超声滚压中的空化现象*

在超声滚压加工中引入切削液后可能会产生空化现象,由此产生的微射流和冲击波对超声表面强化将有积极作用。为研究超声滚压加工中空化现象是否存在及空化效应在超声滚压中的作用,本文首先分析了超声滚压中的空化阈值,然后进行了染色法试验和超声滚压后试样氧元素能谱分析,最后通过超声滚压加工对比试验研究了空化效应对加工后材料表面粗糙度和显微硬度的影响。研究发现,超声滚压加工中的声压幅值远大于空化阈值,满足空化存在的必要条件；超声滚压中发生了明显的卡纸染色现象,引入切削液后工件超声滚压加工表面氧元素含量显著提高,表明超声滚压中发生了空化现象。超声滚压加工中的空化效应能进一步降低工件表面粗糙度和提高表面显微硬度,有利于提高工件表面强化质量。本研究为空化效应在超声滚压中的积极利用提供了依据。

Cavitation in ultrasonic rolling

Cavitation may occur when cutting fluid is introduced into ultrasonic rolling, and the resulting micro-jets and shock wave will have a positive effect on ultrasonic surface strengthening. Whether cavitation exists and the effect of cavitation effect in ultrasonic rolling were studied in this work. Firstly, the cavitation threshold in ultrasonic rolling was analyzed. Then, the staining test and energy spectrum analysis of the oxygen element in the workpiece after ultrasonic rolling were carried out. Finally, the effect of cavitation on the surface roughness and microhardness of the processed material was investigated by a comparative ultrasonic rolling experiment. The results show that the pressure amplitude of ultrasonic wave in ultrasonic rolling is much larger than the cavitation threshold. So the necessary condition for the existence of cavitation is satisfied. Obvious staining occurs in ultrasonic rolling, and the oxygen element content in the workpiece surface after ultrasonic rolling is significantly increased when the cutting fluid is introduced. So the existence of cavitation in ultrasonic rolling is verified. The cavitation effect in ultrasonic rolling can further reduce the surface roughness and increase the surface microhardness of the workpiece, which is beneficial to improve the surface strengthening quality of the workpiece. This study provides a basis for the positive use of cavitation effect in ultrasonic rolling.