Pseudo 3D RVE Based Finite Element Simulation on White Matter

2012 ◽  
Author(s):  
Yi Pan ◽  
Vivak Patel ◽  
Assimina A. Pelegri ◽  
David I. Shreiber
Keyword(s):  
Finite Element ◽  
White Matter ◽  
Spinal Cord Injuries ◽  
Axonal Injury ◽  
Mechanical Strain ◽  
Element Model ◽  
Tissue Level ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Brain White Matter

Axonal injury represents a critical target for traumatic brain and spinal cord injuries prevention and treatment. Finite element head models are often used to predict brain injury caused by mechanical loading exerted on the head. Many studies have been attempted to understand injury mechanisms and to define mechanical parameters of axonal injury. Mechanical strain has been identified as the proximal cause of axonal injury. Since the microstructure of the brain white matter is locally oriented, the stress and strain fields are highly axon orientation dependent. The accuracy of the finite element simulations depends not only on correct determination of the material properties but also on precise depiction of the tissues’ microstructure (microscopic level). We applied a finite element method and a mircomechanics approach to simulate the kinematics of axon, which was developed according to experimental data, and found that the degree of coupling between the axons and surrounding cells within the tissue will affect the behavior of the tissue. In this study, the finite element model and the kinematic axonal model are applied to the Representative Volume Element (RVE) of central nervous system (CNS) white matter to investigate the tissue level mechanical behavior. The uniaxial tensile test on the white matter tissue will be presented as an example using the RVE.

MULTISCALE COMPUTATIONAL EVALUATION OF ELASTO-VISCOPLASTIC DEFORMATION BEHAVIOR OF AMORPHOUS POLYMER CONTAINING MICROSCOPIC HETEROGENEITY DURING UNIAXIAL TENSILE TEST

2010 ◽  
Vol 02 (03n04) ◽  
pp. 235-255 ◽  
Author(s):  
MAKOTO UCHIDA ◽  
NAOYA TADA
Keyword(s):  
Finite Element ◽  
Deformation Behavior ◽  
Volume Fraction ◽  
Amorphous Polymer ◽  
Element Model ◽  
Strength Distribution ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Viscoplastic Deformation ◽  
Heterogeneous Microstructures

The two-scale elasto-viscoplastic deformation behavior of amorphous polymer was investigated using the large deformation finite element homogenization method. In order to enable a large time increment for the simulation step in the plastic deformation stage, the tangent modulus method is introduced into the nonaffine molecular chain network theory, which is used to represent the deformation behavior of pure amorphous polymer. Two kinds of heterogeneous microstructures were prepared in this investigation. One was the void model, which contains uniformly or randomly distributed voids, and the other was the heterogeneous strength (HS) model, which contains a distribution of initial shear strength. In the macroscopic scale, initiation and propagation processes of necking during uniaxial tension were considered. The macroscopic nominal stress–strain relation was strongly characterized by the volume fraction and distribution of voids for the void model and by the width of the strength distribution for the HS model. Non-uniform deformation behaviors in microscopic and macroscopic scales are closely related to each other for amorphous polymers because continuous stretching and hardening in the localized zone of the microstructure brings about an increase in macroscopic deformation resistance. Furthermore, computational results obtained from the homogenization model are compared to those obtained from the full-scale finite element model, and the effect of the scale difference between microscopic and macroscopic fields is discussed.

Emulating the Interfacial Kinematics of CNS White Matter With Finite Element Techniques

2011 ◽  
Author(s):  
Yi Pan ◽  
Assimina A. Pelegri ◽  
David I. Shreiber
Keyword(s):  
Finite Element ◽  
White Matter ◽  
Soft Tissues ◽  
Axonal Injury ◽  
Mechanical Strain ◽  
Finite Element Models ◽  
Correct Determination ◽  
The Central Nervous System ◽  
Primary Trauma

Axonal injury represents a critical target for TBI and SCI prevention and treatment. Mechanical strain has been identified as the proximal cause of axonal injury, while secondary ischaemic and excitotoxic insults associated with the primary trauma potentially exacerbate the structural and functional damage. Many studies have been attempted to identify the states of stress and strain in white matter using animal and finite element models. These material models employed in finite element simulations of the central nervous system (CNS) of soft tissues heavily depend on phenomenological representations. The accuracy of these simulations depends not only on correct determination of the material properties but also on precise depiction of the tissues’ microstructure.

Analysis on Oil Extraction Progressing Cavity Pump Three-Dimensional Finite Element Model

2014 ◽  
Vol 644-650 ◽  
pp. 670-673
Author(s):  
Guo You Han ◽  
Ming Qi Wang ◽  
Yu Hou ◽  
Qiang Li
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Finite Element Model ◽  
Fluid Pressure ◽  
Three Dimensional ◽  
Element Model ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Analysis Model ◽  
Element Analysis

The finite element analysis of PCP involves three nonlinear of geometry, material and contact, and the load of PCP is diversity, leading to it difficult to establish the finite element model and calculate by finite method. This article takes GLB120-27 as an example, to establish 3D solid model of PCP by using SolidWorks; to determine M-R model constant of stator rubber by using the data of uniaxial tensile test: to separate the seal band from the stator chamber by using Boolean operation and set up contact pairs, to achieve the correct simulation of stator chamber fluid pressure; to correctly simulate the interference fit between stator and rotor through setting correlation parameters; to establish 3D finite element analysis model and verify the correctness by using the experiment data of hydraulic characteristics of PCP.

