Zhou Peng, Zhang Chu, Xu Ke, Ren Weiping
Institute of engineering technology, University of Science and Technology Beijing, Beijing 100083, China.
Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083, China.
Sensors (Basel). 2019 Aug 12;19(16):3529. doi: 10.3390/s19163529.
Ultrasonic testing is an important means to detect defacing defects, such as scratches and cracks, but when the size of these defects is smaller than the wavelength of ultrasonic waves, it is difficult to detect them using traditional methods like the pulse-echo method and broadband ultrasound attenuation method for the diffraction of ultrasonic waves at the defects. Based on the non-contact characteristic of electromagnetic acoustic transducers (EMATs), a transducer for scanning inspection was developed in this paper. The transducer was utilized to detect and measure the depth of the defacing defects on an aluminium plate based on the near-field enhancement of ultrasonic Lamb waves. The results show that the amplitude of the S0 Lamb wave experiences a large enhancement when the transducer is passed over the scratch defects and the enhancement has a clearly positive correlation with the depth of the scratch defects. When the depth increases from 0.1 mm to 0.9 mm, the amplitude of S0 Lamb waves increases from 1.13 times to 2.27 times the S0 Lamb waves received on the aluminium plate without defects. The new method can be utilized to detect the defacing defects on the aluminium plate and get better detection effects than the traditional methods without analyzing the relatively small reflection waves.
超声检测是检测诸如划痕和裂纹等表面损伤缺陷的重要手段，但是当这些缺陷的尺寸小于超声波的波长时，使用传统方法如脉冲回波法和宽带超声衰减法，由于超声波在缺陷处的衍射，很难检测到它们。基于电磁超声换能器（EMAT）的非接触特性，本文研制了一种用于扫描检测的换能器。该换能器基于超声兰姆波的近场增强效应，用于检测和测量铝板上表面损伤缺陷的深度。结果表明，当换能器扫过划痕缺陷时，S0兰姆波的幅值有很大增强，且这种增强与划痕缺陷的深度呈明显正相关。当深度从0.1mm增加到0.9mm时，S0兰姆波的幅值从无缺陷铝板上接收到的S0兰姆波的1.13倍增加到2.27倍。该新方法可用于检测铝板上的表面损伤缺陷，且无需分析相对较小的反射波，比传统方法具有更好的检测效果。
