary S

2014-08-01

Three-point bending tests are often used to determine the apparent or effective elastic modulus of long bones. The use of beam theory equations to interpret such tests can result in a substantial underestimation of the true effective modulus. In this study three-dimensional, nonlinear finite element analysis is used to quantify the errors inherent in beam theory and to create plots that can be used to correct the elastic modulus calculated from beam theory. Correction plots are generated for long bones representative of a variety of species commonly used in research studies. For a long bone with dimensions comparable to the mouse femur, the majority of the error in the effective elastic modulus results from deformations to the bone cross section that are not accounted for in the equations from beam theory. In some cases, the effective modulus calculated from beam theory can be less than one-third of the true effective modulus. Errors are larger: (1) for bones having short spans relative to bone length; (2) for bones with thin vs. thick cortices relative to periosteal diameter; and (3) when using a small radius or "knife-edge" geometry for the center loading ram and the outer supports in the three-point testing system. The use of these correction plots will enable researchers to compare results for long bones from different animal strains and to compare results obtained using testing systems that differ with regard to length between the outer supports and the radius used for the loading ram and outer supports.

Crystalline cellulose elastic modulus predicted by atomistic models of uniform deformation and nanoscale indentation

Treesearch

Xiawa Wu; Robert J. Moon; Ashlie Martini

2013-01-01

The elastic modulus of cellulose Iß in the axial and transverse directions was obtained from atomistic simulations using both the standard uniform deformation approach and a complementary approach based on nanoscale indentation. This allowed comparisons between the methods and closer connectivity to experimental measurement techniques. A reactive...

[Water parameters of desert xeric shrubs in west Erdos region].

PubMed

Li, Xiao; Wang, Ying-chun; Zheng, Rong

2007-05-01

By using PV technique, this paper studied the turgor pressure (psi P), cell elastic modulus (epsilon), and relative cell volume (RCV) of super xerophytes Potaninia mongolica, Reaumuria soongorica, Tetraena mongolica and Zygophyllum xanthoxylon in west Alashan, with the relationships among the parameters analyzed. The results showed that R. soongorica had the strongest ability to maintain maximum turgor pressure (a = 2.4593). The four plants maintained their turgor pressure by different ways, i.e., P. mongolica maintained it by elastic adjustment (epsilon max = 8.4005 MPa), R. soongorica by osmotic adjustment (psi pi100 = -3.1302 MPa; psi0 = -3.5074 MPa), T. mongolica by both osmotic and elastic adjustment, and Z. xanthoxylon by osmotic adjustment, which had weak adjustment ability. The cell wall of P. mongolica was soft and highly elastic, benefiting to the water absorption by root and stem and to the fast water transmission. T. mongolica also had relatively soft and high elastic cell wall, and its psi P, and epsilon changed slowly with decreasing RCV, suggesting that this plant had strong ability of holding water and resisting dehydration.

Elastic-Mathematical Theory of Cells and Mitochondria in Swelling Process

PubMed Central

Mela, M. J.

1968-01-01

The elastic behavior of the cell wall as a function of the temperature has been studied with particular attention being given to the swelling of egg cells of Strongylocentrotus purpuratus and Crassostrea virginica in different sea water concentrations at different temperatures. It was found that the modulus of elasticity is a nonlinear function of temperature. At about 12-13°C the modulus of elasticity (E) is constant, independent of the stress (σ) and strain (εν) which exist at the cell wall; the membranous material follows Hooke's law, and E ≈ 3 × 107 dyn/cm2 for S. purpuratus and C. virginica. When the temperature is higher or lower than 12-13°C, the modulus of elasticity increases, and the membranous material does not follow Hooke's law, but is almost directly proportional to the stresses existing at the cell wall. On increasing the stress, the function Eσ = E(σ) approaches saturation. The corresponding stress-strain diagrams, σ = σ(εν), and the graphs, Eσ = E(σ) and Eσ = E(t) are given. The cyto-elastic phenomena at the membrane are discussed. PMID:5689191

Design of Strain-Limiting Substrate Materials for Stretchable and Flexible Electronics

PubMed Central

Ma, Yinji; Jang, Kyung-In; Wang, Liang; Jung, Han Na; Kwak, Jean Won; Xue, Yeguang; Chen, Hang; Yang, Yiyuan; Shi, Dawei; Feng, Xue

2017-01-01

Recently developed classes of electronics for biomedical applications exploit substrates that offer low elastic modulus and high stretchability, to allow intimate, mechanically biocompatible integration with soft biological tissues. A challenge is that such substrates do not generally offer protection of the electronics from high peak strains that can occur upon large-scale deformation, thereby creating a potential for device failure. The results presented here establish a simple route to compliant substrates with strain-limiting mechanics based on approaches that complement those of recently described alternatives. Here, a thin film or mesh of a high modulus material transferred onto a prestrained compliant substrate transforms into wrinkled geometry upon release of the prestrain. The structure formed by this process offers a low elastic modulus at small strain due to the small effective stiffness of the wrinkled film or mesh; it has a high tangent modulus (e.g., >1000 times the elastic modulus) at large strain, as the wrinkles disappear and the film/mesh returns to a flat geometry. This bilinear stress–strain behavior has an extremely sharp transition point, defined by the magnitude of the prestrain. A theoretical model yields analytical expressions for the elastic and tangent moduli and the transition strain of the bilinear stress–strain relation, with quantitative correspondence to finite element analysis and experiments. PMID:29033714

Design of Strain-Limiting Substrate Materials for Stretchable and Flexible Electronics.

PubMed

Ma, Yinji; Jang, Kyung-In; Wang, Liang; Jung, Han Na; Kwak, Jean Won; Xue, Yeguang; Chen, Hang; Yang, Yiyuan; Shi, Dawei; Feng, Xue; Rogers, John A; Huang, Yonggang

2016-08-02

Recently developed classes of electronics for biomedical applications exploit substrates that offer low elastic modulus and high stretchability, to allow intimate, mechanically biocompatible integration with soft biological tissues. A challenge is that such substrates do not generally offer protection of the electronics from high peak strains that can occur upon large-scale deformation, thereby creating a potential for device failure. The results presented here establish a simple route to compliant substrates with strain-limiting mechanics based on approaches that complement those of recently described alternatives. Here, a thin film or mesh of a high modulus material transferred onto a prestrained compliant substrate transforms into wrinkled geometry upon release of the prestrain. The structure formed by this process offers a low elastic modulus at small strain due to the small effective stiffness of the wrinkled film or mesh; it has a high tangent modulus (e.g., >1000 times the elastic modulus) at large strain, as the wrinkles disappear and the film/mesh returns to a flat geometry. This bilinear stress-strain behavior has an extremely sharp transition point, defined by the magnitude of the prestrain. A theoretical model yields analytical expressions for the elastic and tangent moduli and the transition strain of the bilinear stress-strain relation, with quantitative correspondence to finite element analysis and experiments.

Elasticity of microscale volumes of viscoelastic soft matter by cavitation rheometry

NASA Astrophysics Data System (ADS)

Pavlovsky, Leonid; Ganesan, Mahesh; Younger, John G.; Solomon, Michael J.

2014-09-01

Measurement of the elastic modulus of soft, viscoelastic liquids with cavitation rheometry is demonstrated for specimens as small as 1 μl by application of elasticity theory and experiments on semi-dilute polymer solutions. Cavitation rheometry is the extraction of the elastic modulus of a material, E, by measuring the pressure necessary to create a cavity within it [J. A. Zimberlin, N. Sanabria-DeLong, G. N. Tew, and A. J. Crosby, Soft Matter 3, 763-767 (2007)]. This paper extends cavitation rheometry in three ways. First, we show that viscoelastic samples can be approximated with the neo-Hookean model provided that the time scale of the cavity formation is measured. Second, we extend the cavitation rheometry method to accommodate cases in which the sample size is no longer large relative to the cavity dimension. Finally, we implement cavitation rheometry to show that the theory accurately measures the elastic modulus of viscoelastic samples with volumes ranging from 4 ml to as low as 1 μl.

Resonant Acoustic Determination of Complex Elastic Moduli

NASA Technical Reports Server (NTRS)

Brown, David A.; Garrett, Steven L.

1991-01-01

A simple, inexpensive, yet accurate method for measuring the dynamic complex modulus of elasticity is described. Using a 'free-free' bar selectively excited in three independent vibrational modes, the shear modulus is obtained by measuring the frequency of the torsional resonant mode and the Young's modulus is determined from measurement of either the longitudinal or flexural mode. The damping properties are obtained by measuring the quality factor (Q) for each mode. The Q is inversely proportional to the loss tangent. The viscoelastic behavior of the sample can be obtained by tracking a particular resonant mode (and thus a particular modulus) using a phase locked loop (PLL) and by changing the temperature of the sample. The change in the damping properties is obtained by measuring the in-phase amplitude of the PLL which is proportional to the Q of the material. The real and imaginary parts or the complex modulus can be obtained continuously as a function of parameters such as temperature, pressure, or humidity. For homogeneous and isotropic samples only two independent moduli are needed in order to characterize the complete set of elastic constants, thus, values can be obtained for the dynamic Poisson's ratio, bulk modulus, Lame constants, etc.

The elastic properties of cancerous skin: Poisson's ratio and Young's modulus.

PubMed

Tilleman, Tamara Raveh; Tilleman, Michael M; Neumann, Martino H A

2004-12-01

The physical properties of cancerous skin tissue have rarely been measured in either fresh or frozen skin specimens. Of interest are the elastic properties associated with the skin's ability to deform, i.e., to stretch and compress. Two constants--Young's modulus and Poisson's ratio--represent the basic elastic behavior pattern of any elastic material, including skin. The former relates the applied stress on a specimen to its deformation via Hooke's law, while the latter is the ratio between the axial and lateral strains. To investigate the elastic properties of cancerous skin tissue. For this purpose 23 consecutive cancerous tissue specimens prepared during Mohs micrographic surgery were analyzed. From these specimens we calculated the change in radial length (defined as the radial strain) and the change in tissue thickness (defined as axial strain). Based on the above two strains we determined a Poisson ratio of 0.43 +/- 0.12 and an average Young modulus of 52 KPa. Defining the elastic properties of cancerous skin may become the first step in turning elasticity into a clinical tool. Correlating these constants with the histopathologic features of a cancerous tissue can contribute an additional non-invasive, in vivo and in vitro diagnostic tool.

Alteration of Dentin-Enamel Mechanical Properties Due to Dental Whitening Treatments

PubMed Central

Zimmerman, B.; Datko, L.; Cupelli, M.; Alapati, S.; Dean, D.; Kennedy, M.

2010-01-01

The mechanical properties of dentin and enamel affect the reliability and wear properties of a tooth. This study investigated the influence of clinical dental treatments and procedures, such as whitening treatments or etching prior to restorative procedures. Both autoclaved and non-autoclaved teeth were studied in order to allow for both comparison with published values and improved clinical relevance. Nanoindentation analysis with the Oliver-Pharr model provided elastic modulus and hardness across the dentin-enamel junction (DEJ). Large increases were observed in the elastic modulus of enamel in teeth that had been autoclaved (52.0GPa versus 113.4GPa), while smaller increases were observed in the dentin (17.9GPa versus 27.9GPa). Likewise, there was an increase in the hardness of enamel (2.0GPa versus 4.3GPa) and dentin (0.5GPa versus 0.7GPa) with autoclaving. These changes suggested that the range of elastic modulus and hardness values previously reported in literature may be partially due to the sterilization procedures. Treatment of the exterior of non-autoclaved teeth with Crest Whitestrips™, Opalescence™ or UltraEtch™ caused changes in the mechanical properties of both the enamel and dentin. Those treated with Crest Whitestrips™ showed a reduction in the elastic modulus of enamel (55.3GPa to 32.7GPa) and increase in the elastic modulus of dentin (17.2GPa to 24.3GPa). Opalescence™ treatments did not significantly affect the enamel properties, but did result in a decrease in modulus of dentin (18.5GPa to 15.1GPa). Additionally, as expected, UltraEtch™ treatment decreased the modulus and hardness of enamel (48.7GPa to 38.0GPa and 1.9GPa to 1.5GPa, respectively) and dentin (21.4GPa to 15.0GPa and 1.9GPa to 1.5GPa, respectively). Changes in the mechanical properties were linked to altered protein concentration within the tooth, as evidenced by fluorescence microscopy and Fourier transform infrared spectroscopy. PMID:20346902

Combining AFM and Acoustic Probes to Reveal Changes in the Elastic Stiffness Tensor of Living Cells

PubMed Central

Nijenhuis, Nadja; Zhao, Xuegen; Carisey, Alex; Ballestrem, Christoph; Derby, Brian

2014-01-01

Knowledge of how the elastic stiffness of a cell affects its communication with its environment is of fundamental importance for the understanding of tissue integrity in health and disease. For stiffness measurements, it has been customary to quote a single parameter quantity, e.g., Young’s modulus, rather than the minimum of two terms of the stiffness tensor required by elasticity theory. In this study, we use two independent methods (acoustic microscopy and atomic force microscopy nanoindentation) to characterize the elastic properties of a cell and thus determine two independent elastic constants. This allows us to explore in detail how the mechanical properties of cells change in response to signaling pathways that are known to regulate the cell’s cytoskeleton. In particular, we demonstrate that altering the tensioning of actin filaments in NIH3T3 cells has a strong influence on the cell's shear modulus but leaves its bulk modulus unchanged. In contrast, altering the polymerization state of actin filaments influences bulk and shear modulus in a similar manner. In addition, we can use the data to directly determine the Poisson ratio of a cell and show that in all cases studied, it is less than, but very close to, 0.5 in value. PMID:25296302

Bending elasticity of lipid membranes in presence of beta 2 glycoprotein I in the surrounding solution

NASA Astrophysics Data System (ADS)

Pavlič, J. I.; Genova, J.; Zheliaskova, A.; Iglič, A.; Mitov, M. D.

2010-11-01

Thermally induced shape fluctuations of giant quasi-spherical lipid vesicles are used to study the bending elasticity modulus kc of a phospholipid (PHLP) membranes in presence of beta 2 glycoprotein I (β2-GPI) in the aqueous solution which surrounds the vesicle's membrane. The bending elastic modulus kc of PHLP - protein membrane was obtained for different mass concentrations of β2-GPI for pure neutral SOPC membranes and for mixed SOPC: Cardiolipin negatively charged membranes. The experimental results for the bending elastic modulus kc of the PHLP membranes does not show dependence on the concentration of β2-GPI in the range from 5.5 to 55 μg/ml, when β2-GPI is present in the aqueous solution surrounding the vesicle's membrane. Obtained results are in good agreement with predictions, based on different experiments, explaining the mechanism of binding of β2-GPI to neutral membranes.

Ultrasound Shear Wave Simulation of Breast Tumor Using Nonlinear Tissue Elasticity

PubMed Central

Park, Dae Woo

2016-01-01

Shear wave elasticity imaging (SWEI) can assess the elasticity of tissues, but the shear modulus estimated in SWEI is often less sensitive to a subtle change of the stiffness that produces only small mechanical contrast to the background tissues. Because most soft tissues exhibit mechanical nonlinearity that differs in tissue types, mechanical contrast can be enhanced if the tissues are compressed. In this study, a finite element- (FE-) based simulation was performed for a breast tissue model, which consists of a circular (D: 10 mm, hard) tumor and surrounding tissue (soft). The SWEI was performed with 0% to 30% compression of the breast tissue model. The shear modulus of the tumor exhibited noticeably high nonlinearity compared to soft background tissue above 10% overall applied compression. As a result, the elastic modulus contrast of the tumor to the surrounding tissue was increased from 0.46 at 0% compression to 1.45 at 30% compression. PMID:27293476

Effect of ripples on the finite temperature elastic properties of hexagonal boron nitride using strain-fluctuation method

NASA Astrophysics Data System (ADS)

Thomas, Siby; Ajith, K. M.; Valsakumar, M. C.

2017-11-01

This work intents to put forth the results of a classical molecular dynamics study to investigate the temperature dependent elastic constants of monolayer hexagonal boron nitride (h-BN) between 100 and 1000 K for the first time using strain fluctuation method. The temperature dependence of out-of-plane fluctuations (ripples) is quantified and is explained using continuum theory of membranes. At low temperatures, negative in-plane thermal expansion is observed and at high temperatures, a transition to positive thermal expansion has been observed due to the presence of thermally excited ripples. The decrease of Young's modulus, bulk modulus, shear modulus and Poisson's ratio with increase in temperature has been analyzed. The thermal rippling in h-BN leads to strong anharmonic behaviour that causes large deviation from the isotropic elasticity. A detailed study shows that the strong thermal rippling in large systems is also responsible for the softening of elastic constants in h-BN. From the determined values of elastic constants and elastic moduli, it has been elucidated that 2D h-BN sheets meet the Born's mechanical stability criterion in the investigated temperature range. The variation of longitudinal and shear velocities with temperature is also calculated from the computed values of elastic constants and elastic moduli.

Relationship between mechanical properties of one-step self-etch adhesives and water sorption.

PubMed

Hosaka, Keiichi; Nakajima, Masatoshi; Takahashi, Masahiro; Itoh, Shima; Ikeda, Masaomi; Tagami, Junji; Pashley, David H

2010-04-01

The purpose of this study was to evaluate the relationship between changes in the modulus of elasticity and ultimate tensile strength of one-step self-etch adhesives, and their degree of water sorption. Five one-step self-etch adhesives, Xeno IV (Dentsply Caulk), G Bond (GC Corp.), Clearfil S3 Bond (Kuraray Medical Inc.), Bond Force (Tokuyama Dental Corp.), and One-Up Bond F Plus (Tokuyama Dental Corp.) were used. Ten dumbelled-shaped polymers of each adhesive were used to obtain the modulus of elasticity by the three-point flexural bending test and the ultimate tensile strength by microtensile testing. The modulus of elasticity and the ultimate tensile strength were measured in both dry and wet conditions before/after immersion in water for 24h. Water sorption was measured, using a modification of the ISO-4049 standard. Each result of the modulus of elasticity and ultimate tensile strength was statistically analyzed using a two-way ANOVA and the result of water sorption was statistically analyzed using a one-way ANOVA. Regression analyses were used to determine the correlations between the modulus of elasticity and the ultimate tensile strength in dry or wet states, and also the percent decrease in these properties before/after immersion of water vs. water sorption. In the dry state, the moduli of elasticity of the five adhesive polymers varied from 948 to 1530 MPa, while the ultimate tensile strengths varied from 24.4 to 61.5 MPa. The wet specimens gave much lower moduli of elasticity (from 584 to 1073 MPa) and ultimate tensile strengths (from 16.5 to 35.0 MPa). Water sorption varied from 32.1 to 105.8 g mm(-3). The moduli of elasticity and ultimate tensile strengths of the adhesives fell significantly after water-storage. Water sorption depended on the constituents of the adhesive systems. The percent decreases in the ultimate tensile strengths of the adhesives were related to water sorption, while the percent reductions in the moduli of elasticity of the adhesives were not related to water sorption. Copyright (c) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Standardizing lightweight deflectometer modulus measurements for compaction quality assurance : research summary.

DOT National Transportation Integrated Search

2017-09-01

The mechanistic-empirical pavement design method requires the elastic resilient modulus as the key input for characterization of geomaterials. Current density-based QA procedures do not measure resilient modulus. Additionally, the density-based metho...

Elastic and thermal expansion asymmetry in dense molecular materials.

PubMed

Burg, Joseph A; Dauskardt, Reinhold H

2016-09-01

The elastic modulus and coefficient of thermal expansion are fundamental properties of elastically stiff molecular materials and are assumed to be the same (symmetric) under both tension and compression loading. We show that molecular materials can have a marked asymmetric elastic modulus and coefficient of thermal expansion that are inherently related to terminal chemical groups that limit molecular network connectivity. In compression, terminal groups sterically interact to stiffen the network, whereas in tension they interact less and disconnect the network. The existence of asymmetric elastic and thermal expansion behaviour has fundamental implications for computational approaches to molecular materials modelling and practical implications on the thermomechanical strains and associated elastic stresses. We develop a design space to control the degree of elastic asymmetry in molecular materials, a vital step towards understanding their integration into device technologies.

Mechanical properties of dental tissues in dolphins (Cetacea: Delphinoidea and Inioidea).

PubMed

Loch, Carolina; Swain, Michael V; van Vuuren, Ludwig Jansen; Kieser, Jules A; Fordyce, R Ewan

2013-07-01

(1) Mammalian teeth play a major role in food acquisition and processing. While most mammals are heterodont and masticate their food, dolphins are homodont with simplified tooth morphology and negligible mastication. Understanding mechanical properties of dental tissues in dolphins is fundamental to elucidate the functional morphology and biomechanics of their feeding apparatus. This paper aims to study the hardness and elastic modulus of enamel and dentine in dolphins. (2) Teeth of 10 extant species (Inioidea and Delphinoidea) were longitudinally sectioned, polished and mounted in a UMIS nanoindenter. Indentations were performed from dentine to outer enamel. Hardness and elastic modulus were calculated using the Oliver-Pharr method. (3) Mean values of hardness and elastic modulus were similar on buccal and lingual surfaces. While dentine hardness was statistically similar among species, enamel hardness varied from 3.86GPa (±0.4) in Steno bredanensis (rough-toothed dolphin) to 2.36GPa (±0.38) in Pontoporia blainvillei (franciscana). For most species, there was a gradational increase in hardness values from inner to outer enamel. Enamel and dentine elastic modulus values clearly differed among species. In enamel, it ranged from 69.32GPa (±4.08) in the rough-toothed dolphin to 13.51GPa (±2.80) in Stenella coeruleoalba (striped dolphin). For most species, elastic modulus values were highest at inner and outer enamel. (4) Differences in mechanical properties between species, and within the enamel of each species, suggest functional implications and influence of ultrastructural arrangement and chemical composition. Copyright © 2012 Elsevier Ltd. All rights reserved.

Diameter effect on stress-wave evaluation of modulus of elasticity of logs

Treesearch

Xiping Wang; Robert J. Ross; Brian K. Brashaw; John Punches; John R. Erickson; John W. Forsman; Roy E. Pellerin

2004-01-01

Recent studies on nondestructive evaluation (NDE) of logs have shown that a longitudinal stress-wave method can be used to nondestructively evaluate the modulus of elasticity (MOE) of logs. A strong relationship has been found between stress-wave MOE and static MOE of logs, but a significant deviation was observed between stress-wave and static values. The objective of...

Prediction of the elastic modulus of wood flour/kenaf fibre/polypropylene hybrid composites

Treesearch

Jamal Mirbagheri; Mehdi Tajvidi; Ismaeil Ghasemi; John C. Hermanson

2007-01-01

The prediction of the elastic modulus of short natural fibre hybrid composites has been investigated by using the properties of the pure composites through the rule of hybrid mixtures (RoHM) equation. In this equation, a hybrid natural fibre composite assumed as a system consisting of two separate single systems, namely particle/polymer and short-fibre/polymer systems...

Diameter effect on stress-wave evaluation of modulus of elasticity of logs

Treesearch

Xiping Wang; Robert J. Ross; Brian K. Brashaw; John R. Erickson; John W. Forsman; Roy Pellerin

2003-01-01

Recent studies on nondestructive evaluation (NDE) of logs have shown that a longitudinal stress-wave method can be used to nondestructively evaluate the modulus of elasticity (MOE) of logs. A strong relationship has been found between stress-wave MOE and static MOE of logs, but a significant deviation was observed between stress-wave and static values. The objective of...

Development of a bending stiffness model for wet process fiberboard

Treesearch

Chris Turk; John F. Hunt

2007-01-01

In traditional mechanics of materials, the stiffness of a beam or plate in bending is described by its cross-sectional shape as well as its material properties, primarily the modulus of elasticity. Previous work at the USDA Forest Products Laboratory, Madison, Wisconsin, has shown that modulus of elasticity has a strong correlation to the density of the fiberboard....

[Assessment of plantar fasciitis using shear wave elastography].

PubMed

Zhang, Lining; Wan, Wenbo; Zhang, Lihai; Xiao, Hongyu; Luo, Yukun; Fei, Xiang; Zheng, Zhixin; Tang, Peifu

2014-02-01

To assess the stiffness and thickness of the plantar fascia using shear wave elastography (SWE) in healthy volunteers of different ages and in patients with plantar fasciitis. The bilateral feet of 30 healthy volunteers and 23 patients with plantar fasciitis were examined with SWE. The plantar fascia thickness and elasticity modulus value were measured at the insertion of the calcaneus and at 1 cm from the insertion. The elderly volunteers had a significantly greater plantar fascia thickness measured using conventional ultrasound (P=0.005) and a significantly lower elasticity modulus value than the young volunteers (P=0.000). The patients with fasciitis had a significantly greater plantar fascia thickness (P=0.001) and a lower elasticity modulus value than the elderly volunteers (P=0.000). The elasticity modulus value was significantly lower at the calcaneus insertion than at 1 cm from the insertion in patients with fasciitis (P=0.000) but showed no significantly difference between the two points in the elderly or young volunteers (P=0.172, P=0.126). SWE allows quantitative assessment of the stiffness of the plantar fascia, which decreases with aging and in patients with plantar fasciitis.

Elastohydrodynamics of elliptical contacts for materials of low elastic modulus

NASA Technical Reports Server (NTRS)

Hamrock, B. J.; Dowson, D.

1983-01-01

The influence of the ellipticity parameter k and the dimensionless speed U, load W, and materials G parameters on minimum film thickness for materials of low elastic modulus was investigated. The ellipticity parameter was varied from 1 (a ball-on-plane configuration) to 12 (a configuration approaching a line contact); U and W were each varied by one order of magnitude. Seventeen cases were used to generate the minimum- and central-film-thickness relations. The influence of lubricant starvation on minimum film thickness in starved elliptical, elastohydrodynamic configurations was also investigated for materials of low elastic modulus. Lubricant starvation was studied simply by moving the inlet boundary closer to the center of the conjunction in the numerical solutions. Contour plots of pressure and film thickness in and around the contact were presented for both fully flooded and starved lubrication conditions. It is evident from these figures that the inlet pressure contours become less circular and closer to the edge of the Hertzian contact zone and that the film thickness decreases substantially as the serverity of starvation increases. The results presented reveal the essential features of both fully flooded and starved, elliptical, elastohydrodynamic conjunctions for materials of low elastic modulus.

Freeze-Thaw Durability of Air-Entrained Concrete

PubMed Central

Shang, Huai-Shuai; Yi, Ting-Hua

2013-01-01

One of the most damaging actions affecting concrete is the abrupt temperature change (freeze-thaw cycles). The types of deterioration of concrete structures by cyclic freeze-thaw can be largely classified into surface scaling (characterized by the weight loss) and internal crack growth (characterized by the loss of dynamic modulus of elasticity). The present study explored the durability of concrete made with air-entraining agent subjected to 0, 100, 200, 300, and 400 cycles of freeze-thaw. The experimental study of C20, C25, C30, C40, and C50 air-entrained concrete specimens was completed according to “the test method of long-term and durability on ordinary concrete” GB/T 50082-2009. The dynamic modulus of elasticity and weight loss of specimens were measured after different cycles of freeze-thaw. The influence of freeze-thaw cycles on the relative dynamic modulus of elasticity and weight loss was analyzed. The findings showed that the dynamic modulus of elasticity and weight decreased as the freeze-thaw cycles were repeated. They revealed that the C30, C40, and C50 air-entrained concrete was still durable after 300 cycles of freeze-thaw according to the experimental results. PMID:23576906

Freeze-thaw durability of air-entrained concrete.

PubMed

Shang, Huai-Shuai; Yi, Ting-Hua

2013-01-01

One of the most damaging actions affecting concrete is the abrupt temperature change (freeze-thaw cycles). The types of deterioration of concrete structures by cyclic freeze-thaw can be largely classified into surface scaling (characterized by the weight loss) and internal crack growth (characterized by the loss of dynamic modulus of elasticity). The present study explored the durability of concrete made with air-entraining agent subjected to 0, 100, 200, 300, and 400 cycles of freeze-thaw. The experimental study of C20, C25, C30, C40, and C50 air-entrained concrete specimens was completed according to "the test method of long-term and durability on ordinary concrete" GB/T 50082-2009. The dynamic modulus of elasticity and weight loss of specimens were measured after different cycles of freeze-thaw. The influence of freeze-thaw cycles on the relative dynamic modulus of elasticity and weight loss was analyzed. The findings showed that the dynamic modulus of elasticity and weight decreased as the freeze-thaw cycles were repeated. They revealed that the C30, C40, and C50 air-entrained concrete was still durable after 300 cycles of freeze-thaw according to the experimental results.

Optimization of flexible substrate by gradient elastic modulus design for performance improvement of flexible electronic devices

NASA Astrophysics Data System (ADS)

Xia, Minggang; Liang, Chunping; Hu, Ruixue; Cheng, Zhaofang; Liu, Shiru; Zhang, Shengli

2018-05-01

It is imperative and highly desirable to buffer the stress in flexible electronic devices. In this study, we designed and fabricated lamellate poly(dimethylsiloxane) (PDMS) samples with gradient elastic moduli, motivated by the protection of the pomelo pulp by its skin, followed by the measurements of their elastic moduli. We demonstrated that the electrical and fatigue performances of a Ag-nanowire thin film device on the PDMS substrate with a gradient elastic modulus are significantly better than those of a device on a substrate with a monolayer PDMS. This study provides a robust scheme to effectively protect flexible electronic devices.

Tensile properties of the human glenoid labrum

PubMed Central

Smith, C D; Masouros, S D; Hill, A M; Wallace, A L; Amis, A A; Bull, A M J

2008-01-01

Human fresh-frozen cadaveric glenoid labrae from 16 donors were harvested and ten of these had no gross degeneration. These ten were divided into eight equal circumferential sections. Each section was cut to produce test-samples from the core layer with a cross-section of 1 × 1 mm. Tensile testing was performed within a controlled environment unit at 37 ± 1 °C and 100% relative humidity. Each test-sample was precycled to a quasi-static state to alleviate the effects of deep-freezing, prior to final testing. The tangent modulus was calculated for each test-sample before and after a 5-min period of stress relaxation and at yield. The mean elastic modulus and yield stress of the glenoid labrum were 22.8 ± 11.4 and 2.5 ± 2.1 MPa, respectively. The anterosuperior portion had a lower elastic modulus and lower yield stress than the inferior portion (both P < 0.02). The pre-stress relaxation tangent modulus was significantly lower than the post-stress relaxation tangent modulus for all portions of the labrum. The glenoid labrum has similar tensile material properties to articular cartilage. Its elastic modulus varies around its circumference. This suggests that the labrum may encounter different forces at different positions. PMID:18031481

How to characterize a nonlinear elastic material? A review on nonlinear constitutive parameters in isotropic finite elasticity

PubMed Central

2017-01-01

The mechanical response of a homogeneous isotropic linearly elastic material can be fully characterized by two physical constants, the Young’s modulus and the Poisson’s ratio, which can be derived by simple tensile experiments. Any other linear elastic parameter can be obtained from these two constants. By contrast, the physical responses of nonlinear elastic materials are generally described by parameters which are scalar functions of the deformation, and their particular choice is not always clear. Here, we review in a unified theoretical framework several nonlinear constitutive parameters, including the stretch modulus, the shear modulus and the Poisson function, that are defined for homogeneous isotropic hyperelastic materials and are measurable under axial or shear experimental tests. These parameters represent changes in the material properties as the deformation progresses, and can be identified with their linear equivalent when the deformations are small. Universal relations between certain of these parameters are further established, and then used to quantify nonlinear elastic responses in several hyperelastic models for rubber, soft tissue and foams. The general parameters identified here can also be viewed as a flexible basis for coupling elastic responses in multi-scale processes, where an open challenge is the transfer of meaningful information between scales. PMID:29225507

A theoretical approach of the relationships between collagen content, collagen cross-links and meat tenderness.

PubMed

Lepetit, J

2007-05-01

This work concerns the relationship between meat tenderness and the rubber-like properties, i.e. pressure and elastic modulus, that endomysium and perimysium connective tissues develop when meat has been heated to a temperature above which collagen contracts. For rest length meats with similar intramuscular connective tissue morphology, and which are at the same ageing state and pH, the elastic modulus of the collagenous fraction of connective tissues is approximately proportional to the total number of collagen cross-links present per volume of meat. Calculations from various published experiments concerned with the effect on tenderness of muscle type, animal age, type, and sex from different species show that this modulus follows most of the variations of meat toughness. Moreover, the proportionality between the increase in this elastic modulus and the increase in meat toughness approaches unity in situations where toughness mainly depends on connective tissues. This work demonstrates the decisive role of rubber-like properties of connective tissues in meat tenderness variations.

Design and Control of a Micro/Nano Load Stage for In-Situ AFM Observation and Nanoscale Structural and Mechanical Characterization of MWCNT-Epoxy Composites

NASA Astrophysics Data System (ADS)

Leininger, Wyatt Christopher

Nanomaterial composites hold improvement potential for many materials. Improvements arise through known material behaviors and unique nanoscale effects to improve performance in areas including elastic modulus and damping as well as various processes, and products. Review of research spurred development of a load-stage. The load stage could be used independently, or in conjunction with an AFM to investigate bulk and nanoscale material mechanics. The effect of MWCNT content on structural damping, elastic modulus, toughness, loss modulus, and glass transition temperature was investigated using the load stage, AMF, and DMA. Initial investigation showed elastic modulus increased 23% with 1wt.% MWCNT versus pure epoxy and in-situ imaging observed micro/nanoscale deformation. Dynamic capabilities of the load stage were investigated as a method to achieve higher stress than available through DMA. The system showed energy dissipation across all reinforce levels, with 480% peak for the 1wt.% MWCNT material vs. the neat epoxy at 1Hz.

Ab Initio Study of Electronic Structure, Elastic and Transport Properties of Fluoroperovskite LiBeF3

NASA Astrophysics Data System (ADS)

Benmhidi, H.; Rached, H.; Rached, D.; Benkabou, M.

2017-04-01

The aim of this work is to investigate the electronic, mechanical, and transport properties of the fluoroperovskite compound LiBeF3 by first-principles calculations using the full-potential linear muffin-tin orbital method based on density functional theory within the local density approximation. The independent elastic constants and related mechanical properties including the bulk modulus ( B), shear modulus ( G), Young's modulus ( E), and Poisson's ratio ( ν) have been studied, yielding the elastic moduli, shear wave velocities, and Debye temperature. According to the electronic properties, this compound is an indirect-bandgap material, in good agreement with available theoretical data. The electron effective mass, hole effective mass, and energy bandgaps with their volume and pressure dependence are investigated for the first time.

Comparative study on the mechanical property of silk thread from cocoons of Bombyx mori L.

PubMed

Iizuka, E; Hachimori, A; Abe, K; Sunohara, M; Hiraide, Y; Ueyama, A; Kamo, K; Fujiwara, T; Nakamura, F; Uno, T

1983-01-01

Specimens of bave (undegummed silk thread) were collected from cocoons of various origins of parent silkworm races, such as Japanese, Chinese, European, Korean and tropical origins, and from as many races as possible. An apparatus was set up to measure the dynamic elastic modulus of these specimens. In all the categories of the races tested, the elastic modulus was linearly related to the size of bave, regardless of the portion of cocoon layer from which the specimens were taken. This correlation was concluded to be universal to the silk thread of Bombyx mori L. species; however, values of the regression coefficient and of the elastic modulus were susceptible to the origin of silkworm races, depending on whether they were native or improved.

Loss tangent and complex modulus estimated by acoustic radiation force creep and shear wave dispersion

PubMed Central

Amador, Carolina; Urban, Matthew W; Chen, Shigao; Greenleaf, James F

2012-01-01

Elasticity imaging methods have been used to study tissue mechanical properties and have demonstrated that tissue elasticity changes with disease state. In current shear wave elasticity imaging methods typically only shear wave speed is measured and rheological models, e.g., Kelvin-Voigt, Maxwell and Standard Linear Solid, are used to solve for tissue mechanical properties such as the shear viscoelastic complex modulus. This paper presents a method to quantify viscoelastic material properties in a model-independent way by estimating the complex shear elastic modulus over a wide frequency range using time-dependent creep response induced by acoustic radiation force. This radiation force induced creep (RFIC) method uses a conversion formula that is the analytic solution of a constitutive equation. The proposed method in combination with Shearwave Dispersion Ultrasound Vibrometry (SDUV) is used to measure the complex modulus so that knowledge of the applied radiation force magnitude is not necessary. The conversion formula is shown to be sensitive to sampling frequency and the first reliable measure in time according to numerical simulations using the Kelvin-Voigt model creep strain and compliance. Representative model-free shear complex moduli from homogeneous tissue mimicking phantoms and one excised swine kidney were obtained. This work proposes a novel model-free ultrasound-based elasticity method that does not require a rheological model with associated fitting requirements. PMID:22345425

Loss tangent and complex modulus estimated by acoustic radiation force creep and shear wave dispersion.

PubMed

Amador, Carolina; Urban, Matthew W; Chen, Shigao; Greenleaf, James F

2012-03-07

Elasticity imaging methods have been used to study tissue mechanical properties and have demonstrated that tissue elasticity changes with disease state. In current shear wave elasticity imaging methods typically only shear wave speed is measured and rheological models, e.g. Kelvin-Voigt, Maxwell and Standard Linear Solid, are used to solve for tissue mechanical properties such as the shear viscoelastic complex modulus. This paper presents a method to quantify viscoelastic material properties in a model-independent way by estimating the complex shear elastic modulus over a wide frequency range using time-dependent creep response induced by acoustic radiation force. This radiation force induced creep method uses a conversion formula that is the analytic solution of a constitutive equation. The proposed method in combination with shearwave dispersion ultrasound vibrometry is used to measure the complex modulus so that knowledge of the applied radiation force magnitude is not necessary. The conversion formula is shown to be sensitive to sampling frequency and the first reliable measure in time according to numerical simulations using the Kelvin-Voigt model creep strain and compliance. Representative model-free shear complex moduli from homogeneous tissue mimicking phantoms and one excised swine kidney were obtained. This work proposes a novel model-free ultrasound-based elasticity method that does not require a rheological model with associated fitting requirements.

Dynamics of hydrated mucopolysaccharides in cartilaginous tissues treated by laser radiation

NASA Astrophysics Data System (ADS)

Omelchenko, Alexander I.; Sobol, Emil N.; Ignatieva, Natalia Y.; Lunin, Valerii V.; Jumel, Kornelia; Harding, Stephen E.; Jones, Nicholas

2001-05-01

Dynamic mechanical properties of hydrated mucopolysaccharides have been studied in heated solutions by means of molecular hydrodynamic and acoustic techniques. These experiments model the thermal condition used for laser reshaping of cartilage. It has been shown that elastic modulus and internal friction depends on concentration of chondroitine sulphate in the solution and temperature. Maximum of internal friction was revealed at about 40 degree(s)C that corresponds to temperature of breakdown of hydrophobic bonds. Temperature dependence of internal friction manifests structural changes in polysaccharides molecules under laser heating.

Insight into the structural, electronic, elastic and optical properties of the alkali hydride compounds, XH (X = Rb and Cs)

NASA Astrophysics Data System (ADS)

Jaradat, Raed; Abu-Jafar, Mohammed; Abdelraziq, Issam; Mousa, Ahmad; Ouahrani, Tarik; Khenata, Rabah

2018-04-01

The equilibrium structural parameters, electronic and optical properties of the alkali hydrides RbH and CsH compounds in rock-salt (RS) and cesium chloride (CsCl) structures have been studied using the full-potential linearized augmented plane-wave (FP-LAPW) method. Wu and Cohen generalized gradient approximation (WC-GGA) was used for the exchange-correlation potential to compute the equilibrium structural parameters, such as the lattice constant (a0), the bulk modulus (B) and bulk modulus first order pressure derivative (B'). In addition to the WC-GGA, the modified Becke Johnson (mBJ) scheme has been also used to overcome the underestimation of the band gap energies. RbH and CsH compounds are found to be semiconductors (wide energy-band gap) using the WC-GGA method, while they are insulators using the mBJ-GGA method. Elastic constants, mechanical and thermodynamic properties were obtained by using the IRelast package. RbH and CsH compounds at ambient pressure are mechanically stable in RS and CsCl structures; they satisfy the Born mechanical stability criteria. Elastic constants (Cij), bulk modulus (B), shear modulus (S) and Debye temperatures (θD) of RbH and CsH compounds decrease as the alkali radius increases. The RS structure of these compounds at ambient conditions is mechanically stronger than CsCl structure. RbH and CsH in RS and CsCl structures are suitable as dielectric compounds. The wide direct energy band gap for these compounds make them promising compounds for optoelectronic UV device applications. Both RbH and CsH have a wide absorption region, on the other hand RbH absorption is very huge compared to the CsH absorption, RbH is an excellent absorbent material, maximum absorption regions are located in the middle ultraviolet (MUV) region and far ultraviolet (FUV) region. The absorption coefficient α (w), imaginary part of the dielectric constant ɛ2(w) and the extinction coefficient k(w) vary in the same way. The present calculated results are in good agreement with the experimental data, indicating the high accuracy of the performed calculations and reliability of the obtained results.

Frequency characteristics of vibration generated by dual acoustic radiation force for estimating viscoelastic properties of biological tissues

NASA Astrophysics Data System (ADS)

Watanabe, Ryoichi; Arakawa, Mototaka; Kanai, Hiroshi

2018-07-01

We proposed a new method for estimating the viscoelastic property of the local region of a sample. The viscoelastic parameters of the phantoms simulating the biological tissues were quantitatively estimated by analyzing the frequency characteristics of displacement generated by acoustic excitation. The samples were locally strained by irradiating them with the ultrasound simultaneously generated from two point-focusing transducers by applying the sum of two signals with slightly different frequencies of approximately 1 MHz. The surface of a phantom was excited in the frequency range of 20–2,000 Hz, and its displacement was measured. The frequency dependence of the acceleration provided by the acoustic radiation force was also measured. From these results, we determined the frequency characteristics of the transfer function from the stress to the strain and estimated the ratio of the elastic modulus to the viscosity modulus (K/η) by fitting the data to the Maxwell model. Moreover, the elastic modulus K was separately estimated from the measured sound velocity and density of the phantom, and the viscosity modulus η was evaluated by substituting the estimated elastic modulus into the obtained K/η ratio.

A highly aromatic and sulfonated ionomer for high elastic modulus ionic polymer membrane micro-actuators

NASA Astrophysics Data System (ADS)

Hatipoglu, Gokhan; Liu, Yang; Zhao, Ran; Yoonessi, Mitra; Tigelaar, Dean M.; Tadigadapa, Srinivas; Zhang, Q. M.

2012-05-01

A high modulus, sulfonated ionomer synthesized from 4,6-bis(4-hydroxyphenyl)-N,N-diphenyl-1,3,5-triazin-2-amine and 4,4‧-biphenol with bis(4-fluorophenyl)sulfone (DPA-PS:BP) is investigated for ionic polymer actuators. The uniqueness of DPA-PS:BP is that it can have a high ionic liquid (IL) uptake and consequently generates a high intrinsic strain response, which is >1.1% under 1.6 V while maintaining a high elastic modulus (i.e. 600 MPa for 65 vol% IL uptake). Moreover, such a high modulus of the active ionomer, originating from the highly aromatic backbone and side-chain-free structure, allows for the fabrication of free-standing thin film micro-actuators (down to 5 µm thickness) via the solution cast method and focused-ion-beam milling, which exhibits a much higher bending actuation, i.e. 43 µm tip displacement and 180 kPa blocking stress for a 200 µm long and 5 µm thick cantilever actuator, compared with the ionic actuators based on traditional ionomers such as Nafion, which has a much lower elastic modulus (50 MPa) and actuation strain.

Dose-dependent collagen cross-linking of rabbit scleral tissue by blue light and riboflavin treatment probed by dynamic shear rheology.

PubMed

Schuldt, Carsten; Karl, Anett; Körber, Nicole; Koch, Christian; Liu, Qing; Fritsch, Anatol W; Reichenbach, Andreas; Wiedemann, Peter; Käs, Josef A; Francke, Mike; Iseli, Hans Peter

2015-08-01

To determine the visco-elastic properties of isolated rabbit scleral tissue and dose-dependent biomechanical and morphological changes after collagen cross-linking by riboflavin/blue light treatment. Scleral patches from 87 adult albino rabbit eyes were examined by dynamic shear rheology. Scleral patches were treated by riboflavin and different intensities of blue light (450 nm), and the impact on the visco-elastic properties was determined by various rheological test regimes. The relative elastic modulus was calculated from non-treated and corresponding treated scleral patches, and treatments with different blue light intensities were compared. Shear rheology enables us to study the material properties of scleral tissue within physiological relevant parameters. Cross-linking treatment increased the viscous as well as the elastic modulus and changed the ratio of the elastic versus viscous proportion in scleral tissue. Constant riboflavin application combined with different blue light intensities from 12 mW/cm(2) up to 100 mW/cm(2) increased the relative elastic modulus of scleral tissue by factors up to 1.8. Further enhancement of the applied light intensity caused a decline of the relative elastic modulus. This might be due to destructive changes of the collagen bundle structure at larger light intensities, as observed by histological examination. Collagen cross-linking by riboflavin/blue light application increases the biomechanical stiffness of the sclera in a dose-dependent manner up to certain light intensities. Therefore, this treatment might be a suitable therapeutic approach to stabilize the biomechanical properties of scleral tissue in cases of pathological eye expansion. © 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Genetic variation in basic density and modulus of elasticity of coastal Douglas-fir.

Treesearch

G.R. Johnson; B.L. Gartner

2006-01-01

Douglas-fir trees from 39 open-pollinated families at four test locations were assessed to estimate heritability of modulus of elasticity (MOE) and basic density. Heritability estimates of MOE (across-site h = 0.55) were larger than those for total height (0.15) and diameter at breast height (DBH; 0.29), and similar to those for density (0.59)....

Modulus of elasticity loss as a rapid indicator of rot-fungal attack on untreated and preservative-treated wood in laboratory tests

Treesearch

Xingxia Ma; Grant T. Kirker; Carol A. Clausen; Mingliang Jiang; Haibin Zhou

2017-01-01

The modulus of elasticity (MOE) of wood is a sensitive indicator of rotfungal attack. To develop an alternative method of rapid assessment of fungal decay in the laboratory, changes in static MOE of untreated and preservative-treated wood were measured during exposure to the brownrot fungus, Gloeophyllum trabeum, and the white-rot fungus, Trametes...

Visualising elastic anisotropy: theoretical background and computational implementation

NASA Astrophysics Data System (ADS)

Nordmann, J.; Aßmus, M.; Altenbach, H.

2018-02-01

In this article, we present the technical realisation for visualisations of characteristic parameters of the fourth-order elasticity tensor, which is classified by three-dimensional symmetry groups. Hereby, expressions for spatial representations of uc(Young)'s modulus and bulk modulus as well as plane representations of shear modulus and uc(Poisson)'s ratio are derived and transferred into a comprehensible form to computer algebra systems. Additionally, we present approaches for spatial representations of both latter parameters. These three- and two-dimensional representations are implemented into the software MATrix LABoratory. Exemplary representations of characteristic materials complete the present treatise.

Measurement of the Elastic Modulus of a Single Boron Nitride Nanotube

NASA Astrophysics Data System (ADS)

Chopra, Nasreen G.; Cohen, Marvin L.; Louie, Steven G.; Zettl, A.

1997-03-01

In situ transmission electron microscope (TEM) measurements of thermally-excited vibrational characteristics of boron nitride (BN) nanotubes are used to extract the elastic modulus. We find BN nanotubes to have a higher axial Young's modulus, 1.2 TPa, than any other insulating fiber. This value is consistent with theoretical predictions and confirms previous TEM observations of the high degree of crystallinity of these structures. This work was supported by the U. S. Department of Energy under contract No. DE-AC03-76-SF00098 and the Office of Naval Research, Order No. N00014-95-F-0099

Test of parameter-free local pseudopotential for the study of dynamical elastic constants - Cu as a prototype

NASA Astrophysics Data System (ADS)

Bhatia, K. G.; Vyas, S. M.; Patel, A. B.; Bhatt, N. K.; Vyas, P. R.; Gohel, V. B.

2018-05-01

Using parameter-free (first principles local) pseudopotential, in the present communication we have calculated dynamical elastic constants (C11, C12 and C44), bulk modulus (B), shear modulus (µp), Young's modulus (Y) and Poisson's ratio (σ) in long wavelength limit. Our computed results are well agreed for C44 and B with experiment and with other theoretical results obtained within framework of second order perturbation pseudopotential theory. From the present study we conclude that pseudopotential used contain s-p hybridization and no extra term is required to account core-core repulsion.

Theoretical study of phonon dispersion, elastic, mechanical and thermodynamic properties of barium chalcogenides

NASA Astrophysics Data System (ADS)

Musari, A. A.; Orukombo, S. A.

2018-03-01

Barium chalcogenides are known for their high-technological importance and great scientific interest. Detailed studies of their elastic, mechanical, dynamical and thermodynamic properties were carried out using density functional theory and plane-wave pseudo potential method within the generalized gradient approximation. The optimized lattice constants were in good agreement when compared with experimental data. The independent elastic constants, calculated from a linear fit of the computed stress-strain function, were used to determine the Young’s modulus (E), bulk modulus (B), shear modulus (G), Poisson’s ratio (σ) and Zener’s anisotropy factor (A). Also, the Debye temperature and sound velocities for barium chalcogenides were estimated from the three independent elastic constants. The calculations of phonon dispersion showed that there are no negative frequencies throughout the Brillouin zone. Hence barium chalcogenides have dynamically stable NaCl-type crystal structure. Finally, their thermodynamic properties were calculated in the temperature range of 0-1000 K and their constant-volume specific heat capacities at room-temperature were reported.

Study of phonon modes and elastic properties of Sc36Al24Co20Y20 and Gd36Al24Co20Y20 rare-earth bulk metallic glasses

NASA Astrophysics Data System (ADS)

Suthar, P. H.; Gajjar, P. N.; Thakore, B. Y.; Jani, A. R.

2013-04-01

A phonon modes and elastic properties of two different rare-earth based bulk metallic glasses Sc36Al24Co20Y20 and Gd36Al24Co20Y20 are computed using Hubbard-Beeby approach and our well established model potential. The local field correlation functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al (F) and Sarkar Sen et al (S) are employed to investigate the influence of the screening effects on the vibrational dynamics of Sc36Al24Co20Y20 and Gd36Al24Co20Y20 bulk metallic glasses. The results for bulk modulus BT, modulus of rigidity G, Poisson's ratio ξ, Young's modulus Y, Debye temperature ΘD, propagation velocity of elastic waves and dispersion curves are reported. The computed elastic properties are found to be in good agreement with experimental and other available data.

