Comparison of Johnson-Cook Model and an ISV Plasticity Damage Model in Penetration Simulation

2016 ◽  
Author(s):  
Yangqing Dou ◽  
Yucheng Liu ◽  
Youssef Hammi
Keyword(s):  
High Speed ◽  
Internal State ◽  
Damage Model ◽  
Rate Equations ◽  
State Variables ◽  
High Speed Impact ◽  
Internal States ◽  
Penetration Mechanics ◽  
History Of ◽  
Cook Model

This paper compares Johnson-Cook model and an internal state variable (ISV) damage model developed by Bammann and Horstemeyer in simulating damage behavior of materials during penetration process. Bammann and Horstemeyer’s ISV damage model employs internal state variables and their rate equations to capture the evolution of internal states of materials during high speed impact and penetration. From the calculated internal states, observable states or global penetration and perforation response of materials can be decided. Compared to the JC model, the ISV damage model closely reflect history of materials’ mechanical behavior during the penetration and perforation process. Moreover, the damage model links the global impact and penetration performance of the materials to their microstructural evolution, such as the nucleation, growth, and coalescence of micro voids and cracks. Therefore, it possesses an enhanced predicative capability for high speed impact, penetration, and perforation problems. To demonstrate the reliability of the presented ISV model, that model is applied for studying penetration mechanics of aluminum and the numerical results are validated by comparing with simulation results yielded from the Johnson-Cook model as well as analytical results calculated from an existing theoretical model.

Experimental Calibration of ISV Damage Model Constants for Pure Copper for High-Speed Impact Simulation

2016 ◽  
Author(s):  
Yangqing Dou ◽  
Yucheng Liu ◽  
Wilburn Whittington ◽  
Jonathan Miller
Keyword(s):  
High Speed ◽  
Impact Analysis ◽  
Split Hopkinson Pressure Bar ◽  
Internal State ◽  
Pure Copper ◽  
Damage Model ◽  
Hopkinson Pressure Bar ◽  
Experimental Calibration ◽  
High Speed Impact ◽  
The Impact

Coefficients and constants of a microstructure-based internal state variable (ISV) plasticity damage model for pure copper have been calibrated and used for damage modeling and simulation. Experimental stress-strain curves obtained from Cu samples at different strain rate and temperature levels provide a benchmark for the calibration work. Instron quasi-static tester and split-Hopkinson pressure bar are used to obtain low-to-high strain rates. Calibration process and techniques are described in this paper. The calibrated material model is used for high-speed impact analysis to predict the impact properties of Cu. In the numerical impact scenario, a 100 mm by 100 mm Cu plate with a thickness of 10 mm will be penetrated by a 50 mm-long Ni rod with a diameter of 10mm. The thickness of 10 mm was selected for the Cu plate so that the Ni-Cu penetration through the thickness can be well observed through the simulations and the effects of the ductility of Cu on its plasticity deformation during the penetration can be displayed. Also, that thickness had been used by some researchers when investigating penetration mechanics of other materials. Therefore the penetration resistance of Cu can be compared to that of other metallic materials based on the simulation results obtained from this study. Through this study, the efficiency of this ISV model in simulating high-speed impact process is verified. Functions and roles of each of material constant in that model are also demonstrated.

scholarly journals Application of a Microstructure-Based ISV Plasticity Damage Model to Study Penetration Mechanics of Metals and Validation through Penetration Study of Aluminum

2017 ◽  
Vol 2017 ◽  
pp. 1-10
Author(s):  
Yangqing Dou ◽  
Yucheng Liu ◽  
Youssef Hammi ◽  
Wilburn Whittington
Keyword(s):  
Internal State ◽  
Void Nucleation ◽  
Damage Model ◽  
Rate Equations ◽  
Modeling Framework ◽  
Experimental Calibration ◽  
Model Compression ◽  
Penetration Mechanics ◽  
Stress States ◽  
First Time

A developed microstructure-based internal state variable (ISV) plasticity damage model is for the first time used for simulating penetration mechanics of aluminum to find out its penetration properties. The ISV damage model tries to explain the interplay between physics at different length scales that governs the failure and damage mechanisms of materials by linking the macroscopic failure and damage behavior of the materials with their micromechanical performance, such as void nucleation, growth, and coalescence. Within the continuum modeling framework, microstructural features of materials are represented using a set of ISVs, and rate equations are employed to depict damage history and evolution of the materials. For experimental calibration of this damage model, compression, tension, and torsion straining conditions are considered to distinguish damage evolutions under different stress states. To demonstrate the reliability of the presented ISV model, that model is applied for studying penetration mechanics of aluminum and the numerical results are validated by comparing with simulation results yielded from the Johnson-Cook model as well as analytical results calculated from an existing theoretical model.

