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Proposing Institution

Department Werkstoffwissenschaften Lehrstuhl Allgemeine Werkstoffeigenschaften (WW I)
Project Manager

Zhuocheng Xie
Martensstr. 5
91058 Erlangen
This Proposal is for the Summer of Simulation (SOS) 2016.The mechanical properties of metals change significantly when their characteristic feature size (e.g., film thickness, wire diameter, ligament size) is reduced to the nanometer scale. For these reasons, standard continuum models of crystal plasticity and elasticity as used in the finite element method (FEM) are no longer valid at these small scales.In the overarching project, we want to use compression tests on nanoporous gold (NPG) to directly compare experimental results with FEM and atomistic simulations on identical samples to better understand the specific atomic-scale deformation mechanisms. The ultimate goal is to provide insights for the development of physics-based continuum models for small-scale plasticity. NPG is an ideal model system, as the ligament size can be precisely tailored, and nanopillar samples can be produced by focused ion beam (FIB) milling. Within the GRK1896, these pillars are produced and characterized in 3D by electron tomography and compressed in situ in the TEM or SEM, where digital image correlation (DIC) is used to determine the local strain. Within our group, we have recently developed methods to construct atomistic samples from tomography data4 as well as to impose experimentally-informed boundary conditions on atomistic simulations5 and successfully applied them to the study of superalloys.The smallest NPG nanopillars contain between 1-10 billion atoms. Molecular dynamics (MD) simulations of full compression tests of such large samples would easily exceed 10 Mio CPUh, therefore we will focus on subsets of the pillar or specific ligaments, where the differences between experiments and FEM calculations are most pronounced. With the test account provided through the SOS, we want to evaluate different load- balancing schemes for the porous structure, data-compression, -handling and -analysis for these large simulations with up to 1 billion atoms, using two atomistic simulation packages for large-scale MD simulations: IMD and LAMMPS. These codes are routinely used on massively parallel platforms and show excellent scaling. For analysis and visualization we will use OVITO, which has been demonstrated to be able to handle such large-scale structures.-->

Impressum, Conny Wendler