Mesoscale Simulation-based Parametric Study of Damage Potential in Brain Tissue Using Hyperelastic and Internal State Variable Models

2021 ◽  
Author(s):  
Ge He ◽  
Lei Fan ◽  
Yucheng Liu
Keyword(s):  
Finite Element ◽  
Brain Tissue ◽  
Internal State ◽  
Stress Triaxiality ◽  
Local Maximum ◽  
Internal State Variable ◽  
State Variable ◽  
Brain Lobe ◽  
Von Mises ◽  
The Brain

Abstract Two-dimensional mesoscale finite element analysis (FEA) of a multi-layered brain tissue was performed to calculate the damage related average stress triaxiality and local maximum von Mises strain in the brain. The FEA was integrated with rate dependent hyperelastic and internal state variable (ISV) models respectively describing the behaviors of wet and dry brain tissues. Using the finite element results, a statistical method of design of experiments (DOE) was utilized to independently screen the relative influences of seven parameters related to brain morphology (sulcal width/depth, gray matter (GM) thickness, cerebrospinal fluid (CSF) thickness and brain lobe) and loading/environment conditions (strain rate and humidity) with respect to the potential damage growth/coalescence in the brain tissue. The results of the parametric study illustrated that the GM thickness and humidity were the two most crucial parameters affecting average stress triaxiality. For the local maximum von Mises strain at the depth of brain sulci, the brain lobe/region was the most influential factor. The conclusion of this investigation gives insight for the future development and refinement of a macroscale brain damage model incorporating information from lower length scale

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 Multiscale Analysis of Void Coalescence in Nickel

2006 ◽  
Vol 129 (1) ◽  
pp. 94-104 ◽  
Author(s):  
M. K. Jones ◽  
M. F. Horstemeyer ◽  
A. D. Belvin
Keyword(s):  
Finite Element ◽  
Internal State ◽  
Three Dimensional ◽  
Finite Element Simulations ◽  
Void Coalescence ◽  
Internal State Variable ◽  
State Variable ◽  
Dimensional Finite Element ◽  
Void Geometry ◽  
Versus Strain

An internal state variable void coalescence equation developed by Horstemeyer, Lathrop, Gokhale, and Dighe (2000, Theor. Appl. Fract. Mech., 33(1), pp. 31–47) that comprises void impingement and void sheet mechanisms is updated based on three-dimensional micromechanical simulations and novel experiments. This macroscale coalescence equation, developed originally from two-dimensional finite element simulations, was formulated to enhance void growth. In this study, three-dimensional micromechanical finite element simulations were employed using cylindrical and spherical void geometries in nickel that were validated by experiments. The number of voids, void orientation, and void spacing were all varied and tested and simulated under uniaxial loading conditions. The micromechanical results showed excellent agreement with experiments in terms of void volume fractions versus strain and local void geometry images. Perhaps more importantly, the macroscale internal state variable void coalescence equation did not require a functional form change but just a coefficient value modification.

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