Numerical simulation on residual distortion of dissimilar metals during friction stir welding based on subregion characterization
To study the correlation mechanism between the changes of yield strengths of weld materials and welding residual distortion,the calculation method of residual distortion of dissimilar metals during friction stir welding based on machanical property subregion charac-terization was proposed.The influence of the rotation direction of the stirring tool on the mechanical property curves of the stirring zone in friction stir welding was studied through friction stir welding experiments.The yield strength of the stirring zone material was defined based on the experimentally measured material constitutive relationship.Different yield strengths were characterized by subregions.The sequen-tial thermo-mechanical coupled model of friction stir welding was established.The influence of yield strength changes in the stirring zone on the residual distortion of dissimilar metals during friction stir welding was studied.The results show that when the advancing side mate-rial is 2024-T3 and the retreating side material is 6061-T6,the yield strength of the stirring zone is 171 MPa and the tensile strength is 194 MPa.When the materials at advancing and retreating sides are exchanged,the yield strength of the stirring zone is 166 MPa and the tensile strength is 186 MPa.The reason for the difference in yield strength and tensile strength caused by the exchange of materials on the advancing and retreating sides is the different flow behaviors at advancing and retreating sides.According to the measured mechanical property curves,the sequential thermo-mechanical coupled model for friction stir welding of dissimilar metals was established.When the advancing side material is 2024-T3 and the retreating side material is 6061-T6,the maximum residual distortion of the friction stir welding component is 1.2 mm.When the advancing side material is 6061-T6 and the retreating side material is 2024-T3,the maximum residual distortion of the friction stir welding component is 1.3 mm.With the increase of yield strength of the stirring zone material,the bending stiffness of the stirring zone increases,leading to the decrease of residual distortion.
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