Correlating off-axis tension tests to shear modulus of wood-based panels

Treesearch

Edmond P. Saliklis; Robert H. Falk

2000-01-01

The weakness of existing relationships correlating off-axis modulus of elasticity E q to shear modulus G 12 for wood composite panels is demonstrated through presentation of extensive experimental data. A new relationship is proposed that performs better than existing equations found in the literature. This relationship can be manipulated to calculate the shear modulus...

Physical property measurements of doped cesium iodide crystals

NASA Technical Reports Server (NTRS)

Synder, R. S.; Clotfelter, W. N.

1974-01-01

Mechanical and thermal property values are reported for crystalline cesium iodide doped with sodium and thallium. Young's modulus, bulk modulus, shear modulus, and Poisson's ratio were obtained from ultrasonic measurements. Young's modulus and the samples' elastic and plastic behavior were also measured under tension and compression. Thermal expansion and thermal conductivity were the temperature dependent measurements that were made.

Alteration of dentin-enamel mechanical properties due to dental whitening treatments.

PubMed

Zimmerman, B; Datko, L; Cupelli, M; Alapati, S; Dean, D; Kennedy, M

2010-05-01

The mechanical properties of dentin and enamel affect the reliability and wear properties of a tooth. This study investigated the influence of clinical dental treatments and procedures, such as whitening treatments or etching prior to restorative procedures. Both autoclaved and non-autoclaved teeth were studied in order to allow for both comparison with published values and improved clinical relevance. Nanoindentation analysis with the Oliver-Pharr model provided elastic modulus and hardness across the dentin-enamel junction (DEJ). Large increases were observed in the elastic modulus of enamel in teeth that had been autoclaved (52.0 GPa versus 113.4 GPa), while smaller increases were observed in the dentin (17.9 GPa versus 27.9 GPa). Likewise, there was an increase in the hardness of enamel (2.0 GPa versus 4.3 GPa) and dentin (0.5 GPa versus 0.7 GPa) with autoclaving. These changes suggested that the range of elastic modulus and hardness values previously reported in the literature may be partially due to the sterilization procedures. Treatment of the exterior of non-autoclaved teeth with Crest Whitestrips, Opalescence or UltraEtch caused changes in the mechanical properties of both the enamel and dentin. Those treated with Crest Whitestrips showed a reduction in the elastic modulus of enamel (55.3 GPa to 32.7 GPa) and increase in the elastic modulus of dentin (17.2 GPa to 24.3 GPa). Opalescence treatments did not significantly affect the enamel properties, but did result in a decrease in the modulus of dentin (18.5 GPa to 15.1 GPa). Additionally, as expected, UltraEtch treatment decreased the modulus and hardness of enamel (48.7 GPa to 38.0 GPa and 1.9 GPa to 1.5 GPa, respectively) and dentin (21.4 GPa to 15.0 GPa and 1.9 GPa to 1.5 GPa, respectively). Changes in the mechanical properties were linked to altered protein concentration within the tooth, as evidenced by fluorescence microscopy and Fourier transform infrared spectroscopy. Published by Elsevier Ltd.

Acute effect and time course of extension and internal rotation stretching of the shoulder on infraspinatus muscle hardness.

PubMed

Kusano, Ken; Nishishita, Satoru; Nakamura, Masatoshi; Tanaka, Hiroki; Umehara, Jun; Ichihashi, Noriaki

2017-10-01

A decrease in flexibility of the infraspinatus muscle causes limitations in the range of shoulder motion. Static stretching (SS) is a useful method to improve muscle flexibility and joint mobility. Previous researchers investigated effective stretching methods for the infraspinatus. However, few researchers investigated the acute effect of SS on the infraspinatus muscle's flexibility. In addition, the minimum SS time required to increase the infraspinatus muscle's flexibility remains unclear. The aims of this study included investigating the acute effect of SS on the infraspinatus muscle's hardness (an index of muscle flexibility) by measuring shear elastic modulus and determining minimum SS time to decrease the infraspinatus muscle's hardness. This included measuring the effect of SS with extension and internal rotation of the shoulder on the infraspinatus muscle's hardness in 20 healthy men. Hence, shear elastic modulus of the infraspinatus was measured by ultrasonic shear wave elastography before and after every 10 seconds up to 120 seconds of SS. Two-way analysis of variance indicated a significant main effect of SS duration on shear elastic modulus. The post hoc test indicated no significant difference between shear elastic modulus after 10 seconds of SS and that before SS. However, shear elastic modulus immediately after a period ranging from 20 seconds to 120 seconds of SS was significantly lower than that before SS. The results suggested that shoulder extension and internal rotation SS effectively decreased the infraspinatus muscle's hardness. In addition, the results indicated that a period exceeding 20 seconds of SS decreased the infraspinatus muscle's hardness. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

The Value of Elastic Modulus Index as a Novel Surrogate Marker for Cardiovascular Risk Stratification by Dimensional Speckle-Tracking Carotid Ultrasonography

PubMed Central

Yoon, Ji Hyun; Cho, In-Jeong; Sung, Ji Min; Lee, Jinyong; Ryoo, Hojin; Shim, Chi Young; Hong, Geu-Ru; Chung, Namsik

2016-01-01

Background Carotid intima media thickness (CIMT) and the presence of carotid plaque have been used for risk stratification of cardiovascular disease (CVD). To date, however, the association between multi-directional functional properties of carotid artery and CVD has not been fully elucidated. We sought to explore the multi-directional mechanics of the carotid artery in relation to cardiovascular risk. Methods Four hundred one patients who underwent carotid ultrasound were enrolled between January 2010 and April 2013. A high risk of CVD was defined as more than 20% of 10-year risk based on the Framingham risk score. Using a speckle-tracking technique, the longitudinal and radial movements were analyzed in the B-mode images. Peak longitudinal and radial displacements, strain and strain rate were also measured. Beta stiffness and elastic modulus index were calculated from the radial measurements. Results Of the overall sample, 13% (52) of patients comprised the high-risk group. In multivariate logistic regression, CIMT and elastic modulus index were independently associated with a high-risk of CVD {odds ratio (OR): 1.810 [95% confidence interval (CI) 1.249–2.622] and OR: 1.767 (95% CI: 1.177–2.652); p = 0.002, 0.006, respectively}. The combination of CIMT and elastic modulus index correlated with a high-risk of CVD more so than CIMT alone. Conclusion The elastic modulus index of the carotid artery might serve as a novel surrogate marker of high-risk CVD. Measurement of the multi-directional mechanics of the carotid artery using the speckle tracking technique has potential for providing further information over conventional B-mode ultrasound for stratification of CVD risk. PMID:27721952

Elastic properties and fracture strength of quasi-isotropic graphite/epoxy composites

NASA Technical Reports Server (NTRS)

Sullivan, T. L.

1977-01-01

A research program is described which was devised to determine experimentally the elastic properties in tension and bending of quasi-isotropic laminates made from high-modulus graphite fiber and epoxy. Four laminate configurations were investigated, and determinations were made of the tensile modulus, Poisson's ratio, bending stiffness, fracture strength, and fracture strain. The measured properties are compared with those predicted by laminate theory, reasons for scatter in the experimental data are discussed, and the effect of fiber misalignment on predicted elastic tensile properties is examined. The results strongly suggest that fiber misalignment in combination with variation in fiber volume content is responsible for the scatter in both elastic constants and fracture strength.

Order-disorder effects on the elastic properties of CuMPt6 (M=Cr and Co) compounds

NASA Astrophysics Data System (ADS)

Huang, Shuo; Li, Rui-Zi; Qi, San-Tao; Chen, Bao; Shen, Jiang

2014-04-01

The elastic properties of CuMPt6 (M=Cr and Co) in disordered face-centered cubic (fcc) structure and ordered Cu3Au-type structure are studied with lattice inversion embedded-atom method. The calculated lattice constant and Debye temperature agree quite well with the comparable experimental data. The obtained formation enthalpy demonstrates that the Cu3Au-type structure is energetically more favorable. Numerical estimates of the elastic constants, bulk/shear modulus, Young's modulus, Poisson's ratio, elastic anisotropy, and Debye temperature for both compounds are performed, and the results suggest that the disordered fcc structure is much softer than the ordered Cu3Au-type structure.

Size effects on elasticity, yielding, and fracture of silver nanowires: In situ experiments

NASA Astrophysics Data System (ADS)

Zhu, Yong; Qin, Qingquan; Xu, Feng; Fan, Fengru; Ding, Yong; Zhang, Tim; Wiley, Benjamin J.; Wang, Zhong Lin

2012-01-01

This paper reports the quantitative measurement of a full spectrum of mechanical properties of fivefold twinned silver (Ag) nanowires (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 scanning electron microscope (SEM). Young's modulus, yield strength, and ultimate tensile strength all increased as the NW diameter decreased. The maximum yield strength in our tests was found to be 2.64 GPa, which is about 50 times the bulk value and close to the theoretical value of Ag in the 110 orientation. The size effect in the yield strength is mainly due to the stiffening size effect in the Young's modulus. Yield strain scales reasonably well with the NW surface area, which reveals that yielding of Ag NWs is due to dislocation nucleation from surface sources. Pronounced strain hardening was observed for most NWs in our study. The strain hardening, which has not previously been reported for NWs, is mainly attributed to the presence of internal twin boundaries.

Age-related variation in the mechanical properties of foods processed by Sapajus libidinosus.

PubMed

Chalk, Janine; Wright, Barth W; Lucas, Peter W; Schuhmacher, Katherine D; Vogel, Erin R; Fragaszy, Dorothy; Visalberghi, Elisabetta; Izar, Patrícia; Richmond, Brian G

2016-02-01

The diet of tufted capuchins (Sapajus) is characterized by annual or seasonal incorporation of mechanically protected foods. Reliance on these foods raises questions about the dietary strategies of young individuals that lack strength and experience to access these resources. Previous research has demonstrated differences between the feeding competencies of adult and juvenile tufted capuchins. Here we test the hypothesis that, compared to adults, juveniles will process foods with lower toughness and elastic moduli. We present data on variation in the toughness and elastic modulus of food tissues processed by Sapajus libidinosus during the dry season at Fazenda Boa Vista, Brazil. Food mechanical property data were collected using a portable universal mechanical tester. Results show that food tissues processed by the capuchins showed significant differences in toughness and stiffness. However, we found no relationship between an individual's age and mean or maximum food toughness or elastic modulus, indicating both juvenile and adult S. libidinosus are able to process foods of comparable properties. Although it has been suggested that juveniles avoid mechanically protected foods, age-related differences in feeding competence are not solely due to variation in food toughness or stiffness. Other factors related to food type (e.g., learning complex behavioral sequences, achieving manual dexterity, obtaining physical strength to lift stone tools, or recognizing subtle cues about food state) combined with food mechanical properties better explain variation in juvenile feeding competency. © 2015 Wiley Periodicals, Inc.

Release characteristics of reattached barnacles to non-toxic silicone coatings.

PubMed

Kim, Jongsoo; Nyren-Erickson, Erin; Stafslien, Shane; Daniels, Justin; Bahr, James; Chisholm, Bret J

2008-01-01

Release mechanisms of barnacles (Amphibalanus amphitrite or Balanus amphitrite) reattached to platinum-cured silicone coatings were studied as a function of coating thickness (210-770 microm), elastic modulus (0.08-1.3 MPa), and shear rate (2-22 microm s(-1)). It was found that the shear stress of the reattached, live barnacles necessary to remove from the silicone coatings was controlled by the combined term (E/t)(0.5) of the elastic modulus (E) and thickness (t). As the ratio of the elastic modulus to coating thickness decreased, the barnacles were more readily removed from the silicone coatings, showing a similar release behavior to pseudobarnacles (epoxy glue). The barnacle mean shear stress ranged from 0.017 to 0.055 MPa whereas the pseudobarnacle mean shear stress ranged from 0.022 to 0.095 MPa.

Adiabatic bulk modulus of elasticity for 2D liquid dusty plasmas

NASA Astrophysics Data System (ADS)

Feng, Yan; Huang, Dong; Li, Wei

2018-05-01

From the recently obtained equation of state (EOS) for two-dimensional (2D) liquid dusty plasmas, their various physical quantities have been derived analytically, such as the specific heat CV, the Grüneisen parameter, the bulk modulus of elasticity, and the isothermal compressibility. Here, the coefficient of volumetric thermal expansion αV and the relative pressure coefficient αP of 2D liquid dusty plasmas are derived from their EOS. Using the obtained CV, αV, and αP, the analytical expression of their heat capacity under constant-pressure conditions CP is obtained. Thus, the heat capacity ratio, expressed as CP/CV , is analytically achieved. Then the adiabatic bulk modulus of elasticity is derived, so that the adiabatic sound speeds are obtained. These obtained results are compared with previous findings using a different approach.

Structural, electronic, elastic, and thermodynamic properties of CaSi, Ca2Si, and CaSi2 phases from first-principles calculations

NASA Astrophysics Data System (ADS)

Li, X. D.; Li, K.; Wei, C. H.; Han, W. D.; Zhou, N. G.

2018-06-01

The structural, electronic, elastic, and thermodynamic properties of CaSi, Ca2Si, and CaSi2 are systematically investigated by using first-principles calculations method based on density functional theory (DFT). The calculated formation enthalpies and cohesive energies show that CaSi2 possesses the greatest structural stability and CaSi has the strongest alloying ability. The structural stability of the three phases is compared according to electronic structures. Further analysis on electronic structures indicates that the bonding of these phases exhibits the combinations of metallic, covalent, and ionic bonds. The elastic constants are calculated, and the bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and anisotropy factor of polycrystalline materials are deduced. Additionally, the thermodynamic properties were theoretically predicted and discussed.

Structural stability, elastic and thermodynamic properties of Au-Cu alloys from first-principles calculations

NASA Astrophysics Data System (ADS)

Kong, Ge-Xing; Ma, Xiao-Juan; Liu, Qi-Jun; Li, Yong; Liu, Zheng-Tang

2018-03-01

Using first-principles calculations method based on density functional theory (DFT) with the Perdew-Burke-Ernzerhof (PBE) implementation of the generalized gradient approximation (GGA), we investigate the structural, elastic and thermodynamic properties of gold-copper intermetallic compounds (Au-Cu ICs). The calculated lattice parameters are in excellent agreement with experimental data. The elastic constants show that all the investigated Au-Cu alloys are mechanically stable. Elastic properties, including the shear modulus, Young's modulus, Poisson's ratio and Pugh's indicator, of the intermetallic compounds are evaluated and discussed, with special attention to the remarkable anisotropy displayed by Au-Cu ICs. Thermodynamic and transport properties including the Debye temperature, thermal conductivity and melting point are predicted from the averaged sound velocity and elastic moduli, using semi-empirical formulas.

The influence of anisotropy on the core structure of Shockley partial dislocations within FCC materials

NASA Astrophysics Data System (ADS)

Szajewski, B. A.; Hunter, A.; Luscher, D. J.; Beyerlein, I. J.

2018-01-01

Both theoretical and numerical models of dislocations often necessitate the assumption of elastic isotropy to retain analytical tractability in addition to reducing computational load. As dislocation based models evolve towards physically realistic material descriptions, the assumption of elastic isotropy becomes increasingly worthy of examination. We present an analytical dislocation model for calculating the full dissociated core structure of dislocations within anisotropic face centered cubic (FCC) crystals as a function of the degree of material elastic anisotropy, two misfit energy densities on the γ-surface ({γ }{{isf}}, {γ }{{usf}}) and the remaining elastic constants. Our solution is independent of any additional features of the γ-surface. Towards this pursuit, we first demonstrate that the dependence of the anisotropic elasticity tensor on the orientation of the dislocation line within the FCC crystalline lattice is small and may be reasonably neglected for typical materials. With this approximation, explicit analytic solutions for the anisotropic elasticity tensor {B} for both nominally edge and screw dislocations within an FCC crystalline lattice are devised, and employed towards defining a set of effective isotropic elastic constants which reproduce fully anisotropic results, however do not retain the bulk modulus. Conversely, Hill averaged elastic constants which both retain the bulk modulus and reasonably approximate the dislocation core structure are employed within subsequent numerical calculations. We examine a wide range of materials within this study, and the features of each partial dislocation core are sufficiently localized that application of discrete linear elasticity accurately describes the separation of each partial dislocation core. In addition, the local features (the partial dislocation core distribution) are well described by a Peierls-Nabarro dislocation model. We develop a model for the displacement profile which depends upon two disparate dislocation length scales which describe the core structure; (i) the equilibrium stacking fault width between two Shockley partial dislocations, R eq and (ii) the maximum slip gradient, χ, of each Shockley partial dislocation. We demonstrate excellent agreement between our own analytic predictions, numerical calculations, and R eq computed directly by both ab-initio and molecular statics methods found elsewhere within the literature. The results suggest that understanding of various plastic mechanisms, e.g., cross-slip and nucleation may be augmented with the inclusion of elastic anisotropy.

Experimental and theoretical modal analysis of full-sized wood composite panels supported on four nodes

Treesearch

Cheng Guan; Houjiang Zhang; Xiping Wang; Hu Miao; Lujing Zhou; Fenglu Liu

2017-01-01

Key elastic properties of full-sized wood composite panels (WCPs) must be accurately determined not only for safety, but also serviceability demands. In this study, the modal parameters of full-sized WCPs supported on four nodes were analyzed for determining the modulus of elasticity (E) in both major and minor axes, as well as the in-plane shear modulus of panels by...

Comparison of Nondestructive Testing Methods for Evaluating No. 2 Southern Pine Lumber: Part A, Modulus of Elasticity

Treesearch

B.Z. Yang; R.D. Seale; R. Shmulsky; J. Dahlen; Xiping Wang

2015-01-01

Modulus of elasticity (MOE, or E) is one of the main quality indicators in structural lumber stress grading systems. Due to a relatively high amount of variability in contemporary sawn lumber, it is important that nondestructive evaluation technology be utilized to better discern high-E-value pieces from low-E-value pieces. The research described in this study is from...

Modeling temperature effect on dynamic modulus of elasticity of red pine (Pinus resinosa) in frozen and non-frozen states

Treesearch

Shan Gao; Xiping Wang; Lihai Wang

2015-01-01

The response of dynamic and static modulus of elasticity (MOEdyn and MOEsta) of red pine small clear wood (25.4 × 25.4 × 407 mm3) within the temperature range -40 to 40°C has been investigated. The moisture content (MC) of the specimens ranged from 0 to 118%. The MOEdyn was...

Stress wave velocity and dynamic modulus of elasticity of yellow-poplar ranging from 100 to 10 percent moisture content

Treesearch

Jody D. Gray; Shawn T. Grushecky; James P. Armstrong

2008-01-01

Moisture content has a significant impact on mechanical properties of wood. In recent years, stress wave velocity has been used as an in situ and non-destructive method for determining the stiffness of wooden elements. The objective of this study was to determine what effect moisture content has on stress wave velocity and dynamic modulus of elasticity. Results...

In Vivo Estimation of Perineal Body Properties Using Ultrasound Quasistatic Elastography in Nulliparous Women

PubMed Central

Chen, Luyun; Low, Lisa Kane; DeLancey, John OL; Ashton-Miller, James A

2015-01-01

Objective The perineal body must undergo a remarkable transformation during pregnancy to accommodate an estimated stretch ratio of over 3.3 in order to permit vaginal delivery of the fetal head. Yet measurements of perineal body elastic properties are lacking in vivo, whether in the pregnant or non-pregnant state. The objective of this study, therefore, was to develop a method for measuring perineal body elastic modulus and to test its feasibility in young nulliparous women. Methods An UltraSONIX RP500 ultrasound system was equipped with elastography software. Approximately 1 Hz free-hand sinusoidal compression loading of the perineum was used to measure the relative stiffness of the perineal body compared to that of a custom reference standoff pad with a modulus of 36.7 kPa. Measurements were made in 20 healthy nulliparous women. Four subjects were invited back for second and third visits to evaluate within- and between-visit repeatability using the coefficient of variation. Results The mean± SD elastic compression modulus of the perineal body was 28.9 ± 4.7 kPa. Within- and between-visit repeatability averaged 3.4% and 8.3%, respectively. Conclusion Ultrasound elastography using a standoff pad reference provides a valid method for evaluating the elastic modulus of the perineal body in living women. PMID:25801422

Elastic medium equivalent to Fresnel's double-refraction crystal.

PubMed

Carcione, José M; Helbig, Klaus

2008-10-01

In 1821, Fresnel obtained the wave surface of an optically biaxial crystal, assuming that light waves are vibrations of the ether in which longitudinal vibrations (P waves) do not propagate. An anisotropic elastic medium mathematically analogous to Fresnel's crystal exists. The medium has four elastic constants: a P-wave modulus, associated with a spherical P wave surface, and three elastic constants, c(44), c(55), and c(66), associated with the shear waves, which are mathematically equivalent to the three dielectric permittivity constants epsilon(11), epsilon(22), and epsilon(33) as follows: mu(0)epsilon(11)<==>rho/c(44), mu(0)epsilon(22)<==>rho/c(55), mu(0)epsilon(33)<==>rho/c(66), where mu(0) is the magnetic permeability of vacuum and rho is the mass density. These relations also represent the equivalence between the elastic and electromagnetic wave velocities along the principal axes of the medium. A complete mathematical equivalence can be obtained by setting the P-wave modulus equal to zero, but this yields an unstable elastic medium (the hypothetical ether). To obtain stability the P-wave velocity has to be assumed infinite (incompressibility). Another equivalent Fresnel's wave surface corresponds to a medium with anomalous polarization. This medium is physically unstable even for a nonzero P-wave modulus.

Experimental Observation of Two Features Unexpected from the Classical Theories of Rubber Elasticity

NASA Astrophysics Data System (ADS)

Nishi, Kengo; Fujii, Kenta; Chung, Ung-il; Shibayama, Mitsuhiro; Sakai, Takamasa

2017-12-01

Although the elastic modulus of a Gaussian chain network is thought to be successfully described by classical theories of rubber elasticity, such as the affine and phantom models, verification experiments are largely lacking owing to difficulties in precisely controlling of the network structure. We prepared well-defined model polymer networks experimentally, and measured the elastic modulus G for a broad range of polymer concentrations and connectivity probabilities, p . In our experiment, we observed two features that were distinct from those predicted by classical theories. First, we observed the critical behavior G ˜|p -pc|1.95 near the sol-gel transition. This scaling law is different from the prediction of classical theories, but can be explained by analogy between the electric conductivity of resistor networks and the elasticity of polymer networks. Here, pc is the sol-gel transition point. Furthermore, we found that the experimental G -p relations in the region above C* did not follow the affine or phantom theories. Instead, all the G /G0-p curves fell onto a single master curve when G was normalized by the elastic modulus at p =1 , G0. We show that the effective medium approximation for Gaussian chain networks explains this master curve.

Mechanical properties of injection-molded thermoplastic denture base resins.

PubMed

Hamanaka, Ippei; Takahashi, Yutaka; Shimizu, Hiroshi

2011-03-01

To investigate the mechanical properties of injection-molded thermoplastic denture base resins. Four injection-molded thermoplastic resins (two polyamides, one polyethylene terephthalate, one polycarbonate) and, as a control, a conventional heat-polymerized polymethyl methacrylate (PMMA), were used in this study. The flexural strength at the proportional limit (FS-PL), the elastic modulus, and the Charpy impact strength of the denture base resins were measured according to International Organization for Standardization (ISO) 1567 and ISO 1567:1999/Amd 1:2003. The descending order of the FS-PL was: conventional PMMA > polyethylene terephthalate, polycarbonate > two polyamides. The descending order of the elastic moduli was: conventional PMMA > polycarbonate > polyethylene terephthalate > two polyamides. The descending order of the Charpy impact strength was: polyamide (Nylon PACM12) > polycarbonate > polyamide (Nylon 12), polyethylene terephthalate > conventional PMMA. All of the injection-molded thermoplastic resins had significantly lower FS-PL, lower elastic moduli, and higher or similar impact strength compared to the conventional PMMA. The polyamide denture base resins had low FS-PL and low elastic moduli; one of them possessed very high impact strength, and the other had low impact strength. The polyethylene terephthalate denture base resin showed a moderately high FS-PL, moderate elastic modulus, and low impact strength. The polycarbonate denture base resin had a moderately high FS-PL, moderately high elastic modulus, and moderate impact strength.

AnisoVis: a MATLAB™ toolbox for the visualisation of elastic anisotropy

NASA Astrophysics Data System (ADS)

Healy, D.; Timms, N.; Pearce, M. A.

2016-12-01

The elastic properties of rocks and minerals vary with direction, and this has significant consequences for their physical response to acoustic waves and natural or imposed stresses. This anisotropy of elasticity is well described mathematically by 4th rank tensors of stiffness or compliance. These tensors are not easy to visualise in a single diagram or graphic, and visualising Poisson's ratio and shear modulus presents a further challenge in that their anisotropy depends on two principal directions. Students and researchers can easily underestimate the importance of elastic anisotropy. This presentation describes an open source toolbox of MATLAB scripts that aims to visualise elastic anisotropy in rocks and minerals. The code produces linked 2-D and 3-D representations of the standard elastic constants, such as Young's modulus, Poisson's ratio and shear modulus, all from a simple GUI. The 3-D plots can be manipulated by the user (rotated, panned, zoomed), to encourage investigation and a deeper understanding of directional variations in the fundamental properties. Examples are presented of common rock forming minerals, including those with negative Poisson's ratio (auxetic behaviour). We hope that an open source code base will encourage further enhancements from the rock physics and wider geoscience communities. Eventually, we hope to generate 3-D prints of these complex and beautiful natural surfaces to provide a tactile link to the underlying physics of elastic anisotropy.

Elastic and thermal properties of the layered thermoelectrics BiOCuSe and LaOCuSe

NASA Astrophysics Data System (ADS)

Saha, S. K.; Dutta, G.

2016-09-01

We determine the elastic properties of the layered thermoelectrics BiOCuSe and LaOCuSe using first-principles density functional theory calculations. To predict their stability, we calculate six distinct elastic constants, where all of them are positive, and suggest mechanically stable tetragonal crystals. As elastic properties relate to the nature and the strength of the chemical bond, the latter is analyzed by means of real-space descriptors, such as the electron localization function (ELF) and Bader charge. From elastic constants, a set of related properties, namely, bulk modulus, shear modulus, Young's modulus, sound velocity, Debye temperature, Grüneisen parameter, and thermal conductivity, are evaluated. Both materials are found to be ductile in nature and not brittle. We find BiOCuSe to have a smaller sound velocity and, hence, within the accuracy of the used Slack's model, a smaller thermal conductivity than LaOCuSe. Our calculations also reveal that the elastic properties and the related lattice thermal transport of both materials exhibit a much larger anisotropy than their electronic band properties that are known to be moderately anisotropic because of a moderate effective-electron-mass anisotropy. Finally, we determine the lattice dynamical properties, such as phonon dispersion, atomic displacement, and mode Grüneisen parameters, in order to correlate the elastic response, chemical bonding, and lattice dynamics.

Ultrahigh Elastic Strain Energy Storage in Metal-Oxide-Infiltrated Patterned Hybrid Polymer Nanocomposites

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

Dusoe, Keith J.; Ye, Xinyi; Kisslinger, Kim

Modulus of resilience, the measure of a material’s capacity to store and release elastic strain energy, is critical for realizing advanced mechanical actuation technologies in micro/nanoelectromechanical systems. In general, engineering the modulus of resilience is difficult because it requires asymmetrically increasing yield strength and Young’s modulus against their mutual scaling behavior. This task becomes further challenging if it needs to be carried out at the nanometer scale. Here, we demonstrate organic–inorganic hybrid composite nanopillars with one of the highest modulus of resilience per density by utilizing vapor-phase aluminum oxide infiltration in lithographically patterned negative photoresist SU-8. In situ nanomechanical measurementsmore » reveal a metal-like high yield strength (~500 MPa) with an unusually low, foam-like Young’s modulus (~7 GPa), a unique pairing that yields ultrahigh modulus of resilience, reaching up to ~24 MJ/m 3 as well as exceptional modulus of resilience per density of ~13.4 kJ/kg, surpassing those of most engineering materials. The hybrid polymer nanocomposite features lightweight, ultrahigh tunable modulus of resilience and versatile nanoscale lithographic patternability with potential for application as nanomechanical components which require ultrahigh mechanical resilience and strength.« less

Ultrahigh Elastic Strain Energy Storage in Metal-Oxide-Infiltrated Patterned Hybrid Polymer Nanocomposites

DOE PAGES

Dusoe, Keith J.; Ye, Xinyi; Kisslinger, Kim; ...

2017-10-19

Modulus of resilience, the measure of a material’s capacity to store and release elastic strain energy, is critical for realizing advanced mechanical actuation technologies in micro/nanoelectromechanical systems. In general, engineering the modulus of resilience is difficult because it requires asymmetrically increasing yield strength and Young’s modulus against their mutual scaling behavior. This task becomes further challenging if it needs to be carried out at the nanometer scale. Here, we demonstrate organic–inorganic hybrid composite nanopillars with one of the highest modulus of resilience per density by utilizing vapor-phase aluminum oxide infiltration in lithographically patterned negative photoresist SU-8. In situ nanomechanical measurementsmore » reveal a metal-like high yield strength (~500 MPa) with an unusually low, foam-like Young’s modulus (~7 GPa), a unique pairing that yields ultrahigh modulus of resilience, reaching up to ~24 MJ/m 3 as well as exceptional modulus of resilience per density of ~13.4 kJ/kg, surpassing those of most engineering materials. The hybrid polymer nanocomposite features lightweight, ultrahigh tunable modulus of resilience and versatile nanoscale lithographic patternability with potential for application as nanomechanical components which require ultrahigh mechanical resilience and strength.« less

Effects of temperature distribution and elastic properties of materials on gas-turbine-disk stresses

NASA Technical Reports Server (NTRS)

Holms, Arthur G; Faldetta, Richard D

1947-01-01

Calculations were made to determine the influence of changes in temperature distribution and in elastic material properties on calculated elastic stresses for a typical gas-turbine disk. Severe temperature gradients caused thermal stresses of sufficient magnitude to reduce the operating safety of the disk. Small temperature gradients were found to be desirable because they produced thermal stresses that subtracted from the centrifugal stresses in the region of the rim. The thermal gradients produced a tendency for a severe stress condition to exist near the rim but this stress condition could be shifted away from the region of blade attachment by altering the temperature distribution. The investigation of elastic material properties showed that centrifugal stresses are slightly affected by changes in modulus of elasticity, but that thermal stresses are approximately proportional to modulus of elasticity and to coefficient of thermal expansion.

Effect of carbon fiber addition on the electromagnetic shielding properties of carbon fiber/polyacrylamide/wood based fiberboards

NASA Astrophysics Data System (ADS)

Dang, Baokang; Chen, Yipeng; Yang, Ning; Chen, Bo; Sun, Qingfeng

2018-05-01

Carbon fiber (CF) reinforced polyacrylamide/wood fiber composite boards are fabricated by mechanical grind-assisted hot-pressing, and are used for electromagnetic interference (EMI) shielding. CF with an average diameter of 150 nm is distributed on wood fiber, which is then encased by polyacrylamide. The CF/polyacrylamide/wood fiber (CPW) composite exhibits an optimal EMI shielding effectiveness (SE) of 41.03 dB compared to that of polyacrylamide/wood fiber composite (0.41 dB), which meets the requirements of commercial merchandise. Meanwhile, the CPW composite also shows high mechanical strength. The maximum modulus of rupture (MOR) and modulus of elasticity (MOE) of CPW composites are 39.52 MPa and 5823.15 MPa, respectively. The MOR and MOE of CPW composites increased by 38% and 96%, respectively, compared to that of polyacrylamide/wood fiber composite (28.64 and 2967.35 MPa).

Effect of carbon fiber addition on the electromagnetic shielding properties of carbon fiber/polyacrylamide/wood based fiberboards.

PubMed

Dang, Baokang; Chen, Yipeng; Yang, Ning; Chen, Bo; Sun, Qingfeng

2018-05-11

Carbon fiber (CF) reinforced polyacrylamide/wood fiber composite boards are fabricated by mechanical grind-assisted hot-pressing, and are used for electromagnetic interference (EMI) shielding. CF with an average diameter of 150 nm is distributed on wood fiber, which is then encased by polyacrylamide. The CF/polyacrylamide/wood fiber (CPW) composite exhibits an optimal EMI shielding effectiveness (SE) of 41.03 dB compared to that of polyacrylamide/wood fiber composite (0.41 dB), which meets the requirements of commercial merchandise. Meanwhile, the CPW composite also shows high mechanical strength. The maximum modulus of rupture (MOR) and modulus of elasticity (MOE) of CPW composites are 39.52 MPa and 5823.15 MPa, respectively. The MOR and MOE of CPW composites increased by 38% and 96%, respectively, compared to that of polyacrylamide/wood fiber composite (28.64 and 2967.35 MPa).

Effect of emulsifier type and concentration, aqueous phase volume and wax ratio on physical, material and mechanical properties of water in oil lipsticks.

PubMed

Beri, A; Norton, J E; Norton, I T

2013-12-01

Water-in-oil emulsions in lipsticks could have the potential to improve moisturizing properties and deliver hydrophilic molecules to the lips. The aims of this work were (i) to investigate the effect of emulsifier type (polymer vs. monomer, and saturated vs. unsaturated chain) and concentration on droplet size and (ii) to investigate the effect of wax ratio (carnauba wax, microcrystalline wax, paraffin wax and performalene) and aqueous phase volume on material properties (Young's modulus, point of fracture, elastic modulus and viscous modulus). Emulsion formation was achieved using a high shear mixer. Results showed that the saturated nature of the emulsifier had very little effect on droplet size, neither did the use of an emulsifier with a larger head group (droplet size ~18-25 μm). Polyglycerol polyricinoleate (PGPR) resulted in emulsions with the smallest droplets (~3-5 μm), as expected from previous studies that show that it produces a thick elastic interface. The results also showed that both Young's modulus and point of fracture increase with increasing percentage of carnauba wax (following a power law dependency of 3), but decrease with increasing percentage of microcrystalline wax, suggesting that the carnauba wax is included in the overall wax network formed by the saturated components, whereas the microcrystalline wax forms irregular crystals that disrupt the overall wax crystal network. Young's modulus, elastic modulus and viscous modulus all decrease with increasing aqueous phase volume in the emulsions, although the slope of the decrease in elastic and viscous moduli is dependent on the addition of solid wax, as a result of strengthening the network. This work suggests the potential use for emulsions in lipstick applications, particularly when PGPR is used as an emulsifier, and with the addition of solid wax, as it increases network strength. © 2013 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Frequency Analysis of Strain of Cylindrical Shell for Assessment of Viscosity

NASA Astrophysics Data System (ADS)

Hasegawa, Hideyuki; Kanai, Hiroshi

2005-06-01

For tissue characterization of atherosclerotic plaque, we have developed a method, namely, the phased tracking method, [H. Kanai et al.: IEEE Trans. Ultrason. Ferroelectr. Freq. Control 43 (1996) 791] to measure the regional strain (change in wall thickness) and elasticity of the arterial wall. In addition to the regional elasticity, we are attempting to measure the regional viscosity for a more precise tissue characterization. Previously, we showed that the viscosity can be obtained by measuring the frequency dependence of the elastic modulus using remote actuation [H. Hasegawa et al.: Jpn. J. Appl. Phys. 43 (2004) 3197]. However, in this method, we need to apply external actuation to the subject. To simplify the measurement, we instead to obtain the frequency dependence of the elastic modulus from the change in arterial wall thickness spontaneously caused by the heartbeat because this change in thickness consists of frequency components up to 20-30 Hz. In this paper, the frequency dependence of the elastic modulus of a silicone rubber tube was investigated by applying frequency analysis to the change in wall thickness caused by the change in internal pressure simulating the actual arterial blood pressure.

Infrared spectroscopy, nano-mechanical properties, and scratch resistance of esthetic orthodontic coated archwires.

PubMed

da Silva, Dayanne Lopes; Santos, Emanuel; Camargo, Sérgio de Souza; Ruellas, Antônio Carlos de Oliveira

2015-09-01

To evaluate the material composition, mechanical properties (hardness and elastic modulus), and scratch resistance of the coating of four commercialized esthetic orthodontic archwires. The coating composition of esthetic archwires was assessed by Fourier-transform infrared spectroscopy (FTIR). Coating hardness and elastic modulus were analyzed with instrumented nano-indentation tests. Scratch resistance of coatings was evaluated by scratch test. Coating micromorphologic characteristics after scratch tests were observed in a scanning electron microscope. Statistical differences were investigated using analysis of variance and Tukey post hoc test. The FTIR results indicate that all analyzed coatings were markedly characterized by the benzene peak at about 1500 cm(-1). The coating hardness and elastic modulus average values ranged from 0.17 to 0.23 GPa and from 5.0 to 7.6 GPa, respectively. Scratch test showed a high coating elasticity after load removal with elastic recoveries >60%, but different failure features could be observed along the scratches. The coatings of esthetic archwires evaluated are probably a composite of polyester and polytetrafluoroethylene. Delamination, crack propagation, and debris generation could be observed along the coating scratches and could influence its durability in the oral environment.

Modelling of single walled carbon nanotube cylindrical structures with finite element method simulations

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

Günay, E.

In this study, the modulus of elasticity and shear modulus values of single-walled carbon nanotubes SWCNTs were modelled by using both finite element method and the Matlab code. Initially, cylindrical armchair and zigzag single walled 3D space frames were demonstrated as carbon nanostructures. Thereafter, macro programs were written by the Matlab code producing the space truss for zigzag and armchair models. 3D space frames were introduced to the ANSYS software and then tension, compression and additionally torsion tests were performed on zigzag and armchair carbon nanotubes with BEAM4 element in obtaining the exact values of elastic and shear modulus values.more » In this study, two different boundary conditions were tested and especially used in torsion loading. The equivalent shear modulus data was found by averaging the corresponding values obtained from ten different nodal points on the nanotube path. Finally, in this study it was determined that the elastic constant values showed proportional changes by increasing the carbon nanotube diameters up to a certain level but beyond this level these values remained stable.« less

A first principle calculation of anisotropic elastic, mechanical and electronic properties of TiB

NASA Astrophysics Data System (ADS)

Zhang, Junqin; Zhao, Bin; Ma, Huihui; Wei, Qun; Yang, Yintang

2018-04-01

The structural, mechanical and electronic properties of the NaCl-type structure TiB are theoretically calculated based on the first principles. The density of states of TiB shows obvious density peaks at -0.70eV. Furthermore, there exists a pseudogap at 0.71eV to the right of the Fermi level. The calculated structural and mechanical parameters (i.e., bulk modulus, shear modulus, Young's modulus, Poisson's ratio and universal elastic anisotropy index) were in good agreement both with the previously reported experimental values and theoretical results at zero pressure. The mechanical stability criterion proves that TiB at zero pressure is mechanistically stable and exhibits ductility. The universal anisotropic index and the 3D graphics of Young's modulus are also given in this paper, which indicates that TiB is anisotropy under zero pressure. Moreover, the effects of applied pressures on the structural, mechanical and anisotropic elastic of TiB were studied in the range from 0 to 100GPa. It was found that ductility and anisotropy of TiB were enhanced with the increase of pressure.

Contact mechanics for coated spheres that includes the transition from weak to strong adhesion

DOE PAGES

Reedy, Earl David

2007-09-01

Recently published results for a rigid spherical indenter contacting a thin, linear elastic coating on a rigid planar substrate have been extended to include the case of two contacting spheres, where each sphere is rigid and coated with a thin, linear elastic material. This is done by using an appropriately chosen effective radius and coating modulus. Finally, the earlier work has also been extended to provide analytical results that span the transition between the previously derived Derjaguin–Müller–Toporov (DMT)-like (work of adhesion/coating-modulus ratio is small) and Johnson–Kendall–Roberts (JKR)-like (work of adhesion/coating-modulus ratio is large) limits.

Elastic model of the traction behavior of two traction lubricants

NASA Technical Reports Server (NTRS)

Loewenthal, S. H.; Rohn, D. A.

1984-01-01

In the analysis of rolling-sliding concentrated contacts, such as gears, bearings and traction drives, the traction characteristics of the lubricant are of prime importance. The elastic shear modulus and limiting shear stress properties of the lubricant dictate the traction/slip characteristics and power loss associated with an EHD contact undergoing slip and/or spin. These properties can be deducted directly from the initial slope m and maximum traction coefficient micron of an experimental traction curve. In this investigation, correlation equations are presented to predict m and micron for two modern traction fluids based on the regression analysis of 334 separate traction disk machine experiments. The effects of contact pressure, temperature, surface velocity, ellipticity ratio are examined. Problems in deducing lubricant shear moduli from disk machine tests are discussed. Previously announced in STAR as N83-20116

Broad Anatomical Variation within a Narrow Wood Density Range--A Study of Twig Wood across 69 Australian Angiosperms.

PubMed

Ziemińska, Kasia; Westoby, Mark; Wright, Ian J

2015-01-01

Just as people with the same weight can have different body builds, woods with the same wood density can have different anatomies. Here, our aim was to assess the magnitude of anatomical variation within a restricted range of wood density and explore its potential ecological implications. Twig wood of 69 angiosperm tree and shrub species was analyzed. Species were selected so that wood density varied within a relatively narrow range (0.38-0.62 g cm-3). Anatomical traits quantified included wood tissue fractions (fibres, axial parenchyma, ray parenchyma, vessels, and conduits with maximum lumen diameter below 15 μm), vessel properties, and pith area. To search for potential ecological correlates of anatomical variation the species were sampled across rainfall and temperature contrasts, and several other ecologically-relevant traits were measured (plant height, leaf area to sapwood area ratio, and modulus of elasticity). Despite the limited range in wood density, substantial anatomical variation was observed. Total parenchyma fraction varied from 0.12 to 0.66 and fibre fraction from 0.20 to 0.74, and these two traits were strongly inversely correlated (r = -0.86, P < 0.001). Parenchyma was weakly (0.24 ≤|r|≤ 0.35, P < 0.05) or not associated with vessel properties nor with height, leaf area to sapwood area ratio, and modulus of elasticity (0.24 ≤|r|≤ 0.41, P < 0.05). However, vessel traits were fairly well correlated with height and leaf area to sapwood area ratio (0.47 ≤|r|≤ 0.65, all P < 0.001). Modulus of elasticity was mainly driven by fibre wall plus vessel wall fraction rather than by the parenchyma component. Overall, there seem to be at least three axes of variation in xylem, substantially independent of each other: a wood density spectrum, a fibre-parenchyma spectrum, and a vessel area spectrum. The fibre-parenchyma spectrum does not yet have any clear or convincing ecological interpretation.

Effect of elasticity on stress distribution in CAD/CAM dental crowns: Glass ceramic vs. polymer-matrix composite.

PubMed

Duan, Yuanyuan; Griggs, Jason A

2015-06-01

Further investigations are required to evaluate the mechanical behaviour of newly developed polymer-matrix composite (PMC) blocks for computer-aided design/computer-aided manufacturing (CAD/CAM) applications. The purpose of this study was to investigate the effect of elasticity on the stress distribution in dental crowns made of glass-ceramic and PMC materials using finite element (FE) analysis. Elastic constants of two materials were determined by ultrasonic pulse velocity using an acoustic thickness gauge. Three-dimensional solid models of a full-coverage dental crown on a first mandibular molar were generated based on X-ray micro-CT scanning images. A variety of load case-material property combinations were simulated and conducted using FE analysis. The first principal stress distribution in the crown and luting agent was plotted and analyzed. The glass-ceramic crown had stress concentrations on the occlusal surface surrounding the area of loading and the cemented surface underneath the area of loading, while the PMC crown had only stress concentration on the occlusal surface. The PMC crown had lower maximum stress than the glass-ceramic crown in all load cases, but this difference was not substantial when the loading had a lateral component. Eccentric loading did not substantially increase the maximum stress in the prosthesis. Both materials are resistant to fracture with physiological occlusal load. The PMC crown had lower maximum stress than the glass-ceramic crown, but the effect of a lateral loading component was more pronounced for a PMC crown than for a glass-ceramic crown. Knowledge of the stress distribution in dental crowns with low modulus of elasticity will aid clinicians in planning treatments that include such restorations. Copyright © 2015 Elsevier Ltd. All rights reserved.

Noninvasive Vascular Displacement Estimation for Relative Elastic Modulus Reconstruction in Transversal Imaging Planes

PubMed Central

Hansen, Hendrik H.G.; Richards, Michael S.; Doyley, Marvin M.; de Korte, Chris L.

2013-01-01

Atherosclerotic plaque rupture can initiate stroke or myocardial infarction. Lipid-rich plaques with thin fibrous caps have a higher risk to rupture than fibrotic plaques. Elastic moduli differ for lipid-rich and fibrous tissue and can be reconstructed using tissue displacements estimated from intravascular ultrasound radiofrequency (RF) data acquisitions. This study investigated if modulus reconstruction is possible for noninvasive RF acquisitions of vessels in transverse imaging planes using an iterative 2D cross-correlation based displacement estimation algorithm. Furthermore, since it is known that displacements can be improved by compounding of displacements estimated at various beam steering angles, we compared the performance of the modulus reconstruction with and without compounding. For the comparison, simulated and experimental RF data were generated of various vessel-mimicking phantoms. Reconstruction errors were less than 10%, which seems adequate for distinguishing lipid-rich from fibrous tissue. Compounding outperformed single-angle reconstruction: the interquartile range of the reconstructed moduli for the various homogeneous phantom layers was approximately two times smaller. Additionally, the estimated lateral displacements were a factor of 2–3 better matched to the displacements corresponding to the reconstructed modulus distribution. Thus, noninvasive elastic modulus reconstruction is possible for transverse vessel cross sections using this cross-correlation method and is more accurate with compounding. PMID:23478602

Assessing the impact of wood decay fungi on the modulus of elasticity of slash pine (Pinus elliottii) by stress wave non-destructive testing

Treesearch

Zhong Yang; Zhehui Jiang; Chung Y. Hse; Ru Liu

2017-01-01

Small wood specimens selected from six slash pine (Pinus elliottii) trees were inoculated with brown-rot and white-rot fungi and then evaluated for static modulus of elasticity (MOE) and dynamic MOE (MOEsw). The experimental variables studied included a brown-rot fungus (Gloeophyllum trabeum) and a white-rot fungus (Trametes versicolor) for six exposure periods (2, 4,...

Stress Wave Interactions with Tunnels Buried in Well-Characterized Jointed Media.

DTIC Science & Technology

1980-06-01

27 14 Particle Velocity and Principal Stress Fields at 62 jisec for the Elastic- Plastic Media Model (Case 1, 0.8 kbar...is used; the basic formulation is similar to the HEMP code (Ref. 3) . Tn numerical solutions and material properties are luscriben in Section 3. 3...media is 16A rock simulant. The elastic- plastic properties are modeled with the following parameters: Bulk Modulus K = .131 Mbar Shear Modulus G

Dynamic determination of modulus of elasticity of full-size wood composite panels using a vibration method

Treesearch

Cheng Guan; Houjiang Zhang; Lujing Zhou; Xiping Wang

2015-01-01

A vibration testing method based on free vibration theory in a ‘‘free–free” support condition was investigated for evaluating the modulus of elasticity (MOE) of full-size wood composite panels (WCPs). Vibration experiments were conducted on three types of WCPs (medium density fibreboard, particleboard, and plywood) to determine the dynamic MOE of the panels. Static...

Determination of mechanical properties of polymer film materials

NASA Technical Reports Server (NTRS)

Hughes, E. J.; Rutherford, J. L.

1975-01-01

Five polymeric film materials, Tedlar, Teflon, Kapton H, Kapton F, and a fiberglass reinforced polyimide, PG-402, in thickness ranging from 0.002 to 0.005 inch, were tested over a temperature range of -195 to 200 C in the "machine" and transverse direction to determine: elastic modulus, Poisson's ratio, three percent offset yield stress, fracture stress, and strain to fracture. The elastic modulus, yield stress and fracture stress decreased with increasing temperature for all the materials while the fracture strain increased. Teflon and Tedlar had the greatest temperature dependence and PG-402 the least. At 200 C the Poisson ratio values ranged from 0.39 to 0.5; they diminished as the temperature decreased covering a range of 0.26 to 0.42 at -195 C. Shortening the gauge length from eight inches to one inch increased the strain to fracture and lowered the elastic modulus values.

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

Berdova, Maria; Liu, Xuwen; Franssila, Sami, E-mail: sami.franssila@aalto.fi

The investigation of mechanical properties of atomic layer deposition HfO{sub 2} films is important for implementing these layers in microdevices. The mechanical properties of films change as a function of composition and structure, which accordingly vary with deposition temperature and post-annealing. This work describes elastic modulus, hardness, and wear resistance of as-grown and annealed HfO{sub 2}. From nanoindentation measurements, the elastic modulus and hardness remained relatively stable in the range of 163–165 GPa and 8.3–9.7 GPa as a function of deposition temperature. The annealing of HfO{sub 2} caused significant increase in hardness up to 14.4 GPa due to film crystallization and densification. Themore » structural change also caused increase in the elastic modulus up to 197 GPa. Wear resistance did not change as a function of deposition temperature, but improved upon annealing.« less

Elastic Properties of Pore-Spanning Apical Cell Membranes Derived from MDCK II Cells.

PubMed

Nehls, Stefan; Janshoff, Andreas

2017-10-17

The mechanical response of adherent, polarized cells to indentation is frequently attributed to the presence of an endogenous actin cortex attached to the inner leaflet of the plasma membrane. Here, we scrutinized the elastic properties of apical membranes separated from living cells and attached to a porous mesh in the absence of intracellular factors originating from the cytosol, organelles, the substrate, neighbors, and the nucleus. We found that a tension-based model describes the data very well providing essentially the prestress of the shell generated by adhesion of the apical membrane patches to the pore rim and the apparent area compressibility modulus, an intrinsic elastic modulus modulated by the surface excess stored in membrane reservoirs. Removal of membrane-associated proteins by proteases decreases the area compressibility modulus, whereas fixation and cross-linking of proteins with glutaraldehyde increases it. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Anisotropy of demineralized bone matrix under compressive load.

PubMed

Trębacz, Hanna; Zdunek, Artur

2011-01-01

Two groups of cubic specimens from diaphysis of bovine femur, intact and completely demineralized, were axially compressed. One half of the samples from each group were loaded along the axis of the femur (L) and the other - perpendicularly (T). Intact samples were characterized in terms of elastic modulus; for demineralized samples secant modulus of elasticity was calculated. During compression an acoustic emission (AE) signal was recorded and AE events and energy were analyzed. Samples of intact bone did not reveal any anisotropy under compression at the stress of 80 MPa. However, AE signal indicated an initiation of failure in samples loaded in T direction. Demineralized samples were anisotropic under compression. Both secant modulus of elasticity and AE parameters were significantly higher in T direction than in L direction, which is attributed to shifting and separation of lamellae of collagen fibrils and lamellae in bone matrix.

