Aero-engine discs are very critical parts since they are exposed to high stress and temperature during flights. Engine disc components such as bearing rings, fan and compressor discs are subjected to extensive inspections during the different manufacturing stages, including dimensional controls up to the detection of the tiniest surface flaws on rolling surfaces (bearing raceways). The forging process, with which most of these parts are formed, is a high energy process that can result in many different types of defects, some of these being near surface or surface breaking cracks. Thus, complementary NDT technologies such as ultrasonic, liquid penetrant and eddy current testing are commonly used for flaw detection on those components. However, as the shapes and materials of these parts become more and more complex, automated inspection plays a crucial role in ensuring that these parts are defect free. To overcome the above-mentioned challenges, this article demonstrates an automated eddy current solution with 3D scanning capabilities developed to inspect aero-engine forged discs.
Eddy current testing technique plays an important role in quality control of aero-engine components. When inspecting with automated eddy current scanners, surface as well as some sub-surface flaws are detected by scanning the surface of the inspected material. Such scanners are usually Cartesian scanners built with rotational axes and designed to perform high speed and repeatable nondestructive testing. However, forged discs have complex shapes with multiple surface transitions that make it difficult for simple 2-axis and rotational scanners to perform inspections of these parts. In order to achieve the desired inspection results under these circumstances, automated eddy current solution with advanced 3D capabilities needs to be used to perform full scans on aero-engine discs. Tridimensional inspection of these discs is best achieved using computer-aided design (CAD) files to perform accurate inspection in the 3D space.