Issue << content << Aircraft-Engines. Eddy Current Testing of High Pressure Turbine Disc Hub


2015. . No. 1(67) - Mar 2015, pp. 14-16

Aircraft-Engines. Eddy Current Testing of High Pressure Turbine Disc Hub

V. A. Syasko, P. V. Solomenchuk, A. I. Vishnevskiy

At OAO “Permskiy Motorny Zavod” (“Perm Engine Company”) the technological need for eddy current testing of subsurface layer of high-pressure turbine (HPT) disc hub has arisen. Parameters of target defects: the length and depth are 0.38 mm each, the width is about 1 μm. The flaw detector “CONSTANTA VD1” with the probe PF-G2-4-Ti is offered to use as an inspection instrument. The maximum depth of defect location at which a defect can be detected by the flaw detector is analytically calculated and equal 0.675 mm. Eddy current probe (ECP) impedance plain signals are analyzed. The main dependences of ECP signals on parameters of extended subsurface defects are defined.
The finite element model of the probe and the test object containing a surface defect of finite length is made. Also the colour defectogram is made. For confirmation of theoretical calculations the reference test piece has been made, the technology of its manufacturing is described. The reference test piece was scanned by the probe PF-G2-4-Ti; the indications of the flaw detector "CONSTANTA VD1" matched the calculated value, which confirms relevance of the model.
The finite element model of the probe and the test object containing subsurface defect of finite length is made. The influence of the defect length and location depth on the ECP signals has been researched; calculated indications of the flaw detector are provided.
The testing method of a HPT disc hub when ECT is fixed on a cutter-hold head of a T-lather which rotates HPT disc is offered. Testing has been carried out after the hub is being finally finished. Based on the simulation results and experimental researches the criterion of the defect existence is offered – 30 μm indication of the flaw detector. Application of finite element modelling enable reference test pieces quantity and experimental researches to be reduced as well as the cost and delivery time of NDT equipment.
Keywords: eddy current testing, subsurface defect, high pressure turbine disc, finite element modelling
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