FINITE STRAIN MEASUREMENT USING IMAGE ANALYSIS UNDER REVERSE SHEAR AFTER FORWARD SHEAR

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Yasuyuki Kato
Keyword(s):  
Image Analysis ◽  
Effective Strain ◽  
Local Deformation ◽  
Gauge Length ◽  
Strain Theory ◽  
Strain Component ◽  
Deformation Path ◽  
Strain Behavior ◽  
Natural Strain ◽  
Shearing Strain

The purpose of this research is to investigate the progress of local deformation under finite deformation by using image analysis based on the Natural Strain theory. Since Natural Strain used in the image analysis can satisfy the addition law of strain on an identical line element and can remove the rigid body rotation from shearing strain component, it is an effective strain for representing stress and strain behavior under large deformation. Therefore, in this research, these features of Natural Strain theory will be incorporated into the method of image analysis. In the present study, using the test pieces made of high purity tough pitch copper, the local deformation occurring under large simple shear is investigated by comparing the strains in each element from the upper position to the middle position with the average strain in the gauge length. In order to investigate the progress of local deformation caused by differences of strain hardening in the material, the experiments are conducted under different deformation histories which are given by applying reverse shear after applying forward shear with different sizes. Consequently, it is revealed that if the value of plastic strain obtained by integrating over the whole deformation path is almost the same, the progress of local deformation is approximately the same even if the deformation path is different.

IMAGE ANALYSIS BASED FINITE STRAIN MEASUREMENT OF LOCAL DEFORMATION UNDER UNIAXIAL LOAD USING NATURAL STRAIN

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Yasuyuki Kato
Keyword(s):  
Image Analysis ◽  
Strain Measurement ◽  
Finite Strain ◽  
Local Deformation ◽  
Strain Theory ◽  
Strain Behavior ◽  
Natural Strain ◽  
Strain Components ◽  
Shearing Strain ◽  
Local Deformations

This paper describes the effectiveness of image analysis based on the Natural Strain theory for measuring the finite strain. Since the additive law of strain on an identical line element can be satisfied and the rigid body rotation can clearly be removed from the shearing strain components, the Natural Strain theory is significantly effective for representing the stress-strain behavior under large elasto-plastic deformation. In this study, the strain measurements under large deformation are conducted by making use of such merits into the image analysis. In our previous studies, in order to verify the effectiveness of this method, the results of strain measurement by image analysis have been compared with the results of conventional strain measurement based on the displacement meter. Consequently, since the results of both measurements almost coincide, the validity of this image analysis has been confirmed. However, these experiments were limited to uniform deformation fields, although in the range of finite deformation. Hence, as for the local deformation, the detailed measurements have not been carried out yet in our previous study. So, in this paper, the local deformations generated under uniaxial tension and simple shear are investigated as the fundamental research. Especially, the progress of local deformations is revealed by comparing the measured values of upper and middle positions in the specimen.

YIELD SURFACE SHAPE ESTIMATED BY USING NATURAL STRAIN UNDER PRE-DEFORMATION OF TENSION AFTER SIMPLE SHEAR

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Yasuyuki Kato
Keyword(s):  
Simple Shear ◽  
Yield Surface ◽  
Effective Strain ◽  
Surface Shape ◽  
Strain Component ◽  
Deformation History ◽  
Proportional Loading ◽  
Strain Behavior ◽  
Natural Strain ◽  
Deformation State

Since the rigid body rotation can be clearly removed from the shearing strain component, and the additive law of strain can be satisfied, the Natural Strain is effective strain representation for expressing the stress-strain behavior under large elasto-plastic deformation. Based on the Natural Strain theory, the purpose of this study is to clarify the mechanism of development of anisotropy in the yield surface that occurs with the progression of deformation by examining the shape of yield surface obtained under large deformation. In our previous studies, using test pieces that the large pre-deformation of uniaxial tension, simple shear and the proportional loading of them are applied, proportional loading tests are carried out again by changing the ratio of tension and shear. In the present paper, another type of the pre-deformation that the deformation path is different but the final deformation state is the same as the predeformation of proportional loading of tension and shear, is chosen as the subject of this study. In particular, the deformation history of tension after simple shear is examined in this study. Then, the relationship between the development of anisotropy in yield surface and the deformation history is revealed in this paper.

DISTRIBUTION OF SHEAR STRAIN IN SQUARE CROSS-SECTION SHAFT MEASURED USING IMAGE ANALYSIS UNDER LARGE DEFORMATION

2020 ◽  
Vol 7 (2) ◽  
Author(s):  
Yasuyuki Kato
Keyword(s):  
Image Analysis ◽  
Natural Rubber ◽  
Shear Strain ◽  
Large Deformation ◽  
Cross Section ◽  
Image Data ◽  
Gauge Length ◽  
Strain Theory ◽  
Test Pieces ◽  
The Cross

In the present study, the distribution of shear strain and warping in a square cross-section shaft generated under a large torsion is investigated using the image analysis based on the Natural Strain theory. The scribe lines are drawn in a grid on a surface of the test pieces made of natural rubber, and the image data of each element in the horizontal direction along the cross-section at the center and upper positions are taken by using a high-pixel camera equipped with macro lens. The distributions for shear strain and warping along the cross-section are obtained from that image data. These measured distributions under large deformation are compared with the distributions based on the conventional torsional theory of a square cross-section shaft, i.e., Saint Venant's theory for torsion. Moreover, taking the effect due to the elongation on the surface of specimens into consideration, the distributions modified elongation of gauge length are compared with experiments, and the validity of the present experimental results are confirmed in this paper.

