Stefan Benke

Towards integrative computational materials engineering of steel components

This article outlines on-going activities at the RWTH Aachen University aiming at a standardized, modular, extendable and open simulation platform for materials processing. This platform on the one hand facilitates the information exchange between different simulation tools and thus strongly reduces the effort to design/re-design production processes. On the other hand, tracking of simulation results along the entire production chain provides new insights into mechanisms, which cannot be explained on the basis of individual simulations. Respective simulation chains provide e.g. the basis for the determination of materials and component properties, like e.g. distortions, for an improved product quality, for more efficient and more reliable production processes and many further aspects. After a short introduction to the platform concept, actual examples for different test case scenarios will be presented and discussed.

Thermo-mechanical analysis of cast/mould interaction in casting processes

Abstract The numerical analysis of the thermo-mechanical interaction between the cast part and mould in casting processes requires a strong coupling between the thermal and mechanical simulation. This includes a 3-D frictionless contact algorithm and a model to describe the local heat transfer between part and mould as a function of the contact pressure or the formation of a local gap between both domains. Several features suitable for the analysis of solidification processes have been introduced in the classical master/slave contact algorithm like a temperature-dependent penalty factor and implemented in the software package CASTS. Benchmark tests and two industrial casting applications illustrate the correctness of the developed thermo-mechanical program and the ability to simulate complex cast parts.

Meso-Mechanical Modeling of Damage in Metal Foams

A finite element model for the elasto-plastic and damage behaviour of a low-density open-cell metal foam is presented. The metal foam is modeled as a three dimensional framework of slender struts. The finite element formulation for the behaviour of the struts makes use of the Timoshenko beam theory. Within the struts a layered approach is adopted to simulate the progressive growth of plasticity and continuum damage from the extreme fibers towards the neutral axis. The arrangement of the struts is random and created by Voronoi tessellation. The macroscopic properties of the foam are determined from the representative volume element by the use of a numerical homogenization algorithm.

Parallelising computational microstructure simulations for metallic materials with OpenMP

This work focuses on the OpenMP parallelisation of an iterative linear equation solver and parallel usage of an explicit solver for the nonlinear phase-field equations. Both solvers are used in microstructure evolution simulations based on the phase-field method. For the latter one, we compare a graph based solution using OpenMP tasks to a first-come-first-serve scheduling using an OpenMP critical section. We discuss how the task solution might benefit from the introduction of OpenMP task dependencies. The concepts are implemented in the software MICRESS which is mainly used by material engineers for the simulation of the evolving material microstructure during processing.

On a Class of Thermo-visco-plastic Constitutive Equations for Semi-solid Alloys

The behavior of semi-solid alloys is quite different in tension, compression and shear and depends strongly on the morphology of the micro-structure. This article outlines a generalized viscoplastic material model for semi-solid alloys which reflects this complex viscoplastic behavior. From the generalized model a number of well known yield functions and viscoplastic material models for semi-solid and solid materials can be reproduces. The general model is applied to describe the behavior of the semi-solid A356 alloy below the coherency temperature during equiaxed solidification.