Analysis and Application of a Coupled Thermoviscoplasticity Theory

1990 ◽  
Vol 57 (4) ◽  
pp. 828-835 ◽  
Author(s):  
H. Ghoneim
Keyword(s):  
Cyclic Loading ◽  
Constitutive Equation ◽  
Internal State ◽  
Internal State Variable ◽  
Strain Rates ◽  
Finite Element Program ◽  
Coupled Equations ◽  
State Variable ◽  
Different Temperatures ◽  
Element Program

Coupled thermoviscoplasticity equations are developed based on the rational theory of thermodynamics. A power-form internal state variable constitutive equation is proposed. Limitation of the proposed constitutive equation is discussed and simulation results of cyclic loading of 1070 steel at different temperatures and strain rates are presented. The developed coupled equations and the proposed constitutive equation are implemented into a finite element program which is used to investigate the thermomechanical problem of cyclic loading of a constrained-ended cylinder.

Dynamic Material Behavior Modeling Using Internal State Variable Plasticity and Its Application in Hard Machining Simulations

2005 ◽  
Vol 128 (3) ◽  
pp. 749-759 ◽  
Author(s):  
Y. B. Guo ◽  
Q. Wen ◽  
K. A. Woodbury
Keyword(s):  
Internal State ◽  
Kinematic Hardening ◽  
Material Behavior ◽  
Machining Process ◽  
Hard Machining ◽  
Internal State Variable ◽  
Strain Rates ◽  
Material Constants ◽  
State Variable ◽  
Jc Model

Work materials experience large strains, high strain rates, high temperatures, and complex loading histories in machining. The problem of how to accurately model dynamic material behavior, including the adiabatic effect is essential to understand a hard machining process. Several conventional constitutive models have often been used to approximate flow stress in machining analysis and simulations. The empirical or semiempirical conventional models lack mechanisms for incorporating isotropic/kinematic hardening, recovery, and loading history effects. In this study, the material constants of AISI 52100 steel (62 HRc) were determined for both the Internal State Variable (ISV) plasticity model and the conventional Johnson-Cook (JC) model. The material constants were obtained by fitting the ISV and JC models using nonlinear least square methods to same baseline test data at different strains, strain rates, and temperatures. Both models are capable of modeling strain hardening and thermal softening phenomena. However, the ISV model can also accommodate the adiabatic and recovery effects, while the JC model is isothermal. Based on the method of design of experiment, FEA simulations and corresponding cutting tests were performed using the cutting tool with a 20 deg chamfer angle. The predicted chip morphology using the ISV model is consistent with the measured chips, while the JC model is not. The predicted temperatures can be qualitatively verified by the subsurface microstructure. In addition, the ISV model gave larger subsurface von Mises stress, plastic strain, and temperature compared with those by the JC model.

A Comparative Study of the Response of Double Shearing and Hypoplastic Models

2002 ◽  
Author(s):  
Huaning Zhu ◽  
Morteza M. Mehrabadi ◽  
Mehrdad Massoudi
Keyword(s):  
Cyclic Loading ◽  
Mechanical Response ◽  
Constitutive Relations ◽  
Constitutive Models ◽  
Shear Loading ◽  
Biaxial Compression ◽  
Finite Element Program ◽  
Cyclic Shear ◽  
Hypoplastic Model ◽  
Element Program

The principal objective of this paper is to compare the mechanical response of a double shearing model with that of a hypoplastic model under biaxial compression and under cyclic shear loading. As the origins and nature of these two models are completely different, it is interesting to compare the predictions of these two models. The constitutive relations of the double shearing and the hypoplastic models are implemented in the finite element program ABACUS/Explicit. It is found that the hypoplastic and the double shearing constitutive models both show strong capability in capturing the essential behavior of granular materials. In particular, under the condition of non-cyclic loading, the stress ratio and void ratio predictions of the double shearing and the hypoplastic models are relatively close, while under the condition of cyclic loading, the predictions of these models are quite different. It is important to note that in the double shearing model employed in this comparison the shear rates on the two slip systems are assumed to be equal. Hence, the conclusions derived in this comparison pertain only to this particular double shearing model. Similarly, the hypoplasticity model considered here is that proposed by Wu, et al. [30] and the conclusions reached here pertain only to this particular hypoplasticity model.

Constitutive Modeling of Beta Titanium Alloy Ti-10V-4.5Fe-1.5Al during Hot Deformation Process

2012 ◽  
Vol 510 ◽  
pp. 729-733
Author(s):  
Feng Bo Han ◽  
Jin Shan Li ◽  
Hong Chao Kou ◽  
Bin Tang ◽  
Min Jie Lai ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Dislocation Density ◽  
Internal State ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Model Parameters ◽  
Internal State Variable ◽  
Dislocation Interaction ◽  
State Variable

A constitutive model using dislocation density rate as an internal state variable has been proposed for hot working of β titanium alloy in this paper. The β phase was only taken into consideration during high temperature deformation. The solution strengthening and dislocation interaction were included in the constitutive equations. The strength coefficient was determined by equivalent vanadium content, Veq, which was calculated according to the alloy constituent. A Kocks-Mecking model was adopted to describe the variation of dislocation density. The constitutive relationship of a β titanium alloy Ti-10V-4.5Fe-1.5Al for high temperature deformation was established using the internal-state-variable based model. Model parameters were determined by the genetic algorithm based objective optimization method. The predicted results agree fairly well with the experimental value.

scholarly journals Formulation of a macroscale corrosion damage internal state variable model

2014 ◽  
Vol 51 (6) ◽  
pp. 1235-1245 ◽  
Author(s):  
Christopher A. Walton ◽  
M.F. Horstemeyer ◽  
Holly J. Martin ◽  
D.K. Francis
Keyword(s):  
Internal State ◽  
Corrosion Damage ◽  
Internal State Variable ◽  
Variable Model ◽  
State Variable ◽  
State Variable Model
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