Defects such as cracks can cause dangerous damage to the metal structure and may lead to structural collapses. Cracks can exist in various shapes and sizes where they can start to develop from small scale lower than 1 mm and spread to contribute to the complete fracture of components. Hence, early discovery and monitoring of any cracks in their early stage are crucial to prevent any sudden fatal accidents in the future. This work presents the study and detailed analysis of an ECT probe’s development based on AMR sensors to identify sub-millimeter surface cracks in galvanized steel plates. The probe consists of an excitation coil that induces an eddy current in sample plates and two AMR sensors that detect the differential eddy current-induced magnetic response. A phase-sensitive detection technique with a lock-in amplifier is used to evaluate the magnetic field distribution detected by the AMR sensors. The measured magnetic responses are classified to the depth, width, length, and complex shapes of artificial slits, and the probe is used to perform line scans and 2-D map scans above the slits’ positions. The probe was able to characterize slits with a depth and width as low as 210 and 50 µm, respectively, by using an excitation current of 4 mA at 1 kHz. The slit orientations that were perpendicular to the differential direction of the AMR sensors were clearly visualized, with their estimated lengths showed a good correlation with the physical slit lengths. In the future, the developed system can be expected to help towards the development of a more sophisticated crack detection system where real-time inspections can be realized and applied in various fields.

裂缝等缺陷会对金属结构造成危险的损坏，并可能导致结构倒塌。裂纹可以以各种形状和大小存在，它们可以从小于 1 毫米的小范围开始发展并扩散，从而导致部件完全断裂。因此，及早发现和早期监测任何裂缝对于防止未来发生任何突发的致命事故至关重要。这项工作介绍了基于 AMR 传感器的 ECT 探头开发的研究和详细分析，以识别镀锌钢板中的亚毫米表面裂纹。探头由一个励磁线圈和两个 AMR 传感器组成，该线圈在样品板中感应出涡流，以及两个 AMR 传感器，用于检测差分涡流感应的磁响应。带有锁定放大器的相敏检测技术用于评估 AMR 传感器检测到的磁场分布。测量的磁响应被分类为人工狭缝的深度、宽度、长度和复杂形状，并且探针用于在狭缝位置上方执行线扫描和二维地图扫描。通过在 1 kHz 下使用 4 mA 的激励电流，该探头能够分别表征深度和宽度低至 210 和 50 µm 的狭缝。垂直于 AMR 传感器差分方向的狭缝方向清晰可见，其估计长度与物理狭缝长度显示出良好的相关性。将来，