Research Of Scanning Eddy Current Testing Technology For The Defects On Aircraft Turbine Blades

As one of the most important parts in the aircraft engine, the aero turbine blade needs to be able to withstand corrosion, oxidation, wear and a variety of loads generated by the engine's high speed operation. This requires the aircraft turbine blades to satisfy special shape and the manufacturing process. Test must be finished before the engine is running, in order to confirm that the blades does not contain any defects which can cause the blade failure. Based on the analysis of aircraft turbine blades main failure forms, combined with the conditions, geometry, material characteristics of the blade, eddy current testing technology, as one of the electromagnetic nondestructive testing technologies, is chosen as the detection means for the aircraft engine blade in this paper.After preliminary explanation of the theoretical basis of eddy current testing, a kind of traditional differential simulative eddy current sensor has been designed and produced, including the structure and circuit of the sensor. Multiple sets of testing experiment for aluminum plate have been finished by this sensor. By analyzing the test results of defects with different dimension and posture, we not only verified the performance of the sensor, but also summarized the influence of the defects dimensions and posture. The dependencies of traditional different eddy current sensor for the direction of discontinuity defects within the object has been proved.Based on the traditional differential eddy current sensor, a new kind of orthogonal rotating excitation field eddy current sensor with 2 plus reverse connected excitation coil has been proposed. The experiment mentioned before is repeated, and the results verify the detection ability for crack defects of this new sensor. After comparison and analysis of the results of these 2 kind of sensors, the compensation ability of the new sensor for the influence of crack posture of eddy current testing results has been proved. This means using the new sensor can reflect the dimension of crack defects with higher accuracy, higher testing efficiency and higher detection rate.The concept of automated scanning eddy current testing has been proposed with the advantage of the new type of sensor and manipulator. The test results are not ideal because of the influence of reverse modeling, clamping, the size of the probe etc. But the automation testing experiment for the profile modeling blades with simple geometric shape proved the possibility of automated scanning eddy current testing. Expectation for the composite nondestructive testing technology has been proposed by the fusion of another nondestructive testing technology such as ultrasonic testing.