Elastic moduli of a Brownian colloidal glass former

NASA Astrophysics Data System (ADS)

Fritschi, S.; Fuchs, M.

2018-01-01

The static, dynamic and flow-dependent shear moduli of a binary mixture of Brownian hard disks are studied by an event-driven molecular dynamics simulation. Thereby, the emergence of rigidity close to the glass transition encoded in the static shear modulus G_∞ is accessed by three methods. Results from shear stress auto-correlation functions, elastic dispersion relations, and the elastic response to strain deformations upon the start-up of shear flow are compared. This enables one to sample the time-dependent shear modulus G(t) consistently over several decades in time. By that a very precise specification of the glass transition point and of G_∞ is feasible. Predictions by mode coupling theory of a finite shear modulus at the glass transition, of α-scaling in fluid states close to the transition, and of shear induced decay in yielding glass states are tested and broadly verified.

Multi-modality gellan gum-based tissue-mimicking phantom with targeted mechanical, electrical, and thermal properties.

PubMed

Chen, Roland K; Shih, A J

2013-08-21

This study develops a new class of gellan gum-based tissue-mimicking phantom material and a model to predict and control the elastic modulus, thermal conductivity, and electrical conductivity by adjusting the mass fractions of gellan gum, propylene glycol, and sodium chloride, respectively. One of the advantages of gellan gum is its gelling efficiency allowing highly regulable mechanical properties (elastic modulus, toughness, etc). An experiment was performed on 16 gellan gum-based tissue-mimicking phantoms and a regression model was fit to quantitatively predict three material properties (elastic modulus, thermal conductivity, and electrical conductivity) based on the phantom material's composition. Based on these material properties and the regression model developed, tissue-mimicking phantoms of porcine spinal cord and liver were formulated. These gellan gum tissue-mimicking phantoms have the mechanical, thermal, and electrical properties approximately equivalent to those of the spinal cord and the liver.

Mechanical Sensing with Flexible Metallic Nanowires

NASA Astrophysics Data System (ADS)

Dobrokhotov, Vladimir; Yazdanpanah, Mehdi; Pabba, Santosh; Safir, Abdelilah; Cohn, Robert

2008-03-01

A calibrated method of force sensing is demonstrated in which the buckled shape of a long flexible metallic nanowire is interpreted to determine the applied force. Using a nanomanipulator the nanowire is buckled in the chamber of a scanning electron microscope (SEM) and the buckled shapes are recorded in SEM images. Force is determined as a function of deflection for an assumed elastic modulus by fitting the shapes using the generalized elastica model. In this calibration the elastic modulus was determined using an auxiliary AFM measurement, with the needle in the same orientation as in the SEM. Following this calibration the needle was used as a sensor in a different orientation than the AFM coordinates to deflect a suspended PLLA polymer fiber from which the elastic modulus (2.96 GPa) was determined. In this study the same needle remained rigidly secured to the AFM cantilever throughout the entire SEM/AFM calibration procedure and the characterization of the nanofiber.

Effect of Curing Period on Properties of Steel and Polypropylene Fibre Reinforced Ultra-High Performance Concrete

NASA Astrophysics Data System (ADS)

Smarzewski, Piotr

2017-10-01

This study has investigated the effect of curing period on the mechanical properties of straight polypropylene and hooked-end steel fibre reinforced ultra-high performance concrete (UHPC). Various physical properties are evaluated, i.e. absorbability, apparent density and open porosity. Compressive strength, tensile splitting strength, flexural strength and modulus of elasticity were determined at 28, 56 and 730 days. Comparative strength development of fibre reinforced mixes at 0.5%, 1%, 1.5% and 2% by volume fractions in relation to the mix without fibres was observed. Good correlations between the compressive strength and the modulus of elasticity are established. Steel and polypropylene fibres significantly increased the compressive strength, tensile splitting strength, flexural strength and modulus of elasticity of UHPC after two years curing period when fibre content volume was at least 1%. It seems that steel fibre reinforced UHPC has better properties than the polypropylene fibre reinforced UHPC.

Effects of process variables on the encapsulation of oil in ca-alginate capsules using an inverse gelation technique.

PubMed

Abang, Sariah; Chan, Eng-Seng; Poncelet, Denis

2012-01-01

The objective of this study was to investigate the effects of process variables on the encapsulation of oil in a calcium alginate membrane using an inverse gelation technique. A dispersion of calcium chloride solution in sunflower oil (water-in-oil emulsion) was added dropwise to the alginate solution. The migration of calcium ions to the alginate solution initiates the formation of a ca-alginate membrane around the emulsion droplets. The membrane thickness of wet capsules and the elastic modulus of dry capsules increased following first-order kinetics with an increasing curing time. An increase in the calcium chloride concentration increased the membrane thickness of wet capsules and the elastic modulus of dry capsules. An increase in the alginate concentration decreased the mean diameter of wet capsules but increased the elastic modulus of dry capsules.

Solvent-free, supersoft and superelastic bottlebrush melts and networks

NASA Astrophysics Data System (ADS)

Daniel, William F. M.; Burdyńska, Joanna; Vatankhah-Varnoosfaderani, Mohammad; Matyjaszewski, Krzysztof; Paturej, Jarosław; Rubinstein, Michael; Dobrynin, Andrey V.; Sheiko, Sergei S.

2016-02-01

Polymer gels are the only viable class of synthetic materials with a Young's modulus below 100 kPa conforming to biological applications, yet those gel properties require a solvent fraction. The presence of a solvent can lead to phase separation, evaporation and leakage on deformation, diminishing gel elasticity and eliciting inflammatory responses in any surrounding tissues. Here, we report solvent-free, supersoft and superelastic polymer melts and networks prepared from bottlebrush macromolecules. The brush-like architecture expands the diameter of the polymer chains, diluting their entanglements without markedly increasing stiffness. This adjustable interplay between chain diameter and stiffness makes it possible to tailor the network's elastic modulus and extensibility without the complications associated with a swollen gel. The bottlebrush melts and elastomers exhibit an unprecedented combination of low modulus (~100 Pa), high strain at break (~1,000%), and extraordinary elasticity, properties that are on par with those of designer gels.

Nonlinear effects in thermal stress analysis of a solid propellant rocket motor

NASA Technical Reports Server (NTRS)

Francis, E. C.; Peeters, R. L.; Murch, S. A.

1976-01-01

Direct characterization procedures were used to determine the relaxation modulus as a function of time, temperature, and state of strain. Using the quasi-elastic method of linearviscoelasticity, these properties were employed in a finite element computer code to analyze a thick-walled, nonlinear viscoelastic cylinder in the state of plane strain bonded to a thin (but stiff) elastic casing and subjected to slow thermal cooling. The viscoelastic solution is then expressed as a sequence of elastic finite element solutions. The strain-dependent character of the relaxation modulus is included by replacing the single relaxation curve used in the linear viscoelastic theory by a family of relaxation functions obtained at various strain levels. These functions may be regarded as a collection of stress histories or responses to specific loads (in this case, step strains) with which the cooldown solution is made to agree by iterations on the modulus and strain level.

Theoretical requirements for broadband perfect absorption of acoustic waves by ultra-thin elastic meta-films

PubMed Central

Duan, Yuetao; Luo, Jie; Wang, Guanghao; Hang, Zhi Hong; Hou, Bo; Li, Jensen; Sheng, Ping; Lai, Yun

2015-01-01

We derive and numerically demonstrate that perfect absorption of elastic waves can be achieved in two types of ultra-thin elastic meta-films: one requires a large value of almost pure imaginary effective mass density and a free space boundary, while the other requires a small value of almost pure imaginary effective modulus and a hard wall boundary. When the pure imaginary density or modulus exhibits certain frequency dispersions, the perfect absorption effect becomes broadband, even in the low frequency regime. Through a model analysis, we find that such almost pure imaginary effective mass density with required dispersion for perfect absorption can be achieved by elastic metamaterials with large damping. Our work provides a feasible approach to realize broadband perfect absorption of elastic waves in ultra-thin films. PMID:26184117

Propagating elastic vibrations dominate thermal conduction in amorphous silicon

NASA Astrophysics Data System (ADS)

Moon, Jaeyun; Latour, Benoit; Minnich, Austin J.

2018-01-01

The thermal atomic vibrations of amorphous solids can be distinguished by whether they propagate as elastic waves or do not propagate due to lack of atomic periodicity. In a -Si, prior works concluded that nonpropagating waves are the dominant contributors to heat transport, with propagating waves being restricted to frequencies less than a few THz and scattered by anharmonicity. Here, we present a lattice and molecular dynamics analysis of vibrations in a -Si that supports a qualitatively different picture in which propagating elastic waves dominate the thermal conduction and are scattered by local fluctuations of elastic modulus rather than anharmonicity. We explicitly demonstrate the propagating nature of waves up to around 10 THz, and further show that pseudoperiodic structures with homogeneous elastic properties exhibit a marked temperature dependence characteristic of anharmonic interactions. Our work suggests that most heat is carried by propagating elastic waves in a -Si and demonstrates that manipulating local elastic modulus variations is a promising route to realize amorphous materials with extreme thermal properties.

Investigation into local cell mechanics by atomic force microscopy mapping and optical tweezer vertical indentation

NASA Astrophysics Data System (ADS)

Coceano, G.; Yousafzai, M. S.; Ma, W.; Ndoye, F.; Venturelli, L.; Hussain, I.; Bonin, S.; Niemela, J.; Scoles, G.; Cojoc, D.; Ferrari, E.

2016-02-01

Investigating the mechanical properties of cells could reveal a potential source of label-free markers of cancer progression, based on measurable viscoelastic parameters. The Young’s modulus has proved to be the most thoroughly studied so far, however, even for the same cell type, the elastic modulus reported in different studies spans a wide range of values, mainly due to the application of different experimental conditions. This complicates the reliable use of elasticity for the mechanical phenotyping of cells. Here we combine two complementary techniques, atomic force microscopy (AFM) and optical tweezer microscopy (OTM), providing a comprehensive mechanical comparison of three human breast cell lines: normal myoepithelial (HBL-100), luminal breast cancer (MCF-7) and basal breast cancer (MDA-MB-231) cells. The elastic modulus was measured locally by AFM and OTM on single cells, using similar indentation approaches but different measurement parameters. Peak force tapping AFM was employed at nanonewton forces and high loading rates to draw a viscoelastic map of each cell and the results indicated that the region on top of the nucleus provided the most meaningful results. OTM was employed at those locations at piconewton forces and low loading rates, to measure the elastic modulus in a real elastic regime and rule out the contribution of viscous forces typical of AFM. When measured by either AFM or OTM, the cell lines’ elasticity trend was similar for the aggressive MDA-MB-231 cells, which were found to be significantly softer than the other two cell types in both measurements. However, when comparing HBL-100 and MCF-7 cells, we found significant differences only when using OTM.

Influence of elastic parameters on the evolution of elasticity modulus of thin films

NASA Astrophysics Data System (ADS)

Gacem, A.; Doghmane, A.; Hadjoub, Z.; Beldi, I.; Doghmane, M.

2012-09-01

In recent years, it appears many structures in the form of thin films or multilayers, used as coatings for surface protection, or to provide materials with new properties different from those of substrates. These properties are the subject of a growing number of studies in order to produce Nano or micro structures with different degrees of quality, and cost as well as the manufacture of thin film properties more functional and more controllable. As the thicknesses are close to micrometric or nanometric scales, the modulus of elasticity are difficult to measure and experimental results are rarely published in the literature. In this context, we propose an analytical qualitative methodology to describe the influence of acoustic parameters of thin films on the evolution of elastic moduli the most used. This method is based on the determination of the acoustic signature V(z) of several thin layers deposited on different substrates, as well the information on the propagation velocity of ultrasonic waves are obtained. Thus, the dispersion curves representing the variation of the modulus of elasticity (Young and the shear), were determined. We have noticed that, according to the type of substrate (light, medium or heavy), we observed the appearance of some anomalies in curves that are generally associated with changes in the acoustic properties of each of the examined layers. We have shown that these anomalies are mainly due to the effect loading, and represent one of the fundamental parameters determining the appearance or disappearance of a phenomenon and represent one of the basic parameters determining the appearance or disappearance of phenomena. Finally, we determine the Poisson ratio of thin films in order to calculate other elastic parameters such as the compressor modulus.

Effect of tooth bleaching agents on protein content and mechanical properties of dental enamel.

PubMed

Elfallah, Hunida M; Bertassoni, Luiz E; Charadram, Nattida; Rathsam, Catherine; Swain, Michael V

2015-07-01

This study investigated the effect of two bleaching agents, 16% carbamide peroxide (CP) and 35% hydrogen peroxide (HP), on the mechanical properties and protein content of human enamel from freshly extracted teeth. The protein components of control and treated enamel were extracted and examined on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Marked reduction of the protein matrix and random fragmentation of the enamel proteins after bleaching treatments was found. The mechanical properties were analyzed with Vickers indentations to characterize fracture toughness, and nanoindentation to establish enamel hardness, elastic modulus and creep deformation. Results indicate that the hardness and elastic modulus of enamel were significantly reduced after treatment with CP and HP. After bleaching, the creep deformation at maximum load increased and the recovery upon unloading reduced. Crack lengths of CP and HP treated enamel were increased, while fracture toughness decreased. Additionally, the microstructures of fractured and indented samples were examined with field emission gun scanning electron microscopy (FEG-SEM) showing distinct differences in the fracture surface morphology between pre- and post-bleached enamel. In conclusion, tooth bleaching agents can produce detrimental effects on the mechanical properties of enamel, possibly as a consequence of damaging or denaturing of its protein components. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Structural, electronic, mechanical, and thermoelectric properties of a novel half Heusler compound HfPtPb

NASA Astrophysics Data System (ADS)

Kaur, Kulwinder; Rai, D. P.; Thapa, R. K.; Srivastava, Sunita

2017-07-01

We explore the structural, electronic, mechanical, and thermoelectric properties of a new half Heusler compound HfPtPb, an all metallic heavy element, recently proposed to be stable [Gautier et al., Nat. Chem. 7, 308 (2015)]. In this work, we employ density functional theory and semi-classical Boltzmann transport equations with constant relaxation time approximation. The mechanical properties, such as shear modulus, Young's modulus, elastic constants, Poisson's ratio, and shear anisotropy factor, have been investigated. The elastic and phonon properties reveal that this compound is mechanically and dynamically stable. Pugh's ratio and Frantsevich's ratio demonstrate its ductile behavior, and the shear anisotropic factor reveals the anisotropic nature of HfPtPb. The band structure predicts this compound to be a semiconductor with a band gap of 0.86 eV. The thermoelectric transport parameters, such as Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and lattice thermal conductivity, have been calculated as a function of temperature. The highest value of Seebeck coefficient is obtained for n-type doping at an optimal carrier concentration of 1.0 × 1020 e/cm3. We predict the maximum value of figure of merit (0.25) at 1000 K. Our investigation suggests that this material is an n-type semiconductor.

Rubber elasticity for percolation network consisting of Gaussian chains.

PubMed

Nishi, Kengo; Noguchi, Hiroshi; Sakai, Takamasa; Shibayama, Mitsuhiro

2015-11-14

A theory describing the elastic modulus for percolation networks of Gaussian chains on general lattices such as square and cubic lattices is proposed and its validity is examined with simulation and mechanical experiments on well-defined polymer networks. The theory was developed by generalizing the effective medium approximation (EMA) for Hookian spring network to Gaussian chain networks. From EMA theory, we found that the ratio of the elastic modulus at p, G to that at p = 1, G0, must be equal to G/G0 = (p - 2/f)/(1 - 2/f) if the position of sites can be determined so as to meet the force balance, where p is the degree of cross-linking reaction. However, the EMA prediction cannot be applicable near its percolation threshold because EMA is a mean field theory. Thus, we combine real-space renormalization and EMA and propose a theory called real-space renormalized EMA, i.e., REMA. The elastic modulus predicted by REMA is in excellent agreement with the results of simulations and experiments of near-ideal diamond lattice gels.

Measurement of high temperature elastic moduli of an 18Cr-9Ni-2.95 Cu-0.58 Nb-0.1C (Wt %) austenitic stainless steel

NASA Astrophysics Data System (ADS)

Tripathy, Haraprasanna; Hajra, Raj Narayan; Sudha, C.; Raju, S.; Saibaba, Saroja

2018-04-01

The Young's modulus (E) and Shear modulus (G) of an indigenously developed 18Cr-9Ni-0.1C-2.95 Cu-0.58Nb (wt %) austenitic stainless steel has been evaluated in the temperature range 298 K to 1273 K (25 °C to 1000 °C), using Impulse excitation technique (IET). The Bulk modulus (K) and the poison's ratio have been estimated from the measured values of E and G. It is observed that the elastic constants (E, G and K) are found to decrease in a nonlinear fashion with increase in temperature. The Cu precipitation is found to influence the elastic moduli of the steel in the cooling cycle. The observed elastic moduli are fitted to 3rd order polynomial equations in order to describe the temperature dependence of E, G, K moduli in the temperature range 298-1273 K (25 °C to 1000 °C). The room temperature values of E,G and K moduli is found to be 207, 82 and 145 GPa respectively for the present steel.

Rubber elasticity for percolation network consisting of Gaussian chains

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

Nishi, Kengo, E-mail: kengo.nishi@phys.uni-goettingen.de, E-mail: sakai@tetrapod.t.u-tokyo.ac.jp, E-mail: sibayama@issp.u-tokyo.ac.jp; Noguchi, Hiroshi; Shibayama, Mitsuhiro, E-mail: kengo.nishi@phys.uni-goettingen.de, E-mail: sakai@tetrapod.t.u-tokyo.ac.jp, E-mail: sibayama@issp.u-tokyo.ac.jp

2015-11-14

A theory describing the elastic modulus for percolation networks of Gaussian chains on general lattices such as square and cubic lattices is proposed and its validity is examined with simulation and mechanical experiments on well-defined polymer networks. The theory was developed by generalizing the effective medium approximation (EMA) for Hookian spring network to Gaussian chain networks. From EMA theory, we found that the ratio of the elastic modulus at p, G to that at p = 1, G{sub 0}, must be equal to G/G{sub 0} = (p − 2/f)/(1 − 2/f) if the position of sites can be determined somore » as to meet the force balance, where p is the degree of cross-linking reaction. However, the EMA prediction cannot be applicable near its percolation threshold because EMA is a mean field theory. Thus, we combine real-space renormalization and EMA and propose a theory called real-space renormalized EMA, i.e., REMA. The elastic modulus predicted by REMA is in excellent agreement with the results of simulations and experiments of near-ideal diamond lattice gels.« less

Pressure effect on the structural, phonon, elastic and thermodynamic properties of L12 phase RH3TA: First-principles calculations

NASA Astrophysics Data System (ADS)

Wang, Leini; Jian, Zhang; Ning, Wei

2018-06-01

The phonon, elastic and thermodynamic properties of L12 phase Rh3Ta have been investigated by the density functional theory (DFT) approach combined with the quasi-harmonic approximation model. The results of the phonon band structure show that L12 phase Rh3Ta possesses dynamical stability in the pressure range from 0-80 GPa due to the absence of imaginary frequencies. The pressure dependences with the elastic constants Cij, shear modulus G, bulk modulus B, Young’s modulus Y, Poisson’s ratio and B/G ratio have been analyzed. The results of the elastic properties studies show that L12 phase Rh3Ta compound is mechanically stable and possesses a higher hardness, improved ductility and plasticity under higher pressures. The pressure and temperature relationship of the thermodynamic properties, such as the Debye temperature ΘD, heat capacity Cp, thermal expansion coefficient α and the Grüneisen parameter γ are predicted by the quasi-harmonic Debye model in a wide pressure (0-80 GPa) and temperature (0-750 K) ranges.

The effects of fractional CO2 laser, Nano-hydroxyapatite and MI paste on mechanical properties of bovine enamel after bleaching

PubMed Central

Moosavi, Horieh

2017-01-01

Background This study investigated the effect of post bleaching treatments to the change of enamel elastic modulus and microhardness after dental bleaching in- vitro. Material and Methods Fifty bovine incisor slab were randomly assigned into five groups (n=10). The samples were bleached for three times; 20 minutes each time, by 40% hydrogen peroxide. Next it was applied fractional CO2 laser for two minutes, Nano- hydroxy apatite (N-HA) and MI-paste for 7 days and 2 minutes per day. The sound enamel and bleached teeth without post treatment remained as control groups. The elastic modulus and microhardness were measured at three times; 24 hours, 1 and 2 months. Data were statistically analyzed by two-way analysis of variance with 95% confidence level. Results Different methods of enamel treatment caused a significant increase in elastic modulus compared to bleached group (P<0.05). Modulus was significantly increased in 1 and 2 months (P<0/001: bleach, P= 0/015: laser, P= 0/008: NHA, P=0/010: MI paste) but there were no significantly difference between 1 and 2 months (P>0.05). There was any significance difference for hardness among treated and control groups, but hardness increased significantly by increasing storage time (P<0.05). Conclusions The use of the protective tested agents can be useful in clinical practice to reduce negative changes of enamel surface after whitening procedures. Key words:Bleaching enamel, CO2 laser, MI pastes, Nano-hydroxy apatite, Microhardness, Elastic modulus. PMID:29410753

Elastic Modulus Determination of Normal and Glaucomatous Human Trabecular Meshwork

PubMed Central

Last, Julie A.; Pan, Tingrui; Ding, Yuzhe; Reilly, Christopher M.; Keller, Kate; Acott, Ted S.; Fautsch, Michael P.; Murphy, Christopher J.; Russell, Paul

2011-01-01

Purpose. Elevated intraocular pressure (IOP) is a risk factor for glaucoma. The principal outflow pathway for aqueous humor in the human eye is through the trabecular meshwork (HTM) and Schlemm's canal (SC). The junction between the HTM and SC is thought to have a significant role in the regulation of IOP. A possible mechanism for the increased resistance to flow in glaucomatous eyes is an increase in stiffness (increased elastic modulus) of the HTM. In this study, the stiffness of the HTM in normal and glaucomatous tissue was compared, and a mathematical model was developed to predict the impact of changes in stiffness of the juxtacanalicular layer of HTM on flow dynamics through this region. Methods. Atomic force microscopy (AFM) was used to measure the elastic modulus of normal and glaucomatous HTM. According to these results, a model was developed that simulated the juxtacanalicular layer of the HTM as a flexible membrane with embedded pores. Results. The mean elastic modulus increased substantially in the glaucomatous HTM (mean = 80.8 kPa) compared with that in the normal HTM (mean = 4.0 kPa). Regional variation was identified across the glaucomatous HTM, possibly corresponding to the disease state. Mathematical modeling suggested an increased flow resistance with increasing HTM modulus. Conclusions. The data indicate that the stiffness of glaucomatous HTM is significantly increased compared with that of normal HTM. Modeling exercises support substantial impairment in outflow facility with increased HTM stiffness. Alterations in the biophysical attributes of the HTM may participate directly in the onset and progression of glaucoma. PMID:21220561

Characterization of ultraviolet light cured polydimethylsiloxane films for low-voltage, dielectric elastomer actuators

NASA Astrophysics Data System (ADS)

Töpper, Tino; Wohlfender, Fabian; Weiss, Florian; Osmani, Bekim; Müller, Bert

2016-04-01

The reduction the operation voltage has been the key challenge to realize of dielectric elastomer actuators (DEA) for many years - especially for the application fields of robotics, lens systems, haptics and future medical implants. Contrary to the approach of manipulating the dielectric properties of the electrically activated polymer (EAP), we intend to realize low-voltage operation by reducing the polymer thickness to the range of a few hundred nanometers. A study recently published presents molecular beam deposition to reliably grow nanometer-thick polydimethylsiloxane (PDMS) films. The curing of PDMS is realized using ultraviolet (UV) radiation with wavelengths from 180 to 400 nm radicalizing the functional side and end groups. The understanding of the mechanical properties of sub-micrometer-thin PDMS films is crucial to optimize DEAs actuation efficiency. The elastic modulus of UV-cured spin-coated films is measured by nano-indentation using an atomic force microscope (AFM) according to the Hertzian contact mechanics model. These investigations show a reduced elastic modulus with increased indentation depth. A model with a skin-like SiO2 surface with corresponding elastic modulus of (2.29 +/- 0.31) MPa and a bulk modulus of cross-linked PDMS with corresponding elastic modulus of (87 +/- 7) kPa is proposed. The surface morphology is observed with AFM and 3D laser microscopy. Wrinkled surface microstructures on UV-cured PDMS films occur for film thicknesses above (510 +/- 30) nm with an UV-irradiation density of 7.2 10-4 J cm-2 nm-1 at a wavelength of 190 nm.

Material model measurements and predictions for a random pore poly(epsilon-caprolactone) scaffold.

PubMed

Quinn, T P; Oreskovic, T L; Landis, F A; Washburn, N R

2007-07-01

We investigated material models for a polymeric scaffold used for bone. The material was made by co-extruding poly(epsilon-caprolactone) (PCL), a biodegradable polyester, and poly(ethylene oxide) (PEO). The water soluble PEO was removed resulting in a porous scaffold. The stress-strain curve in compression was fit with a phenomenological model in hyperbolic form. This material model will be useful for designers for quasi-static analysis as it provides a simple form that can easily be used in finite element models. The ASTM D-1621 standard recommends using a secant modulus based on 10% strain. The resulting modulus has a smaller scatter in its value compared with the coefficients of the hyperbolic model, and it is therefore easier to compare differences in material processing and ensure quality of the scaffold. A prediction of the small-strain elastic modulus was constructed from images of the microstructure. Each pixel of the micrographs was represented with a brick finite element and assigned the Young's modulus of bulk PCL or a value of 0 for a pore. A compressive strain was imposed on the model and the resulting stresses were calculated. The elastic constants of the scaffold were then computed with Hooke's law for a linear-elastic isotropic material. The model was able to predict the small-strain elastic modulus measured in the experiments to within one standard deviation. Thus, by knowing the microstructure of the scaffold, its bulk properties can be predicted from the material properties of the constituents. Copyright 2006 Wiley Periodicals, Inc.

Estimation of the Young’s modulus of cellulose Iß by MM3 and quantum mechanics

USDA-ARS?s Scientific Manuscript database

Young’s modulus provides a measure of the resistance to deformation of an elastic material. In this study, modulus estimations for models of cellulose Iß relied on calculations performed with molecular mechanics (MM) and quantum mechanics (QM) programs. MM computations used the second generation emp...

Tensile elastic properties of 18:8 chromium-nickel steel as affected by plastic deformation

NASA Technical Reports Server (NTRS)

Mcadam, D J; Mebs, R W

1939-01-01

The relationship between stress and strain, and between stress and permanent set, for 18:8 alloy as affected by prior plastic deformation is discussed. Hysteresis and creep and their effects on the stress-strain and stress-set curves are also considered, as well as the influence of duration of the rest interval after cold work and the influence of plastic deformation on proof stresses, on the modulus of elasticity at zero stress, and on the curvature of the stress-strain line. A constant (c sub 1) is suggested to represent the variation of the modulus of elasticity with stress.

Improving impact resistance of ceramic materials by energy absorbing surface layers

NASA Technical Reports Server (NTRS)

Kirchner, H. P.; Seretsky, J.

1974-01-01

Energy absorbing surface layers were used to improve the impact resistance of silicon nitride and silicon carbide ceramics. Low elastic modulus materials were used. In some cases, the low elastic modulus was achieved using materials that form localized microcracks as a result of thermal expansion anisotropy, thermal expansion differences between phases, or phase transformations. In other cases, semi-vitreous or vitreous materials were used. Substantial improvements in impact resistance were observed at room and elevated temperatures.

A Focused Fundamental Study of Predicting Materials Degradation & Fatigue. Volume 1

DTIC Science & Technology

1997-05-31

physical properties are: bulk modulus, shear strength, coefficient of friction, modulus of elasticity/ rigidity and Poisson’s ratio. Each of these physical...acting on a subsurface crack when abrasive motion occurs on the surface using linear elastic fracture mechanics theory. Both mechanisms involve a...The body of the scattering 5 cell was a 4-way Swagelok*(Crawford Fitting Co., Solon, OH) connector with a 1.5 mm hole drilled in the top for

Density and mechanical properties of calcium aluminate cement

NASA Astrophysics Data System (ADS)

Ahmed, Syed Taqi Uddin; Ahmmad, Shaik Kareem

2018-04-01

Calcium aluminate cements are a special type of cements which have their composition mainly dominated by the presence of Monocalcium Aluminates. In the present paper for the first time we have shown theoretical density and elastic constants for various calcium aluminate cements. The density of the present CAS decrease with aluminates presents in the cement. Using the density data, the elastic moduli namely Young's modulus, bulk and shear modulus show strong linear dependence as a function of compositional parameter.

Substrate-dependent cell elasticity measured by optical tweezers indentation

NASA Astrophysics Data System (ADS)

Yousafzai, Muhammad S.; Ndoye, Fatou; Coceano, Giovanna; Niemela, Joseph; Bonin, Serena; Scoles, Giacinto; Cojoc, Dan

2016-01-01

In the last decade, cell elasticity has been widely investigated as a potential label free indicator for cellular alteration in different diseases, cancer included. Cell elasticity can be locally measured by pulling membrane tethers, stretching or indenting the cell using optical tweezers. In this paper, we propose a simple approach to perform cell indentation at pN forces by axially moving the cell against a trapped microbead. The elastic modulus is calculated using the Hertz-model. Besides the axial component, the setup also allows us to examine the lateral cell-bead interaction. This technique has been applied to measure the local elasticity of HBL-100 cells, an immortalized human cell line, originally derived from the milk of a woman with no evidence of breast cancer lesions. In addition, we have studied the influence of substrate stiffness on cell elasticity by performing experiments on cells cultured on two substrates, bare and collagen-coated, having different stiffness. The mean value of the cell elastic modulus measured during indentation was 26±9 Pa for the bare substrate, while for the collagen-coated substrate it diminished to 19±7 Pa. The same trend was obtained for the elastic modulus measured during the retraction of the cell: 23±10 Pa and 13±7 Pa, respectively. These results show the cells adapt their stiffness to that of the substrate and demonstrate the potential of this setup for low-force probing of modifications to cell mechanics induced by the surrounding environment (e.g. extracellular matrix or other cells).

Oxynitride glass fibers

NASA Technical Reports Server (NTRS)

Patel, Parimal J.; Messier, Donald R.; Rich, R. E.

1991-01-01

Research at the Army Materials Technology Laboratory (AMTL) and elsewhere has shown that many glass properties including elastic modulus, hardness, and corrosion resistance are improved markedly by the substitution of nitrogen for oxygen in the glass structure. Oxynitride glasses, therefore, offer exciting opportunities for making high modulus, high strength fibers. Processes for making oxynitride glasses and fibers of glass compositions similar to commercial oxide glasses, but with considerable enhanced properties, are discussed. We have made glasses with elastic moduli as high as 140 GPa and fibers with moduli of 120 GPa and tensile strengths up to 2900 MPa. AMTL holds a U.S. patent on oxynitride glass fibers, and this presentation discusses a unique process for drawing small diameter oxynitride glass fibers at high drawing rates. Fibers are drawn through a nozzle from molten glass in a molybdenum crucible at 1550 C. The crucible is situated in a furnace chamber in flowing nitrogen, and the fiber is wound in air outside of the chamber, making the process straightforward and commercially feasible. Strengths were considerably improved by improving glass quality to minimize internal defects. Though the fiber strengths were comparable with oxide fibers, work is currently in progress to further improve the elastic modulus and strength of fibers. The high elastic modulus of oxynitride glasses indicate their potential for making fibers with tensile strengths surpassing any oxide glass fibers, and we hope to realize that potential in the near future.

A small punch test technique for characterizing the elastic modulus and fracture behavior of PMMA bone cement used in total joint replacement.

PubMed

Giddings, V L; Kurtz, S M; Jewett, C W; Foulds, J R; Edidin, A A

2001-07-01

Polymethylmethacrylate (PMMA) bone cement is used in total joint replacements to anchor implants to the underlying bone. Establishing and maintaining the integrity of bone cement is thus of critical importance to the long-term outcome of joint replacement surgery. The goal of the present study was to evaluate the suitability of a novel testing technique, the small punch or miniaturized disk bend test, to characterize the elastic modulus and fracture behavior of PMMA. We investigated the hypothesis that the crack initiation behavior of PMMA during the small punch test was sensitive to the test temperature. Miniature disk-shaped specimens, 0.5 mm thick and 6.4 mm in diameter, were prepared from PMMA and Simplex-P bone cement according to manufacturers' instructions. Testing was conducted at ambient and body temperatures, and the effect of test temperature on the elastic modulus and fracture behavior was statistically evaluated using analysis of variance. For both PMMA materials, the test temperature had a significant effect on elastic modulus and crack initiation behavior. At body temperature, the specimens exhibited "ductile" crack initiation, whereas at room temperature "brittle" crack initiation was observed. The small punch test was found to be a sensitive and repeatable test method for evaluating the mechanical behavior of PMMA. In light of the results of this study, future small punch testing should be conducted at body temperature.

Nano and micro mechanical properties of uncross-linked and cross-linked chitosan films

PubMed Central

Aryaei, Ashkan; Jayatissa, Ahalapitiya H.; Jayasuriya, A. Champa

2016-01-01

The aim of this study is to determine the nano and micro mechanical properties for uncross-linked and cross-linked chitosan films. Specifically, we looked at nanoindentation hardness, microhardness, and elastic modulus. It is important to study the nano and microscale mechanical properties of chitosan since chitosan has been widely used for biomedical applications. Using the solvent-cast method, the chitosan films were prepared at room temperature on the cleaned glass plates. The chitosan solution was prepared by dissolving chitosan in acetic acid 1% (v/v). Tripolyphosphate (TPP) was used to create the cross-links between amine groups in chitosan and phosphate groups in TPP. In this study, atomic force microscopy was used to measure the nanoindentation hardness and surface topography of the uncross-linked and cross-linked chitosan films. Elastic modulus was then calculated from the nanoindentation results. The effective elastic modulus was determined by microhardness with some modifications to previous theories. The microhardness of the chitosan films were measured using Vicker’s hardness meter under three different loads. Our results show that the microhardness and elastic modulus for cross-linked chitosan films are higher than the uncross-linked films. However, the cross-linked chitosan films show increased brittleness when compared to uncross-linked films. By increasing the load magnitude, the microhardness increases for both uncross-linked and cross-linked chitosan films. PMID:22100082

Porous titanium materials with entangled wire structure for load-bearing biomedical applications.

PubMed

He, Guo; Liu, Ping; Tan, Qingbiao

2012-01-01

A kind of porous metal-entangled titanium wire material has been investigated in terms of the pore structure (size and distribution), the strength, the elastic modulus, and the mechanical behavior under uniaxial tensile loading. Its functions and potentials for surgical application have been explained. In particular, its advantages over competitors (e.g., conventional porous titanium) have been reviewed. In the study, a group of entangled titanium wire materials with non-woven structure were fabricated by using 12-180 MPa forming pressure, which have porosity in a range of 48%-82%. The pores in the materials are irregular in shape, which have a nearly half-normal distribution in size range. The yield strength, ultimate tensile strength, and elastic modulus are 75 MPa, 108 MPa, and 1.05 GPa, respectively, when its porosity is 44.7%. The mechanical properties decrease significantly as the porosity increases. When the porosity is 57.9%, these values become 24 MPa, 47.5 MPa, and 0.33 GPa, respectively. The low elastic modulus is due to the structural flexibility of the entangled titanium wire materials. For practical reference, a group of detailed data of the porous structure and the mechanical properties are reported. This kind of material is very promising for implant applications because of their very good toughness, perfect flexibility, high strength, adequate elastic modulus, and low cost. Copyright © 2011 Elsevier Ltd. All rights reserved.

PECVD silicon-rich nitride and low stress nitride films mechanical characterization using membrane point load deflection

NASA Astrophysics Data System (ADS)

Bagolini, Alvise; Picciotto, Antonino; Crivellari, Michele; Conci, Paolo; Bellutti, Pierluigi

2016-02-01

An analysis of the mechanical properties of plasma enhanced chemical vapor (PECVD) silicon nitrides is presented, using micro fabricated silicon nitride membranes under point load deflection. The membranes are made of PECVD silicon-rich nitride and low stress nitride films. The mechanical performance of the bended membranes is examined both with analytical models and finite element simulation in order to extract the elastic modulus and residual stress values. The elastic modulus of low stress silicon nitride is calculated using stress free analytical models, while for silicon-rich silicon nitride and annealed low stress silicon nitride it is estimated with a pre-stressed model of point-load deflection. The effect of annealing both in nitrogen and hydrogen atmosphere is evaluated in terms of residual stress, refractive index and thickness variation. It is demonstrated that a hydrogen rich annealing atmosphere induces very little change in low stress silicon nitride. Nitrogen annealing effects are measured and shown to be much higher in silicon-rich nitride than in low stress silicon nitride. An estimate of PECVD silicon-rich nitride elastic modulus is obtained in the range between 240-320 GPa for deposited samples and 390 GPa for samples annealed in nitrogen atmosphere. PECVD low stress silicon nitride elastic modulus is estimated to be 88 GPa as deposited and 320 GPa after nitrogen annealing.

Investigation of the elastic modulus, tensile and flexural strength of five skull simulant materials for impact testing of a forensic skin/skull/brain model.

PubMed

Falland-Cheung, Lisa; Waddell, J Neil; Chun Li, Kai; Tong, Darryl; Brunton, Paul

2017-04-01

Conducting in vitro research for forensic, impact and injury simulation modelling generally involves the use of a skull simulant with mechanical properties similar to those found in the human skull. For this study epoxy resin, fibre filled epoxy resin, 3D-printing filaments (PETG, PLA) and self-cure acrylic denture base resin were used to fabricate the specimens (n=20 per material group), according to ISO 527-2 IBB and ISO20795-1. Tensile and flexural testing in a universal testing machine was used to measure their tensile/flexural elastic modulus and strength. The results showed that the epoxy resin and fibre filled epoxy resin had similar tensile elastic moduli (no statistical significant difference) with lower values observed for the other materials. The fibre filled epoxy resin had a considerably higher flexural elastic modulus and strength, possibly attributed to the presence of fibres. Of the simulants tested, epoxy resin had an elastic modulus and flexural strength close to that of mean human skull values reported in the literature, and thus can be considered as a suitable skull simulant for a skin/skull/brain model for lower impact forces that do not exceed the fracture stress. For higher impact forces a 3D printing filament (PLA) may be a more suitable skull simulant material, due to its closer match to fracture stresses found in human skull bone. Influencing factors were also anisotropy, heterogeneity and viscoelasticity of human skull bone and simulant specimens. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dynamic analysis of bulk-fill composites: Effect of food-simulating liquids.

PubMed

Eweis, Ahmed Hesham; Yap, Adrian U-Jin; Yahya, Noor Azlin

2017-10-01

This study investigated the effect of food simulating liquids on visco-elastic properties of bulk-fill restoratives using dynamic mechanical analysis. One conventional composite (Filtek Z350 [FZ]), two bulk-fill composites (Filtek Bulk-fill [FB] and Tetric N Ceram [TN]) and a bulk-fill giomer (Beautifil-Bulk Restorative [BB]) were evaluated. Specimens (12 × 2 × 2mm) were fabricated using customized stainless steel molds. The specimens were light-cured, removed from their molds, finished, measured and randomly divided into six groups. The groups (n = 10) were conditioned in the following mediums for 7 days at 37°C: air (control), artificial saliva (SAGF), distilled water, 0.02N citric acid, heptane, 50% ethanol-water solution. Specimens were assessed using dynamic mechanical testing in flexural three-point bending mode and their respective mediums at 37°C and a frequency range of 0.1-10Hz. The distance between the supports were fixed at 10mm and an axial load of 5N was employed. Data for elastic modulus, viscous modulus and loss tangent were subjected to ANOVA/Tukey's tests at significance level p < 0.05. Significant differences in visco-elastic properties were observed between materials and mediums. Apart from bulk-fill giomer, elastic modulus was the highest after conditioning in heptane. No apparent trends were noted for viscous modulus. Generally, loss tangent was the highest after conditioning in ethanol. The effect of food-simulating liquids on the visco-elastic properties of bulk-fill composites was material and medium dependent. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of AlF3 on the Density and Elastic Properties of Zinc Tellurite Glass Systems

PubMed Central

Sidek, Haji Abdul Aziz; Rosmawati, Shaharuddin; Halimah, Mohamed Kamari; Matori, Khamirul Amin; Talib, Zainal Abidin

2012-01-01

This paper presents the results of the physical and elastic properties of the ternary zinc oxyfluoro tellurite glass system. Systematic series of glasses (AlF3)x(ZnO)y(TeO2)z with x = 0–19, y = 0–20 and z = 80, 85, 90 mol% were synthesized by the conventional rapid melt quenching technique. The composition dependence of the physical, mainly density and molar volume, and elastic properties is discussed in term of the AlF3 modifiers addition that are expected to produce quite substantial changes in their physical properties. The absence of any crystalline peaks in the X-ray diffraction (XRD) patterns of the present glass samples indicates the amorphous nature. The addition of AlF3 lowered the values of the densities in ternary oxyfluorotellurite glass systems. The longitudinal and transverse ultrasonic waves propagated in each glass sample were measured using a MBS8020 ultrasonic data acquisition system. All the velocity data were taken at 5 MHz frequency and room temperature. The longitudinal modulus (L), shear modulus (G), Young’s modulus (E), bulk modulus (K) and Poisson’s ratio (σ) are obtained from both velocities data and their respective density. Experimental data shows the density and elastic moduli of each AlF3-ZnO-TeO2 series are found strongly depend upon the glass composition. The addition of AlF3 modifiers into the zinc tellurite causes substantial changes in their density, molar volume as well as their elastic properties.

Development of Space Station strut design

NASA Technical Reports Server (NTRS)

Johnson, R. R.; Bluck, R. M.; Holmes, A. M. C.; Kural, M. H.

1986-01-01

Candidate Space Station struts exhibiting high stiffness (38-40 msi modulus of elasticity) were manufactured and experimentally evaluated. One and two inch diameter aluminum-clad evaluation specimens were manufactured using a unique dry fiber resin injection process. Preliminary tests were performed on strut elements having 80 percent high-modulus graphite epoxy and 20 percent aluminum. Performed tests included modulus of elasticity, thermal cycling, and coefficient of thermal expansion. The paper describes the design approach, including an analytical assessment of strut thermal deformation behavior. The major thrust of this paper is the manufacturing process which produces aluminum-clad struts with precisely controlled properties which can be fine-tuned after fabrication. An impact test and evaluation procedure for evaluating toughness is described.

First-principles calculations of the electronic, vibrational, and elastic properties of the magnetic laminate Mn₂GaC

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

Thore, A., E-mail: andth@ifm.liu.se; Dahlqvist, M., E-mail: madah@ifm.liu.se, E-mail: bjoal@ifm.liu.se, E-mail: johro@ifm.liu.se; Alling, B., E-mail: madah@ifm.liu.se, E-mail: bjoal@ifm.liu.se, E-mail: johro@ifm.liu.se

2014-09-14

In this paper, we report the by first-principles predicted properties of the recently discovered magnetic MAX phase Mn₂GaC. The electronic band structure and vibrational dispersion relation, as well as the electronic and vibrational density of states, have been calculated. The band structure close to the Fermi level indicates anisotropy with respect to electrical conductivity, while the distribution of the electronic and vibrational states for both Mn and Ga depend on the chosen relative orientation of the Mn spins across the Ga sheets in the Mn–Ga–Mn trilayers. In addition, the elastic properties have been calculated, and from the five elastic constants,more » the Voigt bulk modulus is determined to be 157 GPa, the Voigt shear modulus 93 GPa, and the Young's modulus 233 GPa. Furthermore, Mn₂GaC is found relatively elastically isotropic, with a compression anisotropy factor of 0.97, and shear anisotropy factors of 0.9 and 1, respectively. The Poisson's ratio is 0.25. Evaluated elastic properties are compared to theoretical and experimental results for M₂AC phases where M = Ti, V, Cr, Zr, Nb, Ta, and A = Al, S, Ge, In, Sn.« less

Elasticity of human embryonic stem cells as determined by atomic force microscopy.

PubMed

Kiss, Robert; Bock, Henry; Pells, Steve; Canetta, Elisabetta; Adya, Ashok K; Moore, Andrew J; De Sousa, Paul; Willoughby, Nicholas A

2011-10-01

The expansive growth and differentiation potential of human embryonic stem cells (hESCs) make them a promising source of cells for regenerative medicine. However, this promise is off set by the propensity for spontaneous or uncontrolled differentiation to result in heterogeneous cell populations. Cell elasticity has recently been shown to characterize particular cell phenotypes, with undifferentiated and differentiated cells sometimes showing significant differences in their elasticities. In this study, we determined the Young's modulus of hESCs by atomic force microscopy using a pyramidal tip. Using this method we are able to take point measurements of elasticity at multiple locations on a single cell, allowing local variations due to cell structure to be identified. We found considerable differences in the elasticity of the analyzed hESCs, reflected by a broad range of Young's modulus (0.05-10 kPa). This surprisingly high variation suggests that elasticity could serve as the basis of a simple and efficient large scale purification/separation technique to discriminate subpopulations of hESCs.

Elastic Properties of Lithium Disilicate Versus Feldspathic Inlays: Effect on the Bonding by 3D Finite Element Analysis.

PubMed

Trindade, Flávia Zardo; Valandro, Luiz Felipe; de Jager, Niek; Bottino, Marco Antônio; Kleverlaan, Cornelis Johannes

2016-10-03

To determine the elastic properties of five ceramic systems with different compositions (lithium disilicate vs. feldspathic ceramics) and processing methods and compare the stress distribution in premolars in the interface with inlays made with these systems loaded with the maximum normal bite force (665 N) using 3D finite element analysis (FEA). The elastic properties of five ceramic restoration materials (IPS e.max Press, IPS e.max CAD, Vita PM9, Vita Mark II, Vita VM7) were obtained using the ultrasonic pulse-echo method. Three-dimensional FEA simplified models of maxillary premolars restored with these ceramic materials were created. The models were loaded with a load at the two nodes on the occlusal surface in the middle of the tooth, 2 mm from the outside of the tooth, simulating a loading ball with a radius of 6 mm. The means values of density (g/cm³), Young's modulus (GPa), and Poison's ratio was 2.6 ± 0.3, 82.3 ± 18.3, and 0.22 ± 0.01 for IPS e.max Press; 2.3 ± 0.1, 83.5 ± 15.0, and 0.21 ± 0.01 for IPS e.max CAD; 2.5 ± 0.1, 44.4 ± 11.5, and 0.26 ± 0.08 for PM9; 2.4 ± 0.1, 70.6 ± 4.9, and 0.22 ± 0.01 for Vitamark II; 2.4 ± 0.1, 63.3 ± 3.9, and 0.23 ± 0.01 for VM7, respectively. The 3D FEA showed the tensile stress at the interface between the tooth and the inlay was dependent on the elastic properties of the materials, since the Vita PM9 and IPS e.max CAD ceramics presented the lowest and the highest stress concentration in the interface, respectively. The elastic properties of ceramic materials were influenced by composition and processing methods, and these differences influenced the stress concentration at the bonding interface between tooth and restoration. The lower the elastic modulus of inlays, the lower is the stress concentration at the bonding interfaces. © 2016 by the American College of Prosthodontists.

High strength, low stiffness, porous NiTi with superelastic properties.

PubMed

Greiner, Christian; Oppenheimer, Scott M; Dunand, David C

2005-11-01

Near-stoichiometric NiTi with up to 18% closed porosity was produced by expansion at 1200 degrees C of argon-filled pores trapped by powder metallurgy within a NiTi billet. When optimally heat-treated, NiTi with 6-16% porosity exhibits superelasticity, with recoverable compressive strains up to 6% at a maximum compressive stress up to 1700 MPa. The apparent Young's modulus of NiTi with 16% porosity, measured during uniaxial compression, is in the range of 15-25 GPa (similar to human bone), but is much lower than measured ultrasonically (approximately 40 GPa), or predicted from continuum elastic mechanics. This effect is attributed to the reversible stress-induced transformation contributing to the linear elastic deformation of porous NiTi. The unique combination of low stiffness, high strength, high recoverable strains and large energy absorption of porous superelastic NiTi, together with the known biocompatibility of NiTi, makes this material attractive for bone-implant applications.

High-pressure structural, elastic, and electronic properties of the scintillator host material KMgF3

NASA Astrophysics Data System (ADS)

Vaitheeswaran, G.; Kanchana, V.; Kumar, Ravhi S.; Cornelius, A. L.; Nicol, M. F.; Svane, A.; Delin, A.; Johansson, B.

2007-07-01

The high-pressure structural behavior of the fluoroperovskite KMgF3 is investigated by theory and experiment. Density functional calculations were performed within the local density approximation and the generalized gradient approximation for exchange and correlation effects, as implemented within the full-potential linear muffin-tin orbital method. In situ high-pressure powder x-ray diffraction experiments were performed up to a maximum pressure of 40GPa using synchrotron radiation. We find that the cubic Pm3¯m crystal symmetry persists throughout the pressure range studied. The calculated ground state properties—the equilibrium lattice constant, bulk modulus, and elastic constants—are in good agreement with experimental results. By analyzing the ratio between the bulk and shear moduli, we conclude that KMgF3 is brittle in nature. Under ambient conditions, KMgF3 is found to be an indirect gap insulator, with the gap increasing under pressure.

Further studies on gold alloys used in fabrication of porcelain-fused-to-metal restorations.

PubMed

Civjan, S; Huget, E F; Dvivedi, N; Cosner, H J

1975-03-01

Composition, microstructure, castability, mechanical properties, and heat treatment characteristics of two gold-palladium-silver-based alloys were studied. The materials exhibited compositional as well as microstructural differences. Clinically acceptable castings could not be obtained when manufacturers' recommended casting temperatures were used. Ultimate tensile strength, yield strength, modulus of elasticity, and Brinell hardness values for the alloys were comparable. The elastic limit of Cameo, however, was significantly higher than that of vivo-star. Maximum rehardening of annealed castings occurred on reheat treatment at temperatures between 1,200 and 1,300 F. As-cast specimens, however, were not heat hardenable. The sequence of heat treatments used in the application of porcelain reduced slightly the hardness of both alloys. Hardness of the metal substructures was not increased by return of porcelain-coated specimens to a 1,250 F oven for final heat treatment.

Temperature dependence of the elastic moduli and damping for polycrystalline LiF-22 pct CaF2 eutectic salt

NASA Technical Reports Server (NTRS)

Wolfenden, A.; Lastrapes, G.; Duggan, M. B.; Raj, S. V.

