Mechanical Engineering
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Browsing Mechanical Engineering by Subject "Additive manufacturing"
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Item Open Access 3D Printed Smart Materials of Continuous Wire Polymer Composites for Sensing Applications(2023-03-28) Elsayed, Mennatullah Mohamed Adel Saleh; Melenka, Garrett; Kempers, RogerSmart material with sensing capability is an exciting new technology that will impact many applications, including structural health monitoring, biomedical implants, wearable sensors, and actuators. Internal damage in polymer composites is usually hard to predict, and they need to be continuously monitored for any sign of internal damage for safety issues and to increase the life cycle. In this study, continuous wire polymer composites (CWPCs) were 3D-printed using the fused filament fabrication (FFF) technique to produce functional smart materials with different sensing capabilities like strain and thermal sensing. Here, the integrated wire within the conductive polymer composite structure acts as a sensing element. For strain sensing characterization, different design parameters such as matrix type, wire type, and loading condition were investigated to study the effect of these parameters on the efficacy of the CWPC sensor. The different matrices used have different mechanical properties representing rigid (polylactic acid) and flexible (thermoplastic polyurethane) structures to widen the range of applications of CWPCs as strain sensors. The change of the electrical resistance of the integrated wire within the CWPCs was measured under tensile loading and plotted against the applied strain. The results of this electromechanical testing demonstrate the ability of CWPCs to be used as strain sensor for either rigid or flexible structures. To check the reliability and reversibility of CWPCs structure as strain sensor, the electromechanical behaviour was investigated under fatigue/cyclic loading. The results of this work demonstrate the reverse piezoresistance behaviour of the CWPC sensor. From thermal sensing standpoint, different design parameters like wire type, matrix type, and sensor thickness were studied to investigate the application of CWPCs as temperature and heat flux sensors which can be readily designed and adapted to suit unique and bespoke thermal applications. The change of the electrical resistance of the integrated wires was correlated to the applied temperature to measure the heat conducted through a surface. A prototype of a real-world application was designed for the heat flux measurements using CWPC sensor. Generally, this study demonstrates the applicability of FFF technique to print sensors with continuous integrated wire with tuneable properties for different sensing applications.Item Open Access Characterization and Impact of Thermal Conductivity of Stainless Steel 316L Employed in Additive Manufacturing(2021-03-08) Rojas Dorantes, Carlos Abel; Czekanski, AlexThe main objective of this research was to develop new methods to improve the mechanical properties of 3D printed metal parts by controlling the heat transfer mechanisms involved in the melting and solidification of powder particles. A number of experiments were carried out to study the parameters involved in the process. The first part of the work was dedicated to the measurement of effective thermal conductivity in 316L stainless-steel powder. The results showed that controlled samples had important increments in thermal conductivity. The experimental setup was based on a steady-state analysis, designed to safely expose the sample up to 1000 C. The best result was obtained from the 10% compacted sample, whose thermal conductivity was double that of the reference sample. In the second part of this work, simulations were performed of a laser track over a powder bed. The results obtained from the thermal conductivity experiments were compared with those from analytical models. The thermal behaviour of the powder displayed an important decrement in temperature gradients. Moreover, analysis of subsequent laser tracks showed important improvements under low energy density. In summary, the theorical findings of this work can help to reduce and control defects formed in the melting and solidification stages of the manufacturing process by limiting temperature gradients and improving thermal distribution.Item Open Access Characterization of Heat Exchange for Additively Manufactured Components(2022-08-08) Elkholy, Ahmed Moustafa Sayed; Kempers, RogerThe current work aims to develop a fundamental understanding of thermal transport mechanisms within and on AM components and structures, which is addressed through three specific objectives. The first objective is to characterize the effect of the process parameters, of FFF and SLM, on the effective thermal conductivity of AM components. Secondly, to improve the pool boiling heat transfer coefficient (HTC) using AM-based structures. Finally, to investigate the application of SLM 3D-printed evaporators in a two-phase loop thermosyphon. To achieve the first objective, a high-accuracy steady-state guarded method was developed to measure the effective conductivity of AM components. First, this apparatus was employed to measure the thermal conductivity of several PLA polymer composites, either metal or carbon fiber. The experimental results showed that all samples featured high anisotropy in thermal conductivity, reaching up to 2 in the carbon fiber composite. Thereafter, the apparatus was modified to quantify the effect of the SLM process parameters, such as the laser power, hatch spacing, etc., on the effective thermal conductivity of AlSi10Mg, which were found to significantly decrease the resulting thermal conductivity up to 22%. With respect to the second objective, an FFF-based polymer fixture was proposed to enhance the pool boiling characteristics from copper surfaces. Due to the low conductivity of the fixture, it could create a spatial temperature distribution at the boiling surface, initiating the bubbles earlier and enhancing the HTC. A high-precision pool boiling apparatus was then built, addressing most of the experimentation issues found in the literature, such as repeatability, surface aging, and the heater's small size. This device was subsequently used to examine novel 3D re-entrant cavities fabricated using SLM on the pool boiling performance. It was observed that the surface with re-entrant cavities increased the nucleation site density and the bubble departure frequency, enhancing the HTC 2.8 times compared to the plain 3D-printed surface. The last objective was achieved by investigating the difference in the thermal performance of closed-loop thermosyphon between two surfaces: machined and additively manufactured via SLM. It was shown that the 3D-evaporator slightly increased the loop thermal resistance; however, it mitigated the temperature instabilities.Item Open Access Development of Characterization of 3D-Printed Continuous Pitch Carbon Fiber Composites(2023-12-08) Olcun, Sinan; Kempers, RogerThis study looks at the development