Improvement Of Bending Fatigue Limit By Shot Peening For Spring Steel Specimens Containing An Artificial Surface Defect

Author:  KTakahashi Ando Amano Miyamoto FTakahashi Tange On
Source:  Conf Proc: ICSP-10 Tokyo, Japan 2008
Doc ID:  2008085
Year of Publication:  2008
ABSTRACT Effects of shot peening on the bending fatigue limit of spring steel specimens (SUP9A) containing an artificial small hole were investigated. Shot peening (SP) and stress shot peening (SSP) were carried out with specimens containing an artificial drilled hole 0.2, 0.4 and 0.8 mm in diameter. Bending fatigue tests were carried out with the specimens. The fatigue limits of specimens containing an artificial small hole were increased by shot peening. Stress shot peening (SSP) was more effective in improving fatigue limit. The specimens containing an artificial hole of a 0.2 mm diameter which received SP or SSP fractured elsewhere than on the hole, and they had very high fatigue limits. The fatigue limit of specimens having an artificial hole under 0.2mm in diameter was determined by threshold condition for the non-propagation of fatigue cracks that emanated outside the drilled hole. From these results, it can be concluded that an artificial drilled hole under 0.2 mm in diameter can be made non-damaging by shot peening. KEY WORDS Shot peening, Bending, Fatigue limit, Surface defect, Residual stress, Non-propagating crack

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