Stress Distribution Area Research Articles

Role of Five-fold Twin Boundary on the Enhanced Mechanical Properties of fcc Fe Nanowires

The role of 5-fold twin boundary on the structural and mechanical properties of fcc Fe nanowire under tension is explored by classical molecular dynamics. Twin-stabilized fcc nanowire with various diameters (6-24 nm) are examined by tension tests at several temperatures ranging from 0.01 to 1100 K. Significant increase in the Young's modulus of the smaller nanowires is revealed to originate from the central area of quinquefoliolate-like stress-distribution over the 5-fold twin, rather than from the surface tension that is often considered as the main source of such size-effects found in nanostructures. Because of the excess compressive stress caused by crossing twin-boundaries, the atoms in the center behave stiffer than those in bulk and even expand laterally under axial tension, providing locally negative Poisson's ratio. The yield strength of nanowire is also enhanced by the twin boundary that suppresses dislocation nucleation within a fcc twin-domain; therefore, the plasticity of nanowire is initiated by strain-induced fcc→bcc phase transformation that destroys the twin structure. After the yield, the nucleated bcc phase immediately spreads to the entire area, and forms a multigrain structure to realize ductile deformation followed by necking. As temperature elevated close to the critical temperature between bcc and fcc phases, the increased stability of fcc phase competes with the phase transformation under tension, and hence dislocation nucleations in fcc phase are observed exclusively at the highest temperature in our study.

A Calculation Model on Dynamic Response of Opposite-Side Simple-Support-Free Rectangular Plate under Shock Loads

The numerical model for opposite-side simple-support-free rectangular plate is established based on the theory of engineering vibration. The basic differential equation of transverse vibration of thin plate and the method of development of trigonometric function series are being used to analyze the behaviors of rectangular plate under moving area-loads in constant speed. The analytical solution of dynamic response for plate was obtained. This model can be used to simulate the dynamic response for thin plate under moving shock load and to assess the yield state of thin plate under shock loads. The Mises' yield criteria was used to judge the dynamic yield case of plate under shock loads. The distribution of stress and strain of dynamic response in parent plate under shock loads was solved according to the free-simple harmonic oscillation equation of plate. The calculation results can be used to analyze the plastic area and visco -plastic area of stress distribution in the plate. It is of some guiding significance for the installation structure of parent plate in explosive welding.

Study of Influence of Substrate Topography on Stress Distribution in Structural Adhesive Joints

This paper analyses the influence of surface roughness on adhesive bond strength. Numerical simulations were performed to evaluate the influence of geometry on the performance of structural adhesive joints. The objective is to create a model to describe the behaviour of the interphase of adhesive joints according to its geometry. Two-dimensional simulations with theoretical geometries were performed considering parameters of roughness, stress distribution, and contact area to verify the qualitative influence of substrate topography on the adhesion of a joint. Numerical analyses were done to verify the effect of the interpenetration of materials on the mechanical properties of the interphase.

Biomechanics Characteristics of New Type Artificial Hip Joint

The structure, geometrical shape and material are the three main parts of the prostheses. This research focuses on the geometrical shape analysis. The geometrical shape of human natural femoral head is similar to the ellipse, but, the artificial femoral head is rotundity shape. There is difference between ellipse and rotundity femoral head. Two models are developed and analyzed in this paper under same conditions used Finite element analysis method. Based on the calculation results, it is shown that the ellipse shape femoral head have the similar characteristics to the natural joint than rotundity model. The ellipse has the more lowness stress distribution area and more small distortion magnitude than rotundity shape artificial femoral head. It should have the more kind effect replace rotundity femoral head with ellipse shape artificial formal head. Keywords: hip joint; prosthesis design; finite element analysis; biomechanics

Super-single tire loadings and their impacts on pavement design

Pavement design and analysis are generally performed based on the load equivalent factor (LEF) obtained from conventional dual tires and assume that the contact stress is equal to the tire inflation pressure. However, heavier tire loadings, such as super-single tires, produce much higher contact stresses than the inflation pressure. This results in larger deformations of subgrades, requiring advanced modeling of subgrades, such as elastic–plastic analysis. Super-single tires also have a different contact area shape from that of conventional tires. To assess the increased contact stresses by super-single tires, realistic contact stress distribution and contact area ratio for super-single tires should be used in the analysis. Three-dimensional finite element analyses of typical flexible pavements were done to evaluate the effects of the increased contact stresses of tire loadings on the subgrades, including load equivalency factors, overlay effect, and subgrade improvement as the behavior of subgrades becomes more important due to the increased contact stresses. Analysis results indicate that the increased contact stresses should be taken into account in the pavement structure design, as well as design of overlay or subgrade improvement. Based on the numerical results, simple design examples are suggested.

