Abstract
Self-piercing riveting (SPR) is one of the mechanical joining processes, and its application to Al/Fe dissimilar materials combination, which is hard to weld, is expanding in the automotive industry. The main process parameters in SPR are types of rivet and die, setting force, and rivet setting speed. Previously, the relationship between the main process parameters and output parameters such as cross-sectional characteristics and joint strength has been studied to optimize the SPR process. In practical applications, there are unexpected and abnormal process conditions such as poor fit-up, angular misalignment, edge offset distance, and inaccurate setting and pre-clamping forces, and their effects on the joining quality have not been discussed. In this study, parametric investigation was performed using an experimental design on SPR joints for 1 mm-thick high strength steel (590 DP) and 2 mm-thick Al alloy (Al5052-H32). The main effect of each level of the abnormal process parameters on the output parameters was statistically investigated, and the analysis of variance was performed for each abnormal process parameter. In the range of abnormal process conditions applied, the set force was the most significant factor affecting the output parameters, and the effect of pre-clamping force on the output parameters was the least significant.
Highlights
In order to improve fuel efficiency and crashworthiness in the automotive industry, the application of various materials rather than the conventional mild steel has been expanding [1]
Five abnormal process conditions were considered in this study; two parameters were related to the forces, and three parameters were related to the specimen setting
The effect of abnormal process conditions during self-piercing riveting (SPR) on four output parameters such as the cross-sectional characteristics and the tensile shear strength of the SPR joint were investigated by using parametric investigation
Summary
In order to improve fuel efficiency and crashworthiness in the automotive industry, the application of various materials rather than the conventional mild steel has been expanding [1]. Increased application of non-ferrous metals and dissimilar material combinations requires non-conventional joining processes instead of resistance spot welding (RSW) and gas metal arc welding (GMAW), which are the main joining processes in car body manufacturing. The rivet, die, and setting force are considered as the main process parameters for given material combinations. From extensive experiences of RSW for sheet metal, it is known that there are diverse abnormal process conditions that are not usually considered as process control parameters but affect the quality of welding. Five factors such as poor fit-up, angular misalignment, edge offset distance, and inexact setting and pre-clamping forces are selected as abnormal process conditions in the SPR process. An experimental design was implemented to analyze the effect of abnormal process conditions on the cross-sectional characteristics and tensile shear strength of the SPR joint
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