scholarly journals Nonlinear chiral rheology of phospholipid monolayers

Soft Matter ◽  
2018 ◽  
Vol 14 (13) ◽  
pp. 2476-2483 ◽  
Author(s):  
KyuHan Kim ◽  
Siyoung Q. Choi ◽  
Joseph A. Zasadzinski ◽  
Todd M. Squires
Keyword(s):  
Elastic Moduli ◽  
Mechanical Response ◽  
Response Property ◽  
Monomolecular Film ◽  
Phospholipid Monolayers ◽  
Applied Torque ◽  
Nonlinear Elastic ◽  
Healing Processes

The macroscopic, mechanical response property of a monomolecular film of the phospholipid DPPC is chiral: values of nonlinear elastic moduli and yield stresses are quite different, depending on the direction of the applied torque; even healing processes after removing a large torque also exhibit completely different behaviors.

Molecular dynamics study on the mechanical response and failure behaviour of graphene: performance enhancement via 5–7–7–5 defects

RSC Advances ◽  
2016 ◽  
Vol 6 (31) ◽  
pp. 26361-26373 ◽  
Author(s):  
G. Rajasekaran ◽  
Avinash Parashar
Keyword(s):  
Molecular Dynamics ◽  
Tensile Strength ◽  
Structural Properties ◽  
Elastic Moduli ◽  
Mechanical Response ◽  
Performance Enhancement ◽  
Structural Defects ◽  
Thick Sheet ◽  
Failure Behaviour ◽  
Production Techniques

A one atom-thick sheet of carbon exhibits outstanding elastic moduli and tensile strength in its pristine form but structural defects which are inevitable in graphene due to its production techniques can alter its structural properties.

Design with Nonhomogeneous Materials—Part I: Pure Bending of Prismatic Bars

1987 ◽  
Vol 109 (1) ◽  
pp. 82-86 ◽  
Author(s):  
V. K. Stokes
Keyword(s):  
Tensile Test ◽  
Material Properties ◽  
Elastic Moduli ◽  
Mechanical Response ◽  
Mechanical Design ◽  
Beam Theory ◽  
Pure Bending ◽  
Strongly Coupled ◽  
Point To Point ◽  
Nonhomogeneous Materials

Because material properties vary from point to point in nonhomogeneous materials, there is some question as to what “properties” are measured in tests such as the tensile test, and how such “properties” can be used in the mechanical design process. In this paper, the mechanical response of nonhomogeneous prismatic bars in pure bending has been shown to depend on parameters that are strongly coupled combinations of geometry and material properties. The purely geometry based inertia tensor in homogeneous beam theory is replaced in the nonhomogeneous case by the rigidity tensor, which combines geometry and material properties. Interpretations for the average elastic moduli, which would be determined by tests on nonhomogeneous materials, have been explored. Also discussed is the usefulness of such average moduli for predicting the mechanical response of nonhomogeneous bars.

Proposed experimental tests of a theory of fine microstructure and the two-well problem

1992 ◽  
Vol 338 (1650) ◽  
pp. 389-450 ◽  
Keyword(s):  
Free Energy ◽  
Mechanical Response ◽  
Experimental Tests ◽  
Martensitic Transformations ◽  
Free Energy Function ◽  
Minimizing Sequences ◽  
Nonlinear Elastic Material ◽  
Theoretical Predictions ◽  
Fine Microstructure ◽  
Nonlinear Elastic

Predictions are made based on an analysis of a new nonlinear theory of martensitic transformations introduced by the authors. The crystal is modelled as a nonlinear elastic material, with a free-energy function that is invariant with respect to both rigid-body rotations and the appropriate crystallographic symmetries. The predictions concern primarily the two-well problem , that of determining all possible energy-minimizing deformations that can be obtained with two coherent and macroscopically unstressed variants of martensite. The set of possible macroscopic deformations obtained is completely determined by the lattice parameters of the material. For certain boundary conditions the total free energy does not attain a minimum , and the finer and finer oscillations of minimizing sequences are interpreted as corresponding to microstructure. The predictions are am enable to experimental tests. The proposed tests involve the comparison of the theoretical predictions with the mechanical response of properly oriented plates subject to simple shear.