Cyclic Plasticity for Nonproportional Paths: Part 1—Cyclic Hardening, Erasure of Memory, and Subsequent Strain Hardening Experiments

1978 ◽  
Vol 100 (1) ◽  
pp. 96-103 ◽  
Author(s):  
H. S. Lamba ◽  
O. M. Sidebottom
Keyword(s):  
Strain Hardening ◽  
Effective Strain ◽  
Strain Range ◽  
Cyclic Hardening ◽  
Cyclic Plasticity ◽  
Phase Cycling ◽  
Strain Behavior ◽  
Subsequent Yield Surface ◽  
Strain Hardening Behavior ◽  
Annealed Copper

Extensive experiments were conducted on annealed copper under cyclic nonproportional strain histories. After cyclically stabilizing the material by uniaxial cycling, out-of-phase axial-shear strain cycling for the same effective strain range caused additional increases in stress amplitudes to restabilized levels. Following cyclic stabilization of the material under out-of-phase cycling, a cycle whose effective strain amplitude was comparable to those of previous cycles resulted in stress-strain behavior unique to that cycle and independent of prior stable deformation. The experimental verification of this material property, which has been the subject of much conjecture, allowed the design of a fundamental class of experiments that determined the subsequent yield surface and strain hardening behavior from only one specimen.

YIELD STRESS BASED ON NATURAL STRAIN THEORY UNDER CYCLIC TENSION-COMPRESSION LOAD AFTER LARGE SIMPLE SHEAR

2018 ◽  
Vol 5 (2) ◽  
Author(s):  
Yasuyuki Kato ◽  
Hiroki Uchida
Keyword(s):  
Yield Stress ◽  
Uniaxial Tension ◽  
Simple Shear ◽  
Strain Theory ◽  
Experimental Result ◽  
Cyclic Loads ◽  
Yield Behavior ◽  
Compression Load ◽  
Natural Strain ◽  
Tension And Compression

Many researches on the yield behavior under cyclic loads have been conducted for many years. However, almost these studies have been done within the range of relatively small size deformation. Hence, the detailed studies for yield phenomenon under cyclic loads after applying a large pre-deformation have not been sufficiently elucidated. Therefore, in the series of our studies, using test pieces of high purity tough pitch copper, the yield behavior generated under cyclic loads after applying the predeformation of large uniaxial tension or large simple shear have been investigated. However, as for the case that the type of pre-deformation differs from the type of deformation in the cyclic load, detailed studies have not been conducted yet. Hence, in the present study, the yield behavior generated under cyclic loads for tension and compression after applying a large pre-deformation of simple shear is examined based on Natural Strain theory. Furthermore, experimental results in the present study are compared with results of previous studies concerning cyclic loads for tension and compression after applying the large uniaxial tension. Consequently, it is revealed that the decreasing tendency of yield stress at the compression side appears more strongly as compared with the experimental result by previous study that the pre-deformity is a uniaxial tension.

scholarly journals Multiscale porosity estimates along the pro-and retrograde deformation path: an example from Alpine slates

2018 ◽  
Author(s):  
Ismay Vénice Akker ◽  
Josef Kaufmann ◽  
Guillaume Desbois ◽  
Jop Klaver ◽  
Janos L. Urai ◽  
...  
Keyword(s):  
Image Analysis ◽  
Cross Sections ◽  
Co2 Sequestration ◽  
Mercury Intrusion Porosimetry ◽  
Mechanical Stability ◽  
Ion Beam ◽  
Deformation Path ◽  
Surface Samples ◽  
Pore Types ◽  
Prograde Path

Abstract. Estimating porosity of slates is of great interest for the recently rising industries dealing with the underground such as CO2 sequestration, nuclear waste disposal and shale gas but also for engineering purposes in terms of mechanical stability for underground or surface constructions. In this study, we aim understanding estimates of porosity of slates from the Infrahelvetic Flysch Units (IFU) in the Glarus Alps (eastern Switzerland) and their changes as function of varying metamorphic grade. Surface and sub-surface samples are collected along a temperature gradient from 200 to 320 °C and give therefore the opportunity to link pore types along the deformation path and to surface processes or indicate what artificially induced porosity is. A developed workflow consists of a combination of bulk rock measurements such as Helium pycnometry (He-pycnometry) and Mercury Intrusion Porosimetry (MIP) with image analysis. Image analysis is performed on high scale resolution with Scanning Electron Microscopy (SEM) on Broad Ion Beam (BIB) prepared cross sections (BIB-SEM). Different vein generations give evidence for porosity formation at depth. Towards peak metamorphic conditions (prograde path) porosity reduces to

New Concept of Equivalent Inherent Strain for Measuring Axisymmetric Residual Stresses

1997 ◽  
Vol 122 (2) ◽  
pp. 304-309 ◽  
Author(s):  
Jun Chen ◽  
Toshio Terasaki ◽  
Tetsuya Akiyama ◽  
Katsuhiko Kishitake
Keyword(s):  
Numerical Simulation ◽  
Residual Stresses ◽  
Experimental Measurement ◽  
Accurate Method ◽  
High Accuracy ◽  
Strain Theory ◽  
Strain Component ◽  
Component Estimation ◽  
Inherent Strain ◽  
Inherent Strain Method

A new concept, the equivalent inherent strain gθeq, is proposed for measuring axisymmetric residual stresses, based on the inherent strain theory. gθeq is a parameter obtained by incorporating the radial inherent strain component into the tangential inherent strain component in computing the axially uniform axisymmetric residual stresses. The application of this concept can avoid the restriction of radial inherent strain component estimation and hence leads to a more simple and accurate method for measuring axisymmetric residual stresses. Experimental measurement and numerical simulation were carried out to demonstrate that this method has both the simplicity of the Sachs method and the high accuracy of the inherent strain method. [S1087-1357(00)70402-3]

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