A Study on Fatigue Behavior according to Effective Case Depth in Induction Case Hardened SM45C Steel

J. Ocean Eng. Technol. 1991;5(1):71-80.

고주파표면경화한 SM45C 강에서 유교경화층깊이가 피로거동에 미치는 영향

오세욱,호정원,박원조

동아대학교,동아대학교,동아대학교

Keywords: highpfrequency induation harening, effective case depth, residual stress, surface origin type fracture, inner origin type fracture, plastic restraint

핵심용어: 고주파 담금질 강화, 유교경화층 깊이, 잔류응력, 표면기점파괴, 내부기점파괴, 소성구속

Abstract

This paper reveals the effect of the effective case depth(ECD) on the fatigue behavior of a high-frequency induction hardened SM45C in rotated bending fatigue test. In addition, the effects of fracture modes(surface origin type, inner origin type) on it are discussed. The fatigue limit of the induction hardened steel is remarkably increased compared with that of base metal. In addition, the fatigue limit is linearly increased as the effective casedepth grows deep in the region of this experiment (ECD/R;0.23-0.49). The S-N curve and fracture mode in the induction case hardened steel are classified into two kinds, as a result : N$_{f}$<10$^{5}$ ;surface origin type fracture(at high stress), N$_{f}$>10$^{5}$ ; in ner origin type fracture(at low stress). In case of inner origin type fracture; as the effective case depth(ECD) gets deep, the fatigue limit is increased by the reason that the fracture origin moves toward center; in reverse, is decreased by reason that the compressive residual stress gets low. As a result, the increasing effect of the former is much bigger than the decreasing effect of the latter, and the fatigue limit is increased as the ECD gets deep.eep.