Effect of assisted transverse magnetic field on distortion behavior of thin-walled components in WEDM process

Machining performance of thin-walled components made by aeronautical difficult-to-process materials is a significant issue in the aviation manufacturing industry. Although wire electric discharge machining-low speed (WEDM-LS) is one of typical non-contact machining processes without macro cutting force, which does well in removing hardness and brittleness materials via pulsed discharge at high temperature, but few researchers have studied the thermal distortion behavior leading to a considerable geometric error in the WEDM-LS of thin-walled components. In this paper, a transverse magnetic field assisted method is applied for affecting the uniformity of discharge point distribution so as to reduce the distortion in WEDM-LS processing thin-wall component. First, the generation mechanism of this new distortion behavior and the impact mechanism of transverse magnetic field (TMF) on distortion are demonstrated by theoretical analysis. In order to further figure out the distortion behavior in the TMF-WEDM process, a new thermo-physical model considering the discharge point distribution is established to simulate temperature field, residual stress field and distortion profiles. Then a large number of Taguchi experiments are carried out to investigate the influences of process parameters including pulse discharge energy (pulse on time, pulse off time, and current) and magnetic field strength on distortion in WEDM-LS. To comparatively analyze simulated and experimental results, the accuracy of established thermo-physical model is verified within a relative error of 18.38 % in distortion. Moreover, it can be revealed that transverse magnetic field contribute to significantly improve the longitudinal distribution uniformity with maximum increase of 12.32% at magnetic field strength: 0.15 T, leading to significant reductions of 32.77% in distortion and 22.68% in recast layer. Eventually, we also presented the variation of residual stress and recast layer along thickness direction under different distortion behavior, which are in good agreement with that of distortion behavior.