1991-01-01

Young's and shear moduli and damping were measured for as-cast polycrystalline LiF-(22 mol pct)CaF2 eutectic specimens as a function of temperature using the piezoelectric ultrasonic composite oscillator technique. The shear modulus decreased with increasing temperature from about 40 GPa at 295 K to about 30 GPa at 1000 K, while the Young modulus decreased from about 115 GPa at 295 K to about 35 GPa at 900 K. These values are compared with those derived from the rule of mixtures using elastic moduli data for LiF and CaF2 single crystals. It is shown that, while the shear modulus data agree reasonably well with the predicted trend, there is a large discrepancy between the theoretical calculations and the Young modulus values, where this disagreement increases with increasing temperature.

The optimal density of cellular solids in axial tension.

PubMed

Mihai, L Angela; Alayyash, Khulud; Wyatt, Hayley

2017-05-01

For cellular bodies with uniform cell size, wall thickness, and shape, an important question is whether the same volume of material has the same effect when arranged as many small cells or as fewer large cells. To answer this question, for finite element models of periodic structures of Mooney-type material with different structural geometry and subject to large strain deformations, we identify a nonlinear elastic modulus as the ratio between the mean effective stress and the mean effective strain in the solid cell walls, and show that this modulus increases when the thickness of the walls increases, as well as when the number of cells increases while the volume of solid material remains fixed. Since, under the specified conditions, this nonlinear elastic modulus increases also as the corresponding mean stress increases, either the mean modulus or the mean stress can be employed as indicator when the optimum wall thickness or number of cells is sought.

Dynamics of an elastic sphere containing a thin creeping region and immersed in an acoustic region for similar viscous-elastic and acoustic time- and length-scales

NASA Astrophysics Data System (ADS)

Gat, Amir; Friedman, Yonathan

2017-11-01

The characteristic time of low-Reynolds number fluid-structure interaction scales linearly with the ratio of fluid viscosity to solid Young's modulus. For sufficiently large values of Young's modulus, both time- and length-scales of the viscous-elastic dynamics may be similar to acoustic time- and length-scales. However, the requirement of dominant viscous effects limits the validity of such regimes to micro-configurations. We here study the dynamics of an acoustic plane wave impinging on the surface of a layered sphere, immersed within an inviscid fluid, and composed of an inner elastic sphere, a creeping fluid layer and an external elastic shell. We focus on configurations with similar viscous-elastic and acoustic time- and length-scales, where the viscous-elastic speed of interaction between the creeping layer and the elastic regions is similar to the speed of sound. By expanding the linearized spherical Reynolds equation into the relevant spectral series solution for the hyperbolic elastic regions, a global stiffness matrix of the layered elastic sphere was obtained. This work relates viscous-elastic dynamics to acoustic scattering and may pave the way to the design of novel meta-materials with unique acoustic properties. ISF 818/13.

Charge-regularized swelling kinetics of polyelectrolyte gels: Elasticity and diffusion

NASA Astrophysics Data System (ADS)

Sen, Swati; Kundagrami, Arindam

2017-11-01

We apply a recently developed method [S. Sen and A. Kundagrami, J. Chem. Phys. 143, 224904 (2015)], using a phenomenological expression of osmotic stress, as a function of polymer and charge densities, hydrophobicity, and network elasticity for the swelling of spherical polyelectrolyte (PE) gels with fixed and variable charges in a salt-free solvent. This expression of stress is used in the equation of motion of swelling kinetics of spherical PE gels to numerically calculate the spatial profiles for the polymer and free ion densities at different time steps and the time evolution of the size of the gel. We compare the profiles of the same variables obtained from the classical linear theory of elasticity and quantitatively estimate the bulk modulus of the PE gel. Further, we obtain an analytical expression of the elastic modulus from the linearized expression of stress (in the small deformation limit). We find that the estimated bulk modulus of the PE gel decreases with the increase of its effective charge for a fixed degree of deformation during swelling. Finally, we match the gel-front locations with the experimental data, taken from the measurements of charged reversible addition-fragmentation chain transfer gels to show an increase in gel-size with charge and also match the same for PNIPAM (uncharged) and imidazolium-based (charged) minigels, which specifically confirms the decrease of the gel modulus value with the increase of the charge. The agreement between experimental and theoretical results confirms general diffusive behaviour for swelling of PE gels with a decreasing bulk modulus with increasing degree of ionization (charge). The new formalism captures large deformations as well with a significant variation of charge content of the gel. It is found that PE gels with large deformation but same initial size swell faster with a higher charge.

Finite element analysis for transverse carpal ligament tensile strain and carpal arch area.

PubMed

Yao, Yifei; Erdemir, Ahmet; Li, Zong-Ming

2018-05-17

Mechanics of carpal tunnel soft tissue, such as fat, muscle and transverse carpal ligament (TCL), around the median nerve may render the median nerve vulnerable to compression neuropathy. The purpose of this study was to understand the roles of carpal tunnel soft tissue mechanical properties and intratunnel pressure on the TCL tensile strain and carpal arch area (CAA) using finite element analysis (FEA). Manual segmentation of the thenar muscles, skin, fat, TCL, hamate bone, and trapezium bone in the transverse plane at distal carpal tunnel were obtained from B-mode ultrasound images of one cadaveric hand. Sensitivity analyses were conducted to examine the dependence of TCL tensile strain and CAA on TCL elastic modulus (0.125-10 MPa volar-dorsally; 1.375-110 MPa transversely), skin-fat and thenar muscle initial shear modulus (1.6-160 kPa for skin-fat; 0.425-42.5 kPa for muscle), and intratunnel pressure (60-480 mmHg). Predictions of TCL tensile strain under different intratunnel pressures were validated with the experimental data obtained on the same cadaveric hand. Results showed that skin, fat and muscles had little effect on the TCL tensile strain and CAA changes. However, TCL tensile strain and CAA increased with decreased elastic modulus of TCL and increased intratunnel pressure. The TCL tensile strain and CAA increased linearly with increased pressure while increased exponentially with decreased elastic modulus of TCL. Softening the TCL by decreasing the elastic modulus may be an alternative clinical approach to carpal tunnel expansion to accommodate elevated intratunnel pressure and alleviate median nerve compression neuropathy. Copyright © 2018 Elsevier Ltd. All rights reserved.

The effects of nail rigidity on fracture healing in rats with osteoporosis

PubMed Central

Sha, Mo; Fu, Jun; Li, Jing; Fan Yuan, Chao; Shi, Lei; Jun Li, Shu

2009-01-01

Background and purpose Stress shielding from rigid internal fixation may lead to refracture after removal of the osteosynthesis material. We investigated the effect of a low-rigidity (Ti-24Nb-4Zr-7.9Sn) intramedullary nail regarding stress shielding and bone healing of osteoporotic fractures in the rat. Methods 40 female Sprague-Dawley rats, aged 3 months, were divided into the following groups: sham-operation (SHAM) (n = 10), ovariectomized (OVX) (n = 10) and OVX-fracture (n = 20). 10 SHAM rats and 10 OVX rats were killed after 12 weeks to provide biomechanical data. Ovariectomy was performed 12 weeks before fracturing both femurs in 20 rats. The left fracture was stabilized with a high-rigidity titanium alloy pin (Ti-6Al-4V; elastic modulus 110 GPa) and the right with a low-rigidity (Ti-24Nb-4Zr-7.9Sn; elastic modulus 33 GPa). The bony calluses were examined by micro-CT at 6 and 12 weeks after fracture, bone volume (BV) and total volume (TV) were determined at the callus region (ROI1) and the total femur (ROI2). Subsequently, the bones were tested mechanically by a three-point bending test. Results In the low-rigidity group, TV (ROI1) increased at 6 weeks, but BV (ROI1), BV (ROI2) were similar but maximum load increased. At 12 weeks, the maximum load and also BV (ROI1, ROI2) were increased in the low-rigidity group. Interpretation The low-rigidity nail manufactured from Ti-24Nb-4Zr-7.9Sn showed better external callus formation, seemed to reduce effects of stress shielding, and reduced bone resorption better than the stiffer nail. The low-rigidity nail was strong enough to maintain alignment of the fracture in the osteoporotic rat model without delayed union. PMID:19297794

Stress analysis of irradiated human tooth enamel using finite element methods

PubMed Central

Thiagarajan, Ganesh; Vizcarra, Bruno; Bodapudi, Venkata; Reed, Rachel; Seyedmahmoud, Rasoul; Wang, Yong; Gorski, Jeffrey P.; Walker, Mary P.

2017-01-01

The objectives of this project were to use finite element methods to determine how changes in the elastic modulus due to oral cancer therapeutic radiation alter the distribution of mechanical stresses in teeth and to determine if observed failures in irradiated teeth correlate with changes in mechanical stresses. A thin slice section finite element (FE) model was constructed from micro CT sections of a molar tooth using MIMICS and 3-Matic software. This model divides the tooth into three enamel regions, the dentin-enamel junction (DEJ) and dentin. The enamel elastic modulus was determined in each region using nano indentation for three experimental groups namely – control (non-radiated), in vitro irradiated (simulated radiotherapy following tooth extraction) and in vivo irradiated (extracted subsequent to oral cancer patient radiotherapy) teeth. Physiological loads were applied to the tooth models at the buccal and lingual cusp regions for all three groups (control, in vitro and in vivo). The principal tensile stress and the maximum shear stress were used to compare the results from different groups since it has been observed in previous studies that delamination of enamel from the underlying dentin was one of the major reasons for the failure of teeth following therapeutic radiation. From the FE data, we observed an increase in the principal tensile stress within the inner enamel region of in vivo irradiated teeth (9.97 ± 1.32 MPa) as compared to control/non-irradiated teeth (8.44 ± 1.57 MPa). Our model predicts that failure occurs at the inner enamel/DEJ interface due to extremely high tensile and maximum shear stresses in in vivo irradiated teeth which could be a cause of enamel delamination due to radiotherapy. PMID:29063816

Stress analysis of irradiated human tooth enamel using finite element methods.

PubMed

Thiagarajan, Ganesh; Vizcarra, Bruno; Bodapudi, Venkata; Reed, Rachel; Seyedmahmoud, Rasoul; Wang, Yong; Gorski, Jeffrey P; Walker, Mary P

2017-11-01

The objectives of this project were to use finite element methods to determine how changes in the elastic modulus due to oral cancer therapeutic radiation alter the distribution of mechanical stresses in teeth and to determine if observed failures in irradiated teeth correlate with changes in mechanical stresses. A thin slice section finite element (FE) model was constructed from micro CT sections of a molar tooth using MIMICS and 3-Matic software. This model divides the tooth into three enamel regions, the dentin-enamel junction (DEJ) and dentin. The enamel elastic modulus was determined in each region using nano indentation for three experimental groups namely - control (non-radiated), in vitro irradiated (simulated radiotherapy following tooth extraction) and in vivo irradiated (extracted subsequent to oral cancer patient radiotherapy) teeth. Physiological loads were applied to the tooth models at the buccal and lingual cusp regions for all three groups (control, in vitro and in vivo). The principal tensile stress and the maximum shear stress were used to compare the results from different groups since it has been observed in previous studies that delamination of enamel from the underlying dentin was one of the major reasons for the failure of teeth following therapeutic radiation. From the FE data, we observed an increase in the principal tensile stress within the inner enamel region of in vivo irradiated teeth (9.97 ± 1.32 MPa) as compared to control/non-irradiated teeth (8.44 ± 1.57 MPa). Our model predicts that failure occurs at the inner enamel/DEJ interface due to extremely high tensile and maximum shear stresses in in vivo irradiated teeth which could be a cause of enamel delamination due to radiotherapy.

Regional variation in tissue composition and biomechanical properties of postmenopausal ovine and human vagina.

PubMed

Ulrich, Daniela; Edwards, Sharon L; Letouzey, Vincent; Su, Kai; White, Jacinta F; Rosamilia, Anna; Gargett, Caroline E; Werkmeister, Jerome A

2014-01-01

There are increasing numbers of reports describing human vaginal tissue composition in women with and without pelvic organ prolapse with conflicting results. The aim of this study was to compare ovine and human posterior vaginal tissue in terms of histological and biochemical tissue composition and to assess passive biomechanical properties of ovine vagina to further characterise this animal model for pelvic organ prolapse research. Vaginal tissue was collected from ovariectomised sheep (n = 6) and from postmenopausal women (n = 7) from the proximal, middle and distal thirds. Tissue histology was analyzed using Masson's Trichrome staining; total collagen was quantified by hydroxyproline assays, collagen III/I+III ratios by delayed reduction SDS PAGE, glycosaminoglycans by dimethylmethylene blue assay, and elastic tissue associated proteins (ETAP) by amino acid analysis. Young's modulus, maximum stress/strain, and permanent strain following cyclic loading were determined in ovine vagina. Both sheep and human vaginal tissue showed comparable tissue composition. Ovine vaginal tissue showed significantly higher total collagen and glycosaminoglycan values (p<0.05) nearest the cervix. No significant differences were found along the length of the human vagina for collagen, GAG or ETAP content. The proximal region was the stiffest (Young's modulus, p<0.05), strongest (maximum stress, p<0.05) compared to distal region, and most elastic (permanent strain). Sheep tissue composition and mechanical properties showed regional differences along the postmenopausal vaginal wall not apparent in human vagina, although the absolute content of proteins were similar. Knowledge of this baseline variation in the composition and mechanical properties of the vaginal wall will assist future studies using sheep as a model for vaginal surgery.

Elastic properties of single-walled carbon nanotube thin film by nanoindentation test.

PubMed

Tang, Xingling; El-Hami, Abdelkhalak; El-Hami, Khalil; Eid, Mohamed; Si, Chaorun

2017-09-12

This paper carries out a preliminary study for the elastic properties of single walled carbon nanotube (SWCNT) thin film. The SWCNT thin films (~250 nm) are prepared by a simple and cost effective method of spin-coating technology. Nanoindentation test with a Berkovich indenter is used to determine the hardness and elastic modulus of the SWCNT thin film. It is important to note that the elastic properties of SWCNT film are indirectly derived from the information of load and displacement of the indenter under certain assumptions, deviation of the 'test value' is inevitable. In this regard, uncertainty analysis is an effective process in guarantying the validity of the material properties. This paper carries out uncertainty estimation for the tested elastic properties of SWCNT film by nanoindentation. Experimental results and uncertainty analysis indicates that nanoindentation test could be an effective and reliable method in determine the elastic properties of SWCNT thin film. Moreover, the obtained values of hardness and elastic modulus can further benefit the design of SWCNT thin film based components.

Elastic energy distribution in bi-material lithosphere: implications for shear zone formation

NASA Astrophysics Data System (ADS)

So, B.; Yuen, D. A.

2013-12-01

Shear instability in the lithosphere can cause mechanical rupturing such as slab detachment and deep focus earthquake. Recent studies reported that bi-material interface, which refers to sharp elastic modulus contrast, plays an important role in triggering the instability [So and Yuen et al., 2012, GJI]. In present study, we performed two-dimensional numerical simulations to investigate the distribution of thermal-mechanical energy within the bi-material lithosphere. Under the far-field constant compression exerted on the domain, a larger elastic energy is accumulated into the compliant part than stiff medium. For instance, the compliant part has two times greater elastic energy density than surrounding stiff part, when the elastic modulus contrast between two different parts is five. Although these elastic energies in both parts are conversed into thermal energies after plastic yielding, denser elastic energy in the compliant is released more efficiently. This leads to efficient strength weakening and the subsequent ductile shear zone in the compliant part. We propose that strong shear heating occurs in lithosphere with the bi-material interface due to locally non-uniform distribution of the energy around the interface.

Effects of Vacancy Concentration and Temperature on Mechanical Properties of Single-Crystal γ-TiAl Based on Molecular Dynamics Simulation

NASA Astrophysics Data System (ADS)

Ruicheng, Feng; Hui, Cao; Haiyan, Li; Zhiyuan, Rui; Changfeng, Yan

2018-01-01

Molecular dynamics simulation is used to analyze tensile strength and elastic modulus under different temperatures and vacancy concentrations. The effects of temperature and vacancy concentration on the mechanical properties of γ-TiAl alloy are investigated. The results show that the ultimate stress, ultimate strain and elastic modulus decrease nonlinearly with increasing temperature and vacancy concentration. As the temperature increases, the plastic of material is reinforced. The influence of temperature on strength and elastic modulus is larger than that of vacancy concentration. The evolution process of vacancy could be observed clearly. Furthermore, vacancies with different concentrations develop into voids first as a function of external forces or other factors, micro cracks evolve from those voids, those micro cracks then converge to a macro crack, and fracture will finally occur. The vacancy evolution process cannot be observed clearly owing to the thermal motion of atoms at high temperature. In addition, potential energy is affected by both temperature and vacancy concentration.

Nanoindentation study of bulk zirconium hydrides at elevated temperatures

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

Cinbiz, Mahmut Nedim; Balooch, Mehdi; Hu, Xunxiang

Here, the mechanical properties of zirconium hydrides was studied using nano-indentation technique at a temperature range of 25 – 400 °C. Temperature dependency of reduced elastic modulus and hardness of δ- and ε-zirconium hydrides were obtained by conducting nanoindentation experiments on the bulk hydride samples with independently heating capability of indenter and heating stage. The reduced elastic modulus of δ-zirconium hydride (H/Zr ratio =1.61) decreased from ~113 GPa to ~109 GPa while temperature increased from room temperature to 400°C. For ε-zirconium hydrides (H/Zr ratio=1.79), the reduced elastic modulus decreased from 61 GPa to 54 GPa as temperature increased from roommore » temperature to 300 °C. Whereas, hardness of δ-zirconium hydride significantly decreased from 4.1 GPa to 2.41 GPa when temperature increased from room temperature to 400 °C. Similarly, hardness of ε-zirconium hydride decreased from 3.06 GPa to 2.19 GPa with temperature increase from room temperature to 300°C.« less

Nanoindentation study of bulk zirconium hydrides at elevated temperatures

DOE PAGES

Cinbiz, Mahmut Nedim; Balooch, Mehdi; Hu, Xunxiang; ...

2017-08-02

Here, the mechanical properties of zirconium hydrides was studied using nano-indentation technique at a temperature range of 25 – 400 °C. Temperature dependency of reduced elastic modulus and hardness of δ- and ε-zirconium hydrides were obtained by conducting nanoindentation experiments on the bulk hydride samples with independently heating capability of indenter and heating stage. The reduced elastic modulus of δ-zirconium hydride (H/Zr ratio =1.61) decreased from ~113 GPa to ~109 GPa while temperature increased from room temperature to 400°C. For ε-zirconium hydrides (H/Zr ratio=1.79), the reduced elastic modulus decreased from 61 GPa to 54 GPa as temperature increased from roommore » temperature to 300 °C. Whereas, hardness of δ-zirconium hydride significantly decreased from 4.1 GPa to 2.41 GPa when temperature increased from room temperature to 400 °C. Similarly, hardness of ε-zirconium hydride decreased from 3.06 GPa to 2.19 GPa with temperature increase from room temperature to 300°C.« less

Fracture Toughness and Elastic Modulus of Epoxy-Based Nanocomposites with Dopamine-Modified Nano-Fillers

PubMed Central

Koh, Kwang Liang; Ji, Xianbai; Lu, Xuehong; Lau, Soo Khim; Chen, Zhong

2017-01-01

This paper examines the effect of surface treatment and filler shape factor on the fracture toughness and elastic modulus of epoxy-based nanocomposite. Two forms of nanofillers, polydopamine-coated montmorillonite clay (D-clay) and polydopamine-coated carbon nanofibres (D-CNF) were investigated. It was found that Young’s modulus increases with increasing D-clay and D-CNF loading. However, the fracture toughness decreases with increased D-clay loading but increases with increased D-CNF loading. Explanations have been provided with the aid of fractographic analysis using electron microscope observations of the crack-filler interactions. Fractographic analysis suggests that although polydopamine provides a strong adhesion between the fillers and the matrix, leading to enhanced elastic stiffness, the enhancement prohibits energy release via secondary cracking, resulting in a decrease in fracture toughness. In contrast, 1D fibre is effective in increasing the energy dissipation during fracture through crack deflection, fibre debonding, fibre break, and pull-out. PMID:28773136

Structural and elastic properties of AIBIIIC 2 VI semiconductors

NASA Astrophysics Data System (ADS)

Kumar, V.; Singh, Bhanu P.

2018-01-01

The plane wave pseudo-potential method within density functional theory has been used to calculate the structural and elastic properties of AIBIIIC 2 VI semiconductors. The electronic band structure, density of states, lattice constants (a and c), internal parameter (u), tetragonal distortion (η), energy gap (Eg), and bond lengths of the A-C (dAC) and B-C (dBC) bonds in AIBIIIC 2 VI semiconductors have been calculated. The values of elastic constants (Cij), bulk modulus (B), shear modulus (G), Young's modulus (Y), Poisson's ratio (υ), Zener anisotropy factor (A), Debye temperature (ϴD) and G/B ratio have also been calculated. The values of all 15 parameters of CuTlS2 and CuTlSe2 compounds, and 8 parameters of 20 compounds of AIBIIIC 2 VI family, except AgInS2 and AgInSe2, have been calculated for the first time. Reasonably good agreement has been obtained between the calculated, reported and available experimental values.

Elasticity and anelasticity of microcrystalline aluminum samples having various deformation and thermal histories

NASA Astrophysics Data System (ADS)

Betekhtin, V. I.; Kadomtsev, A. G.; Kardashev, B. K.

2006-08-01

The effect of the amplitude of vibrational deformation on the elastic modulus and internal friction of microcrystalline aluminum samples produced by equal-channel angular pressing was studied. The samples have various deformation and thermal histories. The elastic and inelastic (microplastic) properties of the samples are investigated. As the degree of plastic deformation increases, the Young’s modulus E, the amplitude-independent decrement δi, and the microplastic flow stress σ increase. As the annealing temperature increases, the quantities δi and σ decrease noticeably and the modulus E exhibits a more complex behavior. The experimental data are discussed under the assumption that the dislocation mobility depends on both the spectrum of point defects and the internal stresses, whose level is determined by the degree of plastic deformation and the temperature of subsequent annealing. The concept of internal stresses is also used to analyze the data on the effect of the degree of deformation and annealing on the rupture strength of the samples.

Elasticity-dependent fast underwater adhesion demonstrated by macroscopic supramolecular assembly.

PubMed

Ju, Guannan; Cheng, Mengjiao; Guo, Fengli; Zhang, Qian; Shi, Feng

2018-05-30

Macroscopic supramolecular assembly (MSA) is a recent progress in supramolecular chemistry to associate visible building blocks through non-covalent interactions in a multivalent manner. Although various substrates (e. g. hydrogels, rigid materials) have been used, a general design rule of building blocks in MSA systems and interpretation of the assembly mechanism are still lacking and urgently in demand. Here we design three model systems with varied modulus and correlated the MSA probability with the elasticity. Based on the effects of substrate deformability on multivalency, we have proposed an elastic-modulus-dependent rule that building blocks below a critical modulus of 2.5 MPa can achieve MSA for the used host/guest system. Moreover, this MSA rule applies well to the design of materials applicable for fast underwater adhesion: Soft substrates (0.5 MPa) can achieve underwater adhesion within 10 s with one magnitude higher strength than that of rigid substrates (2.5 MPa). © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High pressure phase transformation in uranium carbide: A first principle study

NASA Astrophysics Data System (ADS)

Sahoo, B. D.; Joshi, K. D.; Gupta, Satish C.

2013-02-01

First principles calculations have been carried out to analyze structural, elastic and dynamic stability, of UC under hydrostatic compression. The comparison of enthalpies of rocksalt type (B1) and body centered orthorhombic (bco) structures as a function of pressure suggests the B1 →bco transition at ˜ 23 GPa, in good agreement with experimental value of 27 GPa. From the lattice dynamic calculations we have determined the phonon dispersion relations for B1 phase at various compressions. It is found that TA phonon branch along Γ-X direction becomes imaginary around the transition pressure. Further, the phonon instability so caused is of long wavelength nature as it occurs near the Brillouin zone centre. This long wavelength phonon instability at the transition point indicates that the B1 →bco transition is driven by elastic failure (the vanishing of C44 modulus). Various physical quantities such as equilibrium volume, bulk modulus, pressure derivative of bulk modulus and elastic constants have been determined at zero pressure and compared with data available in literature.

The effect of boron concentration on the structure and elastic properties of Ru-Ir alloys: first-principles calculations

NASA Astrophysics Data System (ADS)

Li, Xiaolong; Zhou, Zhaobo; Hu, Riming; Zhou, Xiaolong; Yu, Jie; Liu, Manmen

2018-04-01

The Phase stability, electronic structure, elastic properties and hardness of Ru-Ir alloys with different B concentration were investigated by first principles calculations. The calculated formation enthaplies and cohesive energies show that these compounds are all thermodynamically stable. Information on electronic structure indicates that they possess metallic characteristic and Ru-Ir-B alloys were composed of the Ru-B and Ir-B covalent bond. The elastic properties were calculated, which included bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio and hardness. The calculated results reveal that the plastic of Ru-Ir-B alloys increase with the increase of the content of B atoms, but the hardness of Ru-Ir-B alloys have no substantial progress with the increase of the content of B atoms. However, it is interesting that the hardness of the Ru-Ir-B compound was improved obviously as the B content was higher than 18 atoms because of a phase structure transition.

Geometrical and material parameters to assess the macroscopic mechanical behaviour of fresh cranial bone samples.

PubMed

Auperrin, Audrey; Delille, Rémi; Lesueur, Denis; Bruyère, Karine; Masson, Catherine; Drazétic, Pascal

2014-03-21

The present study aims at providing quantitative data for the personalisation of geometrical and mechanical characteristics of the adult cranial bone to be applied to head FE models. A set of 351 cranial bone samples, harvested from 21 human skulls, were submitted to three-point bending tests at 10 mm/min. For each of them, an apparent elastic modulus was calculated using the beam's theory and a density-dependant beam inertia. Thicknesses, apparent densities and percentage of ash weight were also measured. Distributions of characteristics among the different skull bones show their symmetry and their significant differences between skull areas. A data analysis was performed to analyse potential relationship between thicknesses, densities and the apparent elastic modulus. A specific regression was pointed out to estimate apparent elastic modulus from the product of thickness by apparent density. These results offer quantitative tools in view of personalising head FE models and thus improve definition of local injury criteria for this body part. Copyright © 2014 Elsevier Ltd. All rights reserved.

First-principles calculations of the structural, elastic and thermodynamic properties of mackinawite (FeS) and pyrite (FeS2)

NASA Astrophysics Data System (ADS)

Wen, Xiangli; Liang, Yuxuan; Bai, Pengpeng; Luo, Bingwei; Fang, Teng; Yue, Luo; An, Teng; Song, Weiyu; Zheng, Shuqi

2017-11-01

The thermodynamic properties of Fe-S compounds with different crystal structure are very different. In this study, the structural, elastic and thermodynamic properties of mackinawite (FeS) and pyrite (FeS2) were investigated by first-principles calculations. Examination of the electronic density of states shows that mackinawite (FeS) is metallic and that pyrite (FeS2) is a semiconductor with a band gap of Eg = 1.02 eV. Using the stress-strain method, the elastic properties including the bulk modulus and shear modulus were derived from the elastic Cij data. Density functional perturbation theory (DFPT) calculations within the quasi-harmonic approximation (QHA) were used to calculate the thermodynamic properties, and the two Fe-S compounds are found to be dynamically stable. The isothermal bulk modulus, thermal expansion coefficient, heat capacities, Gibbs free energy and entropy of the Fe-S compounds are obtained by first-principles phonon calculations. Furthermore, the temperature of the mackinawite (FeS) ⟶ pyrite (FeS2) phase transition at 0 GPa was predicted. Based on the calculation results, the model for prediction of Fe-S compounds in the Fe-H2S-H2O system was improved.

Tolerance to structural disorder and tunable mechanical behavior in self-assembled superlattices of polymer-grafted nanocrystals

DOE PAGES

Gu, X. Wendy; Ye, Xingchen; Koshy, David M.; ...

2017-02-27

Large, freestanding membranes with remarkably high elastic modulus ( > 10 GPa) have been fabricated through the self-Assembly of ligand-stabilized inorganic nanocrystals, even though these nanocrystals are connected only by soft organic ligands (e.g., dodecanethiol or DNA) that are not cross-linked or entangled. Recent developments in the synthesis of polymer-grafted nanocrystals have greatly expanded the library of accessible superlattice architectures,which allows superlattice mechanical behavior to be linked to specific structural features. Here, colloidal self-Assembly is used to organize polystyrene-grafted Au nanocrystals at a fluid interface to form ordered solids with sub-10-nm periodic features. We used thin-film buckling and nanoindentation tomore » evaluate the mechanical behavior of polymer-grafted nanocrystal superlattices while exploring the role of polymer structural conformation, nanocrystal packing, and superlattice dimensions. Superlattices containing 3-20 vol % Au are found to have an elastic modulus of ~6-19 GPa, and hardness of ~120-170 MPa. We also found that rapidly self-Assembled superlattices have the highest elastic modulus, despite containing significant structural defects. Polymer extension, interdigitation, and grafting density are determined to be critical parameters that govern superlattice elastic and plastic deformation.« less

The effects of a 4-week static stretching programme on the individual muscles comprising the hamstrings.

PubMed

Ichihashi, Noriaki; Umegaki, Hiroki; Ikezoe, Tome; Nakamura, Masatoshi; Nishishita, Satoru; Fujita, Kosuke; Umehara, Jun; Nakao, Sayaka; Ibuki, Satoko

2016-12-01

The aims of this study were to investigate the effects of a 4-week intervention of static stretching (SS) on muscle hardness of the semitendinosus (ST), semimembranosus (SM) and biceps femoris (BF) muscles. Shear elastic modulus was measured by using ultrasound shear wave elastography as the index of muscle hardness. Thirty healthy men (age 22.7 ± 2.2 years) volunteered for this study and were randomly assigned to the SS intervention group (n = 15) or the control group (n = 15). Participants in the SS intervention group received a 4-week stretch intervention for the hamstrings of their dominant leg. Shear elastic moduli of the hamstrings were measured at initial evaluation and after 4 weeks in both groups at a determined angle. In all muscles, the shear elastic modulus decreased significantly after SS intervention. The percentage change in the shear elastic modulus from the value at initial evaluation to after 4 weeks intervention was greatest in the SM. These results suggest that SS intervention has chronic effects on reducing hardness of the hamstring muscle components, especially the SM muscle.

Elastic properties, reaction kinetics, and structural relaxation of an epoxy resin polymer during cure

NASA Astrophysics Data System (ADS)

Heili, Manon; Bielawski, Andrew; Kieffer, John

The cure kinetics of a DGEBA/DETA epoxy is investigated using concurrent Raman and Brillouin light scattering. Raman scattering allows us to monitor the in-situ reaction and quantitatively assess the degree of cure. Brillouin scattering yields the elastic properties of the system, providing a measure of network connectivity. We show that the adiabatic modulus evolves non-uniquely as a function of cure degree, depending on the cure temperature and the molar ratio of the epoxy. Two mechanisms contribute to the increase in the elastic modulus of the material during curing. First, there is the formation of covalent bonds in the network during the curing process. Second, following bond formation, the epoxy undergoes structural relaxation toward an optimally packed network configuration, enhancing non-bonded interactions. We investigate to what extent the non-bonded interaction contribution to structural rigidity in cross-linked polymers is reversible, and to what extent it corresponds to the difference between adiabatic and isothermal moduli obtained from static tensile, i.e. the so-called relaxational modulus. To this end, we simultaneously measure the adiabatic and isothermal elastic moduli as a function of applied strain and deformation rate.

Tolerance to structural disorder and tunable mechanical behavior in self-assembled superlattices of polymer-grafted nanocrystals

NASA Astrophysics Data System (ADS)

Gu, X. Wendy; Ye, Xingchen; Koshy, David M.; Vachhani, Shraddha; Hosemann, Peter; Alivisatos, A. Paul

2017-03-01

Large, freestanding membranes with remarkably high elastic modulus (>10 GPa) have been fabricated through the self-assembly of ligand-stabilized inorganic nanocrystals, even though these nanocrystals are connected only by soft organic ligands (e.g., dodecanethiol or DNA) that are not cross-linked or entangled. Recent developments in the synthesis of polymer-grafted nanocrystals have greatly expanded the library of accessible superlattice architectures, which allows superlattice mechanical behavior to be linked to specific structural features. Here, colloidal self-assembly is used to organize polystyrene-grafted Au nanocrystals at a fluid interface to form ordered solids with sub-10-nm periodic features. Thin-film buckling and nanoindentation are used to evaluate the mechanical behavior of polymer-grafted nanocrystal superlattices while exploring the role of polymer structural conformation, nanocrystal packing, and superlattice dimensions. Superlattices containing 3-20 vol % Au are found to have an elastic modulus of ˜6-19 GPa, and hardness of ˜120-170 MPa. We find that rapidly self-assembled superlattices have the highest elastic modulus, despite containing significant structural defects. Polymer extension, interdigitation, and grafting density are determined to be critical parameters that govern superlattice elastic and plastic deformation.

Base course resilient modulus for the mechanistic-empirical pavement design guide : [summary].

DOT National Transportation Integrated Search

2011-01-01

Elastic modulus determination is often used in designing pavements and evaluating pavement performance. The Mechanistic-Empirical Pavement Design Guide (MEPDG) has become an important source of guidance for pavement design and rehabilitation. MEPDG r...

The influence of the cumulated deformation energy in the measurement by the DSI method on the selected mechanical properties of bone tissues.

PubMed

Makuch, Anna M; Skalski, Konstanty R; Pawlikowski, Marek

2017-01-01

The goal of the study was to determine the influence of DSI test conditions, i.e., loading/unloading rates, hold time, and the value of the maximum loading force on selected mechanical properties of trabecular bone tissue. The test samples were resected from a femoral head of a patient qualified for a hip replacement surgery. During the DSI tests hardness (HV, HM, HIT) and elastic modulus (EIT) of trabecular bone tissue were measured using the Micro Hardness Tester (MHT, CSEM). The analysis of the results of measurements and the calculations of total energy, i.e., elastic and inelastic (Wtotal, Welastic, Winelastic) and those of hardness and elasticity made it possible to assess the impact of the process parameters (loading velocity, force and hold time) on mechanical properties of bone structures at a microscopic level. The coefficient k dependent on the EIT/HIT ratio and on the stored energy (ΔW = Wtotal - Welastic) is a measure of the material reaction to the loading and the deformation of tissue.

Method of measuring material properties of rock in the wall of a borehole

DOEpatents

Overmier, David K.

1985-01-01

To measure the modulus of elasticity of the rock in the wall of a borehole, a plug is cut in the borehole wall. The plug, its base attached to the surrounding rock, acts as a short column in response to applied forces. A loading piston is applied to the top of the plug and compression of the plug is measured as load is increased. Measurement of piston load and plug longitudinal deformation are made to determine the elastic modulus of the plug material. Poisson's ratio can be determined by simultaneous measurements of longitudinal and lateral deformation of the plug in response to loading. To determine shear modulus, the top of the plug is twisted while measurements are taken of torsional deformation.

Method of measuring material properties of rock in the wall of a borehole

DOEpatents

Overmier, D.K.

1984-01-01

To measure the modulus of elasticity of the rock in the wall of a borehole, a plug is cut in the borehole wall. The plug, its base attached to the surrounding rock, acts as a short column in response to applied forces. A loading piston is applied to the top of the plug and compression of the plug is measured as load is increased. Measurements of piston load and plug longitudinal deformation are made to determine the elastic modulus of the plug material. Poisson's ratio can be determined by simultaneous measurements of longitudinal and lateral deformation of the plug in response to loading. To determine shear modulus, the top of the plug is twisted while measurements are taken of torsional deformation.

Young's modulus and internal friction of the SiC/Si biomorphic composite based on the sapele wood precursor

NASA Astrophysics Data System (ADS)

Kardashev, B. K.; Orlova, T. S.; Smirnov, B. I.; de Arellano-Lopez, A. R.; Martinez-Fernandez, J.

2009-04-01

The effect of the vibrational strain amplitude on the Young’s modulus and ultrasound absorption (internal friction) of a SiC/Si biomorphic composite prepared by pyrolysis of sapele wood followed by infiltration of silicon were investigated. The studies were conducted in air and in vacuum by the acoustic resonance method with the use of a composite vibrator in longitudinal vibrations at frequencies of about 100 kHz. Measurements performed on sapele wood-based bio-SiC/Si samples revealed a substantial effect of adsorption-desorption of molecules contained in air on the effective elasticity modulus and elastic vibration decrement. Microplastic characteristics of the SiC/Si composites prepared from wood of different tree species were compared.

Readily fiberizable glasses having a high modulus of elasticity

NASA Technical Reports Server (NTRS)

Bacon, J. F.

1970-01-01

New glass compositions yield composites having higher moduli of elasticity and specific moduli of elasticity than commercially available glasses. Over a reasonable temperature range the glasses have a viscosity of about 20,000 poises. They consist of silica, alumina, magnesia, and beryllia, plus at least one uncommon oxide.

Simulation of hydrocephalus condition in infant head

NASA Astrophysics Data System (ADS)

Wijayanti, Erna; Arif, Idam

2014-03-01

Hydrocephalus is a condition of an excessive of cerebrospinal fluid in brain. In this paper, we try to simulate the behavior of hydrocephalus conditions in infant head by using a hydro-elastic model which is combined with orthotropic elastic skull and with the addition of suture that divide the skull into two lobes. The model then gives predictions for the case of stenosis aqueduct by varying the cerebral aqueduct diameter, time constant and brain elastic modulus. The hydrocephalus condition which is shown by the significant value of ventricle displacement, as the result shows, is occurred when the aqueduct is as resistant as brain parenchyma for the flow of cerebrospinal fluid. The decrement of brain elastic modulus causes brain parenchyma displacement value approach ventricle displacement value. The smaller of time constant value causes the smaller value of ventricle displacement.

Elastic, mechanical, and thermodynamic properties of Bi-Sb binaries: Effect of spin-orbit coupling

NASA Astrophysics Data System (ADS)

Singh, Sobhit; Valencia-Jaime, Irais; Pavlic, Olivia; Romero, Aldo H.

2018-02-01

Using first-principles calculations, we systematically study the elastic stiffness constants, mechanical properties, elastic wave velocities, Debye temperature, melting temperature, and specific heat of several thermodynamically stable crystal structures of BixSb1 -x (0

Low Velocity Sphere Impact of a Soda Lime Silicate Glass

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

Wereszczak, Andrew A; Fox, Ethan E; Morrissey, Timothy G

2011-10-01

This report summarizes TARDEC-sponsored work at Oak Ridge National Laboratory (ORNL) during the FY11 involving low velocity (< 30 m/s or < 65 mph) ball impact testing of Starphire soda lime silicate glass. The intent was to better understand low velocity impact response in the Starphire for sphere densities that bracketed that of rock. Five sphere materials were used: borosilicate glass, soda-lime silicate glass, steel, silicon nitride, and alumina. A gas gun was fabricated to produce controlled velocity delivery of the spheres against Starphire tile targets. Minimum impact velocities to initiate fracture in the Starphire were measured and interpreted inmore » context to the kinetic energy of impact and the elastic property mismatch between the any of the five sphere-Starphire-target combinations. The primary observations from this low velocity (< 30 m/s or < 65 mph) testing were: (1) Frictional effects contribute to fracture initiation. (2) Spheres with a lower elastic modulus require less force to initiate fracture in the Starphire than spheres with a higher elastic modulus. (3) Contact-induced fracture did not initiate in the Starphire SLS for impact kinetic energies < 150 mJ. Fracture sometimes initiated or kinetic energies between {approx} 150-1100 mJ; however, it tended to occur when lower elastic modulus spheres were impacting it. Contact-induced fracture would always occur for impact energies > 1100 mJ. (4) The force necessary to initiate contact-induced fracture is higher under dynamic or impact conditions than it is under quasi-static indentation conditions. (5) Among the five used sphere materials, silicon nitride was the closest match to 'rock' in terms of both density and (probably) elastic modulus.« less

Gelling ability of kefiran in the presence of sucrose and fructose and physicochemical characterization of the resulting cryogels.

PubMed

Zavala, Lucía; Roberti, Paula; Piermaria, Judith A; Abraham, Analía G

2015-08-01

In this work, the influence of sucrose and fructose on the gel-forming capacity of kefiran was investigated as well as the physicochemical characteristics of the resulting gels. The addition of sugar to gel-forming solutions did not alter the pseudoplastic flow properties of kefiran solutions and after one freeze-thaw cycle translucent gels with high water-holding capability were obtained. A highly porous matrix was revealed by microscopy whose pore size varied with sugar concentration. Sucrose and fructose had different effects on the rheological characteristics of sugar-kefiran gels. An increment in the strength of the gels with progressive concentrations of sucrose was evidenced by an increase in the elastic modulus (G'), indicating that sucrose reinforces the binding interactions between the polymer molecules (p ≤ 0.05). A drastic reduction in elastic modulus occurred, however, when 50.0 % w/w sucrose was added to kefiran gels, resulting in less elasticity. In contrast, when fructose was added to kefiran gels, elastic modulus decreased slightly with progressive sugar concentrations up to 10 %, thereafter increasing up to 50 % (p ≤ 0.05). Supplementation with up to 30 % sugar contributed to water retention and increased the viscous modulus. The relative increment in the elastic and viscous moduli elevated the loss tangent (tanδ) depending on the type and concentration of sugar. Sugars (sucrose, fructose) present in the matrix of the polysaccharide networks modified water-polymer and polymer-polymer interactions and consequently changed the gels' physicochemical characteristics, thus allowing the possibility of selecting the appropriate formulation through tailor-made kefiran cryogels.

Biomechanics of isolated tomato (Solanum lycopersicum L.) fruit cuticles: the role of the cutin matrix and polysaccharides.

PubMed

López-Casado, Gloria; Matas, Antonio J; Domínguez, Eva; Cuartero, Jesús; Heredia, Antonio

2007-01-01

The mechanical characteristics of the cuticular membrane (CM), a complex composite biopolymer basically composed of a cutin matrix, waxes, and hydrolysable polysaccharides, have been described previously. The biomechanical behaviour and quantitative contribution of cutin and polysaccharides have been investigated here using as experimental material mature green and red ripe tomato fruits. Treatment of isolated CM with anhydrous hydrogen fluoride in pyridine allowed the selective elimination of polysaccharides attached to or incrusted into the cutin matrix. Cutin samples showed a drastic decrease in elastic modulus and stiffness (up to 92%) compared with CM, which clearly indicates that polysaccharides incorporated into the cutin matrix are responsible for the elastic modulus, stiffness, and the linear elastic behaviour of the whole cuticle. Reciprocally, the viscoelastic behaviour of CM (low elastic modulus and high strain values) can be assigned to the cutin. These results applied both to mature green and red ripe CM. Cutin elastic modulus, independently of the degree of temperature and hydration, was always significantly higher for the ripe than for the green samples while strain was lower; the amount of phenolics in the cutin network are the main candidates to explain the increased rigidity from mature green to red ripe cutin. The polysaccharide families isolated from CM were pectin, hemicellulose, and cellulose, the main polymers associated with the plant cell wall. The three types of polysaccharides were present in similar amounts in CM from mature green and red ripe tomatoes. Physical techniques such as X-ray diffraction and Raman spectroscopy indicated that the polysaccharide fibres were mainly randomly oriented. A tomato fruit CM scenario at the supramolecular level that could explain the observed CM biomechanical properties is presented and discussed.

Study on rheological properties of CMC/Eu-Tb solutions with different concentrations

NASA Astrophysics Data System (ADS)

Fu, Z. C.; Ye, J.; Xiong, J.

2018-05-01

The rheological properties of polymer solution are sensitive to variations in the polymer structure. Carboxymethyl cellulose (CMC) aqueous solution has been used in many fields, such as food, medicine and paper industry. In this paper, the effects of different concentrations (2% - 6%) of CMC/Eu-Tb on their rheological properties were investigeted, including steady-state flow and viscoelastic response. The results show that, the viscosity of CMC/Eu-Tb is lower than that of CMC, at the same concentrations; the products solutions present a nearly Newtonian behavior at the low concentrations (2% - 3%); while at the higher concentrations (4% - 6%), the products solutions present a pseudoplastic behavior; shear-thinning behavior is due to the polymer chains unravel under the action of flow and the molecular chains are oriented in the flow direction. The results also show that the viscosity of the solutions decreases with increasing temperature. Dynamic rheological tests show that CMC/Eu-Tb has viscoelasticity in the concentrations of 2% - 6%. At lower concentrations, the elastic modulus G‧ is slightly higher than the viscous modulus G″, and as the concentrations increase, the elastic modulus G‧ is significantly higher than the viscous modulus G″. It means that at the lower solution concentrations, the solutions tend to be less elastic and easier to flow. Most of the energies are lost through the viscous flow. As the solution concentrations increase, the solutions tend to be more elastic, and the system tends to form a gel.

Examining platelet-fibrin interactions during traumatic shock in a swine model using platelet contractile force and clot elastic modulus.

PubMed

White, Nathan J; Martin, Erika J; Brophy, Donald F; Ward, Kevin R

2011-07-01

A significant proportion of severely injured patients develop early coagulopathy, characterized by abnormal clot formation, which impairs resuscitation and increases mortality. We have previously demonstrated an isolated decrease in clot strength by thrombelastography in a swine model of nonresuscitated traumatic shock. In order to more closely examine platelet-fibrin interactions in this setting, we define the observed decrease in clot strength in terms of platelet-induced clot contraction and clot elastic modulus using the Hemostasis Analysis System (HAS) (Hemodyne Inc., Richmond, Virginia, USA). Whole blood was sampled for HAS measurements, metabolic measurements, cell counts, and fibrinogen concentration at baseline prior to injury and again at a predetermined level of traumatic shock defined by oxygen debt. Male swine (N=17) received femur fracture and controlled arterial hemorrhage to achieve an oxygen debt of 80 ml/kg. Platelet counts were unchanged, but fibrinogen concentration was reduced significantly during shock (167.6 vs. 66.7 mg/dl, P=0.0007). Platelet contractile force generated during clot formation did not change during shock (11.7 vs. 10.4 kdynes, P=0.41), but clot elastic modulus was dynamically altered, resulting in a lower final value (22.9 vs. 17.3 kdynes/cm, P<0.0001). In this model of traumatic shock, platelet function was preserved, whereas terminal clot elastic modulus was reduced during shock in a manner most consistent with early changes in the mechanical properties of the developing fibrin fiber network.

Effect of structural evolution on mechanical properties of ZrO2 coated Ti-6Al-7Nb-biomedical application

NASA Astrophysics Data System (ADS)

Zalnezhad, E.

2016-05-01

Zirconia (ZrO2) nanotube arrays were fabricated by anodizing pure zirconium (Zr) coated Ti-6Al-7Nb in fluoride/glycerol electrolyte at a constant potential of 60 V for different times. Zr was deposited atop Ti-6Al-7Nb via a physical vapor deposition magnetron sputtering (PVDMS) technique. Structural investigations of coating were performed utilizing X-ray diffraction (XRD) analysis. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to characterize the morphology and microstructure of coatings. Unannealed ZrO2 nanotube arrays were amorphous. Monoclinic and tetragonal ZrO2 appeared when the coated substrates were heat treated at 450 °C and 650 °C, while monoclinic ZrO2 was found at 850 °C and 900 °C. Mechanical properties, including nanohardness and modulus of elasticity, were evaluated at different annealing temperatures using a nanoindentation test. The nanoindentation results show that the nanohardness and modulus of elasticity for Ti-6AL-7Nb increased by annealing ZrO2 coated substrate at 450 °C. The nanohardness and modulus of elasticity for coated substrate decreased with annealing temperatures of 650, 850, and 900 °C. At an annealing temperature of 900 °C, cracks in the ZrO2 thin film coating occurred. The highest nanohardness and elastic modulus values of 6.34 and 218 GPa were achieved at an annealing temperature of 450 °C.

The changes of red blood cell viscoelasticity and sports anemia in male 24-hr ultra-marathoners.

PubMed

Liu, Che-Hung; Tseng, Yen-Fang; Lai, Jiun-I; Chen, Yin-Quan; Wang, Shih-Hao; Kao, Wei-Fong; Li, Li-Hua; Chiu, Yu-Hui; How, Chorng-Kuang; Chang, Wen-Han

2018-05-01

In endurance sports, stress, dehydration and release of chemical factors have been associated with red blood cell (RBC) alterations of structure and function, which may contribute to sports anemia, a well-observed phenomenon during long-distance running. Until now, the investigation of the changes of viscoelastic properties of RBC membrane, a decisive factor of RBC deformability to avoid hemolysis, is lacking, especially in an Oriental population. nineteen runners were prospectively recruited into our study. Hematological parameters were analyzed before and immediately after the 2015 Taipei 24H Ultra-Marathon Festival, Taiwan. Video particle tracking microrheology was used to determine viscoelastic properties of each RBC sample by calculating the dynamic elastic modulus G'(f) and the viscous modulus G″(f) at frequency f = 20 Hz. Haptoglobin, RBC count, hemoglobin, hematocrit, mean cell hemoglobin, plasma free hemoglobin and unsaturated iron-binding capacity values of the recruited runners showed a statistically significant drop in the post-race values. Blood concentration of reticulocyte and ferritin were significantly higher at post-race compared with pre-race. 15 out of the 19 runners had a concurrent change in the elastic and the viscous moduli of their RBCs. Changes in the elastic and the viscous moduli were correlated with changes in the RBC count, hemoglobin and hematocrit. Viscoelasticity properties, the elastic modulus G'(f) and the viscous modulus G″(f) of RBCs are associated with endurance exercise-induced anemia. Copyright © 2017. Published by Elsevier Taiwan LLC.

Biomimicry in biomedical research

PubMed Central

Zhang, Ge

2012-01-01

Biomimicry (literally defined as the imitation of life or nature) has sparked a variety of human innovations and inspired countless cutting-edge designs. From spider silk-made artificial skin to lotus leaf-inspired self-cleaning materials, biomimicry endeavors to solve human problems. Biomimetic approaches have contributed significantly to advances biomedical research during recent years. Using polyacrylamide gels to mimic the elastic modulus of different biological tissues, Disher’s lab has directed meschymal stem cell differentiation into specific lineages.1 They have shown that soft substrates mimicking the elastic modulus of brain tissues (0.1~1 kPa) were neurogenic, substrates of intermediate elastic modulus mimicking muscle (8 ~17 kPa) were myogenic, and substrates with bone-like elastic modulus (25~40 kPa) were osteogenic. This work represents a novel way to regulate the fate of stem cells and exerts profound influence on stem cell research. Biomimcry also drives improvements in tissue engineering. Novel scaffolds have been designed to capture extracellular matrix-like structures, binding of ligands, sustained release of cytokines, and mechanical properties intrinsic to specific tissues for tissue engineering applications.2,3 For example, tissue engineering skin grafts have been designed to mimic the cell composition and layered structure of native skin.4 Similarly, in the field of regenerative medicine, researchers aim to create biomimetic scaffolds to mimic the properties of a native stem cell environment (niche) to dynamically interact with the entrapped stem cells and direct their response.5 PMID:23275257

Evaluation of Metakaolin and Slag for GDOT Concrete Specifications and Mass Concrete Provision - Phase I

DOT National Transportation Integrated Search

2017-11-01

This report documents the evaluation of cement replacement with mekaolin and slag materials supplied by multiple vendors by measuring compressive strength, tensile strength, modulus of rupture, modulus of elasticity, sulfate expansion, alkali-silica ...