A Damage Model for Nonlinear Tensile Behavior of Cortical Bone

1999 ◽  
Vol 121 (5) ◽  
pp. 533-541 ◽  
Author(s):  
M. T. Fondrk ◽  
E. H. Bahniuk ◽  
D. T. Davy
Keyword(s):  
Experimental Data ◽  
Cortical Bone ◽  
Internal State ◽  
Damage Model ◽  
Experimental Studies ◽  
Inelastic Strain ◽  
Damage Parameter ◽  
Tensile Behavior ◽  
State Variables ◽  
Bending Loading

To describe the time-dependent nonlinear tensile behavior observed in experimental studies of cortical bone, a damage model was developed using two internal state variables (ISV’s). One ISV is a damage parameter that represents the loss of stiffness. A rule for the evolution of this ISV was defined based on previously observed creep behavior. The second ISV represents the inelastic strain due to viscosity and internal friction. The model was tested by simulating experiments in tensile and bending loading. Using average values from previous creep studies for parameters in the damage evolution rule, the model tended to underestimate the maximum nonlinear strains and to overestimate the nonlinear strain accumulated after load reversal in the tensile test simulations. Varying the parameters for the individual tests produced excellent fits to the experimental data. Similarly, the model simulations of the bending tests could produce excellent fits to the experimental data. The results demonstrate that the 2-ISV model combining damage (stiffness loss) with slip and viscous behavior could capture the nonlinear tensile behavior of cortical bone in axial and bending loading.

A Thermo-Electro-Elasto-Viscoplastic Damage Internal State Variable (ISV) Model for Ductile Metals

2018 ◽  
Author(s):  
Nikolay Dimitrov ◽  
Yucheng Liu ◽  
M. F. Horstemeyer
Keyword(s):  
Internal State ◽  
Deformation Gradient ◽  
Damage Model ◽  
Rate Equations ◽  
Thermodynamic Force ◽  
Practical Implementation ◽  
Internal State Variable ◽  
State Variable ◽  
Simplifying Assumptions ◽  
Future Work

A multiphysics Internal State Variable (ISV) theory that couples the thermoelastoviscoplastic damage model of Bammann-Horstemeyer with electricity-related electromagnetic phenomena is presented in which the kinematics, thermodynamics, and kinetics are internally consistent. An extended multiplicative decomposition of the deformation gradient that accounts for elasticity, plasticity, damage, thermal expansion, electricity, and magnetism is introduced. The different geometrically-affected rate equations are given for each phenomenon after the ISV formalism and have a thermodynamic force pair that acts as an internal stress-like quantity. Guidelines for practical implementation, recommendations for simplifying assumptions, and suggestions for future work supplement the theoretical model. The abstraction of the model can capture the full multi-physics described above; however, the robustness of the model is realized when any of the listed phenomena are not included in the boundary value problem, the model reduces to the previous form — the model will revert to the Bammann-Horstemeyer plasticity-damage ISV model.

A Multiphase Internal State Variable Model With Rate Equations for Predicting Elastothermoviscoplasticity and Damage of Fiber Reinforced Polymer Composites

2017 ◽  
Author(s):  
Ge He ◽  
Yucheng Liu ◽  
D. J. Bammann ◽  
M. F. Horstemeyer
Keyword(s):  
Internal State ◽  
Damage Model ◽  
Matrix Cracking ◽  
Fiber Reinforced Polymer ◽  
Rate Equations ◽  
Internal State Variable ◽  
Fiber Reinforced ◽  
Variable Model ◽  
State Variable ◽  
Reinforced Polymer

This paper agglomerates an Internal State Variable (ISV) model for polymers (Bouvard et al., 2010, 2013) with damage evolution (Horstemeyer and Gokhale, 1999: Horstemeyer et al., 2000; Francis et al., 2014) into a multiphase ISV framework (Rajagopal and Tao, 1995; Bammann et al., 1996) that features a finite strain theoretical framework for Fiber Reinforced Polymer (FRP) composites under various stress states, temperatures, strain rates, and history dependencies. In addition to the inelastic ISVs for the polymer matrix and interphase, new ISVs associated with the interaction between phases are introduced. A scalar damage variable is employed to capture the damage history of such material, which is a result of three damage modes: matrix cracking, fiber breakage, and deterioration of the fiber-matrix interface, and each damage model was well calibrated to the experimental data from Rolland et al., (2016). The constitutive model developed herein arises employing standard postulates of continuum mechanics with the kinematics, thermodynamics, and kinetics being internally consistent.

