June 18, 2006
June 18, 2006
June 21, 2006
11.414.1 - 11.414.6
Design, Build and Test in Support of Computer Aided Design Introduction
A senior level project requiring the design, fabrication and testing of an idealized lift hook is discussed. The primary objective of the project is to address the issue of solution accuracy1 and its importance in computer aided design (CAD). Secondary objectives of the project are to reinforce the CAD process, introduce the computer numerically controlled (CNC) machining process, and to provide some of the tools and skill helpful to students during their senior capstone design projects.
The primary CAD tools used in the completion of the project are solid modeling and the finite element method (FEM). Critical to the successful application of the FEM, under all circumstances, is the generation of an accurate solution. As defined here accuracy requires the construction of a proper finite element model (e.g. finite element, restraints, loads, etc…), as well as a numerically robust solution. Accuracy must answer two questions:
• Is the computational model sufficiently accurate2? • Is the numerical solution sufficiently accurate3,4?
While it is difficult to determine firm answers to these questions it is important that they are asked. The lift hook project being discussed and its design, build, and test format is constructed to raise awareness of these issues.
The lift hook design project is part of the first course in a two course capstone design sequence in mechanical engineering at the United States Naval Academy. The first semester course is structured to have two hours of lecture and two hours of laboratory per week. Course credit is split evenly between computer aided design content (CAD) and the capstone design project.
The CAD portion of the course is project driven covering topics in solid modeling, drafting, finite element analysis, assembly modeling and rapid prototyping. Approximately a third of this time is spent on design projects using finite element analysis. The specific analyses required include rods and beams, frames, linear elastic solids and heat transfer. The last three projects are team assignments. The finite element lecture content has changed from year to year ranging from a miniature finite element course to a just-in-time delivery model. The lecture topics and course materials of relevance to this project included the basic element stiffness approach for rods and trusses, plane stress rectangular finite elements and formal and heuristic approaches to determine solution accuracy and convergence.
While all of the finite element projects in the course contain an element of design, build and test the most well developed project, and the one discussed here, concerns the linear elastic behavior of a lift hook. The project requires the design of a lift hook with the greatest stiffness
Burkhardt, J. (2006, June), Design, Build And Test In Support Of Computer Aided Design Paper presented at 2006 Annual Conference & Exposition, Chicago, Illinois. 10.18260/1-2--851
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