Type of Document Master's Thesis Author Collins, Kevin Ralph URN etd-08012012-040538 Title The effect of cracks on the dynamic behavior of bars and shafts 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
- Rotational motion
Date of Defense 1989-03-29 Availability restricted AbstractNondestructive methods of detecting cracks in structural components and machinery are important,
both in preventing failures and in establishing maintenance procedures. This thesis considers how
the vibration behavior of cracked members can be modelled mathematically and how these mathematical
models may lead to advancements in crack detection procedures. Two separate cases are
considered: the longitudinal vibration of a cracked bar and the coupled vibrations of a cracked rotating
In the longitudinal vibration study, the equation of motion is developed for a cantilevered bar with
a symmetric surface crack. Next, Galerkin's Method is used to obtain one- and two-term approximate
solutions. Both forced and free vibrations of the bar are analyzed. Graphical results showing
the relationships between displacement and crack size, crack position, and forcing frequency are
presented and discussed. Spectral analysis is used to compare uncracked and cracked bar behavior.
Finally, a sensitivity analysis of the forced vibration case is conducted to observe how the forcing
frequency affects the rate of change of steady-state response at the onset of cracking.
In the second part of the thesis, a similar analysis is conducted for a cracked, simply-supported
Timoshenko shaft rotating at a constant angular speed. The equations of motion derived by Wauer
(b) are used as the basis of the study. Again, Galerkin's Method is applied to obtain approximate
solutions. Time histories and spectra are used to observe how changes in various parameters influence
the vibration behavior. The effects of mass eccentricity and gravity are studied. Finally, the
effect of a periodic axial impact load is considered.
Filename Size Approximate Download Time (Hours:Minutes:Seconds)
28.8 Modem 56K Modem ISDN (64 Kb) ISDN (128 Kb) Higher-speed Access LD5655.V855_1989.C668.pdf 4.69 Mb 00:21:41 00:11:09 00:09:45 00:04:52 00:00:24next to an author's name indicates that all files or directories associated with their ETD are accessible from the Virginia Tech campus network only.
If you have questions or technical problems, please Contact DLA.