Energy transformation, ultrasonic

Comparison of several techniques (namely Fourier transform infrared spectroscopy (FTIR), simultaneous thermogravimetric analysis-differential scanning calorimetry (TGA-DSC) and ultrasonic spectroscopy) for assessing the residual physical and mechanical characteristics of polymer matrix composites (PMCs) exposed to excessive thermal loads showed the measured power spectra of ultrasonic energy to correlate with performance of graphite fibre epoxy matrix composites exposed to thermal degradation, and also that analyses with the three techniques all pointed to the same critical temperature at which thermally induced damage increased sharply [58],... 

Ultrasonication involves the conversion of a conventional 50 / 60 Hz alternating-current line power to 20 kHz electrical energy and transformation to mechanical vibration. A lead zirconate titanate electrostrictive (piezoelectric) crystal, when subjected to alternating voltage, expands and contracts. This transducer vibrates longitudinally and transmits this motion to the horn tip. The horn tip is immersed in the liquid slurry and cavitation... 

Elastomechanical ultrasonic vibration is generated by the transformation of electric energy in piezoceramic or magnetostrictive sonic converters. A voltage generator serves to convert a low-frequency mains voltage into... 

Another process in which mechanical energy is transformed into heat is ultrasonic welding, which is illustrated in Figure 8.9. A piezoelectric crystal transmits longitudinal vibrations at a frequency of about 20 kHz through... 

At first, any type of energy is susceptible to be converted into ultrasonic energy for example, the mechanical energy accumulated in fluids could be transformed into ultrasonic waves by means of a siren. However, the main applications at the industrial level include systems that use electricity as the energy source. 

In order to transform the kinetic energy of a fluid into ultrasonic waves, siren and whistle systems are used. In siren systems, the fluid is forced to pass across a hole and depending on its velocity, the fluid flux will generate turbulence that constitutes the mechanical wave. In whistles, the fluid is forced across a thin blade which causes the blade to vibrate. For each vibrational movement, the leading face of the blade creates a pressure wave (Mason, 1998). 

Transducer. A transducer or a probe is a device that emits a beam of ultrasonic waves when bursts of alternating voltage are applied to it. An ultrasonic transducer is comprised of piezoelectric material. Piezoelectric material is material that vibrates mechanically under a varying electric potential and develops electrical potentials under mechanical strain, thus transforming electrical energy into mechanical energy and vice versa (2). As the name implies, an electrical charge is developed by a piezoelectric crystal when pressure is applied to it and reverse is also true. The most commonly encountered piezoelectric materials are quartz, lithium sulfate, and artificial ceramic materials such as barium titanate. 

---