Numerical Simulation And Experimental Analysis Of Friction Stir Welding To Investigate Mechanism Of Defect Formation And Its Influence On Weld Quality

Abstract

Friction stir welding (FSW) is a solid-state joining process and is effective in welding newlinealuminum alloys. Study on material flow mechanism and defect formation is important as it newlineinfluences the quality of the weld, mechanical properties and microstructural features. newlineExperimental analysis of FSW is a time-consuming and tedious task as it requires a lot of post newlineweld analysis to acquire weld properties. The numerical technique is an efficient method as it newlineovercomes these issues with material flow observations and in-depth defect analysis. In the newlinecurrent research work, a three-dimensional thermo-mechanical model based on the coupled newlineEulerian Lagrangian method is developed to simulate FSW under different conditions. The newlinedeveloped model for the FSW AA6061 sheet is validated with the defect, forces, and spindle newlinetorque. Also, there is a lack of numerical modeling that shows different types of defects. newlineDifferent types of defects, i.e. tunnel, void, cavity, and root defects that are encountered from newlinethe numerical results for different process combinations. A parametric window is established newlinebased on the defective and non-defective process ranges. A 2o tilted tool mostly resulted in a newlinedefect-free weld condition due to proper forging load and improved weld temperature. The newlinemodel is further extended for FSW of an AA2024 aerospace grade alloy using a square pin newlinetool. Literature suggests that square pin produces better weld than cylindrical pin due to newlinepulsating effect. The average axial force and defects are validated with in-house experimental newlineresults. There is a lack of research work that has calculated the weld efficiency using numerical newlinetechniques by using the model s output responses. A novel concept of defect volume is newlinecalculated using the Eulerian volume fraction within the weld domain. The developed model newlineis used with an eccentric square pin tool along with an experimental technique. The novelty newlinelies in employing numerical modeling of eccentric pins as most of the work done is newlineexperimental. Also, an enhanced rotational