Wang Zheng, Zeng Zhanhong, Song Yongfeng, Li Xiongbing
Beijing Institute of Aeronautical Materials, Beijing 100095, China.
School of Traffic and Transportation Engineering, Central South University, Changsha 410075, China.
Materials (Basel). 2022 Dec 3;15(23):8633. doi: 10.3390/ma15238633.
The roughness of a flaw's surface significantly affects the scattering behavior of ultrasonic waves. It is vital to understand the impact of roughness on flaw echoes, especially when performing ultrasonic nondestructive inspection on safety-critical components. However, the current approach for creating rough flaw models fails to reconstruct complicated cracks with secondary cracks. Here, a multi-scale distortion method is developed to generate a rough flaw by using an optical microscope image of a real flaw. The finite element (FE) is then implemented to simulate the near-surface rough flaws in nickel-based bars, which are detected by an offsetting immersion transducer with mode-converted transverse waves. Numerical results show that the randomness and complexity of flaw echoes from rough flaws are exceptionally high. The gap between the maximum and minimum normalized amplitude values of flaw echoes from a rough crack with secondary cracks can reach 7.125 dB. Meanwhile, the maximum time of flight (TOF) is almost twice as large as the minimum TOF. Therefore, the present method can generate effective rough flaw models in terms of macroscopic rough geometry and microscopic rough surface. Moreover, the impact of the rough flaw surface on the flaw echoes goes beyond amplitude changes and may make flaw location challenging.
缺陷表面的粗糙度会显著影响超声波的散射行为。了解粗糙度对缺陷回波的影响至关重要，尤其是在对安全关键部件进行超声无损检测时。然而，目前创建粗糙缺陷模型的方法无法重建带有二次裂纹的复杂裂纹。在此，开发了一种多尺度畸变方法，通过使用真实缺陷的光学显微镜图像来生成粗糙缺陷。然后实施有限元（FE）来模拟镍基棒材中的近表面粗糙缺陷，这些缺陷由带有模式转换横波的偏置浸入式换能器检测。数值结果表明，粗糙缺陷的缺陷回波的随机性和复杂性极高。带有二次裂纹的粗糙裂纹的缺陷回波的最大归一化幅度值与最小归一化幅度值之间的差距可达7.125 dB。同时，最大飞行时间（TOF）几乎是最小TOF的两倍。因此，本方法能够在宏观粗糙几何形状和微观粗糙表面方面生成有效的粗糙缺陷模型。此外，粗糙缺陷表面对缺陷回波的影响不仅限于幅度变化，还可能使缺陷定位具有挑战性。
