Experimental Fatigue Results under Stationary and Nonstationary Random Vibration

Abstract

There is a steadily increasing supply of interesting fatigue test result for materials under the action of random processes, especially in the area of stationary random loading. In the strictest sense, nonstationary random processes in fatigue should be considered quasistationary processes since the fatigue loading is nominally stationary over the long run to failure. It is possible to imagine nonstationary loading s over a complete fatigue life (such as the action of wear or steadily increasing damping in a fatigue test), but actual tests of this nature are not yet available. This paper surveys the field of stationary and quasistationary random loading subsequent to the author's 1968 state of the art paper on this topic. One of the most significant findings from this survey is the widespread use of repeated random loading sequences by research groups and working professional committees in interlaboratory test programs. The necessity to analyze service loadings carefully, to separate random and nonrandom aspects, is also dealt with in detail.