PSI - Issue 64

Hendrik Holzmann et al. / Procedia Structural Integrity 64 (2024) 1303–1310 Hendrik Holzmann / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 2. Overview of the used workflow.

The framework initiates with a parametric mechanical finite element model set up in Ansys ® MAPDL. The model geometry is derived from experimental samples. It is set up from several equal substructures that are periodically arranged. Each consists of the geometry for two metal sheets and the core of PIR foam. For this work, a structure composed of 15 substructures (each with dimensions of 100x100x25 mm³) is used (cf. Fig. 3 (a)).

(a) (b) Fig 3: Sandwich element geometry with substructures (a) and finite element mesh with boundary conditions indicated in green (b).

Every substructure is meshed with finite elements. For the metal sheets, a solidshell mesh is used. For the foam, a tetrahedron mesh is used since this can be applied for randomized geometries which is the case for the foam in this work. The mesh size on top of the sandwich element is adjusted to the relevant frequency range. On the bottom of the structure, it is left coarse to save computation time. The mesh between the substructures is identical thus a contact is achieved by combining incident nodes. A periodic boundary condition of fixed-loose bearings (cf. Fig. 3 (b)) with free rotation is implemented in the parametric model to simulate the bearing arrangement like in the production line. The parametric scattering of material parameters – Young ’ s modulus and densities of foam and steel sheets is included in the model, ensuring a representation of real-world uncertainties. For the modulus of elasticity of the foam, a normally distributed variation is assumed. A standard deviation of 7.85 % around the mean value of 3.75 MPa is used from experiments. The defects are geometrically modeled using hemispheres (cf. Fig. 4) with a variable diameter of 1 cm to 5 cm. The size is assumed to be uniformly distributed. Furthermore, the two-dimensional location in the sandwich structure is furthermore randomised with a uniform distribution.