Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 16 of 16
Full-Text Articles in Engineering
Effect Of Size And Shape Parameters On Microstructure Of Additively Manufactured Inconel 718, Showmik Ahsan
Effect Of Size And Shape Parameters On Microstructure Of Additively Manufactured Inconel 718, Showmik Ahsan
Browse all Theses and Dissertations
Additive Manufacturing (AM) methods are promising in applications where complex part geometries, exotic materials and small lot sizes are required. Aerospace manufacturing stands to use AM methods extensively in the future, and frequently requires temperature- and corrosion-resistant alloy materials such as Inconel 718. However, the microstructural evolution of Inconel 718 during additive manufacturing is poorly understood and depends on part size and shape. We studied the microstructure of Inconel 718 parts manufactured by Laser Powder Bed Fusion in order to further elucidate these dependencies. Microstructural analysis, SEM imaging, EBSD scans and Microhardness testing were performed.
Vibration Bending Fatigue Analysis Of Additively Repaired Ti-6al-4v Airfoil Blades, Lucas Jordan Smith
Vibration Bending Fatigue Analysis Of Additively Repaired Ti-6al-4v Airfoil Blades, Lucas Jordan Smith
Browse all Theses and Dissertations
Repairing airfoil blades is necessary to extend the life of turbine engines. Directed energy deposition (DED) additive manufacturing (AM) provides the ability to add material at a specific location on an existing component. In this work, AM repairs on Ti-6Al-4V airfoil blades were analyzed to determine what effect the repair will have on the blade performance in high cycle vibration fatigue testing. Targeted sections were cut out of airfoil blades near high stress locations and repaired using DED. To understand the defects that arose with this type of repair, computed tomography imaging was used to quantify the defects from the …
Effect Of Build Geometry And Build Parameters On Microstructure, Fatigue Life, And Tensile Properties Of Additively Manufactured Alloy 718, Anna Dunn
Browse all Theses and Dissertations
Additive Manufacturing (AM), particularly laser powder bed fusion, is being studied for use in critical component applications. Tensile and fatigue testing shows differences when built using different laser powers. However, when fabricated in an as-printed geometry, the gauge sections of the two specimens are different and experience different thermal behavior. This work explores microhardness, microstructure size, Niobium segregation, and porosity from samples made with varying laser power and different build geometry sizes representative of the gauge sections in the tensile and fatigue bars. Results show that microhardness varies spatially across the sample. Smaller diameter metallographic coupons (fatigue diameter) have a …
Correlating In-Situ Monitoring Data With Internal Defects In Laser Powder Bed Fusion Additive Manufacturing, Andrew J. Harvey
Correlating In-Situ Monitoring Data With Internal Defects In Laser Powder Bed Fusion Additive Manufacturing, Andrew J. Harvey
Browse all Theses and Dissertations
The presence of defects within laser powder bed fusion (LPBF) parts can lead to reduced mechanical properties and life of components. Because of this, the ability to detect these defects within the parts is critical before the part is subject to its intended loading. Normally the parts are subjected to a quality analysis once they are completed however, this process is typically expensive and time consuming. A solution for these problems is to sense the creation of defects and pores in the parts in-situ, while the part is being fabricated. One proposed method of in-situ monitoring is visible spectroscopy to …
Primary Processing Parameters And Their Influence On Porosity And Fatigue Life Of Additively Manufactured Alloy 718, Luke C. Sheridan
Primary Processing Parameters And Their Influence On Porosity And Fatigue Life Of Additively Manufactured Alloy 718, Luke C. Sheridan
Browse all Theses and Dissertations
In many structural applications void-like defects cause significant performance debits which call for component redesign or post-processing to account for or remove the defects. For laser powder bed fusion (LPBF) processes, it has been shown that many of these features and their size and shape characteristics are controllable through LPBF process parameter manipulation. For design efforts, however, it is necessary to understand the direct influences of processing on the formation of porosity and the role that individual pores and porosity distributions have on the properties and performance of AM components. Additionally, design criteria must be established to facilitate implementation of …
Designing New Generations Of Bcc Lattice Structures And Developing Scaling Laws To Predict Compressive Mechanical Characteristics And Geometrical Parameters, Hasanain Abdulhadi
Designing New Generations Of Bcc Lattice Structures And Developing Scaling Laws To Predict Compressive Mechanical Characteristics And Geometrical Parameters, Hasanain Abdulhadi
