Vom 24.10.2022 bis zum 26.10.2022 fand der International Workshop on Piezoelectric Materials and Applications in Actuators (IWPMA) online statt. Diese jährliche Konferenz bringt Forscher, führende internationale Spezialisten und die Industrie zusammen, die an piezoelektrischen Materialien und Ultraschalltechnologien arbeiten. Olga Friesen berichtete in ihrem Beitrag "Estimation of piezoelectric material parameters of ring-shaped specimens" über eine Methode zur Materialparamerterschätzung von ringförmigen Piezokeramiken.
Estimation of piezoelectric material parameters of ring-shaped specimens
Autoren: Olga Friesen, Leander Claes, Nadine Feldmann, Bernd Henning
A requirement for the increasingly simulation-driven design process of piezoelectric actuators and sensors are accurate material parameters. Historically the parameters of piezoelectric materials are determined using the well-known IEEE standard on piezoelectricity. However, the method proposed in this standard, which is an analytical approach based on the evaluation of resonance frequencies, relies on impedance measurements on a number of differently shaped and thus differently processed samples. Because the processing method of the sample has huge influence on the sample’s properties, the resulting material parameter sets are inconsistent. Further, it is advantageous if material parameters can be determined using samples with the same geometry that is to be used in the respective actuator or sensor. Previous studies show that a full set of material parameters can be determined in an inverse procedure using a single disc-shaped specimen with an electrode structure optimised for increased sensitivity of the impedance with respect to all material parameters. However, especially high-power actuator applications often employ ring-shaped piezoelectric components, necessitating an adaptation of the previously developed method.
In the contribution, the authors present an approach for the estimation of piezoelectric material parameters using ring-shaped hard- and soft-piezoelectric samples. An initial, rough estimate for the material parameters is determined using analytical approximations for the resonance frequencies derived from the IEEE standard. These values are then refined in an inverse approach that uses analytical expressions for the electrical impedance of piezoelectric rings as a forward model. Further refinement is achieved by using finite element simulations as the forward model. The procedure is first evaluated using finite-element simulation results of the electrical impedance as a surrogate for the measured impedance to verify that the estimates for the material parameters match the provided parameter values, showing good agreement both for the virtual soft- as well as the hard-piezoelectric material. Finally, the procedure is applied to impedance measurement data, showing good agreement between simulation and measurement result and yield material parameters for a hard-piezoelectric ring.