Recently, with the expansion of application of polymer composite materials, high levels of deformation compensation actions have been developed. However, there is a problem of high-temperature viscoelasticity that occurs over time after completing the injection molding process. In this study, changes of mechanical properties of the Moldflow program for injection molding were analyzed to verify the viscoelasticity phenomenon through deformation analysis. In addition, deformation analysis of plastic injection molded products according to arrangement of three ribs was conducted and two products with different geometric shapes of the same function were compared. As a result, it was possible to reflect the viscoelastic effect by reducing the elastic modulus and shear modulus of the material. It was confirmed that the geometric shape with thick ribs formed in multiple longitudinal directions was mainly responsible. On the surface of the product where the rib arrangement was parallel and perpendicular to the flow direction, the orientation was orthogonal to the linear direction and the maximum residual stress was 81.17 MPa, which showed the largest value. It was judged that viscoelastic phenomena could be predicted and that an arrangement of parallel and perpendicular ribs that might intersect should be avoided.
The aim of this study is to numerically investigate the cooling performance of the electric vehicle motor depending on the attachment of the heat sink and materials to the cooling channel. The research focused on the numerical comparison of forced convective heat transfer coefficients with case 1 (Heat Sink-None, Cooling Channel-Al), case 2 (Heat Sink-None, Cooling Channel-Metal Hybrid Material), case 3 (Heat Sink-4EA, Cooling Channel-Al), and case 4 (Heat Sink-6EA, Cooling Channel-Al). To compare the cooling performance for novel design of the smart cooling system, selected local positions for various temperature distributions were marked on the coil surface. Normalized local Nusselt number of the cooling area at the normalized width position indicated that cooling performance of case 1 was on an average 8.05, 0.57, and 5.85% lower than that of cases 2, 3, and 4, respectively.
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Since most commercialized DLP 3D printers fabricate 3D structures by sinking materials to Vat using a bottom-up method, it is difficult to use various materials simultaneously and there are many restrictions on printing composite materials. Especially, composite resin mixed with various functional powders in photo curable resin generally has high viscosity, causing difficult material flow in the bottom-up method when using Vat. Additionally, most of the previously presented methods for fabricating multi-material structure use individual curing for each material, so the adhesion force at the contact surface is less than 50% compared to single material. Thus, in this paper, we propose a new type of DLP 3D printer that combines Material Extrusion and the DLP system. The proposed equipment can supply high viscosity composite material resins to a specific area to cure various materials simultaneously. This method will enable fabrication of multiple composite material structures with sufficient adhesion force. The tensile test will be performed to verify suitability of the proposed method.
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