Preform design for formability enhancement of tube hydroforming process using deformation history

Preform design in tube hydroforming implies the design of an intermediate shape between initial tube and the final product enabling to be fabricated without defects and excessive loss of material. A carefully selected preform can contribute significantly to reduce production cost and improve formability, since thinned sections may not be able to endure internal pressure during expansion whereas excessive thickening may lead to wrinkles. Generally, preform design in hydroforming was mainly carried out through the trial-and-error approach. Even though a series of numerical simulations for several predetermined preformed shapes were conducted, optimum configuration could not be obtained and could not be suggested the general procedure for preform design as well. In this work, a simple numerical approach to the preform design for formability enhancement was introduced based on the deformation history during forward hydroforming simulation. The proposed approach was implemented to a hydroforming process of an automobile subframe component in order to be satisfied the required specification after hydroforming, and the conceptual application has been proved to be successful on its effectiveness and feasibility. Therefore, it is shown that preform design approach proposed in this study will provide one of feasible methods to satisfy the increasing practical demands for improvement of the formability in hydroforming processes.