OS2121 高輝度放射光ラミノグラフィを用いた高強度鋼中の転動疲労き裂の観察

Abstract

In rolling contact fatigue (RCF), cracks are usually initiated from inclusions under the surface and propagated to the contact surface. In the present study, RCF cracks was observed using synchrotron radiation computed laminography (SRCL) in SPring-8. For observation of crack propagation, ex situ rolling fatigue test and SRCL were applied to same sample. Laminography is suitable for the observation of sheeted material and sheeted sample is useful for operation of rolling fatigue tests. The specimen with flaking damage was measured by SRCL. It was found that two types of cracks, vertical crack and horizontal crack under the contact surface, which is typically rolling fatigue crack, can be measured by SRCL. For observation of RCF crack propagation, vertical crack which initiate from inclusion and propagated in the direction perpendicular to the contact surface, could be detected. SRCL and fatigue tests were conducted three times. As results, crack propagation could be observed between first and third measurements, while the different part of crack was detected in second measurement. Residual compression stress is considered to affect the observation of RCF crack. SRCL is concluded to be effective for evaluation of initiation and propagation behavior of crack in the rolling fatigue.