scholarly journals BEHAVIOR TYPES AND FEATURES OF LATERAL STRAIN AND POISSON’S RATIO OF ISOTROPIC RHEONOMOUS MATERIALS UNDER CREEP CONDITIONS DESCRIBED BY THE LINEAR THEORY OF VISCOELASTICITY

2018 ◽  
Vol 10 (4) ◽  
pp. 65-77
Author(s):  
А.V. Khokhlov ◽  
Keyword(s):  
Linear Theory ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Lateral Strain ◽  
Behavior Types ◽  
Theory Of Viscoelasticity

XRD Tensile Test Technique to Measure Mechanical Properties of Micron-Thick Si and TiN Films

2005 ◽  
Vol 297-300 ◽  
pp. 574-580 ◽  
Author(s):  
Takahiro Namazu ◽  
Shozo Inoue ◽  
Daisuke Ano ◽  
Keiji Koterazawa
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Partial Pressure ◽  
Young’S Modulus ◽  
Poisson’S Ratio ◽  
Young's Modulus ◽  
Poisson's Ratio ◽  
Lateral Strain ◽  
Test Technique ◽  
Tin Films

This paper focuses on investigating mechanical properties of micron-thick polycrystalline titanium nitride (TiN) films. We propose a new technique that can directly measure lateral strain of microscale crystalline specimen by X-ray diffraction (XRD) during tensile test. The XRD tensile test can provide not only Young’s modulus but also Poisson’s ratio of TiN films. Micron-thick TiN films were deposited onto both surfaces of single crystal silicon (Si) specimen by r.f. reactive magnetron sputtering. Young’s modulus and Poisson’s ratio of Si specimen obtained by XRD tensile tests were in good agreement with analytical values. TiN films deposited at Ar partial pressure of 0.7Pa had the average values of 290GPa and 0.36 for Young’s modulus and Poisson’s ratio. The elastic mechanical properties of TiN films gradually decreased down to 220GPa and 0.29 with increasing Ar partial pressure up to 1.0Pa, regardless of film thickness. The change in the film properties with Ar partial pressure would be attributed to the change in the film density.

Improvement of Poisson’s Ratio using Carbon Nanotubes Reinforcement for Laminated Sandwich Plate

2019 ◽  
Vol 11 (1) ◽  
Author(s):  
M. Senbagan ◽  
R. Sarathkumar ◽  
D. Dominic Xavier ◽  
S. Seralathan ◽  
V. Hariram
Keyword(s):  
Carbon Nanotubes ◽  
Poisson’S Ratio ◽  
Longitudinal Strain ◽  
Sandwich Panel ◽  
Sandwich Plate ◽  
Relative Difference ◽  
Poisson's Ratio ◽  
Face Sheet ◽  
Lateral Strain ◽  
Compressive Loads

The focus of this study is to improve the material properties like Poisson's ratio and flexural strength of a sandwich plate by adding carbon nanotubes. A comparative analysis is carried out between sandwich plate with and without addition of carbon nanotubes. Nastran / Patran are the main tools used for this analysis. The experimental work focuses on the behaviour of the sandwich plate while applying tensile and compressive loads. The reduction of displacement in orthogonal sides under compressive stress and tensile stress are observed for carbon nanotubes enriched sandwich plate. This is due to increased face sheet relative difference of lateral strain with longitudinal strain. It is also observed that the mechanical properties of carbon nanotubes enriched sandwich plate are enhanced in comparison to sandwich plate without carbon nanotubes. It is found that, for feasible applications, the sandwich plate enhanced with carbon nanotubes, possess greater face sheet relative difference of lateral strain with longitudinal strain. It is concluded that the Poisson’s ratio for the sandwich panel enriched with carbon nanotubes is advantageous than sandwich panel without carbon nanotubes.

scholarly journals Tendon Fascicles Exhibit a Linear Correlation Between Poisson's Ratio and Force During Uniaxial Stress Relaxation

