Effects of Refill Friction Stir Spot Weld Spacing and Edge Margin on Mechanical Properties of Multi-Spot-Welded Panels

Guruvignesh Lakshmi Balasubramaniam,Enkhsaikhan Boldsaikhan,Mitsuo Fujimoto,Shintaro Fukada,Kenichi Kamimuki

doi:10.3390/jmmp4020055

Guruvignesh Lakshmi Balasubramaniam, Enkhsaikhan Boldsaikhan + Show 3 more

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https://doi.org/10.3390/jmmp4020055

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Abstract

Refill friction stir spot welding (RFSSW) is an emerging technology for joining aerospace aluminum alloys. The aim of the study is to investigate the effects of the refill friction stir spot weld spacing and the edge margin on the mechanical properties of multi-spot-welded AA7075-T6 panels. AA7075-T6 is a baseline aerospace aluminum alloy used in aircraft structures. The study employs an innovative robotic RFSSW system that is designed and developed by Kawasaki Heavy Industries (KHI). The experimental strategy uses Design of Experiments (DoE) to characterize the failure loads of multi-spot-welded panels in terms of the spot weld spacing, edge margin, and heat-affected zone (HAZ) of the spot weld. The RFSSW process leaves behind a thermal “imprint” as HAZ in heat-treatable aluminum alloys. According to the DoE results, larger spot weld spacings with no HAZ overlap produce higher failure loads of multi-spot-welded panels. On the other hand, edge margins that are equal to or less than the spot weld diameter demonstrate abnormal plastic deformations, such as workpiece edge swelling and weld crown dents, during the RFSSW process. The larger edge margins do not demonstrate such abnormal deformations during the welding process.

Highlights

The consumption of aluminum alloys is growing in many industries, as they are lightweight and easy to recycle
AA7075-T6 is a baseline aerospace aluminum alloy used in aircraft structures [24]
AA7075 is a baseline aerospace aluminum alloy used in aircraft structures

Summary

Introduction

The consumption of aluminum alloys is growing in many industries, as they are lightweight and easy to recycle. This growth creates the need for better ways of welding aluminum alloys with satisfactory mechanical and metallurgical properties [1]. Aluminum alloys welded with conventional fusion welding techniques exhibit the formation of brittle intermetallic compounds that usually cause severe intermetallic cracking [2]. It is difficult or almost impossible to weld high-strength aluminum alloys with conventional fusion welding techniques. Solid-state welding techniques, such as ultrasonic welding and friction stir welding, are better alternatives to welding aluminum alloys. Macwan et al [4] characterized the mechanical and microstructural properties of ultrasonic spot welds of a rare earth-containing ZEK100 magnesium alloy and AA5754

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