Failure prediction of hydroforming aluminum tubular blanks

Abstract

Aiming for weight and product cost reduction as well as structure enhancement, different industries have been embarking on the development of new manufacturing processes and materials to produce different lightweight components and structures. The applications of lightweight aluminum tubular components / structures have been under development for many years. The industry's increasing requirements for the utilization of aluminum tubes in hydroforming processes indicate the industry's demands for lightweight metals, low energy consumption and effective methods for reducing the whole weight of components. However, the production of extremely thin and economical aluminum alloy tubes is still a challenging task. The formability of aluminum tubes in the hydroforming process is an important factor and was thus the focus of this study to offer an effective evaluation method for predicting the failure of alloy tubes. The objective of this study was to develop a failure criterion to predict the failure of hydroforming of aluminum tubular blanks. This was achieved by developing a testing method for the tube formability and a new damage-based failure criterion for the tubular component under investigation, as well as the fracture behavior of aluminum tubular blanks during the hydroforming process. The aluminum seam welded alloy tubes AA6063 were selected as the specimens in this study. An experimental platform for the hydroforming process was utilized in the study to obtain both material properties and damage parameters. A new analytic method in deriving damage rule has been proposed as a result of the study. Together with the experiment, a damage-coupled shear criterion was developed for the failure prediction of aluminum tubes in the hydroforming process. The criterion was computed using FORTRAN codes and compared to the experimental results and two other results obtained from published articles. The damage-coupled constitutive and failure models were implemented in a finite element analysis and then validated by the experimental results in order to establish a reliable failure prediction method for hydroforming aluminum tubular blanks. With the aid of the predictive capability of a damage-based material and failure models coded in a finite element package, new insights into the material failure behaviors in the hydroforming operation have been realized. The establishment of the predictive method will enable design and process engineers to produce high-quality tubular structures/components at a considerably reduced cost and weight.