Fatigue Life Evaluation under Service Loading by Frequency Domain Method

In design of a structure in consideration of the fatigue life, it is very important to evaluate not only a fatigue life under the constant loading but also a fatigue life under the service loading. Generally, a fatigue life prediction by the rainflow method is used when a service loading condition is given as a wave form (we call this as time domain information). However, recently we sometimes experienced that the service loading condition is given only as the frequency domain information such as power spectrum density (PSD) of dynamic load.In this paper, firstly we present the investigated results of the fatigue life estimation by using service loading with frequency domain information. Then fatigue tests are also carried out by using the round bar specimens under several service loading conditions. Finaly, these fatigue lives estimated by using frequency domain information are compared with the estimated results by using time domain information. We can confirmed that These both estimated results coincided well with the experimental results, and this fatigue life estimation method using frequency domain information is effective in the standardized fatigue life evaluation of structures.