An Approach for Prediction of Fatigue Life Based on Fatigue and Low-Energy Shocks

The product which characterizes fatigue induced failure always suffers complex fatigue loads, and the damage caused by fatigue loads accumulate with time. Besides, the existence of shocks can not only increase the risk of failure directly, but also affect the magnitude of damage caused by fatigue loads. This paper analyzes the reliability of products when fatigue loads and shocks are involved at the same time. The features of fatigue damage and shock damage are investigated, and the coupling relationship between them is discussed. With assumptions of HCF and low-energy shocks, the effect of shocks on the fatigue damage is characterized as the degradation of the ultimate strength of the product. The overall reliability model with fatigue failure and shock failure is developed. Two conditions are considered for the reliability model: shocks with fixed time period and shocks with HPP. Three important cumulative damage theories are adopted. An engineering case of actuator cylinder is given to demonstrate this proposed approach.