Characterising piezoelectric material parameters through a 3D FEM and optimisation algorithm

Self heating in underwater transducers can act as a limit for high performance transducers. Understanding the physical processes which drive ultrasound transducer self heating requires characterisation of the internal energy loss mechanisms. This study focuses on the energy loss mechanisms of the active part of the transducer, the piezoelectric component. A method which involves a 3D FEM model nested within an iterative simulated annealing scheme which determines the material parameters, including the energy loss parameters, is used to characterise a piezoelectric rod. This type of piezoelectric structure is commonly used in underwater transducers. A cost function is used to compare the difference between the measured electrical admittance and the modelled electrical admittance. The choice of the cost function used has an impact on which material parameters the method is able to optimise efficiently. In the case of the cost function used in this study, the method is successful at characterising the real values of the material constants. However, a more tailored cost function is needed to characterise the loss tangents successfully.