1991 年 40 巻 453 号 p. 706-711
For the prediction of service load from fatigue fracture surface, not only the measurement of striation spacing(s) but also the information on stress ratio are necessary.
In the previous paper, the authors found that there was one to one correspondence between the ratio of striation height H to s (H/s) and the stress ratio R for 2017-T4 aluminum alloy. Since s ranges approximately from 0.1 to 2μm and H is smaller than s, the prediction of accurate R value requires the accurate measurement of H and s. For this purpose the procedure composed of cutting, polishing by emery paper and buff polishing was utilized previously. In this paper, an improved method using Microtome to reveal sharp striation sections is proposed and the improvement of measurement accuracy is shown.
In addition to 2017-T4 aluminum alloy, type 304 stainless steel was investigated in order to study the effect of mechanical properties on the relationship between H/s and R. The experimenal results gave almost the same relationship for type 304 stainless steel and 2017-T4 aluminum alloy. This result implies that the H/s-R relationship is independent of material properties, suggesting that one master curve of H/s-R and striation spacing s give a crucial information about the service load at the occurrence of fatigue fracture accidents.