抄録
In order to evaluate the stress of a machine part subjected to variable stress amplitude, the density of fatigue slip bands produced on aluminum foil is proposed as a measure for this purpose. The fundamental characteristics of slip band formation were examined under both constant and variable amplitude stresses. It was found that the density of slip bands was dependent on both the stress amplitude and the number of stress cycles. The variation of stress amplitude hardly affected the increase of the slip bands in successive stress cycles, irrespectively of the variable mode of stress. The density of slip bands under variable loading, fs was well correlated with the equivalent stress, σeq=(ΣσαiNi/ΣNi)1/α, where σi, Ni and α are stress amplitude, the number of stress cycles at σi, and a material constant determined from an aluminum foil used, respectively. It is concluded that the equivalent stress can be evaluated by the density of slip bands produced on aluminum foil, using the relationship between fs and applied stress amplitude obtained under constant loading. The accuracy of measuring the equivalent stress was within 3%.
