Technical Diagnostics and Non-Destructive Testing, 2024, №02



2024 №02 (04)

DOI of Article 10.37434/tdnk2024.02.05

2024 №02 (06)

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Technical Diagnostics and Non-Destructive Testing #2, 2024, pp. 34-40

Detection of fatigue cracks in the fillet zone of steel blades of industrial gas turbines using EDDY current method

V.M. Uchanin¹, D. Nardoni², P. Nardoni²

¹G.V. Karpenko Physico-Mechanical Institute of NASU. 5 Naukova str., 79060, Lviv, Ukraine. E-mail: vuchanin@gmail.com
²I&T Nardoni Institute, Via della Cascina Pontevica, 21, 25124, Brescia, Italy. E-mail: nardoni.campus@gmail.com

The results of experimental investigations needed for the development of an effective eddy current technique for detection of the fatigue cracks originated in the critical fillet zone of gas turbine blades from ferromagnetic steels are discussed. The proposed inspection technique is based on using selective eddy current probes of double-differential type, which can ensure a high sensitivity when the clearance between the probe operational surface and the blade surface in the fillet zone is changed during the scanning. Experimental investigation of signals of eddy current probe of MDF 0501 type (operational surface diameter of 5 mm) allowed minimizing the lift-off influence by selecting the optimal operating frequency and the scanning parameters of the inspected zone. The proposed technique effectiveness was confirmed with the application for a real gas turbine blade with a 2 mm long and 0.2 mm deep artificial defect in the fillet zone, which characterizes the sensitivity threshold in accordance with the technical assignment. The developed technique has been used with success also during its trials in the power industry plants. 20 Ref., 9 Fig.
Keywords: gas turbine blade, fillet zone, eddy current probe, operation frequency

Received: 11.04.2024
Received in revised form: 10.05.2024
Accepted: 12.06.2024

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