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Shawn P. Reese ◽  
Jeffrey A. Weiss
Keyword(s):  
Stress Relaxation ◽  
Linear Correlation ◽  
Poisson’S Ratio ◽  
Viscoelastic Behavior ◽  
Uniaxial Stress ◽  
Poisson's Ratio ◽  
Lateral Strain ◽  
Sprague Dawley ◽  
Underlying Mechanisms ◽  
Dependent Mechanism

The underlying mechanisms for the viscoelastic behavior of tendon and ligament tissue are poorly understood. It has been suggested that both a flow-dependent and flow-independent mechanism may contribute at different structural levels. We hypothesized that the stress relaxation response of a single tendon fascicle is consistent with the flow-dependent mechanism described by the biphasic theory (Armstrong et al., 1984, “An Analysis of the Unconfined Compression of Articular Cartilage,” ASME J. Biomech. Eng., 106, pp. 165–173). To test this hypothesis, force, lateral strain, and Poisson's ratio were measured as a function of time during stress relaxation testing of six rat tail tendon fascicles from a Sprague Dawley rat. As predicted by biphasic theory, the lateral strain and Poisson's ratio were time dependent, a large estimated volume loss was seen at equilibrium and there was a linear correlation between the force and Poisson's ratio during stress relaxation. These results suggest that the fluid dependent mechanism described by biphasic theory may explain some or all of the apparent viscoelastic behavior of single tendon fascicles.

scholarly journals NON-MONOTONICITY, SIGN CHANGES AND OTHER FEATURES OF POISSON'S RATIO EVOLUTION FOR ISOTROPIC LINEAR VISCOELASTIC MATERIALS UNDER TENSION AT CONSTANT STRESS RATES

2019 ◽  
Vol 81 (3) ◽  
pp. 271-291
Author(s):  
A.V. Khokhlov
Keyword(s):  
Poisson’S Ratio ◽  
Poisson Ratio ◽  
Constant Stress ◽  
Stress Rate ◽  
Poisson's Ratio ◽  
Lateral Strain ◽  
Viscoelastic Materials ◽  
Sign Changes ◽  
Material Functions ◽  
Different Types

We study analytically the Boltzmann - Volterra linear constitutive equation for isotropic non-aging viscoelastic media in order to elucidate its capabilities to provide a qualitative simulation of rheological phenomena related to different types of evolution of triaxial strain state and of the lateral contraction ratio (the Poisson ratio) observed in uni-axial tests of viscoelastic materials under tension or compression at constant stress rate. In particular, we consider such effects as increasing, decreasing or non-monotone dependences of lateral strain and Poisson's ratio on time, sign changes and negativity of Poisson's ratio (auxeticity effect) and its stabilization at large times. The viscoelasticity equation implies that the hydrostatic and deviatoric parts of stress and strain tensors don't depend on each other. It is governed by two material functions of a positive real argument (that is shear and bulk creep compliances). Assuming both creep compliances are arbitrary positive, differentiable, increasing and convex up functions on time semi-axis, we analyze general expressions for the Poisson ratio and strain triaxiality ratio (which is equal to volumetric strain divided by deviatoric strain) generated by the viscoelasticity relation under uni-axial tension or compression. We investigate qualitative properties and peculiarities of their evolution in time and their dependences on material functions characteristics. We obtain the universal accurate two-sided bound for the Poisson ratio range and criteria for the Poisson ratio increase or decrease and for extrema existence. We derive necessary and sufficient restrictions on shear and bulk creep compliances providing sign changes of the Poisson ratio and negative values of Poisson's ratio on some interval of time. The properties of the Poisson ratio under tension at constant stress rates found in the study we compare to properties the Poisson ratio evolution under constant stress (in virtual creep tests) and illustrate them using popular classical and fractal models with shear and bulk creep functions each one controlled by three parameters. The analysis carried out let us to conclude that the linear viscoelasticity theory (supplied with common creep functions which are non-exotic from any point of view) is able to simulate qualitatively the main effects associated with different types of the Poisson ratio evolution under tension or compression at constant stress rate except for dependence of Poisson's ratio on stress rate. It is proved that the linear theory can reproduce increasing, decreasing or non-monotone and convex up or down dependences of lateral strain and Poisson's ratio on time and it can provide existence of minimum, maximum or inflection points and sign changes from minus to plus and vice versa and asymptotic stabilization at large times.

