Tool Wear And Contact Pressure Measurement In Sheet Metal Forming Process

Investigation of the tool wear controlling and evolution characteristics of contact pressure during bending and drawing process of high strength steel was performed. Plastic forming theory was applied to analyze the magnitude of the contact pressure at the die radius during the cup drawing process. The results gained from the formulas of the contact pressure coincided with that of the finite element results. Finite element method was utilized to simulate the channel forming process of DP780. The hardening model of sheet metal, contact pressure dependent frictional coefficient of the blank-die interface and strain rate-dependent behavior of the sheet metal were investigated. The flowing conclusions can be drawn from the simulation results:the sheet using combined hardening rule has a higher value of tool wear than that using the isotropic hardening rule; constant friction coefficient and strain rate-independence model has a lower value of the predicted tool wear.Optimization of die radius contour lines aimed to find a profile curve which achieves the minimum wear depth and the most uniform distribution of wear was conducted. The simulation model assisted with user subroutine was used to calculate the optimization function of all the contour lines of the die radii. Moreover, artificial neural network was employed to establish the relationships between die contour lines and optimization function values. The optimization method was sequence quadratic programming by which the contour lines satisfied the aim was obtained. Finally, the piezoelectric cable was utilized to capture and measure the peak value of contact pressure at the entrance region of the die radius. The electro-mechanical coupling finite element simulation was conducted to validate the practicability of this method. The calibration experiment was then carried out to obtain the piezoelectric coefficient. A half open die radius in which the cable was half embedded had been designed. The peak of contact pressure was captured and the peak distribution of the contact pressure was provided.