Controlled strain path forming process with space variant blank holder force using RSM method

In this paper, a strain path controlled forming process is reported through adjusting the blank holder force located in various flange areas to achieve a fracture free product. Due to the wide application and the high efficiency of the Finite Element Method, it is the means used instead of experiment to carry out the controlled forming process. Deep drawing processes with two materials, SPCC and Al 5754, were simulated with yield criteria Hill 48 and Hill 90, respectively. The empirical equation, built through Response Surface Method, was developed based on the Finite Element Method (FEM) simulation results. The equation explores the relationship between the principal strain of fracture risk elements and the working parameters, especially the blank holder force located in various flange areas. The empirical equations were developed based on a set of numerical simulation results within two elements which have the high fracture risk. Three dimensional principal strain surfaces of one element were drawn which displayed the obvious trend varied with the space variant blank holder force. The model adequacy was checked and confirmed using ANOVA method. However, four extra sets of numerical simulation were carried out to compare with the value predicted using Response Surface Method (RSM). The good consistency confirms the effectiveness of this empirical equation within the plasticity field. With the assistance of the empirical model, it is feasible to acquire a fracture free product through regulating a suitable blank holder force profile. The space variant blank holder system could be widely used to form a product with complicated shape, especially body panels in the automotive field.