ICTMS 2022 in Grenoble / France (June 27 - July 1, 2022)


1.    Introduction

Metal foams are used in a wide range of applications, such as in energy dissipation and as lightweight materials. As integral part of a structure, the mechanical characteristics of metal foams and their response to external load need to be well understood. To gain greater insights, we have used lab-based dynamic computed tomography (CT) provided by Tescan to visualize uninterrupted compression of aluminum metal foams. Mechanical simulations of the same samples run with the simulation software GeoDict [1] are then coupled to these results. The dynamic CT reveals different modes of deformation, like buckling or bending of struts and collapsing of cells. Moreover, the displacement and deformation of pores can be analyzed once the scan is imported into the software.

2. Materials and Methods

The simulation of the compression of 35% is possible thanks to the voxel-based FFT solver FeelMath [2] in the GeoDict simulation software. By comparing simulation and scan, the simulation can be validated in two ways: First, the load curves show whether the stresses in the foam are similar in simulation and experiment. Second, the different deformation modes observed in the simulation are compared to the deformation modes in the scan, as well as the evolution of pore shapes with increasing compression. 

3. Results and Conclusion

Two samples from the same foam are tested, analyzed, and simulated. The comparisons show very good agreement in the stress-strain curves and also in the observed geometric deformations (Fig. 1). Differences are observed in the interval in which a specific cell starts collapsing. This is due to the fact that boundary conditions in tangential- and in load-direction are not perfectly identical and that small impurities or pores in the struts might be present but not captured by the CT. For the overall results, this has no effect when the sample under observation is large enough. We successfully verify that the simulation setup is valid not only on a Digital Twin, obtained by importing a CT scan, but also on a Statistical Digital Twin of a foam which is digitally generated based on the geometrical analysis of the scan. This makes possible to create digital foam structures with desired properties and to predict their deformation. Thus, digital parameter studies  may be performed using simulation software without the need to manufacture the foam in reality.

4. References 

[1] A. Wiegmann et al, doi.org/10.30423/release.geodict2022 
[2] M. Kabel et al, doi.org/10.1007/s00466-019-01713-3

Speaker: Andreas Grießer, M.Sc. (Math2Market GmbH)