EXPERIMENTAL VERIFICATION OF RANDOM LOAD FATIGUE ENDURANCE

— This paper is concerned with various problems related to laboratory experimental verification of fatigue endurance under random loading. Based on statistical characteristics of stationary and non-stationary operating random processes (probability density function and/or power spectral density, transition probability densities) it is shown how to design real time simulation algorithms that are further used to create inputs of computer controlled electrohydraulic loading systems. The corresponding fatigue tests (strain or stress constrolled) produce endurance curves that can be plotted in various coordinates (peak or RMS values vs fictitious number of cycles or time to failure) offering non-identical conclusions and qualitative interpretations. Some examples of the influence of simulated random process probability density function and/or power spectral density on the resulting fatigue endurance are presented and also certain suggestions concerning prospects for random load fatigue tests are summarized.