In this paper, fatigue lives of tensile-shear multi-spot welded joints with four spot per specimen with different arrangements have been investigated. For this purpose, three types of joints with axial, transverse and almond-shaped have been selected. The prediction of fatigue life of spot welded joints has been carried out based on the available S-N curve of smooth specimens and the values of fatigue strength reduction factors. The experimental results and numerical predictions were compared and it was observed a good agreement between experimental and numerical ones. In addition, the Experimental Modal Analysis (EMA) was applied on the specimens before and after different fatigue loadings. Then percent of the identified natural frequencies decreasing was investigated and its correlation with crack initiation and total fatigue life of spot welded joints was studied.

Keywords: Fatigue Life, Modal Analysis, Resistance spot welding, Strain-life approach

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