PSI - Issue 28

Florian Vlădulescu et al. / Procedia Structural Integrity 28 (2020) 637–647 Vl ă dulescu and Constantinescu / Structural Integrity Procedia 00 (2019) 000–000

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macroscale structure is considered as a multiscale problem since the dimensions of the lattices are typically relatively small compared to the size of the macroscale part. When lattice optimization is performed, one can, for example, maximize rigidity or minimize the mass as an optimization objective, with the same optimization constraints available as in the case of standard topological optimization.

Fig. 3. Mode shape corresponding to the first natural frequency.

We used a cubic lattice cell, the size of lattice cell being identical to that used for the finite element (8×8×8 mm), although this is not mandatory. For the solution, a maximum threshold of 500 iterations is initially set, but as it is not a very large model the solution is obtained after only 30 iterations. The new structure of the bracket is shown in Fig. 4 for a regular cube lattice (cubic cell). The working methodology used in a lattice optimization analysis is generally similar to that used in a standard topology optimization analysis. But there are some particularities which will be highlighted in the following. When performing a lattice optimization, a lattice structure is obtained having its geometrical appearance (size, shape) according to the input data defined previously.

Fig. 4. Lattice model of the bracket: lateral view for regular cube lattice – cubic cell.

After solving the lattice optimization analysis, the new material distribution can be observed in Fig. 5. In the red area, practically no material is removed and as it goes to the blue area more and more material is removed. In fact, after performing the lattice optimization, results are automatically converted in ANSYS SpaceClaim Direct Modeler in an “stl” format file and the lattice geometry is generated, as to be eventually used in 3D printing. It should be also mentioned that the initial geometry of the bracket was modelled also in ANSYS SpaceClaim Direct Modeler. The lattice model is an input data for the modal analysis which will provide new natural frequencies. When using a cubic cell, the first natural frequency has now a value of 1227 Hz (Fig. 6), which increased considerably compared