of 3D printing technologies for the purpose of creating thermally conductive composites using continuous pitch carbon fiber and how various printing parameters affect thermal conductivity of samples. An initial prototype 3D printer was made with a custom dual nozzle extruder to print pitch carbon fibers, initial samples were measured with 37.1 W/mK effective thermal conductivity, this was much lower than what was expected of the samples. Imaging and µCT scanning confirmed fibers were breaking at some point in the process. A heat flow meter in a vacuum chamber was designed and fabricated to measure thermal conductivity of individual tows of carbon fibers to characterize breakage. The printing parameters affecting breakage were diagnosed and it as found that the angle between the nozzle and the printing bed had the greatest impact on breakage after a new printing system was developed using a 6-axis robot arm.Item Open Access Material Characterization and Development of Simulant Phantoms for a Biofidelic Head Model(2024-11-07) Tenio, Tristan Virgilio; Boakye-Yiadom, SolomonTraumatic Brain Injury (TBI) is a global health crisis, with concussions — classified as mild TBI — being particularly common in sports and daily activities. These non-penetrative injuries complicate diagnosis and analysis due to ethical and observational challenges. This thesis aims to develop a biofidelic head model for lab-based impact testing, bridging the gap of anatomical representation between computational models and physical validation. This research focuses on characterizing materials that mimic the mechanical properties of human brain and skull tissues under impact conditions. These materials are tested for their ability to simulate the brain’s compressive and shear responses and the skull’s flexural strength, using advanced manufacturing techniques. The research, structured across five chapters, reviews existing head impact methods and current practices for simulant characterization, selects and tests brain and skull simulants, and designs a comprehensive methodology for creating a full-scale biofidelic head model, proposing advancements for more accurate TBI analysis and prevention.Item Open Access Multiscale Material Modeling of Additively Manufactured Composite Laminates(2019-11-22) Somireddy, Madhukar; Czekanski, AlexAdditive manufacturing (AM) technology has revolutionized the production of structural parts for many industries. AM methods enable freedom in design of a part and furthermore, make it easier to fabricate a part with tailored microstructure to yield desired mechanical properties. Despite many other benefits, anisotropy in the material properties of 3D printed parts remains of primary concern. Anisotropy is introduced into parts during the printing process. This calls for the need to investigate the material behaviour of printed parts at different scales to enable the effective design and analysis of models for 3D printing. The present work therefore focuses on addressing the material behaviour of 3D printed parts via fused filament fabrication (FFF), a material extrusion AM process. Four aspects of the problem are accordingly examined. First, the material behaviour of printed parts with different materials is assessed by conducting mechanical testing. Second, the mechanical behaviour of printed parts is characterized using laminate mechanics. Furthermore, the microstructure of printed parts is characterized, and its influence on the final properties is investigated. Third, computational micromechanical models are employed to estimate the final material properties of printed parts based on the underlying mesostructure. Finally, the computational models are employed to perform damage analysis of printed parts. The research work revealed that the final material behavior of printed parts was governed by their mesostructure, which was produced during 3D printing process. The behavior of printed parts resembled that of traditional laminates and therefore, the laminate mechanics can be employed in preliminary design and analysis. Computational models predicted accurate final properties of parts by considering their mesostructure, and also their nonlinear behavior under loads. The computational damage model that employed bulk material properties provided ideal material behavior and the other damage model that used results of unidirectional laminates provided actual material behavior of printed parts. In summary, this work presents a processstructureproperty relationship for 3D printed parts, and also outlines the mechanics of the material to characterize the mechanical behaviour of the printed parts. Finally, computational models are developed for the effective design and analysis of models for 3D printing.Item Open Access The Effect of the Heat Treatment on Microstructural Evolution and Mechanical Properties of 3D Printed Medical Grade Ti6AL4V(2020-05-11) Azgomi, Niyousha; Boakye-Yiadom, SolomonThe merger of metal 3D printing with a simple post-processing treatment to fabricate parts using Ti6Al4V medical-grade titanium alloy would prove very desirable for most biomedical applications. In this study, the effect of post-processing heat treatment on the microstructure and properties of 3D printed and conventionally manufactured Ti6Al4V medical-grade titanium alloy was investigated to determine the performance of the as printed and heat-treated parts. In general, heat treatment led to the growth of distinct continuous and discontinuous lath structures along prior grain boundaries as well as basketweave lath and V-shaped structures within the prior- grains. V-shaped and spherical structures were specific to 3D printed and conventional samples, respectively. Also, regarding the mechanical properties, 3D printed samples had better wear resistance as well as higher hardness compared to the conventional samples due to the presence of V-shaped structures.Item Open Access Thermal Fe Analysis of Powder Bed Fusion Process: Power Input Evaluation and Parameter Sensitivity(2018-11-21) Moraes, Diego Augusto De; Czekanski, AlexWe investigated the thermal behavior of the powder bed fusion (PBF) manufacturing process. Specifically, a finite element thermal analysis procedure was developed to simulate selective laser melting, one of several PBF processes available on the market. The primary objective was to study how selected parameters of the PBF process affect temperature distributions, since a high temperature gradient and cooling rate are associated with residual stress and deformation in the built part. Since it was difficult to devise an analytical solution for this transient thermal problem, commercially available finite element analysis software, Abaqus, was employed. Sensitivity analysis was undertaken to analyze the impact of powder diameter, packing density, and substrate temperature on the overall temperature distributions. Finally, verification and validation were performed via experimental setup and data from the literature. The samples built were characterized by residual stress measurements, porosity, and relative density to further validate the model.