中文摘要：

由滚动接触疲劳引起的钢轨踏面斜裂纹已成为目前高速铁路在役钢轨无损检测中的重要问题,现有的铁路钢轨超声探伤车（仪）难以检测此类缺陷。采用低频超声表面波方法,沿钢轨长度方向对钢轨踏面斜裂纹进行B扫成像检测。由于钢轨轨头为带圆弧边的矩形截面,在钢轨表面激发和传播的低频表面波已不再是经典的Rayleigh波,而是一类导波,导波的多模式对表面波成像检测形成了干扰。为减小干扰,将空间平均技术应用于钢轨踏面斜裂纹的表面波B扫成像。对人工缺陷试块和钢轨试样的B扫成像实验结果表明,利用空间平均技术能有效的抑制此类干扰,提高信噪比,可对钢轨踏面斜裂纹作快速检测和定位。

英文摘要：

Rail tread tilted cracks induced by rolling contact fatigue are common problems in nondestructive testing of modern high speed railways. Existing railway rail ultrasonic flaw detection vehicle （instrument） has difficulties to detect such defects. An imaging method based on low frequency ultrasonic surface wave B-scan along rail length direction is presented in this paper to detect rail tread tilted cracks. Because railhead has a rectangular cross section with circular edge, the low-frequency surface wave propagating along the railhead is no longer classical Rayleigh wave, but a class of guided wave. The multi-mode characteristics of guided wave interfere the surface wave B scan imaging detection of tilted cracks. To suppress this kind of interference efficiently, spatial averaging method is used in surface wave B-scan imaging detection of rail tread tilted cracks. The B-scan imaging experiment results for artificial defect specimen and rail sample show that spatial averaging method can effectively suppress such interference and improve signal to noise ratio, and this method can rapidly detect and locate the tilted cracks on railhead.