Aluminum Friction Stir Welding Head Fatigue Crack Growth Rate Pilot Study

Friction stir welding(FSW)is a solid-state connection,because of its unique characteristics of the welding and advantages of this new link since the advent of technology since the welding industry by the extensive attention.In aerospace, shipbuilding,automobiles and other fields,especially high-strength aluminum alloy in connection with broad prospects.FSW at home and abroad from the present situation,although foreign aircraft parts has been in use on aluminum parts of the friction stir welding technology,but some of the joint application of basic research work is not perfect,especially the fatigue. Fatigue damage is the main reason for failure mechanical parts.According to statistics, in the mechanical parts failure in about 80 percent or more of fatigue damage. Aluminum alloy used for air friction stir welding the first to study the fatigue of the significance of self-evident.Can FSW technology in the aviation industry in China will depend mainly on friction stir welding the first performance meets the requirements of aircraft and fatigue properties must be studied and verified one of the important properties.FSW joint fatigue behavior of aerospace structures,anti-fatigue fracture of FSW is to inform the members of the use of one of the most important indicator.Therefore,this paper,aluminum friction stir welding head fatigue crack growth were studied,and achieved certain results.1.In view of the commonly used four aircraft aluminum alloy (2024,6082,7050,7075)the different specifications,the use of existing conditions, determined to meet requirements of joint use of friction stir welding process parameters.And through the friction stir welding the first organizational analysis and testing,by technical parameters.To seek technical parameters and fatigue properties of relations,in order to find the best alloy corresponding to the fatigue properties of welding norms.2.Aluminum alloy used for aviation 7075 - T651,7050-7451 friction stir welding head of the base metal,welding the nuclear area and heat-affected zone of the fatigue crack growth rate(da/dN)were studied.Fatigue crack growth tests using CT sample, 810 Material Test System on the test machine.Increased use of polynomial obtained fatigue crack growth rate(da/dN)and(ΔK),respectively,and will base metal, welding the nuclear area and heat-affected zone of the same set of samples(da/dN) and(ΔK)data points together for the overall return Analysis.Test formula has been to Paris to express the aluminum alloy 7075 - T651 base metal,welding the nuclear area,heat-affected zone(da/dN)and(ΔK)the relationship.The results show that the heat affected zone fatigue crack growth rate higher than the base metal and welding the nuclear area,the alloy is the first of friction stir welding the weakest region.3.For the aluminum alloy 7075 - T651,7050-T7451 friction stir welding the first heat-affected zone of the fatigue crack propagation pilot study was to understand the fatigue crack in the heat affected zone in the joint expansion of the mechanism,and its influence factors.