Inverse Analysis in Hydroforming of a Refrigerator Door Handle Using MOGA

Abstract

An inverse problem of load path design in tube hydroforming of a refrigerator door handle is 
presented. The motivation is to inversely analyze the load path for tube hydroforming and 
verify the applicability of developed algorithms. Several parameters are given as inputs: the 
material properties of the pre-bent tube, the geometry of the tube and the die. The study 
also investigates the influence of the coefficient of friction (COF) at two levels: with COP 
of 0.1 and 0.05. The process parameters with regard to pressure and end feeding are to be 
determined. An optimization strategy using MOGA was implemented to solve the inverse 
problem. In order to obtain a quality part without failure, six objectives were calculated to 
evaluate the forming severity and the final product geometry, namely, fracture/necking, 
wrinkling, severe thinning, die filling, and the maximum thinning ratio of tube thickness. The 
MOGA was coupled with finite element analysis (PEA) and used to optimize the load path. 
To reduce the calculation cost, a surrogate Kriging model was established to replace the PEA, 
and was updated every five generations. A Pareto optimal solution set was generated after 20 
steps and the optimal load path was determined with a minimum thinning ratio. The results were 
validated by both the FEA simulation results and the comparison of the optimal load path with 
the actual load paths. It was noted that the thinning ratio was less than 25% for the lower 
coefficient of friction (0.05) and the maximum stress was far below the forming stress limit. 
Meanwhile, the tube fully filled the die cavity and no failure occurred.