GENERAL PROPERTIES OF THE CREEP CURVES FOR VOLUMETRIC, AXIAL AND LATERAL STRAIN GENERATED BY THE RABOTNOV NON-LINEAR VISCOELASTICITY RELATION UNDER UNI-AXIAL LOADINGS

2019 ◽  
Vol 81 (2) ◽  
pp. 146-164
Author(s):  
A. V. Khokhlov
Keyword(s):  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Lateral Strain ◽  
Sign Changes ◽  
General Properties ◽  
Material Functions ◽  
Contraction Ratio ◽  
Creep Curves ◽  
Non Linear ◽  
Verification Techniques

The Rabotnov physically non-linear (quasi-linear) constitutive equation for non-aging elasto-viscoplastic materials with four material functions is studied analytically in order to outline the set of basic rheological phenomena which it can simulate, to clarify the material functions governing abilities, to indicate application field of the relation and to develop identification and verification techniques. General properties of the theoretic creep curves for volumetric, longitudinal and lateral strain generated by the model under uni-axial loading are investigated assuming material functions of the relation are arbitrary. Intervals of creep curves monotonicity and conditions for existence of extrema and sign changes are considered and the influence of minimal qualitative restrictions imposed on its material functions is analyzed. It is proved that the Rabotnov relation is able to simulate non-monotone behavior and sign changes of lateral strain and Poisson's ratio (lateral contraction ratio in creep). The expressions for Poisson's ratio via the strain state parameter (equal to volumetric strain divided by deviatoric strain) and via four material functions of the model are derived. The Poisso'n ratio dependence on time, stress level and material functions is examined. Assuming material functions are arbitrary, general two-sided bound for the Poisson's ratio range is obtained. Additional restrictions on material functions providing negative Poisson's ratio values are found and the criterion for its non-dependence on time is formulated. Taking into account volumetric creep (governed by two material functions of the model) is proved to affect strongly the qualitative behavior and characteristic features of longitudinal creep curves and the Poisso'n ratio evolution.

An Iterative Axial and Lateral Ultrasound Strain Estimator Using Subband Division

2020 ◽  
Vol 10 (5) ◽  
pp. 1057-1068
Author(s):  
Hui Peng ◽  
Juhong Tie ◽  
Dequan Guo
Keyword(s):  
Poisson’S Ratio ◽  
Signal To Noise Ratio ◽  
Lateral Displacement ◽  
Axial Strain ◽  
Poisson's Ratio ◽  
Lateral Strain ◽  
Signal To Noise ◽  
Strain Estimation ◽  
Rf Signals ◽  
Noise Ratio

Conventional ultrasound strain imaging usually only calculates the axial strain. Although axial strain is the main component of two dimensional strain field, lateral displacement and strain estimation can provide additional information of human mechanical properties. Shear strain and Poisson’s ratio can be estimated by using lateral strain estimation technique. Low lateral sampling rate and decorrelation noise of lateral radio frequency (RF) signal caused by axial displacement motion increase the difficulty of lateral strain estimation. Subband division technique is to divide a broadband signal into several narrowband signals. In this paper, the application of subband division technique in axial and lateral strain estimation is studied, and an iterative method for estimating axial and lateral strains is proposed based on subband technique. The subband division of this method is carried out along the axial direction, so that the bandwidth of the lateral subband signal is maintained and the quality of the lateral sub strain image is not reduced. In this paper, the number of subbands is three; the compounded lateral strain image is obtained by superimposing these sub strain images on the average. In each iteration, the temporal stretching technique is used to align the axial and lateral RF signals by using the axial and lateral displacement estimation information, which reduces the decorrelation noise of the RF signals. The length of temporal stretching window decreases with the number of iterations, so as to gradually improve the accuracy of temporal stretching. The phase zero algorithm is used to estimate the axial and lateral displacements. The effectiveness of this method is tested by simulations. The simulation results show that the elastographic signal-to-noise ratio (SNRe) of lateral strain image is increased by about 50%, the elastographic contrast noise ratio (CNRe) of lateral strain image is increased by about 120%, the SNRe of axial strain image is increased by about 4%, the CNRe of axial strain image is increased by 8%, and the signal-to-noise ratio of Poisson’s ratio image is increased by about 40%.

