Improvement of Tensile Fatigue Strength of Duralumin Plate With a Hole by Cavitation Peening Using Opposed Cavitating Jets

Author:  Hitoshi Soyama and Fumio Takeo
Source:  ICSP-13
Doc ID:  2017102
Year of Publication:  2017
Abstract:  
Introduction: Cavitation impacts at bubble collapses cause severe erosion in hydraulic machineries such as pumps and valves. However, the cavitation impacts can be utilized for mechanical surface treatment in the same way of shot peening. The peening method using cavitation impacts is called as “cavitation peening”, or “cavitation shotless peening” as shots are not required [1]. In case of conventional cavitation peening, cavitation bubbles are generated by injecting a high speed water jet into water,i.e., a cavitating jet. In order to treat a relatively thin plate, treatment of both surfaces at the same time would be useful, as convex curve of the plate induced by the peening could be reduced. Thus, peening effect using opposed cavitating jets [2] to treat both side at the same time should be examined. In previous report [2], it was shown that the opposed cavitating jet could treat inner surface of a pipe which was placed in parallel to the cavitating jets. And also, when the opposed cavitating jets injected to the target, cavitation impacts at impinging area were enhanced, as the pressure at bubble collapse region was increased [3]. In order to enhance fatigue strength with a hole by cavitation peening using a single cavitating jet, a plate and/or attachment were required to make cavitation bubble collapse on the wall surrounding the hole with enhancing cavitation impacts, and it took time to treat. On the other hand, when the opposed jets were used, the bending fatigue strength and fatigue life of the duralumin plate with a hole was enhanced comparing with as machined specimen [2]. However, the fatigue strength and fatigue life of tensile test are not investigated.