A study on the numerical analysis of thermomechanical behaviour in a stud-to-plate laser braze joint

摘要

A mechanical analysis of stud-to-plate laser brazing was performed using the finite element method, and the transient displacement and stress fields in brazing workpieces were calculated. The materials used were small-diameter studs of AISI type 304 stainless steel, thin plates of Al 5052 aluminium and 88Al-12Si braze alloy for the filler metal. The mechanical analysis took account of the thermal aspects of brazing and the transient temperature fields were calculated using a brazing heat transfer model. An incremental plasticity model was employed for thermal elastoplastic analysis, which considered the temperature-dependent mechanical properties and the isotropic hardening effect of the materials. The numerical result showed that high residual tensile stresses remained in the middle of the braze gap, approaching the yield point of type 304 stainless steel. The permanent deformation of workpieces after the brazing was completed was minimal and confined to the area adjacent to the joint. Stress peaks were found to exist along the joining interfaces, which were due to mismatches in thermal and mechanical properties among the materials involved.