DISLOCATION STRUCTURE OF FATIGUE CRACK TIP
疲劳裂纹尖端的位错结构

It was observed first in this test that the stabilized dislocation cell and wall structures had been formed on near fatigue threshold of physcial short crack in dual-phase steels. There was a probability of forming dislocation cell on ferrite-martensite interfaces in long crack growth threshold. where the dislocation lines were more dense, there were the dislocation lines of single(R = 0,-1) and cross slip(R=-1) in the second stage of long crack growth ;there were obviously rare and lengthened dislocation lines of single and cross slip in the third stage of long crack growth. It is indicated that the dislocation morphologies of fatigue crack tip were the products of strain history. The dislocation cell and wall structures were substable on near physical short crack threshold. it was constituted into dynamic balance with cyclic stress-strain on threshold, and also was one of microstructural parameters.