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Browsing Mechanical Engineering by Subject "3D printing"
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Item Open Access 3D Printing of Continuous Wire Polymer Composite for Mechanical and Thermal Applications(2019-07-02) Ibrahim, Yehia Elsayed Mahmoud; Kempers, RogerRecently, continuous fiber reinforcement has been combined with 3D printing techniques such as fused filament fabrication to create stronger and stiffer printed composite components. The continuous nature of the reinforcing material can improve both mechanical and thermal properties of the polymeric material significantly. However, several parameters can affect the printed composite properties such as filler volume fraction, type of polymer matrix and filler treatment. The work presented in this study addresses the effect of reinforcing polymers with continuous metal wire on the composites properties and the potential applications for these composites. In the first part of this study we presented a novel 3D printing technique in which metal wires were combined with polymer matrixes in order to improve both mechanical and thermal properties of the printed components. In the second part, we investigated the tensile and bending properties of the continuous wire polymer composites which was superior compared to the base polymer. In addition, we studied the effect of introducing continuous wires to the polymer matrix on the effective thermal conductivity which was found to increase significantly. In addition, we investigated the use of the fabricated composites as a novel fabrication technique for low-temperature heating elements and explored this technology for de-icing and anti-icing 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 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 Topology and Printing Orientation Optimization of Orthotropic Material for Additive Manufacturing(2021-11-15) Moter, Ahmed Elsayed Bayoumy Elsayed; Czekanski, AlexMechanical properties of 3d printed polymers have witnessed remarkable improvements as a result of optimization in topology and raster orientation. This study proposes and evaluates a strategy to deal with stiffness maximization of structures in elastic region subjected to global volume and compliance constraints. This work also presents a unique approach to dealing with local constraints, specifically stresses along and perpendicular to the fibers of the printed structures (principal material axes). A modified SIMP (modified solid isotropic material with penalization) method is used with the method of moving asymptotes (MMA) as the optimizer. A detailed description of the formulation and sensitivity analysis are discussed. 2D structures are then analyzed in the numerical examples section. The method can also be used for 3D structures, as the formulation derivation is general. Results show that this method is effective for producing manufacturable 3D printed structures that avoid stress concentrations.