Advances in Alternative Spot-Joining Technologies for Difficult-to-Weld Materials

The growing demand for lightweight, multi-material structures has accelerated the development of joining technologies capable of uniting dissimilar metals, polymers, and composites. Conventional resistance spot welding (RSW) remains prevalent in automotive body construction but faces inherent limitations when applied to high-strength aluminum, magnesium, and polymer-matrix materials. These challenges—arising from electrical, thermal, and metallurgical incompatibilities—have driven the emergence of alternative spot-joining technologies that employ frictional, mechanical, or hybrid mechanisms to achieve localized bonding without melting.
This paper provides a comprehensive review of these methods, categorized as rivet-less, tubular-rivet, and solid-rivet joining systems. The discussion covers mechanisms of heat generation and material flow, representative joint microstructures, and mechanical performance across various material combinations. Recent advances in numerical and data-driven modeling are examined, including thermo-mechanical finite-element analysis, machine-learning-assisted surrogate modeling, crashworthiness simulation, and corrosion–fatigue prediction, all of which contribute to the realization of digital-twin frameworks for joining process design.
The paper concludes with an outlook on AI-enabled process monitoring, adaptive control, and sustainability-oriented design, emphasizing the transition from empirically tuned operations to intelligent, self-optimizing joining systems that support next-generation manufacturing.