射流压力对淹没水射流冲击与空蚀效果的影响

目的探究淹没水射流对铝合金及铜合金材料的冲击与空蚀作用。方法为获得关键射流工况参数对射流冲击和冲蚀效果的影响,对射流压力、冲击时间和靶距的作用进行了研究。在较低压力条件下对材料表面的残余应力进行测量与分析;在较高压力时对材料表面的破坏形貌进行观测。结果残余应力随射流压力的增加而增加,当冲击时间为20 min,射流压力为40 MPa时,残余应力达到最大值91 MPa;在空蚀作用初期,试样表面出现尺寸较小、呈离散分布的空蚀坑,其为离散空泡冲蚀所致。随着空蚀作用的增强,材料表面的空蚀坑增大,同时出现塑性变形,当冲击压力为300 MPa,靶距为7cm,冲击时间为15 min时,达到最显著冲击效果。结论当压力较小时,淹没水射流可以强化金属表面;当压力较大时,淹没水射流可以使金属表面产生空蚀坑和塑性变形。尽管淹没水射流具有连续的射流速度分布,但材料表面的破坏更多地取决于空化现象。

Effects of Jet Pressure on Impingement and Cavitation Erosion Effects of Submerged Water Jet

The work aims to explore the impingement and cavitation erosion effects of submerged water jet on aluminium alloy and Cu alloy. Effects of jet pressure, impingement duration and target distance were studied to obtain the effects of key jet duty parameters on jet impingement and erosion. Residual stress on the material surface was measuremd and analyzed at low pressure and surface morphology of the material surface was observed at high pressure. Residual stress increased as the jet pressure increased, it was up to 91 MPa when the impingement duration was 20 minutes and jet pressure was 40 MPa. At the initial stage of cavitation erosion, dispersely distributed cavitation erosion pits were present on specimen surface, reflecting the effects of cavitation bubbles. With the enhancement of cavitation erosion effects, cavitation erosion pits on specimen surface expanded and plastic deformation was present simultaneously. It achieved the most significant impact when the impingement pressure was 300 MPa, target distance was 7 cm and impact duration was 15 minutes. The submerged water jet can strengthen the metal surface at low pressure and cause the metal surface to produce the pits and plastic deformation at high pressure. Surface morphology characteristic reflects the dominant effect of dispersed bubbles produced as a result of cavitation. Though the submerged water jet presents continuous jet velocity distribution, the damage on the specimen surface largely depends on cavitation phenomenon.