PSI - Issue 33

ScienceDirect Available online at www.sciencedirect.com cienceDirect Structural Integrity Procedia 00 (2019) 000–000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000–000 Available online at www.sciencedirect.com Procedia Structural Integrity 33 (2021) 491–497

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© 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 the scientific committee of the IGF ExCo Abstract The novel destructive method, which is based on enlarging of initial cold-expanded hole diameter, is developed for quantitative assessment of fatigue damage accumulation. The secondary hole diameter increments in principal strain directions are measured at different stages of low-cycle fatigue. These data offer construction of normalized dependencies of principal residual strains, related to the secondary hole diameter, against of lifetime percentage, thus providing a explicit form of the damage accumulation function. These functions are obtained for mandrel entrance and exit side. Obtained information reveals peculiarities of damage accumulation depending on residual stress level. The results also demonstrate how stress ratio influences on the damage accumulation process under low-cycle fatigue conditions. Keywords: Damage accumulation; Low-cycle fatigue; Cold-expanded hole; Secondary hole drilling 1. Introduction The cold expansion process reliably leads to enhance the fatigue life of aircraft structures with fastener holes as it was shown by Reid (2014). Optimal design of such joints must take into account fine nuances of local deformation process caused by low-cycle fatigue. Quantitative description of damage accumulation is the essential step in this way. The novel method based on preliminary low-cycle fatigue loading of specimens with holes and inserting a sequence of narrow notches under constant external load has earlier been proposed by Matvienko et al. (2019, 2020). Abstract The novel destructive method, which is based on enlarging of initial cold-expanded hole diameter, is developed for quantitative assessment of fatigue damage accumulation. The secondary hole diameter increments in principal strain directions are measured at different stages of low-cycle fatigue. These data offer construction of normalized dependencies of principal residual strains, related to the secondary hole diameter, against of lifetime percentage, thus providing a explicit form of the damage accumulation functi n. These functions are obtained for mandrel entra ce and exit side. Obtaine information reveals peculiarities of damage accumulation depending on residual stress level. The results also demo strate how stress ratio influences on the damage accumulation process under low-cycle fatigue conditions. Keywords: Damage accumulation; Low-cycle fatigue; Cold-expanded hole; Secondary hole drilling 1. Introduction The cold expansion process reliably leads to enhance the fatigue life of aircraft structures with fastener holes as it was shown by Reid (2014). Optimal design of such joints must take into account fine nuances of local deformation process caused by low-cycle fatigue. Quantitative description of damage accumulation is the essential step in this way. The novel method based on preliminary low-cycle fatigue loading of specimens with holes and inserting a sequence of narrow notches und r constant external load has earlier be n proposed by Matvienko et al. (2019, 2020). Corresponding author. Y. Matvi nko, T l.: +7-916-100-91-55. E-mail address: ygmatvienko@gmail.com IGF26 - 26th International Conference on Fracture and Structural Integrity Low-cycle fatigue damage accumulation near cold-expanded hole IGF26 - 26th International Conference on Fracture and Structural Integrity Low-cycle fatigue damage accumulation near cold-expanded hole by secondary hole drilling data Yu. Matvienko a , V. Pisarev b , S. Eleonsky b a Mechanical Engineering Research Institute of the Russian Academy of Science, 4 Maly Kharitonievsky Pereulok, 101990 Moscow, Russia b Central Aero-Hydrodynamics Institute named after Prof. N.E. Zhukovsky (TsAGI), 1 Zhukovsky Street, Zhukovsky, 140180 Moscow Region, Russia by secondary hole drilling data Yu. Matvienko a , V. Pisarev b , S. Eleonsky b a Mechanical Engineering Research Institute of the Russian Academy of Science, 4 Maly Kharitonievsky Pereulok, 101990 Moscow, Russia b Central Aero-Hydrodynamics Institute named after Prof. N.E. Zhukovsky (TsAGI), 1 Zhukovsky Street, Zhukovsky, 140180 Moscow Region, Russia

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 the scientific committee of the IGF ExCo 10.1016/j.prostr.2021.10.056 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 Statement: Peer-review und r responsibility of the scientific committee of the IGF ExCo 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 Statement: Peer-review under responsibility of the scientific committee of the IGF ExCo Corresponding author. Y. Matvienko, Tel.: +7-916-100-91-55. E-mail address: ygmatvienko@gmail.com