Damage evaluation of the power plants materials based on the AE model of material degradation under high-cyclic fatigue

Abstract

Modern mechanical engineering products are expected to have an increased lifetime at reduced cost. In order to enable this development, new and improved methods of structural materials strengthening need to be found. Mathematical modelling of the mechanical behaviour of the products in the conditions of fatigue, taking into account various operational, design and technological factors does not provide the necessary accuracy and has to be verified in long-term tests. Therefore, development of a methodology for predicting the limiting state of the structural materials under the long-term periodic load by non-destructive control methods, in particular the acoustic emission (AE) method, remains topical.Within this work, custom-designed model samples of nickel- and titanium-based alloys, as well as carbon and alloyed steel have been studied in comparison. The samples were fabricated both in standard technological process and including ultrasonic surface hardening. Features of cyclic AE characteristics that are identical for different classes of materials with different technological inheritance are described. Based on the obtained results, the relationships between the informative parameters of AE and the criteria of the limiting state of the studied materials for power plants under the high-cycle fatigue conditions are established. This enables assessment of the effectiveness of the technological measures aimed at increasing the life of parts of the power plants, based on non-destructive AE control.