Engineering Commons^™

A Convolutional Neural Network (Cnn) For Defect Detection Of Additively Manufactured Parts, Musarrat Farzana Rahman

Masters Theses

“Additive manufacturing (AM) is a layer-by-layer deposition process to fabricate parts with complex geometries. The formation of defects within AM components is a major concern for critical structural and cyclic loading applications. Understanding the mechanisms of defect formation and identifying the defects play an important role in improving the product lifecycle. The convolutional neural network (CNN) has been demonstrated to be an effective deep learning tool for automated detection of defects for both conventional and AM processes. A network with optimized parameters including proper data processing and sampling can improve the performance of the architecture. In this study, for the …

Fabrication Of Silicon Nitride Parts By Ceramic On-Demand Extrusion Process, Sachin Choudhary

Masters Theses

“Ceramic On-Demand Extrusion (CODE) is a patented solid freeform fabrication method for manufacturing high-density monolithic ceramic parts. In the past 5-6 years, the technology has been successfully implemented to fabricate alumina and zirconia parts. The mechanical characterizations also show CODE’s high potential in achieving desired structural properties. The present study covers the fabrication of silicon nitride parts by CODE process, which entailed the design of paste formulation for achieving rheology suitable for dimensional control in fabricated parts and determining firing temperature and the content of sintering additives for silicon nitride green bodies fabricated by CODE. The density, hardness, and fracture …

Additive Manufacturing Of Linear Shaped Charges To Address Run Up And Run Down Phenomena, Jason Ho

Masters Theses

”A shaped charge is an explosive device used to focus detonation energy in a desired direction. Additive Manufacturing (AM) can allow greater design freedom and geometric complexity for the liner portion of the shaped charge.

In this work, the following hypotheses were tested: 1) Adjusting the initial apex angle of a linear shaped charge liner reduces the amount of run up that occurs, and 2) implementing a backstop at the end of a linear shaped charge liner reduces the amount of run down that occurs.

Linear shaped charge liners with a continuously changing apex angle were created with additive manufacturing. …

In-Situ X-Ray Imaging Of The Selective Laser Melting Process, Meelap M. Coday

Masters Theses

"Fusion-based metal additive manufacturing (AM) has garnered much interest in recent decades. Despite the popularity of fusion-based AM technologies such as selective laser melting (SLM), there are still fundamental questions and uncertainties that need to be addressed. In this work, we focus on the understanding of the undercooling in the SLM process and the uncertainties induced by the laser beam size, power, and scan speed. First, we report the estimation of undercooling in the SLM process from the solidification rate measured by in-situ high-speed synchrotron x-ray imaging, based on the dendrite growth velocity model. The undercooling changes as a function …

Combining Laser Aided Ablation And Polishing To Minimize Surface Roughness Of Additively Manufactured Aluminium Components, Sahil Bipinkumar Patel

Masters Theses

“The surface roughness of additively manufactured parts is much higher than the acceptable range for most applications, thus post-processing is needed to qualify these parts for use. Laser polishing can be used to bring the surface roughness in an admissible range, but if the initial roughness is very high then the energy density for the polishing process needs to be very high to achieve a significant reduction in roughness. This high energy density can produce many process defects. Also, laser polishing alone cannot get rid of high wavelength asperities. Any waviness in the part can be linked with initial waviness …

The Effect Of Cell Size And Surface Roughness On The Compressive Properties Of Abs Lattice Structures Fabricated By Fused Deposition Modeling, Leah Hope Mason

Masters Theses

"Postprocessing is an important step in many manufacturing methods, but it is especially important for additive manufacturing. Researchers looking to improve the surface roughness of acrylonitrile butadiene styrene (ABS) parts fabricated by fused deposition modeling (FDM) have determined that acetone smoothing not only achieves improved surface roughness but increases compressive strength as well. This could be very beneficial to lattice structures, which are known for already having an excellent strength to weight ratio. If the compressive strength of ABS lattice structures could be improved even further using acetone smoothing, it could expand the applications for plastic lattice structures and improve …

Development Of Test Methods For Characterizing Extrudability Of Cement-Based Materials For Use In 3d Printing, Jonathan Thomas Kuchem

Masters Theses

"3D printing is the process of creating three-dimensional objects using an automated additive manufacturing process. The 3D printing process has been used with materials such as metals and polymers, but application with cement based materials for the construction industry has yet to be developed. In this research, two main problems were investigated for printing cement based composite materials: extrudability and tensile reinforcement. Fiber-reinforced concrete (FRC) was studied as an internal reinforcing system to increase tensile/flexural strength. First, FRC was studied to investigate mechanical properties and use of fibers from waste tires as an environmentally friendly option. A reference mixture with …

Effect Of Sparse-Build Internal Structure On Performance Of Fused Deposition Modeling Parts, Shixuan Meng

Masters Theses

"Fused deposition modeling (FDM) technology has been used in additive manufacturing for years and is able to significantly reduce both manufacturing time and cost for production tooling and end-use parts. Autoclave molding is one of the conventional tools used to produce composite parts. In autoclave molding, the soft composite material is positioned on the molding tool, and then subjected to vacuum and elevated temperatures to facilitate the curing of the resin. With additive manufacturing (AM), it is possible to fabricate the molding tool with a sparse internal structure, thereby reducing the fabrication time and cost compared to a solid tool. …

Thermographic Investigation Of Laser Metal Deposition, Sreekar Karnati

Masters Theses

"Laser metal deposition as an additive manufacturing technique has been proven to possess the capability for fabricating complex, intricate geometries and excellent material properties through material deposition. Accurate manufacture of such geometric features would require precise control over the material deposition process. The need of the hour are process monitoring and analyses mechanisms that are crucial in ascertaining the occurrence of the intended actions during deposition while also serving as effective learning tools. The current work involved developing and incorporating an Infra-Red (IR) camera as a process monitoring tool for laser metal deposition. Using the IR camera the thermal dynamics …

An Experimental Study Of Fabrication Temperature Effect On Aqueous Extrusion Freeform Fabrication, Jie Li

Masters Theses

"In order to understand the effect of fabrication temperature, a computer controlled 3-D gantry system was used to extrude aqueous alumina paste using Extrusion Freeform Fabrication. The system includes a temperature control subsystem that allows for fabrication of components below the paste's freezing temperature in the range of -10⁰C to -30⁰C and a hot plate with temperature in the range of 20⁰C to 80⁰C inside a room temperature chamber. Comparisons in terms of relative density, mechanical properties, part accuracy and minimum deposition angle were performed by Extrusion Freeform Fabrication at 40⁰C plate temperature inside a room temperature chamber and at …