A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Manufacturability Analysis of Thermally-Enhanced Polymer Composite Heat Exchangers(2011) Hall, Timothy; Gupta, Satyandra K; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Thermally-enhanced polymer composite heat exchangers are an attractive alternative for applications such as the use of seawater as a cooling medium and other corrosive environments that traditionally use expensive exotic metallic alloys, but a number of manufacturing challenges exist. The goal of this thesis is to develop an understanding of the manufacturing feasibility, in particular mold filling and fiber orientation, of utilizing thermally-enhanced polymer composites and injection molding to manufacture polymer heat exchangers. To best predict mold filling feasibility, this thesis proposes developing an explicit construction of the boundary, represented as a surface based on the parameter space, which separates the feasible and infeasible design space. The feasibility boundary for injection molding in terms of the design parameters is quite complex due to the highly nonlinear process physics, which, consequently, makes molding simulation computationally intensive and time consuming. This thesis presents a new approach for the explicit construction of a moldability-based feasibility boundary based on intelligent Design of Experiments and adaptive control techniques to minimize the number or computation experiments needed to build an accurate model of the feasibility boundary. Additionally, to improve the flexibility of the mold filling prediction framework to changes in overall heat exchanger design, a model simplification approach is presented to predict mold filling for general finned-plate designs by determining an equivalent flat plate representation and utilizing a developed flat plate mold filling metamodel to estimate mold filling. Finally, a fiber orientation measurement methodology is presented for experimentally determining fiber orientation behavior for sample heat exchanger geometries that develops both a local and global understanding of the fiber orientation behavior and compares thesis findings to simulation predictions. The work presented in this thesis significantly advances the understanding of manufacturability considerations for utilizing thermally-enhanced polymer composites in heat exchanger applications and is useful in design exploration, optimization, and decision-making approaches.Item Development of In-Mold Assembly Methods for Producing Mesoscale Revolute Joints(2009) Ananthanarayanan, Arvind; Gupta, Satyandra K; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)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.