چكيده به لاتين
Tonpilz transducers have wide application at sonar systems for acoustic wave generation in water. These transducers use crystals piezoelectric properties for ultrasonic wave generation, by applying an alternate electric field they cause mechanical vibrations and as the result ultrasonic waves will be generated. Constant temperature increase over time, due to the hysteresis loss in piezoelectric material, is one of the common problems affiliated with Tonpilz transducers. However, by calculating dissipated energy for every cycle, estimation of cycle number for every mechanical component which works under that cycle load is possible by defining fatigue entropy and monitoring components entropy up to fatigue entropy. Here, the
components temperature increase is not the focus and just their instant entropy is the defining factor. In this thesis with the use of finite element method, at first the impedance response of an already designed transducer at a specific frequency is calculated and its hysteresis loops are estimated according to impedance curve. Then with measuring of the area inside the loops, the amount of loss per cycle is calculated. In the next step, considering Curie temperature at which crystals will lose their piezoelectric properties and also regarding structural equation of piezoelectric entropy rise, fatigue entropy for piezoceramic is calculated and also transducers entropy increase for fatigue entropy calculation is monitored. Finally, the time limit for using
the transducer is estimated.
Keywords: Tonpilz transducers, piezoelectric materials, impedance response, hysteresis
loss, Curie temperature, fatique entropy
