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

成功识别完整和一致的材料参数集的一个基本前提是精确和正确地确定压电材料或组件的特性。这就需要开发合适的测量方法并在测量系统中实施。首先，电气（电阻抗）、机械（表面位移）和热（温度分布）变量被准连续和同时记录，以完整描述材料和部件的行为。计划各种实验测量设置的概念和技术实施，以针对选定的影响变量进行有针对性的研究。最初，仅线性材料参数或材料参数组被确定为温度的函数（AP 3和AP 4）。为此，在不同温度下测量具有优化电极配置的压电陶瓷样品的频率依赖性电阻抗曲线（AP 1），并与MOP组合作确定材料参数集。接着研究机械负载（AP 5）和叠加的DC电压（AP 6）的影响。作为这些初步调查的结果，材料参数的参数空间将被确定，相关的非线性特性的初始描述将是可用的。在此基础上，EMT和LDM小组将与ANA、OPT和SIM子项目中的其他小组密切合作，开发一种合适的材料模型，描述高功率超声应用中的热和压电材料行为。基于这些结果，开发了一种测量系统，以表征压电陶瓷的非线性行为（AP 8）。EMT集团的主要目标是测量系统的自动化和电量采集。由于非线性，频率相关阻抗的评估不再适用。相反，用于评估电流和电压的信号频谱的方法和电路被开发。同时，LDM团队开发了记录压电陶瓷样品力学和热学参数的测量技术（振动测量和高温测量）。最后，通过将开发的测量方法、材料模型、仿真环境和参数识别方法应用于不同几何形状、电极配置和材料的压电陶瓷样品，对它们进行了检验和验证。

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.