A Physically Motivated Internal State Variable Plasticity/Damage Model Embedded With a Length Scale for Hazmat Tank Cars’ Structural Integrity Applications

2011 ◽  
Author(s):  
Fazle R. Ahad ◽  
Koffi Enakoutsa ◽  
Kiran N. Solanki ◽  
Yustianto Tjipowidjojo ◽  
Douglas J. Bammann
Keyword(s):  
Evolution Equation ◽  
Internal State ◽  
Damage Model ◽  
Mesh Size ◽  
Material Behavior ◽  
Length Scale ◽  
Internal State Variable ◽  
State Variable ◽  
Fe Simulations ◽  
The Impact

In this study, we use a physically-motivated internal state variable plasticity/damage model containing a mathematical length scale to represent the material behavior in finite element (FE) simulations of a large scale boundary value problem. This problem consists of a moving striker colliding against a stationary hazmat tank car. The motivations are (1) to reproduce with high fidelity finite deformation and temperature histories, damage, and high rate phenomena which arise during the impact and (2) to address the pathological mesh size dependence of the FE solution in the post-bifurcation regime. We introduce the mathematical length scale in the model by adopting a nonlocal evolution equation for the damage, as suggested by Pijaudier-Cabot and Bazant (1987) in the context of concrete. We implement this evolution equation into existing implicit and explicit versions of the FE subroutines of the plasticity/failure model. The results of the FE simulations, carried out with the aid of Abaqus/Explicit FE code, show that the material model, accounting for temperature histories and nonlocal damage effects, satisfactorily predicts the damage progression during the tank car impact accident and significantly reduces the pathological mesh size effects.

scholarly journals Modeling the Dynamic Failure of Railroad Tank Cars Using a Physically Motivated Internal State Variable Plasticity/Damage Nonlocal Model

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Fazle R. Ahad ◽  
Koffi Enakoutsa ◽  
Kiran N. Solanki ◽  
Yustianto Tjiptowidjojo ◽  
Douglas J. Bammann
Keyword(s):  
Finite Element ◽  
Evolution Equation ◽  
Internal State ◽  
Mesh Size ◽  
High Rate ◽  
Length Scale ◽  
Internal State Variable ◽  
State Variable ◽  
Nonlocal Evolution Equation ◽  
The Impact

We used a physically motivated internal state variable plasticity/damage model containing a mathematical length scale to idealize the material response in finite element simulations of a large-scale boundary value problem. The problem consists of a moving striker colliding against a stationary hazmat tank car. The motivations are (1) to reproduce with high fidelity finite deformation and temperature histories, damage, and high rate phenomena that may arise during the impact accident and (2) to address the material postbifurcation regime pathological mesh size issues. We introduce the mathematical length scale in the model by adopting a nonlocal evolution equation for the damage, as suggested by Pijaudier-Cabot and Bazant in the context of concrete. We implement this evolution equation into existing finite element subroutines of the plasticity/failure model. The results of the simulations, carried out with the aid of Abaqus/Explicit finite element code, show that the material model, accounting for temperature histories and nonlocal damage effects, satisfactorily predicts the damage progression during the tank car impact accident and significantly reduces the pathological mesh size effects.

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.

Temperature-Dependent Fracture Mechanics-Informed Damage Model for Ceramic Matrix Composites

2021 ◽  
Author(s):  
Travis Skinner ◽  
Aditi Chattopadhyay
Keyword(s):  
Fracture Mechanics ◽  
Internal State ◽  
Damage Model ◽  
Ceramic Matrix ◽  
Model Parameters ◽  
Internal State Variable ◽  
Temperature Dependent ◽  
State Variable ◽  
Initiation And Propagation ◽  
Matrix Damage

Abstract This work presents a temperature-dependent reformulation of a multiscale fracture mechanics-informed matrix damage model previously developed by the authors. In this paper, internal state variable theory, fracture mechanics, and temperature-dependent material properties and model parameters are implemented to account for length scale-specific ceramic matrix composite (CMC) brittle matrix damage initiation and propagation behavior for temperatures ranging from room temperature (RT) to 1200°C. A unified damage internal state variable (ISV) is introduced to capture effects of matrix porosity, which occurs as a result of material diffusion around grain boundaries, as well as matrix property degradation due to matrix crack initiation and propagation. The porosity contribution to the unified damage ISV is related to the volumetric strain, and matrix cracking effects are captured using fracture mechanics and crack growth kinetics. A combination of temperature-dependent material properties and damage model parameters are included in the model to simulate effects of temperature on the deformation and damage behavior of 2D woven C/SiC CMC material systems. Model calibration is performed using experimental data from literature for plain weave C/SiC CMC at RT, 700°C, and 1200°C to determine how damage model parameters change in this temperature range. The nonlinear, temperature-dependent predictive capabilities of the reformulated model are demonstrated for 1000°C using interpolation to obtain expected damage model parameters at this temperature and the predictions are in good agreement with experimental results at 1000°C.

