Investigation of the wear behaviour of polyacetal bushings by the inflow of contaminants

Polyacetal is used as a part of the lower arm ball joint in the automobile chassis system. It is used as the bushing material, which is in contact with the steel ball on stud under the grease-lubricated condition. In an automobile chassis system, environmental factors reduce the durability of the automotive components. While driving, the grease is contaminated with dust particles and water. Introduction of the dust particles and water into the ball joint increases the wear of the bushing. The damage or the failure of the ball joint can generate noise and lead to uncomfortable driving conditions. Also, it will reduce the durability of other components in the chassis system. Since the ball joint is directly exposed to external environments, it is necessary to investigate the effect of contaminants on the wear of the bushing. In this study, the wear behaviour of the polyacetal bushing for inflow of dust particles and water were investigated. The ball-on-disk type wear test was used for the sliding tests. The disk specimen was made with polyacetal material and the ball specimen was made with steel. The wear volume increased with the amount of the dust particles up to 1.5 g/10 ml and then decreased. The surface was covered with the dust particles, so the dust layer had to be removed to further wear out the surface. The wear volume increased with the amount of the water. When grease was contaminated with water, a water layer, instead of the grease layer, formed on the surface during sliding.