杆中导波声弹敏感模态与激励频率的确定方法

Determination of surveying mode and excitation frequency for waveguard structure stress measurement by use of acoustoelastic effect of guided waves in bar

基于超声导波声弹性效应检测波导结构的应力水平具有潜在的优势。为实现超声导波声弹应力检测的关键技术——检测模态与激励频率的选取,提出一种基于Murnaghan超弹模型的有限元特征频率法。使用该方法计算预应力杆中的频散特性,得到反映不同激励频率应力敏感性的声弹频散曲线,与文献中的L(0,1)模态试验结果进行对比,趋势一致,说明该方法的适用性。为进一步验证该方法的可靠性,选取L(0,1)模态声弹敏感的几组频率,在自制拉伸试验平台上,对碳素钢杆进行超声导波声弹试验。试验结果表明:低应力区域误差较大,在高应力区域误差均低于10%,且声弹常数与理论结果趋势一致。研究表明该理论方法可指导超声导波声弹应力检测时频率与模态的选取。

The method of measuring the stress level of waveguide structures by use of the acoustoelastic effect of ultrasonic guided wave is of potential advantages.In order to select the optimal surveying mode and excitation frequency in acoutoelastic stress testing,a finite element eigenfrequency method based on the Murnaghan hyperelastic model was presented.The dispersion characteristic of a prestressed bar was calculated using this approach,and the acoustoelastic dispersion curve was obtained for describing the stress sensitivity under different excitation frequencies.The results are consistent with those in other literatures.On this basis,selecting the surveying mode and excitation frequency,the acoustoelastic effect of L（0,1）mode was inspected for Q235 carbon steel bar on a homemade tensile test platform.The results show that：the errors are great in low stress region whereas,in high stress region it can be controlled within 10%, and the tendency of acoutoelastic constants is in agreement with the theoretical results.The study proposes a method that can provide a determination method of surveying mode and excitation frequency for stress measurement by using the acoustoelastic effect of ultrasonic guided wave.