Fatigue behavior and grain size of commercially pure aluminum plates

Abstract

The fatigue behavior of commercially pure aluminum plates of various grain sizes was studied by using a repeating type bending machine and the following conclusions were drawn.Fatigue limit in alternate bending stress was increased with the decrease of grain size and its dependence upon the grain size was nearly identical with that of tensile strength upon the grain size.Hardening, resulting from the alternate stress, exhibited a linear relationship to the logarithmic value of repeating times. In the early stage of testing (less than 7% of fatigue limit), the degree of hardening was low, but it was led to relatively higher values with subsequent cycles of bending. The conversion point of hardening by the repeated cycles did not depend upon grain size of the specimen.By intermediate annealing of the specimen after subjected to the repeated cycles of less than 7% of the the expected life, the number of total cycles to the perfect failure was increased. However, damage of the specimen was irrecoverable after it was subjected to the cycles of 10% of the expected life.