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Unformatted text preview: PROOF COPY 114204JTQ P R O O F C O P Y 1 1 4 2 4 J T Q D. J. Dickrell III University of Florida, Mechanical Engineering Department, Gainesville, FL 32611 D. B. Dooner University of Puerto Rico, Mechanical Engineering Department, Mayaguez, PR 00681-9045 W. G. Sawyer University of Florida, Mechanical Engineering Department, Gainesville, FL 32611 The Evolution of Geometry for a Wearing Circular Cam: Analytical and Computer Simulation With Comparison to Experiment The evolution of the geometry of a simple two-dimensional circular cam as a result of wear is studied using three complementary approaches: a closed form analytical expres- sion, a computer simulation, and the development of an experimental apparatus. Experi- ments were run for over 1.5 million cycles, and measurements of cam shape and follower motion were recorded and compared favorably to the predictions of both techniques. Errors associated with an accelerated computational approach are discussed. @ DOI: 10.1115/1.1504092 # Introduction Life prediction for dynamic systems is an important concern for machine designers to consider for technical and economic rea- sons. A better understanding of the manner in which components wear out can significantly aid engineers in design work. A key issue in predicting component life that demands careful consideration is the coupling of wear and load in surface contacts. A simple extrapolation of wear properties at the initial cycles of a mechanism can greatly over-predict or under-predict the amount of wear realized in that components life due to the ever-evolving contact conditions at the interface. Several prediction methods are available that take this coupling into account. Numerical studies, which include the finite-element method ~ FEM ! , have been used to simulate wear in silico . Podra and Andersson @ 1 # published a thorough investigation of sliding-wear using FEM. The iterative nature of numerical simulations enables them to encompass the changing loads and geometries in the con- tact region, therefore modeling wear processes accurately. Another advantage of numerical simulation is the capability to rapidly change test conditions and component properties without inordi- nate set-up cost or significant downtime. One downside to these numerical processes is that through certain refinements of the nu- merical simulation, the model can become more costly and more time consuming than physical testing. Many studies are more thoroughly reviewed in papers by Blanchet @ 2 # and Sawyer @ 3 # . An alternate approach first proposed by Blanchet @ 2 # , and fol- lowed by Sawyer @ 3 # , is the development of a closed-form ana- lytical expression for simple mechanisms using a simple line re- moval term for wear. These expressions are less common than other approaches due to their exclusivity to certain types of prob- lems. For those special problems however, these closed-form expressions have proven extremely effective at predicting wear behavior @ 4 # .....
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- Spring '08