Constitutive Description of Temperature-Dependent Nonproportional Cyclic Viscoplasticity

1997 ◽  
Vol 119 (1) ◽  
pp. 12-19 ◽  
Author(s):  
Xian Jie Yang
Keyword(s):  
Evolution Equations ◽  
Kinematic Hardening ◽  
Complex Loading ◽  
Deformation Resistance ◽  
Material Behavior ◽  
Temperature History ◽  
Loading History ◽  
Dependent Behavior ◽  
Proposed Model ◽  
Hardening Rules

This paper is concerned with the constitutive modeling of the temperature history dependent behavior of metallic materials under uniaxial and nonproportional cyclic loadings. In the study, a class of kinematic hardening rules characterized by a decomposition of the total kinematic hardening variable is discussed. A new nonproportionality is defined. In order to consider the influence of complex cyclic loading and temperature histories on materials behavior, an apparent isotropic deformation resistance parameter Qasm is proposed and the evolution equations of the isotropic deformation resistance Q are offered to correlate the memory effect of previous loading history on material behavior. The proposed model is applied to the description of complex cyclic deformation behavior of 1Cr18Ni9Ti stainless steel, and this model gives good results for the prediction of complex tests under complex loading history and at stepwise temperature changes.

Damage-coupled ratcheting behaviors of SA508 Gr.3 steel at room and elevated temperatures: Experiments and simulations

2020 ◽  
Vol 29 (9) ◽  
pp. 1379-1396
Author(s):  
Jun Tian ◽  
Xiaolong Fu ◽  
Xuejiao Shao ◽  
Lu Jiang ◽  
Jian Li ◽  
...  
Keyword(s):  
Path Dependence ◽  
Elevated Temperatures ◽  
Kinematic Hardening ◽  
Cyclic Softening ◽  
Dynamic Strain ◽  
Loading Paths ◽  
Proposed Model ◽  
Series Of Experiments ◽  
Hardening Rules ◽  
Multiaxial Loadings

A series of experiments subjected to uniaxial and non-proportionally multiaxial cyclic loadings were performed to investigate the ratcheting responses of SA508 Gr.3 steel at room and elevated temperatures. The influences of different stress levels and nonproportional loading paths on the damage-coupled ratcheting responses were discussed. From experimental results, cyclic softening characteristic and dynamic strain aging can be observed under cyclic loadings. Moreover, the steel exhibits an obvious nonproportional path-dependence of the damage evolution under multiaxial loading paths. To numerically simulate the ratcheting responses under uniaxial and multiaxial loadings with the extended cyclic plastic model, the damage-coupled variable was introduced into the classic isotropic and nonlinear kinematic hardening rules. Corresponding material parameters could be calibrated from experimental data, and comparisons between experimental and simulated results were performed to validate the proposed model.

Characterization and Modeling of Time-Dependent Behaviour of Braided Packing Rings

2016 ◽  
Author(s):  
Mehdi Kazeminia ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Viscoelastic Behavior ◽  
Material Behavior ◽  
Time Dependent ◽  
Nonlinear Material ◽  
Dependent Behavior ◽  
Sealing Performance ◽  
Proposed Model ◽  
Packing Rings ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic

The sealing performance of packed stuffing boxes used in valves and compressors depends on the ability of the structure to maintain a minimum threshold contact pressure through a sufficient period of time. Packing rings exhibit combined creep and relaxation behavior due to internal disordered porous structure and nonlinear material behavior in addition to the interaction with other structural components. A comprehensive understanding of the time-dependent behavior of packing rings is essential for increasing the sealing performance. In this paper, the time-dependent linear viscoelastic behavior of packing material is constitutively simulated. The experimental investigation is carried out in a special test bench which was designed and developed to study the characteristics of the time-dependent behavior of packing rings. The results show that the proposed model can successfully be exploited to determine the time-dependent behavior of packing rings for application in the design of packed stuffing boxes.

Necessity of Kinematic Strain Hardening in Simulating Impact Events

2017 ◽  
Author(s):  
Sharang Kirloskar ◽  
Gurmeet Singh ◽  
Avinash Kumar
Keyword(s):  
Strain Hardening ◽  
Impact Loading ◽  
High Speed ◽  
Kinematic Hardening ◽  
Material Behavior ◽  
Isotropic Hardening ◽  
Measurement Systems ◽  
Tension And Compression ◽  
Hardening Rules ◽  
Impact Events

