scholarly journals A Hyper-Viscoelastic Continuum-Level Finite Element Model of the Spinal Cord Assessed for Transverse Indentation and Impact Loading

2021 ◽  
Vol 9 ◽  
Author(s):  
Aleksander Rycman ◽  
Stewart McLachlin ◽  
Duane S. Cronin
Keyword(s):  
Experimental Data ◽  
Spinal Cord ◽  
Finite Element ◽  
Impact Loading ◽  
Material Properties ◽  
Injury Risk ◽  
Model Parameters ◽  
Pia Mater ◽  
Level Model ◽  
Linear Material

Finite Element (FE) modelling of spinal cord response to impact can provide unique insights into the neural tissue response and injury risk potential. Yet, contemporary human body models (HBMs) used to examine injury risk and prevention across a wide range of impact scenarios often lack detailed integration of the spinal cord and surrounding tissues. The integration of a spinal cord in contemporary HBMs has been limited by the need for a continuum-level model owing to the relatively large element size required to be compatible with HBM, and the requirement for model development based on published material properties and validation using relevant non-linear material data. The goals of this study were to develop and assess non-linear material model parameters for the spinal cord parenchyma and pia mater, and incorporate these models into a continuum-level model of the spinal cord with a mesh size conducive to integration in HBM. First, hyper-viscoelastic material properties based on tissue-level mechanical test data for the spinal cord and hyperelastic material properties for the pia mater were determined. Secondly, the constitutive models were integrated in a spinal cord segment FE model validated against independent experimental data representing transverse compression of the spinal cord-pia mater complex (SCP) under quasi-static indentation and dynamic impact loading. The constitutive model parameters were fit to a quasi-linear viscoelastic model with an Ogden hyperelastic function, and then verified using single element test cases corresponding to the experimental strain rates for the spinal cord (0.32–77.22 s−1) and pia mater (0.05 s−1). Validation of the spinal cord model was then performed by re-creating, in an explicit FE code, two independent ex-vivo experimental setups: 1) transverse indentation of a porcine spinal cord-pia mater complex and 2) dynamic transverse impact of a bovine SCP. The indentation model accurately matched the experimental results up to 60% compression of the SCP, while the impact model predicted the loading phase and the maximum deformation (within 7%) of the SCP experimental data. This study quantified the important biomechanical contribution of the pia mater tissue during spinal cord deformation. The validated material models established in this study can be implemented in computational HBM.

Analytical evaluation of thermally induced residual stresses in ground components

2003 ◽  
Vol 217 (5) ◽  
pp. 471-482 ◽  
Author(s):  
D G Walsh ◽  
A A Torrance ◽  
J Tiberg
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Critical Temperature ◽  
Yield Strength ◽  
Residual Stresses ◽  
Material Properties ◽  
Analytical Evaluation ◽  
Simple Method ◽  
Thermally Induced

Although thermally induced tensile residual stresses have been known to occur in ground components, it has not been possible to predict the critical temperature at which these stresses begin to manifest themselves in the workpiece. In this paper, a model of the formation of thermally induced tensile residual stresses is proposed and a simple method of calculating the critical temperature above which tensile residual stresses occur is developed. The analysis makes use of dimensional methods to characterize the critical temperature. In addition, a formula characterizing the yield strength as a function of temperature was developed. The model was then validated using finite element techniques and some experimental data. The analysis reveals that it is possible to determine the critical temperature above which tensile residual stresses will be manifested based on readily available material properties. A case study illustrates the application of the technique.

Bodner-Partom Constitutive Model and Nonlinear Finite Element Analysis

1990 ◽  
Vol 112 (3) ◽  
pp. 287-291 ◽  
Author(s):  
F. A. Kolkailah ◽  
A. J. McPhate
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Plastic Strain ◽  
Constitutive Model ◽  
Finite Element Model ◽  
Numerical Technique ◽  
Element Model ◽  
Material Behavior ◽  
Model Parameters ◽  
Elastic Plastic

In this paper, results from an elastic-plastic finite-element model incorporating the Bodner-Partom model of nonlinear time-dependent material behavior are presented. The parameters in the constitutive model are computed from a leastsquare fit to experimental data obtained from uniaxial stress-strain and creep tests at 650°C. The finite element model of a double-notched specimen is employed to determine the value of the elastic-plastic strain and is compared to experimental data. The constitutive model parameters evaluated in this paper are found to be in good agreement with those obtained by the other investigators. However, the parameters determined by the numerical technique tend to give response that agree with the data better than do graphically determined parameters previously used. The calculated elastic-plastic strain from the model agreed well with the experimental strain.

