Quantitative Evaluation of Dislocation Structure Induced by Cyclic Plasticity

2007 ◽  
Vol 345-346 ◽  
pp. 49-52 ◽  
Author(s):  
Tsuyoshi Mayama ◽  
Katsuhiko Sasaki ◽  
Yoshihiro Narita
Keyword(s):  
Cyclic Loading ◽  
Quantitative Evaluation ◽  
Strain Amplitude ◽  
Dislocation Structure ◽  
Evaluation Method ◽  
Cyclic Hardening ◽  
Cyclic Softening ◽  
Cyclic Plasticity ◽  
Loading Test ◽  
Loading Tests

In the present study, a new approach is conducted to evaluate dislocation structure induced by cyclic plasticity. First, cyclic plastic loading tests are carried out up to 100 cycles with three different small strain amplitudes on SUS316L stainless steel at room temperature. The test result presents the dependence of the strain amplitude on cyclic hardening and softening behaviors. Specifically, it is found that the cyclic loading test with strain amplitude of 0.25% shows both cyclic hardening and cyclic softening, while the cyclic loading tests with strain amplitudes of 0.75% and 1.0% show no cyclic softening. Secondly, the dislocation structures of the specimens after cyclic loading are observed by using a transmission electron microscope (TEM), and this observation reveals that the dislocation structure after cyclic loading test depends on the strain amplitude. Finally, a quantitative evaluation method of the dislocation structure is also proposed. The TEM images are converted into binary images and the resolution dependence of the generated binary image is used to visualize the characteristics of the dislocation structure. The relationship between strain amplitudes of cyclic plasticity and dislocation structure organization is clarified by the evaluation method. Finally, the heterogeneity of the dislocation structure is discussed.

The uniaxial and biaxial, monotonic and cyclic plasticity behaviour of a lead alloy model material

1983 ◽  
Vol 18 (2) ◽  
pp. 125-133 ◽  
Author(s):  
T H Hyde
Keyword(s):  
Cyclic Loading ◽  
Cyclic Hardening ◽  
Model Material ◽  
Monotonic Loading ◽  
Biaxial Stress ◽  
Cyclic Plasticity ◽  
Lead Alloy ◽  
Material Behaviour ◽  
Loading Tests ◽  
Chill Cast

A chill-cast, antimony-arsenic-lead alloy model material has been used to investigate the monotonic and cyclic loading, uniaxial and biaxial plasticity behaviour of a metal at elevated temperature, i.e., T/ Tm ≈ 0.5. For the lead alloy used, a post-machining heat treatment of 96h at 100 C considerably reduced the scatter in the material behaviour. Uniaxial monotonic loading tests showed that the behaviour is relatively independent of temperature and strain-rate for strains less than about 1 per cent. Under cyclic loading conditions, between fixed strain limits, a stable hysteresis loop is obtained after the first cycle for both uniaxial and biaxial stress systems. By taking into account the biaxiality ratio and the increase in yield-range caused by cyclic hardening, the uniaxial and biaxial, cyclic plasticity behaviour was reasonably accurately predicted from the uniaxial, monotonic loading behaviour.

scholarly journals Cyclic Soft/Hardening and Microscopic Mechanism of GS-20Mn5

2021 ◽  
Author(s):  
Zongyuan Zou ◽  
Doudou Liu ◽  
Shuting Han ◽  
Chunyan Song ◽  
Hongzhong Wang
Keyword(s):  
Cyclic Loading ◽  
Mechanical Response ◽  
Cast Steel ◽  
Cyclic Hardening ◽  
Cyclic Softening ◽  
Offshore Platforms ◽  
Microscopic Mechanism ◽  
Tem Analysis ◽  
Loading Tests ◽  
Cyclic Loading Tests

