基于光纤F-P传感器的缺陷波极值实验研究

Extremum experimental study of defect echo base on non-contact optical fiber F-P Laser

基于光干涉原理确定初始Fabry-Perot(F-P)腔长度,设计一光纤F-P干涉仪,建立光纤F-P激光超声实验装置,用于试样表面缺陷的非接触式检测。结果表明,激发源、传感系统及缺陷位置一定时,直接表面波的幅值和出现时间及反射回波的出现时间基本不变;缺陷的宽度、深度一定时,缺陷越长,缺陷反射波的幅值越大;缺陷尺寸一定,缺陷长度方向垂直激发源与传感器连线时,缺陷反射波幅值最高,随着倾角减小,幅值逐渐降低,平行时幅值最小。

In this paper,the length of Fabry-Perot cavity is obtained based on interference principle of light.An optical fiber F-P interferometer is designed. The contactless type laser ultrasound experimental devices of optical fiber are established,using for detecting surface defects.The results show that when the locations of the excitation source and the sensor and the defects are settled, the direct generated surface waves and reflection surface waves achieve at the same time.And the amplitude of direct generated surface waves remain basically unchanged.With the constant length and depth of the rectangle defect,the longer the length of the defect is,the larger the amplitude of the reflected wave is;with the constant length,depth and width of the defect,the amplitude of the reflected wave is the largest when the excitation source is perpendicular to defect;the amplitude lowers gradually with the decreasing of rake angle.Until the excitation source is parallel to the defect, the amplitude is lowest.