Abstract
Although short-pitch resistance spot welding (RSW) significantly increases vehicle body strength, its application has been limited because of the associated shunting effect. In this study, a reference-based adaptive RSW process intended to minimize the shunting effect was proposed, and a related RSW system that controls welding current and power was developed to implement the adaptive method. The proposed RSW method compensates for the heat input loss caused by the shunting effect based on the estimated weld pitch and reference data obtained under suitable welding conditions. An exponential model was developed using a unique indicator (i.e., the ratio of the adaptive welding heat input to the reference welding heat input until the reference welding power curve peak) to estimate the weld pitch. A logistic growth model was next developed based on the relationship of the nugget diameter, heat input, and weld pitch to estimate the heat input compensation. A unique strategy using power control with a modified reference power curve was applied to supply the calculated heat input compensation. The experimental results intended to validate the proposed adaptive RSW process indicated that the proposed process effectively reduced the shunting effect and produced an improved nugget shape relative to the conventional RSW process.
Highlights
In response to enforceable vehicle fuel efficiency regulations, such as the Corporate AverageFuel Efficiency (CAFE) Standards intended to improve the fuel economy of light trucks and cars [1], automotive equipment manufacturers have developed and applied various lightweight technologies using high-strength steel (HSS) in their vehicle bodies [2,3,4]
The reference-based reference-based adaptive resistance spot welding (RSW) method proposed in this this study study included included both both current current and and power power control; control; the the related related RSW
The target weld pitch was was 10.0 mm, but inexact adjustments led to random pitch effects
Summary
Fuel Efficiency (CAFE) Standards intended to improve the fuel economy of light trucks and cars [1], automotive equipment manufacturers have developed and applied various lightweight technologies using high-strength steel (HSS) in their vehicle bodies [2,3,4]. In addition to meeting fuel efficiency standards, these lightweight vehicle body parts must meet various vehicle crashworthiness standards, such as the Small Overlap Frontal Crashworthiness Evaluation. This safety standard was introduced by the Insurance Institute for Highway Safety (IIHS) in 2012 and addresses one of the most serious crash scenarios [5,6]. The tensile shear strength (TSS) and fatigue strength of the spot welds show little and no increase, respectively, Metals 2018, 8, 775; doi:10.3390/met8100775 www.mdpi.com/journal/metals
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