Title:

Investigation of Macro-Structured Tooling Effect on Formability Enhancement and Force Reduction in Deep Drawing Process

In deep drawing, formability is limited by wrinkling and tearing, and conventional draw beads control material flow at the cost of heavy lubrication and high frictional resistance. Macro-structured tooling with periodic wave features offers an alternative, reportedly reducing blank-holder force by over 50%, lowering forming energy by ~17%, and potentially eliminating lubrication. As sheet metal flows over the wave peaks, it undergoes repeated bending and unbending under superimposed tension, a deformation mode mechanistically identical to Cyclic Bending under Tension (CBT). This work establishes CBT as a fundamental characterization method for both conventional and macro-structured forming processes. Using a CBT setup with varying bending depth ratios, force-displacement response, forming limits, and texture evolution were evaluated. Compared to simple tension, CBT yielded up to five times greater elongation to fracture and reduced forming force through bending-induced stress superposition. Marciniak testing with full-field strain measurement on CBT-processed specimens demonstrated extended forming limits, while pole figure analysis revealed pronounced {011} fiber development along the stretching direction. These results position CBT as a critical tool for optimizing next-generation stamping processes.

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