Study of advanced integrated piezoelectric sensor systems for the evaluation of structures and materials

开发紧凑、灵敏、耐用、廉价的机械测量实时传感器是一项重大的工程挑战，受到了研究和工业界的极大关注。在常用的传感器中，压电式传感器往往是最有吸引力的，它提供了最高的功率密度和相对容易的应用。其高度的机电耦合和几乎瞬时的响应时间使机械测量能够有效地转换为具有相对高灵敏度和高分辨率的电信号。目前，压电传感器被用于各种工程应用中，如用于检测裂纹和损伤的结构的无损评估，用于表征薄膜的机械性能以确定其厚度和模数，以及用于识别化学和生物物种的化学和生物表面声波装置等等。 压电式传感器广泛应用的主要障碍是(I)受其最小可检测应力的限制，以及(Ii)难以集成来自多个传感器的信号。基于单个压电传感器的现有技术只能在需要确定的参数数量非常有限的情况下使用。这导致了对含有嵌入损伤的结构的定量无损评估以及在声表面波器件中检测多种化学和生物物种的主要困难。 因此，本项目的目标是研究高灵敏度的集成压电传感器，并开发一种用于定量评估结构完整性的成像技术。为了开发高灵敏度的传感器，将开展超材料基压电传感器的研究。超材料是指表现出罕见的特殊性能的新型复合材料。新的压电传感器将是包含精心设计的局部结构的复合材料，通过它们之间的内部相互作用可以获得高灵敏度。对于损伤成像，通过对来自多个压电传感器的信号进行积分，可以对传感器附近的波传播进行再生和研究。然后，将建立基于来自多个传感器的信号的逆过程，以定量地识别干扰波传播的异常。 将进行理论和实验研究。研究的主要步骤包括：(I)建立不同载荷和边界条件下以纤维和薄片形式相互作用的压电元件的统一和基本的动力学模型；(Ii)使用所开发的模型来评估具有设计的局部结构的新型压电传感器的性能，并研究传感器的灵敏度与局部结构的布置之间的关系；(Iii)研究传感器对不同埋入异常的响应，并开发定量识别埋入缺陷的反技术；(Iv)进行实验研究以验证理论预测，评估新的传感器设计，研究用于损伤定量成像的集成多传感器。 该研究将大大提高人们对压电传感器的认识，并为压电传感器的设计提供重要的知识。该项目也代表了无损评估和其他相关领域的一个新课题。它的可行性已经从我们最近的研究结果中得到了明确的证明。从长远来看，研究成果可用于下一代压电传感器的设计。

Developing compact, sensitive, durable, inexpensive real-time sensors for mechanical measurements represents a significant engineering challenge and has received considerable attention from research and industrial communities. Among the commonly used sensors, piezoelectric sensors are often the most attractive, which offer the highest power density and the relative ease of application. Their high electromechanical coupling and almost instantaneous response time enable the effective conversion of mechanical measurements into electric signals with a relatively high sensitivity and high resolution. Piezoelectric sensors are currently used in various engineering applications, such as the nondestructive evaluation of structures to detect cracks and damage, the characterization of the mechanical property of thin films to determine their thickness and modulus, and the chemical and biological surface-acoustic-wave devices to identify chemical and biological species, to name a few. Major impediments to the wider application of piezoelectric sensors are (i) the limitation by their minimum detectable stress, and (ii) the difficulty in integrating signals from multiple sensors. Existing techniques based on individual piezoelectric sensors can only be used in situations where a very limited number of parameters need to be determined. This results in major difficulties in quantitative nondestructive evaluation of structures containing embedded damage and in the detection of multiple chemical and biological species in surface-acoustic-wave devices. It is, therefore, the objective of the current project to study highly sensitive integrated piezoelectric sensors and develop an imaging technique for the quantitative evaluation of structural integrity. To develop highly sensitive sensors, study of metamaterial-based piezoelectric sensors will be conducted. Metamaterials refer to new types of composites exhibiting exceptional properties not commonly observed. The new piezoelectric sensors will be composites containing carefully designed local structures, from which high sensitivity can be achieved through the internal interaction between them. For damage imaging, by integrating signals from multiple piezoelectric sensors, the wave propagation near the sensors can be regenerated and studied. An inverse process based on the signals from the multiple sensors will then be established to quantitatively identify the anomalies, which have disturbed the wave propagation. Both theoretical and experimental studies will be conducted. The main steps of the research include: (i) Developing a unified and fundamental dynamic model of interacting piezoelectric elements, in forms of fibres and sheets, under different loading and boundary conditions, (ii) Using the developed model to evaluate the behaviour of new piezoelectric sensors with designed local structures, which form interacting piezoelectric elements, and study the relation between the sensitivity of the sensors and the arrangements of the local structures, (iii) Studying sensor response to different embedded anomalies, and developing an inverse technique to quantitatively identify embedded defects, (iv) Conducting experimental studies for verifying the theoretical predictions, evaluating new sensor designs and studying integrated multiple sensors for quantitative imaging of damage. The proposed study will significantly improve the understanding and provide important knowledge for the design of piezoelectric sensors. The project also represents a new topic in nondestructive evaluation and other related areas. Its feasibility has been clearly shown from our recent research results. In the long term, the outcome of the research can be used in the design of next generation piezoelectric sensors.