The integrity of the main shaft plays a significant role in the safety of wind turbine. Stress concentration often occurs where the main shaft and the bearing are assembled in the wind turbine. The surface breaking of transverse crack on the outer circumference thus becomes a major dangerous source. In this research, a finite element (FE) model is developed to analysis the echoes on the end face, which are often confused in the identification of the crack signals. The propagation of ultrasonic waves and its reflection on the shaft boundary will be investigated in details. The relationship between the amplitude of the crack echo and the radial position of the piezoelectric transducer is explored optimized comprehensively. Then, an ultrasonic measurement methodology are established for the examination of the main shaft from the end face. A circular scanning experiment for the shaft testing on surface cracks have been implemented. The results show that the crack depth less than 5 mm can be examined, although the total size of the shaft is Φ600 mm × 1285 mm. All artificial cracks in the high-stress zone have been detected with the aid of a B-scan imaging, which reveals the position of defects. This research will provide an effective regular inspection technique for the wind turbine shaft examination.

主轴的完整性在风力涡轮机的安全中起着重要作用。在主轴和轴承组装在风力涡轮机中的地方经常发生应力集中。因此，外周上的横向裂纹的表面破裂成为主要的危险源。在这项研究中，开发了一个有限元（FE）模型来分析端面上的回波，这些回波通常与裂纹信号的识别相混淆。将详细研究超声波的传播及其在轴边界上的反射。综合探讨了裂纹回波幅度与压电换能器径向位置之间的关系。然后，建立了一种超声波测量方法，用于从端面检查主轴。已经实施了用于轴测试表面裂纹的圆形扫描实验。结果表明，尽管轴的总尺寸为Φ600毫米×1285毫米 借助B扫描成像，可以检测出高应力区域中的所有人造裂缝，从而揭示出缺陷的位置。该研究将为风机轴的检验提供有效的常规检查技术。