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TC4 titanium alloy is widely used in aerospace, petrochemical, pharmaceutical and other fields, which accounts for about 60% of the current titanium alloy products. Water Cavitation Peening (WCP) is a new material surface modification process and has great development potential. The improvement of the water cavitation peening is severely limited by the correlation and coupling between process parameters. Therefore, the influence law of each process parameter is the key problem that needs to be resolved. TC4 titanium alloy as research object is took and four main process parameters of WCP under four working conditions is construct (four factors and four levels orthogonal). The influence of process parameters on three evaluation indexes is studied, such as the surface residual stress, the surface roughness and the microhardness. Then, the fuzzy mathematics comprehensive evaluation is used to optimize. Results show that the peening time has the greatest influence on strengthening effect and the nozzle diameter has the least. The optimized combination is that the nozzle diameter is 1.4 mm, the incident pressure is 40 MPa, the dimensionless target distance is 72.5 and peening time is 27.5 min. The corresponding surface residual stress, the surface roughness and the microhardness can reach −612 MPa, 0.76 μm, and 405 HV respectively.

Cavitation generation methods have been applied in multifarious directions due to their diversity. And scholars have carried out numerous researches and discussions on cavitation generation methods. The purpose of this study is to explore the generating mechanism and evolution law of volumetric alternate cavitation (VAC). In the VAC, the liquid water is placed in an airtight container with variable volume. With the volume alternately changes, the liquid water inside the container continues to cavitate. In this study, the mixture turbulence model and in-cylinder dynamic grid model were used to apply computational fluid dynamics (CFD) simulation of volume alternate cavitation. In the simulation, the cloud images at 7 heights on the central axis are monitored, and the phenomenon and mechanism of height and eccentricity are analyzed detailedly. By using the method of cavitation flow visualization (CFV), the generating mechanism and evolution law of cavitation are clarified. The synergistic effects of experiments and high-speed camera capture confirm the simulation. In the experiment, the volume change stroke of the airtight container is 20 mm, the volume change frequency is 18 Hz, and the shooting frequency of the high-speed camera is set to 10000 fps. The results show that the position of occurring cavitation phenomenon has a reasonable law during the whole evolution cycle of the cavitation cloud. It is evident that a cycle of volume alternation corresponds to the generation, development and collapse stages of cavitation bubbles.

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Cavitation generation methods have been used in multifarious directions because of their diversity, and numerous studies and discussions have been conducted on cavitation generation methods. This study aims to explore the generating mechanism and evolution law of volume alternate cavitation (VAC). In the VAC, liquid water is placed in an airtight container with a variable volume. As the volume alternately changes, the liquid water inside the container continues to cavitate. Then, the mixture turbulence model and in-cylinder dynamic grid model are adopted to conduct computational fluid dynamics simulation of volume alternate cavitation. In the simulation, the cloud images at seven heights on the central axis are monitored, and the phenomenon and mechanism of height and eccentricity are analyzed in detail. By employing the cavitation flow visualization method, the generating mechanism and evolution law of cavitation are revealed. The synergistic effects of experiments and high-speed camera capturing confirm the correctness of the simulation results. In the experiment, the volume change stroke of the airtight container is set to 20 mm, the volume change frequency is 18 Hz, and the shooting frequency of the high-speed camera is set to 10000 FPS. The experimental results indicate that the position of the cavitation phenomenon has a reasonable law during the whole evolution cycle of the cavitation cloud. Also, the volume alternation cycle corresponds to the generation, development, and collapse stages of cavitation bubbles.