Finite element investigation of orientation-dependent mechanical properties in Reuleaux triangle clinch joints

Abstract Clinch joining is widely used in sheet metal assemblies, and joint geometry strongly influences mechanical performance. While most studies focus on circular or rotationally symmetric joint geometries, the influence of non-rotationally symmetric joint orientation relative to the loading direction has received limited attention. The present study addresses this gap through a systematic finite element investigation in which three distinct orientations of a Reuleaux triangle clinch joint are analyzed under quasi-static lap-shear loading, with all other model parameters held constant. The study is purely numerical; no experimental validation or damage model is included. Force–displacement responses, initial stiffness, and load at 1 mm displacement are evaluated alongside local stress and strain distributions. The results show that joint orientation has a negligible effect on elastic stiffness but a significant influence on load-bearing capacity, with the arc-loaded configuration outperforming the vertex-loaded configuration by approximately 10%. The origin of this difference is traced to orientation-dependent stress concentration at the joint neck and the asymmetry in neck thickness between orientations.