Abstract The cyclic plastic characteristics of metal materials are different from the deformation characteristics under monotonic loading, which has an important effect on the safety of structures in service under cyclic loading. However, GS-20Mn5, which is commonly used in large hydraulic machine beams, offshore platforms and large Bridges, is still lacking the studies of mechanical response characteristics under cyclic loading. In this study, the cyclic softening/hardening characteristics of GS-20Mn5 are studied by a series of cyclic loading tests under uniaxial strain control. Combined with transmission electron microscope (TEM) analysis of cyclic loading tests under typical strain levels, the microscopic mechanism of cyclic softening/hardening is discussed. The results show that the cyclic softening/hardening properties of GS-20Mn5 cast steel are sensitive to amplitudes and cycles. At smaller strain amplitudes (0.16%,0.2% and 0.3%), the cyclic hardening properties of GS-20Mn5 cast steel are rapid at the beginning of the cycle, followed by cyclic softening and then slow secondary cyclic hardening at the end. However, under larger strain amplitudes (0.4% and 0.5%), the cyclic hardening continues during the cyclic loading, and the hardening rate is bigger at the beginning of the cyclic loading and smaller at the later cyclic stage. The cyclic softening/hardening characteristics of GS-20Mn5 cast steel are related to the dislocation structure of ferrite and pearlite. Taking the strain amplitude of 0.2% as an example, the initial cyclic hardening is mainly caused by the proliferation and interaction of dislocations in ferrite. Dislocation spots and cell walls in ferrite grains are mainly caused cyclic softening at the initial stage, the secondary cyclic hardening is directly related to dislocation proliferation and entanglement in pearlite.

Modelling of Cyclic Plasticity With Unified Constitutive Equations: Improvements in Simulating Normal and Anomalous Bauschinger Effects

1980 ◽  
Vol 102 (2) ◽  
pp. 215-222 ◽  
Author(s):  
A. K. Miller
Keyword(s):  
Constitutive Equations ◽  
Work Hardening ◽  
Hysteresis Loops ◽  
Experimental Tests ◽  
Cyclic Hardening ◽  
Back Stress ◽  
Cyclic Softening ◽  
Cyclic Plasticity ◽  
Dislocation Loops ◽  
Work Hardening Coefficient

In simulating cyclic plasticity with several existing “unified” constitutive equations, the predicted hysteresis loops are “oversquare” with respect to experimentally-observed behavior. To eliminate this shortcoming in the constitutive equations developed by the present author, the work-hardening coefficient in the equation controlling the back stress (R) has been made a function of the back stress itself and the sign of the effective modulus-compensated stress σ/E – R. This improvement results in simulated hysteresis loops whose curvature closely resembles that in experimental tests. The improvement preserves all of the previously demonstrated capabilities such as cyclic hardening, cyclic hardening, cyclic softening, etc. The same equations can also simulate some unusual experimentally-observed Bauschinger effects involving local reversals in curvature. The curvature reversals in the simulations result from strain softening of the isotropic work-hardening variable in the equations. The physical significance of the behavior of the constitutive equations is discussed in terms of annihilation of previously-generated dislocation loops by reversing dislocations and experimentally-observed decreases in dislocation density and dissolution of cell walls upon stress reversal.

Modeling of Low Cycle Behavior of P92 Steel Based on Cyclic Plasticity Constitutive Equations

2015 ◽  
Vol 750 ◽  
pp. 41-46 ◽  
Author(s):  
Xiao Wei Wang ◽  
Jian Ming Gong ◽  
Yong Jiang ◽  
Yan Ping Zhao ◽  
Ming Hao Yu
Keyword(s):  
High Temperature ◽  
Strain Amplitude ◽  
Model Comparison ◽  
Low Cycle Fatigue ◽  
Cyclic Softening ◽  
Cyclic Plasticity ◽  
P92 Steel ◽  
Softening Behavior ◽  
Steel Material ◽  
Cyclic Plasticity Model

Strain controlled uniaxial low cycle fatigue (LCF) tests of P92 steel were conducted at strain amplitudes of 0.4%, 0.6% and 0.8% in fully reversed manner with strain rate of 1.0×10-3s-1 at high temperature of 650 °C. Cyclic softening behavior was studied and time-independent cyclic plasticity model was used to represent the cyclic mechanical behavior of this steel. Material parameters were determined step by step at higher strain amplitude of 0.8%, experimental data with lower strain amplitude were used to validate the extrapolation of the model. Comparison of the simulated and experimental results shows that the proposed model can give a reasonable prediction of stress-strain hysteresis loop for P92 steel at high temperature.

