Beitrag niedriger Lastamplituden zur Ermüdungsschädigung von 0,15 %C Stahl

The S-N curve of 0.15 %C steel shows an endurance limit. Two-step variable amplitude loading experiments serve to investigate the influence of numerous cycles below the endurance limit on fatigue damage. If high stress amplitudes of the loading sequences are more than approx. 15 % above the endurance limit, low load cycles contribute significantly to fatigue damage. Investigations of fatigue crack propagation under two-step variable amplitude loading show accelerated crack growth caused by low load cycles. If high stress amplitudes of the two-step sequences are less than 15 % above the endurance limit, beneficial influences of numerous low load cycles are found. Under these conditions, the material can sustain far greater numbers of load cycles than predicted by Miner damage accumulation calculation. Fatigue crack growth studies show that under these conditions for the high load numerous low load cycles lead to stop of the crack propagation.