基于导波速度的无缝钢轨应力检测方法

Detection Method for Stress in Continuously Welded Rail Based on Guided Wave Velocity

为提高无缝钢轨应力检测精度,基于半解析有限元方法,分析应力作用下的钢轨导波模态传播规律,提出最优导波模态的选取、激励与接收方法。利用希尔伯特变换及二维傅里叶变换计算目标模态群速度和相速度,提出二次加权修正方法,以降低阵列换能器单元数量对相速度计算精度的影响。以此为基础,建立不同频率导波模态的速度与应力关系,分析基于群速度、相速度的应力检测精度。研究结果表明:随着导波频率的增大,导波群速度的计算误差逐渐增大,而相速度计算误差受到的影响较小;以200 Hz低频激励导波时,需选用群速度作为钢轨应力检测参数,应力估计精度约为0.219 MPa;以2kHz中频激励或20kHz高频激励时,需选用相速度作为检测参数,应力估计精度分别约为0.638和0.012MPa。因此,在实际应用中需根据导波频率选择不同类型的速度作为检测参数估计钢轨应力。

In order to improve the detection precisionof the stress in continuously welded rail,the modal propagation laws of guidedwaves in rail under stress were analyzed based on semi-analytical finite element method,and the optimal methods were proposed for selecting,exciting and receiving guided wave modes.The group velocity and phase velocity of target modes were calculated by using Hilbert transform and 2D Fourier transform respectively,and a double weighted correction method was proposed to reduce the impact of the number of array transducer units on the accuracy of phase velocity calculation.On this basis,the relationships between the stress and velocities of guided wave modes in different frequencies were established.The accuracy of stress detection was then analyzed based on group velocity or phase velocity.Results show that,with the increase of guided wave frequency,the calculation error of group velocity increases gradually,while that of phase velocity is lessaffected.With the low frequency of 200 Hz as guided wave excitation,group velocity should be used as the detection parameter for rail stress,and the stress estimation accuracy is about 0.219 MPa.With the intermediate frequency of 2 kHzor high frequency of 20 kHz as guided wave excitation,phase velocity should be used as the detection parameter and the stress estimation accuracy is about0.638 and 0.012 MPa respectively.Therefore,in practical applications,it isnecessary to choose an appropriate type of velocity as the detection parameter to estimate rail stress according to guided wave frequency.