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Abstract

In this research project the rigid body (or acceleration) noise together with the sound due to transient vibration has been studied for colliding spheres. In the investigation of the rigid body sound radiated by colliding spheres the three cases considered cover elastic, plastic and visco-elastic impact.

For elastic impact the Hertz law of contact was used for predicting the force time history during the contact period. The velocity potential for an oscillating sphere is also obtained and from this can be derived the sound pressure in the far field for a unit acceleration impulse. Convolution of this pressure term with the acceleration from the Hertz theory enables the computation of the pressure as a function of time.

For the case of radiation due to inelastic collision the Andrews theory is used in which the contact period is divided into three stages, an initial elastic loading period, secondly an elastic-plastic loading and finally an elastic loading period, Knowledge of the accelerations during each period enabled prediction of sound pressure with the aid of the convolution method.

The sound pressure radiated by a visco-elastic sphere in collision with a metallic sphere is also analysed. The model was based upon the use of the force-time relationship developed by Pao.

Finally, the transient vibrations of solid and hollow spheres are studied and the sound caused by transient vibration for both types of sphere are computed.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science Q Science > QC Physics
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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