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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7. Conclusions Topology optimization helps us to design durable and lightweight components for any application. We can define objectives easily and apply controls to ensure that manufacturing requirements are met, minimum material thicknesses are set, and exclusion areas are defined. In a first stage, lattice optimization was used as an extended step from topology optimization, effective for practical engineering applications involving 3D printing. In the first step of this work an initial model of a mounting bracket considered as a case study was established through a finite element analysis. The boundary conditions were defined, and the Block Lanczos algorithm was used for computing the first six natural frequencies in a modal analysis. Also, the mass of the bracket was established. The lattice optimization method enabled us to compute an optimal variable density lattice distribution in the model. A new geometrical model was generated automatically by using the ANSYS software customized for lattice structures and cubic cells of two sizes were used. The 8×8×8 mm cell led to an increase of the fundamental frequency from 839 Hz for the unoptimized model to 1227 Hz for the optimized one and to 1366 Hz for the homogenized one, and mass was reduced from 45.5 kg to only 21.77 kg, less than half. The smaller cubic cell of 4×4×4 mm could not be used effectively. The obtained results can give confidence for the use of a lattice type topology optimization, but care should be taken as not to reduce too much the cell size, as the numerical solution may become tedious or ineffective. Homogenization proved to be more effective for optimization in analysing the modal response of the mounting bracket, by increasing the fundamental frequency and reducing its mass. The SMART feature is a promising tool to be used for simulating 3D crack propagation, but more refinements are needed as to better understand its particularities, especially is mixed mode situations. Acknowledgements The work of Florian Vlădulescu was supported by the project ANTREPRENORDOC, in the framework of Human Resources Development Operational Programme 2014-2020, financed from the European Social Fund under the contract number 36355/23.05.2019 HRD OP /380/6/13 – SMIS Code: 123847. References ANSYS 2019 R3 (2019a), Meshing User's Guide, ANSYS Inc., Canonsburg, USA. ANSYS 2019 R3 (2019b), Mechanical User's Guide, ANSYS Inc., Canonsburg, USA. ANSYS 2019 R3 (2019c), Material Designer User's Guide, ANSYS Inc., Canonsburg, USA. ANSYS 2019 R3 (2019d), Mechanical APDL Fracture Analysis Guide, ANSYS Inc., Canonsburg, USA. Arabnejad, S., Johnston, B., Tanzer, M., Pasini, D., 2016. Fully porous 3D printed titanium femoral stem to reduce stress‐shielding following total hip arthroplasty. Journal of Orthopaedic Research 35, 1774–1783. Bendsøe, M.P., Sigmund, O., 1999. Material interpolation schemes in topology optimization. Archive of Applied Mechanics 69, 635–654. Bendsøe, M.P., Kikuchi, N., 1988. Generating optimal topologies in structural design using a homogenization method . Computer Methods in Applied Mechanics and Engineering 71, 197–224. Cheng, L., Liang, X., Belski, E., Wang, X., Sietins, J.M., Ludwick, S., To, A., 2018. Natural frequency optimization of variable-density additive manufactured lattice structure: Theory and experimental validation. Journal of Manufacturing Science and Engineering 140, 105002. Cheng, L., Liu, J., Liang, X., To, A.C., 2018. Coupling lattice structure topology optimization with design-dependent feature evolution for additive manufactured heat conduction design. Computer Methods in Applied Mechanics and Engineering 332, 408–439. Cheng, L., Zhang, P., Biyikli, E., Kirca, M., Chmielus, M., To, A.C., 2017. Efficient design optimization of variable-density cellular structures for additive manufacturing: theory and experimental validation. Rapid Prototyping Journal 23, 660-677. Choi, J., Chae T-S., 2015. Effective stiffness and effective compressive yield strength for unit cell model of complex truss. International Journal of Mechanics and Materials in Design 11, 91–110. Daynes, S., Feih, S., Lu, W.F., Wei, J., 2019. Design concepts for generating optimised lattice structures aligned with strain trajectories. Computer Methods in Applied Mechanics and Engineering 354, 689–705. Deshpande, V.S., Ashby, M.F., Fleck, N.A., 2001. Foam topology: bending versus stretching dominated architectures. Acta Materialia 49, 1035– 1040. Huang, X., Xie, M., 2010. Evolutionary Topology Optimization of Continuum Structures . John Wiley & Sons. Jansen, M., Pierard, O., 2020. A hybrid density/level set formulation for topology optimization of functionally graded lattice structures. Computers & Structures 231, 106205.