The effect of sliding friction on the size of yielding region in the ultra high molecular weight polyethylene asperity in contact with metal was investigated. The main objective of this work was to gain an understanding of wear particle generation mechanism from the two-dimensional finite element model. To assess the influence of the parameters of interest, different friction coefficients and loading conditions were used in the numerical simulations. Results from the finite element analysis show that the increase of the yielding region is strongly influenced by the friction coefficient and the rise in the tangential force, which is related to the generation of wear particles. Finite element wear particle generation model, based on strain discontinuities, was therefore proposed. The results obtained in this study can lead to the development of an accurate finite element particle generation model that would be of use in the assessment of an artificial implant performance and their development.KEY WORDS: asperity contact, finite element, hip joint, strain discontinuities, wear particle formation Nomenclatures n normal vector S t discontinuity path u(r) displacement as a function of root, r w (x,t) propagation direction w (e) (t) vector of propagation direction at time, t and element, e Y yield point Ñ spatial gratient r ¼ @ @r ¼ @ @x þ @ @y (in 2D cases) (r) strain as a function of root r W 2D entire body r f flow stress r Y yield stress h asperity base angle

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A finite-element model for sliding contact in total hip joint prosthesis is presented in this paper. The hip prosthesis studied consists of an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup articulating against cobalt-chrome and alumina-ceramic femoral heads. Various aspects of prosthesis operation were analysed using the finite-element model. For example, bulk material and surface stresses were analysed under varying conditions of elastic modulus, friction coefficient, sliding speed, and radial clearance. The resulting variations of temperature were also recorded. The results obtained from the model are useful in understanding the operating conditions and the causes of wear in the hip prosthesis.

The purpose of the work is to obtain size and geometry numerical data of femur bone for designing femoral stem of total hip joint arthroplasy to fit for Indonesian patient with normal hip joint structure. Geometry data of femur bone was taken by both  X-ray and CT scan methods. The X-Ray anatomy digital objects were taken from different angles at certain intervals as input data to reconstruct anatomical objects. Slicing of femur bone imaging taken by CT scan has a constant interval. Data obtained from both CT scan and X-ray were compared. A solid model of bone is used as a visual-tactile representation, planning surgery (surgical) and simulation tool for physicians. In this work the data input was used for design of a total hip joint arthroplasty (THA) femoral stem. The work reported in this article is considered as a preliminary stage of the development of total hip joint arthroplasty devices for being fit to local (Indonesian) patients with hip joint disorders. The preliminary designs developed in this work is suit for many kind materials, however, for the implementation into manufacturing works, the use of Titanium Alloys need to consider for appropriate femoral stem designs by taking into account the available of tools and effectiveness of femoral stem production, made of the materials.

This research focuses on the properties and capabilities of carbon nanotubes (CNTs) as reinforcing agents in ceramic composite bearing components. The addition of CNT to pure ceramics can form composites with much better performance than conventional ceramics for various applications. The study was started from the pure ceramics in their use as a component of bearing total hip arthroplasty and the damage that occurred after implantation. The study covers factors that cause degradation of conventional ceramics introduction of properties and use of CNTs as new reinforcing agents for ceramic composite materials widely used sintering method and the heat and pressure parameters used during the sintering process to meet the standards for the manufacture of Total Hip Arthroplasty (THA) bearing component. The contact and buckling behaviors of the CNTs influence the composites friction properties. The presence of CNT until 20 wt% of CNT exhibited improve wear resistance with lower friction with the increase of weight percent. CNT reinforced ceramic coating might be capable to withstand high load-bearing conditions. Plastic deformation can be one of the critical processes in wear in the ceramics wear mechanism. Other processes are cracking and chemical reaction. The microstructures and porosity take an important role in indicating the ceramics wear properties and wear mechanisms.