Abstract
To investigate the opening and closing behaviors of fatigue cracks on the surface of 1/2CT specimen of high-speed tool steel SKH51, the contact stress σc1 between the two opponent fracture surfaces was determined by X-ray stress measurements in the vicinity of fatigue crack tip at Kmax=8.9MPam1/2 and Kmax=15.4MPam1/2 during the loading process. The results obtained are summarized as follows.
The residual stress on the fatigue fracture surface was found to be given as the sum of three components; the tensile stress component σr1, resulting from the monotonic plastic zone dimension, the compression stress component -σr2, resulting from the cyclic plastic zone dimension, and the compression component -σr3, resulting from the contact compression zone dimension under the fracture surface. The effect of -σr3 was especially large in the low stress intensity factor range, and consequently the residual stress on the fracture surface became compressive.
