Abstract: According to the load characteristics of vehicle structural parts during operation, the drive shaft strength evolution under low-amplitude training loads is studied. Through coaxing effect experiment of smooth specimens, the coaxing stress range of shaft material 40Cr stress is determined. The influences of load amplitude and load times on the residual fatigue strength of structural parts are analyzed. The results show that the best coaxing effect of structural strength exists under certain conditions. By orthogonal analysis and processing of test data, the relation model of strengthening or damage effect and equivalent symmetrical stress and load times is fitted. Furthermore, based on this model and the work load spectrum of auto drive shaft, a fatigue cumulative strengthen model in work process is built through the integration of strengthening and damage effect. In accordance with matching the design stress range with the best coaxing effect, a new method of lightweight design is proposed with the aim of cumulative strengthening effect of low amplitude loading, so as to provide a theoretical basis for auto structural parts lightweight design.

Key words: Coaxing, Cumulative fatigue strengthen, Drive shaft, Lightweight design