Investigation on changing loading path in sheet metal forming by applying a property-adjustable flexible-die

In sheet metal forming operations, the loading path is a significant process parameter, which greatly influences material flow and part quality. In this paper, an innovative method was proposed to change the loading path by using a property-adjustable flexible-die (MR fluid) in sheet forming process. Experimental and numerical simulations on free bulging process of Al 1060-O sheet using a MR fluid under two different magnetic field changing types were carried out. Results showed that the loading curves were changed noticeably by varying the magnetic flux density in the working area during the bulging test. The differences of configuration, velocity, stress distribution and thickness strain distribution of forming parts indicate that the loading path change has a great effect on the deformation behavior. It provides a new method to change the loading path in near real-time during the forming process, which brings potential application for intelligent control of sheet metal forming.