Zheng Jianxin, Guo Yonglei, Zhu Lixin, Deng Hanlin, Shang Yingju
College of Mechanical & Power Engineering, Henan Polytechnic University, Jiaozuo 454003, PR China.
College of Mechanical & Power Engineering, Henan Polytechnic University, Jiaozuo 454003, PR China.
Ultrasonics. 2021 Aug;115:106456. doi: 10.1016/j.ultras.2021.106456. Epub 2021 Apr 25.
The ultrasonic cavitation effect can improve the machining quality. In order to study the formation process of cavitation in two-dimensional ultrasonic rolling process (TDUR) and its influence on processing, a simulation and experimental study of cavitation in TDUR was conducted to further improve the processing quality. The pressure distribution model and the cavitation model of the two-phase mixed flow around the roller in TDUR were constructed by combining the ideal bubble dynamics theory. And the cavitation intensity was evaluated by the vapor volume fraction (VVF). The formation process of cavitation effect in the flow field was analyzed by finite element analysis, and the effects of different inlet pressures and different pipe structures on the cavitation were studied. TDUR experiments were carried out to study the changes of surface roughness and residual stress of the workpiece under the effect of ultrasonic cavitation, and the positive effect of cavitation effect was verified. The simulation results show that the cavitation effect mainly occurs in the left half of the roller and the rolling area, and the cavitation in the left half of the roller changes from transient cavitation to steady-state cavitation as the inlet pressure increases. Different inlet pressures in the rolling region always show periodic transient cavitation, with obvious cavitation bubbles generation, expansion and collapse processes. The lower the inlet pressures in the straight and inverted trumpet pipe, the stronger the transient cavitation effect. The experimental results show that the cavitation effect can further improve the surface strengthening quality of the workpiece. Under the same process parameters, the surface roughness of the workpiece can be reduced by up to 47.7% and the residual compressive stress of the surface can be increased by up to 10.2%. Therefore, the cavitation effect can be applied in ultrasonic rolling process to further improve the surface strengthening quality, and the straight pipe at atmospheric inlet pressure is preferred in TDUR.
超声空化效应可以提高加工质量。为了研究二维超声滚压加工过程（TDUR）中空化的形成过程及其对加工的影响，对TDUR中的空化进行了模拟和实验研究，以进一步提高加工质量。结合理想气泡动力学理论，建立了TDUR中轧辊周围两相混合流的压力分布模型和空化模型。并通过蒸汽体积分数（VVF）评估空化强度。通过有限元分析对流场中空化效应的形成过程进行了分析，研究了不同入口压力和不同管道结构对空化的影响。进行了TDUR实验，研究了超声空化作用下工件表面粗糙度和残余应力的变化，验证了空化效应的积极作用。模拟结果表明，空化效应主要发生在轧辊左半部和轧制区域，随着入口压力的增加，轧辊左半部的空化从瞬态空化转变为稳态空化。轧制区域不同的入口压力总是呈现周期性的瞬态空化，有空化气泡明显的产生、膨胀和溃灭过程。直管和倒喇叭管中入口压力越低，瞬态空化效应越强。实验结果表明，空化效应可以进一步提高工件的表面强化质量。在相同工艺参数下，工件表面粗糙度可降低达47.7%，表面残余压应力可增加达10.2%。因此，空化效应可应用于超声滚压加工过程中以进一步提高表面强化质量，在TDUR中大气入口压力下的直管是首选。
