A Universal Elastoplastic Equivalent Method for Sandwich Panels and Its Application in Plastic Forming

Based on Hill'48 yield criterion, a simple and universal elastoplastic equivalent method for sandwich panels was proposed. In this method, the core of sandwich panel was equivalent to an orthotropic homogeneous panel, and the elastoplastic parameters of equivalent sandwich model were quickly obtained by uniaxial tensile and pure shear numerical simulations of the mesoscopic sandwich model utilizing user-defined material subroutine (UMAT). The equivalent elastoplastic parameters of brazed aluminum honeycomb panels (BAHPs) with core heights of 9 mm (BAHP-H9) and 12 mm (BAHP-H12) were obtained, which were proved to be effective by comparison with analytical solutions and analysis of numerical simulation results. Then, the effectiveness of elastoplastic equivalent method was further demonstrated by comparing the numerical simulation results of multi-point forming (MPF) for the mesoscopic and equivalent finite element (FE) model of BAHPs. Finally, MPF experiments of cylindrical BAHPs under different target forming radii were carried out. The results showed that the elastoplastic equivalent method could be effectively applied to the plastic forming of sandwich panels.