New Mechanical Model And Applications Of Springback In Small Curvature Bottom Bending

Sheet metal stamping process is a common method of plastic forming, which hashigh efficiency, low cost, low power consumption and many other advantages, and hasbeen widely used in various industrial fields. However, it contains so complex physicalphenomena that makes process designing and controlling very difficult, thus many defectsappears in the forming process, and the most difficult one to predict and control isspringback.Considering a small arc of curvature as the research object, a new mechanicalmodel of springback analysis in sheet metal bottom bending was established, with finiteelement numerical simulation and experiment to further improve the springback predictionaccuracy.In terms of theory,based on the plane strain assumption,the moment and springbackanalysis model in sheet metal bending whose material was linear and hardening wasbuilt.Then the quantitative relationship of the bent radius of the plate before and afterunloading was given.By analyzing the elastic-plastic stress distribution in the smallcurvature of plate bottom bending,the relative shift and the curvature of the stress andstrain neutral layer was expressed,then the moment and springback analysis model in thesheet bottom bending with the real elastic-plastic meaning was established, thequantitative relationship among the moment、the curvature and the bottom-force waspresented and the maximum relative bent radius and ultimate expression of the bottombending was expressed.In the finite element numerical simulation,based on the ABAQUS finite elementanalysis software,the stamping and springback process of the sheet metal bending wassimulated.Comparing with the theoretical results, the conclusion that radius of curvaturebecame smaller with the increase of bottom-force was verified.Under differentbottom-forces,the impact of the punch radius、the metal thickness and the frictioncoefficient on the springback was simulated and analyzed.In the experiment,by using two materials steel to form a a small arc AB of the arcpanel spring,the calibration deviation range between the theoretical and experimentalstudies in the elastic-plastic plate bottom bending.Through using different heat treatment processing to treat the bending test piece,the effect of various heat treatment for bendingspringback was determined.By changing the conditions of friction between the specimenand the sheet metal to carry out the bending experiments,the effects of friction conditionson the nature of the springback was qualitatively studied.