SPOT WELD FATIGUE DURABILITY PERFORMANCE EVALUATION THROUGH THE USE OF FEA

摘要

The sheet metal joining through spot welding is the most widely used process for automotive body building, where an average vehicle has around 5,000 spot welding points in its structure. In this sense, the spot welding project is critical to the final product performance and it must be done in a way that can assure both quality and durability of the vehicle, already taking into consideration the fact that the spot weld mechanical properties related to fatigue and rupture resistance are much lower when compared to other available welding techniques like MIG welding for example. These properties have a direct impact in the fatigue durability and crashworthiness properties of the vehicle, as a significant part of the structural resistance goes through these spot welds. With this scenario, the correct application of FEA techniques is very important to assure that the projected joints and spot weld disposition meet the product targets in terms of safety and durability. The objective of this work is to review the mechanical properties of the spot weld related to its fatigue strength and the FEA methods applied during the product development to assure that the durability performance target of the vehicle will be met. It has also been reviewed how the assembly process affects the FEA results in the cases of joint misalignment and indentation of the spot weld, where significant performance reduction can be expected. Another aspects, like crashworthiness performance of the spot welds, are not covered in this paper, however the correct application of the FEA techniques herein described are expected to improve these different aspects of the final product as well.