The finite element analysis of machining characteristics of titanium alloy in ultrasonic vibration assisted machining

Abstract

Titanium alloy Ti6Al4V, an alpha-beta alloy, possesses many advantageous properties, such as high special strength, good resilience and resistance to high temperature and corrosion, fracture resistant characteristics and so on, being widely used in aerospace, biomedical and chemical industry. However, its machinability is still a challenge due to its low thermal conductivity, low elastic modulus and high chemical reactivity. As a novel and effective machining method, ultrasonic vibration assisted machining (UVAM) can effectively improve the machining performance of workpieces, which is widely used in the field of titanium alloy machining. A two-dimensional cutting finite element modeling methodology for orthogonal cutting titanium alloy Ti6Al4V was established to analyze the comparisons between conventional machining (CM) and ultrasonic vibration assisted machining and the effects of frequency and amplitude. The simulation results showed that (1) UVAM more easily formed serrated chip than that of CM. The chip segmentation coefficient GS which could quantitatively characterize the segmentation degree of chip showed an increasing trend with the increase of amplitude. (2) The cutting force curve of UVAM had periodic pulse fluctuation due to the effects of vibration in x-direction and y-direction. The main cutting force and the thrust force of UVAM showed the further decrease trend with the increase of frequency and x-direction amplitude. However, the y-direction amplitude made the contrary trend for the cutting force. (3) Meanwhile, with the increase of y-direction amplitude, the plastic and friction dissipation energies increased obviously. The introduction of ultrasonic vibration results in complex changes in the tool-chip contact, mechanical and temperature characteristics of the workpiece. Choosing the suitable vibration parameters will contribute to improving the machinability of titanium alloys.