Development of In-Mold Assembly Methods for Producing Mesoscale Revolute Joints

In-mold assembly is a promising process for producing articulated joints. It utilizes injection molding to automate assembly operations, which may otherwise require high labor times for production. Since injection molding is a high throughput process, in-mold assembly holds considerable promise in bulk production of assembled parts. However, current in-mold assembly methods cannot be used for manufacturing in-mold assembled products at the mesoscale. This is because the process changes considerably when the sizes of the molded parts are reduced. The premolded component in a mesoscale joint consists of miniature features. Hence, when a high temperature, high pressure polymer melt is injected on top of it, it is susceptible to plastic deformation. Due to presence of a mesoscale premolded component which is susceptible to deformation, traditional shrinkage models alone can not be used to characterize and control the clearances. This dissertation identifies and addresses issues pertaining to in-mold assembly of revolute joints at the mesoscale. First, this dissertation identifies defect modes which are unique to in-mold assembly at the mesoscale. Then it develops mold design templates which can be used for manufacturing in-mold assembled mesoscale revolute joints. Further, issues related to the deformation of the mesoscale premolded component are identified. Two novel mold design solutions to realize mesoscale in-mold assembled revolute joints are presented. The first involves use of mold inserts to constrain the premolded component to inhibit its deformation. The second involves use of a bi-directional flow of the polymer melt over the premolded component to balance the deforming forces experienced by it. Finally, methods to predict and control clearances that would be obtained in mesoscale in-mold assembled revolute joints are presented. To demonstrate the utility of the tools built as part of this research effort, a case study of a miniature robotic application built using mesoscale in-mold assembly methods is presented. This dissertation provides a new approach for manufacturing mesoscale assemblies which can lead to reduction in product cost and create several new product possibilities

Simulation-Based Design of Drive Mechanism for Flapping Wing Miniature Air Vehicles

Flapping wing miniature air vehicles (MAVs) have significant potential in surveillance, search, rescue and reconnaissance applications. These applications require the MAV to carry payloads in the form of batteries, on-board cameras, camera, sensors etc. In order to ensure that the payload capacity of the MAV is maximized for a given wing area and flapping frequency, we need to carefully design the drive mechanism to reduce its mass and ensure that it meets the intended functional requirements. The overall design approach described in this chapter incorporates the advances in modeling and simulations methods in kinematic and dynamic analysis, finite element analysis, and manufacturability analysis. We demonstrate applicability this design approach using two case studies

Investigation on the Luminescence Properties of InMO4 (M = V5+, Nb5+, Ta5+) Crystals Doped with Tb3+ or Yb3+ Rare Earths Ions

[EN] We explore the potential of Tb- and Yb-doped InVO4, InTaO4, and InNbO4 for applications as phosphors for light-emitting sources. Doping below 0.2% barely change the crystal structure and Raman spectrum but provide optical excitation and emission properties in the visible and near-infrared (NIR) spectral regions. From optical measurements, the energy of the first/second direct band gaps was determined to be 3.7/4.1 eV in InVO4, 4.7/5.3 in InNbO4, and 5.6/6.1 eV in InTaO4. In the last two cases, these band gaps are larger than the fundamental band gap (being indirect gap materials), while for InVO4, a direct band gap semiconductor, the fundamental band gap is at 3.7 eV. As a consequence, this material shows a strong self-activated photoluminescence centered at 2.2 eV. The other two materials have a weak self-activated signal at 2.2 and 2.9 eV. We provide an explanation for the origin of these signals taking into account the analysis of the polyhedral coordination around the pentavalent cations (V, Nb, and Ta). Finally, the characteristic green (D-5(4) -> F-7(J)) and NIR (F-2(5/2) -> F-2(7/2)) emissions of Tb3+ and Yb3+ have been analyzed and explained.The authors thank the financial support from the Spanish Ministerio de Ciencia, Innovacion y Universidades, Spanish ́ Research Agency (AEI), Generalitat Valenciana, and European Fund for Regional Development (ERDF, FEDER) under grants no. MAT2016-75586-C4-1/2-P, RTI2018-101020-BI00, RED2018-102612-T (MALTA Consolier Team), and Prometeo/2018/123 (EFIMAT). P.B. acknowledges financial support from the Kempe Foundation and the Knut & Alice Wallenberg Foundation via a doctoral studentship. A.B.G. thanks the support provided by Universitat de Valencia to perform a research stay (Atraccióde Talent, VLC-CAMPUS)Botella, P.; Enrichi, F.; Vomiero, A.; Muñoz-Santiuste, JE.; Garg, AB.; Arvind, A.; Manjón, F.... (2020). Investigation on the Luminescence Properties of InMO4 (M = V5+, Nb5+, Ta5+) Crystals Doped with Tb3+ or Yb3+ Rare Earths Ions. ACS Omega. 5(5):2148-2158. https://doi.org/10.1021/acsomega.9b02862S214821585

A Comparative Overview of Glass-Ceramic Characterization by MAS-NMR and XRD

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