High-speed micro-jet produced by cavitation collapse near the wall is the main mechanism of material damage, and cavitation pit is the most typical damage feature. The reason why high-pressure and high-speed micro-jet can only cause nano- and microscale cavitation pit is that the micro-jet is a short-term impact load of nano- and microscale, and the material shows size effect during the formation of pits. To further explore the cavitation damage characteristics and deformation mechanism of materials, the theoretical framework of indentation test and J-C constitutive model were adopted, and the size effect of materials during the process of cavitation pit formation was mainly considered, and the prediction models of cavitation impact load, impact pressure and velocity of micro-jet were established. The results showed that the equivalent stress and strain of cavitation pit and the impact pressure and velocity of micro-jet are only related to the diameter-to-depth ratio of pit without size effect, and also to the diameter of pit with size effect. Larger diameter and deeper depth of the pit infers greater cavitation impact load, and the influence of the pit diameter is more obvious. When considering the size effect, there is an additional size effect coefficient: 1+54hpα2μ2bdp2σJC2. In the selected size range of pit, the cavitation impact load, impact pressure and velocity of micro-jet predicted with size effect increase by 0.9408%-322.5% compared with those without size effect. The maximum increase ratio appears at the minimum of diameter-to-depth ratio of pit (dp = 2 μm and dh = 2 μm), that is, the smaller the pit diameter is and the greater the depth is, the greater the increase ratio is. Ten typical cavitation pits were selected for inversion analysis. The impact pressure and velocity of micro-jet with and without size effect are 473-1131 MPa and 355-848 m/s, and 427-604 MPa and 320-453 m/s, respectively. The predicted values increase by about 11%-88% when considering the size effect, and the micro-jet velocity predicted is closer to that observed by high-speed cameras, which confirms the necessity and rationality of size effect in the inversion analysis of cavitation pits.

中文翻译：

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材料的超声空化损伤特性及基于尺寸效应的空化冲击载荷预测模型。

气蚀在壁附近崩塌产生的高速微射流是材料破坏的主要机理，而气蚀坑是最典型的破坏特征。高压高速微射流只能产生纳米和微尺度的气蚀坑的原因是，微射流是纳米和微尺度的短期冲击载荷，并且材料在形成过程中显示出尺寸效应坑。为进一步探讨材料的空化破坏特性及变形机理，采用压痕试验和JC本构模型的理论框架，主要考虑了空化坑形成过程中材料的尺寸效应，并预测了空化影响的预测模型。确定了微射流的载荷，冲击压力和速度。结果表明，空化坑的等效应力和应变以及微射流的冲击压力和速度仅与无尺寸效应的坑的直径与深度之比有关，也与具有尺寸效应的坑的直径有关。坑的直径越大，深度越深，则说明空化冲击负荷越大，坑的直径的影响越明显。考虑尺寸效应时，还有一个附加的尺寸效应系数：1 +54hpα2μ2bdp2σJC2。在选定的坑尺寸范围内，具有尺寸效应的空化冲击载荷，冲击压力和微射流速度与没有尺寸效应的相比增加了0.9408％-322.5％。最大增加率出现在凹坑的直径与深度之比的最小值（dp = 2μm和dh = 2μm）时，即，凹坑直径越小，深度越大，增加率越大。选择了十个典型的空化坑进行反演分析。具有和不具有尺寸效应的微射流的冲击压力和速度分别为473-1131 MPa和355-848 m / s，以及427-604 MPa和320-453 m / s。考虑到尺寸效应，预测值增加了约11％-88％，并且预测的微射流速度更接近于高速相机观察到的速度，这证实了空化反演分析中尺寸效应的必要性和合理性。坑。分别。考虑到尺寸效应，预测值增加了约11％-88％，并且预测的微射流速度更接近于高速相机观察到的速度，这证实了空化反演分析中尺寸效应的必要性和合理性。坑。分别。当考虑尺寸效应时，预测值增加约11％-88％，并且预测的微射流速度更接近于高速相机观察到的速度，这证实了在空化反演分析中尺寸效应的必要性和合理性。坑。