中文摘要：

基于机电阻抗技术，采用一种新型压电陶瓷纤维复合材料MFC（Macro—fiber compos—ite），对管道连接处法兰的螺栓工况进行监测实验研究。首先，研究了螺栓扭矩大小对管道法兰结构的阻抗的影响程度。在对螺栓开始施加扭矩时阻抗值变化明显，当扭矩增大到一定程度后，阻抗变化减缓。同时进一步研究了松动螺栓数量与管道法兰结构的阻抗变化之间的关系。结果显示，结构的损伤值随松动螺栓个数的增加呈线性增长。采用均方根偏差统计算法，对在不同工况条件下管道法兰结构处测得的阻抗值进行了有效的分析和处理。结果表明，采用MFC作为压电敏感元件的机电阻抗法，用于管道法兰结构健康监测具有较好的稳定性和应用潜力。

英文摘要：

A new type of piezoelectric composite fiber material, named as MFC （Macro-fiber composite）, was adopted to monitor the working condition of bolt installed on flange at pipe connection based On electromechanical impedance method. Firstly, the effect of torque applied to bolt on impedance curves of host structure was experimentally investigated. At the beginning of torque application to bolt, the received impedance curve changes obviousely. After the ＂applied torque increases to a certain extent, the change of impedance becomes mild. Furthermore, the relation between number of loosed bolt and the change of impedance curves received on the pipeline flange was also investigated. It is found that the damage index values of pipe structure increase linearly along with the increase of loosed bolt number. Root mean square deviation algorithm was used to effectively analyze and process the impedance values of pipe flange obtained under different working conditions. Therefore, it is easily concluded that electromechanical impedance-based method combining MFC as piezoelectric sensing element can be applied for health monitoring of flange in pipe structure and has good stability and potential application.