Mechanical properties and failure mechanisms of refill friction stir spot welds
Date
2021-11-01Author
Lakshmi Balasubramaniam, Guruvignesh
Boldsaikhan, Enkhsaikhan
Joseph Rosario, Gratias Fernandez
Ravichandran, Saravana P.
Fukada, Shintaro
Fujimoto, Mitsuo
Kamimuki, Kenichi
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Citation: Lakshmi Balasubramaniam, G.; Boldsaikhan, E.; Joseph Rosario, G.F.; Ravichandran, S.P.; Fukada, S.; Fujimoto, M.; Kamimuki, K. Mechanical Properties and Failure Mechanisms of Refill Friction Stir Spot Welds. J. Manuf. Mater. Process. 2021, 5, 118. https://doi.org/ 10.3390/jmmp5040118
Abstract
Refill friction stir spot welding (RFSSW) is an innovative solid-state welding technology
for aluminum structures. The presented study aimed to evaluate the mechanical properties of refill
spot welds and their failure mechanisms with the use of industrial test standards. The mechanical
properties of refill spot welds were compared with those of rivet joints with comparable joint sizes.
Static load tests indicated that RFSSW coupons demonstrate higher ultimate shear strengths but
slightly lower ultimate tension strengths than those of rivet coupons. Fatigue test results indicated
that both RFSSW coupons and rivet coupons demonstrate comparable performances during lowload-level fatigue lap shear tests but RFSSW coupons outperform rivet coupons during high-loadlevel fatigue lap shear tests. The failure mechanisms of refill spot welds were characterized in
terms of external loading, parent metal properties, and weld properties. Refill spot weld failures
included parent metal tensile failures, nugget pullouts, and interfacial failures. A refill spot weld may
demonstrate one or a combination of these mechanical failures. Although the mechanical tests of refill
spot welds demonstrated promising results with predictable failure mechanisms, the metallurgical
evolution involved in RFSSW remains a subject to study.
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