Micro-architectured materials for noise and vibration control in high voltage products – design and modelling

University essay from Uppsala universitet/Tillämpad mekanik

Abstract: Many Hitachi ABB Power Grids (HAPG) products vibrate and emit noise, but legal limitations of these parameters fuel the development of energy absorption methods used on products. Methods such as Constrained Layer Damping (CLD). Modern CLD research focuses on the application of micro-architectured structures in the damping layer and improving numerical models for streamlined product optimization. Focus was on developing a numerical computational homogenization, Finite Element Analysis (FEA), method for investigating the mechanical properties of a linear viscoelastic material model applied to a micro-architectured octet lattice. Computational homogenization of a Representative Volume Element (RVE) is performed in COMSOL Multiphysics 5.6. Initially, a linear elastic and then a linear viscoelastic material model applied to an octet lattice structure is homogenized for several lattice nominal densities. Linear isotropic viscoelastic bulk material properties were extracted from stress relaxation tests of SLA 3D-printed Formlabs Standard Black Methacrylate Resin measured in a Shimadzu AGS-X series universal test frame 20kN Table Top Model. Extracted properties were applied to a Prony Series code with one term, imitating a viscoelastic material of Standard Linear Solid (SLS) type. Recreated numerical relaxation tests validated the method of applying the viscoelastic material model in the computational model before applying the material model to an octet lattice structure. An eigenfrequency analysis was performed on SLA 3D-printed octetlattice blocks of the same Standard Resin. The computationally homogenized linear elastic octet lattice results were validated using analytical Euler-Bernoulli beam theory for lower lattice densities. Engineering constants E, G, and v analyzed from the homogenized viscoelastic octet lattices displayed a dependency on the nominal density agreeing with literature. The numerical viscoelastic relaxation time was also found to be independent of the nominal density. Experimental eigenfrequency data was also collected from three viscoelastic octet lattice blocks and is suggested to be compared with numerical results in a future study.

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