Improvement in Fatigue Strength of Silicon Manganese Steel SUP7 by Using a Cavitating Jet

摘要

It is possible to strengthen metallic materials by using a cavitating jet to introduce compressive residual stress in the material surface, since the impact of collapsing cavitation bubbles peen the surface in the same way as shot peening. In order to demonstrate the improvement in the fatigue strength of a material by suing a cavitating jet, an experimental study was carried out. Silicon manganese steel JIS SUP7 was chosen as a test material, since JIS SUP7 is used as a spring material after shot peening. The specimens were exposed to the cavitating jet with upstream pressure P_1=20 MPA, downstream pressure p_2=0.28 MPa, the cavitation number σ ～=p_2/p_1=0.014, the nozzle throat diameter d=0.842 mm and the standoff distance s=31 mm. The scanning speed v at which the compressive residual stress took the most significant value was 0.25 mm/s. The compressive residual stress was introduced in the entire surface peened by the cavitating jet under the above conditions.