PSI - Issue 59

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2023) 000 – 000

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 59 (2024) 771–778

VII International Conference “In -service Damage of Materials: Diagnostics and Prediction ” (DMDP 2023) Effect of heat treatment of reconditioned shafts on resistance to crack propagation Viktor Kovalov*, Olena Berezshnaya, Valeriy Kassov, Yana Vasylchenko, Svetlana Maluhina, Maksim Berezshniy Donbas State Engineering Academy, 84313, Kramatorsk, Ukraine Abstract The article presents studies of fatigue crack formation, the rate of their growth and propagation to failure of the specimen under the action of applied static forces depending on the structure of the surface layer, including the coating applied by electro-contact surfacing, and the heat affected zone. One of the main disadvantages of almost all metal coatings applied by various methods (cladding, gas-thermal spraying, electrodeposition, electro-contact welding, etc.) is the presence of residual stresses in them, which adversely affect the fatigue strength and other mechanical characteristics of parts with coatings. Fatigue fracture is preceded by crack initiation and development, followed by brittle fracture without visible plastic deformation. When selecting materials and rational technologies for restoration and hardening by electro-contact surfacing of parts operating under cyclic loads, not only characteristics of standard mechanical properties and endurance limit of composite surfacing materials, but also resistance to crack development are of great importance. In the experimental assessment of fatigue crack growth rate, the initial data are the dependence between the change in crack length and the number of cycles of applied loads. With the appearance of a crack in the specimen, the stress field undergoes a significant change: at the crack tip there is a concentration of stresses. The method used contains two stages: fatigue crack formation, during which it is possible to measure the crack growth rate, and crack propagation until the specimen fails under the action of applied static forces. The rate of fatigue crack propagation was studied on model specimens of steel 40 and 40X, which simulated the structural state of the surface layer with a certain content of plastic phases, regulated by combined heat treatment. The studies were carried out on a hydraulic machine MUP 50 with a pulsator providing a maximum load of 0.25 MN. The loading scheme is a concentrated load creating a

* Corresponding author. Tel.: +3-809-8815-8865. E-mail address: elena.kassova07@gmail.com

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of DMDP 2023 Organizers

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of DMDP 2023 Organizers 10.1016/j.prostr.2024.04.110