Nonlinear Elastic Analysis of the Hardness Test on Rubber-Like Materials

1991 ◽  
Vol 64 (2) ◽  
pp. 202-210 ◽  
Author(s):  
W. V. Chang ◽  
S. C. Sun
Keyword(s):  
Finite Element ◽  
Linear Elasticity ◽  
Elastic Moduli ◽  
Indentation Depth ◽  
Nonlinear Effects ◽  
Hardness Test ◽  
Constitutive Law ◽  
Total Load ◽  
Depth Difference ◽  
Nonlinear Elastic

Abstract Both the Ogden-Tschoegl nonlinear elastic constitutive law and a contact algorithm in the general-purpose finite-element program AFEM have been used to examine the use of IRHD values to relate the elastic properties of elastomers. We are aware that large deformations of rubber specimens and complicated interface conditions are involved in this so-called simple test. However, from the finite-element results, we find that the linearly elastic Hertz contact solution is a reasonably accurate model. This can be attributed to several points. First, the hardness test involves mainly compression and shear deformation and the linearly elastic behavior is more closely followed in rubbers for the above two types of deformation. Second, although nonlinear effects become significant in soft rubbers and higher indentation cases, the ASTM D 1415 standard defines larger indentation depth differences for smaller IRHD values. The definition itself compensates for the nonlinear effects. Third, although the interfacial stress field changed due to different frictional conditions, we calculated the IRHD values only from indentation depth difference and total load applied to the steel ball. Both the indentation depth difference and the total load are obtained from far-field conditions and do not change significantly. We should note that using linear elasticity to correlate the elastic moduli and IRHD values is simply a special case in rubber elasticity. We conveniently get rubber's elastic moduli from IRHD values based on linear elasticity, but the complete rubber-like material behavior has to be obtained from more general experiments and described by a nonlinear constitutive law such as the Ogden-Tschoegl model.

Comparison of linear and nonlinear elastic moduli for reservoir rock by use of a granular medium model

1996 ◽  
Vol 99 (3) ◽  
pp. 1360-1365 ◽  
Author(s):  
I. Yu. Belyaeva ◽  
L. A. Ostrovsky ◽  
V. Yu. Zaitsev ◽  
V. Stefan ◽  
A. M. Sutin
Keyword(s):  
Granular Medium ◽  
Elastic Moduli ◽  
Reservoir Rock ◽  
Medium Model ◽  
Linear And Nonlinear ◽  
Nonlinear Elastic

Some Remarks on the Effect of Interphases on the Mechanical Response and Stability of Fiber-Reinforced Elastomers

2012 ◽  
Vol 79 (3) ◽  
Author(s):  
Katia Bertoldi ◽  
Oscar Lopez-Pamies
Keyword(s):  
Mechanical Response ◽  
Fiber Composite ◽  
Fiber Reinforced ◽  
Elastic Solids ◽  
Elastomeric Matrix ◽  
Fiber Reinforced Materials ◽  
Drastic Effect ◽  
American Society ◽  
Nonlinear Elastic ◽  
Fiber Composite Materials

In filled elastomers, the mechanical behavior of the material surrounding the fillers -termed interphasial material-can be significantly different (softer or stiffer) from the bulk behavior of the elastomeric matrix. In this paper, motivated by recent experiments, we study the effect that such interphases can have on the mechanical response and stability of fiber-reinforced elastomers at large deformations. We work out in particular analytical solutions for the overall response and onset of microscopic and macroscopic instabilities in axially stretched 2D fiber-reinforced nonlinear elastic solids. These solutions generalize the classical results of Rosen (1965, “Mechanics of Composite Strengthening,” Fiber Composite Materials, American Society for Metals, Materials Park, OH, pp. 37–75), and Triantafyllidis and Maker (1985, “On the Comparison between Microscopic and Macroscopic Instability Mechanisms in a Class of Fiber-Reinforced Composites,” J. Appl. Mech., 52, pp. 794–800), for materials without interphases. It is found that while the presence of interphases does not significantly affect the overall axial response of fiber-reinforced materials, it can have a drastic effect on their stability.

scholarly journals ON THE MECHANICAL RESPONSE OF A PRESSURIZED FUNCTIONALLY-GRADED CYLINDER

