E XPERIMENTAL AND NUMERICAL STUDY OF 6061-T6 AL- ALLOY FATIGUE LIFE USING FRICTION STIR WELDING

Abstract

Welded parts are often subjected to variable loads. Paper’s aim is to evaluate the fatiguecharacteristics of friction stir welding of AA6061-T6 alloy under variable loading andobserved the influence of heat treatment for friction stir welding joint on the fatigue stressanalysis. The microstructure of the welds alloy are studied before and after heat treatment.The friction stir welding was employed using milling machine with constant tool rotation(1000 rpm) and feed rate (20 mm/min). Artificial aging are made for aluminum friction stirwelded alloy using electrical furnace at temperature of 500ºC for 20 min. Quenching at190ºC for 4 hr. via water is followed the aging process. Fatigue test were done for specimens(base metal, friction stir welding alloys before and after heat treatment) to obtain the S-Ncurves for each case. Finite element via ANSYS software is used to analysis the FSW(temperature, Von-Mises stress, deformation in the welded zone and contact friction stressdistributions) and Fatigue test (fatigue life, fatigue damage, fatigue safety factor, biaxialityindication , equivalent alternating stress and stress intensity factors) where the generalthermo-elasto plastic relation produced under thermal and mechanical loads with isotropic,kinematic and mixed hardening rule in three dimensional problems is proposed. The resultsshown that the heat treatment for the friction stir welded alloy would be increased thefatigue strength of the welded plate that the number of cycles of base metal (AA6061-T6)was 1.2×106 and the number of cycle for welded joints without heat treatment was(0.9×106), where the number of cycles was 1×107 with heat treatment with quenching within4hr. also it can be concluded that, the fracture opening mode (mode I) is exist in the unheated welded alloy and disappeared with heating treatment