AUTOMATED CALIBRATION OF A VOID CLOSURE MODEL FOR HIGH-TEMPERATURE DEFORMATION

2011 ◽  
Vol 03 (01n02) ◽  
pp. 79-90 ◽  
Author(s):  
S. AFSHAN ◽  
D. BALINT ◽  
J LIN ◽  
D FARRUGIA
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
High Temperature ◽  
Search Method ◽  
Temperature Deformation ◽  
Model Parameters ◽  
Trial And Error ◽  
Closure Model ◽  
Gurson Model ◽  
Void Closure

The so-called Gurson model is a well-established micromechanical model of the ductile fracture of porous materials, where the mechanism is void nucleation, growth and coalescence. Although the Gurson model, and particularly its modified form developed by Tvergaard and Needleman, is widely used, its application to void closure has received relatively little attention. The first objective of the current work is to explore the applicability of the Gurson model to void closure. The fixed parameters characterizing the modified Gurson model are not universal and must be calibrated for a particular material, typically by trial and error fitting of finite element (FE) simulations to experimental data. However, the trial and error approach is expensive and time consuming (one test generally corresponds to only one triaxiality level). A novel approach has been developed in the present work to identify the void closure model parameters using a nongradient based optimization search method (pattern search method). Rather than using experimental data for void closure, a series of finite element analyses, one of a representative volume element (RVE) containing a spherical void, and another with an equivalent cell of Gurson–Tvergaard (GT) material, has been performed. Both models have parametric characterizations, enabling simulations under different triaxialities and initial void volume fractions. The numerical results of the discrete void RVE and the GT cell can then be compared and model parameters identified. The new automated method was applied using material properties obtained from high temperature tensile testing of Telby plus steel at 900°C and 1100°C, temperatures in the range of those experienced during a typical steel rolling process. The effect of strain rate on void closure is also investigated using this approach for Telby plus steel.

Nonconformal mesh-based finite element strategy for 3D textile composites

2016 ◽  
Vol 51 (16) ◽  
pp. 2315-2330 ◽  
Author(s):  
B Wucher ◽  
S Hallström ◽  
D Dumas ◽  
T Pardoen ◽  
C Bailly ◽  
...  
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Material Properties ◽  
Three Dimensional ◽  
Textile Composites ◽  
Thermoelastic Properties ◽  
Material Interfaces ◽  
Local Correction ◽  
Finite Element Procedure ◽  
Woven Reinforcement

A finite element procedure is developed for the computation of the thermoelastic properties of textile composites with complex and compact two- and three-dimensional woven reinforcement architectures. The purpose of the method is to provide estimates of the properties of the composite with minimum geometrical modeling effort. The software TexGen is used to model simplified representations of complex textiles. This results in severe yarn penetrations, which prevent conventional meshing. A non-conformal meshing strategy is adopted, where the mesh is refined at material interfaces. Penetrations are mitigated by using an original local correction of the material properties of the yarns to account for the true fiber content. The method is compared to more sophisticated textile modeling approaches and successfully assessed towards experimental data selected from the literature.

An Integrated Musculoskeletal-Finite-Element Model to Evaluate Effects of Load Carriage on the Tibia During Walking

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Chun Xu ◽  
Amy Silder ◽  
Ju Zhang ◽  
Julie Hughes ◽  
Ginu Unnikrishnan ◽  
...  
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Injury Risk ◽  
Load Carriage ◽  
Body Motion ◽  
Bone Biomechanics ◽  
External Loading ◽  
Fe Model ◽  
Loading Conditions ◽  
Reaction Forces

