hydroforming of anisotropic aluminum tubes: part i experiments

hydroforming of aluminum tubes, despite its appeal in weight-sensitive applications, presents challenges such as the reduced ductility of al in comparison to steel and its more complex constitutive behavior. this two-part series of papers details a combined experimental and analytical study of the process and its limits. part i presents a custom laboratory-scale facility used to conduct a series of hydroforming experiments on relatively long al-6260-t4 tubes. the initially circular tubes are inflated against a square die with rounded corners while simultaneously they are axially compressed in order to delay wall thinning and burst. a 2d numerical model was used to optimize the loading histories considered. despite careful design of the process, burst proved to be a limiting factor as friction prevented uniform material feeding to the expected levels. furthermore, prediction of burst was found to require the calibration and implementation of non-quadratic, anisotropic yield functions in the constitutive modeling and the use of numerical models that include all 3d effects of the setup. these models and their performance in predicting all aspects of the experimental results are discussed in part ii.