Predicting the coefficient of restitution of impacting elastic-perfectly plastic spheres |
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Authors: | Robert L Jackson Itzhak Green Dan B Marghitu |
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Institution: | (1) Laboratory for Surface Technology and Tribology, Faculty of Engineering Technology, University of Twente, Drienerloolaan 5, Postbus 217, 7500 AE Enschede, The Netherlands |
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Abstract: | The current work presents a different methodology for modeling the impact between elasto-plastic spheres. Recent finite element
results modeling the static deformation of an elasto-plastic sphere are used in conjunction with equations for the variation
of kinetic energy to obtain predictions for the coefficient of restitution. A model is also needed to predict the residual
deformation of the sphere during rebound, or unloading, of which several are available and compared in this work. The model
predicts that a significant amount of energy will be dissipated in the form of plastic deformation such that as the speed
at initial impact increases, the coefficient of restitution decreases. This work also derives a new equation for the initial
critical speed which causes initial plastic deformation in the sphere that is different than that shown in previously derived
equations and is strongly dependant on Poisson’s Ratio. For impacts occurring above this speed, the coefficient of restitution
will be less than a value of one. This work also compares the predictions between several models that make significantly different
predictions. The results of the current model also compare well with some existing experimental data. Empirical fits to the
results are provided for use as a tool to predict the coefficient of restitution. |
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Keywords: | |
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