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Full-Text Articles in Engineering
A Convolutional Neural Network (Cnn) For Defect Detection Of Additively Manufactured Parts, Musarrat Farzana Rahman
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 …
Characterization Of High Cycle Fatigue And Laser-Aided Machining And Polishing Of Additively Manufactured Materials, Mohammad Masud Parvez
Characterization Of High Cycle Fatigue And Laser-Aided Machining And Polishing Of Additively Manufactured Materials, Mohammad Masud Parvez
Doctoral Dissertations
“Additive manufacturing (AM) and laser-aided machining and polishing (LAMP) of materials are emerging manufacturing processes both for research and industrial sectors. The AM process can manufacture near-net-shape parts with complex geometries. Meanwhile, the LAMP process integrated with an AM system offers a high processing rate, minimum heat-affected zone, and easily adjustable process parameters during machining and polishing. In mechanical properties characterization of AM metals and alloys, fatigue is a vitally important test method to understand the behavior of materials in cycling loading and unloading circumstances since most mechanical failures of structures are due to fatigue. To characterize AM metal fatigue …
Fabrication, Characterization Of High-Entropy Alloys And Deep Learning-Based Inspection In Metal Additive Manufacturing, Wenyuan Cui
Doctoral Dissertations
"Alloying has been used to confer desirable properties to materials. It typically involves the addition of small amounts of secondary elements to a primary element. In the past decade, however, a new alloying strategy that involves the combination of multiple principal elements in high concentrations to create new materials called high- entropy alloys (HEAs) has been in vogue. In the first part, the investigation focused on the fabrication process and property assessment of the additive manufactured HEA to broaden its engineering applications. Additive manufacturing (AM) is based on manufacturing philosophy through the layer-by-layer method and accomplish the near net-shaped components …
Fabrication Of Silicon Nitride Parts By Ceramic On-Demand Extrusion Process, Sachin Choudhary
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 …
Additively Manufactured Metallic Cellular Structures, Okanmisope Aziel Fashanu
Additively Manufactured Metallic Cellular Structures, Okanmisope Aziel Fashanu
Doctoral Dissertations
"Cellular structures are lightweight structures with excellent mechanical, thermal, and acoustic properties. They offer promise in a series of applications, including lightweight applications, sandwich cores, mechanical damping, acoustic absorption, strain isolation, and thermal management. The manufacturing of these complex cellular structures is expensive and time-consuming, which hinders the adoption of these structures in many industries. Advancement in manufacturing technologies, such as additive manufacturing (AM), however, have changed this. AM allows for the rapid and less expensive manufacturing of complex cellular structures. This work aimed to investigate the performance of additively manufactured cellular structures for lightweight and sandwich core applications. In …
Layer-To-Layer Feedback Control For Direct Energy Deposition Additive Manufacturing, Michelle Gegel
Layer-To-Layer Feedback Control For Direct Energy Deposition Additive Manufacturing, Michelle Gegel
Doctoral Dissertations
"Additive manufacturing (AM) has garnered much attention in recent years, some calling it the fourth industrial revolution. It was first used to create rapid prototypes, although recent efforts have been made to advance the technology towards production of functional parts. This requires advancement in the materials used in AM, as well as the ability to produce quality parts repeatably. More specifically, direct energy deposition (DED) of metal powders is a process capable of producing and repairing parts with complex geometries; however, it is not widely used in industry due to challenges with quality control. In this process, metal powder is …
In-Situ X-Ray Imaging Of The Selective Laser Melting Process, Meelap M. Coday
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
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 …
Fabrication And Characterization Of Multifunctional Composites, Aditya R. Thakur
Fabrication And Characterization Of Multifunctional Composites, Aditya R. Thakur
Doctoral Dissertations
“This study details the research to facilitate fabrication and characterization of novel structural composites reinforced with carbon fibers. Across industries, materials with high performance-to-weight ratio are sought after. Using carbon fibers as secondary phases in these proposed composites, specific characteristics can be tailored in these materials to manufacture strong, lightweight, high performance structures. The first part of the research focused on the improvement in the mechanical properties of the composites using carbon fiber reinforcement. As a part of this study, toughened ceramic composites with predictable failure patterns were produced using carbon fiber inclusions. A closed-form analytical model was developed to …
The Effect Of Cell Size And Surface Roughness On The Compressive Properties Of Abs Lattice Structures Fabricated By Fused Deposition Modeling, Leah Hope Mason
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 …
Design, Fabrication, And Characterization Of Functionally Graded Materials, Sreekar Karnati
Design, Fabrication, And Characterization Of Functionally Graded Materials, Sreekar Karnati
Doctoral Dissertations
