Mechanism of plastic deformation in chain die forming of variable cross section

Chain die forming is a new type of sheet metal forming process. The material flow law and characteristics of chain die forming process were studied through simulation. The analysis results show that the maximum principal strain at the corner of the variable section forming part is larger, and the direction is perpendicular to the outside bending surface; the maximum principal strain at the concave arc region in the flange is tensile strain, which decreases along the height direction of flange from high to low; the flange height and forming angle have great influence on the longitudinal strain of the forming part, and increasing the height of the flange and forming angle can increase the longitudinal strain of the flange; the effect of material properties on the longitudinal strain of the forming part is small. The longitudinal strain of the variable cross section was extracted from the simulation model. The results show that the four arc zones in the flange of variable cross section part have larger longitudinal strain, where tensile or compressive deformation occur during forming process, but the equivalent plastic strain mainly concentrates in bending areas of variable cross section part. The simulated results were verified through experiment of chain die forming of variable cross section tests, and the experimental results are in good agreement with the simulation results.