An internal state variable damage model in crystal plasticity

2007 ◽  
Vol 39 (10) ◽  
pp. 941-952 ◽  
Author(s):  
G.P. Potirniche ◽  
M.F. Horstemeyer ◽  
X.W. Ling
Keyword(s):  
Crystal Plasticity ◽  
Internal State ◽  
Damage Model ◽  
Internal State Variable ◽  
State Variable

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 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.

Using Internal State Variable Plasticity to Determine Dynamic Loading History Effects in Manufacturing Processes

2004 ◽  
Author(s):  
Y. B. Guo ◽  
Q. Wen ◽  
M. F. Horstemeyer
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Internal State ◽  
Material Behavior ◽  
Temperature History ◽  
Loading Path ◽  
Internal State Variable ◽  
State Variable ◽  
History Effects ◽  
Deformation Processes

Worked materials in large deformation processes such as forming and machining experience a broad range of strain, strain rate, and temperatures, which in turn affect the flow stress. However, the flow stress also highly depends on many other factors such as strain path, strain rate and temperature history. Only a model that includes all of these pertinent factors is capable of predicting complex stress state in material deformation. In this paper, the commonly used phenomenological plasticity models (Johnson-Cook, Usui, etc.) to characterize material behavior in forming and machining were critically reviewed. Although these models are easy to apply and can describe the general response of material deformation, these models lack the mechanisms to reflect static and dynamic recovery and the effects of load path and strain rate history in large deformation processes. These effects are essential to understand process mechanisms, especially surface integrity of the manufactured products. As such a dislocation-based internal state variable (ISV) plasticity model was used, in which the evolution equations enable the prediction of strain rate history and temperature history effects. These effects can be quite large and cannot be modeled by the equation-of-state models that assume that stress is a unique function of the total strain, strain rate, and temperature, independent of the loading path. The temperature dependence of the hardening and recovery functions results in the prediction of thermal softening during adiabatic temperatures rises, which are common in metal forming and machining. The dynamic mechanical behaviors of three different benchmark work materials, titanium Ti-6Al-4V, AISI 52100 steel (62 HRc), and aluminum 6061-T6, were modeled using the ISV approach. The material constants were obtained by using a nonlinear regression fitting algorithm in which the stress-strain curves from the model were correlated to the experiments at different (extreme) temperatures. Then the capabilities of the determined material constants were examined by comparing the predicted material flow stress with the test data at different temperatures, strains, and strain rate history. The comparison demonstrates that the internal state plasticity model can successfully recover dynamic material behavior at various deformation states including the loading path effect. In addition, thermal softening due to adiabatic deformation was also captured by this approach.

Cutting Mechanics of High Speed Dry Machining of Magnesium-Calcium Biomedical Alloy Using Internal State Variable Plasticity Model

2011 ◽  
Author(s):  
M. Salahshoor ◽  
Y. B. Guo
Keyword(s):  
Mechanical Properties ◽  
Chip Formation ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Internal State ◽  
Material Behavior ◽  
Internal State Variable ◽  
Plasticity Model ◽  
Dry Cutting ◽  
State Variable

Magnesium-Calcium (MgCa) alloys have become attractive orthopedic biomaterials due to their biodegradability, biocompatibility, and congruent mechanical properties with bone tissues. However, process mechanics of machining biomedical MgCa alloys is poorly understood. Mechanical properties of the biomedical magnesium alloy at high strain rates and large strains are determined by using the split-Hopkinson pressure bar testing method. Internal state variable (ISV) plasticity model is implemented to understand the dynamic material behavior under cutting conditions. A finite element simulation model has been developed to study the chip formation during high speed dry cutting of MgCa0.8 (wt %) alloy. Continuous chip formation predicted by the FE simulation is verified by high speed dry face milling of MgCa0.8 using polycrystalline diamond (PCD) inserts. Chip ignition is known as the most hazardous aspect of machining Mg alloys. The predicted temperature distributions may well explain the reason for machining safety of high-speed dry cutting of MgCa0.8 alloy.

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