The wear of ultra-high molecular weight polyethylene (UHMWPE) cup is a major problem of artificial hip joints that are used in replacement arthroplasty. A recent study shows that the temperature of the femoral head in artificial hip joints increases to more than 41 °C during walking. The wear of the artificial hip joints increases if it is exposed to a temperature of 42 °C or higher for a long time. The purpose of this study was to investigate the influence of bulk temperature on the friction

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... d wear characteristics of artificial hip joints. A pin-on-disc testing machine that shows multi-directional sliding motion was used in this experiment. The pins were made of UHMWPE (GUR1050), and the material of the discs was stainless steel grade 316 (SUS316). The sliding speed was 20 mm/s, the mean contact pressures were 3.5 MPa and 20 MPa, and the test time was 14 hours. The bulk temperature was adjusted to 36 °C and 42 °C with a temperature controller. The lubricating liquid used was calf serum diluted by 25 percent, and it was regularly exchanged during friction experiments. The amount of its exchange was 1-4 ml/h, which was controlled by the inflow and outflow of the lubricating liquid in a liquid bath. This experiment has shown that the transfer film in the rubbed area of SUS316 discs decreased with the increase in the bulk temperature. Furthermore, the coefficient of friction and the wear of UHMWPE showed an obvious increase with the temperature rise. Therefore, it was considered that the temperature rise of the femoral head in artificial hip joints is related to the wear mechanisms of UHMWPE in vivo.