Macro-Micro Biomechanics Finite Element Modeling of Brain Injury Under Concussive Loadings

2016 ◽  
Author(s):  
X. Gary Tan ◽  
Andrzej J. Przekwas ◽  
Raj K. Gupta
Keyword(s):  
Finite Element ◽  
Brain Injury ◽  
White Matter ◽  
Strain Rate ◽  
Material Behavior ◽  
Tau Proteins ◽  
Beam Model ◽  
Strain And Strain Rate ◽  
Starting Point ◽  
Macro Scale

Traumatic brain injury (TBI) occurs in many blunt, ballistic and blast impact events. During trauma axons in the white matter are especially vulnerable to injury due to the rapid mechanical loading of brain. The axonal pathology leads to cytoskeletal failure and disconnection. The microtubules are one of major structural components of the cytoskeleton filamentous network. By bridging the macroscopic forces acting on the whole brain with the cellular and subcellular failure, the macro-micro computational models in both time and space can help us better understand the complex biophysics and elucidate the injury mechanism of both severe and mild TBI (concussion). At the macroscopic scale we developed the high-fidelity anatomical human body finite element model (FEM) to predict intracranial pressures and strain and strain rate fields of brain in the blast event. The macro-scale models and the coupled blast and biomechanics approach were validated against test data of shock wave interacting with a surrogate head in the shock tube. The mechanical deformation of brain tissue was mapped to the white matter tracts to obtain local axonal strain and strain rate for the micromechanical models. We developed the micromechanical FEM of myelinated axons interconnected with the oligodendrocyte by the processes, utilizing a novel beam element free of rotational degrees of freedom (DOFs). The numerical results reveal the possible mechanism of impact-induced axon injury including demyelination, breakup of processes, and axonal varicosity. We also investigate the dynamic response of microtubules bundles under traumatic loading. Different from the commonly discrete bead-spring models, a network of microtubules cross-linked with microtubule-associated-protein (MAP) tau proteins was modeled by the nonlinear beam model. Tau protein is modeled by the rate-dependent bar element for its complicated material behavior. The model considers the rupture of microtubule and the failure of tau-tau interface and tau-microtubule interface. The simulation result of the combined effects of the failure of the cross-linked architecture and elongation and bending of the bundle are possibly correlated to the axonal undulations following traumatic loading observed in the experiments. The developed macro-micro biomechanics models can be used as a starting point for modeling the neurobiology effects and guide the design of novel injury protection strategies.

scholarly journals Embedded axonal fiber tracts improve finite element model predictions of traumatic brain injury

2019 ◽  
Vol 19 (3) ◽  
pp. 1109-1130 ◽  
Author(s):  
Marzieh Hajiaghamemar ◽  
Taotao Wu ◽  
Matthew B. Panzer ◽  
Susan S. Margulies
Keyword(s):  
Traumatic Brain Injury ◽  
Finite Element ◽  
Brain Injury ◽  
Strain Rate ◽  
Brain Tissue ◽  
Brain Injuries ◽  
Characteristic Curve ◽  
Strain And Strain Rate

AbstractWith the growing rate of traumatic brain injury (TBI), there is an increasing interest in validated tools to predict and prevent brain injuries. Finite element models (FEM) are valuable tools to estimate tissue responses, predict probability of TBI, and guide the development of safety equipment. In this study, we developed and validated an anisotropic pig brain multi-scale FEM by explicitly embedding the axonal tract structures and utilized the model to simulate experimental TBI in piglets undergoing dynamic head rotations. Binary logistic regression, survival analysis with Weibull distribution, and receiver operating characteristic curve analysis, coupled with repeated k-fold cross-validation technique, were used to examine 12 FEM-derived metrics related to axonal/brain tissue strain and strain rate for predicting the presence or absence of traumatic axonal injury (TAI). All 12 metrics performed well in predicting of TAI with prediction accuracy rate of 73–90%. The axonal-based metrics outperformed their rival brain tissue-based metrics in predicting TAI. The best predictors of TAI were maximum axonal strain times strain rate (MASxSR) and its corresponding optimal fraction-based metric (AF-MASxSR7.5) that represents the fraction of axonal fibers exceeding MASxSR of 7.5 s−1. The thresholds compare favorably with tissue tolerances found in in–vitro/in–vivo measurements in the literature. In addition, the damaged volume fractions (DVF) predicted using the axonal-based metrics, especially MASxSR (DVF = 0.05–4.5%), were closer to the actual DVF obtained from histopathology (AIV = 0.02–1.65%) in comparison with the DVF predicted using the brain-related metrics (DVF = 0.11–41.2%). The methods and the results from this study can be used to improve model prediction of TBI in humans.