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Vlado Lubarda
Keyword(s):  
Shear Stress ◽  
Power Law ◽  
Functionally Graded Material ◽  
Elastic Moduli ◽  
Mechanical Response ◽  
Maximum Shear Stress ◽  
Radial Distance ◽  
Functionally Graded ◽  
Graded Material ◽  
Radial Inhomogeneity

A pressurized functionally-graded cylinder is considered made of the material whose elastic moduli vary with the radial distance according to the power-law relation. Some peculiar features of the mechanical response are noted for an incompressible functionally-graded material with the power of radial inhomogeneity equal to two. In particular, it is shown that the maximum shear stress is constant throughout the cylinder, while the displacement changes proportional to 1/r along the radial distance. No displacement takes place at all under equal pressures applied at both boundaries.

Modelling of Shape Memory Alloy Negator Springs for Long-Stroke Constant-Force Actuators

2012 ◽  
Vol 78 ◽  
pp. 52-57
Author(s):  
Andrea Spaggiari ◽  
Eugenio Dragoni
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Elastic Moduli ◽  
Mechanical Response ◽  
Constant Force ◽  
Output Force ◽  
Different Temperatures ◽  
Strip Metal ◽  
Long Stroke ◽  
Intrinsic Characteristic

The paper deals with the analytical modelling of a shape memory alloy Negator spring. Negator springs are spiral springs made of strip metal wound on the flat with an inherent curvature such that, in repose, each coil wraps tightly on its inner neighbour. This configuration allows a constant force mechanical response and very long strokes, limited mainly from the total length of the spring. The authors investigate the behaviour of the spring made of a shape memory alloy (SMA). The intrinsic characteristic of SMA is to have two different elastic moduli at different temperatures. This difference can be exploited in order to have a net actuation force for the entire very long stroke, overcoming the two major drawbacks of the SMA actuators, short strokes and output force which varies linearly during the travel.

scholarly journals A Unified Phenomenological Model for Tensile and Compressive Response of Polymeric Foams

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Timothy R. Walter ◽  
Andrew W. Richards ◽  
Ghatu Subhash
Keyword(s):  
Phenomenological Model ◽  
Elastic Moduli ◽  
Mechanical Response ◽  
Model Parameters ◽  
Polymeric Foams ◽  
Compressive Response ◽  
Tensile Response ◽  
Tension And Compression ◽  
Engineering Parameters ◽  
Strain Responses

Tensile and compressive stress-strain responses were obtained for various densities of polymer foams. These experimental data were used to determine relevant engineering parameters (such as elastic moduli in tension and compression, ultimate tensile strength, etc.) as a function of foam density. A phenomenological model applicable for both compressive and tensile responses of polymeric foams is validated by comparing the model to the experimentally obtained compression and tensile responses. The model parameters were analyzed to determine the effect of each parameter on the mechanical response of the foam. The engineering parameters were later compared to the appropriate model parameters and a good correlation was obtained. It was shown that the model indeed captures the entire compressive and tensile response of polymeric foams effectively.

scholarly journals Определение модулей упругости третьего порядка в образцах полистирола, изготовленных по разным технологиям

2021 ◽  
Vol 91 (8) ◽  
pp. 1220
Author(s):  
А.В. Белашов ◽  
А.А. Жихорева ◽  
Я.М. Бельтюков ◽  
О.А. Москалюк ◽  
И.В. Семенова
Keyword(s):  
Ethylene Glycol ◽  
Elastic Properties ◽  
Elastic Moduli ◽  
Ultrasonic Method ◽  
Ultrasonic Waves ◽  
Polymer Materials ◽  
Glycol Dimethacrylate ◽  
Third Order ◽  
Temperature Regimes ◽  
Nonlinear Elastic

An ultrasonic method was applied in this work to measure third-order elastic moduli of polystyrene samples fabricated using different technologies: two commercial samples of a styrene copolymer with ethylene glycol dimethacrylate in different concentrations and two laboratory samples obtained by melt technology in different temperature regimes. It is shown that the dependences of nonlinear elastic moduli on the frequency of ultrasonic waves in the range of 1-3 MHz differ significantly between commercial copolymer samples and laboratory samples. The moduli of laboratory samples obtained using the same technology, but in different temperature regimes, also differ markedly. Thus, the manufacturing technology can affect significantly the nonlinear elastic properties of polymer materials.

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