基于非线性超声混频技术的金属疲劳微裂纹实验测量

Experimental Measurements of Fatigue Micro-crack in a Metal Structure Based on the Frequency-mixing Nonlinear Ultrasonic Technique

利用RAM-5000 SNAP声学测试系统,对包含疲劳微裂纹的金属早期损伤试件进行非线性超声混频实验测量。通过双纵波对向混合模式,完成对试件沿长度方向的扫查检测。实验结果表明,两声波在微裂纹附近交汇时,所获混频非线性效应更强。混频声波,可避免系统非线性的干扰,获得更加“纯净”的信号。通过该技术不仅可以发现常规无损检测手段难以检测的微裂纹损伤,而且可以实现损伤定位,是检测结构部件中微裂纹损伤的一种可靠方法。

The Frequency-mixing nonlinear ultrasonic measurements were carried out on an early damaged metal specimen with fatigue micro-crack,by utilizing the RAM-5000 SNAP system.Based on the two longitudinal waves opposite mixing mode,the scanning tests along the length direction of the specimens were completed.The experimental results show that the nonlinear mixing effect is obviously dominant when the two ultrasonic waves meet near the micro-crack.By avoiding the interference from system nonlinearities,the technique of mixing waves can make the measured nonlinear response signals more“pure”.The nonlinear ultrasonic technology provides effective detection of the fatigue micro-crack that cannot be identified by the conventional nondestructive testing methods,and realizes the damage localization ability,which is a reliable method to detect micro-crack in structural components.