Optimization of Process Parameters during Hydroforming of Tank Bottom using NSGA-III Algorithm

The hydroforming technology can realize overall forming of large storage tank’s bottom, but the quality is affected by many technological parameters. In view of wrinkling and cracking defects of integral storage tank’s bottom in hydroforming, a multi-objective optimization model is established for process parameters include pre-expansion pressure, hydraulic pressure, blank holder force and fillet radius of blank holder. Based on finite element simulation, the surrogate model between process parameters and quality criteria is established using Kriging technique. NSGA-III is used to determine optimal process parameters when storage tank’s bottom reaches targets include minimum wall thickness variations, minimum fracture trend, minimum flange wrinkle and minimum wrinkle trend. Compared with Particle swarm optimization (PSO) algorithm, NSGA-III algorithm is more suitable to solve this optimization problem. The validity of this method and accuracy of the results are verified by simulation experiments.