Impact events are very high speed and short duration events. Experimental analysis of such events tends to be extremely expensive and challenging to study because of the apparatus and measurement systems required to capture the event. Due to this, impact events are studied extensively through simulations. The ability to simulate these events is a dictating factor for developing better and more efficient designs. Traditionally, loads occurring due to impact events are assumed to monotonically increase and hence pure isotropic strain hardening is sufficient to model the material behavior. However, this assumption doesn’t hold true for all impact events. When the loads caused by an impact do not monotonically increase but instead oscillate causing tension and compression cycles, pure isotropic hardening could lead to unrealistic results. In this work, different strain hardening rules are studied and analyzed for a plate under impact loading. The process to obtain a parameter which sets a realistic combination of isotropic and kinematic strain hardening rules is demonstrated and discussed. Limitations of the existing practice of using isotropic hardening in impact loading cases are studied. An alternative approach to accommodate the kinematic hardening rule into material models using LS-DYNA, a finite element solver, is discussed.

Multiaxial Cyclic Ratcheting in Coiled Tubing—Part II: Experimental Program and Model Evaluation

1999 ◽  
Vol 122 (2) ◽  
pp. 162-167 ◽  
Author(s):  
Radovan Rolovic ◽  
Steven M. Tipton
Keyword(s):  
Internal Pressure ◽  
Constant Pressure ◽  
Material Behavior ◽  
Experimental Program ◽  
Test Machine ◽  
Loading History ◽  
Coiled Tubing ◽  
Proposed Model ◽  
Model Block ◽  
The Mean

An experimental program was conducted to evaluate the plasticity model proposed in a separate paper (Part I). Constant pressure, cyclic bend-straighten tests were performed to identify material parameters required by the analytical model. Block pressure, bend-straighten tests were conducted to evaluate the proposed model. Experiments were performed on full-size coiled tubing samples using a specialized test machine. Two commonly used coiled tubing materials and four specimen sizes were subjected to load histories consisting of bending-straightening cycles with varying levels of internal pressure. It was observed that cyclic ratcheting rates can be reversed without reversing the mean stress, i.e., diametral growth of coiled tubing can be followed by diametral shrinkage even when the internal pressure is kept positive, depending on the loading history. This material behavior is explained in the context of the new theory. The correlation between the predictions and the test data is very good. [S0094-4289(00)00502-8]

Eulerian Framework for Inelasticity Based on the Jaumann Rate and a Hyperelastic Constitutive Relation—Part II: Finite Strain Elastoplasticity

2013 ◽  
Vol 80 (2) ◽  
Author(s):  
Amin Eshraghi ◽  
Hamid Jahed ◽  
Katerina D. Papoulia
Keyword(s):  
Evolution Equations ◽  
Finite Strain ◽  
Kinematic Hardening ◽  
Nonlinear Evolution Equations ◽  
304 Stainless Steel ◽  
Flow Rule ◽  
Hardening Material ◽  
Jaumann Rate ◽  
Proposed Model ◽  
Nonlinear Hardening

An Eulerian rate formulation of finite strain elastoplasticity is developed based on a fully integrable rate form of hyperelasticity proposed in Part I of this work. A flow rule is proposed in the Eulerian framework, based on the principle of maximum plastic dissipation in six-dimensional stress space for the case of J2 isotropic plasticity. The proposed flow rule bypasses the need for additional evolution laws and/or simplifying assumptions for the skew-symmetric part of the plastic velocity gradient, known as the material plastic spin. Kinematic hardening is modeled with an evolution equation for the backstress tensor considering Prager’s yielding-stationarity criterion. Nonlinear evolution equations for the backstress and flow stress are proposed for an extension of the model to mixed nonlinear hardening. Furthermore, exact deviatoric/volumetric decoupled forms for kinematic and kinetic variables are obtained. The proposed model is implemented with the Zaremba–Jaumann rate and is used to solve the problem of rectilinear shear for a perfectly plastic and for a linear kinematic hardening material. Neither solution produces oscillatory stress or backstress components. The model is then used to predict the nonlinear hardening behavior of SUS 304 stainless steel under fixed-end finite torsion. Results obtained are in good agreement with reported experimental data. The Swift effect under finite torsion is well predicted by the proposed model.

Simultaneous and Mixed Stress Relaxation in Tension and Creep in Torsion of 2618 Aluminum

1986 ◽  
Vol 53 (3) ◽  
pp. 529-535 ◽  
Author(s):  
J. L. Ding ◽  
W. N. Findley
Keyword(s):  
Stress Relaxation ◽  
Kinematic Hardening ◽  
Theoretical Models ◽  
Material Behavior ◽  
Time Dependent ◽  
Creep Recovery ◽  
State Variable ◽  
Dependent Behavior ◽  
Stress States ◽  
Tensile Relaxation

The time dependent behavior of 2618-T61 aluminum under mixed loads and constraints (tension relaxation and torsion creep) is investigated. Experiments include tensile relaxation; simultaneous tension relaxation with step changes in torsion creep and reversed torsion; and alternate creep and relaxation. Results were compared with theoretical models developed previously using as input creep and creep recovery data under constant stress states only. Experimental observations were generally well described by strain hardening flow rules. Some failures in describing the material behavior by the state variable approaches (kinematic hardening) are also discussed.

