Surface integrity and fatigue analysis of shot-peening for 7055 aluminum alloy under different high-speed milling conditions

Changfeng Yao,Xingtang Dou,Daoxia Wu,Zheng Zhou,Jiyin Zhang

doi:10.1177/1687814016674628

Changfeng Yao, Xingtang Dou + Show 3 more

Open Access

https://doi.org/10.1177/1687814016674628

Copy DOI

Abstract

To study the effect of different milled surfaces on shot peening surface integrity (roughness, residual stress, hardness, and microstructure), research on the change of surface integrity is carried out using the same shot peening process for different milling surfaces of 7055-T77 aluminum alloy. Surface integrity measurements, fatigue fracture analysis, and fatigue life tests are conducted to reveal the effect of surface integrity on crack initiation and fatigue life. The results show that shot peening can reduce the dispersion and instability of surface integrity brought by milling processing, although it increases the surface roughness; the maximum residual compressive stress and depth of residual stress layer increase significantly after shot peening, and the residual stress and hardening distribution are very good; larger surface roughness and irregular surface scratches of milling samples before shot peening easily lead to cracks and gouges produced on shot peening surface.

Highlights

Due to the advantage of high strength, low density, and satisfactory processing performance, high-strength aluminum alloy is widely used in the manufacture of the main structure and load bearing components in the aerospace industry.1 7055 aluminum alloy is an outstanding representative of a high-strength aluminum alloy in aircraft; compared to 7050 aluminum alloy, 7055 aluminum alloy has higher strength, better fracture toughness, and higher resistance to stress corrosion cracking.[2]Surface integrity adopts surface geometric features, micromechanical properties, and microstructure of surface metamorphic layer to measure the comprehensive performance of machined parts
Han Huang[6] studied the machining characteristics of nitinol in high-speed milling through a series of systematic high-speed milling experiments; the results show that with the increase in cutting speed, the better will be the surface quality, the smaller will be the magnitude of work hardening
In order to get the optimum milling parameters of highspeed milling 7055 aluminum alloy, Yao et al.[9] conducted the orthogonal experiment and finite element (FE) simulation to research the effect of milling parameters on surface integrity; the results show that when milling speed, feed per tooth, milling depth, and milling width are 1100 m/min, 0.02 mm/z, 0.7 mm, and 6 mm, respectively, good surface quality is obtained and the magnitude of surface metamorphic layer will be larger

Summary

Introduction

Due to the advantage of high strength, low density, and satisfactory processing performance, high-strength aluminum alloy is widely used in the manufacture of the main structure and load bearing components in the aerospace industry.1 7055 aluminum alloy is an outstanding representative of a high-strength aluminum alloy in aircraft; compared to 7050 aluminum alloy, 7055 aluminum alloy has higher strength, better fracture toughness, and higher resistance to stress corrosion cracking.[2]. Surface integrity adopts surface geometric features, micromechanical properties, and microstructure of surface metamorphic layer to measure the comprehensive performance of machined parts.

Objectives

Conclusion