Creep Age Forming of Aluminum 7075 Tailor-Machined Blanks: Statistical Modeling, Sensitivity Analysis and Multi-objective Optimization

Abstract

In this paper, creep age forming of aluminum 7075 tailor-machined blanks is experimentally studied. As there are two different thicknesses in a single tailor-machined blank, forming properties differ, e.g., spring-back in two sections with different thicknesses. Hence, creep age forming of this kind of blank is more difficult than monolithic plates. In the present work, the effect of two main creep forming process parameters, namely time and temperature, is investigated on spring-back of both thin and thick sections of a tailor-machined blank. First, a model was initiated and then a multi-objective optimization using response surface methodology was proposed considering time and temperature as input and spring-back as output parameters. Finally, a second-order linear regression for spring-back of thin and thick sections was introduced. Evaluation of the developed model and the role of considered parameters on spring-back were investigated using Sobol sensitivity analysis. The results showed that within the range of considered parameters with an increase in both time and temperature, spring-back for both thin and thick sections decreases. Based on the multi-objective optimization of the present work, the best time and temperature for creep age forming in a 7075 tailor-machined blank with minimum spring-back in both thin and thick sections are 19.6 h and 232 °C, respectively.