FATIGUE OF METALS CAUSED BY A RELATIVELY FEW CYCLES OF HIGH LOAD OR STRAIN AMPLITUDE

Abstract

The problem of fatigue is generally concerned with lifetimes in excess of 10⁵ cycles, where the applied, stress or strain is probably slightly above the initial yield of the material. In practice a component is more likely to be subjected to 10⁶–10⁸ cycles during its working life, and in such cases the applied stress is probably less than the ”static” elastic limit. It is therefore desirable, in view of the number of tests required on account of scatter, to accelerate the process of fatigue testing by using fairly high cyclic frequencies of several thousand per minute. It is now generally accepted that there is no speed effect over the range 500–10,000 c./m.