球状黒鉛鋳鉄の低サイクル疲労強度および機構に及ぼす基地組織の影響

概要

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In order to investigate the effect of matrix on the fatigue behavior of ductile cast iron, both cyclic stress- and strain-amplitude-controlled low-cycle fatigue tests are conducted on ductile cast irons with different microstructures. Three kinds of ductile cast irons, i. e., ferritic, (FDI), pearlitic, (PDI),and bainitic matrix, (ADI), with the same chemical compositions, are prepared by using different heat treatments. Each material shows cyclic hardening behavior at an early stage of fatigue life. The fatigue life satisfies the Manson-Coffin relationship and differs depending on matrix. In particular, the fatigue life trends observed in two test conditions are apparently opposite. However, a definite trend of the fatigue life is obtained when the relationship between the stress amplitude and strain amplitude is correlated by means of the cyclic stress-strain relationship. The microscopic fatigue process is dominated by initiation and propagation of the microcrack. It is recognized that the microcrack initiation originates not only in spheroidal graphite, but also in microshrinkage in PDI and ADI. The relationship between the crack growth rate of a leading crack and cyclic J integral value indicates no unique linear relationship, which suggests the effect of the crack closure behavior of spheroidal graphite.
一般社団法人日本機械学会の論文
1992-08-25