Mechanical, Anisotropic, and Electronic Properties of XN (X = C, Si, Ge): Theoretical Investigations.

PubMed

Ma, Zhenyang; Liu, Xuhong; Yu, Xinhai; Shi, Chunlei; Wang, Dayun

2017-08-08

The structural, mechanical, elastic anisotropic, and electronic properties of Pbca -XN (X = C, Si, Ge) are investigated in this work using the Perdew-Burke-Ernzerhof (PBE) functional, Perdew-Burke-Ernzerhof for solids (PBEsol) functional, and Ceperly and Alder, parameterized by Perdew and Zunger (CA-PZ) functional in the framework of density functional theory. The achieved results for the lattice parameters and band gap of Pbca -CN with the PBE functional in this research are in good accordance with other theoretical results. The band structures of Pbca -XN (X = C, Si, Ge) show that Pbca -SiN and Pbca -GeN are both direct band gap semiconductor materials with a band gap of 3.39 eV and 2.22 eV, respectively. Pbca -XN (X = C, Si, Ge) exhibits varying degrees of mechanical anisotropic properties with respect to the Poisson's ratio, bulk modulus, shear modulus, Young's modulus, and universal anisotropic index. The (001) plane and (010) plane of Pbca -CN/SiN/GeN both exhibit greater elastic anisotropy in the bulk modulus and Young's modulus than the (100) plane.

A study of the influence of micro and nano phase morphology on the mechanical properties of a rubber-modified epoxy resin

NASA Astrophysics Data System (ADS)

Russell, Bobby Glenn

Epoxy resins are thermosets with extraordinary adhesion; high strength; good resistance to creep, heat, and chemicals; and they have low shrinkage. Conversely, these polymers are brittle, they are sensitive to moisture, and they exhibit poor toughness. To improve their toughness, they are often modified by introducing dispersed rubber particles in the primary phase. In this study, the epoxy resin was modified with carboxyl-terminated butadiene acrylonitrile (CTBN), liquid-reactive rubbers. The initiator concentration, percent acrylonitrile in the CTBN rubber, and cure temperatures were altered to give varying materials properties. Statistical analysis of the morphology data showed that the percentage of rubber acrylonitrile had an effect on both the rubber particle size and volume fraction. The cure temperature had an effect on the rubber particle volume and modulus. Plots of the rubber particle size, volume fraction, and modulus versus bulk elastic storage modulus and fracture toughness revealed that rubber particle size had no effect on bulk properties, volume fraction and rubber particle modulus had an effect on both the bulk storage elastic modulus and fracture toughness.

Mechanical, Anisotropic, and Electronic Properties of XN (X = C, Si, Ge): Theoretical Investigations

PubMed Central

Ma, Zhenyang; Liu, Xuhong; Yu, Xinhai; Shi, Chunlei; Wang, Dayun

2017-01-01

The structural, mechanical, elastic anisotropic, and electronic properties of Pbca-XN (X = C, Si, Ge) are investigated in this work using the Perdew–Burke–Ernzerhof (PBE) functional, Perdew–Burke–Ernzerhof for solids (PBEsol) functional, and Ceperly and Alder, parameterized by Perdew and Zunger (CA–PZ) functional in the framework of density functional theory. The achieved results for the lattice parameters and band gap of Pbca-CN with the PBE functional in this research are in good accordance with other theoretical results. The band structures of Pbca-XN (X = C, Si, Ge) show that Pbca-SiN and Pbca-GeN are both direct band gap semiconductor materials with a band gap of 3.39 eV and 2.22 eV, respectively. Pbca-XN (X = C, Si, Ge) exhibits varying degrees of mechanical anisotropic properties with respect to the Poisson’s ratio, bulk modulus, shear modulus, Young’s modulus, and universal anisotropic index. The (001) plane and (010) plane of Pbca-CN/SiN/GeN both exhibit greater elastic anisotropy in the bulk modulus and Young’s modulus than the (100) plane. PMID:28786960

Dynamic Simulation of VEGA SRM Bench Firing By Using Propellant Complex Characterization

NASA Astrophysics Data System (ADS)

Di Trapani, C. D.; Mastrella, E.; Bartoccini, D.; Squeo, E. A.; Mastroddi, F.; Coppotelli, G.; Linari, M.

2012-07-01

During the VEGA launcher development, from the 2004 up to now, 8 firing tests have been performed at Salto di Quirra (Sardinia, Italy) and Kourou (Guyana, Fr) with the objective to characterize and qualify of the Zefiros and P80 Solid Rocket Motors (SRM). In fact the VEGA launcher configuration foreseen 3 solid stages based on P80, Z23 and Z9 Solid Rocket Motors respectively. One of the primary objectives of the firing test is to correctly characterize the dynamic response of the SRM in order to apply such a characterization to the predictions and simulations of the VEGA launch dynamic environment. Considering that the solid propellant is around 90% of the SRM mass, it is very important to dynamically characterize it, and to increase the confidence in the simulation of the dynamic levels transmitted to the LV upper part from the SRMs. The activity is articulated in three parts: • consolidation of an experimental method for the dynamic characterization of the complex dynamic elasticity modulus of elasticity of visco-elastic materials applicable to the SRM propellant operative conditions • introduction of the complex dynamic elasticity modulus in a numerical FEM benchmark based on MSC NASTRAN solver • analysis of the effect of the introduction of the complex dynamic elasticity modulus in the Zefiros FEM focusing on experimental firing test data reproduction with numerical approach.

First-principles calculations of stability, electronic and elastic properties of the precipitates present in 7055 aluminum alloy

NASA Astrophysics Data System (ADS)

Huang, Cheng; Shao, Hongbang; Ma, Yunlong; Huang, Yuanchun; Xiao, Zhengbing

2018-04-01

The structural stability, electronic structures and elastic properties of the strengthening precipitates, namely Al3Zr, MgZn2, Al2CuMg and Al2Cu, present in 7055 aluminum alloy were investigated by the first-principles calculations based on density functional theory (DFT). The optimized structural parameters are in good agreement with literature values available. It is found that Al3Zr has the strongest alloying ability and structural stability, while for MgZn2, its structural stability is the worst. The calculated electronic results indicate that covalent bonding is the dominant cohesion of Al3Zr, whereas the fractional ionic interactions coexisting with metallic bonding are found in MgZn2, Al2CuMg and Al2Cu. The elastic constants Cij of these precipitates were calculated, and the bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio and universal elastic anisotropy were derived. It is suggested that MgZn2 is ductile, whereas Al3Zr, Al2CuMg and Al2Cu are brittle, and the elastic anisotropies of them increase in the following sequence: Al3Zr

Measurement of elastic pp scattering at $$\\sqrt{\\hbox {s}} = \\hbox {8}$$ TeV in the Coulomb–nuclear interference region: Determination of the ρ-parameter and the total cross-section

DOE PAGES

Antchev, G.; Aspell, P.; Atanassov, I.; ...

2016-11-30

Here, the TOTEM experiment at the CERN LHC has measured elastic proton–proton scattering at the centre-of-mass energy s√=8TeV and four-momentum transfers squared, |t|, from 6 × 10 –4 to 0.2 GeV 2. Near the lower end of the t-interval the differential cross-section is sensitive to the interference between the hadronic and the electromagnetic scattering amplitudes. This article presents the elastic cross-section measurement and the constraints it imposes on the functional forms of the modulus and phase of the hadronic elastic amplitude. The data exclude the traditional Simplified West and Yennie interference formula that requires a constant phase and a purelymore » exponential modulus of the hadronic amplitude. For parametrisations of the hadronic modulus with second- or third-order polynomials in the exponent, the data are compatible with hadronic phase functions giving either central or peripheral behaviour in the impact parameter picture of elastic scattering. In both cases, the ρ-parameter is found to be 0.12±0.03. The results for the total hadronic cross-section are σ tot = (102.9±2.3) mb and (103.0±2.3) mb for central and peripheral phase formulations, respectively. Both are consistent with previous TOTEM measurements.« less

MR-ARFI-based method for the quantitative measurement of tissue elasticity: application for monitoring HIFU therapy

NASA Astrophysics Data System (ADS)

Vappou, Jonathan; Bour, Pierre; Marquet, Fabrice; Ozenne, Valery; Quesson, Bruno

2018-05-01

Monitoring thermal therapies through medical imaging is essential in order to ensure that they are safe, efficient and reliable. In this paper, we propose a new approach, halfway between MR acoustic radiation force imaging (MR-ARFI) and MR elastography (MRE), allowing for the quantitative measurement of the elastic modulus of tissue in a highly localized manner. It relies on the simulation of the MR-ARFI profile, which depends on tissue biomechanical properties, and on the identification of tissue elasticity through the fitting of experimental displacement images measured using rapid MR-ARFI. This method was specifically developed to monitor MR-guided high intensity focused ultrasound (MRgHIFU) therapy. Elasticity changes were followed during HIFU ablations (N  =  6) performed ex vivo in porcine muscle samples, and were compared to temperature changes measured by MR-thermometry. Shear modulus was found to increase consistently and steadily a few seconds after the heating started, and such changes were found to be irreversible. The shear modulus was found to increase from 1.49  ±  0.48 kPa (before ablation) to 3.69  ±  0.93 kPa (after ablation and cooling). Thanks to its ability to perform quantitative elasticity measurements in a highly localized manner around the focal spot, this method proved to be particularly attractive for monitoring HIFU ablations.

Effect of cholesterol lowering on stiffness of aortic and femoral arterial walls in rabbits on a high fat diet.

PubMed

Xue, Li; Xu, Wan-Hai; Xu, Jin-Zhi; Zhang, Tong; Bi, Hong-Yuan; Shen, Bao-Zhong

2009-06-20

Researches in arterial elasticity have increased over the past few years. We investigated the effects of simvastatin on vascular stiffness in fat fed rabbits by ultrasonography. Thirty rabbits were assigned randomly to 3 groups: normal control group (A), the cholesterol group (B), simvastatin group (C: high fat diet for 4 weeks and high fat diet + simvastatin for further 4 weeks). Stiffness coefficient, pressure strain elastic modulus and velocity of pulse waves in abdominal aorta and femoral artery were measured by ultrasonographic echo tracking at the end of the 4th and the 8th weeks. At the end of the 4th week, stiffness coefficient, pressure strain elastic modulus and pulse wave velocity of femoral artery were significantly increased in group B compared with those in group A. Similarly, at the end of the 8th week, the same parameters of abdominal aorta were significantly increased in group B compared with those in group A. In contrast, stiffness coefficient, pressure strain elastic modulus and pulse wave velocity of femoral artery were significantly decreased in group C compared with those in group B, however, there was no significant difference in parameters of abdominal aorta between groups B and C. Short term administration of simvastatin can improve the elasticity of femoral artery but not abdominal aorta.

Mechanisms governing the visco-elastic responses of living cells assessed by foam and tensegrity models.

PubMed

Cañadas, P; Laurent, V M; Chabrand, P; Isabey, D; Wendling-Mansuy, S

2003-11-01

The visco-elastic properties of living cells, measured to date by various authors, vary considerably, depending on the experimental methods and/or on the theoretical models used. In the present study, two mechanisms thought to be involved in cellular visco-elastic responses were analysed, based on the idea that the cytoskeleton plays a fundamental role in cellular mechanical responses. For this purpose, the predictions of an open unit-cell model and a 30-element visco-elastic tensegrity model were tested, taking into consideration similar properties of the constitutive F-actin. The quantitative predictions of the time constant and viscosity modulus obtained by both models were compared with previously published experimental data obtained from living cells. The small viscosity modulus values (10(0)-10(3) Pa x s) predicted by the tensegrity model may reflect the combined contributions of the spatially rearranged constitutive filaments and the internal tension to the overall cytoskeleton response to external loading. In contrast, the high viscosity modulus values (10(3)-10(5) Pa x s) predicted by the unit-cell model may rather reflect the mechanical response of the cytoskeleton to the bending of the constitutive filaments and/or to the deformation of internal components. The present results suggest the existence of a close link between the overall visco-elastic response of micromanipulated cells and the underlying architecture.

Mechanical properties of high-temperature superconducting wires. Ph.D. Thesis - Illinois Inst. of Tech.

NASA Technical Reports Server (NTRS)

Goretta, K. C.; Cluff, J. A.; Joo, J.; Lanagan, M. T.; Singh, J. P.; Vasanthamohan, N.; Xin, Y.; Wong, K. W.

1995-01-01

Bending strength, fracture toughness, and elastic modulus data were acquired for YBa2Cu3O(x), Bi2Sr2CaCu2O(x) (Bi,Pb)2Sr2Ca2Cu3O(x), and Tl2Ba2Ca2Cu3O(x) bars. These data and thermal expansion coefficients strongly suggest that the maximum possible tensile strain without fracture of bulk tapes or wires is approximately equals 0.2%. In Ag-clad conductors, residual stresses will be of limited benefit, but fractures produced by larger strains can be accommodated by shunting current through the Ag.

Viscoelastic damping in crystalline composites and alloys

NASA Astrophysics Data System (ADS)

Ranganathan, Raghavan; Ozisik, Rahmi; Keblinski, Pawel

We use molecular dynamics simulations to study viscoelastic behavior of model Lennard-Jones (LJ) crystalline composites subject to an oscillatory shear deformation. The two crystals, namely a soft and a stiff phase, individually show highly elastic behavior and a very small loss modulus. On the other hand, when the stiff phase is included within the soft matrix as a sphere, the composite exhibits significant viscoelastic damping and a large phase shift between stress and strain. In fact, the maximum loss modulus in these model composites was found to be about 20 times greater than that given by the theoretical Hashin-Shtrikman upper bound. We attribute this behavior to the fact that in composites shear strain is highly inhomogeneous and mostly accommodated by the soft phase, corroborated by frequency-dependent Grüneisen parameter analysis. Interestingly, the frequency at which the damping is greatest scales with the microstructural length scale of the composite. Finally, a critical comparison between damping properties of these composites with ordered and disordered alloys and superlattice structures is made.

Speaker box made of composite particle board based on mushroom growing media waste

NASA Astrophysics Data System (ADS)

Tjahjanti, P. H.; Sutarman, Widodo, E.; Kurniawan, A. R.; Winarno, A. T.; Yani, A.

2017-06-01

This research aimed to use mushroom growing media waste (MGMW) that was added by urea, starch and polyvinyl chloride (PVC) glue as a composite particle board to be used as the material of speaker box manufacture. Physical and mechanical testing of particle board including density, moisture content, thickness swelling after immersion in water, strength in water absorption, internal bonding, modulus of elasticity, modulus of rupture and screw holding power, were carried out in accordance with the Stándar Nasional Indonesia (SNI) 03-2105-2006 and Japanese International Standard (JIS) A 5908-2003. The optimum composition of composite particle boards was 60% MGMW + 39% (50% urea +50% starch) + 1% PVC glue. Furthermore, the optimum composition to create speaker box with hardness values of 14.9 Brinnel Hardness Number and results of vibration test obtained amplitude values of the Z-axis, minimum of 0.032007 and maximum of 0.151575. For the acoustic test, results showed good sound absorption coefficients at frequencies of 500 Hz and it has better damping absorption.

The Effect of Pigment Volume Concentration on Film Formation and the Mechanical Properties of Coatings Based on Water-Dispersion Paint and Varnish Materials

NASA Astrophysics Data System (ADS)

Kasyanenko, I. M.; Kramarenko, V. Yu.

2018-01-01

The effect of pigment volume concentration (PVC) on the film formation process and properties of coatings based on the water dispersion of an Acronal 290D styrene-acrylate copolymer and a pigment/filler system used for paint materials in construction was investigated. An analysis of the results obtained is performed within the framework of the concept of the critical PVC. It is shown that the initiation and development of internal stresses occurs the faster, the higher the PVC, but the position of the maximum or the inflection point of the internal stress-drying time curve complies with a universal value of the solid volume content in the compositions. It is found that the internal stresses and Young's modulus of coatings are characterized by an extreme concentration relation that, for the reduced elastic modulus, can be described by a system of equations based on the Halpin-Tsai equation.

Strong and electrically conductive nanopaper from cellulose nanofibers and polypyrrole.

PubMed

Lay, Makara; Méndez, J Alberto; Delgado-Aguilar, Marc; Bun, Kim Ngun; Vilaseca, Fabiola

2016-11-05

In this work, we prepare cellulose nanopapers of high mechanical performance and with the electrical conductivity of a semiconductor. Cellulose nanofibers (CNF) from bleached softwood pulp were coated with polypyrrole (PPy) via in situ chemical polymerization, in presence of iron chloride (III) as oxidant agent. The structure and morphology of nanopapers were studied, as well as their thermal, mechanical and conductive properties. Nanopaper from pure CNF exhibited a very high tensile response (224MPa tensile strength and 14.5GPa elastic modulus). The addition of up to maximum 20% of polypyrrole gave CNF/PPy nanopapers of high flexibility and still good mechanical properties (94MPa strength and 8.8GPa modulus). The electrical conductivity of the resulting CNF/PPy nanopaper was of 5.2 10(-2)Scm(-1), with a specific capacitance of 7.4Fg(-1). The final materials are strong and conductive nanopapers that can find application as biodegradable flexible thin-film transistor (TFT) or as flexible biosensor. Copyright © 2016 Elsevier Ltd. All rights reserved.

Experimental and Numerical Investigation on the Bearing and Failure Mechanism of Multiple Pillars Under Overburden

NASA Astrophysics Data System (ADS)

Zhou, Zilong; Chen, Lu; Zhao, Yuan; Zhao, Tongbin; Cai, Xin; Du, Xueming

2017-04-01

To reveal the mechanical response of a multi-pillar supporting system under external loads, compressive tests were carried out on single-pillar and double-pillar specimens. The digital speckle correlation method and acoustic emission technique were applied to record and analyse information of the deformation and failure processes. Numerical simulations with the software programme PFC2D were also conducted. In the compressive process of the double-pillar system, if both individual pillars have the same mechanical properties, each pillar deforms similarly and reaches the critical stable state almost simultaneously by sharing equal loads. If the two individual pillars have different mechanical properties, the pillar with higher elastic modulus or lower strength would be damaged and lose its bearing capacity firstly. The load would then be transferred to the other pillar under a load redistribution process. When the pillar with higher strength is strong enough, the load carried by the pillar system would increase again. However, the maximum bearing load of the double-pillar system is smaller than the sum of peak load of individual pillars. The study also indicates that the strength, elastic modulus, and load state of pillars all influence the supporting capacity of the pillar system. In underground space engineering, the appropriate choice of pillar dimensions and layout may play a great role in preventing the occurrence of cascading pillar failure.

Mechanical properties of concrete containing a high volume of tire-rubber particles.

PubMed

Khaloo, Ali R; Dehestani, M; Rahmatabadi, P

2008-12-01

Due to the increasingly serious environmental problems presented by waste tires, the feasibility of using elastic and flexible tire-rubber particles as aggregate in concrete is investigated in this study. Tire-rubber particles composed of tire chips, crumb rubber, and a combination of tire chips and crumb rubber, were used to replace mineral aggregates in concrete. These particles were used to replace 12.5%, 25%, 37.5%, and 50% of the total mineral aggregate's volume in concrete. Cylindrical shape concrete specimens 15 cm in diameter and 30 cm in height were fabricated and cured. The fresh rubberized concrete exhibited lower unit weight and acceptable workability compared to plain concrete. The results of a uniaxial compressive strain control test conducted on hardened concrete specimens indicate large reductions in the strength and tangential modulus of elasticity. A significant decrease in the brittle behavior of concrete with increasing rubber content is also demonstrated using nonlinearity indices. The maximum toughness index, indicating the post failure strength of concrete, occurs in concretes with 25% rubber content. Unlike plain concrete, the failure state in rubberized concrete occurs gently and uniformly, and does not cause any separation in the specimen. Crack width and its propagation velocity in rubberized concrete are lower than those of plain concrete. Ultrasonic analysis reveals large reductions in the ultrasonic modulus and high sound absorption for tire-rubber concrete.

TiCN thin films grown by reactive crossed beam pulsed laser deposition

NASA Astrophysics Data System (ADS)

Escobar-Alarcón, L.; Camps, E.; Romero, S.; Muhl, S.; Camps, I.; Haro-Poniatowski, E.

2010-12-01

In this work, we used a crossed plasma configuration where the ablation of two different targets in a reactive atmosphere was performed to prepare nanocrystalline thin films of ternary compounds. In order to assess this alternative deposition configuration, titanium carbonitride (TiCN) thin films were deposited. Two crossed plasmas were produced by simultaneously ablating titanium and graphite targets in an Ar/N2 atmosphere. Films were deposited at room temperature onto Si (100) and AISI 4140 steel substrates whilst keeping the ablation conditions of the Ti target constant. By varying the laser fluence on the carbon target it was possible to study the effect of the carbon plasma on the characteristics of the deposited TiCN films. The structure and composition of the films were analyzed by X-ray Diffraction, Raman Spectroscopy and non-Rutherford Backscattering Spectroscopy. The hardness and elastic modulus of the films was also measured by nanoindentation. In general, the experimental results showed that the TiCN thin films were highly oriented in the (111) crystallographic direction with crystallite sizes as small as 6.0 nm. It was found that the hardness increased as the laser fluence was increased, reaching a maximum value of about 33 GPa and an elastic modulus of 244 GPa. With the proposed configuration, the carbon content could be easily varied from 42 to 5 at.% by changing the laser fluence on the carbon target.

Elastic metamaterials with simultaneously negative effective shear modulus and mass density.

PubMed

Wu, Ying; Lai, Yun; Zhang, Zhao-Qing

2011-09-02

We propose a type of elastic metamaterial comprising fluid-solid composite inclusions which can possess a negative shear modulus and negative mass density over a large frequency region. Such a material has the unique property that only transverse waves can propagate with a negative dispersion while longitudinal waves are forbidden. This leads to many interesting phenomena such as negative refraction, which is demonstrated by using a wedge sample and a significant amount of mode conversion from transverse waves to longitudinal waves that cannot occur on the interface of two natural solids.

Measurement of leaky Lamb wave dispersion curves with application on coating characterization

NASA Astrophysics Data System (ADS)

Lee, Yung-Chun; Cheng, Sheng Wen

2001-04-01

This paper describes a new measurement system for measuring dispersion curves of leaky Lamb waves. The measurement system is based on a focusing PVDF transducer, the defocusing measurement, the V(f,z) waveform processing method, and an image displaying technique. The measurement system is applied for the determination of thin-film elastic properties, namely Young's modulus and shear modulus, by the inversion of dispersion curves measured from a thin-film/plate configuration. Elastic constants of electro-deposited nickel layers are determined with this method.

Holographic Phonons

NASA Astrophysics Data System (ADS)

Alberte, Lasma; Ammon, Martin; Jiménez-Alba, Amadeo; Baggioli, Matteo; Pujolàs, Oriol

2018-04-01

We present a class of holographic massive gravity models that realize a spontaneous breaking of translational symmetry—they exhibit transverse phonon modes whose speed relates to the elastic shear modulus according to elasticity theory. Massive gravity theories thus emerge as versatile and convenient theories to model generic types of translational symmetry breaking: explicit, spontaneous, and a mixture of both. The nature of the breaking is encoded in the radial dependence of the graviton mass. As an application of the model, we compute the temperature dependence of the shear modulus and find that it features a glasslike melting transition.

The elasticity and failure of fluid-filled cellular solids: Theory and experiment

NASA Astrophysics Data System (ADS)

Warner, M.; Thiel, B. L.; Donald, A. M.

2000-02-01

We extend and apply theories of filled foam elasticity and failure to recently available data on foods. The predictions of elastic modulus and failure mode dependence on internal pressure and on wall integrity are borne out by photographic evidence of distortion and failure under compressive loading and under the localized stress applied by a knife blade, and by mechanical data on vegetables differing only in their turgor pressure. We calculate the dry modulus of plate-like cellular solids and the cross over between dry-like and fully fluid-filled elastic response. The bulk elastic properties of limp and aging cellular solids are calculated for model systems and compared with our mechanical data, which also show two regimes of response. The mechanics of an aged, limp beam is calculated, thus offering a practical procedure for comparing experiment and theory. This investigation also thereby offers explanations of the connection between turgor pressure and crispness and limpness of cellular materials.

Does maltose influence on the elasticity of SOPC membrane?

NASA Astrophysics Data System (ADS)

Genova, J.; Zheliaskova, A.; Mitov, M. D.

2010-11-01

Thermally induced shape fluctuations of giant quasi-spherical lipid vesicles are used to study the influence of the disaccharide maltose, dissolved in the aqueous solution, on the curvature elasticity kc of a lipid membrane. The influence of the carbohydrate solute is investigated throughout a considerably wide interval of concentrations. The values of the bending elastic modulus for 200 mM and 400 mM of maltose in the water solution are obtained. The data for kc in presence of maltose is compared with previously obtained results for this constant for the most popular hydrocarbons: monosaccharides glucose and fructose and disaccharides sucrose and trehalose. It is shown that the presence of maltose, dissolved in the aqueous phase surrounding the membrane does not influence on the bending elasticity with the increase of its concentration in the aqueous solution. Up to our knowledge this is the first sugar that does not show decrease of the bending elastic modulus of the lipid membrane, when present in the water surrounding it in concentration up to 400mM.

The elasticity and failure of fluid-filled cellular solids: theory and experiment.

PubMed

Warner, M; Thiel, B L; Donald, A M

2000-02-15

We extend and apply theories of filled foam elasticity and failure to recently available data on foods. The predictions of elastic modulus and failure mode dependence on internal pressure and on wall integrity are borne out by photographic evidence of distortion and failure under compressive loading and under the localized stress applied by a knife blade, and by mechanical data on vegetables differing only in their turgor pressure. We calculate the dry modulus of plate-like cellular solids and the cross over between dry-like and fully fluid-filled elastic response. The bulk elastic properties of limp and aging cellular solids are calculated for model systems and compared with our mechanical data, which also show two regimes of response. The mechanics of an aged, limp beam is calculated, thus offering a practical procedure for comparing experiment and theory. This investigation also thereby offers explanations of the connection between turgor pressure and crispness and limpness of cellular materials.

The elasticity and failure of fluid-filled cellular solids: Theory and experiment

PubMed Central

Warner, M.; Thiel, B. L.; Donald, A. M.

2000-01-01

We extend and apply theories of filled foam elasticity and failure to recently available data on foods. The predictions of elastic modulus and failure mode dependence on internal pressure and on wall integrity are borne out by photographic evidence of distortion and failure under compressive loading and under the localized stress applied by a knife blade, and by mechanical data on vegetables differing only in their turgor pressure. We calculate the dry modulus of plate-like cellular solids and the cross over between dry-like and fully fluid-filled elastic response. The bulk elastic properties of limp and aging cellular solids are calculated for model systems and compared with our mechanical data, which also show two regimes of response. The mechanics of an aged, limp beam is calculated, thus offering a practical procedure for comparing experiment and theory. This investigation also thereby offers explanations of the connection between turgor pressure and crispness and limpness of cellular materials. PMID:10660680

Characterization of phase properties and deformation in ferritic-austenitic duplex stainless steels by nanoindentation and finite element method

DOE PAGES

Schwarm, Samuel C.; Kolli, R. Prakash; Aydogan, Eda; ...

2016-11-03

The phase properties and deformation behavior of the δ–ferrite and γ–austenite phases of CF–3 and CF–8 cast duplex stainless steels were characterized by nanoindentation and microstructure-based finite element method (FEM) models. We evaluated the elastic modulus of each phase and the results indicate that the mean elastic modulus of the δ–ferrite phase is greater than that of the γ–austenite phase, and the mean nanoindentation hardness values of each phase are approximately the same. Furthermore, the elastic FEM model results illustrate that greater von Mises stresses are located within the δ–ferrite phase, while greater von Mises strains are located in themore » γ–austenite phase in response to elastic deformation. The elastic moduli calculated by FEM agree closely with those measured by tensile testing. Finally, the plastically deformed specimens exhibit an increase in misorientation, deformed grains, and subgrain structure formation as measured by electron backscatter diffraction (EBSD).« less

Characterization of phase properties and deformation in ferritic-austenitic duplex stainless steels by nanoindentation and finite element method

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

Schwarm, Samuel C.; Kolli, R. Prakash; Aydogan, Eda

The phase properties and deformation behavior of the δ–ferrite and γ–austenite phases of CF–3 and CF–8 cast duplex stainless steels were characterized by nanoindentation and microstructure-based finite element method (FEM) models. We evaluated the elastic modulus of each phase and the results indicate that the mean elastic modulus of the δ–ferrite phase is greater than that of the γ–austenite phase, and the mean nanoindentation hardness values of each phase are approximately the same. Furthermore, the elastic FEM model results illustrate that greater von Mises stresses are located within the δ–ferrite phase, while greater von Mises strains are located in themore » γ–austenite phase in response to elastic deformation. The elastic moduli calculated by FEM agree closely with those measured by tensile testing. Finally, the plastically deformed specimens exhibit an increase in misorientation, deformed grains, and subgrain structure formation as measured by electron backscatter diffraction (EBSD).« less

Effective properties of a fly ash geopolymer: Synergistic application of X-ray synchrotron tomography, nanoindentation, and homogenization models

DOE PAGES

Das, Sumanta; Yang, Pu; Singh, Sudhanshu S.; ...

2015-09-02

Microstructural and micromechanical investigation of a fly ash-based geopolymer using: (i) synchrotron x-ray tomography (XRT) to determine the volume fraction and tortuosity of pores that are influential in fluid transport, (ii) mercury intrusion porosimetry (MIP) to capture the volume fraction of smaller pores, (iii) scanning electron microscopy (SEM) combined with multi-label thresholding to identify and characterize the solid phases in the microstructure, and (iv) nanoindentation to determine the component phase elastic properties using statistical deconvolution, is reported in this paper. The phase volume fractions and elastic properties are used in multi-step mean field homogenization (Mori- Tanaka and double inclusion) modelsmore » to determine the homogenized macroscale elastic modulus of the composite. The homogenized elastic moduli are in good agreement with the flexural elastic modulus determined on macroscale paste beams. As a result, the combined use of microstructural and micromechanical characterization tools at multiple scales provides valuable information towards the material design of fly ash geopolymers.« less

Statistical models for the distribution of modulus of elasticity and modulus of rupture in lumber with implications for reliability calculations

Treesearch

Steve P. Verrill; Frank C. Owens; David E. Kretschmann; Rubin Shmulsky

2017-01-01

It is common practice to assume that a two-parameter Weibull probability distribution is suitable for modeling lumber properties. Verrill and co-workers demonstrated theoretically and empirically that the modulus of rupture (MOR) distribution of visually graded or machine stress rated (MSR) lumber is not distributed as a Weibull. Instead, the tails of the MOR...

Elastic and mechanical softening in boron-doped diamond

PubMed Central

Liu, Xiaobing; Chang, Yun-Yuan; Tkachev, Sergey N.; Bina, Craig R.; Jacobsen, Steven D.

2017-01-01

Alternative approaches to evaluating the hardness and elastic properties of materials exhibiting physical properties comparable to pure diamond have recently become necessary. The classic linear relationship between shear modulus (G) and Vickers hardness (HV), along with more recent non-linear formulations based on Pugh’s modulus extending into the superhard region (HV > 40 GPa) have guided synthesis and identification of novel superabrasives. These schemes rely on accurately quantifying HV of diamond-like materials approaching or potentially exceeding the hardness of the diamond indenter, leading to debate about methodology and the very definition of hardness. Elasticity measurements on such materials are equally challenging. Here we used a high-precision, GHz-ultrasonic interferometer in conjunction with a newly developed optical contact micrometer and 3D optical microscopy of indentations to evaluate elasticity-hardness relations in the ultrahard range (HV > 80 GPa) by examining single-crystal boron-doped diamond (BDD) with boron contents ranging from 50–3000 ppm. We observe a drastic elastic-mechanical softening in highly doped BDD relative to the trends observed for superhard materials, providing insight into elasticity-hardness relations for ultrahard materials. PMID:28233808

Elastic and mechanical softening in boron-doped diamond

NASA Astrophysics Data System (ADS)

Liu, Xiaobing; Chang, Yun-Yuan; Tkachev, Sergey N.; Bina, Craig R.; Jacobsen, Steven D.

2017-02-01

Alternative approaches to evaluating the hardness and elastic properties of materials exhibiting physical properties comparable to pure diamond have recently become necessary. The classic linear relationship between shear modulus (G) and Vickers hardness (HV), along with more recent non-linear formulations based on Pugh’s modulus extending into the superhard region (HV > 40 GPa) have guided synthesis and identification of novel superabrasives. These schemes rely on accurately quantifying HV of diamond-like materials approaching or potentially exceeding the hardness of the diamond indenter, leading to debate about methodology and the very definition of hardness. Elasticity measurements on such materials are equally challenging. Here we used a high-precision, GHz-ultrasonic interferometer in conjunction with a newly developed optical contact micrometer and 3D optical microscopy of indentations to evaluate elasticity-hardness relations in the ultrahard range (HV > 80 GPa) by examining single-crystal boron-doped diamond (BDD) with boron contents ranging from 50-3000 ppm. We observe a drastic elastic-mechanical softening in highly doped BDD relative to the trends observed for superhard materials, providing insight into elasticity-hardness relations for ultrahard materials.

Cone penetrometer equipped with piezoelectric sensors for measurement of soil stiffness in highway pavement.

DOT National Transportation Integrated Search

2005-11-01

The stiffness (elastic modulus and shear modulus) and Poisson's ratio of the base and sublayers are important parameters in the design and quality assurance during construction of highway pavements. The new highway construction guide proposed by AASH...

The power law and dynamic rheology in cheese analysis

USDA-ARS?s Scientific Manuscript database

The protein networks of food such as cheese are investigated nondestructively by small amplitude oscillatory shear analysis, which provides information on elastic modulus and viscous modulus. Relationships between frequency and viscoelastic data may be obtained from frequency sweeps by applying the...

Feasibility of a transient elastography technique for in vitro arterial elasticity assessment.

PubMed

Brum, J; Balay, G; Bia, D; Armentano, R L; Negreira, C

2010-01-01

The early detection of biomechanical modifications in the arterial wall could be used as a predictor factor for various diseases, for example hypertension or atherosclerosis. In this work a transient elastography technique is used for the in vitro evaluation of the arterial wall elasticity. The obtained Young modulus is compared with the one obtained by a more classical approach: pressure-diameter relationships. As a sample an arterial phantom made of PolyVinyl Alcohol (PVA) gel was used. Diameter variation due to pressure variation inside the phantom was recorded by means of ultrasound. Through both techniques similar Young modulus estimations are obtained showing in this way the feasibility of applying transient elastography for the arterial wall elasticity assessment.

Studying Petrophysical and Geomechanical Properties of Utica Point-Pleasant Shale and its Variations Across the Northern Appalachian Basin

NASA Astrophysics Data System (ADS)

Raziperchikolaee, S.; Kelley, M. E.; Burchwell, A.

2017-12-01

Understanding petrophysical and geomechanical parameters of shale formations and their variations across the basin are necessary to optimize the design of a hydraulic fracturing program aimed at enhancing long term oil/gas production from unconventional wells. Dipole sonic logging data (compressional-wave and shear-wave slowness) from multiple wells across the study area, coupled with formation bulk density log data, were used to calculate dynamic elastic parameters, including shear modulus, bulk modulus, Poisson's ratio, and Young's modulus for the shale formations. The individual-well data were aggregated into a single histogram for each parameter to gain an understanding of the variation in the properties (including brittleness) of the Utica Point-Pleasant formations across the entire study area. A crossplot of the compressional velocity and bulk density and a crossplot between the compressional velocity, the shear velocity, and depth of the measurement were used for a high level petrophysical characterization of the Utica Point-Pleasant. Detailed interpretation of drilling induced fractures recorded in image logs, and an analysis of shear wave anisotropy using multi-receiver sonic logs were also performed. Orientation of drilling induced fractures was measured to determine the maximum horizontal stress azimuth. Also, an analysis of shear wave anisotropy to predict stress anisotropy around the wellbore was performed to determine the direction of maximum horizontal stress. Our study shows how the detailed interpretation of borehole breakouts, drilling induced fractures, and sonic wave data can be used to reduce uncertainty and produce a better hydraulic fracturing design in the Utica Point Pleasant formations across the northern Appalachian Basin region of Ohio.

Nanotribological performance of fullerene-like carbon nitride films

NASA Astrophysics Data System (ADS)

Flores-Ruiz, Francisco Javier; Enriquez-Flores, Christian Ivan; Chiñas-Castillo, Fernando; Espinoza-Beltrán, Francisco Javier

2014-09-01

Fullerene-like carbon nitride films exhibit high elastic modulus and low friction coefficient. In this study, thin CNx films were deposited on silicon substrate by DC magnetron sputtering and the tribological behavior at nanoscale was evaluated using an atomic force microscope. Results show that CNx films with fullerene-like structure have a friction coefficient (CoF ∼ 0.009-0.022) that is lower than amorphous CNx films (CoF ∼ 0.028-0.032). Analysis of specimens characterized by X-ray photoelectron spectroscopy shows that films with fullerene-like structure have a higher number of sp3 CN bonds and exhibit the best mechanical properties with high values of elastic modulus (E > 180 GPa) and hardness (H > 20 GPa). The elastic recovery determined on specimens with a fullerene-like CNx structure was of 95% while specimens of amorphous CNx structure had only 75% elastic recovery.

Determination of Elastic Moduli of Fiber-Resin Composites Using an Impulse Excitation Technique

NASA Technical Reports Server (NTRS)

Viens, Michael J.; Johnson, Jeffrey J.

1996-01-01

The elastic moduli of graphite/epoxy and graphite/cyanate ester composite specimens with various laminate lay-ups was determined using an impulse excitation/acoustic resonance technique and compared to those determined using traditional strain gauge and extensometer techniques. The stiffness results were also compared to those predicted from laminate theory using uniaxial properties. The specimen stiffnesses interrogated ranged from 12 to 30 Msi. The impulse excitation technique was found to be a relatively quick and accurate method for determining elastic moduli with minimal specimen preparation and no requirement for mechanical loading frames. The results of this investigation showed good correlation between the elastic modulus determined using the impulse excitation technique, strain gauge and extensometer techniques, and modulus predicted from laminate theory. The flexural stiffness determined using the impulse excitation was in good agreement with that predicted from laminate theory. The impulse excitation/acoustic resonance interrogation technique has potential as a quality control test.

Atomic force microscopy studies on cellular elastic and viscoelastic properties.

PubMed

Li, Mi; Liu, Lianqing; Xi, Ning; Wang, Yuechao

2018-01-01

In this work, a method based on atomic force microscopy (AFM) approach-reside-retract experiments was established to simultaneously quantify the elastic and viscoelastic properties of single cells. First, the elastic and viscoelastic properties of normal breast cells and cancerous breast cells were measured, showing significant differences in Young's modulus and relaxation times between normal and cancerous breast cells. Remarkable differences in cellular topography between normal and cancerous breast cells were also revealed by AFM imaging. Next, the elastic and viscoelasitc properties of three other types of cell lines and primary normal B lymphocytes were measured; results demonstrated the potential of cellular viscoelastic properties in complementing cellular Young's modulus for discerning different states of cells. This research provides a novel way to quantify the mechanical properties of cells by AFM, which allows investigation of the biomechanical behaviors of single cells from multiple aspects.

Fluid Effects on Shear for Seismic Waves in Finely Layered Porous Media

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

Berryman, J G

Although there are five effective shear moduli for any layered VTI medium, one and only one effective shear modulus of the layered system (namely the uniaxial shear) contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves. Pore fluids can increase the magnitude the shear energy stored in this modulus by an amount that ranges from the smallest to the largest effective shear moduli of the VTI system. But, since there are five shear moduli in play, the overall increase in shear energy due to fluids is reducedmore » by a factor of about 5 in general. We can therefore give definite bounds on the maximum increase of overall shear modulus, being about 20% of the allowed range as liquid is fully substituted for gas. An attendant increase of density (depending on porosity and fluid density) by approximately 5 to 10% decreases the shear wave speed and, thereby, partially offsets the effect of this shear modulus increase. The final result is an increase of shear wave speed on the order of 5 to 10%. This increase is shown to be possible under most favorable circumstances - i.e. when the shear modulus fluctuations are large (resulting in strong anisotropy) and the medium behaves in an undrained fashion due to fluid trapping. At frequencies higher than seismic (such as sonic and ultrasonic waves for well-logging or laboratory experiments), resulting short response times also produce the requisite undrained behavior and, therefore, fluids also affect shear waves at high frequencies by increasing rigidity.« less

Prediction of local proximal tibial subchondral bone structural stiffness using subject-specific finite element modeling: Effect of selected density-modulus relationship.

PubMed

Nazemi, S Majid; Amini, Morteza; Kontulainen, Saija A; Milner, Jaques S; Holdsworth, David W; Masri, Bassam A; Wilson, David R; Johnston, James D

2015-08-01

Quantitative computed tomography based subject-specific finite element modeling has potential to clarify the role of subchondral bone alterations in knee osteoarthritis initiation, progression, and pain initiation. Calculation of bone elastic moduli from image data is a basic step when constructing finite element models. However, different relationships between elastic moduli and imaged density (known as density-modulus relationships) have been reported in the literature. The objective of this study was to apply seven different trabecular-specific and two cortical-specific density-modulus relationships from the literature to finite element models of proximal tibia subchondral bone, and identify the relationship(s) that best predicted experimentally measured local subchondral structural stiffness with highest explained variance and least error. Thirteen proximal tibial compartments were imaged via quantitative computed tomography. Imaged bone mineral density was converted to elastic moduli using published density-modulus relationships and mapped to corresponding finite element models. Proximal tibial structural stiffness values were compared to experimentally measured stiffness values from in-situ macro-indentation testing directly on the subchondral bone surface (47 indentation points). Regression lines between experimentally measured and finite element calculated stiffness had R(2) values ranging from 0.56 to 0.77. Normalized root mean squared error varied from 16.6% to 337.6%. Of the 21 evaluated density-modulus relationships in this study, Goulet combined with Snyder and Schneider or Rho appeared most appropriate for finite element modeling of local subchondral bone structural stiffness. Though, further studies are needed to optimize density-modulus relationships and improve finite element estimates of local subchondral bone structural stiffness. Copyright © 2015 Elsevier Ltd. All rights reserved.

The young's modulus of 1018 steel and 67061-T6 aluminum measured from quasi-static to elastic precursor strain-rates

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

Rae, Philip J; Trujillo, Carl; Lovato, Manuel

2009-01-01

The assumption that Young's modulus is strain-rate invariant is tested for 6061-T6 aluminium alloy and 1018 steel over 10 decades of strain-rate. For the same billets of material, 3 quasi-static strain-rates are investigated with foil strain gauges at room temperature. The ultrasonic sound speeds are measured and used to calculate the moduli at approximately 10{sup 4} s{sup -1}. Finally, ID plate impact is used to generate an elastic pre-cursor in the alloys at a strain-rate of approximately 10{sup 6} s{sup -1} from which the longitudinal sound speed may be obtained. It is found that indeed the Young's modulus is strain-ratemore » independent within the experimental accuracy.« less

Using mechanobiological mimicry of red blood cells to extend circulation times of hydrogel microparticles

PubMed Central

Merkel, Timothy J.; Jones, Stephen W.; Herlihy, Kevin P.; Kersey, Farrell R.; Shields, Adam R.; Napier, Mary; Luft, J. Christopher; Wu, Huali; Zamboni, William C.; Wang, Andrew Z.; Bear, James E.; DeSimone, Joseph M.

2011-01-01

It has long been hypothesized that elastic modulus governs the biodistribution and circulation times of particles and cells in blood; however, this notion has never been rigorously tested. We synthesized hydrogel microparticles with tunable elasticity in the physiological range, which resemble red blood cells in size and shape, and tested their behavior in vivo. Decreasing the modulus of these particles altered their biodistribution properties, allowing them to bypass several organs, such as the lung, that entrapped their more rigid counterparts, resulting in increasingly longer circulation times well past those of conventional microparticles. An 8-fold decrease in hydrogel modulus correlated to a greater than 30-fold increase in the elimination phase half-life for these particles. These results demonstrate a critical design parameter for hydrogel microparticles. PMID:21220299

Evaluation of copper, aluminum, and nickel interatomic potentials on predicting the elastic properties

NASA Astrophysics Data System (ADS)

Rassoulinejad-Mousavi, Seyed Moein; Mao, Yijin; Zhang, Yuwen

2016-06-01

Choice of appropriate force field is one of the main concerns of any atomistic simulation that needs to be seriously considered in order to yield reliable results. Since investigations on the mechanical behavior of materials at micro/nanoscale have been becoming much more widespread, it is necessary to determine an adequate potential which accurately models the interaction of the atoms for desired applications. In this framework, reliability of multiple embedded atom method based interatomic potentials for predicting the elastic properties was investigated. Assessments were carried out for different copper, aluminum, and nickel interatomic potentials at room temperature which is considered as the most applicable case. Examined force fields for the three species were taken from online repositories of National Institute of Standards and Technology, as well as the Sandia National Laboratories, the LAMMPS database. Using molecular dynamic simulations, the three independent elastic constants, C11, C12, and C44, were found for Cu, Al, and Ni cubic single crystals. Voigt-Reuss-Hill approximation was then implemented to convert elastic constants of the single crystals into isotropic polycrystalline elastic moduli including bulk modulus, shear modulus, and Young's modulus as well as Poisson's ratio. Simulation results from massive molecular dynamic were compared with available experimental data in the literature to justify the robustness of each potential for each species. Eventually, accurate interatomic potentials have been recommended for finding each of the elastic properties of the pure species. Exactitude of the elastic properties was found to be sensitive to the choice of the force fields. Those potentials that were fitted for a specific compound may not necessarily work accurately for all the existing pure species. Tabulated results in this paper might be used as a benchmark to increase assurance of using the interatomic potential that was designated for a problem.

One-Dimensional and Two-Dimensional Analytical Solutions for Functionally Graded Beams with Different Moduli in Tension and Compression

PubMed Central

Li, Xue; Dong, Jiao

2018-01-01

The material considered in this study not only has a functionally graded characteristic but also exhibits different tensile and compressive moduli of elasticity. One-dimensional and two-dimensional mechanical models for a functionally graded beam with a bimodular effect were established first. By taking the grade function as an exponential expression, the analytical solutions of a bimodular functionally graded beam under pure bending and lateral-force bending were obtained. The regression from a two-dimensional solution to a one-dimensional solution is verified. The physical quantities in a bimodular functionally graded beam are compared with their counterparts in a classical problem and a functionally graded beam without a bimodular effect. The validity of the plane section assumption under pure bending and lateral-force bending is analyzed. Three typical cases that the tensile modulus is greater than, equal to, or less than the compressive modulus are discussed. The result indicates that due to the introduction of the bimodular functionally graded effect of the materials, the maximum tensile and compressive bending stresses may not take place at the bottom and top of the beam. The real location at which the maximum bending stress takes place is determined via the extreme condition for the analytical solution. PMID:29772835

Indentation quantification for in-liquid nanomechanical measurement of soft material using an atomic force microscope: rate-dependent elastic modulus of live cells.

PubMed

Ren, Juan; Yu, Shiyan; Gao, Nan; Zou, Qingze

2013-11-01

In this paper, a control-based approach to replace the conventional method to achieve accurate indentation quantification is proposed for nanomechanical measurement of live cells using atomic force microscope. Accurate indentation quantification is central to probe-based nanomechanical property measurement. The conventional method for in-liquid nanomechanical measurement of live cells, however, fails to accurately quantify the indentation as effects of the relative probe acceleration and the hydrodynamic force are not addressed. As a result, significant errors and uncertainties are induced in the nanomechanical properties measured. In this paper, a control-based approach is proposed to account for these adverse effects by tracking the same excitation force profile on both a live cell and a hard reference sample through the use of an advanced control technique, and by quantifying the indentation from the difference of the cantilever base displacement in these two measurements. The proposed control-based approach not only eliminates the relative probe acceleration effect with no need to calibrate the parameters involved, but it also reduces the hydrodynamic force effect significantly when the force load rate becomes high. We further hypothesize that, by using the proposed control-based approach, the rate-dependent elastic modulus of live human epithelial cells under different stress conditions can be reliably quantified to predict the elasticity evolution of cell membranes, and hence can be used to predict cellular behaviors. By implementing the proposed approach, the elastic modulus of HeLa cells before and after the stress process were quantified as the force load rate was changed over three orders of magnitude from 0.1 to 100 Hz, where the amplitude of the applied force and the indentation were at 0.4-2 nN and 250-450 nm, respectively. The measured elastic modulus of HeLa cells showed a clear power-law dependence on the load rate, both before and after the stress process. Moreover, the elastic modulus of HeLa cells was substantially reduced by two to five times due to the stress process. Thus, our measurements demonstrate that the control-based protocol is effective in quantifying and characterizing the evolution of nanomechanical properties during the stress process of live cells.

New methodology for mechanical characterization of human superficial facial tissue anisotropic behaviour in vivo.

PubMed

Then, C; Stassen, B; Depta, K; Silber, G

2017-07-01

Mechanical characterization of human superficial facial tissue has important applications in biomedical science, computer assisted forensics, graphics, and consumer goods development. Specifically, the latter may include facial hair removal devices. Predictive accuracy of numerical models and their ability to elucidate biomechanically relevant questions depends on the acquisition of experimental data and mechanical tissue behavior representation. Anisotropic viscoelastic behavioral characterization of human facial tissue, deformed in vivo with finite strain, however, is sparse. Employing an experimental-numerical approach, a procedure is presented to evaluate multidirectional tensile properties of superficial tissue layers of the face in vivo. Specifically, in addition to stress relaxation, displacement-controlled multi-step ramp-and-hold protocols were performed to separate elastic from inelastic properties. For numerical representation, an anisotropic hyperelastic material model in conjunction with a time domain linear viscoelasticity formulation with Prony series was employed. Model parameters were inversely derived, employing finite element models, using multi-criteria optimization. The methodology provides insight into mechanical superficial facial tissue properties. Experimental data shows pronounced anisotropy, especially with large strain. The stress relaxation rate does not depend on the loading direction, but is strain-dependent. Preconditioning eliminates equilibrium hysteresis effects and leads to stress-strain repeatability. In the preconditioned state tissue stiffness and hysteresis insensitivity to strain rate in the applied range is evident. The employed material model fits the nonlinear anisotropic elastic results and the viscoelasticity model reasonably reproduces time-dependent results. Inversely deduced maximum anisotropic long-term shear modulus of linear elasticity is G ∞,max aniso =2.43kPa and instantaneous initial shear modulus at an applied rate of ramp loading is G 0,max aniso =15.38kPa. Derived mechanical model parameters constitute a basis for complex skin interaction simulation. Copyright © 2017. Published by Elsevier Ltd.

