Robust design optimization of HDPE friction stir welding process using the static RDPP-SF and Taguchi-grey methods: A comparative study

Abstract

The paper aims to analyze and optimize the FSWing process of plates in a butt configuration. The ultimate objective is to desensitize the process to both endogenous and exogenous noises, which are lacing the manufacturing process.. To this end, the Robust Design for Products and Processes using the stochastic frontier (RDPP-SF) and the Taguchi-Grey methods are employed, and settings of the process parameters, which yield the best mechanical performances, are sought. The process parameters are the pin rotation speed (x₁), feed rate (x₂), and plunged surface (x₃), whereas the process responses are the longitudinal stress (σ_L), transverse stress (σ_T), longitudinal strain (ε_L), and transverse strain (ε_T) that occur in the FSWed seams. Three replications of an FCCD design are conducted and then statistically analyzed. For the RDPP-SF method, the optimal mechanical properties are σ_L = 22.197 MPa, σ_T = 22.607 MPa, ε_L = 18.33 %, and ε_T = 15.83 % and they occur when setting the rotation speed (x₁) at 1700 rpm, the feed rate (x₂) at 29 mm/min, and the plunged surface (x₃) at 478 mm². The optimal values with regard to the Taguchi-Grey method are achieved at, σ_L = 23.733 MPa, σ_T = 23.886 MPa, ε_L = 17.76 %, and ε_T = 16.91 % while setting the rotation speed (x₁) at 1280 rpm, the feed rate (x₂) at 29 mm/min, and the plunged surface (x₃) at 478 mm². The discrepancy between the RDPP-SF and the Taguchi-Grey method is partly due to the variance decomposition models, which are employed.