Studying the effect of a hydrostatic stress/strain reduction factor on damage mechanics of concrete materials

2013 ◽  
Vol 22 (5-6) ◽  
pp. 149-159
Author(s):  
Ziad N. Taqieddin ◽  
George Z. Voyiadjis
Keyword(s):  
Damage Mechanics ◽  
Internal State ◽  
Hydrostatic Stress ◽  
Damage Model ◽  
Reduction Factor ◽  
State Variables ◽  
Elastic Plastic ◽  
Damage Models ◽  
Plastic Damage ◽  
Concrete Materials

AbstractIn the non-linear finite element analysis (NFEA) of concrete materials, continuum damage mechanics (CDM) provides a powerful framework for the derivation of constitutive models capable of describing the mechanical behavior of such materials. The internal state variables of CDM can be introduced to the elastic analysis of concrete to form elastic-damage models (no inelastic strains), or to the elastic-plastic analysis in order to form coupled/uncoupled elastic-plastic-damage models. Experimental evidence that is well documented in literature shows that the susceptibility of concrete to damage and failure is distinguished under deviatoric loading from that corresponding to hydrostatic loading. A reduction factor is usually introduced into a CDM model to reduce the susceptibility of concrete to hydrostatic stresses/strains. In this work, the effect of a hydrostatic stress/strain reduction factor on the performances of two NFEA concrete models will be studied. These two (independently published) models did not provide any results showing such effect. One of these two models is an elastic-damage model, whereas the other is an uncoupled elastic-plastic-damage model. Simulations and comparisons are carried out between the performances of the two models under uniaxial tensile and compressive loading conditions. Simulations are also provided for the uncoupled elastic-plastic-damage model under the following additional loading conditions: biaxial tension and biaxial compression, uniaxial cyclic loading, and varying ratios of triaxial compressive loadings. These simulations clearly show the effect of the reduction factor on the numerically depicted behaviors of concrete materials. To have rational comparisons, the hydrostatic stress reduction factor applied to each model is chosen to be a function of the internal state variables common to both models. Therefore, once the two models are calibrated to simulate the experimental behaviors, their corresponding reduction factors are readily available at every increment of the iterative NFEA procedures.

Damage Coupled With Heat Conduction in Uniaxially Reinforced Composites

1988 ◽  
Vol 55 (3) ◽  
pp. 641-647 ◽  
Author(s):  
Y. Weitsman
Keyword(s):  
Heat Conduction ◽  
Mechanical Response ◽  
Internal State ◽  
Constitutive Relations ◽  
Damage Model ◽  
Irreversible Thermodynamics ◽  
Continuum Damage ◽  
State Variables ◽  
Damage Growth ◽  
Continuum Damage Model

This paper presents a continuum damage model for a unidirectionally reinforced composite based upon fundamental concepts of continuum mechanics and irreversible thermodynamics. Damage is incorporated by two symmetric, second-rank, tensor-valued, internal state variables which represent the total areas of “active” and “passive” cracks contained within a representative material volume element. Constitutive relations are derived for both the mechanical response and heat flux in the presence of damage. It is shown that damage growth contributes to dissipation in the coupled heat conduction process. A specific fracture mechanics solution is employed to relate “microlevel” crack growth processes to “macrolevel” damage growth expressions. This approach lends itself to a probabilistic formulation of the continuum damage model.

A Continuum Damage Model for Viscoelastic Materials

1988 ◽  
Vol 55 (4) ◽  
pp. 773-780 ◽  
Author(s):  
Y. Weitsman
Keyword(s):  
Degrees Of Freedom ◽  
Internal State ◽  
Constitutive Relations ◽  
Damage Model ◽  
Uniaxial Stress ◽  
Continuum Damage ◽  
State Variables ◽  
Viscoelastic Materials ◽  
Continuum Damage Model ◽  
Special Cases

This paper presents a continuum damage model for viscoelastic materials. “Damage” is expressed by two symmetric, second rank tensors which are related to the total areas of “active” and “passive” microcracks within a representative volume element of the multifractured material. Viscoelasticity is introduced through scalar valued internal state variables that represent the internal degrees-of-freedom associated with the motions of long chain polymeric molecules. The constitutive relations are established from basic considerations of continuum mechanics and irreversible thermodynamics, with detailed expressions derived for the case of initially isotropic materials. It is shown that damage causes softening of the material moduli as well as changes in material symmetry. The special cases of uniaxial damage under uniaxial stress and the interaction of damage with moisture diffusion are also considered.

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