The influence of the observed increasing cyclic modulus in super-purity aluminum on stress distribution in bending-fatigue specimens is discussed. The resulting stress redistribution is examined for the various types of fatigue tests in common use. Differences in published fatigue data are partially explained in the light of this stress redistribution. It is concluded that for a cyclic strain hardening material, such as high purity aluminum, constant strain (or deflection) tests are more severe than constant moment tests, and the latter in turn are more severe than constant stress tests. Some observations of the development of slip bands and fatigue cracks are presented.
展开▼
