Abstract
The paper presents investigation on the ideal spot weld numerical model. The weld discussed in the paper was made by the resistance spot welding of two overlapping steel sheets. The ideal weld contained three parts, i.e. two welded steel sheets and an intermediate component (connector) made of the same material. The connector was placed between the sheets, assembled mechanically and fixed. A numerical model of the ideal weld enables the elimination of all welding imperfections, including, among other things, an indent left by the electrode as well as stresses and deformations of materials present in the actual welded joint. The ideal weld was intentionally not subjected to the thermal cycle. As a result, the heat-affected zone and the molten nugget were eliminated from the model (welding area). Consequently, the entire tested (analysed) weld specimen only had the properties of the base material. The analysis presented in the paper is based on 3D FEM numerical modelling and experimental validation. The numerical model of the ideal weld (nugget surface) was investigated in relation to various shapes of the nugget (e.g. circular, square and rectangular) as well as in relation to different dimensions. The research also involved the performance of a comparative analysis including various welding conditions. The analysis was carried out to determine the highest possible value of shear force generated during a static tensile test. The results of the numerical tests were compared with the results of selected laboratory tests.
Highlights
Results of scientific and engineering investigations reported in publications, those related to resistance welding, are usually focused on modifications of technological processes aimed to improve both the process and the quality of finished products
The research involved the examination of the effect of the weld nugget shape, the weld area and welding technology parameters on weld strength in the static tensile test based on numerical analysis and laboratory tests
Maximum differences between the FEM calculation results and the experimental test results of approximately 12% and 15% related to the maximum shear force and shear strength, respectively. & Adopting the highest value of the shear strength in the static tensile test as the primary criterion, the most favourable variants were M8 and M6 (2 circular weld nuggets, φ = 4.24–6.0 mm)
Summary
Results of scientific and engineering investigations reported in publications, those related to resistance welding, are usually focused on modifications of technological processes aimed to improve both the process and the quality of finished products. In terms of resistance welding, goals are usually joint-related improvements achieved through the reduction of welding imperfections, increased process repeatability and/or the higher strength of welded joints [1,2,3]. Reported investigations related to the strength of joints usually. Related recommendations suggest avoiding the use of welds affected by tension or torsion [2]. For this reason, the primary analytical criterion adopted in this paper was the shear strength of the weld. The quality-related analysis presented in this article did not include a depth to which electrodes penetrated the material subjected to welding (‘indent’)
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