1988 年 37 巻 417 号 p. 612-618
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 9mm and 6mm 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 examined. An X-ray microbeam stress measurement equipment was used to measure the residual strees distribution and the integral breadth distribution on the fracture surface.
The results obtained are summerized 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 Kmax. The residual stress on the brittle fracture surface was about constant at Kmax.
(2) The integral breadth on the fatigue fracture surface increased with Kmax, while the integral breadth on the brittle fracture surface was about constant irrespective of Kmax.
(3) In the region of Kmax below 20MPa√m, the residual stress was compression. The reason of this behavior was discussed in terms of the correlation between the residual stress σr1 controlled by Kmax and the residual stress -σr2 controlled by ΔK. It was found that the effect of -σr2 was greater than σr1 in this region.