Shakedown Limit Load Determination for a Kinematically Hardening 90-Degree Pipe Bend Subjected to Constant Internal Pressure and Cyclic Bending

2007 ◽  
Author(s):  
Hany F. Abdalla ◽  
Mohammad M. Megahed ◽  
Maher Y. A. Younan
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Plastic Material ◽  
Kinematic Hardening ◽  
Limit Load ◽  
Material Behavior ◽  
Pipe Bend ◽  
Cyclic Bending ◽  
Perfectly Plastic ◽  
Shakedown Limit

A simplified technique for determining the shakedown limit load of a structure employing an elastic-perfectly-plastic material behavior was previously developed and successfully applied to a long radius 90-degree pipe bend. The pipe bend is subjected to constant internal pressure and cyclic bending. The cyclic bending includes three different loading patterns namely; in-plane closing, in-plane opening, and out-of-plane bending moment loadings. The simplified technique utilizes the finite element method and employs small displacement formulation to determine the shakedown limit load without performing lengthy time consuming full cyclic loading finite element simulations or conventional iterative elastic techniques. In the present paper, the simplified technique is further modified to handle structures employing elastic-plastic material behavior following the kinematic hardening rule. The shakedown limit load is determined through the calculation of residual stresses developed within the pipe bend structure accounting for the back stresses, determined from the kinematic hardening shift tensor, responsible for the translation of the yield surface. The outcomes of the simplified technique showed very good correlation with the results of full elastic-plastic cyclic loading finite element simulations. The shakedown limit moments output by the simplified technique are used to generate shakedown diagrams of the pipe bend for a spectrum of constant internal pressure magnitudes. The generated shakedown diagrams are compared with the ones previously generated employing an elastic-perfectly-plastic material behavior. These indicated conservative shakedown limit moments compared to the ones employing the kinematic hardening rule.

Predictions of microtorsional experiments by micropolar plasticity

2005 ◽  
Vol 461 (2053) ◽  
pp. 189-205 ◽  
Author(s):  
Paschalis Grammenoudis ◽  
Charalampos Tsakmakis
Keyword(s):  
Size Effects ◽  
Bauschinger Effect ◽  
Kinematic Hardening ◽  
Circular Cylinders ◽  
Isotropic Hardening ◽  
Gradient Plasticity ◽  
Material Response ◽  
Micropolar Plasticity ◽  
Classical Plasticity ◽  
Hardening Rules

Kinematic hardening rules are employed in classical plasticity to capture the so–called Bauschinger effect. They are important when describing the material response during reloading. In the framework of thermodynamically consistent gradient plasticity theories, kinematic hardening effects were first incorporated into a micropolar plasticity model by Grammenoudis and Tsakmakis. The aim of the present paper is to investigate this model by predicting size effects in torsional loading of circular cylinders. It is shown that kinematic hardening rules compared with isotropic hardening rules, as adopted in the paper, provide more possibilities for modelling size effects in the material response, even if only monotonous loading conditions are considered.

Prediction of Stress Relaxation in Power Plant Components Based on a Constitutive Model

2017 ◽  
Author(s):  
Y. Kostenko ◽  
K. Naumenko
Keyword(s):  
Power Plant ◽  
Stress Relaxation ◽  
Constitutive Model ◽  
Evolution Equations ◽  
Material Behavior ◽  
Assessment Procedure ◽  
Reliable Prediction ◽  
Inelastic Material ◽  
Plant Components

Many power plant components and joint connections are subjected to complex thermo-mechanical loading paths under severe temperature environments over a long period. An important part in the lifetime assessment is the reliable prediction of stress relaxation using improved creep modeling to avoid possible integrity or functionality issues and malfunction in such components. The aim of this work is to analyze the proposed constitutive model for advanced high chromium steels with the goal of predicting stress relaxation over the long term. The evolution equations of the constitutive model for inelastic material behavior are introduced to account for hardening and softening phenomena. The material properties were identified for 9–12%CrMoV steels in the creep range. The model is applied to the stress relaxation analysis of power plant components. The results for long-term assessment, which are encouragingly close to reality, will be presented and discussed. An outlook on further developments of the model and assessment procedure is also provided.

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