Tiwari Kumar Anubhav, Raisutis Renaldas
Prof. K. Barsauskas Ultrasound Research Institute, Kaunas University of Technology, K. Baršausko St. 59, LT-51423 Kaunas, Lithuania.
Department of Electrical Power Systems, Faculty of Electrical and Electronics Engineering, Kaunas University of Technology, Studentu St. 48, LT-51367 Kaunas, Lithuania.
Materials (Basel). 2018 Jul 9;11(7):1173. doi: 10.3390/ma11071173.
In this paper, the disbond-type defect presented on glass fiber reinforced plastic material is analyzed by refining the guided Lamb wave signals. A segment of wind turbine blade is considered as a test sample. The low-frequency ultrasonic measurement system is used for the non-destructive testing of the test sample using guided waves. The P-1 type macro-fiber composite transducer as a transmitter and contact-type piezoceramic transducer as a receiver are used for the testing of a sample. The disbond type defect having a diameter of 81 mm is detected from the experimental results. To improve the accuracy in locating and sizing the defects and estimation of the time of flight and phase velocity of ultrasonic guided waves in defective region, signal processing algorithm is developed by utilizing the promising properties of various ultrasonic signal processing techniques such as wavelet transform, amplitude detection, two-dimensional Fast-Fourier transform, Hilbert transform and variational mode decomposition. The discrete wavelet transform is used to denoise the guided wave signals and then, the size and location of defects are estimated by amplitude detection. The reflected wave signals from the opposite edge of the sample are removed by applying the two-dimensional Fast-Fourier transform to the experimental B-scan signal. Afterwards, variational mode decomposition and Hilbert transform are used for the phase velocity and time-delay estimation by comparing the instantaneous amplitudes of the defective and defect-free signal. The validation and the demonstration of reproducibility of the algorithm is performed by extracting the features of a 51 mm defect from another experimental B-scan.
本文通过对导波兰姆波信号进行细化分析了玻璃纤维增强塑料材料上出现的脱粘型缺陷。将一段风力涡轮机叶片视为测试样本。低频超声测量系统用于利用导波对测试样本进行无损检测。使用P-1型宏纤维复合换能器作为发射器，接触式压电陶瓷换能器作为接收器对样本进行测试。从实验结果中检测到直径为81毫米的脱粘型缺陷。为了提高缺陷定位和尺寸测量的精度以及估计缺陷区域中超声导波的飞行时间和相速度，利用小波变换、幅度检测、二维快速傅里叶变换、希尔伯特变换和变分模态分解等各种超声信号处理技术的优良特性开发了信号处理算法。离散小波变换用于对导波信号进行去噪，然后通过幅度检测估计缺陷的尺寸和位置。通过对实验B扫描信号应用二维快速傅里叶变换去除来自样本相对边缘的反射波信号。之后，通过比较有缺陷信号和无缺陷信号的瞬时幅度，使用变分模态分解和希尔伯特变换进行相速度和时延估计。通过从另一个实验B扫描中提取51毫米缺陷的特征来进行算法的验证和再现性演示。
