列车外圆弹簧疲劳损伤的非线性超声测试

进行了列车外圆弹簧在疲劳载荷作用下所产生损伤的非线性超声测试。对列车外圆弹簧进行疲劳加载,利用专门的非线性超声测试系统激发和接收透过弹簧的超声纵波。在相应的信号处理后,建立了声学非线性系数与弹簧疲劳次数之间的关系。实验结果表明,当疲劳次数小于150万次时,由于弹簧材料内部位错、滑移带等微观缺陷还没有形成足以产生显著非线性的积累,该非线性系数增长不明显;当疲劳次数达到150万次至300万次之间的疲劳响应期时,非线性系数增加明显,表明弹簧材料的内部损伤快速增加;当疲劳次数超过300万次时,弹簧材料的内部损伤积累速度减缓,非线性系数增加放缓。该研究表明列车外圆弹簧的疲劳损伤程度与其声学非线性系数直接相关,利用该方法可以为材料和结构早期力学性能退化的检测和评价提供一种有效的途径。

Non-destructive evaluation of fatigue damage of train spring using nonlinear ultrasonic method

Non-destructive evaluation of fatigue damage of train spring was carried out by using nonlinear ultrasonic method.Using the nonlinear ultrasonic measurement system,longitudinal ultrasonic wave was excited and acquired after propagating through the train spring under fatigue load.The relationship between the nonlinearity parameter and fatigue cycles was established after signal process for the received ultrasonic waves.Experimental result shows that increase of the nonlinear parameter was relative slow when the fatigue cycle was less than 150 million times because the micro-structure is not sufficient enough to have obvious nonlinear accumulation on ultrasonic waves.When the fatigue cycle was between 150 and 300 million times,the nonlinear parameter increased obviously with the fatigue cycle,which showed that fatigue damage aggravates during this period.Increase of the nonlinear parameter slowed down when the fatigue cycle was more than 300 million times.This research demonstrates that fatigue damage of train spring is closely related to the nonlinear parameter,and it is expected to provide a promising way for the characterization of material fatigue damage and degradation effectively in a nondestructive way.