SUMMARY
Mechanical surface enhancement techniques are utilized to improve the fatigue life of formed and machined components by inducing a compressive residual stress in the workpiece surface and subsurface. Liquid cavitation peening is a newer surface enhancement technique that utilizes a cavitating stream to induce compressive residual stresses in the workpiece. As the cavitation bubble collapses on the workpiece surface, a large pressure wave is generated, creating a compressive residual stress in the workpiece. Oil is presented as a preferred fluid as it erodes less of the surface during impact. New research needs to be conducted to gain a better understanding of how process parameters affect the mechanical properties of the workpiece. This thesis presents a new process, oil jet cavitation in air, and evaluates its effectiveness on the physical and mechanical properties of the workpiece surface. An experimental study is carried out on a novel experimental prototype system to determine the effects of the process parameters (stand-off distance, traverse speed, pass to pass overlap) on the workpiece characteristics. The workpiece material utilized throughout is 2024-T3 Aluminum. The results of this study demonstrate that all three process parameters, standoff distance, traverse speed, and pass to pass overlap, are statistically significant with respect to deflection, microhardness, and mass loss. The process was able to induce -155 MPa compressive residual stress, improve micro hardness by 21%, limit mass loss to 1.3 µg/s, and cause a 0.010 inch (0.254 mm) deflection in the strip. The process did not create a change in the surface area roughness (Sa). The acoustic emission magnitude is suggested as a good indicator of deflection, micro hardness, and mass loss over the range of the values tested in the experiment. An explanation of how each process parameter affects the surface characterstics is discussed, with a complete analysis of variance provided for each.