Low-cycle fatigue damage and fatigue reliability of 7075-T651 aluminum alloy under random loading

摘要

Low-cycle fatigue behavior of 7075-T651 aluminum alloy under random loading condition is investigated in the present study. Special attention is paid to the following subjects. First of all, the mechanical, in particular, the low-cycle fatigue behavior of the alloy is studied following a traditional procedure. Secondly, fatigue damage of the specimen is calculated based on cycle-by-cycle counting and random vibration theory respectively. Thirdly, the applicability of a "plastic work interaction damage rule" proposed by Morrow is investigated. Finally, the fatigue reliability is studied based on experimental results. Through the study it is found that the plastic work interaction rule does provide us with better fatigue damage prediction than the widely used Palmgren-Miner rule, and a formula derived in random vibration books can be used to predict the fatigue damage very easily. It is also found that fatigue lives of the tested specimens can be fitted appropriately by normal or lognormal probability density function. The result provides us with necessary information on the fatigue reliability assessment of components made of the tested material.