FATIGUE CRACK PROPAGATION AND CLOSURE EFFECT IN FERRITE-MARTENSITE DUAL-PHASE STEEL
DENG Rongying;YE Zhijun;LIU Shuhua;ZOU Dingqiang Institute of Mechanics; Academia Sinica; Beijing China Academy of Railway Sciences; Beijing
Cite this article:
DENG Rongying;YE Zhijun;LIU Shuhua;ZOU Dingqiang Institute of Mechanics; Academia Sinica; Beijing China Academy of Railway Sciences; Beijing. FATIGUE CRACK PROPAGATION AND CLOSURE EFFECT IN FERRITE-MARTENSITE DUAL-PHASE STEEL. Acta Metall Sin, 1990, 26(3): 50-54.
Abstract The effect of ferrite content in ferrite-martensite dual-phase steel onthe initiation and propagation of fatigue crack and the plastic deformation at cracktip has been studied. In a range of ferrite content from 24.2 to 41.5%, the opti-mum seems to be 33.8%, of which the crack initiation will be prolonged, the thre-shold value increased, the propagation rate decreased and the closure stress intensityfactor increased. As the propagation force is described by effective stress intensityfactor, three steels with various ferrite contents will show the same propagationbehaviour on da/dN vs △K_(off) curve. It is shown that the closure effect increaseswith the decrease in △K at the fatigue crack tip. When △K equals to △K_(th), theclosure effect reaches a maximum value of 0.7 in a dual-phase steel with 33.8%ferrite.
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