Residual stress profiles in coated riveted joints of dissimilar materials using SPR joining technique

The United Kingdom has set a formidable net-zero target of 100% emission reduction by 2050, emphasising the urgent need for progress in sustainability efforts. Given the significant role of the automotive industry in CO2 emissions, there is a growing demand for lightweight multi-material structures to mitigate environmental impact. Carbon fibre reinforced polymer (CFRP) and Aluminium (Al) have emerged as pivotal materials due to their superior strength-to-weight ratio, particularly in the context of vehicle electrification. However, understanding and mitigating joint failure resulting from residual stresses in the Self-piercing riveting (SPR) process remains a critical area of investigation. Prior studies have successfully quantified residual stresses in SPR joints, primarily focusing on similar metallic materials. This current research extends the inquiry to encompass both dissimilar materials i.e. CFRP-Al with carbon steel rivet joint, with a particular emphasis on the resistance encountered during rivet insertion, potentially leading to stress-induced failures. Employing various coated rivets (carbon and Aluminium-based) with distinctive characteristics, this study aims to unravel the intricate interplay between surface properties, coating hardness, and residual stress formation during SPR joining, ultimately enhancing our comprehension of these critical structural elements.

英国已确立极具挑战性的2050年实现100%减排的净零排放目标，凸显了可持续发展进程提速的迫切性。鉴于汽车工业在二氧化碳排放中占据重要地位，市场对轻量化多材料结构的需求日益增长，以降低其环境影响。碳纤维增强复合材料（Carbon Fibre Reinforced Polymer, CFRP）与铝（Aluminium, Al）凭借优异的比强度，已成为车辆电动化领域的关键材料。然而，如何理解并缓解自冲铆接（Self-piercing Riveting, SPR）过程中由残余应力引发的接头失效问题，仍是亟待深入研究的核心领域。此前的研究已成功量化了SPR接头中的残余应力，但主要聚焦于同类金属材料。本研究将研究范围拓展至异种材料接头，即采用碳钢铆钉的CFRP-铝接头，并重点关注铆钉插入过程中遇到的阻力——该阻力可能引发应力诱导失效。本研究使用多种具有独特性能的碳基与铝基涂层铆钉，旨在揭示表面特性、涂层硬度与SPR连接过程中残余应力形成之间的复杂相互作用，最终加深对这类关键结构元件的理解。