Study on the surface integrity of ultrasonic cavitation-assisted WEDM-LS under Rayleigh-Plesset model

In this paper, a novel ultrasonic cavitation (USC)-assisted low-speed WEDM (WEDM-LS) process is proposed to address the issue of low machining efficiency and the recast layer when cutting thick nickel-titanium shape memory alloy (NiTi SMA) workpiece. Based on the Rayleigh-Plesset model, the machining mechanism of USC-assisted WEDM-LS is explored. Firstly, considering the influence of WEDM on vapor volume fraction (VVF) in the flow field, the impact strength of microjet, which is caused by collapsing near-wall acoustic bubbles on the workpiece surface, is studied. In addition, the influence of a single bubble collapse microjet impacting on the workpiece surface and recast layer is simulated and analyzed based on water hammer effect. The results demonstrated that the microjet is useful for removing workpiece material. The verification experiment results showed that, compared to traditional WEDM-LS, the material removal rate (MRR) of USC-assisted WEDM-LS increases by 31.65%, the thickness of the recast layer reduces by 20.39%, and the degree of burn surface is effectively reduced. These machining characteristics indicate that the surface integrity of the workpiece is improved greatly.