A Finite Element Model for Estimating Axonal Damage in Traumatic Brain Injury

2012 ◽  
Author(s):  
Rika M. Wright ◽  
K. T. Ramesh
Keyword(s):  
Traumatic Brain Injury ◽  
Finite Element ◽  
Brain Injury ◽  
White Matter ◽  
Finite Element Model ◽  
Axonal Injury ◽  
Diffuse Axonal Injury ◽  
Element Model ◽  
Cellular Level ◽  
The Brain

There has been an ongoing effort to reduce the occurrence of sports-related traumatic brain injury. These injuries are caused by an impact to the head and often lead to the damage of neural axons in the brain. This type of damage is classified as diffuse axonal injury (DAI) or traumatic axonal injury (TAI) [1]. One of the difficulties in studying the progression of axonal injury is that the structural signature of DAI cannot be readily visualized with conventional medical imaging modalities since the damage occurs at the cellular level [2]. This also makes the injury difficult to diagnose. Many researchers have turned to finite element (FE) models to study the development of diffuse axonal injury. FE models provide a means for observing the mechanical process of injury development from the loads to the head at the macroscale to the damage that results at the cellular level. However, for a finite element model to be a viable tool for studying DAI, the model must be able to accurately represent the behavior of the brain tissue, and it must be able to accurately predict injury. In this work, we address both of these issues in an effort to improve the material models and injury criteria used in current FE models of TBI. We represent the white matter with an anisotropic, hyper-viscoelastic constitutive model, incorporate the microstructure of the white matter through the use of diffusion tensor imaging (DTI), and estimate injury using an axonal strain injury (ASI) criterion (Figure 1). We also develop a novel method to quantify the degree of axonal damage in the fiber tracts of the brain.

scholarly journals Numerical Modeling and Experimental Characterization of Elastomeric Pads Bonded in a Conical Spring under Multiaxial Loads and Pre-Compression

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Debora Francisco Lalo ◽  
Marcelo Greco ◽  
Matias Meroniuc
Keyword(s):  
Finite Element ◽  
Test Data ◽  
Complex Geometry ◽  
Experimental Tests ◽  
Element Model ◽  
Initial Guess ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Multiaxial Loading ◽  
Fitting Procedure

Elastomeric components are widely used in the engineering field since their mechanical properties can vary according to a specific condition, enabling their applications under large deformations and multiaxial loading. In this context, the present study seeks to investigate the main challenges involved in the finite element hyperelasticity simulation of rubber-like material components under different cases of multiaxial loading and precompression. The complex geometry of a conical rubber spring was chosen to deal with several deformation modes; this component is in the suspension system placed between the frame and the axle for railway vehicles. The framework of this study provides the correlation between axial and radial stiffness under precompression obtained by experimental tests in prototypes and virtual modeling obtained through a curve fitting procedure. Since the material approaches incompressibility, different shape functions were adopted to describe the fields of pressure and displacements according to the finite element hybrid formulation. The material parameters were accurately adjusted through an optimization algorithm implemented in Python program language which calibrates the finite element model according to the prototype test data. However, as an initial guess, the proper constitutive model and its parameters were first defined based only on the uniaxial tensile test data, since this test is easy to perform and well understood. The validation of the simulation results in comparison with the experimental data demonstrated that care should be given when the same component is subjected to different multiaxial loading cases.

Brain White Matter Model of Orthotropic Viscoelastic Properties in Frequency Domain

2019 ◽  
Author(s):  
Xuehai Wu ◽  
John G. Georgiadis ◽  
Assimina A. Pelegri
Keyword(s):  
Finite Element ◽  
White Matter ◽  
Finite Element Model ◽  
Frequency Domain ◽  
Material Properties ◽  
Viscoelastic Properties ◽  
Diffusion Mri ◽  
Element Model ◽  
Brain White Matter ◽  
Macro Scale

Abstract Finite element analysis is used to study brain axonal injury and develop Brain White Matter (BWM) models while accounting for both the strain magnitude and the strain rate. These models are becoming more sophisticated and complicated due to the complex nature of the BMW composite structure with different material properties for each constituent phase. State-of-the-art studies, focus on employing techniques that combine information about the local axonal directionality in different areas of the brain with diagnostic tools such as Diffusion-Weighted Magnetic Resonance Imaging (Diffusion-MRI). The diffusion-MRI data offers localization and orientation information of axonal tracks which are analyzed in finite element models to simulate virtual loading scenarios. Here, a BMW biphasic material model comprised of axons and neuroglia is considered. The model’s architectural anisotropy represented by a multitude of axonal orientations, that depend on specific brain regions, adds to its complexity. During this effort, we develop a finite element method to merge micro-scale Representative Volume Elements (RVEs) with orthotropic frequency domain viscoelasticity to an integrated macro-scale BWM finite element model, which incorporates local axonal orientation. Previous studies of this group focused on building RVEs that combined different volume fractions of axons and neuroglia and simulating their anisotropic viscoelastic properties. Via the proposed model, we can assign material properties and local architecture on each element based on the information from the orientation of the axonal traces. Consecutively, a BWM finite element model is derived with fully defined both material properties and material orientation. The frequency-domain dynamic response of the BMW model is analyzed to simulate larger scale diagnostic modalities such as MRI and MRE.