Browse all Theses and Dissertations
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 …
Microstructural Characterization Of LensTm Ti-6al-4v: Investigating The Effects Of Process Variables Across Multiple Deposit Geometries, Laura Christine Davidson
Microstructural Characterization Of LensTm Ti-6al-4v: Investigating The Effects Of Process Variables Across Multiple Deposit Geometries, Laura Christine Davidson
Browse all Theses and Dissertations
Laser based additive manufacturing of Ti-6Al-4V components is under consideration for aerospace applications. The mechanical properties of the finished components depend on their microstructure. Process mapping compares process variables such as heat source power, heat source travel speed, material feed rate, part preheat temperature and feature geometry to process outcomes such as microstructure, melt pool geometry and residual stresses. In this work, the microstructure of two-dimensional pads, multilayer pads, thin walls, and structural components at the steady state location was observed. A method for measuring β grain widths that allows for the calculation of standard deviations, confidence intervals, and variances …
Low Velocity Impact And Rf Response Of 3d Printed Heterogeneous Structures, Sandeep Keerthi
Low Velocity Impact And Rf Response Of 3d Printed Heterogeneous Structures, Sandeep Keerthi
Browse all Theses and Dissertations
Three-dimensional (3D) printing, a form of Additive manufacturing (AM), is currently being explored to design materials or structures with required Electro-Mechanical-Physical properties. Microstrip patch antennas with a tunable radio-frequency (RF) response are a great candidate for 3D printing process. Due to the nature of extrusion based layered fabrication; the processed parts are of three-layer construction having inherent heterogeneity that affects structural and functional response. The purpose of this study is to identify the relationship between the anisotropy in dielectric properties of AM fabricated acrylonitrile butadiene styrene (ABS) substrates in the RF domain and resonant frequencies of associated patch antennas and …
Design And Testing Of Scalable 3d-Printed Cellular Structures Optimized For Energy Absorption, Sagar Dilip Sangle
Design And Testing Of Scalable 3d-Printed Cellular Structures Optimized For Energy Absorption, Sagar Dilip Sangle
Browse all Theses and Dissertations
Sandwich panel structures are widely used due to their high compressive and flexural stiffness and strength-to-weight ratios, good vibration damping, and low through-thickness thermal conductivity. These structures consist of solid face sheets and low-density cellular core structures that are often based upon honeycomb topologies. Interest in additive manufacturing (AM), popularly known as 3D printing (3DP), has rapidly grown in past few years. The 3DP method is a layer-by-layer approach for the fabrication of 3D objects. Hence, it is very easy to fabricate complex structures with complex internal features that cannot be manufactured by any other fabrication processes. Due to the …
Low-Velocity Impact Behavior Of Sandwich Panels With 3d Printed Polymer Core Structures, Andrew Joseph Turner
Low-Velocity Impact Behavior Of Sandwich Panels With 3d Printed Polymer Core Structures, Andrew Joseph Turner
Browse all Theses and Dissertations
Sandwich panel structures are widely used in aerospace, marine, and automotive applications because of their high flexural stiffness, strength-to-weight ratio, good vibration damping, and low through-thickness thermal conductivity. These structures consist of solid face sheets and low-density cellular core structures, which are often based upon honeycomb topologies. The recent progress of additive manufacturing (AM) (popularly known as 3D printing) processes has allowed lattice configurations to be designed with improved thermal-mechanical properties. The aim of this work is to design and print lattice truss structures (LTS) keeping in mind the flexible nature of AM. Several 3D printed core structures were created …
Resilience And Toughness Behavior Of 3d-Printed Polymer Lattice Structures: Testing And Modeling, Mohammed Al Rifaie
Resilience And Toughness Behavior Of 3d-Printed Polymer Lattice Structures: Testing And Modeling, Mohammed Al Rifaie
Browse all Theses and Dissertations
This research focuses on the energy absorption capability of additively manufactured or 3D printed polymer lattice structures of different configurations. The Body Centered Cubic (BCC) lattice structure is currently being investigated by researchers for energy absorption applications. For this thesis, the BCC structure is modified by adding vertical bars in different arrangements to create three additional configurations. Four designs or sets of the lattice structure are selected for comparison including BCC, BCC with vertical bars added to all nodes (BCCV), BCC with vertical bars added to alternate nodes (BCCA), and BCC with gradient arrangements of vertical bars (BCCG). Both experimental …
