3-D FEM analysis of sheet metal deep drawability and stretchability - application of FEM analysis to research formability of sheet metals

Square cup deep drawing and hemispherical punch stretching, the optimal means of forming sheet metals, were numerically analyzed by the three-dimensional finite element method (FEM) based on the membrane theory. Methods for predicting and evaluating the formability of sheet metals and for avoiding the fracture of sheet metals were also studied. The estimation index of breakage for sheet metals in the forming processes was determined from the strain calculated by finite element method (FEM) analysis and the theoretical forming limit diagram. In the analysis of square cup deep drawing, the material properties and forming conditions were investigated for their effects on the strain path and fracture limit at weak portions such as the punch shoulder, and their quantitative relationships were clarified. In the analysis of hemispherical punch stretching, it was computationally confirmed that changing the width of square blanks changes the strain state from uniaxial tensile deformation to plane strain deformation. The effect of blank width on the limiting dome height was analyzed, and the analytical results were confirmed to agree with the experimental results in tendency.