Simulation Analysis Of Surface Residual Stress For Ti-6Al-4V Titanium Alloy Cryogenic Machining Using Liquid Nitrogen

Titanium alloy materials represented by Ti-6Al-4V are widely used in core industrial fields such as aerospace and marine equipment due to their advantages of high strength,good corrosion resistance,and strong load-bearing capacity.A large number of studies have shown that under normal cutting conditions,the residual stress state of the titanium alloy machining surface is mainly tensile stress,which greatly affects the component geometry,service life,fatigue strength,and so on.How to effectively improve this stress state has become an urgent problem to be solved in the processing of advanced titanium alloy parts.The introduction of liquid nitrogen cooling in the processing of titanium alloys significantly strengthens the local cooling environment of the cutting,accelerates the cutting heat dissipation,and helps weaken a series of harmful effects caused by cutting heat,such as the generation of thermally induced surface tensile stress.Therefore,it is necessary to further analyze the effect of liquid nitrogen cooling on the distribution of residual stress state on the processed surface of Ti-6Al-4V.This article has conducted in-depth research and analysis on the residual stress of the processed surface in the cryogenic processing of liquid nitrogen from basic theory and numerical analysis.The main contents include:(1)Mechanism analysis of the effect of cryogenic processing of Ti-6Al-4V on residual stress distribution in liquid nitrogen.Based on the force-heat coupling theory of surface residual stress,referring to Waldorf’s slip line model,the mechanical surface stress and thermal stress are combined to predict the residual stress of the processed surface.Based on the cutting area separation model,a combination of cutting deformation zone model and ploughing zone model is used to analyze the generation mechanism of residual stress.(2)Based on the cutting area separation model,a new finite element model of orthogonal turning under dry cutting and liquid nitrogen low temperature cutting conditions was established,and the processed surface was still affected by the low temperature of liquid nitrogen during low temperature machining of Ti-6Al-4V by liquid nitrogen Problem,the traditional liquid nitrogen low temperature finite element analysis model was optimized and verified through experiments.At the same time,it provides a valuable reference for the related research of surface processing residual stress in low temperature processing.(3)Based on the finite element prediction model of the residual stress of the liquid nitrogen cryogenic machining surface of Ti-6Al-4V titanium alloy,the influence of cooling factors,cutting parameters and tool parameters on the distribution of residual stress on the machining surface was analyzed.Simulation analysis of the effect of different cooling methods on the surface temperature of the processed workpiece.It is determined that the surface temperature of the workpiece processed by liquid nitrogen cooling is lower.Compared with dry cutting conditions,the restrictions on the selection of cutting parameters for Ti-6Al-4V machining are relaxed to a certain extent.