Stability of residual stresses created by shot peening of pearlitic steel and their influence on fatigue behaviour

In this study the effect of shot peening on the fatigue lifetime of a near pearlitic microalloyed steel was investigated. The fatigue tests were run in strain control with parallel recording of stress relaxation and recovery of the work hardened surface zone at different total strain amplitudes exerted to the test specimens. These relaxation processes were followed versus cycle number up to half of the fatigue life time (N=Nf/2). Provided that the global plastic strain amplitude is lower than about 0.08% a noticeable increase in life time is seen. Lower plastic strain amplitude increases the life time. At small plastic strain amplitudes it was found that the fatigue life time could be increased more than tenfold by the shot peening process.