An Experimental Study to Measure the Mechanical Properties of the Human Liver.

PubMed

Karimi, Alireza; Shojaei, Ahmad

2018-01-01

Since the liver is one of the most important organs of the body that can be injured during trauma, that is, during accidents like car crashes, understanding its mechanical properties is of great interest. Experimental data is needed to address the mechanical properties of the liver to be used for a variety of applications, such as the numerical simulations for medical purposes, including the virtual reality simulators, trauma research, diagnosis objectives, as well as injury biomechanics. However, the data on the mechanical properties of the liver capsule is limited to the animal models or confined to the tensile/compressive loading under single direction. Therefore, this study was aimed at experimentally measuring the axial and transversal mechanical properties of the human liver capsule under both the tensile and compressive loadings. To do that, 20 human cadavers were autopsied and their liver capsules were excised and histologically analyzed to extract the mean angle of a large fibers population (bundle of the fine collagen fibers). Thereafter, the samples were cut and subjected to a series of axial and transversal tensile/compressive loadings. The results revealed the tensile elastic modulus of 12.16 ± 1.20 (mean ± SD) and 7.17 ± 0.85 kPa under the axial and transversal loadings respectively. Correspondingly, the compressive elastic modulus of 196.54 ± 13.15 and 112.41 ± 8.98 kPa were observed under the axial and transversal loadings respectively. The compressive axial and transversal maximum/failure stress of the capsule were 32.54 and 37.30 times higher than that of the tensile ones respectively. The capsule showed a stiffer behavior under the compressive load compared to the tensile one. In addition, the axial elastic modulus of the capsule was found to be higher than that of the transversal one. The findings of the current study have implications not only for understanding the mechanical properties of the human capsule tissue under tensile/compressive loading, but also for providing unprocessed data for both the doctors and engineers to be used for diagnosis and simulation purposes. © 2017 S. Karger AG, Basel.

Broad Anatomical Variation within a Narrow Wood Density Range—A Study of Twig Wood across 69 Australian Angiosperms

PubMed Central

Ziemińska, Kasia; Westoby, Mark; Wright, Ian J.

2015-01-01

Objectives Just as people with the same weight can have different body builds, woods with the same wood density can have different anatomies. Here, our aim was to assess the magnitude of anatomical variation within a restricted range of wood density and explore its potential ecological implications. Methods Twig wood of 69 angiosperm tree and shrub species was analyzed. Species were selected so that wood density varied within a relatively narrow range (0.38–0.62 g cm-3). Anatomical traits quantified included wood tissue fractions (fibres, axial parenchyma, ray parenchyma, vessels, and conduits with maximum lumen diameter below 15 μm), vessel properties, and pith area. To search for potential ecological correlates of anatomical variation the species were sampled across rainfall and temperature contrasts, and several other ecologically-relevant traits were measured (plant height, leaf area to sapwood area ratio, and modulus of elasticity). Results Despite the limited range in wood density, substantial anatomical variation was observed. Total parenchyma fraction varied from 0.12 to 0.66 and fibre fraction from 0.20 to 0.74, and these two traits were strongly inversely correlated (r = -0.86, P < 0.001). Parenchyma was weakly (0.24 ≤|r|≤ 0.35, P < 0.05) or not associated with vessel properties nor with height, leaf area to sapwood area ratio, and modulus of elasticity (0.24 ≤|r|≤ 0.41, P < 0.05). However, vessel traits were fairly well correlated with height and leaf area to sapwood area ratio (0.47 ≤|r|≤ 0.65, all P < 0.001). Modulus of elasticity was mainly driven by fibre wall plus vessel wall fraction rather than by the parenchyma component. Conclusions Overall, there seem to be at least three axes of variation in xylem, substantially independent of each other: a wood density spectrum, a fibre-parenchyma spectrum, and a vessel area spectrum. The fibre-parenchyma spectrum does not yet have any clear or convincing ecological interpretation. PMID:25906320

[Evaluation of bone structure and quality of ovariectomized rats by microcrack].

PubMed

Dai, Ru-chun; Liao, Er-yuan; Yang, Chuan

2003-12-01

To compare microcrack with bone mineral desity (BMD), bone histomorphometry and biomechanics parameters, and to investigate the potential of microcrack in the evaluation of bone biomechanical quality. Eight 10-month-old Sprague-Dawley rats were served as baseline controls, and 90 10-month-old rats were randomly divided into A, B, and C groups. Each group comprised ovariectomized (OVX), 17 beta-estradiol treated [EST, 10 micro/(kg x d)] and sham-operated (SHAM) subgroups. Rats from groups A,B and C were killed at the 3rd, 15th and 21st week post-operatively. Total body and lumbar vertebral BMD were measured before being killed, and BMD of isolated lumbar vertebrae and tibiae were measured after killing. Bone histomorphometry of the proximal end of isolated right tibia was performed,and compression test was carried out on the isolated 5th lumbar vertebra (L5). After fatigue damage, the isolated 4th lumbar vertebra was stained by en bloc basic fuchsin staining, and microcrack density (Cr. Dn) and microcrack surface density (Cr. SDn) were de- termined on the bone tissue sections. Bone parameters in each subgroup of rats were observed at different time. (1) At the 15th and 21st week post-operatively, multi-part BMD, Cr. Dn and Cr. SDn were higher than those at the 3rd week. (2) At the 15th week, trabecular separation (Tb. Sp) increased, trabecular number (Tb. N) decreased, and the maximum loading level and elastic modulus of vertebra reached the peak. (3) At the 3rd week, Tb. Sp, Cr. Dn and Cr. SDn in the OVX subgroup were greater than those in the EST subgroup, while the percentage of trabecular area (TbTr) in the OVX subgroup was lower than that of the EST and SHAM subgroups. No changes of BMDs and biomechanic parameters were observed among the three subgroups. (4) At the 15th week, multi-part BMD and maximum loading level in the OVX and EST subgroups were lower than those in the SHAM subgroup, while elastic modulus, bone histomorphometry parameters, Cr. Dn and Cr. SDn had no change among the three subgroups. (5) At the 21st week, multi-part BMDs, Tb. N and TbTr in the OVX subgroup were smaller than those in the EST and SHAM subgroups. Tb. Sp, bone formation rate, mineral apposition rate, percent labeled perimeter,Cr. Dn and Cr. SDn in the OVX subgroups were greater than those in the EST and SHAM subgroups. Maximum loading level and elastic modulus of vertebra in EST and OVX subgroups were lower than those in the SHAM subgroup. There were no significant differences in all of these parameters Microcrack can be regarded as an alterative between the EST and the SHAM subgroup. Conclusion parameter in the evaluation of bone biomechanical quality.

Determination of elastic modulus and residual stress of plasma-sprayed tungsten coating on steel substrate

NASA Astrophysics Data System (ADS)

You, J. H.; Höschen, T.; Lindig, S.

2006-01-01

Plasma-sprayed tungsten, which is a candidate material for the first wall armour, shows a porous, heterogeneous microstructure. Due to its characteristic morphology, the properties are significantly different from those of its dense bulk material. Measurements of the elastic modulus of this coating have not been reported in the literature. In this work Young's modulus of highly porous plasma-sprayed tungsten coatings deposited on steel (F82H) substrates was measured. For the fabrication of the coating system the vacuum plasma-spray process was applied. Measurements were performed by means of three-point and four-point bending tests. The obtained modulus values ranged from 53 to 57 GPa. These values could be confirmed by the test result of a detached coating strip, which was 54 GPa. The applied methods produced consistent results regardless of testing configurations and specimen sizes. The errors were less than 1%. Residual stress of the coating was also estimated.

Elastic collapse in disordered isostatic networks

NASA Astrophysics Data System (ADS)

Moukarzel, C. F.

2012-02-01

Isostatic networks are minimally rigid and therefore have, generically, nonzero elastic moduli. Regular isostatic networks have finite moduli in the limit of large sizes. However, numerical simulations show that all elastic moduli of geometrically disordered isostatic networks go to zero with system size. This holds true for positional as well as for topological disorder. In most cases, elastic moduli decrease as inverse power laws of system size. On directed isostatic networks, however, of which the square and cubic lattices are particular cases, the decrease of the moduli is exponential with size. For these, the observed elastic weakening can be quantitatively described in terms of the multiplicative growth of stresses with system size, giving rise to bulk and shear moduli of order e-bL. The case of sphere packings, which only accept compressive contact forces, is considered separately. It is argued that these have a finite bulk modulus because of specific correlations in contact disorder, introduced by the constraint of compressivity. We discuss why their shear modulus, nevertheless, is again zero for large sizes. A quantitative model is proposed that describes the numerically measured shear modulus, both as a function of the loading angle and system size. In all cases, if a density p>0 of overconstraints is present, as when a packing is deformed by compression or when a glass is outside its isostatic composition window, all asymptotic moduli become finite. For square networks with periodic boundary conditions, these are of order \\sqrt{p} . For directed networks, elastic moduli are of order e-c/p, indicating the existence of an "isostatic length scale" of order 1/p.

Macroscopic elastic properties of textured ZrN-AlN polycrystalline aggregates: From ab initio calculations to grain-scale interactions

NASA Astrophysics Data System (ADS)

Holec, D.; Tasnádi, F.; Wagner, P.; Friák, M.; Neugebauer, J.; Mayrhofer, P. H.; Keckes, J.

2014-11-01

Despite the fast development of computational material modeling, the theoretical description of macroscopic elastic properties of textured polycrystalline aggregates starting from basic principles remains a challenging task. In this study we use a supercell-based approach to obtain the elastic properties of a random solid solution cubic Zr1 -xAlxN system as a function of the metallic sublattice composition and texture descriptors. The employed special quasirandom structures are optimized not only with respect to short-range-order parameters, but also to make the three cubic directions [1 0 0 ] , [0 1 0 ] , and [0 0 1 ] as similar as possible. In this way, only a small spread of elastic constant tensor components is achieved and an optimum trade-off between modeling of chemical disorder and computational limits regarding the supercell size and calculational time is proposed. The single-crystal elastic constants are shown to vary smoothly with composition, yielding x ≈0.5 an alloy constitution with an almost isotropic response. Consequently, polycrystals with this composition are suggested to have Young's modulus independent of the actual microstructure. This is indeed confirmed by explicit calculations of polycrystal elastic properties, both within the isotropic aggregate limit and with fiber textures with various orientations and sharpness. It turns out that for low AlN mole fractions, the spread of the possible Young's modulus data caused by the texture variation can be larger than 100 GPa. Consequently, our discussion of Young's modulus data of cubic Zr1 -xAlxN contains also the evaluation of the texture typical for thin films.

Effect of pore geometry on the compressibility of a confined simple fluid

NASA Astrophysics Data System (ADS)

Dobrzanski, Christopher D.; Maximov, Max A.; Gor, Gennady Y.

2018-02-01

Fluids confined in nanopores exhibit properties different from the properties of the same fluids in bulk; among these properties is the isothermal compressibility or elastic modulus. The modulus of a fluid in nanopores can be extracted from ultrasonic experiments or calculated from molecular simulations. Using Monte Carlo simulations in the grand canonical ensemble, we calculated the modulus for liquid argon at its normal boiling point (87.3 K) adsorbed in model silica pores of two different morphologies and various sizes. For spherical pores, for all the pore sizes (diameters) exceeding 2 nm, we obtained a logarithmic dependence of fluid modulus on the vapor pressure. Calculation of the modulus at saturation showed that the modulus of the fluid in spherical pores is a linear function of the reciprocal pore size. The calculation of the modulus of the fluid in cylindrical pores appeared too scattered to make quantitative conclusions. We performed additional simulations at higher temperature (119.6 K), at which Monte Carlo insertions and removals become more efficient. The results of the simulations at higher temperature confirmed both regularities for cylindrical pores and showed quantitative difference between the fluid moduli in pores of different geometries. Both of the observed regularities for the modulus stem from the Tait-Murnaghan equation applied to the confined fluid. Our results, along with the development of the effective medium theories for nanoporous media, set the groundwork for analysis of the experimentally measured elastic properties of fluid-saturated nanoporous materials.

The influence of electric charge transferred during electro-mechanical reshaping on mechanical behavior of cartilage

NASA Astrophysics Data System (ADS)

Protsenko, Dimitry E.; Lim, Amanda; Wu, Edward C.; Manuel, Cyrus; Wong, Brian J. F.

2011-03-01

Electromechanical reshaping (EMR) of cartilage has been suggested as an alternative to the classical surgical techniques of modifying the shape of facial cartilages. The method is based on exposure of mechanically deformed cartilaginous tissue to a low level electric field. Electro-chemical reactions within the tissue lead to reduction of internal stress, and establishment of a new equilibrium shape. The same reactions offset the electric charge balance between collagen and proteoglycan matrix and interstitial fluid responsible for maintenance of cartilage mechanical properties. The objective of this study was to investigate correlation between the electric charge transferred during EMR and equilibrium elastic modulus. We used a finite element model based on the triphasic theory of cartilage mechanical properties to study how electric charges transferred in the electro-chemical reactions in cartilage can change its mechanical responses to step displacements in unconfined compression. The concentrations of the ions, the strain field and the fluid and ion velocities within the specimen subject to an applied mechanical deformation were estimated and apparent elastic modulus (the ratio of the equilibrium axial stress to the axial strain) was calculated as a function of transferred charge. The results from numerical calculations showed that the apparent elastic modulus decreases with increase in electric charge transfer. To compare numerical model with experimental observation we measured elastic modulus of cartilage as a function of electric charge transferred in electric circuit during EMR. Good correlation between experimental and theoretical data suggests that electric charge disbalance is responsible for alteration of cartilage mechanical properties.

Hardrock Elastic Physical Properties: Birch's Seismic Parameter Revisited

NASA Astrophysics Data System (ADS)

Wu, M.; Milkereit, B.

2014-12-01

Identifying rock composition and properties is imperative in a variety of fields including geotechnical engineering, mining, and petroleum exploration, in order to accurately make any petrophysical calculations. Density is, in particular, an important parameter that allows us to differentiate between lithologies and estimate or calculate other petrophysical properties. It is well established that compressional and shear wave velocities of common crystalline rocks increase with increasing densities (i.e. the Birch and Nafe-Drake relationships). Conventional empirical relations do not take into account S-wave velocity. Physical properties of Fe-oxides and massive sulfides, however, differ significantly from the empirical velocity-density relationships. Currently, acquiring in-situ density data is challenging and problematic, and therefore, developing an approximation for density based on seismic wave velocity and elastic moduli would be beneficial. With the goal of finding other possible or better relationships between density and the elastic moduli, a database of density, P-wave velocity, S-wave velocity, bulk modulus, shear modulus, Young's modulus, and Poisson's ratio was compiled based on a multitude of lab samples. The database is comprised of isotropic, non-porous metamorphic rock. Multi-parameter cross plots of the various elastic parameters have been analyzed in order to find a suitable parameter combination that reduces high density outliers. As expected, the P-wave velocity to S-wave velocity ratios show no correlation with density. However, Birch's seismic parameter, along with the bulk modulus, shows promise in providing a link between observed compressional and shear wave velocities and rock densities, including massive sulfides and Fe-oxides.

Elastic properties of a porous titanium-bone tissue composite.

PubMed

Rubshtein, A P; Makarova, E B; Rinkevich, A B; Medvedeva, D S; Yakovenkova, L I; Vladimirov, A B

2015-01-01

The porous titanium implants were introduced into the condyles of tibias and femurs of sheep. New bone tissue fills the pore, and the porous titanium-new bone tissue composite is formed. The duration of composite formation was 4, 8, 24 and 52 weeks. The formed composites were extracted from the bone and subjected to a compression test. The Young's modulus was calculated using the measured stress-strain curve. The time dependence of the Young's modulus of the composite was obtained. After 4 weeks the new bone tissue that filled the pores does not affect the elastic properties of implants. After 24 and 52 weeks the Young's modulus increases by 21-34% and 62-136%, respectively. The numerical calculations of the elasticity of porous titanium-new bone tissue composite were conducted using a simple polydisperse model that is based on the consideration of heterogeneous structure as a continuous medium with spherical inclusions of different sizes. The kinetics of the change in the elasticity of the new bone tissue is presented via the intermediate characteristics, namely the relative ultimate tensile strength or proportion of mature bone tissue in the bone tissue. The calculated and experimentally measured values of the Young's modulus of the composite are in good agreement after 8 weeks of composite formation. The properties of the porous titanium-new bone tissue composites can only be predicted when data on the properties of new bone tissue are available after 8 weeks of contact between the implant and the native bone. Copyright © 2015 Elsevier B.V. All rights reserved.

Method of determining elastic and plastic mechanical properties of ceramic materials using spherical indenters

DOEpatents

Adler, Thomas A.

1996-01-01

The invention pertains a method of determining elastic and plastic mechanical properties of ceramics, intermetallics, metals, plastics and other hard, brittle materials which fracture prior to plastically deforming when loads are applied. Elastic and plastic mechanical properties of ceramic materials are determined using spherical indenters. The method is most useful for measuring and calculating the plastic and elastic deformation of hard, brittle materials with low values of elastic modulus to hardness.

Elasticity study of textured barium strontium titanate thin films by X-ray diffraction and laser acoustic waves

NASA Astrophysics Data System (ADS)

Chaabani, Anouar; Njeh, Anouar; Donner, Wolfgang; Klein, Andreas; Hédi Ben Ghozlen, Mohamed

2017-05-01

Ba0.65Sr0.35TiO3 (BST) thin films of 300 nm were deposited on Pt(111)/TiO2/SiO2/Si(001) substrates by radio frequency magnetron sputtering. Two thin films with different (111) and (001) fiber textures were prepared. X-ray diffraction was applied to measure texture. The raw pole figure data were further processed using the MTEX quantitative texture analysis software for plotting pole figures and calculating elastic constants and Young’s modulus from the orientation distribution function (ODF) for each type of textured fiber. The calculated elastic constants were used in the theoretical studies of surface acoustics waves (SAW) propagating in two types of multilayered BST systems. Theoretical dispersion curves were plotted by the application of the ordinary differential equation (ODE) and the stiffness matrix methods (SMM). A laser acoustic waves (LAW) technique was applied to generate surface acoustic waves (SAW) propagating in the BST films, and from a recursive process, the effective Young’s modulus are determined for the two samples. These methods are used to extract and compare elastic properties of two types of BST films, and quantify the influence of texture on the direction-dependent Young’s modulus.

Physical and mechanical characterisation of 3D-printed porous titanium for biomedical applications.

PubMed

El-Hajje, Aouni; Kolos, Elizabeth C; Wang, Jun Kit; Maleksaeedi, Saeed; He, Zeming; Wiria, Florencia Edith; Choong, Cleo; Ruys, Andrew J

2014-11-01

The elastic modulus of metallic orthopaedic implants is typically 6-12 times greater than cortical bone, causing stress shielding: over time, bone atrophies through decreased mechanical strain, which can lead to fracture at the implantation site. Introducing pores into an implant will lower the modulus significantly. Three dimensional printing (3DP) is capable of producing parts with dual porosity features: micropores by process (residual pores from binder burnout) and macropores by design via a computer aided design model. Titanium was chosen due to its excellent biocompatibility, superior corrosion resistance, durability, osteointegration capability, relatively low elastic modulus, and high strength to weight ratio. The mechanical and physical properties of 3DP titanium were studied and compared to the properties of bone. The mechanical and physical properties were tailored by varying the binder (polyvinyl alcohol) content and the sintering temperature of the titanium samples. The fabricated titanium samples had a porosity of 32.2-53.4% and a compressive modulus of 0.86-2.48 GPa, within the range of cancellous bone modulus. Other physical and mechanical properties were investigated including fracture strength, density, fracture toughness, hardness and surface roughness. The correlation between the porous 3DP titanium-bulk modulus ratio and porosity was also quantified.

Mechanical characterization of hydroxyapatite, thermoelectric materials and doped ceria

NASA Astrophysics Data System (ADS)

Fan, Xiaofeng

For a variety of applications of brittle ceramic materials, porosity plays a critical role structurally and/or functionally, such as in engineered bone scaffolds, thermoelectric materials and in solid oxide fuel cells. The presence of porosity will affect the mechanical properties, which are essential to the design and application of porous brittle materials. In this study, the mechanical property versus microstructure relations for bioceramics, thermoelectric (TE) materials and solid oxide fuel cells were investigated. For the bioceramic material hydroxyapatite (HA), the Young's modulus was measured using resonant ultrasound spectroscopy (RUS) as a function of (i) porosity and (ii) microcracking damage state. The fracture strength was measured as a function of porosity using biaxial flexure testing, and the distribution of the fracture strength was studied by Weibull analysis. For the natural mineral tetrahedrite based solid solution thermoelectric material (Cu10Zn2As4S13 - Cu 12Sb4S13), the elastic moduli, hardness and fracture toughness were studied as a function of (i) composition and (ii) ball milling time. For ZiNiSn, a thermoelectric half-Heusler compound, the elastic modulus---porosity and hardness---porosity relations were examined. For the solid oxide fuel cell material, gadolina doped ceria (GDC), the elastic moduli including Young's modulus, shear modulus, bulk modulus and Poisson's ratio were measured by RUS as a function of porosity. The hardness was evaluated by Vickers indentation technique as a function of porosity. The results of the mechanical property versus microstructure relations obtained in this study are of great importance for the design and fabrication of reliable components with service life and a safety factor. The Weibull modulus, which is a measure of the scatter in fracture strength, is the gauge of the mechanical reliability. The elastic moduli and Poisson's ratio are needed in analytical or numerical models of the thermal and mechanical stresses arising from in-service thermal gradients, thermal transients and/or mechanical loading. Hardness is related to a material's wear resistance and machinability, which are two essential considerations in fabrication and application.

Strengthening and toughening metallic glasses: The elastic perspectives and opportunities

NASA Astrophysics Data System (ADS)

Liu, Z. Q.; Zhang, Z. F.

2014-04-01

There exist general conflicts between strength and toughness in crystalline engineering materials, and various strengthening and toughening strategies have been developed from the dislocation motion perspectives. Metallic glasses (MGs) have demonstrated great potentials owing to their unique properties; however, their structural applications are strictly limited. One of the key problems is that the traditional strengthening and toughening strategies and mechanisms are not applicable in MGs due to the absence of dislocations and crystalline microstructures. Here, we show that the strength and toughness, or equivalently the shear modulus and Poisson's ratio, are invariably mutually exclusive in MGs. Accordingly, the MGs can be categorized into four groups with different levels of integrated mechanical properties. It is further revealed that the conflicts originate fundamentally from the atomic bonding structures and the levels of strength-toughness combinations are indeed dominated by the bulk modulus. Moreover, we propose novel strategies for optimizing the mechanical properties of MGs from the elastic perspectives. We emphasize the significance of developing high bulk modulus MGs to achieve simultaneously both high strength and good toughness and highlight the elastic opportunities for strengthening and toughening materials.

Effects of the size and content of protein aggregates on the rheological and structural properties of soy protein isolate emulsion gels induced by CaSO4.

PubMed

Wang, Xufeng; He, Zhiyong; Zeng, Maomao; Qin, Fang; Adhikari, Benu; Chen, Jie

2017-04-15

The effects of the size and content of soy protein isolate (SPI) aggregates on the rheological and textural properties of CaSO 4 -induced SPI emulsion gels were investigated. Considerable differences in the rheological, water-holding, and micro-structural properties were observed. The gels with larger and/or more SPI aggregates showed substantial increase in the elastic modulus and had lower gelation temperatures. Creep data suggested that the size of the SPI aggregates contributed more to the elastic modulus, whereas the increase of aggregate content enhanced the elastic modulus and viscous component of the gels. The water-holding capacity was markedly enhanced (p<0.05) with the increase in both the size and content of SPI aggregates. Confocal laser scanning microscopy and scanning electron microscopy showed that larger and/or more SPI aggregates resulted in more homogeneous networks with smaller oil droplets. These insights provide important information for the product development in relation to soy protein-stabilized emulsions and emulsion gels. Copyright © 2016. Published by Elsevier Ltd.

Improved Mechanical Compatibility and Cytocompatibility of Ta/Ti Double-Layered Composite Coating

NASA Astrophysics Data System (ADS)

Ding, Ding; Xie, Youtao; Li, Kai; Huang, Liping; Zheng, Xuebin

2017-08-01

In order to improve the mechanical compatibility and cytocompatibility of titanium implants, a composite coating with double layers composed of tantalum and titanium was designed and prepared using plasma spraying technology. In the composite coating, the upper tantalum layer provides a good biocompatibility, and the sublayer of titanium with a porous structure ensures the low elastic modulus. Results show that the fabricated composite coating exhibits a relatively low elastic modulus of 26.7 GPa, which is close to the elastic modulus of human cortical bone. In vitro cytocompatibility evaluation of the composite coating shows that the human bone marrow stromal cells exhibit enhanced adhesion and spreading performance on the double-layered composite coating in comparison with the single-layered titanium coating. In order to eliminate the misgivings of chemical stability of the composite coating in clinical application, electrochemical corrosion of the coating was examined. The results obtained revealed a very weak galvanic corrosion between the tantalum and titanium in the composite coating, which would ensure the safety of the coating in vivo.

Lattice dynamic properties of Rh2XAl (X=Fe and Y) alloys

NASA Astrophysics Data System (ADS)

Al, Selgin; Arikan, Nihat; Demir, Süleyman; Iyigör, Ahmet

2018-02-01

The electronic band structure, elastic and vibrational spectra of Rh2FeAl and Rh2YAl alloys were computed in detail by employing an ab-initio pseudopotential method and a linear-response technique based on the density-functional theory (DFT) scheme within a generalized gradient approximation (GGA). Computed lattice constants, bulk modulus and elastic constants were compared. Rh2YAl exhibited higher ability to resist volume change than Rh2FeAl. The elastic constants, shear modulus, Young modulus, Poisson's ratio, B/G ratio electronic band structure, total and partial density of states, and total magnetic moment of alloys were also presented. Rh2FeAl showed spin up and spin down states whereas Rh2YAl showed none due to being non-magnetic. The calculated total densities of states for both materials suggest that both alloys are metallic in nature. Full phonon spectra of Rh2FeAl and Rh2YA1 alloys in the L21 phase were collected using the ab-initio linear response method. The obtained phonon frequencies were in the positive region indicating that both alloys are dynamically stable.

Long-life physical property preservation and postendodontic rehabilitation with the Composipost.

PubMed

Duret, B; Duret, F; Reynaud, M

1996-01-01

Most coronal radicular reconstructions are made of cast inlay core metals or prefabricated posts covered in composite. The differences in the mechanical properties of these elements create a heterogeneous mass with inconsistent mechanical behavior. Studies using the Finite Element Method have shown the biomechanical disturbances caused by the inclusion of materials with a modulus of elasticity that is superior to that of dentine (i.e., nickel, chrome, zircon, etc). The use of materials with a modulus of elasticity close to that of dentine does not disturb the flow of stress inside the root. To our knowledge, only a composite material structured with programmable mechanical properties would be capable of producing both high mechanical performance and a modulus of elasticity adapted to dentine values. The C-POST, made of carbon epoxy, accommodates the demands of the dentine, as well as the in vitro stress linked to the prosthesis. The internal structure, consisting of long high-performance carbon fibers, unidirectionally and equally stretched, confers a totally original behavior that is adapted to clinical objectives. In addition, the C-POST has a fracture resistance superior to most metals.

Investigation of different physical aspects such as structural, mechanical, optical properties and Debye temperature of Fe2ScM (M=P and As) semiconductors: A DFT-based first principles study

NASA Astrophysics Data System (ADS)

Ali, Md. Lokman; Rahaman, Md. Zahidur

2018-04-01

By using first principles calculation dependent on the density functional theory (DFT), we have investigated the mechanical, structural properties and the Debye temperature of Fe2ScM (M=P and As) compounds under various pressures up to 60 GPa. The optical properties have been investigated under zero pressure. Our calculated optimized structural parameters of both the materials are in good agreement with other theoretical predictions. The calculated elastic constants show that Fe2ScM (M=P and As) compounds are mechanically stable under external pressure below 60 GPa. From the elastic constants, the shear modulus G, the bulk modulus B, Young’s modulus E, anisotropy factor A and Poisson’s ratio ν are calculated by using the Voigt-Reuss-Hill approximation. The Debye temperature and average sound velocities are also investigated from the obtained elastic constants. The detailed analysis of all optical functions reveals that both compounds are good dielectric material.

An overview of self-consistent methods for fiber-reinforced composites

NASA Technical Reports Server (NTRS)

Gramoll, Kurt C.; Freed, Alan D.; Walker, Kevin P.

1991-01-01

The Walker et al. (1989) self-consistent method to predict both the elastic and the inelastic effective material properties of composites is examined and compared with the results of other self-consistent and elastically based solutions. The elastic part of their method is shown to be identical to other self-consistent methods for non-dilute reinforced composite materials; they are the Hill (1965), Budiansky (1965), and Nemat-Nasser et al. (1982) derivations. A simplified form of the non-dilute self-consistent method is also derived. The predicted, elastic, effective material properties for fiber reinforced material using the Walker method was found to deviate from the elasticity solution for the v sub 31, K sub 12, and mu sub 31 material properties (fiber is in the 3 direction) especially at the larger volume fractions. Also, the prediction for the transverse shear modulus, mu sub 12, exceeds one of the accepted Hashin bounds. Only the longitudinal elastic modulus E sub 33 agrees with the elasticity solution. The differences between the Walker and the elasticity solutions are primarily due to the assumption used in the derivation of the self-consistent method, i.e., the strain fields in the inclusions and the matrix are assumed to remain constant, which is not a correct assumption for a high concentration of inclusions.

Cone penetrometer equipped with piezoelectric sensors for measurement of soil stiffness in highway pavement : executive summary report.

DOT National Transportation Integrated Search

2005-11-01

The stiffness (elastic modulus and shear modulus) and Poissons ratio of the base and : sublayers are important parameters in the design and quality assurance during construction of : highway pavements. During and after the construction of a paveme...

Inverse finite element methods for extracting elastic-poroviscoelastic properties of cartilage and other soft tissues from indentation

NASA Astrophysics Data System (ADS)

Namani, Ravi

Mechanical properties are essential for understanding diseases that afflict various soft tissues, such as osteoarthritic cartilage and hypertension which alters cardiovascular arteries. Although the linear elastic modulus is routinely measured for hard materials, standard methods are not available for extracting the nonlinear elastic, linear elastic and time-dependent properties of soft tissues. Consequently, the focus of this work is to develop indentation methods for soft biological tissues; since analytical solutions are not available for the general context, finite element simulations are used. First, parametric studies of finite indentation of hyperelastic layers are performed to examine if indentation has the potential to identify nonlinear elastic behavior. To answer this, spherical, flat-ended conical and cylindrical tips are examined and the influence of thickness is exploited. Also the influence of the specimen/substrate boundary condition (slip or non-slip) is clarified. Second, a new inverse method---the hyperelastic extraction algorithm (HPE)---was developed to extract two nonlinear elastic parameters from the indentation force-depth data, which is the basic measurement in an indentation test. The accuracy of the extracted parameters and the influence of noise in measurements on this accuracy were obtained. This showed that the standard Berkovitch tip could only extract one parameter with sufficient accuracy, since the indentation force-depth curve has limited sensitivity to both nonlinear elastic parameters. Third, indentation methods for testing tissues from small animals were explored. New methods for flat-ended conical tips are derived. These account for practical test issues like the difficulty in locating the surface or soft specimens. Also, finite element simulations are explored to elucidate the influence of specimen curvature on the indentation force-depth curve. Fourth, the influence of inhomogeneity and material anisotropy on the extracted "average" linear elastic modulus was studied. The focus here is on murine tibial cartilage, since recent experiments have shown that the modulus measured by a 15 mum tip is considerably larger than that obtained from a 90 mum tip. It is shown that a depth-dependent modulus could give rise to such a size effect. Lastly, parametric studies were performed within the small strain setting to understand the influence of permeability and viscoelastic properties on the indentation stress-relaxation response. The focus here is on cartilage, and specific test protocols (single-step vs. multi-step stress relaxation) are explored. An inverse algorithm was developed to extract the poroviscoelastic parameters. A sensitivity study using this algorithm shows that the instantaneous elastic modulus (which is a measure of the viscous relaxation) can be extracted with very good accuracy, but the permeability and long-time relaxation constant cannot be extracted with good accuracy. The thesis concludes with implications of these studies. The potential and limitations of indentation tests for studying cartilage and other soft tissues is discussed.

Effects of the 3D bone-to-implant contact and bone stiffness on the initial stability of a dental implant: micro-CT and resonance frequency analyses.

PubMed

Hsu, J T; Huang, H L; Tsai, M T; Wu, A Y J; Tu, M G; Fuh, L J

2013-02-01

This study investigated the effects of bone stiffness (elastic modulus) and three-dimensional (3D) bone-to-implant contact ratio (BIC%) on the primary stabilities of dental implants using micro-computed tomography (micro-CT) and resonance frequency analyses. Artificial sawbone models with five values of elastic modulus (137, 123, 47.5, 22, and 12.4 MPa) comprising two types of trabecular structure (solid-rigid and cellular-rigid) were investigated for initial implant stability quotient (ISQ), measured using the wireless Osstell resonance frequency analyzer. Bone specimens were attached to 2 mm fibre-filled epoxy sheets mimicking the cortical shell. ISQ was measured after placing a dental implant into the bone specimen. Each bone specimen with an implant was subjected to micro-CT scanning to calculate the 3D BIC% values. The similarity of the cellular type of artificial bone to the trabecular structure might make it more appropriate for obtaining accurate values of primary implant stability than solid-bone blocks. For the cellular-rigid bone models, the ISQ increased with the elastic modulus of cancellous bone. The regression correlation coefficient was 0.96 for correlations of the ISQ with the elasticity of cancellous bone and with the 3D BIC%. The initial implant stability was moderately positively correlated with the elasticity of cancellous bone and with the 3D BIC%. Copyright © 2012 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

First Principles Investigation of Fluorine Based Strontium Series of Perovskites

NASA Astrophysics Data System (ADS)

Erum, Nazia; Azhar Iqbal, Muhammad

2016-11-01

Density functional theory is used to explore structural, elastic, and mechanical properties of SrLiF3, SrNaF3, SrKF3 and SrRbF3 fluoroperovskite compounds by means of an ab-initio Full Potential-Linearized Augmented Plane Wave (FP-LAPW) method. Several lattice parameters are employed to obtain accurate equilibrium volume (Vo). The resultant quantities include ground state energy, elastic constants, shear modulus, bulk modulus, young's modulus, cauchy's pressure, poisson's ratio, shear constant, ratio of elastic anisotropy factor, kleinman's parameter, melting temperature, and lame's coefficient. The calculated structural parameters via DFT as well as analytical methods are found to be consistent with experimental findings. Chemical bonding is used to investigate corresponding chemical trends which authenticate combination of covalent-ionic behavior. Furthermore electron density plots as well as elastic and mechanical properties are reported for the first time which reveals that fluorine based strontium series of perovskites are mechanically stable and posses weak resistance towards shear deformation as compared to resistance towards unidirectional compression while brittleness and ionic behavior is dominated in them which decreases from SrLiF3 to SrRbF3. Calculated cauchy's pressure, poisson's ratio and B/G ratio also proves ionic nature in these compounds. The present methodology represents an effective and influential approach to calculate the whole set of elastic and mechanical parameters which would support to understand various physical phenomena and empower device engineers for implementing these materials in numerous applications.

Non-Muscle Myosin II Isoforms Have Different Functions in Matrix Rearrangement by MDA-MB-231 Cells

PubMed Central

Hindman, Bridget; Goeckeler, Zoe; Sierros, Kostas; Wysolmerski, Robert

2015-01-01

The role of a stiffening extra-cellular matrix (ECM) in cancer progression is documented but poorly understood. Here we use a conditioning protocol to test the role of nonmuscle myosin II isoforms in cell mediated ECM arrangement using collagen constructs seeded with breast cancer cells expressing shRNA targeted to either the IIA or IIB heavy chain isoform. While there are several methods available to measure changes in the biophysical characteristics of the ECM, we wanted to use a method which allows for the measurement of global stiffness changes as well as a dynamic response from the sample over time. The conditioning protocol used allows the direct measurement of ECM stiffness. Using various treatments, it is possible to determine the contribution of various construct and cellular components to the overall construct stiffness. Using this assay, we show that both the IIA and IIB isoforms are necessary for efficient matrix remodeling by MDA-MB-231 breast cancer cells, as loss of either isoform changes the stiffness of the collagen constructs as measured using our conditioning protocol. Constructs containing only collagen had an elastic modulus of 0.40 Pascals (Pa), parental MDA-MB-231 constructs had an elastic modulus of 9.22 Pa, while IIA and IIB KD constructs had moduli of 3.42 and 7.20 Pa, respectively. We also calculated the cell and matrix contributions to the overall sample elastic modulus. Loss of either myosin isoform resulted in decreased cell stiffness, as well as a decrease in the stiffness of the cell-altered collagen matrices. While the total construct modulus for the IIB KD cells was lower than that of the parental cells, the IIB KD cell-altered matrices actually had a higher elastic modulus than the parental cell-altered matrices (4.73 versus 4.38 Pa). These results indicate that the IIA and IIB heavy chains play distinct and non-redundant roles in matrix remodeling. PMID:26136073

Hardness and Elastic Modulus on Six-Fold Symmetry Gold Nanoparticles

PubMed Central

Ramos, Manuel; Ortiz-Jordan, Luis; Hurtado-Macias, Abel; Flores, Sergio; Elizalde-Galindo, José T.; Rocha, Carmen; Torres, Brenda; Zarei-Chaleshtori, Maryam; Chianelli, Russell R.

2013-01-01

The chemical synthesis of gold nanoparticles (NP) by using gold (III) chloride trihydrate (HAuCl∙3H2O) and sodium citrate as a reducing agent in aqueous conditions at 100 °C is presented here. Gold nanoparticles areformed by a galvanic replacement mechanism as described by Lee and Messiel. Morphology of gold-NP was analyzed by way of high-resolution transmission electron microscopy; results indicate a six-fold icosahedral symmetry with an average size distribution of 22 nm. In order to understand the mechanical behaviors, like hardness and elastic moduli, gold-NP were subjected to nanoindentation measurements—obtaining a hardness value of 1.72 GPa and elastic modulus of 100 GPa in a 3–5 nm of displacement at the nanoparticle’s surface. PMID:28809302

Eliminating electromechanical instability in dielectric elastomers by employing pre-stretch

NASA Astrophysics Data System (ADS)

Jiang, Liang; Betts, Anthony; Kennedy, David; Jerrams, Stephen

2016-07-01

Electromechanical instability (EMI) is one of most common failure modes for dielectric elastomers (DEs). It has been reported that pre-stretching a DE sample can suppress EMI due to strain stiffening taking place for larger strains and a higher elastic modulus are achieved at high stretch ratios when a voltage is applied to the material. In this work, the influence of equi-biaxial stretch on DE secant modulus was studied using VHB 4910 and silicone rubber (SR) composites containing barium titanate (BaTiO3, BT) particles and also dopamine coated BT (DP-BT) particles. The investigation of equi-biaxial deformation and EMI failure for VHB 4910 was undertaken by introducing a voltage-stretch function. The results showed that EMI was suppressed by equi-biaxial pre-stretch for all the DEs fabricated and tested. The stiffening properties of the DE materials were also studied with respect to the secant modulus. Furthermore, a voltage-induced strain of above 200% was achieved for the polyacrylate film by applying a pre-stretch ratio of 2.0 without EMI occurring. However, a maximum voltage-induced strain in the polyacrylate film of 78% was obtained by the SR/20 wt% DP-BT composite for a lower applied pre-stretch ratio of 1.6 and again EMI was eliminated.

Factors affecting the thermal shock behavior of yttria stabilized hafnia based graphite and tungsten composites.

NASA Technical Reports Server (NTRS)

Lineback, L. D.; Manning, C. R.

1971-01-01

Hafnia-based composites containing either graphite or tungsten were investigated as rocket nozzle throat inserts in solid propellant rocket engines. The thermal shock resistance of these materials is considered in terms of macroscopic thermal conductivity, thermal expansion, modulus of elasticity, and compressive fracture stress. The effect of degree of hafnia stabilization, density, and graphite or tungsten content upon these parameters is discussed. The variation of the ratio of elastic modulus to compressive fracture stress with density and its effect upon thermal shock resistance of these materials are discussed in detail.

Surface Wave Metrology for Copper/Low-k Interconnects

NASA Astrophysics Data System (ADS)

Gostein, M.; Maznev, A. A.; Mazurenko, A.; Tower, J.

2005-09-01

We review recent advances in the application of laser-induced surface acoustic wave metrology to issues in copper/low-k interconnect development and manufacturing. We illustrate how the metrology technique can be used to measure copper thickness uniformity on a range of features from solid pads to arrays of lines, focusing on specific processing issues in copper electrochemical deposition (ECD) and chemical-mechanical polishing (CMP). In addition, we review recent developments in surface wave metrology for the characterization of low-k dielectric elastic modulus, including the ability to measure within-wafer uniformity of elastic modulus and to characterize porous, anisotropic films.

Elastic superlattices with simultaneously negative effective mass density and shear modulus

NASA Astrophysics Data System (ADS)

Solís-Mora, I. S.; Palomino-Ovando, M. A.; Pérez-Rodríguez, F.

2013-03-01

We investigate the vibrational properties of superlattices with layers of rubber and polyurethane foam, which can be either conventional or auxetic. Phononic dispersion calculations show a second pass band for transverse modes inside the lowest band gap of the longitudinal modes. In such a band, the superlattices behave as a double-negative elastic metamaterial since the effective dynamic mass density and shear modulus are both negative. The pass band is associated to a Fabry-Perot resonance band which turns out to be very narrow as a consequence of the high contrast between the acoustic impedances of the superlattice components.

Estimation of elasticity map of soft biological tissue mimicking phantom using laser speckle contrast analysis

NASA Astrophysics Data System (ADS)

Suheshkumar Singh, M.; Rajan, K.; Vasu, R. M.

2011-05-01

Scattering of coherent light from scattering particles causes phase shift to the scattered light. The interference of unscattered and scattered light causes the formation of speckles. When the scattering particles, under the influence of an ultrasound (US) pressure wave, vibrate, the phase shift fluctuates, thereby causing fluctuation in speckle intensity. We use the laser speckle contrast analysis (LSCA) to reconstruct a map of the elastic property (Young's modulus) of soft tissue-mimicking phantom. The displacement of the scatters is inversely related to the Young's modulus of the medium. The elastic properties of soft biological tissues vary, many fold with malignancy. The experimental results show that laser speckle contrast (LSC) is very sensitive to the pathological changes in a soft tissue medium. The experiments are carried out on a phantom with two cylindrical inclusions of sizes 6mm in diameter, separated by 8mm between them. Three samples are made. One inclusion has Young's modulus E of 40kPa. The second inclusion has either a Young's modulus E of 20kPa, or scattering coefficient of μs'=3.00mm-1 or absorption coefficient of μa=0.03mm-1. The optical absorption (μa), reduced scattering (μs') coefficient, and the Young's modulus of the background are μa=0.01mm-1, μs'=1.00mm-1 and 12kPa, respectively. The experiments are carried out on all three phantoms. On a phantom with two inclusions of Young's modulus of 20 and 40kPa, the measured relative speckle image contrasts are 36.55% and 63.72%, respectively. Experiments are repeated on phantoms with inclusions of μa=0.03mm-1, E =40kPa and μs'=3.00mm-1. The results show that it is possible to detect inclusions with contrasts in optical absorption, optical scattering, and Young's modulus. Studies of the variation of laser speckle contrast with ultrasound driving force for various values of μa, μs', and Young's modulus of the tissue mimicking medium are also carried out.

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).

Tensile properties of SiC/aluminum filamentary composites - Thermal degradation effects

NASA Technical Reports Server (NTRS)

Skinner, A.; Koczak, M. J.; Lawley, A.

1982-01-01

Aluminium metal matrix composites with a low cost fiber, e.g. SiC, provide for an attractive combination of high elastic modulus and longitudinal strengths coupled with a low density. SiC (volume fraction 0.55)-aluminum (6061) systems have been studied in order to optimize fiber composite strength and processing parameters. A comparison of two SiC/aluminum composites produced by AVCO and DWA is provided. Fiber properties are shown to alter composite tensile properties and fracture morphology. The room temperature tensile strengths appear to be insensitive to thermal exposures at 500 C up to 150 h. The elastic modulus of the composites also appears to be stable up to 400 C, however variations in the loss modulus are apparent. The fracture morphology reflects the quality of the interfacial bond, fiber strengths and fiber processing.

Elastic Moduli of Pyrolytic Boron Nitride Measured Using 3-Point Bending and Ultrasonic Testing

NASA Technical Reports Server (NTRS)

Kaforey, M. L.; Deeb, C. W.; Matthiesen, D. H.; Roth, D. J.

1999-01-01

Three-point bending and ultrasonic testing were performed on a flat plate of PBN. In the bending experiment, the deformation mechanism was believed to be shear between the pyrolytic layers, which yielded a shear modulus, c (sub 44), of 2.60 plus or minus .31 GPa. Calculations based on the longitudinal and shear wave velocity measurements yielded values of 0.341 plus or minus 0.006 for Poisson's ratio, 10.34 plus or minus .30 GPa for the elastic modulus (c (sub 33)), and 3.85 plus or minus 0.02 GPa for the shear modulus (c (sub 44)). Since free basal dislocations have been reported to affect the value of c (sub 44) found using ultrasonic methods, the value from the bending experiment was assumed to be the more accurate value.

Imperfection sensitivity of pressured buckling of biopolymer spherical shells

NASA Astrophysics Data System (ADS)

Zhang, Lei; Ru, C. Q.

2016-06-01

Imperfection sensitivity is essential for mechanical behavior of biopolymer shells [such as ultrasound contrast agents (UCAs) and spherical viruses] characterized by high geometric heterogeneity. In this work, an imperfection sensitivity analysis is conducted based on a refined shell model recently developed for spherical biopolymer shells of high structural heterogeneity and thickness nonuniformity. The influence of related parameters (including the ratio of radius to average shell thickness, the ratio of transverse shear modulus to in-plane shear modulus, and the ratio of effective bending thickness to average shell thickness) on imperfection sensitivity is examined for pressured buckling. Our results show that the ratio of effective bending thickness to average shell thickness has a major effect on the imperfection sensitivity, while the effect of the ratio of transverse shear modulus to in-plane shear modulus is usually negligible. For example, with physically realistic parameters for typical imperfect spherical biopolymer shells, the present model predicts that actual maximum external pressure could be reduced to as low as 60% of that of a perfect UCA spherical shell or 55%-65% of that of a perfect spherical virus shell, respectively. The moderate imperfection sensitivity of spherical biopolymer shells with physically realistic imperfection is largely attributed to the fact that biopolymer shells are relatively thicker (defined by smaller radius-to-thickness ratio) and therefore practically realistic imperfection amplitude normalized by thickness is very small as compared to that of classical elastic thin shells which have much larger radius-to-thickness ratio.

Smooth muscle-dependent changes in aortic wall dynamics during intra-aortic counterpulsation in an animal model of acute heart failure.

PubMed

Cabrera Fischer, Edmundo I; Bia, Daniel; Zócalo, Yanina; Armentano, Ricardo L

2009-06-01

Intra-aortic balloon pumping (IABP) may modify arterial biomechanics; however, its effects on arterial wall properties during acute cardio-depression have not yet been fully explored. This dynamical study was designed to characterize the effects of IABP on aortic wall mechanics in an in vivo animal model of acute heart failure. Aortic pressure, diameter and blood flow were measured in six anesthetized sheep with acute cardio-depression by halothane (4%), before and during IABP (1:2). Aortic characteristic impedance and aortic wall stiffness indexes were calculated. acute experimental cardio-depression resulted in a reduction in mean aortic pressure (p<0.05) and an increase in the characteristic impedance (p<0.005), incremental elastic modulus (p<0.05), stiffness index (p<0.05) and Peterson elastic modulus (p<0.05). IABP caused an increase in the cardiac output (p<0.005) and a reduction in the systemic vascular resistances (p<0.05). In addition, the aortic impedance, incremental elastic modulus, stiffness index and Peterson modulus were significantly reduced during IABP (p<0.05). Our findings show that IABP caused changes in aortic wall impedance and intrinsic wall properties, improving the arterial functional capability and the left ventricular afterload by a reduction in both. Systemic vascular resistances and aortic stiffness were also improved by means of smooth muscle-dependent mechanisms.

Modified atomic force microscope applied to the measurement of elastic modulus for a single peptide molecule

NASA Astrophysics Data System (ADS)

Ptak, Arkadiusz; Takeda, Seiji; Nakamura, Chikashi; Miyake, Jun; Kageshima, Masami; Jarvis, Suzanne P.; Tokumoto, Hiroshi

2001-09-01

A modified atomic force microscopy (AFM) system, based on a force modulation technique, has been used to find an approximate value for the elastic modulus of a single peptide molecule directly from a mechanical test. For this purpose a self-assembled monolayer built from two kinds of peptides, reactive (able to anchor to the AFM tip) and nonreactive, was synthesized. In a typical experiment a single C3K30C (C=cysteine, K=lysine) peptide molecule was stretched between a Au(111) substrate and the gold-coated tip of an AFM cantilever to which it was attached via gold-sulfur bonds. The amplitude of the cantilever oscillations, due to an external force applied via a magnetic particle to the cantilever, was recorded by a lock-in amplifier and recalculated into stiffness of the stretched molecule. A longitudinal Young's modulus for the α-helix of a single peptide molecule and for the elongated state of this molecule has been estimated. The obtained values; 1.2±0.3 and 50±15 GPa, for the peptide α-helix and elongated peptide backbone, respectively, seem to be reasonable comparing them to the Young's modulus of protein crystals and linear organic polymers. We believe this research opens up a means by which scientists can perform quantitative studies of the elastic properties of single molecule, especially of biologically important polymers like peptides or DNA.

