Investigation of Stress Wave Propagation in Brain Tissues Through the Use of Finite Element Method

2010 ◽  
Author(s):  
Biaobiao Zhang ◽  
W. Steve Shepard ◽  
Candace L. Floyd
Keyword(s):  
Finite Element ◽  
Wave Propagation ◽  
Brain Injury ◽  
Stress Wave ◽  
Brain Research ◽  
Complex Structure ◽  
Stress Wave Propagation ◽  
Wave Loads ◽  
The Impact ◽  
The Brain

Because axons serve as the conduit for signal transmission within the brain, research related to axon damage during brain injury has received much attention in recent years. Although myelinated axons appear as a uniform white matter, the complex structure of axons has not been thoroughly considered in the study of fundamental structural injury mechanisms. Most axons are surrounded by an insulating sheath of myelin. Furthermore, hollow tube-like microtubules provide a form of structural support as well as a means for transport within the axon. In this work, the effects of microtubule and its surrounding protein mediums inside the axon structure are considered in order to obtain a better understanding of wave propagation within the axon in an attempt to make progress in this area of brain injury modeling. By examining axial wave propagation using a simplified finite element model to represent microtubule and its surrounding proteins assembly, the impact caused by stress wave loads within the brain axon structure can be better understood. Through conducting a transient analysis as the wave propagates, some important characteristics relative to brain tissue injuries are studied.

Wave Propagation in an Elastic Rod Exhibiting Internal Coulomb Friction, Considered as a Model for a Ring Spring

1956 ◽  
Vol 23 (3) ◽  
pp. 367-372
Author(s):  
E. H. Lee ◽  
A. J. Wang
Keyword(s):  
Wave Propagation ◽  
Stress Wave ◽  
Coulomb Friction ◽  
Stress Wave Propagation ◽  
Infinite Length ◽  
Input Energy ◽  
Elastic Rod ◽  
Total Input ◽  
Conical Bearing ◽  
The Impact

Abstract The problem of stress-wave propagation in a ring spring is considered. A ring spring consists of rings placed normal to the spring axis with alternate internal and external conical bearing surfaces. The friction between these surfaces causes a loading-unloading relation which is strongly irreversible, leading to marked energy absorption for oscillatory stressing. The attenuation of a pulse of stress is analyzed in detail as it is propagated down a spring of infinite length. The influence of certain spring characteristics is evaluated. Concentration of the absorption of the total input energy is found in the region of the impact end of the spring, and particular examples are presented.

Experimental investigation of stress wave propagation in standing trees

Holzforschung ◽  
2011 ◽  
Vol 65 (5) ◽  
Author(s):  
Houjiang Zhang ◽  
Xiping Wang ◽  
Juan Su
Keyword(s):  
Wave Propagation ◽  
Stress Wave ◽  
Wave Energy ◽  
Structural Defects ◽  
Stress Wave Propagation ◽  
Tree Trunk ◽  
Wave Fronts ◽  
Contour Maps ◽  
Standing Trees ◽  
The Impact

Abstract The objective of this study was to investigate how a stress wave travels in a standing tree as it is introduced into the tree trunk through a mechanical impact. A series of stress wave time-of-flight (TOF) data were obtained from three freshly-cut red pine (Pinus resinosa Ait.) logs by means of a two-probe stress wave timer. Two-dimensional (2D) and three-dimensional (3D) stress wave contour maps were constructed based on the experimental data using a commercial software. These stress wave contour maps represent the wave fronts in a time sequence, illustrating the flow of stress wave energy within a log. The analysis of TOF data and wave fronts indicates that stress wave propagation in standing trees is affected by tree diameter, travel distance, and internal wood conditions (wood properties and structural defects). When a stress wave is introduced into a tree trunk from a point source, it initially propagates in the impact direction as a 3D wave. Then the flow of the stress wave energy gradually changes towards the longitudinal directions. As the diameter-to-distance ratio reaches 0.1 or below, the wave begins to travel as a quasi 1D wave.

FEA Robustness Verification in the Modeling of 1-D Stress Wave Propagation for a Split Hopkinson Bar (SHB) Test

2012 ◽  
Author(s):  
Michael L. McCoy ◽  
Rasoul Moradi ◽  
Hamid M. Lankarani
Keyword(s):  
Finite Element ◽  
Wave Propagation ◽  
Stress Wave ◽  
Hopkinson Bar ◽  
Stress Wave Propagation ◽  
Fe Model ◽  
Strain Gages ◽  
Split Hopkinson Bar ◽  
Split Hopkinson ◽  
Impact Problems

Impact loading on mechanical structures and components produces stress conditions that are large in magnitude and fluctuate with time which are difficult for the engineer to assess for design. The Stress Wave Propagation (SWP) is a classical methodology to account for these large stress levels. Due to the highly mathematical approach of stress wave theory along with consideration of boundary conditions interactions in the struck solid, the stress wave propagation method generates closed solutions to impact problems that are only 1-D in nature [1, 2]. In engineering practice, most mechanical problems are more complex than 1-D and thus numerical methods need to be applied to provide engineering solutions. The Finite Element Method (FEM) is a numerical technique that is commonly used in static and dynamic loading conditions to provide engineering solution to complex geometry and loading. In this paper, the FEM is examined to determine if this methodology is robust enough to accurately represent Stress Wave Propagation in solid mediums by the capturing wave propagation velocities, boundary reflections and transmissions along with large transient stress magnitudes using simple 2-D axisymmetrical elements. The most complex 1-D problem and perhaps the most practical solved problem by the Stress Wave Propagation is the Split Hopkinson Bar (SHB) test. The purpose of this test is to determine the dynamic strength of materials. A finite element (FE) model of an as-built SHB test apparatus was developed. In the same function as the strain gages, two nodes were used to extract the strain time histories from the FE model of the apparatus bars. It was found that the pseudo-strain gages of the FEA compared well to the SWP theory. The pulse magnitudes of strains, strain rates and stress were found extremely similar and exhibited magnitudes within 4% between SWP and direct examination. This model replicating a dynamic impact event demonstrated that the FEA can be used to solve complex impact problems involving stress wave propagation with the use of simple 2-D axisymmetric elements reducing computation time.