An Efficient Multi-Scale Modeling Method that Reveals Coupled Effects Between Surface Roughness and Roll-Stack Deformation in Cold Sheet Rolling

2021 ◽  
pp. 1-53
Author(s):  
Feng Zhang ◽  
Arif S Malik
Keyword(s):  
Surface Roughness ◽  
Finite Element ◽  
Rough Surface ◽  
Material Behavior ◽  
Sheet Rolling ◽  
Elastic Plastic ◽  
Multi Scale ◽  
Macro Scale ◽  
Surface Contact ◽  
Rough Surface Contact

Abstract In thin-gauge cold rolling of metal sheet, the surface roughness of work-rolls is known to affect the rolled sheet surface morphology, the required rolling load, and the roll wear. While modeling of rough surfaces using statistical asperity theory has been widely applied to problems involving semi-infinite solids, the application of asperity distributions and their elastic-plastic behavior has not been considered in roll-stack models for cold sheet rolling. In this work, a simplified-mixed finite element method (SM-FEM) is combined with statistical elastic-plastic asperity theory to study contact interference and coupling effects between a rough work-roll surface and the roll-stack mechanics in cold sheet rolling. By mixing equivalent rough-surface contact foundations, Hertz foundations, and Timoshenko beam stiffness, an approach is created to efficiently model interactions between the micro-scale asperities and the macro-scale roll-stack deformation. Nonlinearities from elastic-plastic material behavior of the asperities and the sheet, as well as changing contact conditions along the roll length, are also accommodated. Performance of the multi-scale SM-FEM approach is made by comparison to a continuum finite element virtual material model. 3D studies for a 4-high mill reveal new multi-scale coupling behaviors, including non-uniform roughness transfer, and perturbations to the sheet thickness ‘crown’ and contact force profiles. The described multi-scale SM-FEM approach is general and applies to rough surface contact problems involving plates and shear-deformable beams having multiple contact interfaces and arbitrary surface profiles.

Finite Element Analysis and Experimental Study on the Effect of Extrusion Ratio during Hot Extrusion Process of Aluminium Matrix Composites

2017 ◽  
Vol 67 (4) ◽  
pp. 428 ◽  
Author(s):  
Dhanalakshmi Sathishkumar ◽  
P. Sivakumar ◽  
K. Shanmuga Sundaram ◽  
S. Anand
Keyword(s):  
Finite Element ◽  
Strain Rate ◽  
Hot Extrusion ◽  
Extrusion Process ◽  
Fe Analysis ◽  
Extrusion Ratio ◽  
Aluminium Matrix ◽  
Matrix Composites ◽  
Aluminium Matrix Composites ◽  
Strain And Strain Rate

The finite element (FE) analysis on the effect of extrusion process parameter namely, extrusion ratio at different billet temperatures on the plastic strain and strain rate of aluminium matrix composite during hot extrusion process has been dealt. The dynamic explicit FE code in ANSYS 15.0 workbench was used for simulation. The FE analysis was carried out on the SiC reinforced aluminium matrix composites for three extrusion ratios 4:1, 8:1 and 15:1, for the billet temperatures in the range 350 °C - 450 °C in steps of 50 °C. The plastic strain and strain rate were found to increase with increase in the extrusion ratio. A minimum strain and strain rate was found to occur at the billet temperature of 450 °C. The silicon carbide particles reinforced aluminium matrix composites were then extruded at the optimised temperature of 450 °C for various extrusion ratios as mentioned above. The effect of extrusion ratio on the microstructure and surface quality of extruded rod was studied.

Analysis of Heat Transfer and Straightening of Continuous Casting Slab Using 3D Finite Element Method

2011 ◽  
Vol 418-420 ◽  
pp. 1698-1702
Author(s):  
Qing Guo Liu ◽  
Xing Zhong Zhang ◽  
Zheng Yi Jiang ◽  
Yan Chao Sun ◽  
Bao Jun Shi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Finite Element Method ◽  
Finite Element ◽  
Strain Rate ◽  
Three Dimensional ◽  
Three Dimension ◽  
Element Analysis ◽  
Strain And Strain Rate ◽  
Three Dimensional Finite Element ◽  
Element Method

The straightening of curved slab results in a greater straightening strain. During the process of multi-point straightening, the peak value of the straightening strain rate will appear at each straightening point. If the strain rate is too large, the straightening cracks will appear. Solidification and heat transfer of a slab is analyzed and the generation of the solidified shell and the three-dimension temperature field of the slab are calculated by using three-dimensional finite element method (FEM). Based on the finite element analysis of five-point straightening of the curved slab, the strain and strain rate of each straightening point were obtained, which is a base of the analysis of straightening cracks.

