Ultrasonic vibration energy effect

Syllabus (1957-1958) pp 137-38 (Frank-Kamenetskii formulation) 151-62 [Session 13, entitled "Hetergeneity of the Initiation Process , includes initiation of solid expls by impact, friction, thermal effect, elastic waves by ultrasonic vibrations, electromagnetic energy and chemical influence. 

Electric energy is converted into mechanical vibrations in modem machinery using the piezoelectric effect. It concerivs the reversible property of special ceramic materials to deliver an electric voltage when affected by external forces. This characteristic is used for the generation of ultrasonic vibrations in such a way that the applied voltage is converted into mechanical vibrations. Modern sonic converters usually contain several piezoceramic disks of lead zirconate titanate restricted by two final masses that are mechanically prestressed by a centric screwing. 

Fig. 2 shows the entrance die pressure and power consumption for various wt% loadings of CNTs as a function of ultrasonic amplitude. The measured pressure is before the ultrasonic treatment of PEI/MWNT composites. A continuous decrease in pressure with increasing ultrasonic amplitude was observed. This is from a combination of heating from dissipated energy from ultrasound, cavitational effect from ultrasonic waves leading to some thixotropic and permanent changes in polymer, reduction in friction at die walls and horn surfaces due to ultrasonic vibrations and possible shear thinning effect created by ultrasound waves. The die... 

The practical application of ultrasonics requires effective transducers to change electrical energy into mechanical vibrations and vice versa. Transducers are usually piezoelectric, ferroelectric, or magnetostrictive. The application of a voltage across a piezoelectric crystal causes it to deform with an amplitude of deformation proportional to the voltage. Reversal of the voltage causes reversal of the mechanical strain. Quartz and synthetic ceramic materials are used. 

The percussive effect of high intensity vibrations generated in an extruded polymer melt can be influenced by ultrasonic oscillations. The periodic shift in the pressure generated by the action of the screw affects the processed material and the energy transferred to the... 

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