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); Golam Newaz, Ph.D. (Committee Member)

Degree Name

Doctor of Philosophy (PhD)

Abstract

Lattice structures (LSs) have been exploited for wide range applications including mechanical, thermal, and biomedical structures because of their unique attributes combining the light weight and relatively high mechanical properties. The first goal of this research is to investigate the effect of strut orientation and length on the compressive mechanical characteristics of body centered cubic (BCC) LS subjected to a quasi-static axial compressive loading using finite element analyses (FEA). In this study, two lattice generations were built and analyzed in commercial finite element (FE) software, ABAQUS/CAE 2016 using “smart procedure”, a meshing technique which was developed for this research to reduce the computational time and increase the accuracy of results by creating hexahedral mesh elements. The first generation comprises thirteen models having fixed strut length with strut angle variation from 40° to 100° with a step of 5°. The second also includes thirteen models; however, having variant strut length, kept constant for a single unit cell and through the entire lattice model but varied from one model to another, corresponding to the same strut angle variation as the first generation. Besides, there is a common model between the two sets, called the reference model (RM) out of which all other models in both sets were composed such that the total number of models adopted in the current study are (25), having the same strut diameter of 1mm. The RM represents the standard BCC configuration of 70.53° strut angle with 5mmx5mmx5mm dimensions for a lattice unit cell and all other models were created from it based on changing the strut angle and length with 3x3x3 unit cells in x, y and z directions. Furthermore, specimens of the RM were fabricated by a fused deposition modeling (FDM) technology using Acrylonitrile Butadiene Styrene (ABS) material and tested experimentally under compression for the purpose of validating the employed boundary and loading conditions. Predicting the mechanical characteristics and structural parameters of LSs is of high importance in the field of lattice design due to the fact that the lattice fabrication might be challenging, time-consuming or expensive. The other objective of this dissertation is to develop generalized closed-form equations using scaling laws and finite element methods (FEMs) to predict not only the compressive mechanical properties (CMPs) but also the geometrical parameters (GPs) with considering the effect of both lattice cell tessellations and material distribution at the strut intersection. For that purpose, the relative density (RD) is varied from 0.14-0.3 with a step of 0.02 by changing the strut diameter, corresponding to each strut angle from 40° to 100° with a step of 10° selected from each generation such that (63) models of fixed strut length and other (63) models of variant strut length were created. By this way, the total number of models adopted to achieve this goal are (117), all built and analyzed using ABAQUS/CAE 2016. The data ensuing from FE simulation of the axial compression test were thereafter used to find the relationships of relative elastic modulus (RE) with RD and relative strength (RS) with RD in order to determine Gibson and Ashby’s pre-factors, C_1, C_5 , n and m. In addition, all other GPs were correlated with the RD based on the measurements of the geometries of the117 lattice models using ABAQUS diagnostic tools. The significance of these factors is not only in predicting the CMPs and GPs but also in providing systematic analyses for changing the deformation mechanisms with the strut angles.

Page Count

171

Year Degree Awarded

2020


Included in

Engineering Commons

Share

COinS