EFFECTS OF STRAIN RATE DEPENDENCY OF MATERIAL PROPERTIES IN LOW VELOCITY IMPACT

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1165-1170 ◽  
Author(s):  
HIROFUMI MINAMOTO ◽  
ROBERT SEIFRIED ◽  
PETER EBERHARD ◽  
SHOZO KAWAMURA
Keyword(s):  
Finite Element ◽  
Strain Rate ◽  
Yield Stress ◽  
Coefficient Of Restitution ◽  
Finite Element Simulations ◽  
Material Behavior ◽  
Rate Dependency ◽  
Rate Dependent ◽  
Strain Rate Dependency ◽  
The Impact

Impact processes are often analyzed using the coefficient of restitution which represents the kinetic energy loss during impact. In this paper the effect of strain rate dependency of the yield stress on the coefficient of restitution is investigated experimentally and numerically for the impact of a steel sphere against a steel rod. Finite Element simulations using strain-rate dependent material behavior are carried out. In addition, Finite Element simulations with elastic-plastic material behavior, which ignore the strain rate dependency, are carried out as well as elastic material behavior. Comparisons between the experiments and the simulations using strain-rate dependent material behavior show good agreement, and also prove the strong dependency of the coefficient of restitution on the strain rate dependency of the yield stress for steel. The results from both, the experiments and the simulations show also the strong influence of the wave propagation in the rod on the coefficient of restitution.

Local Variations of Strain and Strain Rate in Roll Bite Region During Rolling of Steels

1998 ◽  
Vol 120 (1) ◽  
pp. 86-96 ◽  
Author(s):  
Ampere A. Tseng ◽  
Shi R. Wang ◽  
A. C. W. Lau
Keyword(s):  
Finite Element ◽  
Cold Rolling ◽  
Strain Rate ◽  
Hot Rolling ◽  
Numerical Approach ◽  
Spatial Variations ◽  
Rate Variation ◽  
Strain And Strain Rate ◽  
Before And After ◽  
Roll Bite

A combined experimental-numerical approach has been developed to quantify the strain rate variation of the workpiece in the roll bite region. In this approach, cold rolling experiments at a production mill were conducted first. Then tensile and microhardness tests were performed on workpieces before and after cold rolling to establish the relationship between the microhardness and plastic strain of the material. Microhardness measurements were also conducted in the roll bite region on a partially cold rolled workpiece. A finite element rolling simulation was performed to predict the spatial variations of the strain and strain rate. Through microhardness matching, it was found that the finite-element predicted strains agree very well with those actually existing in the rolled workpiece. Consequently, the finite-element predicted strain rates, whose time-accumulation directly gave strains which matched the actual strains, were verified. Finally, a finite-element simulation of both cold and hot rolling was conducted to assess the effect of several major rolling parameters on the strain rate variation in the bite region. Results show that the spatial variations of strain rate in the roll bite region are extremely nonuniform for both cold and hot rolling.

Post-Yield Material Characterization for Strain-Based Design

SPE Journal ◽  
2009 ◽  
Vol 14 (01) ◽  
pp. 128-134 ◽  
Author(s):  
Trent M.V. Kaiser
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
Heavy Oil ◽  
Material Characterization ◽  
Material Behavior ◽  
Material Strength ◽  
Standard Material ◽  
Strain And Strain Rate ◽  
Static Conditions

