| Summary: | 碩士 === 淡江大學 === 機械工程學系 === 90 === A methodology for formulating an elasto-plastic finite element model, which is based on Prandtl-Reuss flow rule and Hill's yield criterion respectively, associates with an Updated Lagrangian Formulation. An extended algorithm is proposed to formulate the boundary condition, such as the yield of element, maximum allowable strain increment, maximum allowable rotation increment, maximum allowable equivalent stress increment, and tolerance for nodes getting out of contact with tool. The fractured thickness of a specimen in simple tension test is adopted as the fracture criterion in simulation. The numerical simulation results include relationship between punch load and punch displacement, variation of the workpiece thickness, distribution of stress, distribution of strain, and forming limit. The finite element model is developed to simulate isotropic, normal anisotropic, and anisotropic of hole-flanging penetration process. The accuracy of the finite element program is based on a comparison between the simulation and experiment outcomes.
In this study, several simulations are performed on diverse Lankford parameters R0, R45, R90 and distinct punch profile radius. When the orientation of expanded hole circumference to rolling direction is at , the thickness of workpieces is various from three types of analyses. Anisotropic analysis determines the thickest workpiece and isotropic analysis the thinnest. As to penetrated height, at the same orientation, isotropic analysis determines the highest workpiece and anisotropic analysis the lowest. When punch profile radius becomes greater, the distance of punch stroke increases progressively and maximum punch load decreases as well.
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