Cavitation Shotless Peening for Improvement of Fatigue Strength

Author:  Soyama, Odhiambo and Saito
Source:  Conf Proc: ICSP-8 Sept. 16-20, 2002 Garmisch-Partenkirchen, Germany
Doc ID:  2002056
Year of Publication:  2002
Authors Hitoshi Soyama, Dan Odhiambo and Kenichi Saito Department of Machine Intelligence and Systems Engineering, Tohoku University, Sendai, Japan Abstract This paper gives an overview of the art, craft and science of "Cavitation Shotless Peening" as a new method of turning the traditional negative effects of cavitation in hydrodynamic machinery to more positive industrial applications. Impact at cavitation bubble collapse can be used to improve the fatigue strength just as the same way as shot peening. Cavitation impacts can peen the surface without the use of shot. Hence, it is a king of shotless peening, and herein termed as Cavitation Shotless Peening (CSP). The peened surface by CSP is less rough compared with shot peening, since there is no solid body collision involved. In the present study, cavitation impacts were produced by a submerged high speed water jet with cavitation, i.e., a cavitating jet. The cavitating jet differs completely from a normal water jet in air. To explore the potentials of CSP as a means of inducing surface compressive residual stress and subsequently increasing fatigue strength of materials, silicon-manganese alloy (JIS SUP7) and an aluminum alloy (JIS AC4CH) specimens were peened by a cavitating jet. The residual stress was measured by an X-ray diffraction method. Experimental results confirmed that the rotating beam (R = -1) fatigue strength of silicon-manganese alloy increased by 41% while that of aluminum alloy increased by 56% in comparison with non-peened specimens.

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