Surface Treatment for Fretting Fatigue Strength Improvement of Aluminum Alloy Used in Rear-Arm of Motorcycle

Abstract

Plain fatigue and fretting fatigue strength tests of aluminum alloy (JIS A7N01) specimens with surface treatments (fine particle peening, burnishing and solid lubricant film) were carried out using an electromagnetic fatigue testing machine. Fretting fatigue limit of untreated specimen was significantly low, which was about one fourth of the plain fatigue strength. Fretting fatigue strength of the specimen surface-treated with fine particle peening was slightly higher than that of the untreated specimen. The fretting fatigue strengths for solid lubricant film and burnishing have been remarkably increased compared to that of the untreated specimen. However, the fatigue limit for solid lubricant film was almost same as that of untreated specimen. From the in-situ SEM observation of fretting fatigue process, it was found that burnishing with smooth surface and high compressive residual stress effectively delayed the fretting fatigue crack nucleation and crack propagation. It was also found that solid lubricant film with low frictional coefficient effectively delayed them.