Summary Conventional material specifications and test methods were developed to support load-based designs in which inelastic deformations are relatively small and yield strength is the primary material factor governing design. However, in strain-based designs where substantial portions of the structure soften under post-yield deformation, more detailed characterization of the post-yield material behavior is required. This paper presents a framework for describing the post-yield properties of metals (including strain-rate dependence of yield strength) a testing method for measuring post-yield strength in terms of strain and strain rate, and an analytical basis for extrapolating measured properties to static conditions for strain-based design and quality assurance (QA). Introduction Typical test specifications for determining the mechanical properties of oil-country tubular goods (OCTG) were developed to provide an index of mechanical strength to support common load-based design methods. Advancing recovery techniques impose conditions on many well structures that exceed the limits of these methods and the material characterizations on which they are founded. Among these new techniques are those used to recover heavy oil. While typical conditions in heavy-oil reservoirs appear benign, enhanced-oil-recovery (EOR) methods such as thermal stimulation and ultrahigh sand production create some of the most challenging conditions for well structures. Imposed deformations commonly exceed the yield limit of the material, therefore post-yield material characteristics govern much of the structural response. Industry-standard material tests provide only limited characterization of post-yield behavior, particularly at strain levels near the yield point (both pre- and post-yield). Furthermore, test strain rates can affect the measured material strength significantly. Field loading usually occurs at much lower rates and is then sustained for extended periods. A method for characterizing post-yield material properties is, therefore, desired to adequately support designs for such applications. This paper proposes a new basis for characterizing mechanical steel properties that provides the static strength and stiffness over the post-yield strain range. Relaxation characteristics are interpreted from testing, and local stiffness properties are provided. Although static properties are inferred, the test and interpretation basis allows the tests to be executed in a relatively brief time frame, making it possible to apply the method in QA programs to confirm post-yield properties for strain-based designs. A test apparatus built to implement the material-characterization protocol is presented, and sample results are provided to demonstrate the method.

The Biomechanical Determinants of Concussion: Finite Element Simulations to Investigate Tissue-Level Predictors of Injury During Sporting Impacts to the Unprotected Head

2015 ◽  
Vol 31 (4) ◽  
pp. 264-268 ◽  
Author(s):  
Declan A. Patton ◽  
Andrew S. McIntosh ◽  
Svein Kleiven
Keyword(s):  
Finite Element ◽  
Corpus Callosum ◽  
Strain Rate ◽  
Tissue Level ◽  
Von Mises Stress ◽  
Tolerance Limits ◽  
Stress Strain ◽  
Head Impacts ◽  
Strain And Strain Rate ◽  
Von Mises

Biomechanical studies of concussions have progressed from qualitative observations of head impacts to physical and numerical reconstructions, direct impact measurements, and finite element analyses. Supplementary to a previous study, which investigated maximum principal strain, the current study used a detailed finite element head model to simulate unhelmeted concussion and no-injury head impacts and evaluate the effectiveness of various tissue-level brain injury predictors: strain rate, product of strain and strain rate, cumulative strain damage measure, von Mises stress, and intracranial pressure. Von Mises stress was found to be the most effective predictor of concussion. It was also found that the thalamus and corpus callosum were brain regions with strong associations with concussion. Tentative tolerance limits for tissue-level predictors were proposed in an attempt to broaden the understanding of unhelmeted concussions. For the thalamus, tolerance limits were proposed for a 50% likelihood of concussion: 2.24 kPa, 24.0 s−1, and 2.49 s−1 for von Mises stress, strain rate, and the product of strain and strain rate, respectively. For the corpus callosum, tolerance limits were proposed for a 50% likelihood of concussion: 3.51 kPa, 25.1 s−1, and 2.76 s−1 for von Mises stress, strain rate, and the product of strain and strain rate, respectively.

Interactive Effects of Strain, Strain-Rate and Temperatures on Microstructure Evolution in High Rate Severe Plastic Deformation

2011 ◽  
Vol 702-703 ◽  
pp. 139-142
Author(s):  
Shashank Shekhar ◽  
S. Abolghashem ◽  
S. Basu ◽  
J. Cai ◽  
M. Ravi Shankar
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Strain Rate ◽  
Interactive Effect ◽  
Material Behavior ◽  
High Rate ◽  
Interactive Effects ◽  
Continuous Dynamic Recrystallization ◽  
Deformation Parameters ◽  
Strain And Strain Rate

During high rate severe plastic deformation (HRSPD), strain and strain-rate are not the only external factors that determine microstructural transformations in materials, temperature-rise due to heat generation from deformation processes, also plays an important role. Temperature may influence the microstructure directly by controlling grain growth kinetics and it may also have an indirect effect through the interactive effect on material behavior, which in turn, influences strain and strain-rate parameters. This complex thermomechanics of HRSPD can lead to myriad of microstructure and consequently, material properties and phenomenon. These deformation parameters can be utilized as a ‘fingerprint’ for the resulting microstructure, and the properties and phenomenon related to it. Here, we capture some of these microstructural transformations by relating grain and sub-grain sizes, to the deformation parameters. In doing so, we find evidence of continuous dynamic recrystallization operative under these HRSPD conditions, where the interplay of strain, strain rate and temperatures offer varying degrees of multimodality in the grain-size distributions.

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