Objective
In the ultrasonic travelling wave motor electrical signals generate high-frequency mechanical vibrations via piezo elements, the-high frequency vibration then being transformed into rotatory mechanical motion via contact and friction between elastic solids.
The motor is presently being intensively used in photo cameras. It may also have a high potential in automation, control and in the automotive industry. This requires intensive research concerning the wave propagation and contact phenomena as well as modelling the interaction of the piezo ceramic elements with the elastic parts. Such research is presently being carried out in several European countries sponsored by industry and by different national organisations, e.g. in Germany by the Deutsche Forschungsgemeinschaft. In the NIS extensive basic research in this field has been carried out.
This project will carry out an examination in depth of the applicability of classical Hertz theory to dynamic contact problems. Preliminary investigations have shown that there may be significant restrictions, especially when bodies in contact vibrate near their resonance frequencies. On the other hand, motion and energy transformation is most effective under resonance excitation. Therefore the project will make it possible to find solutions to several model problems concerning the frictional contact interaction between solids under near-resonance excitation. These problems are extremely complicated because they lead to non-linear boundary-value problems for partial differential equations with unknown separation of the adhesion and slip zones. In these zones the boundary conditions change from those expressing proportionality between normal and tangential stresses to kinematic conditions of adhesion together with well-known inequalities for stresses. Also, the velocities of the relative motion of the solids are unknown. They are to be determined simultaneously with the contact stress distributions from the rigid body equations of motion.
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64289 Darmstadt
Germany