Experimental and analytical studies on the effect of excessive loading on fatigue crack propagation in piping materials

Yamaguchi, Yoshihito ; Katsuyama, Jinya  ; Onizawa, Kunio ; Li, Y.* ; Yagawa, Genki*

Since the seismic regulatory guide was revised and the Niigata-ken Chuetsu-oki earthquake occurred, attention is being drawn to the evaluation of the effects of large scale earthquakes for piping systems in which cracks may potentially occur. In this work, crack growth behaviors after excessive loading were experimentally and analytically evaluated for carbon steel and austenitic stainless steel. Increase and decrease pattern of load amplitude and maximum load of cyclic loading were applied to fatigue crack growth test. According to these results, retardation effect of crack growth was confirmed after excessive loading. In addition, applicability to the retardation effect of the modified Wheeler model was elucidated. We confirmed the retardation effect hardly influence the failure probability based on seismic loading by the probabilistic fracture mechanics (PFM) analyses with the Wheeler model.