Use of Low Plasticity Burnishing as a Replacement for Shot Peening for Naval Components

Traditional shot peening is often used on U.S. Navy components to increase resistance to fatigue crack initiation. Low plasticity burnishing (LPB) is being investigated as a replacement for shot peening due to a number of advantages: increased depth of residual compressive stress, enhanced surface finish, and ability to perform the operation without set up of additional containment areas. The depth of residual compressive stress has been measured using shallow-hole and deep-hole drilling methods and shows approximately a 10x increase compared to shot peening. Knoop microhardness testing was performed to correlate hardness measurements with compressive residual stress. It will also be used as a secondary means of verifying the plasticity depth effects of LPB via work hardening when hole drilling methods cannot be employed (e.g. finished components). Microstructural characterization was also performed to confirm no deleterious changes (e.g. micro-cracking, cold laps, smearing, etc.) occurred during the LPB process.