汽轮机轮缘超声相控阵检测中缺陷方向识别

利用超声相控阵检测系统对含有裂纹缺陷的外包菌型低压汽轮机叶轮圆盘实验试块进行检测.针对超声波脉冲反射法中缺陷方向难以确定,尺寸容易误判等问题,提出一种频谱分析方法,研究线状缺陷方向变化对于超声回波的影响.对于3种倾斜角度的裂纹缺陷回波信号,分析其功率谱并进行小波包的分解和重构,用"频率-能量"的方法提取各方向缺陷回波信号的能量特征.实验结果表明,各方向缺陷回波信号的能量特征差别明显,并绘制出声束轴线与缺陷的夹角和高频带所占能量之间关系曲线.该方法实现了缺陷方向的识别,并为后续线状缺陷的准确定量提供依据.

Recognition of Defect Direction in Ultrasonic Phased Array Testing of Turbine Disc Rims

Ultrasonic phased array inspection system was used to test straddle mount-type low-pressure turbine disc mockup which contains several crack defects. To solve the directional uncertainty of defect and the erroneous judgment of defect size based on ultrasonic pulse reflecting technique, a spectrum anal- ysis method to study the impact of linear defect orientation on the ultrasonic echo signals of defects was proposed. The power spectra of the echo signals of crack defects with three different orientations were ob- tained. Then the signals were decomposed and reconstructed by wavelet packet transform, and the energy features of these signals were extracted by the ＂frequency-energy＂ method. The results indicate that the features of the echo signal of crack defects with various orientations have apparent differences, and the re- lationship between high-frequency energy and the angle between acoustic beam and defect was drawn. This method can realize the recognition of defect direction, which provides a basis for quantitative re- search on linear defects.