Implementation of Microstructural Material Phenomena in Macro Scale Simulations of Forming Processes

The paper deals with problems related to full/macro scale simulations of industrial forming processes. Large-scale numerical simulations and virtual modeling are replacing prototypes in order to reduce costs and time. This requires accurate and reliable predictions. To satisfy these requirements, sophisticated material models including micro- structural phenomena as phase transitions, aging, and recrystallization have to be considered on macro scale level simulation. Solution strategies are discussed and some examples are given of complex thermo- mechanically coupled forming simulations

On Anisotropy, Objectivity and Invariancy in finite thermo–mechanical deformations

In elastic–plastic finite deformation problems constitutive relations are commonly formulated in\ud terms the Cauchy stress as a function of the elastic finger tensor and an objective rate of the Cauchy stress\ud as a function of the rate of deformation tensor. For isotropic materials models this is rather straight forward,\ud but for anisotropic material models, including elastic anisotropy as well as plastic anisotropy, this may lead to\ud confusing formulations. It will be shown that it is more convenient to define the constitutive relations in terms\ud of invariant tensors referred to the deformed metric. An alternative decomposition of the deformation tensor is\ud introduced that can easily be linked to the additive decomposition of the velocity gradient into a spin tensor and\ud a rate of deformation tensor. Constraints for constitutive equations are formulated based on thermodynamics

Tool deformation during the shape rolling of stator vanes

Tool deformation is an important issue in the shape rolling of stator vanes as it directly\ud influences the thickness of the rolled vane. This means that for the design of an accurate production process\ud the deformation of the tools has to be accounted for. The shape rolling of symmetrical straight vanes has been\ud investigated. This rolling process is considered stationary, because these vanes have a constant cross-section\ud over the length. Therefore an ALE formulation is suitable to calculate the steady state. The deformation of\ud the sheet as well as the deformation of the tools have been calculated with the developed finite element model.\ud Some results of these simulations are presented in this pape

Modelling of ductile failure in metal forming

Damage and fracture are important criteria in the design of products and processes. Damage models can be used to predict ductile failure in metal forming processes. Nonlocal models avoid the mesh dependency problems of local damage models. A nonlocal damage model has been implemented in LSDYNA using the user-subroutines UMAT and UCTRL1. The implemented model will be compared with\ud results obtained with the available option in LS-DYNA to combine *MAT PLASTICITY WITH DAMAGE with *MAT NONLOCAL. Advantages and disadvantages of the different implementations will be discussed. The user nonlocal damage model has been applied to a bending and a blanking process. Results of these simulations will be shown

3D FEM simulations of the rolling of stator vanes, including tool deformation

Tool deformation is an important issue in the shape rolling of stator vanes as it directly influences the thickness of the rolled vane. This means that for the design of an accurate production process the deformation of the tools has to be accounted for. The shape rolling of symmetrical straight vanes has been investigated. Because these vanes have a constant cross-section over the length, this rolling process can be considered as a stationary process. Therefore an ALE formulation is suitable to calculate the steady state. The deformation of the sheet as well as the deformation of the tools have been calculated with the developed finite element model. Some results of these simulations are presented in this paper

3D FEM Simulation of shape rolling using an ALE method

The shape rolling of stator vanes has been modelled in 3D using the finite\ud element method. Till now only the rolling of straight vanes, which have a constant cross section, is studied. Therefore this rolling process can be considered as a stationary process. Such processes can be described as a flow problem using the Arbitrary Lagrangian Eulerian (ALE) formulation. This makes it possible to follow free surfaces and to adapt the mesh in order to avoid large element distortions, to keep or create refinements were needed. The mesh topology however remains constant during a simulation. Topics of the ALE formulation such as mesh relocation, transfer of state variables etc. will be addressed in the paper. The tools are modelled as deformable bodies, as tool deformation is the most important reason for the deviation of the vane dimensions from the required dimensions. 3D FEM simulations have been carried out of the rolling of a test vane. Some characteristic results, such as material flow, tool deformations, stresses and strains, will be shown