基于压电阻抗技术的金属材料弹性变形检测研究

Research on the Measurement of Elastic Deformation of Metal Materials Based on Piezoelectric Impedance

基于压电阻抗技术的结构健康监测原理,对低碳钢圆棒试样单轴拉伸弹性变形过程中安装在其上的压电材料的阻抗信息进行了分析,探究采用压电阻抗谱中峰值频率变化表征金属材料弹性变形(也即材料应力)状态的方法的可行性.将压电材料片作为主动传感器,粘贴在圆棒的端部圆截面(受压变形区)和杆中部(拉伸变形区)两种位置,分别测取园棒试样不同拉伸伸长情况下的阻抗信号.分析试验结果发现:随着弹性伸长变形量的增加,端部压电导纳(阻抗的倒数)谱中对应峰值频率减小,而杆中部压电导纳谱中对应峰值频率增加,两个部位的压电导纳频率变化接近线性规律.由此可得出结论:可以利用压电阻抗(导纳)技术,通过测量部位的压电导纳谱信息,以频率为特征参数对结构件的应力状态进行监测;通过端面压电材料输出导纳谱信息中频率改变量,可实现对轴杆类构件轴向应力状态进行监测,这个方法特别适合于埋入式螺栓,混凝土中预应力钢筋等轴向力的监测.

Based on the piezoelectric impedance structure health monitoring technique,the impedance information of the piezoelectric patches of the low carbon steel round bar during its uniaxial tensile elastic deformation was analyzed.A method using the peak frequency shift in the piezoelectric impedance spectroscopy to characterize the elastic deformation(i.e.,material stress)of a metal material is proposed.The piezoelectric patches were pasted as active sensor in the end circle section(compression deformation zone)and the middle part of the bar(tensile deformation zone),and the impedance signals of the piezoelectric patched were obtained under different tensile elongation condition.The experimental results show that with the increase of the elastic deformation,the peak frequency in the impedance spectrum of the piezoelectric patch on the end of the specimen decreases,while the peak frequency of the patch on the middle increases,and the frequency change is close to the linear with the tensile elongation.The experimental results are consistent with the theoretical analysis from the stress point of view.It is prove that by using frequency in the piezoelectric admittance spectrum as a characteristic parameter,the piezoelectric impedance technique can be used to characterize the stress state of a structure.It is especially suitable for monitoring the axial force of pre-embedded bolts and pre-stressed steel bars in concrete.