高速度工具鋼の引張・圧縮疲労破面のX線フラクトグラフィに関する検討(<小特集>X線材料強度小特集)

概要

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To investigate the influence of mean stress on the tensile and compressive fatigue strength of the heat-treated high-speed steel, fatigue tests were conducted on the test pieces of 9 mm and 6 mm in diameter which had been heat-treated at two levels of temperature, and the correlation between the X-ray parameters obtained from the X-ray measurements and the fracture mechanics parameters was stress distribution and the integral breadth distribution on the fracture surface. The results obtained are summarized as follows. (1) In the region of Fish eye, or the fatigue fracture surface, the residual stress on the surface was found to change from compressive residual stress to tensile residual stress and reached to a maximum at a certain value of the maximum stress intensity factor K_<max>. The residual stress on the brittle fracture surface was about constant at K_<max>. (2) The integral breadth on the fatigue fracture surface increased with K_<max> while the integral breadth on the brittle fracture surface was about constant irrespective of K_<max>. (3) In the region of K_<max> below 20MPa√<m>, the residual stress was compression. The reason of this behavior was discussed in terms of the correlation between the residual stress σr_1 controlled by K_<max> and the residual stress -σr_2 controlled by ΔK. It was found that the effect of -σr_2 was greater than σr_1 in this region.
1988-06-15