Age-related changes of the glenoid labrum in normal shoulders

A growing number of labral changes are described in the literature. The purpose of this study was to evaluate the glenoid and labrum of normal shoulders at different ages and characterize any apparent age-dependent changes. We analyzed 32 normal cadaveric shoulders with a mean age of 57 years (range, 18-89 years). There were 22 male and 10 female cadavers, with 14 right and 18 left specimens. The shoulders were studied macroscopically, histologically, and radiologically. The radiologic evaluation consisted of an analysis of the subchondral mineralization of the glenoid with the use of computed tomographic osteoabsorptiometry. Macroscopically, there were no statistically significant differences among the age groups. Histopathologically, the labrum showed a significant qualitative and quantitative increase (P <.01) in lesions across all regions with increasing age. In younger individuals, lesions at the 12-o'clock position were the most prevalent, with the incidence increasing with age. The anterosuperior position was the region with the next highest prevalence. This was also the area of the highest stress distribution on the glenoid. Our studies demonstrated clear histopathologic changes of the glenoid labrum that are significantly age-related at specific sites. The earliest changes are seen close to the area of highest stress distribution of the glenoid, which could explain the progressive labral changes with increasing age. Arthroscopically detected changes of the glenoid labrum should be evaluated in the context of age-related changes in normal shoulders. (J Shoulder Elbow Surg 2003;12:40-52)

Endurance sports after total knee replacement: a biomechanical investigation.

No biomechanical evaluation of total knee designs exists for loads occurring during sports activities. It was the purpose of the present study to evaluate the contact stress distribution and contact area of different knee joint designs for loads that occur during four common recreational endurance activities. Three different total knee designs were evaluated for loads occurring during cycling (1.2 body weight (BW) at 80 degrees of knee flexion), power walking (4 BW at 20 degrees), hiking (8 BW at 40 degrees), and jogging (9 BW at 50 degrees) using Fuji pressure-sensitive film. The designs consisted of a flat tibial inlay, a curved inlay, and an inlay with mobile bearings. Five measurements were conducted for each load. The pressure sensitive films were scanned and analyzed using an image analysis program. During cycling, the area with stress levels above the yield point of polyethylene (overloaded area) was below 15 mm2 for each design. During power walking, the mobile bearing design showed no overloaded area, whereas it was below 50 mm2 for the flat and curved design. During downhill walking and jogging, more than 140 mm2 were overloaded for each design. It was concluded that patients after total knee replacement should alternate activities such as power walking and cycling. For mountain hiking, patients are advised to avoid descents or at least use ski poles. Jogging or sports involving running should be discouraged after total knee replacement.

Experimental study of the plastic yielding of rolled sheet metals with the cruciform plate specimen

In the current paper, an experimental technique for the evaluation of the in-plane yield loci of sheet metals with the cruciform plate specimen is presented. The measurement system is shown to conform to the optimized design concept proposed by other researchers. Finite element analysis demonstrates a reasonably wide area of uniform stress distribution in the center of the cruciform specimen, which allows the measurement of in-plane strain field by using a stacked strain rosette. Based on the designed apparatus, the yield loci of the 1100-F aluminum sheets corresponding to the as-received condition, and 25% and 50% thickness reductions by further rolling, were constructed, respectively, by applying biaxial loadings along the two principal axes of the cruciform specimen. A set of uniaxial tension tests were also performed to determine the plastic properties of the aluminum sheet along different directions with respect to the rolling direction. Finally, Hill's 1990 yield criterion is examined based on the experimental data from both biaxial and uniaxial tension tests.

全部床義歯床下支持組織におけるこう合圧による応力分布に関する研究 第１報 下顎第一大臼歯部の二次元要素分割と荷重点の条件について

The purpose of this study was to analyze the occlusal stress under complete denture base.In this study, the effect of the separating elements and loading points were performed utilizing the finite element method. The results were as follows:1. As the separation of elements decreases, the stress distribution area become limited.2. The area of the greatest stress concentration was found in mucosa under the loading point.3. The area of stress concentration of cortical bone was found on the lingual side.4. The lower bite rim model has a tendency to be displaced to the lingual side.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - The application of dislocation etching techniques to the study of liquid impacts

Erosion damage is very often the cumulative result of a series of liquid droplet impacts which individually do not produce any deformation visible under the optical microscope. Such collisions do, however, produce dislocations in the crystalline structure surrounding the area of impact, and in suitable materials these dislocations can be revealed by chemical etch pitting. The technique is particularly easy to apply to freshly cleaved lithium fluoride crystals, and it has been used to study several types of impact. The impact of solid balls produces symmetrical rosettes of dislocations lying on {110} planes, and the dimensions of the rosettes can be related to the area of contact and stress distribution calculated from the theory of the collision of elastic/plastic bodies. Similar, but less symmetrical, rosettes are produced by liquid impacts and, by comparison of the extent and distribution of the dislocation loops in the two cases, it has been possible to make an estimate of the pressure and effective area of contact for liquid drops of various sizes, quantities which are otherwise difficult to measure. The behaviour of liquids other than water has also been investigated.