Project manager:

• martin [dot] abendroth [at] imfd [dot] tu-freiberg [dot] de (Dr.-Ing. Martin Abendroth)
• bjoern [dot] kiefer [at] imfd [dot] tu-freiberg [dot] de (Prof. Dipl.- Ing.Ing. Björn Kiefer, Ph.D.)

Project staff:

• Dr.-Ing. Johannes Storm (2011-2015)
• Dr.-Ing. Christoph Settgast (2015-2019)
• Dr.-Ing. Alexander Malik (2019-2023)

Porous ceramic structures, which are characterised by high thermal resistance and good design options for filter structures, are predominantly used to filter liquid metals. In addition to functional properties such as porosity, filtration efficiency, flow behaviour and chemical reactivity, which are key to filter quality in molten metal treatment, the mechanical properties of the filter also play an important role. The partial or total breakage of a filter system causes considerable technological damage and contamination of the melt. If the filter material deforms too much as a result of pressure softening, the filter function is severely impaired or even completely prevented by clogging. It is therefore essential to ensure the strength of the filter material and the filter structure as a component against thermal and mechanical stresses during the filtration process. This applies to resistance to single or repeated thermal shock and viscoplastic deformation during the stresses caused by the molten metal. In order to technologically increase the melt throughput, filters with diameters > 200 mm will be required in future, which will lead to disproportionate bending stresses, pressure softening and larger temperature gradients. Due to the geometrically complex design of highly porous filter structures such as ceramic foams, etc., the evaluation of thermal shock and creep behaviour can only be solved using a multi-scale modelling approach and numerical simulations.

The aim of the project is to develop meso- and macroscopic material models and to provide simulation tools for evaluating the thermal shock resistance and pressure softening of specific filter structures. The project thus serves as an interface to the materials science investigations in project area C of the SFB 920 and also creates a bridge to the research, optimisation and design of new, more complex filter systems in project area A.

When creating the computer-generated model, the SurfaceEvolver software can be used to simulate interfaces with minimal surface energy. For the simulation of foams, this method
can be used to generate the PU backbone, which is ultimately bordered by an interface between computer-generated Kelvin cell bubbles and the fluid of a PU foam. Furthermore, this can be used to approximately describe the impregnation and spray coating process, in which a defined volume of liquid (slurry) is distributed on the base structure in such a way that the surface area of the solid part is minimised. A volume model can be generated from these physically based surface meshes which, in conjunction with the developed material law, can be used in the FEM to calculate the local stress and strain fields under systematically varied external loads. The local stress and strain fields can be used to derive criteria that can be used to make statements about the onset of non-elastic deformations or failure as a result of critically loaded cracks.