Papers by Keyword: Contact Mechanics

Abstract: Wear generated by the presence of friction on hip joint contact surfaces can cause debris, which may lead to loosening and failure of the hip prostheses. The objective of this study is to examine the limiting friction coefficient of the hip joint using Finite Element (FE) method. The hip joint model was developed to represent the contact surfaces between femoral head and inner socket, and the contact surfaces between inner socket and acetabular cup. The measured angle from 0° to 15° was applied to the inner socket for normal walking condition. The maximum contact pressure on the acetabular cup surface was found at the position angle of 10°. Therefore, further examination was carried out and the results showed that the highest friction coefficient of 0.4 was determined.

Abstract: A comparative study concerning the dynamics of chain drives mechanisms is presented in this article. The study compares the dynamic response using the spherical contact model proposed by Lankarani and Nikravesh with a new enhanced cylindrical model developed by the authors to describe the contact phenomenon in cylindrical clearance revolute joints. In the process, the influence of contact parameters and the numerical efficiency of using different contact modeling approaches are evaluated. It is demonstrated that cylindrical contact is stiffer than spherical contact. The spherical model represents a rough approximation to evaluate the contact between cylindrical bodies since contact forces are underestimated.

Abstract: This study presents a first attempt to develop a numerical three-dimensional multilayered (more than 2 composite layered coatings) elasticperfectly plastic rough solids model to investigate the contact behavior under combined normal loading and tangential traction. Contact analyses are performed to study the effects composite thin film layers. Local contact pressure profiles, von Mises stresses, and shear stresses as a function of material properties and applied normal and tangential friction loads are calculated.

Abstract: Radial lip seals made from PTFE composites are used more frequently for sealing of crank shafts in automotive and aerospace industries. Due to the seal loses materials and finally fails. Through experiment on a test rig, the tribology performance of seal can be predicted. Because of the non-linear elasto-viscoplastc material properties of PTFE composites, the finite element analysis (FEA) is adopted. A modified iterative remeshing method is adopted in wear process. The lip wears out according to the contact pressure of the node on the contact surface. Comparisons between numerical simulation and short-term service are made. The results show that the maximum of contact pressure decreased and width increased with wear time added, and the maximum of contact pressure moves toward the lip tip. Finally, it reaches lip tip, the phenomenon of uneven contact pressure was disappeared.

Abstract: Slewing bearings are the basic structural components widely used in construction machinery industry. Their stress status and distribution have great influence on the service life. A finite element approach for a single-row slewing bearing is established based on the bilinear isotropic model. The stress status at different loading conditions is simulated with the bearing geometric and material parameters. The result shows that the numerical simulation is reasonable in comparison with the analytical result obtained by Hertz’s theory and provides reliable design guideline for slewing bearings.

Abstract: Wear is the matrix surface and plastic deformation as the basic factors of the phenomenon, this paper analyzed with abaqus finite element method friction deformation which stress. The results show that the stress state changes drastically with different friction coefficient and the distribution of plastic deformation regions also changes. The regions seriously damaged by friction lead to fatigue via plastic deformation, which is the main reason for material friction and then dislocation friction occurs.

Abstract: The sliding frictional contact problem for a laterally graded half-plane has been considered. Two finite element (FE) models, in macro and micro scales have been developed to investigate the effective parameters in contact mechanics of laterally graded materials loaded by flat and triangular rigid stamps. In macro scale model, the laterally graded half-plane is discretized by piecewise homogeneous layers for which the material properties are specified at the centroids by Mori-Tanaka method. In micro scale model, functionally graded material (FGM) structure has been modeled as ideal solid quadrant particles which are spatially distributed in a homogeneous matrix. Boundary conditions and loading is the same in both models. The microstructure has modeled as rearrangement and sizes changing of particles are possible to provide the possibility of crack nucleation investigation in non-singular regions. Analyses and comparison of the results showed that micro and macro scale results are in very good agreement. Also, increasing the grains aspect ratio and using optimum distribution of grains decrease stress distribution roughness on the surface. Therefore, the possibility of surface cracking far from stamp’s edges decreased.

Abstract: Top drive casing running tool, because of its convenience, speed and safety, has been widely received by the research enterprises of petroleum mechanism and instrument. Now, there have been developed several kinds of casing running tools which have gradually been used by the drilling corporation at home and abroad. The slips system’s parameters, such as the axial thrust, slips length, teeth form, teeth interval, etc., directly affect the performance and safety of casing running tools. Those have no reports about correlative theoretical investigation results. Here, we found the mechanical analysis model between slip and casing and gain the minimum primitive axis thrust of slips. Then the minimum teeth interval of the slips is deduced by contact mechanics. And then the slips available working length is worked out through the shell theory and empirical formulas. Finally, based on finite element method, we obtain tooth form angles’ recommendable range by studying the tooth form. This study supplies theoretical basis to structural design of slips system of the top drive casing running tool.

Abstract: Composites forming processes involve mechanical interactions on the ply, tow, and filament level. The deformations that occur during forming processes are governed by friction between tows and tooling material on the mesoscopic level and consequently between filaments within the tows on the microscopic level. A thorough understanding of the frictional properties of individual filaments is essential to understand and to predict the macroscopic deformations of a fabric during forming. This paper provides a global description of the experimental and modelling approaches to explain the contact friction between fibrous tows and metal tooling material, focusing on contact mechanics at the tow and filament scale.

Abstract: With the development of functional and structural materials, increasing interests have been shown in the field of biomaterials with a negative Poisson’s ratio (auxetic), which exhibit the unusual property of becoming thinner when compressed. This unusual property makes it potentially a synthetic replacement biomaterial with adequate mechanical property and wear resistance. In this study, the potential of applying the auxetic ultra-high molecular weight polyethylene (UHMWPE) for the artificial hip joint was discussed. The contact mechanics characteristics in artificial hip joint replacement under different Poisson's ratios of -1<μ≤0.5 were investigated and compared using the finite element method. The results show that Poisson’s ratio had great effect on the contact mechanics in artificial hip joint replacement. Therefore, the future work should focus on tailoring an auxetic UHMWPE with a suitable Poisson’s ratio for artificial hip joint replacements.