The main aim of this thesis is to investigate the manufacturability of different gyroid
designs using Selective laser melting (SLM) process . This study paves the way for a better
understanding of design aspects, process optimization, and characterization of titanium
alloy (Ti6Al4V) gyroid lattice structures for bone implant applications.
First, A MATLAB® code was developed to create various gyroid designs and understand
the relationship between the implicit equation parameters and the measurable outputs of
gyroid unit cells. A novel gyroid lattice structure is proposed, where the porosity is graded
in a radial direction. Second, gyroid designs were investigated by developing a permissible
design map to help choose the right gyroid parameters for bone implants.
Third, response surface methodology was used to study the process-structure-property
relationship and understand the effect of SLM process parameters on the manufacturability
of Ti6Al4V gyroid lattice structures. Laser power was found to be the most significant
factor affecting the errors in relative density and strut size of gyroid structures. A
volumetric energy density between 85 and 103 J/mm3 induces the least errors in the
gyroid’s relative density.
Fourth, the quasi-static properties of the novel designs were compared to uniform gyroids.
The proposed novel gyroids had the highest compressive strength reaching 160 MPa.
Numerical simulations were studied to give insight into how manufacturing irregularities
can affect the mechanical properties of gyroids. Last, an in-depth defect analysis was
conducted to understand how SLM defects may influence the fatigue properties of different
Ti6Al4V gyroids. Thin struts have less internal defects than thick ones; thus, they show less crack propagation rate and higher normalized fatigue life. These favorable findings
contributed to scientific knowledge of manufacturability of Ti6Al4V porosity graded
gyroids and determined the influence of SLM defects on the mechanical properties of
gyroid designs for bone implants. / Thesis / Doctor of Philosophy (PhD) / This thesis studies the integration of design aspects, SLM manufacturability, and
mechanical characterization of Ti6Al4V gyroid lattice structures used for bone implants.
A MATLAB® code was developed to design novel porosity graded gyroids, and develop
permissible design map to aid the choice of different gyroid designs for bone implants..
Process maps were also developed to investigate the relationship among laser power, scan
speed, and the errors in the relative density of lattice structures. Moreover, the normalized
fatigue strength of thin struts gyoid was found to be higher than that of thicker
struts.Analytical models and finite element analysis (FEA) models were compared to
experimental results. The variation of the results gives a better understanding of the effect
of manufacturing defects. An improved insight of gyroids manufacturability has been
obtained by integrating the permissible design space with the process-structure-property
relationship, and the defect analysis of porosity graded gyroids.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/25797 |
| Date | January 2020 |
| Creators | Mahmoud, Dalia |
| Contributors | Elbestawi, Mohamed A., Mechanical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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