Fatigue Life Assessment of High-Strength Stainless Steels via Small Punch Testing

Small punch fatigue tests (SPFTs) were conducted on three high-strength stainless steels: X17CrNi15-2, 15-5PH, and PH13-8Mo. The SPFT valley displacement-versus-SPFT life curves for the three stainless steels exhibited three different stages. Power-law relationships were obtained to characterize the maximum forces with SPFT lives for different stainless steels. The fracture mechanisms of the tested SPFT specimens were characterized via scanning electron microscopy, which was dependent on the materials and applied loads. Finite element analyses were performed to obtain the equivalent local stresses and strains. A simplified critical plane-strain energy density (SED) criterion was used for the SPFT life assessment by correlating the FE-obtained strain energy density with the SPFT life. The SED values for the SPFT life were in the following order: PH13-8Mo > 15-5PH > X17CrNi15-2.