Low-Cycle Fatigue of Aluminium Alloy due to Rotating-Beam Bending under Random and Multiple Repeated Loading

Abstract

Recently, low-cycle fatigue of metallic materials has been widely studied, and several fracture criteria of fatigue have been presented as the basis for predicting low-cycle fatigue lives. The authors had previously proposed a fracture criterion of low-cycle fatigue based on strain, in stead of the Miner's linear damage rule based on S-N curve, and investigated the relation between the stress-strain behaviour and the fatigue lives by carrying out the low-cycle fatigue tests under rotary bending to measure the stress and strain during those tests, and the above mentioned criterion was verified experimentally.Although many ordinary fatigue tests have hitherto been carried out of aluminium alloys, still we have very few data of low-cycle fatigue tests of aluminium alloys performed under rotary bending. In the present report information is given of experimental studies that are usually performed on steels as applied to the studies on the aluminium alloy 17 S-T 4 under the condition of the constant- and varying-stress amplitudes. Moreover the effects of frequency distribution of loads and their sequence of application on fatigue lives were investigated. The applicability of the above criterion has been discussed by summarizing the data by means of“the reduced strain amplitude”and“the reduced stress amplitude modified by the stress correction factors”already reported.