Nondestructive evaluation of hydrogel mechanical properties using ultrasound

PubMed Central

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

2012-01-01

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

Hardness and modulus of elasticity of primary and permanent teeth after wear against different dental materials

PubMed Central

Galo, Rodrigo; Contente, Marta Maria Martins Giamatei; Galafassi, Daniel; Borsatto, Maria Cristina

2015-01-01

Objectives: The purpose of this study was to determine the Young's modulus and the hardness of deciduous and permanent teeth following wear challenges using different dental materials. Materials and Methods: Wear challenges were performed against four dental materials: A resin-based fissure sealant (Fluoroshield®), a glass ionomer based fissure sealant (Vitremer®), and two microhybrid composite resins (Filtek Z250 and P90®). Using the pin-on-plate design, a deciduous or a permanent tooth was made into a pin (4 mm × 4 mm × 2 mm) working at a 3 N vertical load, 1 Hz frequency, and 900 cycles (15 min) with Fusayama artificial saliva as a lubricant. Before and after the tribological tests, the hardness and elasticity modulus of the tooth samples were measured by creating a nanoindentation at load forces up to 50 mN and 150 mN. All of the results were statistically analyzed using ANOVA and post-hoc Duncan's tests (P < 0.05). Results: No difference in hardness was encountered between deciduous and permanent teeth (P < 0.05) or modulus of elasticity (P < 0.05) before or after the wear challenges for all of the dental materials tested. Conclusions: Wear challenges against the studied dental materials did not alter the properties of permanent or deciduous teeth after the application of a 3 N load. PMID:26929700

Computationally designed lattices with tuned properties for tissue engineering using 3D printing

PubMed Central

Gonella, Veronica C.; Engensperger, Max; Ferguson, Stephen J.; Shea, Kristina

2017-01-01

Tissue scaffolds provide structural support while facilitating tissue growth, but are challenging to design due to diverse property trade-offs. Here, a computational approach was developed for modeling scaffolds with lattice structures of eight different topologies and assessing properties relevant to bone tissue engineering applications. Evaluated properties include porosity, pore size, surface-volume ratio, elastic modulus, shear modulus, and permeability. Lattice topologies were generated by patterning beam-based unit cells, with design parameters for beam diameter and unit cell length. Finite element simulations were conducted for each topology and quantified how elastic modulus and shear modulus scale with porosity, and how permeability scales with porosity cubed over surface-volume ratio squared. Lattices were compared with controlled properties related to porosity and pore size. Relative comparisons suggest that lattice topology leads to specializations in achievable properties. For instance, Cube topologies tend to have high elastic and low shear moduli while Octet topologies have high shear moduli and surface-volume ratios but low permeability. The developed method was utilized to analyze property trade-offs as beam diameter was altered for a given topology, and used to prototype a 3D printed lattice embedded in an interbody cage for spinal fusion treatments. Findings provide a basis for modeling and understanding relative differences among beam-based lattices designed to facilitate bone tissue growth. PMID:28797066

Computationally designed lattices with tuned properties for tissue engineering using 3D printing.

PubMed

Egan, Paul F; Gonella, Veronica C; Engensperger, Max; Ferguson, Stephen J; Shea, Kristina

2017-01-01

Tissue scaffolds provide structural support while facilitating tissue growth, but are challenging to design due to diverse property trade-offs. Here, a computational approach was developed for modeling scaffolds with lattice structures of eight different topologies and assessing properties relevant to bone tissue engineering applications. Evaluated properties include porosity, pore size, surface-volume ratio, elastic modulus, shear modulus, and permeability. Lattice topologies were generated by patterning beam-based unit cells, with design parameters for beam diameter and unit cell length. Finite element simulations were conducted for each topology and quantified how elastic modulus and shear modulus scale with porosity, and how permeability scales with porosity cubed over surface-volume ratio squared. Lattices were compared with controlled properties related to porosity and pore size. Relative comparisons suggest that lattice topology leads to specializations in achievable properties. For instance, Cube topologies tend to have high elastic and low shear moduli while Octet topologies have high shear moduli and surface-volume ratios but low permeability. The developed method was utilized to analyze property trade-offs as beam diameter was altered for a given topology, and used to prototype a 3D printed lattice embedded in an interbody cage for spinal fusion treatments. Findings provide a basis for modeling and understanding relative differences among beam-based lattices designed to facilitate bone tissue growth.

Elastic and microplastic properties of titanium in different structural states

NASA Astrophysics Data System (ADS)

Kardashev, B. K.; Betekhtin, V. I.; Kadomtsev, A. G.; Narykova, M. V.; Kolobov, Yu. R.

2017-09-01

The behavior of elastic (Young's modulus) and microplastic properties of titanium depending on the initial structure and subsequent severe plastic deformation that transforms the material (concerning the grain size) into the submicrocrystalline structural state has been studied. It has been shown that, to a great extent, different initial structures of the metal predetermine its elastic properties after deformation.

Low Activation Joining of SiC/SiC Composites for Fusion Applications: Modeling Miniature Torsion Tests with Elastic and Elastic-Plastic Models

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

Henager, Charles H.; Nguyen, Ba Nghiep; Kurtz, Richard J.

2015-06-30

The international fusion community designed miniature torsion specimens for joint testing and irradiation in test reactors with limited irradiation volumes since SiC and SiC-composites used in fission or fusion environments require joining methods for assembling systems. Torsion specimens fail out-of-plane when joints are strong and when elastic moduli are comparable to SiC, which causes difficulties in determining shear strengths for many joints or for comparing unirradiated and irradiated joints. A finite element damage model was developed to treat elastic joints such as SiC/Ti3SiC2+SiC and elastic-plastic joints such as SiC/epoxy and steel/epoxy. The model uses constitutive shear data and is validatedmore » using epoxy joint data. The elastic model indicates fracture is likely to occur within the joined pieces to cause out-of-plane failures for miniature torsion specimens when a certain modulus and strength ratio between the joint material and the joined material exists. Lower modulus epoxy joints always fail in plane and provide good model validation.« less

Low temperature internal friction spectrum of YBa 2Cu 3O x

NASA Astrophysics Data System (ADS)

Mi, Y.; Schaller, R.; Berger, H.; Benoit, W.; Sathish, S.

1991-01-01

The elastic and anelastic behaviours of polycrystalline YBa 2Cu 3O x specimens have been studied between 80 and 300 K, by means of a resonant bar technique. Three damping peaks have been observed at 90, 115 and 220 K. The stability of these peaks during annealing in vacuum has been carefully examined. The 90 K peak is not related to the superconducting transition because it is still observed after thermal treatments leading to the disappearance of superconductivity. The 115 K is due to a relaxation mechanism. The activation energy is ∼0.17 eV and the frequency factor is ∼10 12s -1. Also this peak is certainly correlated with the excess oxygen atoms, because it disappears with annealing in vacuum. The 220 K maximum, which was also observed by ultrasonic measurements, seems to be affected by the sample preparation, i.e. by the sintering conditions. Finally, a frequency hysteresis has been observed in every superconducting sample, which accounts for an anomalous behaviour of the elastic modulus.

On the propulsive efficiency of rotating elastica.

NASA Astrophysics Data System (ADS)

Fermigier, Marc; Champagne, Nicolas; Laik, Eric; Marthelot, Joel; Du Roure, Olivia

2007-11-01

A majority of microorganisms propel themselves with long flexible cilia or flagella. Understanding in detail the hydrodynamics of such propulsion mechanisms is important both from biological and engineering point of views, in particular to design artificial microswimmers. We report an experimental investigation of the propulsive force delivered by a rotating elastic filament. Macroscopic filaments made of an elastomer (Young's modulus E) loaded with solid particles to match the density of the suspending liquid are rotated at constant velocity φ in a bath of glycerin. Their three dimensional shape is time independent but varies with φ and aspect ratio L/a. The force on the filament is computed from the experimental shape using a slender body approximation (ratio of perpendicular and parallel friction coefficients : ζ= 2 ζ). The evolution of axial force is captured by a single dimensionless parameter comparing viscous and elastic stresses: Sp = (ηφ/E) (L/a)^4. As for a planar oscillating flexible tail a maximum force is found at Sp 1.

On the realization of the bulk modulus bounds for two-phase viscoelastic composites

NASA Astrophysics Data System (ADS)

Andreasen, Casper Schousboe; Andreassen, Erik; Jensen, Jakob Søndergaard; Sigmund, Ole

2014-02-01

Materials with good vibration damping properties and high stiffness are of great industrial interest. In this paper the bounds for viscoelastic composites are investigated and material microstructures that realize the upper bound are obtained by topology optimization. These viscoelastic composites can be realized by additive manufacturing technologies followed by an infiltration process. Viscoelastic composites consisting of a relatively stiff elastic phase, e.g. steel, and a relatively lossy viscoelastic phase, e.g. silicone rubber, have non-connected stiff regions when optimized for maximum damping. In order to ensure manufacturability of such composites the connectivity of the matrix is ensured by imposing a conductivity constraint and the influence on the bounds is discussed.

Evaluation of the Carrying Capacity of Rectangular Steel-Concrete Columns

NASA Astrophysics Data System (ADS)

Vatulia, Glib; Rezunenko, Maryna; Petrenko, Dmytro; Rezunenko, Sergii

2018-06-01

Experimental studies of rectangular steel-concrete columns under centric compression with random eccentricity were conducted. The stress-strain state and the carrying capacity exhaustion have been assessed. The regression dependence is proposed to determine the maximum carrying capacity of such columns. The mathematical model takes into account the combined influence of the physical and geometric characteristics of the columns, such as their length, crosssectional area, casing thickness, prism strength of concrete, yield strength of steel, modulus of elasticity of both steel and concrete. The correspondence of the obtained model to the experimental data, as well as the significance of the regression parameters are confirmed by the Fisher and Student criteria.

Mechanical properties and XRD of Nafion modified by 2-hydroxyethylammonium ionic liquids

NASA Astrophysics Data System (ADS)

Garaev, V.; Pavlovica, S.; Reinholds, I.; Vaivars, G.

2013-12-01

In this work, the Nafion 112 membrane impregnated with 2-hydroxyethylammonium carboxylate ionic liquids have been investigated. The used ionic liquids were 2-hydroxyethylammonium formate [HEA]F, acetate [HEA]A and lactate [HEA]L. Prepared composite membranes Nafion/ionic liquid are characterized by mechanical testing, such as tensile test and creep test. It is found that ionic liquids decrease elastic modulus and creep compliance, but do not have significant effect on the tensile strength. Also, composite membranes were studied by wide angle X-ray diffraction. All ionic liquids shift the peak maximum to the lower angle. In this work, only biodegradable ionic liquids were used for composite preparation.

Acoustic and elastic waves in metamaterials for underwater applications

NASA Astrophysics Data System (ADS)

Titovich, Alexey S.

Elastic effects in acoustic metamaterials are investigated. Water-based periodic arrays of elastic scatterers, sonic crystals, suffer from low transmission due to the impedance and index mismatch of typical engineering materials with water. A new type of acoustic metamaterial element is proposed that can be tuned to match the acoustic properties of water in the quasi-static regime. The element comprises a hollow elastic cylindrical shell fitted with an optimized internal substructure consisting of a central mass supported by an axisymmetric distribution of elastic stiffeners, which dictate the shell's effective bulk modulus and density. The derived closed form scattering solution for this system shows that the subsonic flexural waves excited in the shell by the attachment of stiffeners are suppressed by including a sufficiently large number of such stiffeners. As an example of refraction-based wave steering, a cylindrical-to-plane wave lens is designed by varying the bulk modulus in the array according to the conformal mapping of a unit circle to a square. Elastic shells provide rich scattering properties, mainly due to their ability to support highly dispersive flexural waves. Analysis of flexural-borne waves on a pair of shells yields an analytical expression for the width of a flexural resonance, which is then used with the theory of multiple scattering to accurately predict the splitting of the resonance frequency. This analysis leads to the discovery of the acoustic Poisson-like effect in a periodic wave medium. This effect redirects an incident acoustic wave by 90° in an otherwise acoustically transparent sonic crystal. An unresponsive "deaf" antisymmetric mode locked to band gap boundaries is unlocked by matching Bragg scattering with a quadrupole flexural resonance of the shell. The dynamic effect causes normal unidirectional wave motion to strongly couple to perpendicular motion, analogous to the quasi-static Poisson effect in solids. The Poisson-like effect is demonstrated using the first flexural resonance of an acrylic shell. This represent a new type of material which cannot be accurately described as an effective acoustic medium. The study concludes with an analysis of a non-zero shear modulus in a pentamode cloak via the two-scale method with the shear modulus as the perturbation parameter.

Primate lens capsule elasticity assessed using Atomic Force Microscopy

PubMed Central

Ziebarth, Noël M.; Arrieta, Esdras; Feuer, William J.; Moy, Vincent T.; Manns, Fabrice; Parel, Jean-Marie

2011-01-01

The purpose of this project is to measure the elasticity of the human and non-human primate lens capsule at the microscopic scale using Atomic Force Microscopy (AFM). Elasticity measurements were performed using AFM on the excised anterior lens capsule from 9 cynomolgus monkey (5.9–8.0 years), 8 hamadryas baboon (2.8–10.1 years), and 18 human lenses (33–79 years). Anterior capsule specimens were obtained by performing a 5mm continuous curvilinear capsulorhexis and collecting the resulting disk of capsular tissue. To remove the lens epithelial cells the specimen was soaked in 0.1% trypsin and 0.02% EDTA for five minutes, washed, and placed on a Petri dish and immersed in DMEM. Elasticity measurements of the capsule were performed with a laboratory-built AFM system custom designed for force measurements of ophthalmic tissues. The capsular specimens were probed with an AFM cantilever tip to produce force-indentation curves for each specimen. Young’s modulus was calculated from the force-indentation curves using the model of Sneddon for a conical indenter. Young’s modulus of elasticity was 20.1–131kPa for the human lens capsule, 9.19–117kPa for the cynomolgus lens capsule, and 13.1–62.4kPa for the baboon lens capsule. Young’s modulus increased significantly with age in humans (p=0.03). The age range of the monkey and baboon samples was not sufficient to justify an analysis of age dependence. The capsule elasticity of young humans (<45 years) was not statistically different from that of the monkey and baboon. In humans, there is an increase in lens capsule stiffness at the microscale that could be responsible for an increase in lens capsule bulk stiffness. PMID:21420953

Chairside CAD/CAM materials. Part 1: Measurement of elastic constants and microstructural characterization.

PubMed

Belli, Renan; Wendler, Michael; de Ligny, Dominique; Cicconi, Maria Rita; Petschelt, Anselm; Peterlik, Herwig; Lohbauer, Ulrich

2017-01-01

A deeper understanding of the mechanical behavior of dental restorative materials requires an insight into the materials elastic constants and microstructure. Here we aim to use complementary methodologies to thoroughly characterize chairside CAD/CAM materials and discuss the benefits and limitations of different analytical strategies. Eight commercial CAM/CAM materials, ranging from polycrystalline zirconia (e.max ZirCAD, Ivoclar-Vivadent), reinforced glasses (Vitablocs Mark II, VITA; Empress CAD, Ivoclar-Vivadent) and glass-ceramics (e.max CAD, Ivoclar-Vivadent; Suprinity, VITA; Celtra Duo, Dentsply) to hybrid materials (Enamic, VITA; Lava Ultimate, 3M ESPE) have been selected. Elastic constants were evaluated using three methods: Resonant Ultrasound Spectroscopy (RUS), Resonant Beam Technique (RBT) and Ultrasonic Pulse-Echo (PE). The microstructures were characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Raman Spectroscopy and X-ray Diffraction (XRD). Young's modulus (E), Shear modulus (G), Bulk modulus (B) and Poisson's ratio (ν) were obtained for each material. E and ν reached values ranging from 10.9 (Lava Ultimate) to 201.4 (e.max ZirCAD) and 0.173 (Empress CAD) to 0.47 (Lava Ultimate), respectively. RUS showed to be the most complex and reliable method, while the PE method the easiest to perform but most unreliable. All dynamic methods have shown limitations in measuring the elastic constants of materials showing high damping behavior (hybrid materials). SEM images, Raman spectra and XRD patterns were made available for each material, showing to be complementary tools in the characterization of their crystal phases. Here different methodologies are compared for the measurement of elastic constants and microstructural characterization of CAD/CAM restorative materials. The elastic properties and crystal phases of eight materials are herein fully characterized. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Effect of single-particle magnetostriction on the shear modulus of compliant magnetoactive elastomers.

PubMed

Kalita, Viktor M; Snarskii, Andrei A; Shamonin, Mikhail; Zorinets, Denis

2017-03-01

The influence of an external magnetic field on the static shear strain and the effective shear modulus of a magnetoactive elastomer (MAE) is studied theoretically in the framework of a recently introduced approach to the single-particle magnetostriction mechanism [V. M. Kalita et al., Phys. Rev. E 93, 062503 (2016)10.1103/PhysRevE.93.062503]. The planar problem of magnetostriction in an MAE with magnetically soft inclusions in the form of a thin disk (platelet) having the magnetic anisotropy in the plane of this disk is solved analytically. An external magnetic field acts with torques on magnetic filler particles, creates mechanical stresses in the vicinity of inclusions, induces shear strain, and increases the effective shear modulus of these composite materials. It is shown that the largest effect of the magnetic field on the effective shear modulus should be expected in MAEs with soft elastomer matrices, where the shear modulus of the matrix is less than the magnetic anisotropy constant of inclusions. It is derived that the effective shear modulus is nonlinearly dependent on the external magnetic field and approaches the saturation value in magnetic fields exceeding the field of particle anisotropy. It is shown that model calculations of the effective shear modulus correspond to a phenomenological definition of effective elastic moduli and magnetoelastic coupling constants. The obtained theoretical results compare well with known experimental data. Determination of effective elastic coefficients in MAEs and their dependence on magnetic field is discussed. The concentration dependence of the effective shear modulus at higher filler concentrations has been estimated using the method of Padé approximants, which predicts that both the absolute and relative changes of the magnetic-field-dependent effective shear modulus will significantly increase with the growing concentration of filler particles.

Effect of single-particle magnetostriction on the shear modulus of compliant magnetoactive elastomers

NASA Astrophysics Data System (ADS)

Kalita, Viktor M.; Snarskii, Andrei A.; Shamonin, Mikhail; Zorinets, Denis

2017-03-01

The influence of an external magnetic field on the static shear strain and the effective shear modulus of a magnetoactive elastomer (MAE) is studied theoretically in the framework of a recently introduced approach to the single-particle magnetostriction mechanism [V. M. Kalita et al., Phys. Rev. E 93, 062503 (2016), 10.1103/PhysRevE.93.062503]. The planar problem of magnetostriction in an MAE with magnetically soft inclusions in the form of a thin disk (platelet) having the magnetic anisotropy in the plane of this disk is solved analytically. An external magnetic field acts with torques on magnetic filler particles, creates mechanical stresses in the vicinity of inclusions, induces shear strain, and increases the effective shear modulus of these composite materials. It is shown that the largest effect of the magnetic field on the effective shear modulus should be expected in MAEs with soft elastomer matrices, where the shear modulus of the matrix is less than the magnetic anisotropy constant of inclusions. It is derived that the effective shear modulus is nonlinearly dependent on the external magnetic field and approaches the saturation value in magnetic fields exceeding the field of particle anisotropy. It is shown that model calculations of the effective shear modulus correspond to a phenomenological definition of effective elastic moduli and magnetoelastic coupling constants. The obtained theoretical results compare well with known experimental data. Determination of effective elastic coefficients in MAEs and their dependence on magnetic field is discussed. The concentration dependence of the effective shear modulus at higher filler concentrations has been estimated using the method of Padé approximants, which predicts that both the absolute and relative changes of the magnetic-field-dependent effective shear modulus will significantly increase with the growing concentration of filler particles.

Mechanical properties of human articular disk and its influence on TMJ loading studied with the finite element method.

PubMed

Tanaka, E; Sasaki, A; Tahmina, K; Yamaguchi, K; Mori, Y; Tanne, K

2001-03-01

The present study was designed to investigate the elastic modulus of human temporomandibular joint (TMJ) disk under tension and its influences on TMJ loading. Seven human TMJ disks served as specimens. Continuous tensile stress was applied to each specimen, and the elastic moduli of human TMJ disks were calculated at 2% strain. Furthermore, using a three-dimensional finite element model of the mandible including the TMJ, changes in the TMJ stresses during clenching were evaluated in association of varying elastic moduli of the articular disk determined by the tensile tests. The elastic moduli at 2% strain varied from 27.1 to 65.2 MPa with a mean of 47.1 MPa. A significant correlation was found between the elastic moduli and age (P < 0.01). On the surface of condyle, compressive stress in the anterior area and tensile stress in the posterior area increased when the elastic moduli of the TMJ disk was varied from 25 to 65 MPa. In the TMJ disk, shear stresses in all the areas became larger with greater stiffness. In conclusion, it is shown that the elastic modulus of human TMJ disk is increased with age and that higher stiffness of the disk exerts substantial influences on mechanical loading for the TMJ structures.

First-principles investigations on structural, elastic and mechanical properties of BNxAs1‑x ternary alloys

NASA Astrophysics Data System (ADS)

Zhang, Junqin; Ma, Huihui; Zhao, Bin; Wei, Qun; Yang, Yintang

2018-05-01

A systematic investigation of the structural optimization, elastic and mechanical properties of the BNxAs1‑x ternary alloys are reported in the present work using the density-functional theory with the generalized gradient approximation (GGA) of the exchange-correlation functional. Some of the constants which are used to analyze the properties including elastic constants and modulus, and some parameters describing the elastic anisotropy and Debye temperature are also calculated. Our calculations were performed to evaluate the equilibrium lattice constant and band structure compared with the available theoretical works. On the one hand, our results might be expected to provide a theoretical basis for future study of BNxAs1‑x alloys towards elastic or mechanical properties. On the other hand, we draw a conclusion that BNxAs1‑x alloys show direct bandgap when x equals 0.25, 0.5 or 0.75. We obtained the elastic modulus, Poisson’s ratio and universal anisotropic index which are used to demonstrate the elastic anisotropy of these alloys which is proved according to our calculations. Also, we calculated the Debye temperature to illustrate covalent interactions and obtained the lower limit of the thermal conductivity for further research.

Evaluation of Mechanical Properties of Glass Fiber Posts Subjected to Laser Surface Treatments.

PubMed

Barbosa Siqueira, Carolina; Spadini de Faria, Natália; Raucci-Neto, Walter; Colucci, Vivian; Alves Gomes, Erica

2016-10-01

The aim of this study was to evaluate the influence of laser irradiation on flexural strength, elastic modulus, and surface roughness and morphology of glass fiber posts (GFPs). Laser treatment of GFPs has been introduced to improve its adhesion properties. A total of 40 GFPs were divided into 4 groups according to the irradiation protocol: GC-no irradiation, GYAG-irradiation with erbium:yttrium-aluminum-garnet [Er:YAG], GCR-irradiation with erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG), and GDI-irradiation with diode laser. The GFP roughness and morphology were evaluated through laser confocal microscopy before and after surface treatment. Three-point bending flexural test measured flexural strength and elastic modulus. Data about elastic modulus and flexural strength were subjected to one-way ANOVA and Bonferroni test (p < 0.05). The effect of roughness was evaluated using the linear mixed effects model and Bonferroni test (p < 0.05). Laser treatment changed surface roughness in the groups GCR (p = 0.000) and GDI (p = 0.007). The mean flexural strength in GYAG (995.22 MPa) was similar to that in GC (980.48 MPa) (p = 1.000) but different from that in GCR (746.83 MPa) and that in GDI (691.34 MPa) (p = 0.000). No difference was found between the groups GCR and GDI (p = 0.86). For elastic modulus: GYAG (24.47 GPa) was similar to GC (25.92 GPa) (p = 1.000) but different from GCR (19.88 GPa) (p = 0.002) and GDI (17.20 GPa) (p = 0.000). The different types of lasers, especially Er,Cr:YSGG and 980 ηm diode, influenced the mechanical properties of GFPs.

Effects of habitual loading on patellar tendon mechanical and morphological properties in basketball and volleyball players.

PubMed

Zhang, Z J; Ng, G Y F; Fu, S N

2015-11-01

Tendon mechanical properties are linked to sports performance and tendon-related injuries, such as tendinopathy. Whether habitual loading, such as participation in regular jumping activities, would induce adaptation on tendon mechanical properties remains unclear. Forty healthy subjects (10 sedentary, 15 volleyball players, and 15 basketball players) aged between 18 and 35 years were recruited. Supersonic shearwave imaging was used to measure the shear elastic modulus and thickness and cross-sectional area (CSA) of the proximal patellar tendons of both knees at 30° of flexion. Significant group differences in tendon shear elastic modulus were found among the three groups. In the dominant leg, reduction in tendon shear elastic modulus by 18.9 % (p = 0.018) and 48.7 % (p = 0.000) were observed in the basketball and volleyball players, respectively, when compared with sedentary subjects. In the non-dominant leg, reduction in tendon shear elastic modulus were 27.3 % (p = 0.034) and 47.1 % (p = 0.02) in the basketball and volleyball players, respectively. The athlete groups were found to have larger CSA but with similar tendon thickness than sedentary group. The CSA were larger by 24-29 % and by 22-24 % in the basketball players and volleyball players, for the dominant and non-dominant legs, respectively (all p < 0.05). Age and body mass are related to tendon stiffness and CSA, particularly in the sedentary subjects. The proximal patellar tendon can undergo substantial adaptation on tendon mechanical and morphological properties when exposed in jumping sports. Intrinsic factors such as age and body mass could influence tendon properties.

Effects of Medium Temperature and Industrial By-Products on the Key Hardened Properties of High Performance Concrete.

PubMed

Safiuddin, Md; Raman, Sudharshan N; Zain, Muhammad Fauzi Mohd

2015-12-10

The aim of the work reported in this article was to investigate the effects of medium temperature and industrial by-products on the key hardened properties of high performance concrete. Four concrete mixes were prepared based on a water-to-binder ratio of 0.35. Two industrial by-products, silica fume and Class F fly ash, were used separately and together with normal portland cement to produce three concrete mixes in addition to the control mix. The properties of both fresh and hardened concretes were examined in the laboratory. The freshly mixed concrete mixes were tested for slump, slump flow, and V-funnel flow. The hardened concretes were tested for compressive strength and dynamic modulus of elasticity after exposing to 20, 35 and 50 °C. In addition, the initial surface absorption and the rate of moisture movement into the concretes were determined at 20 °C. The performance of the concretes in the fresh state was excellent due to their superior deformability and good segregation resistance. In their hardened state, the highest levels of compressive strength and dynamic modulus of elasticity were produced by silica fume concrete. In addition, silica fume concrete showed the lowest level of initial surface absorption and the lowest rate of moisture movement into the interior of concrete. In comparison, the compressive strength, dynamic modulus of elasticity, initial surface absorption, and moisture movement rate of silica fume-fly ash concrete were close to those of silica fume concrete. Moreover, all concretes provided relatively low compressive strength and dynamic modulus of elasticity when they were exposed to 50 °C. However, the effect of increased temperature was less detrimental for silica fume and silica fume-fly ash concretes in comparison with the control concrete.

T1ρ Dispersion in Articular Cartilage

PubMed Central

Besier, Thor F.; Pauly, John M.; Smith, R. Lane; Delp, Scott L.; Beaupre, Gary S.; Gold, Garry E.

2015-01-01

Objective This study assessed T1ρ relaxation dispersion, measured by magnetic resonance imaging (MRI), as a tool to noninvasively evaluate cartilage material and biochemical properties. The specific objective was to answer two questions: (1) does cartilage initial elastic modulus (E0) correlate with T1ρ dispersion effects and (2) does collagen or proteoglycan content correlate with T1ρ dispersion effects? Design Cadaveric patellae with and without visible cartilage damage on conventional MR were included. T2 and T1ρ relaxation times at 500 and 1000 Hz spin-lock field amplitudes were measured. We estimated T1ρ dispersion effects by measuring T1ρ relaxation time at 500 and 1000 Hz and T2 relaxation time and using a new tool, the ratio T1ρ/T2. Cartilage initial elastic modulus, E0, was measured from initial response of mechanical indentation creep tests. Collagen and proteoglycan contents were measured at the indentation test sites; proteoglycan content was measured by their covalently linked sulfated glycosaminoglycans (sGAG). Pearson correlation coefficients were determined, taking into account the clustering of multiple samples within a single patella specimen. Results Cartilage initial elastic modulus, E0, increased with decreasing values of T1ρ/T2 measurements at both 500 Hz (P = 0.034) and 1000 Hz (P = 0.022). 1/T1ρ relaxation time (500 Hz) increased with increasing sGAG content (P = 0.041). Conclusions T1ρ/T2 ratio, a new tool, and cartilage initial elastic modulus are both measures of water–protein interactions, are dependent on the cartilage structure, and were correlated in this study. PMID:26069714

Progression of Carotid Arterial Stiffness With Treatment of Hypertension Over 10 Years: The Multi-Ethnic Study of Atherosclerosis.

PubMed

Gepner, Adam D; Tedla, Yacob; Colangelo, Laura A; Tattersall, Matthew C; Korcarz, Claudia E; Kaufman, Joel D; Liu, Kiang; Burke, Gregory L; Shea, Steven; Greenland, Philip; Stein, James H

2017-01-01

Associations with antihypertensive medication classes and progression of arterial stiffness have not been studied in a prospective multiethnic cohort. All participants had hypertension at baseline, defined as blood pressure ≥140/90 mm Hg or use of antihypertensive medications. Medication use and blood pressure were assessed at 5 time points. Young's elastic modulus and distensibility coefficient of the right common carotid artery were obtained by ultrasound at baseline and after a mean (SD) follow-up period of 9.4 (0.5) years. Associations with changes in Young's elastic modulus and distensibility coefficient, baseline antihypertensive medication use, number of visits each medication class was reported, and blood pressure control (<140/90 mm Hg) were assessed using multiple linear regression models. At baseline, mean age of participants (n=1206) was 63.2 (9.0) years (55% female; 35% African American, 19% Hispanic, 12% Chinese). Mean systolic blood pressure was 136.5 (20.6) mm Hg. Greater progression of arterial stiffness was associated with older age, African American ethnicity, and baseline calcium channel blocker use. There were no other associations between changes in Young's elastic modulus or distensibility coefficient and use of other medication classes (all P>0.4). Achieving blood pressure control (<140/90 mm Hg) at all visits was associated with slower progression of arterial stiffness (Young's elastic modulus: β=-790.1 mm Hg, P=0.01; distensibility coefficient: β=7.34×10 - 4 mm Hg - 1 , P=0.001). Blood pressure control, rather than use of any particular antihypertensive medication class, was associated most strongly with slowing arterial stiffness progression. Over nearly a decade of follow-up, no consistent associations between any specific antihypertensive medication class and progressive carotid arterial stiffening were identified. © 2016 American Heart Association, Inc.

Numerical investigation of the mechanical properties of the additive manufactured bone scaffolds fabricated by FDM: The effect of layer penetration and post-heating.

PubMed

Naghieh, S; Karamooz Ravari, M R; Badrossamay, M; Foroozmehr, E; Kadkhodaei, M

2016-06-01

In recent years, thanks to additive manufacturing technology, researchers have gone towards the optimization of bone scaffolds for the bone reconstruction. Bone scaffolds should have appropriate biological as well as mechanical properties in order to play a decisive role in bone healing. Since the fabrication of scaffolds is time consuming and expensive, numerical methods are often utilized to simulate their mechanical properties in order to find a nearly optimum one. Finite element analysis is one of the most common numerical methods that is used in this regard. In this paper, a parametric finite element model is developed to assess the effects of layers penetration׳s effect on inter-layer adhesion, which is reflected on the mechanical properties of bone scaffolds. To be able to validate this model, some compression test specimens as well as bone scaffolds are fabricated with biocompatible and biodegradable poly lactic acid using fused deposition modeling. All these specimens are tested in compression and their elastic modulus is obtained. Using the material parameters of the compression test specimens, the finite element analysis of the bone scaffold is performed. The obtained elastic modulus is compared with experiment indicating a good agreement. Accordingly, the proposed finite element model is able to predict the mechanical behavior of fabricated bone scaffolds accurately. In addition, the effect of post-heating of bone scaffolds on their elastic modulus is investigated. The results demonstrate that the numerically predicted elastic modulus of scaffold is closer to experimental outcomes in comparison with as-built samples. Copyright © 2016 Elsevier Ltd. All rights reserved.

Modeling the Elastic Modulus of 2D Woven CVI SiC Composites

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.

2006-01-01

The use of fiber, interphase, CVI SiC minicomposites as structural elements for 2D-woven SiC fiber reinforced chemically vapor infiltrated (CVI) SiC matrix composites is demonstrated to be a viable approach to model the elastic modulus of these composite systems when tensile loaded in an orthogonal direction. The 0deg (loading direction) and 90deg (perpendicular to loading direction) oriented minicomposites as well as the open porosity and excess SiC associated with CVI SiC composites were all modeled as parallel elements using simple Rule of Mixtures techniques. Excellent agreement for a variety of 2D woven Hi-Nicalon(TradeMark) fiber-reinforced and Sylramic-iBN reinforced CVI SiC matrix composites that differed in numbers of plies, constituent content, thickness, density, and number of woven tows in either direction (i.e, balanced weaves versus unbalanced weaves) was achieved. It was found that elastic modulus was not only dependent on constituent content, but also the degree to which 90deg minicomposites carried load. This depended on the degree of interaction between 90deg and 0deg minicomposites which was quantified to some extent by composite density. The relationships developed here for elastic modulus only necessitated the knowledge of the fractional contents of fiber, interphase and CVI SiC as well as the tow size and shape. It was concluded that such relationships are fairly robust for orthogonally loaded 2D woven CVI SiC composite system and can be implemented by ceramic matrix composite component modelers and designers for modeling the local stiffness in simple or complex parts fabricated with variable constituent contents.

Effects of Medium Temperature and Industrial By-Products on the Key Hardened Properties of High Performance Concrete

PubMed Central

Safiuddin, Md.; Raman, Sudharshan N.; Zain, Muhammad Fauzi Mohd.

2015-01-01

The aim of the work reported in this article was to investigate the effects of medium temperature and industrial by-products on the key hardened properties of high performance concrete. Four concrete mixes were prepared based on a water-to-binder ratio of 0.35. Two industrial by-products, silica fume and Class F fly ash, were used separately and together with normal portland cement to produce three concrete mixes in addition to the control mix. The properties of both fresh and hardened concretes were examined in the laboratory. The freshly mixed concrete mixes were tested for slump, slump flow, and V-funnel flow. The hardened concretes were tested for compressive strength and dynamic modulus of elasticity after exposing to 20, 35 and 50 °C. In addition, the initial surface absorption and the rate of moisture movement into the concretes were determined at 20 °C. The performance of the concretes in the fresh state was excellent due to their superior deformability and good segregation resistance. In their hardened state, the highest levels of compressive strength and dynamic modulus of elasticity were produced by silica fume concrete. In addition, silica fume concrete showed the lowest level of initial surface absorption and the lowest rate of moisture movement into the interior of concrete. In comparison, the compressive strength, dynamic modulus of elasticity, initial surface absorption, and moisture movement rate of silica fume-fly ash concrete were close to those of silica fume concrete. Moreover, all concretes provided relatively low compressive strength and dynamic modulus of elasticity when they were exposed to 50 °C. However, the effect of increased temperature was less detrimental for silica fume and silica fume-fly ash concretes in comparison with the control concrete. PMID:28793732

Biomechanical properties of the mid-shaft femur in middle-aged hypophysectomized rats as assessed by bending test.

PubMed

Bozzini, Clarisa; Picasso, Emilio O; Champin, Graciela M; Alippi, Rosa María; Bozzini, Carlos E

2012-10-01

Both stiffness and strength of bones are thought to be controlled by the "bone mechanostat". Its natural stimuli would be the strains of bone tissue (sensed by osteocytes) that are induced by both gravitational forces (body weight) and contraction of regional muscles. Body weight and muscle mass increase with age. Biomechanical performance of load-bearing bones must adapt to these growth-induced changes. Hypophysectomy in the rat slows the rate of body growth. With time, a great difference in body size is established between a hypophysectomized rat and its age-matched control, which makes it difficult to establish the real effect of pituitary ablation on bone biomechanics. The purpose of the present investigation was to compare mid-shaft femoral mechanical properties between hypophysectomized and weight-matched normal rats, which will show similar sizes and thus will be exposed to similar habitual loads. Two groups of 10 female rats each (H and C) were established. H rats were 12-month-old that had been hypophysectomized 11 months before. C rats were 2.5-month-old normals. Right femur mechanical properties were tested in 3-point bending. Structural (load-bearing capacity and stiffness), geometric (cross-sectional area, cortical sectional area, and moment of inertia), and material (modulus of elasticity and maximum elastic stress) properties were evaluated. The left femur was ashed for calcium content. Comparisons between parameters were performed by the Student's t test. Average body weight, body length, femur weight, femur length, and gastrocnemius weight were not significantly different between H and C rats. Calcium content in ashes was significantly higher in H than in C rats. Cross-sectional area, medullary area, and cross-sectional moment of inertia were higher in C rats, whereas cortical area did not differ between groups. Structural properties (diaphyseal stiffness, elastic limit, and load at fracture) were about four times higher in hypophysectomized rats, as were the bone material stiffness or Young's modulus and the maximal elastic stress (about 7×). The femur obtained from a middle-aged H rat was stronger and stiffer than the femur obtained from a young-adult C rat, both specimens showing similar size and bone mass and almost equal geometric properties. The higher than normal structural properties shown by the hypophysectomized femur were entirely due to changes in the intrinsic properties of the bone; it was thus stronger at the tissue level. The change of the femoral bone tissue was associated with a high mineral content and an unusual high modulus of elasticity and was probably due to a diminished bone and collagen turnover.

Elasticity of Pargasite Amphibole: A Hydrous Phase at Mid Lithospheric Discontinuity

NASA Astrophysics Data System (ADS)

Peng, Y.; Mookherjee, M.

2017-12-01

Mid Lithospheric Discontinuity (MLD) is characterized by a low shear wave velocity ( 3 to 10 %). In cratons, the depth of MLD varies between 80 and 100 km. The reduction of the shear wave velocity at MLD is similar to what is observed in the lithosphere-asthenosphere boundary (LAB). Such low velocity at MLD could be caused by partial melting, temperature induced grain boundary sliding, changes in the elastic anisotropy, and/or metasomatism which may lead to the formation of hydrous phases including mica and amphibole. Thus, it is clear that in order to assess the role of metasomatism at MLD, we need better constraints on the elasticity of hydrous phases. However, such elasticity data are scarce. In this study, we explore elasticity of pargasite amphibole [NaCa2(Mg4Al)(Si6Al2)O22(OH)2] using density functional theory (DFT) with local density approximation (LDA) and generalized gradient approximation (GGA). We find that the pressure-volume results can be adequately described by a finite strain equation with the bulk modulus, K0 being 102 and 85 GPa for LDA and GGA respectively. We also determined the full elastic constant tensor (Cij) using the finite difference method. The bulk modulus, K0 determined from the full elastic constant tensor is 104 GPa for LDA and 87 GPa for GGA. The shear modulus, G0 determined from the full elastic constant tensor is 64 GPa for LDA and 58 GPa for GGA. The bulk and shear moduli predicted with LDA are 5 and 1 % stiffer than the recent results [1]. In contrast, the bulk and shear moduli predicted with GGA are 12 and 10 % softer compared to the recent results [1]. The full elastic constant tensor for pargasite shows significant anisotropy. For instance, LDA predicts compressional (AVP) and shear (AVS) wave anisotropy of 22 and 20 % respectively. At higher pressure, elastic moduli stiffen. However, temperature is likely to have an opposite effect on the elasticity and this remains largely unknown for pargasite. Compared to the major mantle minerals, pargasite has softer elastic constants and significant anisotropy and may explain the reduction in shear wave velocity at MLD. Reference: [1] Brown, J. M., Abramson, E. H.,2016, Phys. Earth Planet. Int., 261, 161-171. Acknowledgement: This work is supported by US NSF award EAR 1639552.

Cervical Rotatory Manipulation Decreases Uniaxial Tensile Properties of Rabbit Atherosclerotic Internal Carotid Artery

PubMed Central

Qi, Ji; Zhang, Lei; Chen, Chao; Mondal, Shubhro; Ping, Kaike; Chen, Yili

2017-01-01

Objective. To investigate the effects of one of the Chinese massage therapies, cervical rotatory manipulation (CRM), on uniaxial tensile properties of rabbit atherosclerotic internal carotid artery (ICA). Methods. 40 male purebred New Zealand white rabbits were randomly divided into CRM-Model group, Non-CRM-Model group, CRM-Normal group, and Non-CRM-Normal group. After modeling (atherosclerotic model) and intervention (CRM or Non-CRM), uniaxial tensile tests were performed on the ICAs to assess the differences in tensile mechanical properties between the four groups. Results. Both CRM and modeling were the main effects affecting physiological elastic modulus (PEM) of ICA. PEM in CRM-Model group was 1.81 times as much as Non-CRM-Model group, while the value in CRM-Model group was 1.34 times as much as CRM-Normal group. Maximum elastic modulus in CRM-Model group was 1.80 times as much as CRM-Normal group. Max strains in CRM-Model group and Non-CRM-Model group were 30.98% and 28.71% lower than CRM-Normal group and Non-CRM-Normal group, respectively. However, whether treated with CRM or not, the uniaxial tensile properties of healthy ICAs were not statistically different. Conclusion. CRM may decrease the uniaxial tensile properties of rabbit arteriosclerotic ICA, but with no effect on normal group. The study will aid in the meaningful explanation of the controversy about the harmfulness of CRM and the suitable population of CRM. PMID:28303160

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

PubMed

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

2017-07-01

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

Control of mechanical response of freestanding PbZr0.52Ti0.48O3 films through texture

NASA Astrophysics Data System (ADS)

Das, Debashish; Sanchez, Luz; Martin, Joel; Power, Brian; Isaacson, Steven; Polcawich, Ronald G.; Chasiotis, Ioannis

2016-09-01

The texture of piezoelectric lead zirconate titanate (PZT) thin films plays a key role in their mechanical response and linearity in the stress vs. strain behavior. The open circuit mechanical properties of PZT films with controlled texture varying from 100% (001) to 100% (111) were quantified with the aid of direct strain measurements from freestanding thin film specimens. The texture was tuned using a highly {111}-textured Pt substrate and excess-Pb in the PbTiO3 seed layer. The mechanical and ferroelastic properties of 500 nm thick PZT (52/48) films were found to be strongly dependent on grain orientation: the lowest elastic modulus of 90 ± 2 GPa corresponded to pure (001) texture, and its value increased linearly with the percentage of (111) texture reaching 122 ± 3 GPa for pure (111) texture. These elastic modulus values were between those computed for transversely isotropic textured PZT films by using the soft and hard bulk PZT compliance coefficients. Pure (001) texture exhibited maximum non-linearity and ferroelastic domain switching, contrary to pure (111) texture that exhibited more linearity and the least amount of switching. A micromechanics model was employed to calculate the strain due to domain switching. The model fitted well the non-linearities in the experimental stress-strain curves of (001) and (111) textured PZT films, predicting 17% and 10% of switched 90° domains that initially were favorably aligned with the applied stress in (001) and (111) textured PZT films, respectively.

Determination of the axial and circumferential mechanical properties of the skin tissue using experimental testing and constitutive modeling.

PubMed

Karimi, Alireza; Navidbakhsh, Mahdi; Haghighatnama, Maedeh; Haghi, Afsaneh Motevalli

2015-01-01

The skin, being a multi-layered material, is responsible for protecting the human body from the mechanical, bacterial, and viral insults. The skin tissue may display different mechanical properties according to the anatomical locations of a body. However, these mechanical properties in different anatomical regions and at different loading directions (axial and circumferential) of the mice body to date have not been determined. In this study, the axial and circumferential loads were imposed on the mice skin samples. The elastic modulus and maximum stress of the skin tissues were measured before the failure occurred. The nonlinear mechanical behavior of the skin tissues was also computationally investigated through a suitable constitutive equation. Hyperelastic material model was calibrated using the experimental data. Regardless of the anatomic locations of the mice body, the results revealed significantly different mechanical properties in the axial and circumferential directions and, consequently, the mice skin tissue behaves like a pure anisotropic material. The highest elastic modulus was observed in the back skin under the circumferential direction (6.67 MPa), while the lowest one was seen in the abdomen skin under circumferential loading (0.80 MPa). The Ogden material model was narrowly captured the nonlinear mechanical response of the skin at different loading directions. The results help to understand the isotropic/anisotropic mechanical behavior of the skin tissue at different anatomical locations. They also have implications for a diversity of disciplines, i.e., dermatology, cosmetics industry, clinical decision making, and clinical intervention.

Uniaxial compressive behavior of micro-pillars of dental enamel characterized in multiple directions.

PubMed

Yilmaz, Ezgi D; Jelitto, Hans; Schneider, Gerold A

2015-04-01

In this work, the compressive elastic modulus and failure strength values of bovine enamel at the first hierarchical level formed by hydroxyapatite (HA) nanofibers and organic matter are identified in longitudinal, transverse and oblique direction with the uniaxial micro-compression method. The elastic modulus values (∼70 GPa) measured here are within the range of results reported in the literature but these values were found surprisingly uniform in all orientations as opposed to the previous nanoindentation findings revealing anisotropic elastic properties in enamel. Failure strengths were recorded up to ∼1.7 GPa and different failure modes (such as shear, microbuckling, fiber fracture) governed by the orientation of the HA nanofibers were visualized. Structural irregularities leading to mineral contacts between the nanofibers are postulated as the main reason for the high compressive strength and direction-independent elastic behavior on enamels first hierarchical level. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Prediction of Mechanical Properties of Polymers With Various Force Fields

NASA Technical Reports Server (NTRS)

Odegard, Gregory M.; Clancy, Thomas C.; Gates, Thomas S.

2005-01-01

The effect of force field type on the predicted elastic properties of a polyimide is examined using a multiscale modeling technique. Molecular Dynamics simulations are used to predict the atomic structure and elastic properties of the polymer by subjecting a representative volume element of the material to bulk and shear finite deformations. The elastic properties of the polyimide are determined using three force fields: AMBER, OPLS-AA, and MM3. The predicted values of Young s modulus and shear modulus of the polyimide are compared with experimental values. The results indicate that the mechanical properties of the polyimide predicted with the OPLS-AA force field most closely matched those from experiment. The results also indicate that while the complexity of the force field does not have a significant effect on the accuracy of predicted properties, small differences in the force constants and the functional form of individual terms in the force fields determine the accuracy of the force field in predicting the elastic properties of the polyimide.

Measurement at low strain rates of the elastic properties of dental polymeric materials.

PubMed

Chabrier, F; Lloyd, C H; Scrimgeour, S N

1999-01-01

To evaluate a simple static test (i.e. a slow strain rate test) designed to measure Young's modulus and the bulk modulus of polymeric materials (The NOL Test). Though it is a 'mature' test as yet it has never been applied to dental materials. A small cylindrical specimen is contained in a close-fitting steel constraining ring and compressive force applied to the ends by steel pistons. The initial (unconstrained) deformation is controlled by Young's modulus. Lateral spreading leads to constraint from the ring and subsequent deformation is controlled by the bulk modulus. A range of dental materials and reference polymers were selected and both moduli measured. From these data Poisson's ratios were calculated. The test proved be a simple reliable method for obtaining values for these properties. For composite the value of Young's modulus was lower, bulk modulus relatively similar and Poisson's ratio higher than that obtained from high strain rate techniques (as expected for a strain rate sensitive material). This test does fulfil a requirement for a simple test to define fully the elastic properties of dental polymeric materials. Measurements are made at the strain rates used in conventional static tests and values reflect this test condition. The higher values obtained for Poisson's ratio at this slow strain rate has implications for FEA, in that analysis is concerned with static or slow rate loading situations.

Ab Initio Study of the Electronic Structure, Elastic Properties, Magnetic Feature and Thermodynamic Properties of the Ba2NiMoO6 Material

NASA Astrophysics Data System (ADS)

Deluque Toro, C. E.; Mosquera Polo, A. S.; Gil Rebaza, A. V.; Landínez Téllez, D. A.; Roa-Rojas, J.

2018-04-01

We report first-principles calculations of the elastic properties, electronic structure and magnetic behavior performed over the Ba2NiMoO6 double perovskite. Calculations are carried out through the full-potential linear augmented plane-wave method within the framework of the Density Functional Theory (DFT) with exchange and correlation effects in the Generalized Gradient and Local Density Approximations, including spin polarization. The elastic properties calculated are bulk modulus (B), the elastic constants (C 11, C 12 and C 44), the Zener anisotropy factor (A), the isotropic shear modulus (G), the Young modulus (Y) and the Poisson ratio (υ). Structural parameters, total energies and cohesive properties of the perovskite are studied by means of minimization of internal parameters with the Murnaghan equation, where the structural parameters are in good agreement with experimental data. Furthermore, we have explored different antiferromagnetic configurations in order to describe the magnetic ground state of this compound. The pressure and temperature dependence of specific heat, thermal expansion coefficient, Debye temperature and Grüneisen parameter were calculated by DFT from the state equation using the quasi-harmonic model of Debye. A specific heat behavior C V ≈ C P was found at temperatures below T = 400 K, with Dulong-Petit limit values, which is higher than those, reported for simple perovskites.

Quantitative Nanomechanical Properties of Multilayer Films Made of Polysaccharides through Spray Assisted Layer-by-Layer Assembly.

PubMed

Criado, Miryam; Rebollar, Esther; Nogales, Aurora; Ezquerra, Tiberio A; Boulmedais, Fouzia; Mijangos, Carmen; Hernández, Rebeca

2017-01-09

Nanomechanical properties of alginate/chitosan (Alg/Chi) multilayer films, obtained through spray assisted layer-by-layer assembly, were studied by means of PeakForce quantitative nanomechanical mapping atomic force microscopy (PF-QNM AFM). Prepared at two different alginate concentrations (1.0 and 2.5 mg/mL) and a fixed chitosan concentration (1.0 mg/mL), Alg/Chi films have an exponential growth in thickness with a transition to a linear growth toward a plateau by increasing the number of deposited bilayers. Height, elastic modulus, deformation, and adhesion maps were simultaneously recorded depending on the number of deposited bilayers. The elastic modulus of Alg/Chi films was found to be related to the mechanism of growth in contrast to the adhesion and deformation. A comparison of the nanomechanical properties obtained for non-cross-linked and thermally cross-linked Alg/Chi films revealed an increase of the elastic modulus after cross-linking regardless alginate concentration. The incorporation of iron oxide nanoparticles (NPs), during the spray preparation of the films, gave rise to nanocomposite Alg/Chi films with increased elastic moduli with the number of incorporated NPs layers. Deformation maps of the films strongly suggested the presence of empty spaces associated with the method of preparation. Finally, adhesion measurements point out to a significant role of NPs on the increase of the adhesion values found for nanocomposite films.

