Hardening and Degradation Rules for Metals Under Monotonic and Cyclic Loading

1983 ◽  
Vol 105 (2) ◽  
pp. 113-118 ◽  
Author(s):  
Z. Mro´z
Keyword(s):  
Elevated Temperature ◽  
Cyclic Loading ◽  
Creep Deformation ◽  
Elevated Temperatures ◽  
Kinematic Hardening ◽  
Complex Loading ◽  
Material Response ◽  
Inelastic Response ◽  
Hardening Model ◽  
Temperature Creep

In order to describe inelastic response of metals at room or elevated temperatures for complex loading histories, the combined isotropic-kinematic hardening model is discussed. The monotonic and cyclic loading histories are associated with variation of two different hardening parameters and the maximal prestress is assumed to affect essentially the material response. First, the hardening model is applied within time-independent plasticity and next the elevated temperature creep deformation is studied for both monotonic and cyclic loading. The degradation rules are briefly discussed in the last part of the paper.

scholarly journals APPLICATION OF AN ELASTOPLASTIC MODEL TO PREDICT BEHAVIORS OF CONCRETE-FACED ROCK-FILL DAM UNDER COMPLEX LOADING CONDITIONS

2015 ◽  
Vol 21 (7) ◽  
pp. 854-865 ◽  
Author(s):  
Kuangmin Wei ◽  
Sheng Zhu
Keyword(s):  
Cyclic Loading ◽  
Kinematic Hardening ◽  
Complex Loading ◽  
In Situ Measurements ◽  
Coarse Grained ◽  
Loading Conditions ◽  
Elastoplastic Model ◽  
Hardening Model ◽  
Rock Fill

In this research, a simplified rotational kinematic hardening model with the concept of sub-loading was used to predict behaviors of Concrete-Faced Rock-fill Dam under complex loading conditions. The model can overcome the shortcomings of classic elastoplastic model (i.e. soil behaviors under cyclic loading-unloading can be predicted). Elastoplastic formula of the model was presented in detail. Then this model was verified with test results of coarse grained soils, under both monotonic loading and cyclic loading-unloading conditions. This model was also applied to analyze deformation of Shuibuya rock-fill dam, computed results and in-situ measurements are compared. Results showed that computed results were consistent with in-situ measurements in both construction and operation period. Results also showed that permanent deformation that was caused by fluctuations of the reservoir level can also be predicted by this rotational kinematic hardening model.

scholarly journals On the Plastic Strain Accumulation in Notched Bars During High-Temperature Creep Dwell

2020 ◽  
Vol 36 (2) ◽  
pp. 167-176 ◽  
Author(s):  
Daniele Barbera ◽  
Haofeng Chen
Keyword(s):  
High Temperature ◽  
Cyclic Loading ◽  
Plastic Strain ◽  
Kinematic Hardening ◽  
High Temperature Creep ◽  
Strain Accumulation ◽  
Material Models ◽  
Cyclic Loading Condition ◽  
Hardening Material ◽  
Temperature Creep

ABSTRACTStructural integrity plays an important role in any industrial activity, due to its capability of assessing complex systems against sudden and unpredicted failures. The work here presented investigates an unexpected new mechanism occurring in structures subjected to monotonic and cyclic loading at high temperature creep condition. An unexpected accumulation of plastic strain is observed to occur, within the high-temperature creep dwell. This phenomenon has been observed during several full inelastic finite element analyses. In order to understand which parameters make possible such behaviour, an extensive numerical study has been undertaken on two different notched bars. The notched bar has been selected due to its capability of representing a multiaxial stress state, which is a practical situation in real components. Two numerical examples consisting of an axisymmetric v-notch bar and a semi-circular notched bar are considered, in order to investigate different notches severity. Two material models have been considered for the plastic response, which is modelled by both Elastic-Perfectly Plastic and Armstrong-Frederick kinematic hardening material models. The high-temperature creep behaviour is introduced using the time hardening law. To study the problem several results are presented, as the effect of the material model on the plastic strain accumulation, the effect of the notch severity and the mesh element type and sensitivity. All the findings further confirm that the phenomenon observed is not an artefact but a real mechanism, which needs to be considered when assessing off-design condition. Moreover, it might be extremely dangerous if the cyclic loading condition occurs at such a high loading level.

