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Mechanical behaviour and failure mechanism of resistance spot welded aluminium and copper joint used in the lightweight structures

Fakhri Marwah Sabah, Al-Mukhtar Ahmed, Mahmood Ibtihal A.

Diagnostyka

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2024

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Vol. 25, No. 2

art. no. 2024207

EN

Recently, dissimilar metals have found applications in the process of resistance spot welding (RSW), particularly within the electric vehicle industry. Notably, copper and aluminum have gained significant importance in these sectors due to their advantageous characteristics for the industry requirements. The mechanical behavior of these materials is essential to maintaining structural integrity. The study aims to estimate the mechanical behavior of dissimilar RSW joints and optimize welding parameters for Cu-Al joints. Hence, understanding the joining processes in the electric vehicle industry to design reliable components. Combining different types of materials, such as T2-grade commercially pure copper sheets and aluminum AA1050 with the same thickness of 1 mm has been welded. The determination of optimal welding conditions takes into account material thicknesses and types. Through tensile-shear testing, welding parameters that yield maximal joint strength were identified. Using Minitab 19 software, the Taguchi method helped achieve optimized welding parameters. The hardness, fracture characteristics, and weld strength have been investigated. Hardness measurements were conducted across the nugget thickness and surface, offering insights into potential failure modes. The welding process involves the transition to a liquid state for the aluminum components, resulting in the formation of intermetallic compounds. Consequently, crack initiation was observed within the aluminum segments, leading to a plug-out fracture mechanism. In contrast, copper exhibits superior strength and hardness compared to aluminum, where increased hardness correlates with heightened strength. The discrepancy in hardness, especially the lower values observed on the aluminum side, caused fractures to appear within the heat affected zone (HAZ). Subsequently, this fracture propagated until pull-out failure was realized. The study revealed that dissimilar joining of Cu and Al resulted in an ultimate tensile stress of 26 MPa, while similar joining of copper showcased a strength of 98 MPa. Additionally, the symmetric join in aluminum exhibited a strength of 93 MPa. The maximum tensile shear force is equal to 512 N at a maximum welding current of 14000 A. The pull-out failure mode occurs in the Cu-Al RSW joint. The maximum hardness was noted in the fusion zone (FZ). Relevant literature sources have supported and confirmed these outcomes.

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Resistance spot welding of AISI-316L SS and 2205 DSS for predicting parametric influences on weld strength – Experimental and FEM approach

Vignesh K., Perumal A. Elaya, Velmurugan P.

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 4

1029--1042

EN

The present study reports the effects of RSW process parameters like heating cycle, welding current and electrode tip diameter on the tensile shear strength and nugget size of dissimilar metal welding of 2205 duplex stainless steel (DSS) and AISI-316L stainless steel sheets. Tensile shear tests were conducted to access the tensile shear strength and associated physical variations of the nugget formed. Finite element (FE) simulation of the tensile–shear test was performed using ABAQUS explicit FE software. The finite element results were compared with experimental results through the aid of graphical representation by com-paring the obtained stress–strain values for validation. The resistance spot welds are subjected to Vickers microhardness test and identified that hardness of HAZ is less for AISI-316L and high in DSS-2205 as compared to respective base metal, moreover heteroge- neous hardness values obtained in the weld metal zone (WMZ) exhibits higher hardness in ASS-316L and low hardness in DSS-2205 side as compared with base metal. Furthermore, SEM fractography indicates that the failure of tensile shear spot welded specimen occurs in the ductile mode of fracture.

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Ocena wytrzymałości połączeń zgrzewanych oporowo z blach tytanowych GR 3 i GR4

Różycka J., Derlatka A., Dyner M.

Rudy i Metale Nieżelazne Recykling

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2015

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R. 60, nr 11

603--609

PL

Celem artykułu była ocena wytrzymałości złączy wykonanych z blach z tytanu grade 3 i grade 4 o grubości 0,4 mm. Blachy łączono w sposób zakładkowy przez zgrzewanie oporowe. Złącza zgrzano pojedynczą zgrzeiną RSW. Dokonano wyboru optymalnych parametrów zgrzewania. Ocenie poddano złącza wykonane za pomocą 5 kombinacji parametrów zgrzewania, różniących się czasem zgrzewania i natężeniem prądu elektrycznego. Analizowano nośności na ścinanie złączy, rozkład odkształceń plastycznych i sposób pękania. Pomiaru odkształceń plastycznych dokonano przy użyciu bezkontaktowego systemu analizy optycznej Aramis.

EN

Titanium and have been identified as one of the best engineering metals for application in many industrial fields such as aviation, automotive and civil engineering. This is because of properties of the material: low density and high mechanical strength. Titanium also is characterised by excellent corrosion resistance to many environments. In recent years, researchers have attached great importance to the application of titanium in resistance spot welding (RSW). In resistance spot welding, two metal sheets are placed between two copper electrodes. The purpose of the two electrodes is to supply current to the weld sheets. The production of RSW welds is finished via solidification. The paper presents a strength evaluation of welded specimens made of titanium grade 3 and grade 4 of 0.4 mm thickness. The lap joins were made by Resistance Spot Welding (RSW). The joints were welded by the single RSW weld. The optimal welding parameters were chosen. The joints welded by 5 variants of welding parameters, different of welding time and electric current. The shear load capacity, a plastic strains distribution and a method of cracking were assessed. The Plastic strains measurement was made using a non-contact optical deformation system Aramis.

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A study on numerical analysis of the resistance spot welding process

Zhigang H., Kim I. S., Son J. S., Kim H.-H., Seo J. H., Jang K. C., Lee D. K., Kuk J.M.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 14, nr 1-2

140--145

EN

Purpose: Over the last few years, there has been a growing interest in quantitative representation of heat transfer and fluid flow phenomena in weld pools in order to study relationships between the processing variables and the quality of the weldment produced and to use this information for the optimization and mobilization of the welding process. Design/methodology/approach: A 2D axisymmetric Finite Element Method (FEM) model has been developed to analyze the transient thermal behaviors of Resistance Spot Welding (RSW) process. In this model, the temperature dependent material properties, phase change and convectional boundary conditions were taken account for the improvement of the calculated accuracy, but the determination of the contact resistance at the surface is moderately simplified in order to reduce the calculating time through the analysis. Findings: The developed model has been employed the thermal history of the whole process (including cooling) and temperature distributions for any position in the weldment. Research limitations/implications: Future research in the field of RSW processing could focus on analysis of the stress and strain distributions as well as deformation in the weldment. Originality/value: It can be concluded that the maximum temperature was up to 1346°C, nearly the molten point of mild steel, and verified by the observation of the surface of the weldment after welding