EFFECT OF SHOT PEENING ON BENDING FATIGUE STRENGTH OF SPRING STEEL SPECIMENS CONTAINING AN ARTIFICIAL SURFACE DEFECTS

摘要

Effects of shot peening on the bending fatigue strength of spring steel (SUP9A) specimens with 500HV 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 of 0.2, 0.3, 0.4 and 0.8 mm diameter. Then, bending fatigue tests were carried out with the specimens with a stress ratio of zero. The bending fatigue limits of specimens containing a drilled hole were increased 34-44% by SP or 68-77% by SSP, respectively. The specimens containing a drilled hole under 0.2-0.3 mm in diameter had very high fatigue limits almost equal to those of shot-peened non-defect specimens. From these results, it can be concluded that a drilled hole under 0.2-0.3 mm in diameter can be made non-damaging by SP or SSP.