Effects of TVSR process on the dimensional stability and residual stress of 7075 aluminum alloy parts

Bianhong Li,Yan Xu,Zhongjun Shi,Zhang Zhang

doi:10.1515/rams-2021-0048

Bianhong Li, Yan Xu + Show 2 more

Open Access

https://doi.org/10.1515/rams-2021-0048

Copy DOI

Abstract

Abstract Residual stress generated during the blank forming and machining process significantly influences the dimensional stability of the mechanical parts. The equivalent bending stiffness and thermal vibration stress relief (TVSR) are two factors that affect the deformation of thin-walled workpiece. To increase the machining accuracy, on the one hand, increase the equivalent bending stiffness in manufacturing, and on the other hand, usually conduct the stress relief process to reduce the residual stress in manufacturing. In the present study, morphology optimization and TVSR process are conducted on a thin-walled part Specimen B of 7075 aluminum alloy to control the residual stress and machining deformation before finish machining. As a contrast, Specimen A is machined in one step. The deformations vary with time of Specimen A and B are measured. The corresponding finite element model is built to further study the stress and distortion during the machining process. Results showed that (1) deformation decreased with the increase of equivalent bending stiffness, compared with Specimen A, the maximum deformation of Specimen B decreased by 58.28%. (2) The final maximum deformation of Specimen B can be reduced by 38.33% by topology reinforcement to improve the equivalent stiffness and TVSR to reduce the residual stress.

Highlights

Residual stress is the internal stress for the self-equilibrium, which remains in the body after eliminating the external force or uneven temperature field [1]
The simulation results of equivalent stiffness before and after topology optimization are presented in Figure 10 and Table 3
Specimen A is one time cutting to the final shape, and after Specimen B first cutting 96 h, the thermal vibration stress relief (TVSR) is conducted to control the residual stress and machining deformation

Summary

Introduction

Residual stress is the internal stress for the self-equilibrium, which remains in the body after eliminating the external force or uneven temperature field [1]. The stress state in the material significantly determines the mechanical behavior and fatigue life [3]. It is the reflection of strain energy that introduced the external energy field [4], and it reaches a steady state before the shape is changed again [5]. The stress is released and redistributed due to the removal of the material, which causes the dimension change of the workpiece [6]. To reduce the machining deformation, adding stiffeners to increase bending stiffness is the simple way to first think [8]. It is revealed that the machining deformation decreases as the equivalent bending stiffness increase in the length direction. Li et al [11] found that bending stiffness affects the contribution of machininginduced residual stress (MIRS) and initial residual stress (IRS) to machining deformation of the thin-walled part

Methods

Results

Conclusion