Study On Damage Types And Formation Of Iridescent Ring During Cavitation Erosion

Cavitation erosion is the main damage type of hydraulic machineries in high rate fluids, including micro-jet impact and thermal damage. But because of its complexity, the mechanism is still remained as a controversial topic.In this paper, by combining the experimental and numerical methods, three types of materials, namely brittle material (quartz glass), plastic material (polytetrafluoroethylene or PTFE) and elastic-plastic material (Q235 steel) are used to investigate the formation mechanism of cavitation damage types and iridescent ring on steel surface. All the work can help to know the cavitation resistance of different materials and provide new theoretical and experimental references for the study of local thermal effect during cavitation erosion. In addition, the main innovative points of this paper are to simulate the formation process of iridescent ring based on the thermo-solid coupling theory, and obtain the information about temperature distribution, value and location of highest temperature, which are also verified by experimental test.The whole research in this paper has shown that the numerical results are in well agreement with the experimental results. The main conclusions are as follows:the formation of different cavitation damage types was dependent on the failure mode and crystal structure change of materials with different physical properties under an instantaneous large impact; iridescent ring was the unique feather of steel caused by thermal effect during cavitation erosion, and its size with colors would be affected by particles in the experimental medium; meanwhile, the experienced temperature of ring area with a shape of hemisphere could reach as high as 1380℃ to 1450℃, and the location of highest temperature was in the stress concentration point rather than the largest elastic-plastic deformation point (or the bottom of erosion pit), which indicated that the iridescent ring is caused by the combined action of large plastic deformation in very short time and stress wave.