多模非线性超声相控阵成像检测评析

Evaluation of Multi-mode Nonlinear Ultrasonic Phased Array Imaging Detection

闭合裂纹的无损评价是超声检测最具挑战性的问题之一。本文评析用纵波(LL)和变型横波(LS)的次谐波对裂纹作相控阵测评的成像能力。成像算法制定后,将该法用于有复杂分支的应力腐蚀裂纹。结果表明:用LL次谐波成像,发现有分支应力腐蚀裂纹其声显示较少;而用LS次谐波成像,发现有分支应力腐蚀裂纹有多重声显示,且分辨率较高。重要的是,LS次谐波图像能有效地显示出LL次谐波图像中未显示出的许多信息。这表明,同时使用LL和LS次谐波图像,可使次谐波相控阵裂纹测评方法更完善。

Nondestructive evaluation of closed cracks is one of the most challenging issues in ultrasonic testing.This article assessed the imaging capabilities of phased array for crack evaluation with LL and mode-converted shear(LS)subharmonic waves.After formulating the imaging algorithm,this method was applied to a complexly branched stress corrosion crack(SCC).As a result,a few responses of the branched SCC were observed in the LL subharmonic image,whereas more multiple responses of the branched SCC with higher resolutions were observed in the LS subharmonic image.Importantly,the LS subharmonic image successfully visualized a lot of responses that were not visualized in the LL subharmonic image.This suggests that the use of both LL and LS subharmonic images will make the technology of subharmonic phased array for crack evaluation more robust for practical application.