Effort flow analysis: a methodology for directed product evolution using rigid body and compliant mechanisms
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This dissertation presents a systematic design methodology for directed product evolution that uses both rigid body and compliant mechanisms to facilitate component combination in the domain of mechanical products. The methodology, known as effort flow analysis, is based on fundamental tenets from the Theory of Mechanics, and Graph Theory. Effort flow analysis uses a semantic network known as an effort flow diagram to model a product as a connected set of nodes and links. The nodes represent the components of the product and the links represent the interfaces between the components. The effort flow diagram is a quasi-static model of the flow of effort (force or torque in the mechanical domain) as it transits the body from input to output. In order to capture the effect of the relative motion that occurs at the interfaces, a basis set for relative motion is developed for effort flow analysis. The basis consists of 4 possible link type cases, (1) No relative motion at the interface or away from the interface, (2) Component relative motion that occurs away from the interface, (3) general Relative motion between components, and (4) Interface relative motion that occurs only at the interface. These are known as NLinks, C-Links, R-Links, and I-Links respectively. Rigid body combinations are sought for components connected by N-Links and compliant mechanism combinations are sought for components connected by the other link types. Component combination opportunities are sought based on the connection structure of the effort flow diagram. Guidance for component combination is captured in a set of 29 product-evolution guidelines that are derived from the results of an empirical study. In addition, an example solution is cataloged for each of the guidelines to foster design-by-analogy efforts by the designer. Finally, the work presents a novel design and prototype for a compliant one-piece umbrella frame, which serves as a proof of concept for the methodology. Possible future pursuits are presented in the areas of knowledge capture using guidelines and solution examples. In addition, the possibility of a function-to-component matrix for automated concept generation is considered.