EFFECTS OF SHOT PEENING ON TORSIONAL FATIGUE LIMIT FOR SPRING STEEL SPECIMENS CONTANING AN ARTIFICIAL SURFACE DEFECT

摘要

Effects of shot peening on the torsional fatigue limit of spring steel specimens containing an artificial small hole were investigated. A drilled hole of 0.2 - 0.8 mm in diameter or a semi-circular slit with diameter of 0.3 and 0.6 mm was introduced on the specimen surface. Then, torsional fatigue tests were carried out with the specimens. The torsional fatigue limits of specimens containing a drilled hole or a semi-circular slit were increased by SP 25 - 64% or 156 - 186%, respectively. The specimens containing a drilled hole under 0.3 mm in diameter and a semi-circular slit under 0.3 mm in diameter had very high fatigue limits almost equal to those of non-defect shot-peened specimens. From these results, it can be concluded that a drilled hole under 0.3 mm in diameter and a semi-circular slit under 0.3 mm in diameter can be made non-damaging by SP.