Damage Mechanisms And Lifetime Prediction Of Stir Head For FSW

Friction stir welding(FSW)is a new type of metal solid-phase welding technology.Compared with the traditional fusion welding processes,it has many advantages,such as high efficiency,environmental protection,low energy consumption and so on.In addition,it can also be used to join high-strength aerospace aluminum alloys and other metallic alloys that are hard to weld by conventional fusion welding.It is known as "the most revolutionary joining process after laser welding".As an important component of the FSW equipment,stir head is closely related to the welding process.The sudden breakage or damage of the stir head will affect the welding quality,which seriously may lead to the welding work piece scrap.To prevent this phenomenon from happening,the traditional method is to get the working life of the stir head by experiment,and replace it before reaching the working life.This method is time and energy consuming and the cost of experiment is high.Therefore,studying the damage mechanism of the stir head,predict the service life of it have great significance to reduce production cost and improve production efficiency.In this paper,I use light-microscope and SEM to observe the fracture of the stir head which is used for welding aluminum alloy.And judge the failure reason is fatigue fracture.Analyze the stress of the stir head,establish the mathematical model of the force during the rolling stage and the stable welding stage.Use D graphics software Solidworks builds the three-dimensional model of welding work piece and the stir head.Use finite element software ANSYS Workbench simulate rolling stage and stable welding stage to obtain the von-Mises stress of this two stages.Based on the results of simulation,establish the load spectrum of the stir head.Predicted the fatigue curve of the stir head material by its static strength.Use nominal stress method and Miner linear cumulative damage theory for calculating the damage of welding each work piece,then get the working life of the stirring head.