パーライト型球状黒鉛鋳鉄の低サイクル疲労

抄録

Cyclic stress- and strain-amplitude-controlled low-cycle fatigue tests were conducted on a pearlitic ductile iron (PDI). The effects of spheroidal graphite (SG) and matrix on the fatigue process were examined. The material tested showed cyclic hardening behaviour at an early stage of the fatigue life, irrespective of the cyclic loading condition. The fatigue lives in all tests satisfied the Manson-Coffin type of relation, which resembled the results reported in the previous report. In evaluating crack growth, no unique linear relationship between crack growth rate and cyclic J-integral value was obtained, which suggested the presence of crack closure effect induced by SG. Microscopic cracks were mostly initiated at SG. However, casting shrinkage in some cases played an important role as a crack initiation site.