钢轨轨底垂直振动模式导波检测技术的实验研究

现有铁路钢轨超声探伤车技术无法检测线路钢轨轨底缺陷,给铁路运输安全带来很大隐患.本文开展了钢轨轨底超声导波传播特性和垂直振动模式导波检测技术研究,采用半解析有限元方法分析了我国60型钢轨轨底的各振动模态导波频散曲线和波结构.应用模态锤技术对自由状态钢轨轨底垂直振动模态导波传播特性进行了实验测量,结果表明,在0～100kHz频率范围内,钢轨轨底垂直振动模态优势模式与厚度为14 mm板中的A0模式兰姆波具有等效性.进一步研究了激励频率、激励脉冲周数、传播距离对轨底垂直振动模态导波传播的影响,设计了导波斜探头,选择合适的参数在钢轨轨底激励出垂直振动模态导波并检测出了轨底的人工缺陷.本文的研究结果为线路钢轨轨底的导波检测技术奠定了一定的基础.

Experimental Investigation on Guided Wave Detection Technology for Rail Bottom Vertical Vibration Mode

Existing railroad rail ultrasonic testing car equipped with special transducer such as wheel probe is blind to the defects in rail bottom; which is a great hidden danger for rail transport safety. Therefore, investigation on propagation characteristics of ultrasonic guided waves in rail bottom and guided wave inspection technique based on vertical vibration mode was carried out. At first, the dispersion curve and wave structure of guided wave propagating in 60# rail bottom in various vibration modes were numerically calculated by using semi-analytical finite element method. Secondly, the propagation characteristics of guided wave in vertical vibration mode for rail bottom in unrestrained state were experimentally analyzed by model hammer technology. Results show that within 0~100kHz frequency range, the propagation characteristics of dominant guided wave vertical vibration mode in rail bottom are very similar to that of A0 mode of Lamb waves in a 14mm thick plate. Furthermore, dominate influence factors concerned to guided wave propagation in vertical vibration mode in rail bottom, such as excitation frequency, excitation pulse oscillate cycles and propagation distance were investigated. A guided wave angle probe was self-designed and appropriate parameters were select, then, the artificial cracks in rail bottom were successfully detected by vertical vibration guided waves. Above results provide a basis of nondestructive testing technique for rail bottom based on guided waves in vertical vibration mode.