Publication Date

2020

Document Type

Dissertation

Committee Members

Ahsan Mian, Ph.D. (Advisor); Raghavan Srinivasan, Ph.D. (Committee Member); Henry Young, Ph.D. (Committee Member); Joy Gockel, Ph.D. (Committee Member); Uttam Chakravarty, Ph.D. (Committee Member)

Degree Name

Doctor of Philosophy (PhD)

Abstract

Lattice cell structures (LCS) are the engineered porous structures that are composed of periodic unit cells in three dimensions. Such structures have many scientific and engineering applications, such as in vessel gas technology, thermal systems, mechanical and aerospace structures, etc. for which lightweight, high strength, and energy absorption capabilities are essential properties. To have an optimized design, finite element analysis (FEA) based computational approach can be used for detailed analysis of such structures, sometime in full scale. However, developing a large-scale model for a lattice-based structure is computationally expensive. If an equivalent solid FE model can be developed using the equivalent solid mechanical properties of a lattice structure, the computational time will be greatly reduced. The main objective of this research is to develop a material model which is equivalent to the mechanical response of a lattice structure. In this study, the mechanical behavior of body centered cubic (BCC) configuration and its derivative such as a BCC placed inside boxed frame (here, termed as `InsideBCC’) under compression and within elastic limit is considered. The BCC and InsideBCC configurations are chosen because they provide the bounds of the mechanical properties of LCS involving BCC derivatives. First, the finite element analysis approach and theoretical calculations are used on a single unit cell of BCC and InsideBCC for several cases (different strut diameters and cell sizes) to predict equivalent solid properties. The equivalent quasi-isotropic properties required to describe the material behavior of both BCC and InsideBCC unit cells are equivalent Young’s modulus (E_e), equivalent shear modulus (G_e), and equivalent Poisson’s ratio (ν_e). The results are then used to develop two separate neural networks (NN) models so that the equivalent solid properties of a BCC or InsideBCC lattice of any geometrical parameters can be predicted. The input data of NN are bulk material properties and geometrical parameters and output data are equivalent solid mechanical properties. For each unit cell configurations, two separate FEA models are then developed for compression loading: (a) one with 5 x 5 x 4 cell for BCC and the other with 6 x 6 x 4 cell for InsideBCC, and (b) one completely solid with equivalent solid properties obtained from NN. In addition, the BCC and InsideBCC LCS specimens are fabricated on a Fused Deposition Modeling uPrint SEplus 3D printer using Acrylonitrile Butadiene Styrene (ABS) and tested under compression. Experimental load-displacement behavior and the results obtained from both the FE models are in good agreement with the experimental data within the elastic limit.

Page Count

118

Year Degree Awarded

2020


Included in

Engineering Commons

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