【作者】 刘建；

【导师】 裘进浩；

【作者基本信息】 南京航空航天大学 ， 仪器科学与技术， 2010， 博士

【摘要】 含金属芯压电纤维(MPF)是一种新型压电驱动器与传感器,其结构细小,粘贴在基体结构表面,不会对结构性能产生影响;易于埋入到复合材料中,而不会对基体材料产生影响。因此MPF非常适宜用作基于Lamb波的结构健康监测中的传感与驱动元件。本文提出采用MPF作为超声Lamb波传感器与驱动器,研究了MPF传感、激励Lamb波的机理,建立了MPF传感Lamb波模型;同时把MPF作为Lamb波传感器分别在一维、二维结构中进行了结构健康监测应用研究。本文的主要工作和创新点主要有:(1)建立了圆柱坐标系下MPF的压电方程。根据MPF的压电方程,推导了粘贴在结构表面的MPF的应变响应电压公式。并根据MPF的应变传感响应原理,推导了MPF对圆形压电片激励Lamb波的响应电压模型,并进行了实验验证;进行了MPF和圆形压电片分别传感Lamb波的对比实验研究,研究结果表明MPF可以用来传感超声Lamb波信号。(2)分别采用幅值和小波变换能量因子的方法对MPF传感超声Lamb波的方向性特性进行了研究。以A0模式Lamb波为例,推导了MPF对圆形压电片激励Lamb波的传感灵敏度系数随Lamb波入射角度变化的函数表达式。同时对推导结果进行了实验验证。研究结果表明MPF传感Lamb波具有很强的方向性,采用小波变换能量因子进行传感方向性表征更能体现出MPF对Lamb波的方向性传感特性。(3)研究了MPF激励Lamb波的机理,建立了基于MPF的激励、传感系统,并进行了实验研究,分析了MPF激励、传感单一模式Lamb波的可行性。同时,还分别基于幅值方法和小波变换能量因子的方法研究了MPF激励Lamb波的方向性。(4)研究了MPF传感的Lamb波信号在不同损伤形式(结构承受载荷,可移除污迹,结构通孔损伤)下的变化情况,进而研究了Lamb波对不同损伤形式的敏感性。同时采用BP神经网络对三种损伤状态及健康状态进行了辨识。(5)利用Gabor小波变换计算损伤反射信号到达时间延迟的原理,把MPF作为Lamb波传感器,在一维结构中进行了损伤定位研究,损伤定位精度较高。(6)采用类似应变花的原理,提出了一种基于MPF花形组合单元的二维结构损伤定位方法,该方法无需知道Lamb波在介质材料中的传播速度,只需要测量MPF响应Lamb波的幅值。分别在铝板中进行了二维结构被动监测实验(模拟声源定位实验)与主动监测实验(载荷定位实验和通孔定位实验),定位精度较高,验证了MPF花形组合单元定位方法在二维结构损伤定位中的可行性。更多还原

【Abstract】 Metal-core piezoelectric fiber (MPF) is one of the new types of piezoelectric devices used for sensors and actuators. MPF has small size, and does not affect the performance of the structure when bonded on the surface or integrated with a host structure. Therefore, MPF has great potential to be used as actuators and sensors for structural health monitoring based on Lamb wave. Lamb wave sensing and generating using MPF is proposed, the principle of sensing and generating using MPF is researched, and the model of Lamb wave sensing is developed. Meanwhile, MPF using as a Lamb wave sensor is researched for structural health monitoring application in one-dimensional and two-dimensional stucture respectively. The major contributions and novel research results in this dissertation are summarized as follows:(1) The piezoelectric equation of MPF in cylindrical-coordinate system is developed. Based on the piezoelectric equation of MPF, the strain response formula of MPF boned on the surface of structure is derived. Then, the model of MPF’s response to Lamb waves excited by circular crested actuator is derived and verified by experiments; the comparative study of MPF and circular PZT’s response to Lamb wave is performed in the end, the results show that MPF has the capability of sensing Lamb waves.(2) The directivity of MPF’s response to Lamb waves is researched using amplitude and wavelet transformation factor respectively. Taking A0 mode Lamb wave as an example, the sensitivity factor function of MPF’s response to lamb wave excited by circular PZT is derived, and the result is verified by experiments. The result shows that MPF has high directivity to sense Lamb wave, the directivity characterized by wavelet transformation factor shows more clear in comparison with amplitude.(3) The principle of Lamb wave generation using MPF is researched, the Lamb wave generation and sensing system with MPF is then established, and verified by experiments. At the same time, the directivity of Lamb wave generation with MPF is researched by means of amptitude and wavelet transformation factor method respectively.(4) The changes of MPF’s response to Lamb wave in different damage type (load, removable putty damage, hole) is researched, and then the response sensivity of Lamb wave to different damage is researched. The BP NN is successfully applied to distinguish three damage type and the health type.(5) According to Gabor wavelet transform to calculate time delay of damage signal, MPF is used as Lamb wave sensors for damge localization in one-dimension structure, the accuracy of damge localization is very high.(6) According to the principle of resistance strain rosettes, a novel method for two-dimension structure damage localization based on MPF rosettes is proposed. This method doesn’t need the speed of Lamb wave in the medium, only need the amplitude of Lamb wave. The passive monitoring experiment (sound source localization) and active monitoring experiment (load localization and hole localization) are performed in two- dimensional Al plate, the accuracy of damge localization is very high, which confirms that the MPF rosettes method has the cability of damage localization in two-dimension structure.、更多还原