ANALYTICAL AND NUMERICAL THERMAL ANALYSIS ON FRICTION STIR WELDING USING POLYGONAL TOOL PIN

Abstract

Frictional heat generation in the tool/matrix interface followed by the stirring of material along the weld line causes plasticized solid state joining in friction stir welding. In this paper, the existing torque based thermo-mechanical model for the tools with cylindrical pins is remodified for the polygonal tool pin profile by introducing novel multiplication factors with respect to the number of sides in the tool pin geometry. The variation in the effective heat supply with respect to the chosen pin geometry was analyzed. A comparative analysis of the proposed analytical model with the existing model was also carried out to understand the accuracy of the proposed model.  Furthermore, a transient thermal numerical modelling was carried out in the view of understanding the change in process peak temperature in the stir zone and change in temperature gradient along the heat affected zone with respect to the change in pin geometry for the opted set of process input parameters. An analytically estimated heat-input-based numerical model was adopted in the present study. It was observed that the process peak temperature was directly proportional to the number of sides in the tool pin.

ABSTRAK: Penjanaan haba geseran antara muka pada alat/matrik diikuti dengan pengacauan material sepanjang garis kimpalan menyebabkan keadaan plastik pepejal melekat bersama geseran kimpalan pengacau. Kajian ini berkaitan tork sedia ada berdasarkan model mekanikal-terma bagi alat pin silinder yang terubah suai bagi profil pin alat poligon dengan memperkenalkan faktor gandaan berdasarkan bilangan sisi geometri alat pin. Perubahan pada bekalan haba efektif berdasarkan geometri pin pilihan telah dikaji. Analisis bandingan pada model analitik yang dicadang bersama model sedia ada, telah dilakukan bagi memahami ketepatan model cadangan. Tambahan, model transien numerikal terma telah dibuat bagi memahami proses perubahan suhu puncak ketika zon pengacauan dan perubahan gradien suhu sepanjang zon terkena haba perubahan geometri pin pada set proses parameter input terpilih. Kajian ini mengaplikasi model numerik berdasarkan input anggaran haba secara analitik. Dapatan kajian menunjukkan suhu puncak proses adalah berkadar langsung dengan bilangan sisi pin alat.