Micro- and multiscale material properties must be considered when manufacturing miniature devices, especially when considering utilizing multiscale sheet metal hydroforming processes. One of the critical considerations during the design process is the burst pressure for the sheet metal which is a limiting factor for potential hydroforming operations. In order to simplify determining tearing or rupture conditions, it is sometimes desired to use analytical methods for estimating material properties, including burst pressures, which occur shortly after material instability. Many researchers have developed approximate methods for predicting deformation during open die hydroforming based upon analytical approaches for biaxial conditions for circular and elliptical dies. Additionally, extracting material properties of sheet metal under biaxial conditions such as bulge hydroforming more closely matches forming conditions that the sheet metal will undergo for actual parts. The objective of the current research was to evaluate the analytically developed models’ ability to predict burst conditions and compare those burst results to those obtained from finite element models and experimentation. Stainless steel (annealed 0.2-mm thick AISI 304) was hydroformed in a circular open die with diameter of 11mm. Elliptical dies were also evaluated that had minor diameters of 11mm and aspect ratios down to 0.5. It was found that using the analytical method developed specifically for circular dies was a good predictor for the burst pressure while the more general analytical method for elliptical dies did not agree with either results from finite element analysis or experimental results.

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