The Effect Of Laser Power And Scan Speed On Melt Pool Characteristics Of Pure Titanium And Ti-6al-4v Alloy For Selective Laser Melting, Chandrakanth Kusuma
The Effect Of Laser Power And Scan Speed On Melt Pool Characteristics Of Pure Titanium And Ti-6al-4v Alloy For Selective Laser Melting, Chandrakanth Kusuma
Browse all Theses and Dissertations
Selective Laser Melting (SLM) is an additive manufacturing (AM) technique that creates complex parts by selectively melting metal powder layer-by-layer. In SLM, the process parameters decide the quality of the fabricated component. In this study, single beads of commercially pure titanium (CP-Ti) and Ti-6Al-4V alloy are melted on a substrate of the same material as powder using an in-house built SLM machine. Multiple combinations of laser power and scan speed are used for single bead fabrication while the laser beam diameter and powder layer thickness are kept constant. This experimental study investigates the influence of laser power, scan speed and …
From 2d To 3d: On The Development Of Flexible And Conformal Li-Ion Batteries Via Additive Manufacturing, Aaron Joseph Blake
From 2d To 3d: On The Development Of Flexible And Conformal Li-Ion Batteries Via Additive Manufacturing, Aaron Joseph Blake
Browse all Theses and Dissertations
The future of electronic devices, such as smart skins, embedded electronics, and wearable applications, requires a disruptive innovation to the design of conventional batteries. This research was thus aimed at leveraging additive manufacturing as a means to invigorate the design of next-generation Li-ion batteries to meet the emerging requirements of flexible electronics. First, a state-of-the art approach for achieving flexible Li-ion batteries, using a robust, multi-walled carbon nanotube mat as current collector was demonstrated. A unique mechanical device was constructed to experimentally observe the correlation between mechanical fatigue and electrochemical stability. Points of failure in the conventional architecture were evaluated …
Feasibility Of Attaining Fully Equiaxed Microstructure Through Process Variable Control For Additive Manufacturing Of Ti-6al-4v, Sarah Louise Kuntz
Feasibility Of Attaining Fully Equiaxed Microstructure Through Process Variable Control For Additive Manufacturing Of Ti-6al-4v, Sarah Louise Kuntz
Browse all Theses and Dissertations
One of the greatest challenges in additive manufacturing is fabricating titanium structures with consistent and desirable microstructure. To date, fully columnar deposits have been achieved through direct control of process variables. However, the introduction of external factors appears necessary to achieve fully equiaxed grain morphology using existing commercial processes. This work introduces and employs an analytic model to relate process variables to solidification thermal conditions and expected beta grain morphology at the surface of and at the deepest point in the melt pool. The latter is required in order to ensure the deposited microstructure is maintained even after the deposition …
An Adapted Approach To Process Mapping Across Alloy Systems And Additive Manufacturing Processes, Luke Charles Sheridan
An Adapted Approach To Process Mapping Across Alloy Systems And Additive Manufacturing Processes, Luke Charles Sheridan
Browse all Theses and Dissertations
The continually growing market for metal components fabricated using additive manufacturing (AM) processes has called for a greater understanding of the effects of process variables on the melt pool geometry and microstructure in manufactured components for various alloy systems. Process Mapping is a general approach that traces the influence of process parameters to thermal behavior and feature development during AM processing. Previous work has focused mainly on Ti-6Al-4V (Ti64), but this work uses novel mathematical derivations and adapted process mapping methodologies to construct new geometric, thermal, and microstructural process maps for Ti64 and two nickel superalloy material systems. This work …
A Framework For Uncertainty Quantification In Microstructural Characterization With Application To Additive Manufacturing Of Ti-6al-4v, Gregory Thomas Loughnane
A Framework For Uncertainty Quantification In Microstructural Characterization With Application To Additive Manufacturing Of Ti-6al-4v, Gregory Thomas Loughnane
Browse all Theses and Dissertations
The sampling of three dimensional (3D) mesoscale microstructural data is typically prescribed using simple rules, likely resulting in data under- or oversampling depending on the measurement(s) of interest. The first part of this work investigates one approach for determining a minimally sufficient sampling scheme for 3D microstructural data, using computer-generated phantoms of polycrystalline grain microstructures. Sources of error that are observed experimentally are modeled using phantoms, in order to determine the effect that errors have on the microstructural statistic(s)-of-interest. Minimally-sufficient sampling schemes are then established based on a required accuracy in the microstructural statistic(s). The characterization error modeling framework is …