Fatigue Crack Propagation Paths Across the Interface of Macroscopic Hardness Discontinuity in Material
Kiyotsugu OHJI, Yoshitaka MISAKA, Takeshi HORIKAWA, Tetsuya TSUJIKAMI, Satoru NAKAI, Takashi MORI and Yoshinori YAMANA
Abstract:The criterion determining the fatigue crack propagation path near or across the interface of hardness discontinuity in material inhomogeneous with respect to hardness was experimentally investigated. The Dsq maximum criterion was used as a reference. Single-edge-cracked panels of S45C hard steel subjected to uniform pulsating axial stresses of R=0.1 were used as test specimens, which had in each a partial slant band-like or circular area hardened by induction-heat-treatment; the fatigue cracks were intended to propagate perpendicular to the specimen axis, if the Dsq maximum criterion was valid. It was observed that the fatigue cracks propagated in all cases straight and perpendicularly to the specimen axis, crossing the interface of the hardness discontinuity, indicating that the Dsq maximum criterion was valid in this case. Key Words:Fatigue, Crack, Crack Path, Hardness Discontinuous Material, Dsq Maximum Criterion