Research on the establishment and influence mechanism of critical wrinkling limit diagram (WLD) of plate and shell forming under mold constraints

Abstract With the rapid development of manufacturing technology in the fields such as aerospace, aviation, national defense, and automobiles, the demands for lightweight, toughening, and forming accuracy of products have increased. As one of the main defects in the plastic forming of thin-walled components, wrinkling failure has always been a key element in forming control. The sheet metal is restrained by the mold in actual forming process and the wrinkling is significantly affected by the boundary conditions. To study the effect of the mold constraints on the wrinkling failure in the actual forming process, a stretching wrinkling test of wedge plate with the boundary constraint conditions of mold was designed. By establishing the simulation model for wrinkling failure of sheet forming under mold constraints and its wrinkling limit diagram (WLD), the accurate prediction of sheet metal wrinkling failure form and the critical state in actual forming was realized. At the beginning of the research, the wedge plate tensile test was implemented for using as verification for simulation results, then the wrinkle simulation model of Buckle-Dynamic with the instability mode as the initial defect was established. By combining with the non-contact full-field strain measurement system DIC to obtain the strain data of the specimens in the test process, the accuracy of the simulation model was verified. On this basis, the critical wrinkling limit diagram (WLD) was established for the wrinkle partition on the wedge specimen, and the influence of stress state, stress loading path, principal compressive stress increment, principal stress ratio factors on the distribution and propagation direction of wrinkles, as well as the morphology and characteristics of WLD are discussed. The research content of this study is of guiding significance for the prediction of the actual wrinkling failure of sheet and shell forming.