Prior studies have assessed the effects of load carriage on the tibia. Here, we expand on these studies and investigate the effects of load carriage on joint reaction forces (JRFs) and the resulting spatiotemporal stress/strain distributions in the tibia. Using full-body motion and ground reaction forces from a female subject, we computed joint and muscle forces during walking for four load carriage conditions. We applied these forces as physiological loading conditions in a finite-element (FE) analysis to compute strain and stress. We derived material properties from computed tomography (CT) images of a sex-, age-, and body mass index-matched subject using a mesh morphing and mapping algorithm, and used them within the FE model. Compared to walking with no load, the knee JRFs were the most sensitive to load carriage, increasing by as much as 26.2% when carrying a 30% of body weight (BW) load (ankle: 16.4% and hip: 19.0%). Moreover, our model revealed disproportionate increases in internal JRFs with increases in load carriage, suggesting a coordinated adjustment in the musculature functions in the lower extremity. FE results reflected the complex effects of spatially varying material properties distribution and muscular engagement on tibial biomechanics during walking. We observed high stresses on the anterior crest and the medial surface of the tibia at pushoff, whereas high cumulative stress during one walking cycle was more prominent in the medioposterior aspect of the tibia. Our findings reinforce the need to include: (1) physiologically accurate loading conditions when modeling healthy subjects undergoing short-term exercise training and (2) the duration of stress exposure when evaluating stress-fracture injury risk. As a fundamental step toward understanding the instantaneous effect of external loading, our study presents a means to assess the relationship between load carriage and bone biomechanics.

scholarly journals Finite Element Analysis of a Ribbed Roofing Panel under Static Flexure

2018 ◽  
Vol 3 (6) ◽  
pp. 15
Author(s):  
Chinedum Vincent Okafor
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Three Dimensional ◽  
Element Model ◽  
Element Analysis ◽  
Load Carrying ◽  
Dimensional Finite Element ◽  
Linear Material ◽  
Three Dimensional Finite Element ◽  
Static Conditions

This study focuses on analyzing the response of a typical ribbed aluminum panel under flexure. A three dimensional finite element model was developed to stimulate the static flexure behavior. The model is a 2.0m (length) x 1.0m (width) x 0.005m (Thickness) with a rib height of 0.038m, crest width of 0.019m and pan distance at 0.055m between intermediate ribs. The load deflection response of the aluminum panel under different flexural loading condition was stimulated. The linear material properties, displacement, stress and strain captured were discussed under static conditions. From the result obtained, the maximum uniformly distributed load carrying capacity of the ribbed aluminum roofing panel under flexure, considering the linear material properties is 665N.

A Heat Transfer and Solidification Model of Continuous Cast

2010 ◽  
Vol 154-155 ◽  
pp. 1431-1434
Author(s):  
Qi Zhang ◽  
La Dao Yang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Material Properties ◽  
Shell Thickness ◽  
Phase Changes ◽  
Continuous Cast ◽  
Solidification Model ◽  
Temperature Distributions ◽  
Linear Material ◽  
Heat Transfer And Solidification

A model of heat transfer and solidification of continuous cast has been established, including boundary conditions in the mold and spray zones. A finite difference method was used for the numerical simulation. The model calculates the shell thickness and temperature distributions of the slab real time. The importance effect of non-linear material properties of specific heat and thermal conductivity as well as phase changes during solidification is treated. The adequacy of model has been proved by industrial and experimental data. The model can be applied to solve some practical problems in continuous cast.

Finite Element Modeling of Aortic Tissue Using High Speed Experimental Data

2005 ◽  
Author(s):  
Muralikrishna Maddali ◽  
Chirag S. Shah ◽  
King H. Yang
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
High Speed ◽  
Material Model ◽  
Traumatic Rupture ◽  
Aortic Tissue ◽  
Model Parameters ◽  
Fe Model ◽  
Rubber Material ◽  
Material Constants

Traumatic rupture of the aorta (TRA) is responsible for 10% to 20% of motor vehicle fatalities [1]. Both finite element (FE) modeling and experimental investigations have enhanced our understanding of the injury mechanisms associated with TRA. Because accurate material properties are essential for the development of correct and authoritative FE model predictions, the objective of the current study was to identify a suitable material model and model parameters for aorta tissue that can be incorporated into FE aorta models for studying TRA. An Ogden rubber material (Type 77B in LS-DYNA 970) was used to simulate a series of high speed uniaxial experiments reported by Mohan [2] using a dumbbell shaped FE model representing human aortic tissue. Material constants were obtained by fitting model simulation results against experimentally obtained corridors. The sensitivity of the Ogden rubber material model was examined by altering constants G and alpha (α) and monitoring model behavior. One single set of material constants (α = 25.3, G = 0.02 GPa, and μ = 0.6000E-06 GPa) was found to fit uniaxial data at strain rates of approximately 100 s−1 for both younger and older aortic tissue specimens. Until a better material model is derived and other experimental data are obtained, it is recommended that the Ogden material model and associated constants derived from the current study be used to represent aorta tissue properties when using FE methods to investigate mechanisms of TRA.

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