Measurement methods for the characterization of the thermal and piezoelectric material behaviour

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An essential prerequisite for the successful identification of complete and consistent material parameter sets is the precise and correct determination of the piezoelectric material or component properties. This requires the development of suitable measurement methods and their implementation in measurement systems. Primarily, the electrical (electrical impedance), mechanical (surface displacement) and thermal (temperature distribution) variables are recorded quasi-continuously and simultaneously for a complete description of the material and component behaviour.The conception and technical implementation of various experimental measurement setups for the targeted investigation of selected influencing variables is planned. Initially, only the linear material parameters or sets of material parameters are determined as a function of the temperature (AP3 and AP4). For this purpose, the frequency-dependent electrical impedance curves of piezoceramic samples with optimized electrode configuration are measured at different temperatures (AP1) and the material parameter sets are determined in cooperation with the MOP group. This is followed by investigations of the influence of a mechanical load (AP5) and a superimposed DC voltage (AP6). As a result of these preliminary investigations, the parameter space for the material parameters will be determined and an initial description of the relevant non-linear properties will be available. Building on this, the groups EMT and LDM will develop a suitable material model describing the thermal and piezoelectric material behaviour for high-power ultrasound applications in close cooperation with the other groups within the sub-projects ANA, OPT and SIM.Based on these results a measurement system to characterize the non-linear behaviour of piezoceramics is developed (AP8). The EMT group's prime objectives are the automation of the measurement system and on the acquisition of electrical quantities. Due to the non-linearities, evaluations of the frequency-dependent impedance can no longer be applied. Instead, methods and circuits for evaluating the signal spectra of current and voltage are developed. At the same time, the LDM group develops the measurement technology for recording the mechanical and thermal parameters (vibrometry and pyrometry) of the piezoceramic sample.Finally, the developed measurement method, the material model, the simulation environment and the parameter identification method are checked and verified by applying them to piezoceramic samples of different geometry, electrode configuration and material.