管道低频弯曲模态导波频散曲线的测定

Measurement of dispersion curve of flexural mode guided wave at low frequency in pipeline

将低频下管道的弯曲振动类比成梁的弯曲振动,采用经典梁理论计算其理论导波频散曲线;通过设置三对等间距布置的加速度传感器,测得振动信号,提取弯曲模态导波频散曲线,结果证明了该方法的有效性,且加速度传感器间的间距越大,效果更好。试验所得的频散曲线与理论频散曲线在低频段拟合较好,高频段有较大偏差,这表明经典梁理论在频率较高时误差较大。

Pipes bending at low frequency can be considered as bending beams, and thus the classic beam theory can be used to calculate the theoretical dispersion curves. By measuring the vibration along the pipe at three equally spaced locations, the dispersion curve of the flexural mode in pipes is extracted. It is also found that larger spaces show better performance. The experimental dispersion curve fits well at the low frequency, but shows a big deviation at high frequency, indicating that the classic beam theory validates at low frequency.