[Comparative study of polymerization shrinkage and related properties of flowable composites and an unfilled resin].

PubMed

Bukovinszky, Katalin; Molnár, Lilla; Bakó, József; Szalóki, Melinda; Hegedus, Csaba

2014-03-01

The polymerization shrinkage and shrinkage stress of dental composites are in the center of the interest of researchers and manufacturers. It is a great challenge to minimize this important property as low as possible. Many factors are related and are in complicated correlation with each other affecting the polymerization shrinkage. Polymerization shrinkage stress degree of conversion and elasticity has high importance from this aspect. Our aim was to study the polymerization shrinkage and related properties (modulus of elasticity, degree of conversion, shrinkage stress) of three flowable composite (Charisma Opal Flow, SDR, Filtek Ultimate) and an unfilled composite resin. Modulus of elasticity was measured using three point flexure tests on universal testing machine. The polymerization shrinkage stress was determined using bonded-disc technique. The degree of conversion measurements were performed by FT-IR spectroscopy. And the volumetric shrinkage was investigated using Archimedes principle and was measured on analytical balance with special additional equipment. The unfilled resin generally showed higher shrinkage (8,26%), shrinkage stress (0,8 MPa) and degree of conversion (38%), and presented the lowest modulus of elasticity (3047,02MPa). Highest values of unfilled resin correspond to the literature. The lack of fillers enlarges the shrinkage, and the shrinkage stress, but gives the higher flexibility and higher degree of conversion. Further investigations needs to be done to understand and reveal the differences between the composites.

Microcomputed tomography and microfinite element modeling for evaluating polymer scaffolds architecture and their mechanical properties.

PubMed

Alberich-Bayarri, Angel; Moratal, David; Ivirico, Jorge L Escobar; Rodríguez Hernández, José C; Vallés-Lluch, Ana; Martí-Bonmatí, Luis; Estellés, Jorge Más; Mano, Joao F; Pradas, Manuel Monleón; Ribelles, José L Gómez; Salmerón-Sánchez, Manuel

2009-10-01

Detailed knowledge of the porous architecture of synthetic scaffolds for tissue engineering, their mechanical properties, and their interrelationship was obtained in a nondestructive manner. Image analysis of microcomputed tomography (microCT) sections of different scaffolds was done. The three-dimensional (3D) reconstruction of the scaffold allows one to quantify scaffold porosity, including pore size, pore distribution, and struts' thickness. The porous morphology and porosity as calculated from microCT by image analysis agrees with that obtained experimentally by scanning electron microscopy and physically measured porosity, respectively. Furthermore, the mechanical properties of the scaffold were evaluated by making use of finite element modeling (FEM) in which the compression stress-strain test is simulated on the 3D structure reconstructed from the microCT sections. Elastic modulus as calculated from FEM is in agreement with those obtained from the stress-strain experimental test. The method was applied on qualitatively different porous structures (interconnected channels and spheres) with different chemical compositions (that lead to different elastic modulus of the base material) suitable for tissue regeneration. The elastic properties of the constructs are explained on the basis of the FEM model that supports the main mechanical conclusion of the experimental results: the elastic modulus does not depend on the geometric characteristics of the pore (pore size, interconnection throat size) but only on the total porosity of the scaffold. (c) 2009 Wiley Periodicals, Inc.

Geophysical Signatures to Monitor Fluids and Mineralization for CO2 Sequestration in Basalts

NASA Astrophysics Data System (ADS)

Otheim, L. T.; Adam, L.; Van Wijk, K.; Batzle, M. L.; Mcling, T. L.; Podgorney, R. K.

2011-12-01

Carbon dioxide sequestration in large reservoirs can reduce emissions of this green house gas into the atmosphere. Basalts are promising host rocks due to their volumetric extend, worldwide distribution, and recent observations that CO2-water mixtures react with basalt minerals to precipitate as carbonate minerals, trapping the CO2. The chemical reaction between carbonic acid and minerals rich in calcium, magnesium and iron precipitates carbonates in the pore space. This process would increase the elastic modulus and velocity of the rock. At the same time, the higher compressibility of CO2 over water changes the elastic properties of the rock, decreasing the saturated rock bulk modulus and the P-wave velocity. Reservoirs where the rock properties change as a result of fluid or pressure changes are commonly monitored with seismic methods. Here we present experiments to study the feasibility of monitoring CO2 migration in a reservoir and CO2-rock reactions for a sequestration scenario in basalts. Our goal is to measure the rock's elastic response to mineralization with non-contacting ultrasonic lasers, and the effect of fluid substitution at reservoir conditions at seismic and ultrasonic frequencies. For the fluid substitution experiment we observe changes in the P- and S-wave velocities when saturating the sample with super-critical (sc) CO2, CO2-water mixtures and water alone for different pore and confining pressures. The bulk modulus of the rock is significantly dependent on frequency in the 2~to 106~Hz range, for CO2-water mixtures and pure water saturations. Dry and pure CO2 (sc or gas) do not show a frequency dependence on the modulus. Moreover, the shear wave modulus is not dispersive for either fluid. The frequency dependence of the elastic parameters is related to the attenuation (1/Q) of the rock. We will show the correlation between frequency dependent moduli and attenuation data for the different elastic moduli of the rocks. Three other basalt samples were stored in a pressure chamber with a sc CO2-water solution to study the effect of mineralization on the elastic properties of the rock. The rock elastic properties are recorded with non-contacting ultrasonic lasers at room conditions. After 15 weeks the first post-mineralization scan showed differences in the rock velocities with respect to the pre-mineralization scan. The analysis is done through coda wave interferometry and direct arrivals. The samples were inserted back into the pressure vessel for continuing mineralization and subsequent scans. Finally, we will discuss the applicability of Gassmann's equation and how the combination of mineralization together with CO2-water mixture affects the velocity of waves in basalt rocks.

Graphite Microstructural Characterization Using Time-Domain and Correlation-Based Ultrasonics

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

Spicer, James

Among techniques that have been used to determine elastic modulus in nuclear graphites, ultrasonic methods have enjoyed wide use and standards using contacting piezoelectric tranducers have been developed to ensure repeatability of these types of measurements. However, the use of couplants and the pressures used to effectively couple transducers to samples can bias measurements and produce results that are not wholly related to the properties of the graphite itself. In this work, we have investigated the use of laser ultrasonic methods for making elastic modulus measurements in nuclear graphites. These methods use laser-based transmitters and receivers to gather data andmore » do not require use of ultrasonic couplants or mechanical contact with the sample. As a result, information directly related to the elastic responses of graphite can be gathered even if the graphite is porous, brittle and compliant. In particular, we have demonstrated the use of laser ultrasonics for the determination of both Young’s modulus and shear modulus in a range of nuclear graphites including those that are being considered for use in future nuclear reactors. These results have been analyzed to assess the contributions of porosity and microcracking to the elastic responses of these graphites. Laser-based methods have also been used to assess the moduli of NBG-18 and IG-110 where samples of each grade were oxidized to produce specific changes in porosity. These data were used to develop new models for the elastic responses of nuclear graphites and these models have been used to infer specific changes in graphite microstructure that occur during oxidation that affect elastic modulus. Specifically, we show how ultrasonic measurements in oxidized graphites are consistent with nano/microscale oxidation processes where basal plane edges react more readily than basal plane surfaces. We have also shown the use of laser-based methods to perform shear-wave birefringence measurements and have shown how these measurements can be used to assess elastic anisotropy in nuclear graphites. Using models developed in this program, ultrasonic data were interpreted to extract orientation distribution coefficients that could be used to represent anisotropy in these materials. This demonstration showed the use of ultrasonic methods to quantify anisotropy and how these methods provide more detailed information than do measurements of thermal expansion – a technique commonly used for assessing anisotropy in nuclear graphites. Finally, we have employed laser-based, ultrasonic-correlation techniques in attempts to quantify aspects of graphite microstructure such as pore size and distribution. Results of these measurements indicate that additional work must be performed to make this ultrasonic approach viable for quantitative microstructural characterization.« less

Relationship between radial compressive modulus of elasticity and shear modulus of wood

Treesearch

Jen Y. Liu; Robert J. Ross

2005-01-01

Wood properties in transverse compression are difficult to determine because of such factors as anatomical complexity, specimen geometry, and loading conditions. The mechanical properties of wood, considered as an anisotropic or orthotropic material, are related by certain tensor transformation rules when the reference coordinate system changes its orientation. In this...

A new mechanism of biopulping : attachment of acid groups on fiber

Treesearch

William R. Kenealy; Chris Hunt; Eric Horn; Carl Houtman

2004-01-01

We analyzed the physical properties of wood chips incubated with Ceriporiopsis subvermispora and cultural parameters of biopulping incubations of Phanerochaete chrysosporium and C. subvermispora. Dynamic mechanical analyses indicated a reduction in the modulus of elasticity (MOE) and loss modulus of spruce during the time where the biopulping energy savings effect...

Effects of silvicultural practice and moisture content level on lobolly pine veneer mechanical properties

Treesearch

Todd F. Shupe; Chung-Yun Hse; Elvin T. Choong; Leslie H. Groom

1998-01-01

Loblolly pine veneer specimens were obtained from five silviculturally different stands. Clear specimens were cut parallel to the grain from full size veneer sheets and tests were done at either air-dry or ovendry conditions to determine differences in bending modulus of rupture (MORb), bending modulus of elasticity (MOEb...

Composites from southern pine juvenile wood. Part 2. Durability and dimensional stability

Treesearch

Anton D. Pugel; Eddie W. Price; Chung-Yun Hse

1990-01-01

Southern pine juvenile and mature wood were processed into three composites: flakeboard, particleboard, and fiberboard. The durability of these composites was assessed by subjecting specimens to an ovendry-vacuumpressure-soak (ODVPS) treatment, and then evaluated for modulus of elasticity, modulus of rupture, and internal bond. Overall, juvenile wood composites had...

Importance of Age on the Dynamic Mechanical Behavior of Intertubular and Peritubular Dentin

PubMed Central

Ryou, Heonjune; Romberg, Elaine; Pashley, David H.; Tay, Franklin R.; Arola, Dwayne

2014-01-01

An experimental evaluation of human coronal dentin was performed using nanoscopic Dynamic Mechanical Analysis (nanoDMA). The primary objectives were to quantify any unique changes in mechanical behavior of intertubular and peritubular dentin with age, and to evaluate the microstructure and mechanical behavior of the mineral deposited within the lumens. Specimens of coronal dentin were evaluated by nanoDMA using single indents and in scanning mode via scanning probe microscopy. Results showed that there were no significant differences in the storage modulus or complex modulus between the two age groups (18–25 versus 54–83 yrs) for either the intertubular or peritubular tissue. However, there were significant differences in the dampening behavior between the young and old dentin, as represented in the loss modulus and tanδ responses. For both the intertubular and peritubular components, the capacity for dampening was significantly lower in the old group. Scanning based nanoDMA showed that the tubules of old dentin exhibit a gradient in elastic behavior, with decrease in elastic modulus from the cuff to the center of tubules filled with newly deposited mineral. PMID:25498296

Electronic Structure, Mechanical and Dynamical Stability of Hexagonal Subcarbides M2C (M = Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt): Ab Initio Calculations

NASA Astrophysics Data System (ADS)

Suetin, D. V.; Shein, I. R.

2018-02-01

Ab initio calculations were used to study the properties of a series of hexagonal (Fe2N-like) subcarbides M2C, where M = Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt, and to calculate their equilibrium structural parameters, electronic properties, phase stability, elastic constants, compression modulus, shear modulus, Young's modulus, compressibility, Pugh's indicator, Poisson ratio, elastic anisotropy indices, and also hardness, Debye temperature, sound velocity, and low-temperature heat capacity. It is found based on these results that all the subcarbides are mechanically stable; however, their formation energies E form are positive with respect to a mixture of d-metal and graphite. In addition, the calculation of the phonon spectra of these subcarbides shows the existence of negative modes, which indicates their dynamical instability. Thus, a successful synthesis of these subcarbides at normal conditions is highly improbable.

Biocompatible low Young's modulus achieved by strong crystallographic elastic anisotropy in Ti-15Mo-5Zr-3Al alloy single crystal.

PubMed

Lee, S-H; Todai, M; Tane, M; Hagihara, K; Nakajima, H; Nakano, T

2012-10-01

The elastic anisotropy of the Ti-15Mo-5Zr-3Al (mass%) β-Ti alloy, an ISO certified biomedical material, was investigated using its single crystal. It was revealed that the Young's modulus exhibited pronounced anisotropy. The Young's modulus was reduced to 44.4GPa along the 〈100〉 direction in the Ti-15Mo-5Zr-3Al single crystal, that is comparable to that of human cortical bones. We determined the strategy that β-Ti alloys with extremely low moduli can be developed by reducing the electron-atom (e/a) ratio in alloys, and by suppressing the formation of the ω-phase at the same time. This new knowledge must lead to the development of "single crystalline β-Ti implant materials" as hard tissue replacements for reducing the stress shielding effect. Copyright © 2012 Elsevier Ltd. All rights reserved.

FP-LAPW study of structural, electronic, elastic, mechanical and thermal properties of AlFe intermetallic

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

Jain, Ekta, E-mail: jainekta05@gmail.com; Pagare, Gitanjali, E-mail: gita-pagare@yahoo.co.in; Sanyal, S. P., E-mail: sps.physicsbu@gmail.com

2016-05-06

The structural, electronic, elastic, mechanical and thermal properties of AlFe intermetallic compound in B{sub 2}-type (CsCl) structure have been investigated using first-principles calculations. The exchange-correlation term was treated within generalized gradient approximation. Ground state properties i.e. lattice constants (a{sub 0}), bulk modulus (B) and first-order pressure derivative of bulk modulus (B’) are presented. The density of states are derived which show the metallic character of present compound. Our results for C{sub 11}, C{sub 12} and C{sub 44} agree well with previous theoretical data. Using Pugh’s criteria (B/G{sub H} < 1.75), brittle character of AlFe is satisfied. In addition shear modulusmore » (G{sub H}), Young’s modulus (E), sound wave velocities and Debye temperature (θ{sub D}) have also been estimated.« less

First-principles predictions of structural, mechanical and electronic properties of βTiNb under high pressure

NASA Astrophysics Data System (ADS)

Wang, Z. P.; Fang, Q. H.; Li, J.; Liu, B.

2018-04-01

Structural, mechanical and electronic properties of βTiNb alloy under high pressure have been investigated based on the density functional theory (DFT). The dependences of dimensionless volume ratio, elastic constants, bulk modulus, Young's modulus, shear modulus, ductile/brittle, anisotropy and Poisson's ratio on applied pressure are all calculated successfully. The results reveal that βTiNb alloy is mechanically stable under pressure below 23.45 GPa, and the pressure-induced phase transformation could occur beyond this critical value. Meanwhile, the applied pressure can effectively promote the mechanical properties of βTiNb alloy, including the resistances to volume change, elastic deformation and shear deformation, as well as the material ductility and metallicity. Furthermore, the calculated electronic structures testify that βTiNb alloy performs the metallicity and the higher pressure reduces the structural stability of unit cell.

Interface test series: An in situ study of factors affecting the containment of hydraulic fractures

NASA Astrophysics Data System (ADS)

Warpinski, N. R.; Finley, S. J.; Vollendorf, W. C.; Obrien, M.; Eshom, E.

1982-02-01

In situ experiments, which are accessible for direct observation by mineback, were conducted to determine the effect that material-property interfaces and in situ stress differences have on hydraulic fracture propagation and the resultant overall geometry. These experiments show conclusively that a difference in elastic modulus at a geologic interface has little or no effect on crack growth and, therefore, is not a feature which would promote containment of fractures within a specified reservoir zone. However, differences in the in situ stress between adjacent layers is shown to have a considerable influence on fracture propagation. Experiments were conducted in a low modulus ash-fall tuff which contained two layers of high minimum principal in situ stress and which was overlain by a formation with at least a factor of 5 increase in elastic modulus. Fractures were observed to terminate in regions of high minimum principal in situ stress in nearly every case.

Temperature Coefficient of the Modulus of Rigidity of Aircraft Instrument Diaphragm and Spring Materials

NASA Technical Reports Server (NTRS)

Brombacher, W G; Melton, E R

1931-01-01

Experimental data are presented on the variation of the modulus of rigidity in the temperature range -20 to +50 degrees C. of a number of metals which are of possible use for elastic elements for aircraft and other instruments. The methods of the torsional pendulum was used to determine the modulus of rigidity and its temperature coefficient for aluminum, duralumin, monel metal, brass, phosphor bronze, coin silver, nickel silver, three high carbon steels, and three alloy steels. It was observed that tensile stress affected the values of the modulus by amounts of 1 per cent or less.

Development of Ti-Nb-Zr alloys with high elastic admissible strain for temporary orthopedic devices.

PubMed

Ozan, Sertan; Lin, Jixing; Li, Yuncang; Ipek, Rasim; Wen, Cuie

2015-07-01

A new series of beta Ti-Nb-Zr (TNZ) alloys with considerable plastic deformation ability during compression test, high elastic admissible strain, and excellent cytocompatibility have been developed for removable bone tissue implant applications. TNZ alloys with nominal compositions of Ti-34Nb-25Zr, Ti-30Nb-32Zr, Ti-28Nb-35.4Zr and Ti-24.8Nb-40.7Zr (wt.% hereafter) were fabricated using the cold-crucible levitation technique, and the effects of alloying element content on their microstructures, mechanical properties (tensile strength, yield strength, compressive yield strength, Young's modulus, elastic energy, toughness, and micro-hardness), and cytocompatibilities were investigated and compared. Microstructural examinations revealed that the TNZ alloys consisted of β phase. The alloy samples displayed excellent ductility with no cracking, or fracturing during compression tests. Their tensile strength, Young's modulus, elongation at rupture, and elastic admissible strain were measured in the ranges of 704-839 MPa, 62-65 GPa, 9.9-14.8% and 1.08-1.31%, respectively. The tensile strength, Young's modulus and elongation at rupture of the Ti-34Nb-25Zr alloy were measured as 839 ± 31.8 MPa, 62 ± 3.6 GPa, and 14.8 ± 1.6%, respectively; this alloy exhibited the elastic admissible strain of approximately 1.31%. Cytocompatibility tests indicated that the cell viability ratios (CVR) of the alloys are greater than those of the control group; thus the TNZ alloys possess excellent cytocompatibility. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Elasticity reconstruction: Beyond the assumption of local homogeneity

NASA Astrophysics Data System (ADS)

Sinkus, Ralph; Daire, Jean-Luc; Van Beers, Bernard E.; Vilgrain, Valerie

2010-07-01

Elasticity imaging is a novel domain which is currently gaining significant interest in the medical field. Most inversion techniques are based on the homogeneity assumption, i.e. the local spatial derivatives of the complex-shear modulus are ignored. This analysis presents an analytic approach in order to overcome this limitation, i.e. first order spatial derivatives of the real-part of the complex-shear modulus are taken into account. Resulting distributions in a gauged breast lesion phantom agree very well with the theoretical expectations. An in-vivo example of a cholangiocarcinoma demonstrates that the new approach provides maps of the viscoelastic properties which agree much better with expectations from anatomy.

Correlation Among the Variant Group, Effective Grain Size, and Elastic Strain Energy During the Phase Transformation in 9Ni Steels

NASA Astrophysics Data System (ADS)

Terasaki, Hidenori; Moriguchi, Koji; Tomio, Yusaku; Yamagishi, Hideki; Morito, Shigekazu

2017-12-01

The effect of carbon content on the density of variant-pair boundaries was investigated in 9Ni steel using an electron backscatter diffraction patterns method. The changes in the density of variant-pair boundaries were correlated with the nondestructive measured values of shear modulus of the austenite phase at the phase transformation point. Furthermore, the effective grain size was correlated with the shear modulus and the density of variant-pair boundaries. These relations are discussed from the viewpoint of self-accommodation of elastic strain energy and the nucleation event in the bainite and martensitic transformations.

Measurement of viscosity and elasticity of lubricants at high pressures

NASA Technical Reports Server (NTRS)

Rein, R. G., Jr.; Charng, T. T.; Sliepcevich, C. M.; Ewbank, W. J.

1975-01-01

The oscillating quartz crystal viscometer has been used to investigate possible viscoelastic behavior in synthetic lubricating fluids and to obtain viscosity-pressure-temperature data for these fluids at temperatures to 300 F and pressures to 40,000 psig. The effect of pressure and temperature on the density of the test fluids was measured concurrently with the viscosity measurements. Viscoelastic behavior of one fluid, di-(2-ethylhexyl) sebacate, was observed over a range of pressures. These data were used to compute the reduced shear elastic (storage) modulus and reduced loss modulus for this fluid at atmospheric pressure and 100 F as functions of reduced frequency.

Shear properties of pultruded fiber reinforced polymer composite materials

NASA Astrophysics Data System (ADS)

Seo, J. H.; Kim, S. H.; Ok, D. M.; An, D. J.; Yoon, S. J.

2018-06-01

This paper focuses on the mechanical properties of PFRP composite materials. Especially, relationship between shear property and the other mechanical properties of PFRP composite materials is investigated through comparison between experimental and theoretical results. The shear property of PFRP composite specimen is calculated from the theoretical equations which were suggested in previous studies. In addition, comparison between the shear property determined by the tensile test and the shear property calculated from theoretical equations is conducted and discussed. It was found that the theoretically predicted shear modulus of elasticity considering contiguity is close to the shear modulus of elasticity obtained by the 45° off-axis tensile test.

Pressure derivatives of elastic moduli of fused quartz to 10 kb

USGS Publications Warehouse

Peselnick, L.; Meister, R.; Wilson, W.H.

1967-01-01

Measurements of the longitudinal and shear moduli were made on fused quartz to 10 kb at 24??5??C. The anomalous behavior of the bulk modulus K at low pressure, ???K ???P 0, at higher pressures. The pressure derivative of the rigidity modulus ???G ???P remains constant and negative for the pressure range covered. A 15-kb hydrostatic pressure vessel is described for use with ultrasonic pulse instrumentation for precise measurements of elastic moduli and density changes with pressure. The placing of the transducer outside the pressure medium, and the use of C-ring pressure seals result in ease of operation and simplicity of design. ?? 1967.

Atomistic modeling of mechanical properties of polycrystalline graphene.

PubMed

Mortazavi, Bohayra; Cuniberti, Gianaurelio

2014-05-30

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

Single-crystal elastic properties of aluminum oxynitride (AlON) from brillouin scattering

DOE PAGES

Satapathy, Sikhanda; Ahart, Muhtar; Dandekar, Dattatraya; ...

2016-01-19

The Brillouin light-scattering technique was used to determine experimentally the three independent elastic constants of cubic aluminum oxynitride at the ambient condition. They are C 11=334.8(±1.8) GPa, C 12=164.4(± 1.2) GPa, and C 44=178.6(± 1.1) GPa. Its bulk modulus is 221.2 GPa. The magnitude of Zener anisotropic ratio is 2.1 similar to other spinels. Here, the anisotropic nature of the material is shown by a large variation in the Young’s modulus and Poisson’s ratio with crystallographic directions. The material was found to be auxetic in certain orientations.

A new generation of high flex life polyurethane urea for polymer heart valve--studies on in vivo biocompatibility and biodurability.

PubMed

Thomas, Vinoy; Jayabalan, Muthu

2009-04-01

Development of new generation high flex life polyurethane urea (HFL18-PU) with appropriate elastic modulus, biocompatibility, blood compatibility, resistant to calcification, and biodurability for the long-term use as cardiac device is still a challenge. This study reports the development of a fully aliphatic, ether-free physically cross-linked and low elastic modulus (6.841 +/- 0.27 MPa) polyurethane urea having in vivo biostability, in vivo biocompatibility and high flex-life (721 +/- 30 million cycles) that can satisfy the requirements for the fabrication of tri-leaflet heart valve. Copyright 2008 Wiley Periodicals, Inc.

Active Vibration Control of Elastic Beam by Means of Shape Memory Alloy Layers

NASA Technical Reports Server (NTRS)

Chen, Q.; Levy, C.

1996-01-01

The mathematical model of a flexible beam covered with shape memory alloy (SMA) layers is presented. The SMA layers are used as actuators, which are capable of changing their elastic modulus and recovery stress, thus changing the natural frequency of, and adjusting the excitation to, the vibrating beam. The frequency factor variation as a function of SMA Young's modulus, SMA layer thickness and beam thickness is discussed. Also control of the beam employing an optimal linear control law is evaluated. The control results indicate how the system reacts to various levels of excitation input through the non-homogeneous recovery shear term of the governing differential equation.

Elastic Modulus and Thermal Conductivity of Thiolene/TiO2 Nanocomposites

PubMed Central

2017-01-01

Metal oxide based polymer nanocomposites find diverse applications as functional materials, and in particular thiol-ene/TiO2 nanocomposites are promising candidates for dental restorative materials. The important mechanical and thermal properties of the nanocomposites, however, are still not well understood. In this study, the elastic modulus and thermal conductivity of thiol-ene/TiO2 nanocomposite thin films with varying weight fractions of TiO2 nanoparticles are investigated by using Brillouin light scattering spectroscopy and 3ω measurements, respectively. As the TiO2 weight fraction increases from 0 to 90%, the effective elastic longitudinal modulus of the films increases from 6.2 to 37.5 GPa, and the effective thermal conductivity from 0.04 to 0.76 W/m K. The former increase could be attributed to the covalent cross-linking of the nanocomposite constituents. The latter one could be ascribed to the addition of high thermal conductivity TiO2 nanoparticles and the formation of possible conductive channels at high TiO2 weight fractions. The linear dependence of the thermal conductivity on the sound velocity, reported for amorphous polymers, is not observed in the present nanocomposite system. PMID:29755637

The stress relaxation of cement clinkers under high temperature

NASA Astrophysics Data System (ADS)

Wang, Xiufang; Bao, Yiwang; Liu, Xiaogen; Qiu, Yan

2015-12-01

The energy consumption of crushing is directly affected by the mechanical properties of cement materials. This research provides a theoretical proof for the mechanism of the stress relaxation of cement clinkers under high temperature. Compression stress relaxation under various high temperatures is discussed using a specially developed load cell, which can measure stress and displacement under high temperatures inside an autoclave. The cell shows that stress relaxation dramatically increases and that the remaining stress rapidly decreases with an increase in temperature. Mechanical experiments are conducted under various temperatures during the cooling process to study the changes in the grinding resistance of the cement clinker with temperature. The effects of high temperature on the load-displacement curve, compressive strength, and elastic modulus of cement clinkers are systematically studied. Results show that the hardening phenomenon of the clinker becomes apparent with a decrease in temperature and that post-peak behaviors manifest characteristics of the transformation from plasticity to brittleness. The elastic modulus and compressive strength of cement clinkers increase with a decrease in temperature. The elastic modulus increases greatly when the temperature is lower than 1000 °C. The compressive strength of clinkers increases by 73.4% when the temperature drops from 1100 to 800 °C.

Strengthening and toughening metallic glasses: The elastic perspectives and opportunities

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

Liu, Z. Q.; Zhang, Z. F., E-mail: zhfzhang@imr.ac.cn

2014-04-28

There exist general conflicts between strength and toughness in crystalline engineering materials, and various strengthening and toughening strategies have been developed from the dislocation motion perspectives. Metallic glasses (MGs) have demonstrated great potentials owing to their unique properties; however, their structural applications are strictly limited. One of the key problems is that the traditional strengthening and toughening strategies and mechanisms are not applicable in MGs due to the absence of dislocations and crystalline microstructures. Here, we show that the strength and toughness, or equivalently the shear modulus and Poisson's ratio, are invariably mutually exclusive in MGs. Accordingly, the MGs canmore » be categorized into four groups with different levels of integrated mechanical properties. It is further revealed that the conflicts originate fundamentally from the atomic bonding structures and the levels of strength-toughness combinations are indeed dominated by the bulk modulus. Moreover, we propose novel strategies for optimizing the mechanical properties of MGs from the elastic perspectives. We emphasize the significance of developing high bulk modulus MGs to achieve simultaneously both high strength and good toughness and highlight the elastic opportunities for strengthening and toughening materials.« less

First-principles calculation on the thermodynamic and elastic properties of precipitations in Al-Cu alloys

NASA Astrophysics Data System (ADS)

Sun, Dongqiang; Wang, Yongxin; Zhang, Xinyi; Zhang, Minyu; Niu, Yanfei

2016-12-01

First-principles calculations based on density functional theory was used to investigate the structural, thermodynamic and elastic properties of precipitations, θ″, θ‧ and θ, in Al-Cu alloys. The values of lattice constants accord with experimental results well. The structural stability of θ is the best, followed by θ‧ and θ″. In addition, due to the highest bulk modulus, shear modulus and Young's modulus, θ possesses the best reinforcement effect in precipitation hardening process considered only from mechanical properties of perfect crystal. According to the values of B/G, Poisson's ratio and C11-C12, θ‧ has the worst ductility, while θ″ has the best ductility, the ductility of θ is in the middle. The ideal tensile strength of θ″, θ‧ and θ calculated along [100] and [001] directions are 20.87 GPa, 23.11 GPa and 24.70 GPa respectively. The analysis of electronic structure suggests that three precipitations all exhibit metallic character, and number of bonding electrons and bonding strength are the nature of different thermodynamic and elastic properties for θ″, θ‧ and θ.

Influence of nanofillers on the thermal and mechanical behavior of DGEBA-based adhesives for bonded-in timber connections

NASA Astrophysics Data System (ADS)

Ahmad, Z.; Ansell, M. P.; Smedley, D.

2006-09-01

Results of an experimental investigation into the thermal behavior and mechanical properties of a room-temperature-cured epoxy adhesive (diglycidyl ether of bisphenol A, DGEBA) cross-linked with polyetheramines and filled with different fillers, namely nanosilica, liquid rubber (CTBN), and clay, are reported. The nanosilica and liquid rubber increased the flexural strength and elastic modulus of the adhesive systems; the addition of clay particles raised the elastic modulus significantly, but embrittled the adhesive. Establishing a correct cure time is very important for bonded-in timber structures, as it will affect the bond strength. A study on the effect of cure time on the flexural strength was carried out, from which it follows that the adhesives should be cured for at least 20 days at room temperature. The damping characteristics and the glass-transition temperature of the adhesives were determined by using a dynamic mechanical thermal analysis. The results showed that the filled adhesives had a higher storage modulus, which was in agreement with the elastic moduli determined from static bending tests. The introduction of the fillers increased its glass-transition temperature considerably.

Response of Arterial Stiffness Four Weeks After Terminating Short-term Aerobic Exercise Training in a Sedentary Lifestyle.

PubMed

Baykara, Murat; Demirel, Adnan; Yavuzatmaca, İhsan; Bilgen, Mehmet

2017-02-01

The purpose of this study was to investigate the response of arterial stiffness in individuals with a sedentary lifestyle at 4 weeks after terminating a 2-week aerobic exercise session. Arterial stiffness was evaluated in 38 participants before starting and after completing a prescribed aerobic exercise program and also at 4 weeks after returning back to their sedentary lifestyle. Parameters regarding arterial compliance, distensibility, wall stress, and the elastic modulus were estimated from the information gained from sonography on the dimensions of carotid and femoral arteries and a sphygmomanometer on the pulse pressure. Primary outcomes included whether short-term aerobic exercise reduced the heart rate, arterial pressure, and intima-media thickness and improved vascular biomechanics in physically inactive but otherwise healthy individuals. The benefits gained in arterial compliance and distensibility deteriorated with termination of exercise, but diastolic wall stress and the elastic modulus improved further. In individuals with sedentary lifestyles, short-term aerobic exercise has strong four-week residual benefits on diastolic wall stress and the elastic modulus, but the effects appear to be negligible on arterial stiffness and distensibility. © 2016 by the American Institute of Ultrasound in Medicine.

Prediction of Indentation Behavior of Superelastic TiNi

NASA Astrophysics Data System (ADS)

Neupane, Rabin; Farhat, Zoheir

2014-09-01

Superelastic TiNi shape memory alloys have been extensively used in various applications. The great interest in TiNi alloys is due to its unique shape memory and superelastic effects, along with its superior wear and dent resistance. Assessment of mechanical properties and dent resistance of superelastic TiNi is commonly performed using indentation techniques. However, the coupling of deformation and reversible martensitic transformation of TiNi under indentation conditions makes the interpretation of results challenging. An attempt is made to enhance current interpretation of indentation data. A load-depth curve is predicted that takes into consideration the reversible martensitic transformation. The predicted curve is in good agreement with experimental results. It is found in this study that the elastic modulus is a function of indentation depth. At shallow depths, the elastic modulus is high due to austenite dominance, while at high depths, the elastic modulus drops as the depth increases due to austenite to martensite transition, i.e., martensite dominance. It is also found that TiNi exhibits superior dent resistance compared to AISI 304 steel. There is two orders of magnitude improvement in dent resistance of TiNi in comparison to AISI 304 steel.

Effect of Salicylate on the Elasticity, Bending Stiffness, and Strength of SOPC Membranes

PubMed Central

Zhou, Yong; Raphael, Robert M.

2005-01-01

Salicylate is a small amphiphilic molecule which has diverse effects on membranes and membrane-mediated processes. We have utilized micropipette aspiration of giant unilamellar vesicles to determine salicylate's effects on lecithin membrane elasticity, bending rigidity, and strength. Salicylate effectively reduces the apparent area compressibility modulus and bending modulus of membranes in a dose-dependent manner at concentrations above 1 mM, but does not greatly alter the actual elastic compressibility modulus at the maximal tested concentration of 10 mM. The effect of salicylate on membrane strength was investigated using dynamic tension spectroscopy, which revealed that salicylate increases the frequency of spontaneous defect formation and lowers the energy barrier for unstable hole formation. The mechanical and dynamic tension experiments are consistent and support a picture in which salicylate disrupts membrane stability by decreasing membrane stiffness and membrane thickness. The tension-dependent partitioning of salicylate was utilized to calculate the molecular volume of salicylate in the membrane. The free energy of transfer for salicylate insertion into the membrane and the corresponding partition coefficient were also estimated, and indicated favorable salicylate-membrane interactions. The mechanical changes induced by salicylate may affect several biological processes, especially those associated with membrane curvature and permeability. PMID:15951377

Effect of modifications in mineralized collagen fibril and extra-fibrillar matrix material properties on submicroscale mechanical behavior of cortical bone.

PubMed

Wang, Yaohui; Ural, Ani

2018-06-01

A key length scale of interest in assessing the fracture resistance of bone is the submicroscale which is composed of mineralized collagen fibrils (MCF) and extra-fibrillar matrix (EFM). Although the processes through which the submicroscale constituents of bone contribute to the fracture resistance in bone have been identified, the extent of the modifications in submicroscale mechanical response due to the changes in individual properties of MCFs and EFM has not been determined. As a result, this study aims to quantify the influence of individual MCF and EFM material property modifications on the mechanical behavior (elastic modulus, ultimate strength, and resistance to failure) of bone at the submicroscale using a novel finite element modeling approach that incorporate 3D networks of MCFs with three different orientations as well as explicit representation of EFM. The models were evaluated under tensile loading in transverse (representing MCF separation) and longitudinal (representing MCF rupture) directions. The results showed that the apparent elastic modulus at the submicroscale under both loading directions for all orientations was only affected by the change in the elastic modulus of MCFs. MCF separation and rupture strengths were mainly dependent on the ultimate strength of EFM and MCFs, respectively, with minimal influence of other material properties. The extent of damage during MCF separation increased with increasing ultimate strength of EFM and decreased with increasing fracture energy of EFM with minimal contribution from elastic modulus of MCFs. For MCF rupture, there was an almost one-to-one linear relationship between the percent change in fracture energy of MCFs and the percent change in the apparent submicroscale fracture energy. The ultimate strength and elastic modulus of MCFs had moderate to limited influence on the MCF rupture fracture energy. The results of this study quantified the extent of changes that may be seen in the energy dissipation processes during MCF rupture and separation relative to the changes in the individual constituents of the tissue. This new knowledge significantly contributes to improving the understanding of how the material property alterations at the submicroscale that can occur due to diseases, age-related changes, and treatments affect the fracture processes at larger length scales. Copyright © 2018 Elsevier Ltd. All rights reserved.

A constrained modulus reconstruction technique for breast cancer assessment.

PubMed

Samani, A; Bishop, J; Plewes, D B

2001-09-01

A reconstruction technique for breast tissue elasticity modulus is described. This technique assumes that the geometry of normal and suspicious tissues is available from a contrast-enhanced magnetic resonance image. Furthermore, it is assumed that the modulus is constant throughout each tissue volume. The technique, which uses quasi-static strain data, is iterative where each iteration involves modulus updating followed by stress calculation. Breast mechanical stimulation is assumed to be done by two compressional rigid plates. As a result, stress is calculated using the finite element method based on the well-controlled boundary conditions of the compression plates. Using the calculated stress and the measured strain, modulus updating is done element-by-element based on Hooke's law. Breast tissue modulus reconstruction using simulated data and phantom modulus reconstruction using experimental data indicate that the technique is robust.

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.

Evaluation of copper, aluminum, and nickel interatomic potentials on predicting the elastic properties

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

Rassoulinejad-Mousavi, Seyed Moein; Mao, Yijin; Zhang, Yuwen, E-mail: zhangyu@missouri.edu

Choice of appropriate force field is one of the main concerns of any atomistic simulation that needs to be seriously considered in order to yield reliable results. Since investigations on the mechanical behavior of materials at micro/nanoscale have been becoming much more widespread, it is necessary to determine an adequate potential which accurately models the interaction of the atoms for desired applications. In this framework, reliability of multiple embedded atom method based interatomic potentials for predicting the elastic properties was investigated. Assessments were carried out for different copper, aluminum, and nickel interatomic potentials at room temperature which is considered asmore » the most applicable case. Examined force fields for the three species were taken from online repositories of National Institute of Standards and Technology, as well as the Sandia National Laboratories, the LAMMPS database. Using molecular dynamic simulations, the three independent elastic constants, C{sub 11}, C{sub 12}, and C{sub 44}, were found for Cu, Al, and Ni cubic single crystals. Voigt-Reuss-Hill approximation was then implemented to convert elastic constants of the single crystals into isotropic polycrystalline elastic moduli including bulk modulus, shear modulus, and Young's modulus as well as Poisson's ratio. Simulation results from massive molecular dynamic were compared with available experimental data in the literature to justify the robustness of each potential for each species. Eventually, accurate interatomic potentials have been recommended for finding each of the elastic properties of the pure species. Exactitude of the elastic properties was found to be sensitive to the choice of the force fields. Those potentials that were fitted for a specific compound may not necessarily work accurately for all the existing pure species. Tabulated results in this paper might be used as a benchmark to increase assurance of using the interatomic potential that was designated for a problem.« less

On the relationships between hardness and the elastic and plastic properties of isotropic power-law hardening materials

NASA Astrophysics Data System (ADS)

Lan, Hongzhi; Venkatesh, T. A.

2014-01-01

A comprehensive understanding of the relationship between the hardness and the elastic and plastic properties for a wide range of materials is obtained by analysing the hardness characteristics (that are predicted by experimentally verified indentation analyses) of over 9000 distinct combinations of material properties that represent isotropic, homogeneous, power-law hardening metallic materials. Finite element analysis has been used to develop the indentation algorithms that provide the relationships between the elastic and plastic properties of the indented material and its indentation hardness. Based on computational analysis and virtual testing, the following observations are made. The hardness (H) of a material tends to increase with an increase in the elastic modulus (E), yield strength (σy) and the strain-hardening exponent (n). Several materials with different combinations of elastic and plastic properties can exhibit identical true hardness (for a particular indenter geometry/apex angle). In general, combinations of materials that exhibit relatively low elastic modulus and high yield strength or strain-hardening exponents and those that exhibit relatively high elastic modulus and low yield strength or strain-hardening exponents exhibit similar hardness properties. Depending on the strain-hardening characteristics of the indented material, (i.e. n = 0 or ?), the ratio H/σy ranges, respectively, from 2.2 to 2.6 or 2 to 20 (for indentations with a cone angle of 70.3°). The materials that have lower σy/E and higher n exhibit higher H/σy ratios. The commonly invoked relationship between hardness and the yield strength, i.e. H ≈ 3σy, is not generally valid or applicable for all power-law hardening materials. The indentation hardness of a power law hardening material can be taken as following the relationship H ≈ (2.1-2.8)σr where σr is the representative stress based on Tabor's representative strain for a wide range of materials.

High Temperature Elastic Properties of Reduced Activation Ferritic-Martensitic (RAFM) Steel Using Impulse Excitation Technique

NASA Astrophysics Data System (ADS)

Tripathy, Haraprasanna; Raju, Subramanian; Hajra, Raj Narayan; Saibaba, Saroja

2018-03-01

The polycrystalline elastic constants of an indigenous variant of 9Cr-1W-based reduced activation ferritic-martensitic (RAFM) steel have been determined as a function of temperature from 298 K to 1323 K (25 °C to 1000 °C), using impulse excitation technique (IET). The three elastic constants namely, Young's modulus E, shear modulus G, and bulk modulus B, exhibited significant softening with increasing temperature, in a pronounced non-linear fashion. In addition, clearly marked discontinuities in their temperature variations are noticed in the region, where ferrite + carbides → austenite phase transformation occurred upon heating. Further, the incidence of austenite → martensite transformation upon cooling has also been marked by a step-like jump in both elastic E and shear moduli G. The martensite start M s and M f finish temperatures estimated from this study are, M s = 652 K (379 °C) and M f =580 K (307 °C). Similarly, the measured ferrite + carbide → austenite transformation onset ( Ac 1) and completion ( Ac 3) temperatures are found to be 1126 K and 1143 K (853 °C and 870 °C), respectively. The Poisson ratio μ exhibited distinct discontinuities at phase transformation temperatures; but however, is found to vary in the range 0.27 to 0.29. The room temperature estimates of E, G, and μ for normalized and tempered microstructure are found to be 219 GPa, 86.65 GPa, and 0.27, respectively. For the metastable austenite phase, the corresponding values are: 197 GPa, 76.5 GPa, and 0.29, respectively. The measured elastic properties as well as their temperature dependencies are found to be in good accord with reported estimates for other 9Cr-based ferritic-martensitic steel grades. Estimates of θ D el , the elastic Debye temperature and γ G, the thermal Grüneisen parameter obtained from measured bulk elastic properties are found to be θ D el = 465 K (192 °C) and γ G = 1.57.

Fabrication of a Nano-ZnO/Polyethylene/Wood-Fiber Composite with Enhanced Microwave Absorption and Photocatalytic Activity via a Facile Hot-Press Method

PubMed Central

Dang, Baokang; Chen, Yipeng; Shen, Xiaoping; Chen, Bo; Sun, Qingfeng; Jin, Chunde

2017-01-01

A polyethylene/wood-fiber composite loaded with nano-ZnO was prepared by a facile hot-press method and was used for the photocatalytic degradation of organic compounds as well as for microwave absorption. ZnO nanoparticles with an average size of 29 nm and polyethylene (PE) powders were dispersed on the wood fibers’ surface through a viscous cationic polyacrylamide (CPAM) solution. The reflection loss (RL) value of the resulting composite was −21 dB, with a thickness of 3.5 mm in the frequency of 17.17 GHz. The PE/ZnO/wood-fiber (PZW) composite exhibited superior photocatalytic activity (84% methyl orange degradation within 300 min) under UV light irradiation. ZnO nanoparticels (NPs) increased the storage modulus of the PZW composite, and the damping factor was transferred to the higher temperature region. The PZW composite exhibited the maximum flexural strength of 58 MPa and a modulus of elasticity (MOE) of 9625 MPa. Meanwhile, it also displayed dimensional stability (thickness swelling value of 9%). PMID:29099777

Effect of property gradients on enamel fracture in human molar teeth.

PubMed

Barani, Amir; Bush, Mark B; Lawn, Brian R

2012-11-01

A model for the fracture of tooth enamel with graded elastic modulus and toughness is constructed using an extended finite element modeling (XFEM) package. The property gradients are taken from literature data on human molars, with maximum in modulus at the outer enamel surface and in toughness at the inner surface. The tooth is modeled as a brittle shell (enamel) and a compliant interior (dentin), with occlusal loading from a hard, flat contact at the cusp. Longitudinal radial (R) and margin (M) cracks are allowed to extend piecewise along the enamel walls under the action of an incrementally increasing applied load. A simple stratagem is deployed in which fictitious temperature profiles generate the requisite property gradients. The resulting XFEM simulations demonstrate that the crack fronts become more segmented as the property gradients become more pronounced, with enhanced propagation at the outer surface and inhibited propagation at the inner. Whereas the growth history of the cracks is profoundly influenced by the gradients, the ultimate critical loads required to attain full fractures are relatively unaffected. Some implications concerning dentistry are considered. Copyright © 2012 Elsevier Ltd. All rights reserved.

Acellularization-Induced Changes in Tensile Properties Are Organ Specific - An In-Vitro Mechanical and Structural Analysis of Porcine Soft Tissues

PubMed Central

Aust, Gabriela; Boldt, Andreas; Fritsch, Sebastian; Keil, Isabel; Koch, Holger; Möbius, Robert; Scheidt, Holger A.; Wagner, Martin F. X.; Hammer, Niels

2016-01-01

Introduction Though xenogeneic acellular scaffolds are frequently used for surgical reconstruction, knowledge of their mechanical properties is lacking. This study compared the mechanical, histological and ultrastructural properties of various native and acellular specimens. Materials and Methods Porcine esophagi, ureters and skin were tested mechanically in a native or acellular condition, focusing on the elastic modulus, ultimate tensile stress and maximum strain. The testing protocol for soft tissues was standardized, including the adaption of the tissue’s water content and partial plastination to minimize material slippage as well as templates for normed sample dimensions and precise cross-section measurements. The native and acellular tissues were compared at the microscopic and ultrastructural level with a focus on type I collagens. Results Increased elastic modulus and ultimate tensile stress values were quantified in acellular esophagi and ureters compared to the native condition. In contrast, these values were strongly decreased in the skin after acellularization. Acellularization-related decreases in maximum strain were found in all tissues. Type I collagens were well-preserved in these samples; however, clotting and a loss of cross-linking type I collagens was observed ultrastructurally. Elastins and fibronectins were preserved in the esophagi and ureters. A loss of the epidermal layer and decreased fibronectin content was present in the skin. Discussion Acellularization induces changes in the tensile properties of soft tissues. Some of these changes appear to be organ specific. Loss of cross-linking type I collagen may indicate increased mechanical strength due to decreasing transverse forces acting upon the scaffolds, whereas fibronectin loss may be related to decreased load-bearing capacity. Potentially, the alterations in tissue mechanics are linked to organ function and to the interplay of cells and the extracellular matrix, which is different in hollow organs when compared to skin. PMID:26960134

Mechanical Characterization of Electrospun Nanocomposite Fibers

NASA Astrophysics Data System (ADS)

Alsmairat, Ohood

Electrospinning is considered one of the most efficient techniques used for producing fibers in the nanometer to micrometer ranges. The mechanical properties of the electrospun fibers depend on the solution used to produce them. The present study focuses on dissolving the PolyMethalylmethacrylate (PMMA) in acetone solvent. A concentration of 23% PMMA was found to be the best concentration for producing smooth fibers with almost no beads. We studied the effect of mixing the PMMA with two types of nanotubes on the mechanical properties of the fibers. A Carbon-Nano-Tubes (CNT) and Boron-Nitride-Nano-Tubes were mixed with PMMA solution at different ratios to produce a CNT/PMMA and BNNT/PMMA solutions with different concentrations of 0.1%, 0.25%, and 0.6%. Electrospinning technique was used to produce fibers from the PMMA, CNT/PMMA, and BNNT/PMMA solutions. All fibers were tested experimentally with a micro-tensile-tester to produce stress-strain curves that were used to extract the average modulus of elasticity, maximum strength, and fracture point for each fiber. Enhancements in the Youngs modulus and maximum tensile strength of the fibers were observed with the addition of CNTs. Further enhancements were observed with the addition of BNNTs. A random sample of 0.6% CNT/PMMA fibers was tested with Raman spectrometer and the results show a linear change in the frequency-strain curve.

Disrupting the Myosin Converter-Relay Interface Impairs Drosophila Indirect Flight Muscle Performance

PubMed Central

Ramanath, Seemanti; Wang, Qian; Bernstein, Sanford I.; Swank, Douglas M.

2011-01-01

Structural interactions between the myosin converter and relay domains have been proposed to be critical for the myosin power stroke and muscle power generation. We tested this hypothesis by mutating converter residue 759, which interacts with relay residues I508, N509, and D511, to glutamate (R759E) and determined the effect on Drosophila indirect flight muscle mechanical performance. Work loop analysis of mutant R759E indirect flight muscle fibers revealed a 58% and 31% reduction in maximum power generation (PWL) and the frequency at which maximum power (fWL) is generated, respectively, compared to control fibers at 15°C. Small amplitude sinusoidal analysis revealed a 30%, 36%, and 32% reduction in mutant elastic modulus, viscous modulus, and mechanical rate constant 2πb, respectively. From these results, we infer that the mutation reduces rates of transitions through work-producing cross-bridge states and/or force generation during strongly bound states. The reductions in muscle power output, stiffness, and kinetics were physiologically relevant, as mutant wing beat frequency and flight index decreased about 10% and 45% compared to control flies at both 15°C and 25°C. Thus, interactions between the relay loop and converter domain are critical for lever-arm and catalytic domain coordination, high muscle power generation, and optimal Drosophila flight performance. PMID:21889448

Wrinkle surface instability of an inhomogeneous elastic block with graded stiffness

NASA Astrophysics Data System (ADS)

Yang, Shengyou; Chen, Yi-chao

2017-04-01

Surface instabilities have been studied extensively for both homogeneous materials and film/substrate structures but relatively less for materials with continuously varying properties. This paper studies wrinkle surface instability of a graded neo-Hookean block with exponentially varying modulus under plane strain by using the linear bifurcation analysis. We derive the first variation condition for minimizing the potential energy functional and solve the linearized equations of equilibrium to find the necessary conditions for surface instability. It is found that for a homogeneous block or an inhomogeneous block with increasing modulus from the surface, the critical stretch for surface instability is 0.544 (0.456 strain), which is independent of the geometry and the elastic modulus on the surface of the block. This critical stretch coincides with that reported by Biot (1963 Appl. Sci. Res. 12, 168-182. (doi:10.1007/BF03184638)) 53 years ago for the onset of wrinkle instabilities in a half-space of homogeneous neo-Hookean materials. On the other hand, for an inhomogeneous block with decreasing modulus from the surface, the critical stretch for surface instability ranges from 0.544 to 1 (0-0.456 strain), depending on the modulus gradient, and the length and height of the block. This sheds light on the effects of the material inhomogeneity and structural geometry on surface instability.