PSI - Issue 31

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000–000

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 31 (2021) 33–37

© 2021 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 ICSID 2020 Organizers. Abstract The blades of axial turbomachines (steam and gas turbines, axial compressors) are highly stressed by centrifugal force, temperature, and alternating fluid forces, which leads to vibrations and fatigue cracking. This requires the studious engagement of designers and technologists. In this paper, a procedure for accelerated fatigue testing of a gas turbine compressor blade based on the modified Locati method is presented. The tests were performed on a vibration shaker with the frequency that equal the blade’s first natural frequency. S-N curves were estimated according to two approximate representation namely one-slope and two-slope models. Then, the blades were tested at different stress levels starting at a level below foreseen fatigue strength at the specified fatigue life. In each loading block, a blade was subjected to 2ˑ10 7 cycles. After the first block was completed, the stress level in the second loading block was increased by 20 MPa and a new 2ˑ10 7 cycles were applied. A procedure was repeated until the blade failure occurred. It was considered that a blade has failed when its natural frequency drops by more than 2%. After the failure, the fatigue strength was calculated using Palmgren -Miner rule. © 2021 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 ICSID 2020 Organizers. Keywords: Modified Locati method, accelerated fatigue test, compressor blade r c 4th International Conference on Structural Integrity and Durability, ICSID 2020 Application of modified Locati method in fatigue strength testing of a turbo compressor blade Sanjin Braut a *, Marina Tevčić b , Mirko Butković a,b , Željko Božić c , Roberto Žigulić a a University of Rijeka, Faculty of Engineering, Vukovarska 58, 51000 Rijeka, Croatia b University of Applied Sciences, Mechanical Engineering Department, I. Meštrovi ć a 10, Karlovac, Croatia c University of Zagreb, Faculty of Mechanical Engineering and Naval Architecture., I. Lu č i ć a 5, 10000 Zagreb, Croatia

* Corresponding author. Tel.: +385 51 651 502 E-mail address: sbraut@riteh.hr

2452-3216 © 2021 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 ICSID 2020 Organizers.

2452-3216 © 2021 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 ICSID 2020 Organizers. 10.1016/j.prostr.2021.03.007