Optimum Design of the Friction Stir Welding Process on A6005 Extruded Alloy for Railway Vehicles to Improve Mechanical Properties

Won, Si-Tea; Kim, Weon-Kyong

Journal of KWJS 2009;27(5):81-87.
Published online November 16, 2009.

마찰 교반 용접된 철도 차량용 A6005 압출재의 기계적 성능 향상을 위한 최적 공법 설계

Optimum Design of the Friction Stir Welding Process on A6005 Extruded Alloy for Railway Vehicles to Improve Mechanical Properties

Si-Tea Won, Weon-Kyong Kim

Abstract

Recently, extruded aluminium-alloy panels have been used in the car bodies for the purpose of the light-weight of railway vehicles and FSW(Friction Stir Welding), which is superior to the arc weldings, has been applied in the railway vehicles. This paper presents the optimum design of the FSW process on A6005 extruded alloy for railway vehicles to improve its mechanical properties. Rotational speed, welding speed and tilting angle of the tool tip were chosen as design parameters. Three objective functions were determined; maximizing the tensile strength, minimizing the hardness and maximizing the difference between the normalized tensile strength and hardness. The tensile tests and the hardness tests for fifteen FSW experiments were carried out according to the central composite design table. Recursive model functions on three characteristic values, such as the tensile strength, the hardness difference(ΔHv) and the difference of normalized tensile strength and ΔHv, were estimated according to the classical response surface analysis methodology. The reliability of each recursive function was verified by F-test using the analysis of variance table. Sensitivity analysis on each characteristic value was done. Finally, the optimum values of three design parameters were found using Sequential Quadratic Programming algorithm.

Key Words: FSW, Sensitivity analysis, Tensile strength, Hardness, Normalized tensile strength, Normalized ΔHv, Response surface analysis methodology, Optimization