Detection and characterization of discontinuities in stainless steel by the laser ultrasonic synthetic aperture focusing technique
Detection and characterization of discontinuities in stainless steel by the laser ultrasonic synthetic aperture focusing technique
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激光超声合成孔径聚焦技术检测和表征不锈钢中的不连续性
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
J. Monchalin
中科院分区：
文献类型：
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作者：
M. Ochiai;D. Lévesque;R. Talbot;A. Blouin;A. Fukumoto;J. Monchalin
本文报道了一种用于检测和表征不锈钢应力腐蚀裂纹和焊接不连续的激光超声系统的性能。采用50 mJ长脉冲激光器与共焦法布里-珀罗干涉仪和合成孔径聚焦技术对弱不连续相关信号进行增强。首先，测试宽度小于0.03毫米（1.2 × 10 -3英寸），深度为0.5至5mm（0.02至0.2英寸）的应力腐蚀裂纹的不锈钢板。在合成孔径聚焦技术处理中，采用纵波和横波两种方法从表面对裂缝进行检测和表征。剪切波重建的破裂面图像提供了非常详细的分支紧密裂缝结构，与液体渗透测试的结果相当。这种出色的成像与b扫描中出现的交叉样特征有关，这些特征得到了解释和解释。其次，对焊接的不锈钢板进行测试，检测出尺寸约为1毫米（0.04英寸）的各种焊接不连续。尽管在这种情况下材料会强烈衰减超声波，但激光超声结合合成孔径聚焦技术成功地检测、定位和确定了这些不连续点的大小。这些结果与x射线计算机断层扫描结果进行了比较。
The performance of a laser ultrasonic system applied to the detection and characterization of stress corrosion cracks and welding discontinuities in stainless steel is reported. A 50 mJ long pulse laser coupled with a confocal Fabry-Perot interferometer and the synthetic aperture focusing technique are used to enhance weak discontinuity related signals. First, stainless steel plates containing stress corrosion cracks with widths of less than 0.03 mm (1.2 × 10 -3 in.) and depths ranging from 0.5 to 5 mm (0.02 to 0.2 in.) are tested. Both longitudinal and shear waves are used in synthetic aperture focusing technique processing to detect and characterize these cracks from the surface opposite cracking. Images at the breaking surface reconstructed by shear waves provide very detailed structures of branched tight cracks, which are comparable to results obtained by liquid penetrant testing. This excellent imaging is linked to the presence of crosslike features appearing in B-scans that are interpreted and explained. Secondly, a welded stainless steel plate is tested and various weld discontinuities with sizes of about 1 mm (0.04 in.) are detected. Although the material strongly attenuates ultrasound in this case, laser ultrasonics combined with the synthetic aperture focusing technique successfully detects, locates and sizes these discontinuities. These results are compared with those obtained by X-ray computed tomography.