On the Transversely Isotropic, Hyperelastic Response of CNS white Matter Using a Hybrid Approach

2020 ◽  
Author(s):  
Yi Pan ◽  
David Shreiber ◽  
Assimina Pelegri
Keyword(s):  
Experimental Data ◽  
White Matter ◽  
Hybrid Approach ◽  
Strain Energy Function ◽  
Transversely Isotropic ◽  
Element Model ◽  
Shear Loading ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Hyperelastic Model

Abstract A numerical and experimental hybrid approach is developed to study the constitutive behavior of the central nervous system white matter. A published transversely isotropic hyperelastic strain energy function is reviewed and used to determine stress-strain relationships for three idealized, simple loading scenarios. The proposed constitutive model is simplified to a three-parameter hyperelastic model by assuming the white matter's incompressibility. Due to a lack of experimental data in all three loading scenarios, a finite element model that accounts for micro-structural axons and their kinematics is developed to simulate behaviors in simple shear loading scenarios to supplement existing uniaxial tensile test data. The parameters of the transversely isotropic hyperelastic material model are determined regressively using the hybrid data. The results highlight that a hybrid numerical virtual test coupled with experimental data, can determine the transversely isotropic hyperelastic model. Besides, it is noted that the model is not limited to small strains, but it is also applied to large deformations.

scholarly journals 3D-Finite element modeling of lead rubber bearing using high damping material

2019 ◽  
Vol 276 ◽  
pp. 01013
Author(s):  
Ahmad Basshofi Habieb ◽  
Tavio Tavio ◽  
Gabriele Milani ◽  
Usman Wijaya
Keyword(s):  
Finite Element ◽  
Shear Behaviour ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Fe Model ◽  
Rubber Material ◽  
Isolation System ◽  
Cyclic Shear ◽  
Rubber Bearing ◽  
Lead Rubber Bearing

Lead Rubber Bearing (LRB) has been widely applied for seismic protection of mid and high-rise buildings around the world. Its excellent energy dissipation becomes the most important aspect of this isolation system thanks to the plasticity and recovery behavior of the lead core. Aiming to develop a deeper knowledge on the behavior of LRB’s, a 3D detailed finite element (FE) modeling is performed in Abaqus FE software. Some important parameters involved in the model are plasticity of the lead core and hyper-elasticity and viscosity of the rubber material. The parameters for rubber material are derived from the results of experimental works in the laboratory, including uniaxial tensile test and relaxation test. The bearing model is then subjected to a cyclic shear-test under constant vertical load. The result of the 3D-FE model is then compared with the analytic-Abaqus model for LRB isolators, developed in the literature. Finally, both 3D-FE model and analytic model result in a good agreement on the shear behaviour of the presented LRB.

Microstructural Hyperelastic Characterization of Brain White Matter in Tension

2019 ◽  
Author(s):  
Mohammadreza Ramzanpour ◽  
Mohammad Hosseini-Farid ◽  
Mariusz Ziejewski ◽  
Ghodrat Karami
Keyword(s):  
Finite Element ◽  
White Matter ◽  
Human Brain ◽  
Volume Fraction ◽  
Fibrous Composite ◽  
Diffuse Axonal Injury ◽  
Stiffness Ratio ◽  
Fibrous Composite Material ◽  
Brain White Matter ◽  
The Brain

Abstract Axons as microstructural constituent elements of brain white matter are highly oriented in extracellular matrix (ECM) in one direction. Therefore, it is possible to model the human brain white matter as a unidirectional fibrous composite material. A micromechanical finite element model of the brain white matter is developed to indirectly measure the brain white matter constituents’ properties including axon and ECM under tensile loading. Experimental tension test on corona radiata conducted by Budday et al. 2017 [1] is used in this study and one-term Ogden hyperelastic constitutive model is applied to characterize its behavior. By the application of genetic algorithm (GA) as a black box optimization method, the Ogden hyperelastic parameters of axon and ECM minimizing the error between numerical finite element simulation and experimental results are measured. Inverse analysis is conducted on the resultant optimized parameters shows high correlation of coefficient (>99%) between the numerical and experimental data which verifies the accuracy of the optimization procedure. The volume fraction of axons in porcine brain white matter is taken to be 52.7% and the stiffness ratio of axon to ECM is perceived to be 3.0. As these values are not accurately known for human brain white matter, we study the material properties of axon and ECM for different stiffness ratio and axon volume fraction values. The results of this study helps to better understand the micromechanical structure of the brain and micro-level injuries such as diffuse axonal injury.

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