Type of Document Master's Thesis Author Andruet, Raul Horacio URN etd-11242009-020021 Title Behavior of a cracked shaft during passage through a critical speed Degree Master of Science Department Civil Engineering Advisory Committee
Advisor Name Title Plaut, Raymond H. Committee Chair Holzer, Siegfried M. Committee Member Rojiani, Kamal B. Committee Member Keywords
- Cranks and crankshafts
Date of Defense 1991-08-15 Availability restricted Abstract
The detection of cracks in structural components and the evaluation of their sizes without the need of removing them from the machine in which they are placed is very important for preventing failures. The objective of this thesis is to study the effects of cracks on the dynamic behavior of shafts under acceleration or deceleration, in order to find methods or procedures capable of detecting the presence of cracks prior to failure.
The equations of motion for a simply supported Bernoulli-Euler shaft are developed following Wauer's formulation. Galerkin's Method is used to obtain five-term approximate solutions. The first two natural frequencies are found for both the uncracked and cracked shaft. A computer program is written to perform the numerical integration of the equations. The shaft is subjected to several constant accelerations and decelerations. Tables and figures showing the results are presented along with discussions and comments related to the different runs made and the results obtained. The effect of the initial position angle of the eccentricity is studied to find the influence of this parameter. The effects of crack position and crack depth on the dynamic behavior of the shaft are also included in this work. Time histories and summary graphs are presented to make easier the interpretation of the results.
Final conclusions and future research proposals complete the work done in this thesis.
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