| Computer simulation methods for metal forming processes based on Arbitrary Lagrangian-Eulerian (ALE) finite elements, adaptive mesh deployment techniques, classical and hydrodynamic friction models, are developed.; The use of ALE description, which employs a referential system neither attached to material nor fixed in space, provides a flexibility for mathematical formulation. It overcomes the drawbacks associated with the Lagrangian description owing to the large plastic deformation of the workpiece and the interaction between the tool and the workpiece.; New 8-node brick multiple-quadrature-point elements are developed for three dimensional metal forming analyses. Element internal forces are underintegrated to reduce computational expenses and the hourglass control is provided to remove spurious singular modes. These elements experience no volumetric locking in bulk deformation analysis and are also successfully applied to sheet metal forming analysis via special treatment on the assumed shear strain rates to avoid shear locking.; Two classical friction models, Coulomb friction law and Tresca type friction law, as well as a hydrodynamic friction model, based on the ALE finite element method with an average flow model, are employed to predict friction forces on the tool-workpiece interface. In the hydrodynamic friction model, friction stress is expressed in terms of forming variables such as surface roughness, lubricant and workpiece properties, film thickness, forming speed, and process geometry. It provides a more realistic modeling of contact, lubrication, and friction stress. The proposed algorithm for the hydrodynamic lubrication analysis with surface roughness has been incorporated into an existing finite element code for flow analysis.; Several numerical simulations of metal forming processes, such as ring rolling, strip rolling, forging and sheet metal forming are presented. Simulation results show good agreement with available experimental data and numerical results found in literature. |