scholarly journals On the Experimental Determination of Poisson’s Ratio for Intact Rocks and Its Variation as Deformation Develops

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Lu Dong ◽  
Hongfa Xu ◽  
Pengxian Fan ◽  
Zhichou Wu
Keyword(s):  
Uniaxial Tension ◽  
Poisson’S Ratio ◽  
Axial Strain ◽  
Deformation Modulus ◽  
Poisson's Ratio ◽  
Lateral Strain ◽  
Compression Tests ◽  
Rock Engineering ◽  
Red Sandstone

Poisson’s ratio is of crucial importance for the theoretical and numerical analysis of rock engineering. It is an elastic parameter of the material and the ratio of the absolute value of lateral strain and axial strain when the material is under uniaxial tension or compression. However, it was rarely investigated compared with deformation modulus and strength. Rock materials are different from metal materials. The pure elastic deformation stage is usually very short or nonexistent in the process of uniaxial tension or compression. In this paper, in order to explore the behavior of Poisson’s ratio, uniaxial compression tests according to The International Society for Rock Mechanics and Rock Engineering are performed on standard specimens of granite, marble, red sandstone, carbonate rock, coral concrete, etc. According to the results, Poisson’s ratio, both the secant Poisson’s ratio and tangent Poisson’s ratio, increase with the externally applied stress. Therefore, regarding it as an elastic constant is worthy of a second thought. If the midpoint of the stress interval is fixed in the 50% of uniaxial compressive strength, the average Poisson’s ratio is almost impervious to the varying span of the stress interval. In addition, the average Poisson’s ratio is immune to the nonlinear deformation in the early loading stage. Thus, the average Poisson’s ratio is a better index than the secant Poisson’s ratio in describing the relationship between axial and lateral strains of hard rocks. The determination of Poisson’s ratio of soft rocks needs further investigation because Poisson’s ratio tends to exceed the theoretical limit in relatively low stress levels. The proposed viewpoint provides a deeper insight into the testing, determining, and using of Poisson’s ratio.

The Model for Calculating Elastic Modulus and Poisson's Ratio of Coal Body

2013 ◽  
Vol 6 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Ai Chi ◽  
Li Yuwei
Keyword(s):  
Elastic Modulus ◽  
Poisson’S Ratio ◽  
Fractured Rock ◽  
Rock Block ◽  
Poisson's Ratio ◽  
Linear Elastic ◽  
Study Results ◽  
The Face ◽  
Block Face ◽  
Coal Rock

Coal body is a type of fractured rock mass in which lots of cleat fractures developed. Its mechanical properties vary with the parametric variation of coal rock block, face cleat and butt cleat. Based on the linear elastic theory and displacement equivalent principle and simplifying the face cleat and butt cleat as multi-bank penetrating and intermittent cracks, the model was established to calculate the elastic modulus and Poisson's ratio of coal body combined with cleat. By analyzing the model, it also obtained the influence of the parameter variation of coal rock block, face cleat and butt cleat on the elastic modulus and Poisson's ratio of the coal body. Study results showed that the connectivity rate of butt cleat and the distance between face cleats had a weak influence on elastic modulus of coal body. When the inclination of face cleat was 90°, the elastic modulus of coal body reached the maximal value and it equaled to the elastic modulus of coal rock block. When the inclination of face cleat was 0°, the elastic modulus of coal body was exclusively dependent on the elastic modulus of coal rock block, the normal stiffness of face cleat and the distance between them. When the distance between butt cleats or the connectivity rate of butt cleat was fixed, the Poisson's ratio of the coal body initially increased and then decreased with increasing of the face cleat inclination.

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