Methods of evaluating low-cycle fatigue of gas turbine engine parts exemplified by a high-pressure turbine cover plate

This article presents an example of calculating the durability of a real part of a gas turbine engine. The part under examination had problems in its operation due to origination of cracks, exhaustion of load bearing capacity and non-localized fracture owing to crack development arising as a result of low-cyclic fatigue of material in the inter-labyrinth zone of the part. The part design analysis carried out with the use of engineering methods in conformity with the standard procedure accepted at the time of design did not presuppose any strength problems owing to low-cyclic fatigue. Mass manifestations of the defect “crack in the radius of the deflector flange center pilot transition” called for the necessity of evaluating the safety of subsequent use of products containing these parts before they reach the end of their assigned service life. Based on the results of metallurgical studies, a conclusion of the causes of defects was made and a complex of technological measures to prevent these defects in the future was proposed. Some methods of evaluating low-cyclic fatigue are presented in the article. They are widely used in engine design and development at the present time (in the absence of a data bank on the properties of materials under the “hard” loading cycle).