Study on Zigzag Path of Low Cycle Fatigue Surface Crack Propagation under Cantilever Bend Loading

Low cycle fatigue surface crack propagation rate(SCPR) test of 10CrNiMo steel with four pieces of specimens were carried out,adopting six-grade nominal strain increased gradually as control parameters under cantilever bend loading.It was found that under the control of every-grade nominal strain,SCPR tends to a certain stable value,but local crack propagates sometimes fast and sometimes slow and it is particularly obvious under the control of low nominal strain.Analysis indicated that surface crack propagation presented a zigzag path of transition and bifurcation,which brought on local cracks unstable growth.Usually,transition and bifurcation will decrease surface crack propagation rate,but sometimes also accelerate surface crack propagation.