الفهرس 
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Abstract
In the present investigation, the tribological behavior of ultra high molecular weight polyethylene (UHMWPE) was investigated. The tribological behavior of such polymeric material was investigated under dry, distilled water and physiological saline lubricated conditions against a 316L stainless steel disc. The effect of the applied load, sliding velocity and sliding distance (sliding time) on the coefficient of friction (COF) and the wear rate (WR) of UHMWPE were investigated. The worn surfaces of UHMWPE samples were investigated using scanning electron microscope (SEM). The results show that the friction behavior of UHMWPE is very sensitive to its water absorption rate. In dry sliding condition, the initial friction coefficient is relatively low, but it increased gradually with the sliding distance, and then steady-state friction coefficient is observed. In saline and distilled water lubrication, the initial friction coefficients are all higher than their steady-state friction coefficients and similar to that in dry sliding. On the other hand, the friction coefficient values decreased with the increasing of sliding speed and increased with the increasing of applied load values. The steady-state friction coefficient in dry sliding is about two times the value in saline, and about 3–4 times that in distilled water. The wear rate of UHMWPE under dry sliding is the highest while the wear rate under distilled water lubrication is the lowest. The wear mechanisms are different under dry friction and various lubricating conditions. It was also observed from the result that, the weight loss and the wear rate of UHMWPE samples were increased with the increasing of load and sliding speed and decreased with the decreasing of these factors.In the current investigation, an artificial neural network (ANN) model for predicting the effect of the applied load, the sliding speed and type of lubricant on wear rate and the coefficient of friction of the UHMWPE was developed. It has been observed that the experimental results coincided with ANNs results.