Modelling of ultrasonic piezoelectric transducer

Ena izmed pomembnejših komponent naprave za ultrazvočno varjenje je ultrazvočni pretvornik, ki električno energijo pretvarja v mehansko. Podobne ultrazvočne pretvornike se uporablja tudi v medicini ter v ultrazvočni čistilni tehnologiji. Razlikujejo se po geometriji komponent in frekvenci delovanja. Za delovanje pretvornika in ugotavljanje njegove resonančne frekvence je zelo pomembna impedančna karakteristika. V pregledu literature je predstavljeno ultrazvočno varjenje ter piezoelektrični materiali, ki omogočajo delovanje piezoelektričnih ultrazvočnih pretvornikov. Prikazan je postopek modeliranja ultrazvočnega pretvornika v programski opremi Comsol Multiphysics. Opisan je eksperimentalni sistem za merjenje impedančne karakteristike in amplitude pomikov. Dokazali smo, da se simulirana in izmerjena impedančna karakteristika zelo dobro ujemata. Ugotovili smo, da na impedančno karakteristiko, amplitudo pomikov, resonančno frekvenco in lokacijo vozlišča longitudinalnega nihanja vplivajo masa in geometrija elementov pretvornika. Z izdelanim računalniškim modelom je možno izvesti simulacijo delovanja ultrazvočnega pretvornika še preden se ta izdela, kar občutno zmanjša stroške razvoja.Ultrasonic transducer, which converts electrical energy to mechanical energy is one of the most important components of an ultrasonic welding machine. Similar ultrasonic transducers are used as sonars in medical applications and in ultrasonic cleaning devices. They differ in geometry of certain parts and operating frequency. Impedance characteristics of each transducer is very important for a proper operation of the transducer and for determination of its resonance frequency. In the literature review ultrasonic welding and piezoelectric materials, which enable the energy conversion are described. Also modelling of the ultrasonic transducer in Comsol Multiphysics software is described minutely. Experimental systems for measuring the impedance and strain amplitude are presented. We proved that the simulated and measured impedance characteristics are very well matched. It was established that the impedance characteristics, strain amplitude, location of longitudinal vibration node and resonance frequency are influenced by the mass and geometry of transducer elements. The computer model of the ultrasonic transducer can be used to predict how a manufactured transducer will work before it is even produced, which cuts down development costs