The Buckling Mechanism of Square Tube Subjected to the Impact of a Mass

2014 ◽  
Vol 624 ◽  
pp. 267-271
Author(s):  
Zhu Hua Tan ◽  
Bo Zhang ◽  
Peng Cheng Zhai
Keyword(s):  
Numerical Simulation ◽  
Wave Propagation ◽  
Numerical Methods ◽  
Stress Wave ◽  
Significant Influence ◽  
Strain Localization ◽  
Stress Wave Propagation ◽  
Low Velocity ◽  
Buckling Modes ◽  
The Impact

The dynamic response of the square tube subjected to the impact of a mass was investigated by using experimental and numerical methods. The square tube was impacted by a mass at the velocity ranging from 5.09 m/s to 12.78 m/s, and different progressive buckling modes were obtained. The numerical simulation was also carried out to analyze the buckling mechanism of the square tube. The results show that there is obvious stress wave propagation and strain localization in the tube, which has a significant influence on the buckling mechanism of the tube. The stress wave and inertia of the mass play different roles at various impact velocities. And buckling mechanism at low velocity is mainly caused by stress wave, whereas the buckling mechanism at high velocity is resulted from the inertial of the mass.

Finite Element Stress Response Analysis of Stepped-Lap Adhesive Joints Subjected to Impact Tensile Load

2000 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Takahiro Ohmori
Keyword(s):  
Finite Element ◽  
Wave Propagation ◽  
Principal Stress ◽  
Impact Load ◽  
Maximum Principal Stress ◽  
Adhesive Joints ◽  
Stress Wave Propagation ◽  
Maximum Value ◽  
Adhesive Thickness ◽  
The Impact

Abstract The stress wave propagation and the stress distribution in stepped-lap adhesive joints of similar adherends subjected to impact tensile loads and elastic deformation are analyzed using three-dimensional finite-element method (FEM). The impact load is applied to the joint by dropping a weight. One end of the upper adherend is fixed, and the other end of the lower adherend is subjected to an impact load. FEM code employed is DYNA3D. The effects of Young’s modulus of the adherends, the number of lapped steps, and the adhesive thickness on the stress wave propagation at the lapped, and fee butted interfaces are examined. It is also found that the maximum value of the maximum principal stress σ1 occurs at the end of the butted interface between the adhesive and the lower adherend to which the impact load is applied. As the number of the lapped steps increases, the maximum value of the maximum principal stress σ1 increases. It is found that the maximum value of the maximum principal stress σ1 increases as the adhesive thickness decreases. The maximum value of σ1 increases as Young’s modulus of the adherends increases. In addition, the experiments were carried out to measure the strain response of stepped-lap adhesive joints subjected to impact tensile loads using strain gauges. A fairly good agreement is seen between the analytical, and the experimental results.

Meshless Method Used in Wave Propagation in Anisotropic Material

2004 ◽  
Vol 261-263 ◽  
pp. 525-530
Author(s):  
Dong Yun Ge ◽  
Ming Wan Lu ◽  
Qiu Hai Lu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Composite Material ◽  
Wave Propagation ◽  
Radial Basis Functions ◽  
Stress Wave ◽  
Anisotropic Material ◽  
Meshless Method ◽  
Basis Functions ◽  
Stress Wave Propagation

The compactly supported radial basis functions (RBFs) is modified and used to the wave propagation in the anisotropic materials. An example to simulate the wave propagation in composite material is used in the paper to verify this method. In this example, stress wave propagation histories are obtained. The comparison between results by this method and by finite element method is also made. And the agreement with two results shows that this method can be used to simulate the wave propagation history in anisotropic material efficiently.

Modeling of Impact Behavior of Lightweight Composites under Metallic Projectile

2011 ◽  
Vol 88-89 ◽  
pp. 214-218 ◽  
Author(s):  
Ali Asadi ◽  
Seyedali Ali Sadough
Keyword(s):  
Wave Propagation ◽  
Numerical Simulations ◽  
Stress Wave ◽  
Alumina Ceramic ◽  
Impact Behavior ◽  
Stress Wave Propagation ◽  
Classic Theory ◽  
Lightweight Composites ◽  
The Impact ◽  
Good Agreement

The purpose of this article is studying the behavior of lightweight composites under metallic projectile by stress wave and comparing the results with numerical simulations. The target includes external layer, Alumina ceramic layer and supportive layer. The impact velocity of the projectile is 500 m/s. In this article, two lightweight composite targets with polymeric supportive layer and metallic supportive layer are studied. The results of numerical simulations and classic theory of stress wave propagation are in good agreement. The effect of changing supportive layer material and time of stress wave propagation into layers by the results of modeling is also studied.

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