FE vibration analyses of novel conforming meta-structures and standard lattices for simple bricks and a topology-optimized aerodynamic bracket

Todd Doehring,Thomas Harris,Alan Freed,William Nelson

doi:10.1038/s41598-020-78239-9

Abstract

Additive manufacturing (AM) enables production of components that are not possible to make using traditional methods. In particular, lattice-type structures are of recent interest due to their potential for high strength-to-weight ratios and other desirable properties. However, standard periodic lattice structures have problems conforming to complex curved and multi-connected shapes (e.g. holes or sharp-to-smooth mating edges). In addition, standard lattices have well known shear and fatigue weaknesses due to their periodic basis/structure. To address these problems, we developed a new type of shape-conforming meta-structure (HGon) that extends lattices, enabling automated conforming to complex shapes and parametric meta-topology control. HGons also have unique vibration dampening and optimization capabilities. This study presents initial FE analyses of (Part 1) dynamic vibration responses of new HGon meta-structures compared with periodic lattices of equivalent density for a series of basic rectangular structures and (Part 2) a complex multi-connected aerodynamic bracket with field-based stress meta-topology optimization. Results show significantly enhanced vibration dampening behavior and superior strength-to-weight ratios for HGon meta-structures as compared to standard lattices.

Highlights

This study presents initial FE analyses of (Part 1) dynamic vibration responses of new HGon meta-structures compared with periodic lattices of equivalent density for a series of basic rectangular structures and (Part 2) a complex multi-connected aerodynamic bracket with field-based stress meta-topology optimization
Highest stress concentrations were found at the base of the lattice structures, but were reduced for the HGon structures
This study presented and analyzed a new type of meta-structure that can enable unprecedented vibration control, conform to complex shapes, and greatly reduce mass/weight for both simple bricks and complex, multi-connected structures

Summary

Methods

The basic meta-structure generation procedure starts by (step 1) generating the initial 3D mesh structure from the shape of interest, usually from a triangular STL surface/solid or similar format. Both Delaunay and fractal refinement[22] are used for the initial ‘base’ meta-mesh, with added steps for HGon-type and hybrid tetrahedral-hexahedral structures. (step 3) for the same nodes and edges, locally implicit meta-structures are added (similar to alpha shapes[23] capsules, spheres, etc.) with accurate positioning as per step 2 These implicit structures add novel local parametric shape control that cannot be done using explicit structures alone. (step 4) the explicit and implicit local meta-structures are combined using a proprietary algorithm that automatically extracts an optimized 3-D manifold meta-shape (HGon) based on the input meta-parameters

Results

Discussion

Conclusion