Development of Shotless Peening System and Manufacturing Considering Preservation of Environment

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1.The cavitating jet in air was successfully realized using cavitation shotless peening system without a water-filled chamber. It was revealed that the cavitating jet in air was most powerful compared with a cavitating jet in water and a normal water jet in air.2.The erosion test and measurement of cavitation intensity were carried out at various conditions to measure the ability of cavitating jet in air, then the optimum condition of the cavitating jet was obtained.3.Several steel were peened by the cavitating jet in air, the residual stress was measured by an X-ray diffraction method. The introduction of compressive residual stress was demonstrated. It shows the possibility of the surface modification by using the cavitating jet in air.4.The optimum peening time was obtained from the relation of the peening time and the residual stress or the fatigue test at constant load changing with the peening time.5.In order to compare the proposed shotless peening considering the prevention of environment and the conventional shot peening, a rotating bending fatigue test was carried out, and it was shown that the improvement of fatigue strength by shotless peening was better than that of shot peening.6.In order to establish non-destructive testing method to evaluate the surface modification layer peened by the shotless peening, the residual stress and austenitic ratio were measured by using an X-ray diffraction method.7.The improvement of fatigue strength of gear was demonstrated by a bending fatigue test of gear tooth comparing the result of shot peening.8.In order to apply the shotless peening to various materials, the relation between the cavitation intensity and the materials properties was investigated, and the fundamental threshold level of materials for the cavitation impact was revealed.