Abstract
This paper investigated the effect of shot-peening on fatigue strength
of spring steel for the high cycle fatigue (HCF) and very high cycle
fatigue (VHCF) to clarify the fatigue limit behavior of high strength
spring steel during service life. Hourglass shape specimens made of
spring steel (Si-Cr alloys) were prepared for the rotary bending fatigue
test. Actual local stresses were quantitatively calculated to compensate
for the stress amplitudes, through which it was clarified that the
shot-peening had strongly positive effects on the HCF strength, but
rather negative effect on the VHCF strength. The fish-eye fracturing
process confirmed that most fish-eye fractures arose at sites deeper
than the compressive residual stress zone, which did not prevent the
creation of the fish-eye, and the fatigue strength improvement in the
VHCF range could scarcely be shown as a result of the shot-peening
treatment.