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以研究自由钢绞线和埋入水泥介质的钢绞线中超声导波纵向模态的衰减特性为目的,首先理论分析了钢绞线中心和外围钢丝中纵向模态的频散和多模态特性,之后采用厚度振动型压电陶瓷片端部激励和自行研制的磁致伸缩式传感器接收的方法对公称直径17.80mm的7芯钢铰线进行了最低阶纵向模态导波L(0,1)的激励接收试验。研究结果表明,在自由钢绞线中频带110~160kHz内模态导波L(0,1)的衰减随频率的增加而减小;在埋置于水泥介质的钢绞线中,频带110~160kHz内模态导波L(0,1)幅度随水泥埋置长度的增加而减小。这些试验结果为分析纵向模态对钢绞线的检测能力提供了试验依据,为超声导波技术应用于钢绞线健康检测奠定了基础。
In order to study the attenuation characteristics of the longitudinal modes of ultrasonic guided waves in free strand and buried concrete, the dispersion and multimodality of the longitudinal modes in the center of the strand and in the peripheral wires are theoretically analyzed. Then the method of receiving by the magnetostrictive sensor excited by the end of thickness vibration type piezoelectric ceramic and self-developed magnetostrictive sensor was adopted to conduct the lowest-order longitudinal mode guided wave L (0, 1 ) Of the incentive to receive the test. The results show that the attenuation of mode guided wave L (0,1) decreases with the increase of frequency in the frequency band of 110 ~ 160kHz in the free steel strand. In the strand embedded in the cement medium, The amplitude of the L (0,1) mode guided wave in 160 kHz decreases with the increase of the buried length of the cement. These test results provide the experimental basis for the analysis of the longitudinal modality of the detection ability of the strand, which lays the foundation for the application of the ultrasonic guided wave technology to the strand health detection.