A New Constitutive Model in the Theory of Plasticity—Part I: Theory

1995 ◽  
Vol 117 (4) ◽  
pp. 365-370 ◽  
Author(s):  
W. Jiang
Keyword(s):  
General Solution ◽  
Constitutive Model ◽  
Closed Form ◽  
Yield Surface ◽  
Kinematic Hardening ◽  
Material Response ◽  
Hardening Model ◽  
Theory Of Plasticity

By proposing two rules to regulate the movement of the yield surface, this paper develops a new kinematic hardening model in the theory of plasticity. A closed-form general solution is obtained in the case of linear stress paths, material response under cyclic loadings is discussed, and various tube problems are solved to demonstrate the model.

scholarly journals Combined hardening parameters of steel CK45 under cyclic strain-controlled loading: Calibration methodology and numerical validation

2020 ◽  
Vol 14 (2) ◽  
pp. 6848-6855
Author(s):  
Bahman Paygozar ◽  
S.A Dizaji ◽  
M.A Saeimi Sadigh
Keyword(s):  
Cyclic Loading ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Strain Curve ◽  
Experimental Tests ◽  
Isotropic Hardening ◽  
Cycle Fatigue ◽  
Stress Strain ◽  
Hardening Model ◽  
Combined Hardening

This study is to indicate the methodology of investigating the behavior of materials in the plastic domain while bearing cyclic loading i.e. low cycle fatigue. Materials under such loading, which experience huge amount of plastic deformation, are affected by the hardening or softening effects of loading which should be taken into account in all applications and numerical simulations as well. This work investigates the methodology of obtaining the nonlinear isotropic and kinematic hardening of steel CK45. To find the parameters of the above mentioned combined nonlinear isotropic/kinematic hardening one tensile test as well as three strain-controlled low cycle fatigue tests are carried out to extract the monotonic stress/strain curve and three diagrams of hysteresis curves, respectively. Then, four parameters necessary to simulate the nonlinear isotropic/ kinematic behavior of the material are extracted by means of curve fitting technique using MATLAB software. Afterwards, the accuracy of the data extracted from the experimental tests using the proposed methodology, are verified in a finite element package, ABAQUS, through implementing two user defined subroutines UMAT written in FORTRAN. It is indicated that the computed constants draw stress-strain curves much closer to experimental responses than isotropic hardening model does.  Eventually, the numerical results acquired by simulating the behavior of the sample under cyclic loading with importing the constants, calculated via combined hardening model, to ABAQUS reflects results highly close to the experimentally obtained response of the sample. It means that the procedure used to find the constants is accurate enough and consequently the constants computed are able to be used in both ABAQUS and subroutines.     

scholarly journals Inelastic behavior and destruction of materials under isothermal and non-isothermal, simple and complex loads

2020 ◽  
pp. 107-119
Author(s):  
V. S Bondar ◽  
D. R Abashev
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Cyclic Loading ◽  
Inelastic Deformation ◽  
Elevated Temperatures ◽  
Complex Loading ◽  
Applied Theory ◽  
Inelastic Behavior ◽  
Significant Difference

The paper deals with mathematical modeling of inelastic behavior and destruction of structural materials (steels and alloys) under simple, complex, isothermal and non-isothermal loads in repeated and long-term exposures to thermomechanical loads. The modeling is carried out on the basis of the applied theory of inelasticity, which belongs to the class of flow theories in combined hardening. The main provisions are formulated and a summary of the main equations of the applied theory of inelasticity is given. The material functions closing the applied theory of inelasticity are determined, and the connection of the defining functions with the material ones is given. Further, the results of some original experimental studies are considered, which are compared with the results of calculations based on the applied theory of inelasticity. In all studies, inelastic deformation is performed under conditions repeated and long-term exposures to thermomechanical loads. Inelastic deformation of AL-25 aluminum alloy samples under uniaxial tension-compression under both isothermal and non-isothermal cyclic loading is considered. Inelastic deformation under complex loading along the two-link polyline deformation paths with different deformation rates under high temperature conditions is studied on tubular 30HGSA alloy samples. Inelastic deformation of tubular stainless steel 304 samples under complex loading at elevated temperatures is considered. Soft cyclic loading is performed along two-link stress trajectories with different fracture angles. At the end of the links of the stress trajectory, exposure is carried out for 8 hours. The results of the calculations based on various theories used in the calculations are analyzed. Inelastic deformation and destruction of samples made of 12X18N9 stainless steel under rigid cyclic deformation under both isothermal and non-isothermal loads is considered. The duration of the loading cycle is 4 minutes, which allowed the effects of healing and embrittlement to appear at a high temperature. There is a significant difference (much higher) in the number of cycles to failure in common-phase and anti-phase modes of changes in force strain and temperature.

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