Enhancing the aggressive intensity of a cavitating jet by introducing a cavitator and a guide pipe

Abstract

In order to enhance the aggressive intensity of a cavitating jet for practical applications, such as cavitation peening, a nozzle equipped with an additional nozzle upstream from the main nozzle, i.e., a cavitator, and a guide pipe downstream from the main nozzle was proposed and optimized. The aggressive intensity of the jet was evaluated by the residual plastic deformation, i.e., the radius of curvature, in duralumin plate specimens subjected to the jet perpendicullary. The radius of curvature can be considered to be directly related to the aggressive intensity of the jet, as the plastic deformation such as introduction of compressive residual stress and/or work hardening in metallic materials is important parameters on cavitation peening. The deformation occurs because the pressure due to cavitation impacts is beyond the yield stress of the specimens. It was demonstrated that a nozzle equipped with an optimized cavitator and optimized guide pipe increased the aggressive intensity of the jet by a factor of 4.2 without an increase of the jet power, compared to the jet obtained with a conventional nozzle with neither cavitator nor guide pipe, as the cavitator fed cavitation nuclei for the jet and the guide pipe enlarged the cavitation clouds of the jet.

The Use of Cavitation Peening to Increase the Fatigue Strength of Duralumin Plates Containing Fastener Holes

“…The expensive plunger pumps normally used for water jet cutting and peening [16] [17] are not required in this case. Recently, a fourfold increase in the aggressive intensity of a cavitating jet using a newly developed nozzle was successful demonstrated [18]. It was proposed to use this new nozzle for the experiments done in this work.…”

“…Since the main factor in improving the fatigue strength by peening is the introduction of compressive residual stress, the residual stresses at the surface of the plates and in the walls surrounding the holes were evaluated by an X-ray diffraction method. Figure 1 shows a schematic diagram of the peening system utilizing a cavitating jet [18]. The cavitating jet is produced by injecting a high-speed water jet into a water-filled chamber, i.e., tank A.…”

Using Cavitation Peening to Improve the Fatigue Life of Titanium Alloy Ti-6Al-4V Manufactured by Electron Beam Melting

“…The compressive residual stress at the surface introduced by peening was evaluated by X-ray diffraction stress measurements. Figure 1 shows a schematic diagram of the cavitation peening system used in the experiment [16]. Water stored in tank B is pressurized by a plunger pump with a maximum pressure of 35 MPa and maximum discharge of 3.0 × 10 −2 m 3 /min.…”

“…The nozzle is equipped with a cavitator and a guide pipe in order to enhance the aggressive intensity of the cavitating jet as shown in Figure 2. The geometry of the nozzle has been previously optimized [16]. The test section is open to the ambient air.…”

“…The injection pressure p 1 was kept constant at 30 MPa and the ambient pressure of the jet, p 2 , is equal to atmospheric pressure (0.1 MPa). The standoff distance from the upstream end of the nozzle plate to the surface of the specimen was 262 mm by reference to the previous study [16]. The nozzle was scanned across the specimen at a constant velocity for uniform treatment.…”