A Phenomenological Model for Cyclic Plasticity

1997 ◽  
Vol 119 (1) ◽  
pp. 7-11 ◽  
Author(s):  
Dar-Yun Chiang
Keyword(s):  
Cyclic Loading ◽  
Phenomenological Model ◽  
Material Properties ◽  
Experimental Studies ◽  
Cyclic Hardening ◽  
Analytical Models ◽  
Cyclic Plasticity ◽  
Loading Conditions ◽  
Microstructural Behavior ◽  
Distributed Elements

A phenomenological model is proposed for cyclic plasticity based on the concept of distributed elements, which is capable of reflecting microstructural behavior of real materials under multiaxial cyclic loading conditions. By investigating the detailed behavior of the model, various important phenomena and effects of materials in cyclic plasticity can be elucidated. Generalization of the model is also done to include cyclic hardening effects. A thorough understanding of these complicated response mechanisms and material properties provides useful insight and guidelines for validating analytical models and for performing experimental studies in the related areas of cyclic plasticity.

scholarly journals Classification and Fractal Characteristics of Limestone Fragments Obtained in Conventional Compression and Cyclic Loading Tests under Uniaxial and Triaxial Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Rui Yang ◽  
Xiaodi Wang ◽  
Hao Zha ◽  
Xiuzhang Yang ◽  
Yang Zhang ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Small Difference ◽  
Confining Pressure ◽  
Test System ◽  
Theoretical Research ◽  
Loading Conditions ◽  
Loading Test ◽  
Loading Tests ◽  
Fractal Characteristics ◽  
Cyclic Loading Tests

The mechanical response characteristics of rocks under cyclic loading conditions are crucial factors for evaluating and analyzing the stability of rock mass during underground excavation. In this study, based on fractal theory and a series of tests using the MTS815.02 rock mechanics test system, the classification and fractal characteristics of limestone specimen fragments are investigated. The results show that limestone specimens subjected to cyclic loading can generate more small-sized fragments than conventional compression, but the large-fragment-producing abilities of the two tests exhibit small difference. The mass fraction of the fragments in the cyclic loading test is obviously greater than that in the conventional test when the fragment size is less than 4.75 mm; however, only a small difference is observed between the cyclic loading tests with frequencies of 0.25 and 0.5 Hz. In the same type of test, a confining pressure is helpful in reducing the fragmentation of limestone specimen. As the size interval decreases, the shapes of limestone fragment transition from rectangular to long slice and then to square. The results also indicate that the confining pressure has a significant influence on the size-quantity and size-mass fractal dimensions of limestone fragments. The former has a positive correlation with the confining pressure, whereas the latter decreases with confining pressure. The conclusions obtained in this investigation can enrich the theoretical research on the failure response and mechanism of rock under cyclic loading conditions.

scholarly journals Viscoplastic Parametric Analysis of Cylindrical Specimen Under Cyclic Behaviour

2021 ◽  
pp. 75-82
Author(s):  
Panagiotis J. Charitidis
Keyword(s):  
Cyclic Loading ◽  
Numerical Study ◽  
Kinematic Hardening ◽  
Cyclic Hardening ◽  
Material Model ◽  
Cyclic Plasticity ◽  
Axial Deformation ◽  
Cyclic Behaviour ◽  
Von Mises ◽  
Cyclic Plasticity Model

The present study tries to present a cyclic hardening model with the aim to simulate quantitatively the material response under strain controlled cyclic loading in tension-compression, of specified axial deformation. A numerical study was carried out to investigate the cyclic constitutive behaviour of alloy Indium under viscoplastic deformation. The analysis was performed under prescribed symmetric strain-controlled cyclic loading. The model contains both isotropic and kinematic hardening components, while the analysis were performed using Comsol Multiphysics for only 60 seconds duration. The kinematic hardening was described by using multiple back stresses. Multiple back stresses can provide a smoother transition between the elastic and plastic deformation, and it improves the general shape of the hysteresis loop. Two cases (geometries) have been examined in this study. From the material model and finite element cyclic plasticity model results, it is found that for the same parameters, but different dimensions there is difference on the stress-strain curves as well as on the von Mises stresses.

scholarly journals Payne Effect in Filled Nitrile Rubber Submitted to Cyclic Loadings

2012 ◽  
Author(s):  
Pierre P. Garnier ◽  
Jean-Benoît J. B. Le Cam ◽  
Michel M. Grédiac
Keyword(s):  
Cyclic Loading ◽  
Strain Amplitude ◽  
Viscoelastic Properties ◽  
Nitrile Rubber ◽  
Loading Conditions ◽  
Payne Effect ◽  
Two Temperatures ◽  
Loading Tests ◽  
Number Of Cycles ◽  
Cyclic Loading Tests

This study deals with the viscoelastic properties of filled nitrile rubber submitted to cyclic loading conditions. Classic strain amplitude sweeps were first carried out on both a filled and an unfilled nitrile rubber. Tests were performed at two temperatures ambient and 80 °C. Some specimens were then subjected to a high number of cycles to study the variations in the viscoelastic properties and the sensitivity of the Payne effect to cyclic loading tests at several given strain amplitudes.

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