More than ten thousands people died caused fatal accidents in houses every year in Japan. Among them a number of the aged people died in falling down to flat floor even though without any steps. Floor slipperiness is usually represented as static friction coefficient at the slips in toe-off during last half of gait cycle. However, it is said that slips are also occurred at heel down to floor during first half of gait cycle. In order to evaluate floor slipperiness at heel down, it is necessary to measure the dynamic friction coefficient between footwear and floor under incremental vertical load during the heel down.
The wear of UHMWPE(ultrahigh molecular weight polyethylene) used in artificial joint is investigated more than 5 million cycles using joint simulator. The simulator is reproduced vertical load, flexion/extension, abduction/adduction and internal/external rotaion during gate cycle.