Design and development of a micro-LDH apparatus to determine formability of sheet metal under hot stamping conditions using Gleeble

Abstract

In the last few years, demand for hot stamped components has increased in the automotive industry. Determination of formability under hot stamping is challenging due to elevated temperature, fast cooling, and high punch velocity. Although there was various strive for formability determination, but there were limitations with experiments like non-uniform heating of specimen, non-uniform strain, and temperature distribution. Therefore, in this work, an experimental apparatus was developed to determine formability at room temperature, high temperature, hot stamping conditions, and any complex process cycle involving heating and cooling. New specimen was designed to produce different strain paths, uniform, and homogenous temperature distribution with the help of FEM software using thermomechanical and thermoelectrical simulation. A micro hemispherical dome-based experimental apparatus was designed using Solidworks. The designed apparatus was used in conjunction with the thermo-mechanical simulator (Gleeble-3800). Thermomechanical analysis was done in PAM STAMP software to optimize specimen size and shape to get uniform strain distribution and different strain paths. A thermoelectric FEM model was developed using Abaqus 6.14 to optimize the temperature distribution in the specimen. The developed model enables choosing the appropriate polarity of the electrical cable connection to achieve uniform temperature distribution in the specimen. Strain path and temperature profiles for experiment and simulation were compared. Further, a forming limit curve was developed using the designed apparatus to verify the feasibility of the apparatus. For feasibility test of apparatus, hot stamping process was selected. This new design apparatus can be used for a range of temperatures up to 1000 °C, hot stamping conditions, and for different materials (aluminum, magnesium alloys, different grade of steel, etc.). It concludes that the connection of different polarities of electrical cable was critical for homogenous and uniform temperature distribution in specimens.