Finite Element Analysis of the Milling of Ti6Al4V Titanium Alloy Laser Additive Manufacturing Parts

Zhaohui Ren,Zhuhong Li,Yunhe Wang,Zhen Liu,Xingwen Zhang

doi:10.3390/app11114813

Abstract

This study aimed to analyze the defects of large residual stress in laser additive manufacturing metal parts by establishing a milling numerical simulation of Ti6Al4V titanium alloy thin-walled parts based on the Johnson-Cook constitutive model of Ti6Al4V titanium alloy, a modified Coulomb friction stress model, the physical chip separation criterion and other theories, combined with the finite element software ABAQUS. The influences of milling depth, initial temperature and milling speed on the forming quality of the formed part were analyzed. The results show that milling changes the residual stress distribution of the deposition layer, which can reduce or even change the residual tensile stress on the surface of the deposition layer produced by the additive manufacturing process into compressive stress, and the equivalent Mises stress decreases by 47% compared with the original forming surface. When the initial temperature increases from 20 °C to 400 °C, the maximum equivalent Mises stress of the milling surface decreases by 26%.

Highlights

Additive manufacturing technology directly produces parts without the need for specific tools, which can enhance the geometric freedom of the process and allow for the manufacturing of complex geometric shapes, as well as reduce time and production costs [1]
After each layer of sedimentation, there is a large residual stress, and as the number of sediments increases, the substrate is fully warmed up and the residual stress generated by the front layer is released when the back layer is deposited
The sedimentary layer as a whole is in a pull stress state; as the cutting process progresses, and with the gradual removal of sedimentary surface materials, the pull stress that remains on the surface of the sediment layer caused by the additive manufacturing process decreases or even becomes pressure stress

Summary

Introduction

Additive manufacturing technology directly produces parts without the need for specific tools, which can enhance the geometric freedom of the process and allow for the manufacturing of complex geometric shapes, as well as reduce time and production costs [1]. Compared with traditional manufacturing methods, additive manufacturing production costs and manufacturing cycles are reduced, and materials are well utilized This process has received significant attention from many industrial departments and has become a hot research topic [2,3,4,5]. Bordin et al, compared the semi-finish machining of forged Ti6Al4V and additively formed titanium alloys’ cutting performance under conditions. The results show that the processing difficulty of additive manufacturing alloys is greater than that of forged alloys, and the surface roughness value is higher, which causes more serious tool wear. The results show that, compared with traditional alloys, the additively manufactured samples have higher work hardening performance, and larger residual stresses are generated during the milling process [21]. The cutting force of selective laser melting is larger than forging, and the cutting force increases with the cutting speed, which is opposite to that of forging; this may be affected by the thermal softening characteristics of Ti6Al4V titanium alloy [22]

Objectives

Results

Conclusion