Date of Award
Ph.D. in Engineering Science
Elizabeth K. Ervin
Arunachalam M. Rajendran
This research is prerequisite to determining structural health and estimating wear-limited life of contact/impact machinery components. Prevention, or at least early notification, of impact-induced wear is essential for preventing economic loss and enhancing personnel safety. Thus, an efficient model which is discrete in time and continuous in space was undertaken; an euler-bernoulli beam with adjustable boundary conditions and variable impact is numerically studied under a pulse loading. Structural stiffness, material modulus, contact stiffness, contact location, damping ratio, pulse duration, clearance and boundary conditions are investigated. A reference system is used as the basis for parameter studies and solution convergence is examined for three boundary conditions. Overall numerical simulations show reasonable response for all the comparison of case studies. The contact location and clearance were found to be important factors due to their direct influence of mode shapes. One example application is illustrated, and comparisons show that considering possible boundary contact but not changing e provides better estimation. Experiments were carried out to verify the effects of influential parameters. Two beam specimens with difference slenderness were designed and examined under point contact/impact. A half-sine pulse excitation was applied through a mechanical shaker, and the deflection was captured by a high speed camera. Numerous test cases were conducted that varied pulse duration, pulse amplitude, clearance, and contact location. Decreasing the pulse duration lowers all deflection amplitudes, but the time in contact is insensitive. No gap causes the smallest beam response, and increasing clearance generates greater free deflection amplitude. Representative test cases were selected for validating the theoretical model. When comparing numerical simulation with experimental result for both specimens, satisfactory agreement for amplitude and duration can be reached even with raw input parameters of the cases without contactor. When there is a contactor, the model shows better prediction for the thick specimen with slenderness ratio of 0.0279 than the thin specimen with slenderness ratio of 0.0186. Contact stiffness and pulse amplitude are two possible sources of error. The contribution of this study is the incorporation of unique pulse loading, changeable boundary conditions, adjustable contact/impact situations, comprehensive parameter studies, and high speed photography.
Xu, Weiping, "Modeling of Transient Response of an Elastic Beam With Flexible Supports and Variable-Location Impact" (2010). Electronic Theses and Dissertations. 320.