scholarly journals Investigation of the Stress-Wave Propagation In Improve the Reliability of the Impact-Echo Method

2002 ◽  
Vol 14 (2) ◽  
pp. 266-274 ◽  
Keyword(s):  
Wave Propagation ◽  
Stress Wave ◽  
Stress Wave Propagation ◽  
Impact Echo ◽  
The Impact ◽  
Impact Echo Method

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.

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.

Structural Damage Survey Using Nondestructive Tests Based on Stress Waves

2007 ◽  
Vol 348-349 ◽  
pp. 389-392
Author(s):  
Young Sang Cho ◽  
Seong Uk Hong
Keyword(s):  
Damage Detection ◽  
Structural Damage ◽  
Flaw Detection ◽  
Concrete Structures ◽  
Stress Waves ◽  
Stress Wave Propagation ◽  
Impact Echo ◽  
Nondestructive Tests ◽  
The Impact ◽  
Impact Echo Method

The impact echo method has been widely used to evaluate the integrity of concrete structures. This paper is to study damage detection technique of concrete members using impact echo method, one of the nondestructive tests based on stress waves. Stress wave propagation behavior is to be studied based on wave mechanics in concrete media. Based on the theoretical study, nondestructive tests using stress waves will be conducted to observe the wave behavior on structural damages. For the damage detection of concrete structures, a mock-up specimen was prepared, and various tests were conducted for the study of the behavior of stress waves. The concrete slab of the flaw detection consist of 5 types; the first group for the thickness presumption, the second group for the position of the voids, the third group for the position of the re-bars, the fourth group for the position conduit, and the fifth group for the position of the crack. Test results are evaluated and summarized to verify if the nondestructive tests can survey damages in the concrete structures in this paper.

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.

Improvement of the Impact-Echo Method for the Higher Reliability in the Structural Integrity Assessment

2006 ◽  
Vol 321-323 ◽  
pp. 336-339 ◽  
Author(s):  
Mi Ra Cho ◽  
Ki Bong Kim ◽  
Sung Ho Joh ◽  
Tae Ho Kang
Keyword(s):  
Structural Integrity ◽  
Stress Wave Propagation ◽  
Layered Systems ◽  
Impact Echo ◽  
Practical Applications ◽  
Integrity Assessment ◽  
Excellent Method ◽  
The Impact ◽  
Impact Echo Method

The impact-echo method, which is to evaluate the integrity of concrete and masonry structures nondestructively, is an excellent method in practical applications, and provides a high quality of structural integrity assessment. However, in the case of multi-layered systems in which each layer has different stiffness, the impact-echo method may lack reliability in thickness evaluation, which demands improvement of the impact-echo method. This study was first dedicated to the understanding of stress-wave propagation in the impact-echo test, and secondly, the reliability of the impact-echo method was investigated through the numerical simulation of the impact-echo test. The investigation included the research on influencing factors such as stiffness contrast between layers and receiver location. Finally, the research in this paper led to the development of the phase-difference response (PDR) method, based on the frequency response between two receivers deployed in a line with an impact source.

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