Spatial Blending Functions for Improved Estimation of Contact Pressure Distribution at the Tool-Workpiece Interface

On-line measurement of contact pressure distribution (CPD) at the tool-workpiece interface during sheet metal stamping processes plays a critical role in tool wear and product quality monitoring and control. Realizing such measurement poses a significant challenge, due to the severe operating conditions at the contact interface. Since the number of sensors that can be integrated into a tooling structure is limited by concerns of structural integrity, a mathematical framework is needed for estimating the contact pressure distribution measured by sparse sensors. This paper investigates a new technique termed the Spatial Blending Functions (SBF), which provides an improved estimate of the contact pressure distribution by merging measurements from tooling-embedded sensors with simulation results from Finite Element modeling. The effectiveness of the SBF-based merging technique is demonstrated for the case of a panel stamping operation through Finite Element simulations and experiments performed on a stamping press with a tooling-integrated sensing system. Analysis of the results demonstrates that the SBF-based CPD estimation is more accurate than classic numeric surface interpolation methods, thus enhances contact pressure distribution estimation for stamping process monitoring.