钢绞线中纵向模态衰减特性的试验研究

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。

Experimental research on attenuation characteristics of longitudinal modes guided wave in steel strands

In order to investigate the attenuation characteristics of ultrasonic longitudinal guided waves,first,the characteristics of longitudinal modes,such as dispersion and multi-mode,for centre and peripheral wires in steel strands are analyzed theoretically.In the experiment,the lowest longitudinal mode of ultrasonic guided waves,L(0,1) mode,is excited by piezoelectric thickness vibration element and received by developed magnetostrictive sensor in a seven-wire,17.80mm nominal diameter steel strand.In a traction-free steel strand,with the increase of frequency in the range of 110kHz-160kHz,attenuation of L(0,1) mode will decrease.Furthermore,in a steel strand embedded in cement,with the increase of embedded lengths,L(0,1) mode amplitudes decreases.The results provide experimental foundation for the analysis of inspection ability to steel strands using longitudinal modes and the application of ultrasonic guided waves technique to health monitoring of steel strands.