This experiment is designed to address the effects of joint related nonlinearities on system parameters. Specifically, the effects of freeplay on the natural frequency, damping, and modal complexity. Many modal analysis techniques assume a system exhibits linear properties that are time invariant. Large structures are commonly constructed with several pinned and bolted joints and these joints can lead to gap and frictional-type nonlinearities. Joint nonlinearities will result in exaggerated damping estimates and complex time-varying mode shapes. These characteristics will result in incorrect modal parameter estimation when estimation assumes linearity. The experiment's intent is to examine nonlinearities and indicate methods of estimating the amount of nonlinearity and the degree of looseness, of a joint, associated with the nonlinearity. A real system, constructed of masses, springs, and viscoelastic components will be tested to arrive at these results. The results of this experiment indicated that it is possible to identify freeplay in the system. In addition to this, a new method of determining a system's degree of nonlinearity was developed.
Library of Congress Subject Headings
Vibration--Control; Modal analysis; Damping (Mechanics); Engineering design--Data processing
Department, Program, or Center
Mechanical Engineering (KGCOE)
Merle, Timothy S., "An Experimental determination of freeplay and its effect on modal complexity and damping" (1997). Thesis. Rochester Institute of Technology. Accessed from
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