ultrasonic piezoelectric transducer,
high frequency ultrasonic transducer
In many cases , the transducer is followed by a metallic booster whichensures a displacement amplification, due to its special shape (conical .exponential or catenoidal). Then, a simple metallic cylinder, the length ofwhich is an integer number of half wavelengths, transfers the acoustic? energy to the workpiece. Sometimes, coupling devices with special shapesare used, for example to modify the vibration direction , to sumup the acoustic power from several transducers or to transferthe acoustic power from one transducer to several tools . Thefixing of the transducer or any acoustic components to the machine body isensured by different types of bearings, which are placed in nodal zones, sothat no disturbance is created.
The design of such transducers has generally been carried out usingequivalent electrical circuitsand this method has allowed aclass1cal analysis of power problems . However, thisapproach does not take account of the distributed nature of inertia andstiffness and, in most cases, it provides accurate results only if it isused as an empirical method, the values of the lumped electrical componentsbeing deduced from measurements. To overcome this problem and to describecorrectly the acoustic wave propagation in these structures, the transfermatrix approach has been used for a long time and is generallysufficient for quantitative analyses and forecasts .Nevertheless it is restricted to plane wave propagation and must be given up when more complex s truc ture geometries or displacement fields areconcerned . This is the case for actually three di mensional s truc tures(special coupling devices... for structures wi th lateral dimensions equalto or larger than one quarter of a wavelength, for structures with rapidvariations of their crosS section, or when complex motions (flexural orradial motions) occur . Then, only the finite element method is able toprovide an efficient help to the designer.
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