As elucidated by StampingSimulation.com in their article “What is Springback in Forming Simulations and How to Identify It,” springback is a phenomenon that emerges during the metal forming process. Once a sheet of metal is plastically deformed by a forming tool to attain a desired shape, the sheet’s final form can alter once the forming tool is withdrawn. This alteration results from the release of elastic stresses, causing the sheet to revert to a new shape as the forming force diminishes—a process that equalizes elastic stresses and strains.
The Culprits Behind Springback While plastic stresses and strains purposefully induce most of the sheet’s deformation, residual elastic stresses endeavor to revert to their original state. This interplay between plastic and elastic behaviors distorts the sheet metal shape. The severity of springback is often heightened in materials with elevated Yield Strength (YS) or comparable Yield Strength and Tensile Strength (TS) values. Geometric intricacies, forming processes, and other variables contribute to the problem’s intensity.
Understanding Negative Springback Negative or positive springback pertains to the direction of deformation. Negative values denote deformation in the -Z direction, while positive values indicate deformation in the +Z direction. Springback possesses a directional component alongside its magnitude, necessitating direction specification in reports.
Crunching the Springback Numbers Calculating springback entails knowledge of material elastic properties (YS and TS), bend radius, material thickness, among other factors. For straightforward straight line bending, manual calculations might suffice. However, intricate operations demand the use of sheet metal forming simulations.
Tackling Springback Challenges Diverse strategies exist to combat springback in sheet metal parts. For simple straight line bends, overbending can be effective, especially with folded parts on brake presses. For more complex scenarios, particularly involving intricate 3D parts, sheet metal forming simulations prove indispensable for gauging and adjusting springback.
Cutting-edge simulation software, like AutoForm, predicts springback shapes and automatically compensates in the opposite direction. However, achieving the desired result often requires bending the part more than the original springback amount, frequently in a 3D fashion.
Beyond springback compensation, elongating the entire part during metal forming processes is another approach. This technique fortifies the surface area through increased plastic deformation from stretch forming, thus retaining the desired shape.
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Photo and article with all rights reserved, courtesy of StampingSimulation.com.