Affiliations: [a] IT-based Realtime NDT Center, Chosun University, Gwangju, Republic of Korea | [b] Department of Defense Science and Technology, Gwangju University, Gwangju, Republic of Korea | [c] Korea Electric Power Research Institute, Daejeon, Republic of Korea
Correspondence:
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Corresponding author: Jinyi Lee, IT-Based Real-time NDT Center, Chosun University, Gwangju, 61452, Republic of Korea. E-mail: jinyilee@chosun.ac.kr
Abstract: A nondestructive testing device, consisting of a scanner and signal processing circuits was developed to detect cracks in turbine disk roots. The scanner consists of a longitudinal feeder and a fir-tree-shaped sensor probe. The feeder inserted the sensor probe along the grooves of the turbine blade attachment. Meanwhile, permanent magnets were placed in opposite direction, to generate a closed magnetic field between the magnetic sensors located on the crests of the sensor probe. The fatigue crack in the turbine disk root occurred in the circumferential direction of the turbine. As a result, magnetic flux leakage was caused by disturbing the flow of closed magnetic field by permanent magnets. The magnetic flux leakage was measured by a magnetic sensor. The effectiveness of the proposed device has been verified using artificial defects introduced into the turbine disk roots by electric discharge machining.
Keywords: Turbine, disk roots, fatigue, stress, sensor array, magnetic flux leakage, residual magnetization
