Novel hydromechanical reverse drawing method for thin-walled aluminum alloy sheet forming

Thin-walled aluminum alloy sheet metal parts are important structural parts of aircraft. This study proposed a reverse drawing method for the fabrication of aluminum alloy sheet parts characterized by reverse drawing. Two modes of forming were discussed herein: (a) a reverse drawing and hydro-bulging method that employs hydro-bulging to complete the final integral forming after drawing and (b) a two-stage hydromechanical reverse drawing (HMRD) process including deep drawing assisted by fluid counter force. Both the simulated and experimental results showed that the blank holder force and pressure loading path significantly affect the formability of the final part. Wrinkles occurring at the unsupported region with a curved surface area can be alleviated by the reduction of the blank holder force and an increase in hydraulic pressure. With HMRD, wrinkles and cracks were eliminated, and the maximum thinning rate was reduced to 22.5% for the aluminum alloy 2A12 part. The findings herein validated the feasible applications of hydromechanical reverse drawing for the manufacture of sheet metal with no defects through the optimization of the process parameters.

Automated summary

This study proposed a reverse drawing method for the fabrication of aluminum alloy sheet parts and discussed two modes of forming. The results showed that the blank holder force and pressure loading path significantly affect the formability of the final part. Wrinkles in the curved surface area can be alleviated by reducing the blank holder force and increasing hydraulic pressure, and wrinkles and cracks can be eliminated by using the HMRD process.