The Research About The Influence Law Of Shape Defect Of Strip On Sheet Metal’s Springback Of Stamping

Springback is an unavoidable common phenomenon in the process of cold stamping.The existence of springback will seriously affect the shape and size precision and surfacequality of the stamping parts. For the stamping sheet metal, in its production process,factors like rolling, welding and quenching may results in residual stress in its internal.When the residual stress is small, the sheet metal will not appear macro wrappingdeformation which is called potential shape defects; while when the residual stress is great,the sheet metal will occur macro wrapping deformation which is called obvious shapedefects. Related literature shows that the existence of residual stress can affect themechanical properties of sheet metal and influence the process of plastic forming. Whilethe existing research of springback prediction in both theoretical calculation and finiteelement simulation doesn’t consider the influence of the initial residual stress.In the actual stamping process, sheet metal often has some initial residual stresswithin it (shape defects). In order to obtain the influence law of the initial residual stresson sheet metal’s stamping springback, theoretical analyses and finite element simulationwere combined. Firstly, based on the plane strain assumption and through the stripdivision thought, bending springback angle model of sheet metal with shape defects wasestablished by using the material model complying with Mises yield criterion and linearhardening. Also, the springback formula of curvature and the springback equation ofcurved surface were deduced. Then the simulation analyses of springback under differentresidual stress peak and different thickness were conducted by using the finite elementsoftware ABAQUS and the theoretical springback value were contrasted with thesimulation springback value. The theoretical calculations and the simulation results had agood agreement which verified the correctness of the theoretical model and the influencelaw of the initial residual stress on sheet metal’s stamping springback was obtained.In addition, in the simulation analyses of springback for sheet with shape defects, theinfluence law of the initial residual stress on sheet metal’s section stress changing anddeformation were also researched relatively. For the former, superposition effects ofdifferent kinds of initial residual stress (tensile stress, non stress and compressive stress) and loading stress were mainly analyzed; for the latter, the influence of initial residualstress on stamping deformation under different residual stress peak and different thicknesswere mainly analyzed.