“The aim of this research was to investigate the feasibility of fabricating custom designed, graded materials using Laser Metal Deposition (LMD) that will cater for functionality and unconventional repair. The ultimate goal of the project is to establish the versatility of LMD for fabricating advanced materials and tackling problems that have been conventionally difficult or in cases infeasible. In order to accomplish these goals, this research involved investigations into, the feasibility of using elemental powders as modular feedstocks, the feasibility of fabricating tailored gradients with these custom compositions, and finally leveraging the advantages of grading materials using LMD to successfully …
Remanufacturing Of Precision Metal Components Using Additive Manufacturing Technology, Xinchang Zhang
Remanufacturing Of Precision Metal Components Using Additive Manufacturing Technology, Xinchang Zhang
Doctoral Dissertations
"Critical metallic components such as jet engine turbine blades and casting die/mold may be damaged after servicing for a period at harsh working environments such as elevated temperature and pressure, impact with foreign objects, wear, corrosion, and fatigue. Additive manufacturing has a promising application for the refurbishment of such high-costly parts by depositing materials at the damaged zone to restore the nominal geometry. However, several issues such as pre-processing of worn parts to assure the repairability, reconstructing the repair volume to generate a repair tool path for material deposition, and inspection of repaired parts are challenging. The current research aims …
Freeform Extrusion Fabrication Of Advanced Ceramics And Ceramic-Based Composites, Wenbin Li
Freeform Extrusion Fabrication Of Advanced Ceramics And Ceramic-Based Composites, Wenbin Li
Doctoral Dissertations
"Ceramic On-Demand Extrusion (CODE) is a recently developed freeform extrusion fabrication process for producing dense ceramic components from single and multiple constituents. In this process, aqueous paste of ceramic particles with a very low binder content ( < 1 vol%) is extruded through a moving nozzle to print each layer sequentially. Once one layer is printed, it is surrounded by oil to prevent undesirable water evaporation from the perimeters of the part. The oil level is regulated just below the topmost layer of the part being fabricated. Infrared radiation is then applied to uniformly and partially dry the top layer so that the yield stress of the paste increases to avoid part deformation. By repeating the above steps, the part is printed in a layer-wise fashion, followed by post-processing. Paste extrusion precision of different extrusion mechanisms was compared and analyzed, with an auger extruder determined to be the most suitable paste extruder for the CODE system. A novel fabrication system was developed based on a motion gantry, auger extruders, and peripheral devices. Sample specimens were then produced from 3 mol% yttria stabilized zirconia using this fabrication system, and their properties, including density, flexural strength, Young's modulus, Weibull modulus, fracture toughness, and hardness were measured. The results indicated that superior mechanical properties were achieved by the CODE process among all the additive manufacturing processes. Further development was made on the CODE process to fabricate ceramic components that have external/internal features such as overhangs by using fugitive support material. Finally, ceramic composites with functionally graded materials (FGMs) were fabricated by the CODE process using a dynamic mixing device"--Abstract, page iv.
Repair Of Metallic Components Using Hybrid Manufacturing, Renwei Liu
Repair Of Metallic Components Using Hybrid Manufacturing, Renwei Liu
Doctoral Dissertations
"Many high-performance metal parts users extend the service of these damaged parts by employing repair technology. Hybrid manufacturing, which includes additive manufacturing (AM) and subtractive manufacturing, provides greater build capability, better accuracy, and surface finish for component repair. However, most repair processes still rely on manual operations, which are not satisfactory in terms of time, cost, reliability, and accuracy. This dissertation aims to improve the application of hybrid manufacturing for repairing metallic components by addressing the following three research topics. The first research topic is to investigate and develop an efficient best-fit and shape adaption algorithm for automating 3D models' …
Effect Of Sparse-Build Internal Structure On Performance Of Fused Deposition Modeling Parts, Shixuan Meng
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. …
Hierarchical Control Of Complex Manufacturing Processes, Hesam Zomorodi Moghadam
Hierarchical Control Of Complex Manufacturing Processes, Hesam Zomorodi Moghadam
Doctoral Dissertations
"The need for changing the control objective during the process has been reported in many systems in manufacturing, robotics, etc. However, not many works have been devoted to systematically investigating the proper strategies for these types of problems. In this dissertation, two approaches to such problems have been suggested for fast varying systems. The first approach, addresses problems where some of the objectives are statically related to the states of the systems. Hierarchical Optimal Control was proposed to simplify the nonlinearity caused by adding the statically related objectives into control problem. The proposed method was implemented for contour-position control of …
Thermographic Investigation Of Laser Metal Deposition, Sreekar Karnati
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
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 …