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This thesis considers the use of chaos concepts in investigating the dynamics of two discontinuously nonlinear mechanical systems having two degrees of freedom. The nonlinearity considered is in the form of a discontinuous stiffness effect, and can cause the systems to exhibit chaotic motion. The first system is a rotor system with a bearing clearance effect. The second is a nonlinear vibration absorber, comprising a conventional linear absorber and a linear snubber stiffness, which the auxiliary mass intermittently contacts. Numerical integration is used in solving the equations of motion for each system. Equivalent physical rigs are tested. Both the theoretical and experimental results are analysed using chaos techniques such as phase plane portraits, Poincaré maps, frequency spectra and bifurcation diagrams. Comparison made between the differently acquired results shows that fairly good correlation is obtained in both systems, for realistic values of damping. Periodic, quasiperiodic and chaotic responses are exhibited by both systems, for different combinations of system parameters, with the responses of the systems being extremely sensitive to changes in these parameters. Investigations of the rotor system concluded that quasi-periodic responses are only possible if there is some form of cross-coupling present. An effective discontinuously nonlinear absorber is developed, theoretically. A reduction in the amplitude of the second resonance peak of the linear absorber is achieved. This enables the primary system to be operated over a wider frequency range without reaching the large amplitudes to the second resonance. The non-linear absorber also has the effect of attenuating the response from the auxiliary mass. Fatigue analysis is carried out to investigate the effect of chaotic motions on mechanical components. The analysis reveals the subharmonic motions are more damaging than chaotic motions, which are in turn more damaging than simple fundamental responses.

The most practical treatment for reducing the noise of present diesel engines is to replace the thin-section, noise-radiating components with constrained damping layers, where a viscoelastic layer is sandwiched between two elastic layers to give the composite panel high damping characteristics. The damping ability of such panels is highly dependent on dynamic shear properties of viscoelastic materials as well as on the selection of elastic materials. The damping shear properties of viscoelastic materials are highly dependent on frequency and temperature. Experimental data on the damping properties of viscoelastic materials are, so far, limited to a small low frequency range. The forced vibration non-resonant technique is adopted in the present investigation. Atest rig has been designed, built and developed to measure the dynamic shear properties of some visoelastic materials over a wide range of temperature (40 to 1000C). These properties are also measured over a wide range of frequency (50-1500 Hz), covering part of the audio frequency range, in which the severity of engine noise occurs. Polysulphide rubber and ethylene propylene rubber have been tested. Their dynamic shear properties have been obtained, tabulated and plotted as functions of frequency and temperature. The effect of strain amplitude has been investigated and discussed. A new approach for an easy, fast and direct measurement of the loss shear modulus has been proposed. It has been found that both viscoelastic materials possess considerable damping, especially over the frequency range of 900-1500 Hz. The effect of strain amplitude was found negligible. The optimum design and damping ability of three layer composite panels have been investigated. The effects of elastic and viscoelastic material on the damping of these panels has been examined. Magnesium has been found to be a superior elastic material of those investigated. Aluminium is the next most suitable elastic material, with steel as the least suitable elastic material. Polysulphide rubber and ethylene propylene rubber have been found suitable for use in composite damping panels, but their relative attractiveness is strongly dependent on frequency and temperature.

No description available.

Thesis (M.S.)--Ohio University, November, 1987. / Title from PDF t.p.

Thesis (Ph. D.)--University of Adelaide, Dept. of Mechanical Engineering, 1999? / Copy 2 does not have a CD-ROM. Includes bibliographical references (p. 317-330). Also available in an electronic version.

Thesis (M. Eng. Sc.)--University of Adelaide, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (leaves 94-97).

Thesis (Ph.D.) - Swinburne University of Technology, Industrial Research Institute Swinburne - 2000. / Submitted for the degree of Doctor of Philosophy, Industrial Research Institute Swinburne, Swinburne University of Technology - 2000. Typescript. Includes bibliographical references (p. [232]-240).