PSI - Issue 45

Structural Integrity Procedia 00 (2022) 000 – 000 ScienceDirect Structural Integrity Procedia 00 (2022) 000 – 000

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Procedia Structural Integrity 45 (2023) 60–65 17th Asia-Pacific Conference on Fracture and Strength and the 13th Conference on Structural Integrity and Failure (APCFS 2022 & SIF 2022) Quantifying the discrepancies in measuring applied stresses using Tangent Modulus Method (TMM) Zulfiqar Ali a,* , Murat Karakus a , Giang D. Nguyen a , Khalid Amrouch b,c 17th Asia-Pacific Conference on Fracture and Strength and the 13th Conference on Structural Integrity and Failure (APCFS 2022 & SIF 2022) Quantifying the discrepancies in measuring applied stresses using Tangent Modulus Method (TMM) Zulfiqar Ali a,* , Murat Karakus a , Giang D. Nguyen a , Khalid Amrouch b,c a School of Architecture and Civil Engineering, The University of Adelaide, Adelaide, SA 5005, Australia b Australian School of Petroleum and Energy Resources, The University of Adelaide, Adelaide, SA 5005, Australia c Mohammed VI Polytechnic University, Geology & Sustainable Mining, Benguerir 43150, Morocco a School of Architecture and Civil Engineering, The University of Adelaide, Adelaide, SA 5005, Australia b Australian School of Petroleum and Energy Resources, The University of Adelaide, Adelaide, SA 5005, Australia c Mohammed VI Polytechnic University, Geology & Sustainable Mining, Benguerir 43150, Morocco Abstract The stress memory in rock under uniaxial cyclic compression is attributed to the nonlinear strains in rock due to crack initiation and propagation. When a rock is subjected to uniaxial compression, potential cracks with strengths lower than the applied stress initiates and propagates. When the specimen is unloaded and reloaded again, new cracks hardly occur until previously applied maximum stress is reached, beyond which new cracks are generated resulting in elastic strains. The tangent modulus method (TMM) is an approach commonly used to reconstruct the applied stress. This method involves plotting the incremental tangent modulus for two successive cycles against the stress, with the separation between the curves assumed to be the maximum stress previously applied. However, this method is sensitive to time and show its effectiveness under a certain range of time delay only. In this paper, we propose a modification to the TMM that eliminates the time dependency of the method. Uniaxial cyclic loading and unloading (UCLU) tests were performed on cylindrical rock specimens, and the effect of time delay on stress memory was observed. The results obtained from the modified technique indicate that the stress memory in rocks remains unaffected by time delay, contrary to the findings of the conventional TMM analysis. © 2023 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 Prof. Andrei Kotousov © 2023 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 Prof. Andrei Kotousov Abstract The stress memory in rock under uniaxial cyclic compression is attributed to the nonlinear strains in rock due to crack initiation and propagation. When a rock is subjected to uniaxial compression, potential cracks with strengths lower than the applied stress initiates and propagates. When the specimen is unloaded and reloaded again, new cracks hardly occur until previously applied maximum stress is reached, beyond which new cracks are generated resulting in elastic strains. The tangent modulus method (TMM) is an approach commonly used to reconstruct the applied stress. This method involves plotting the incremental tangent modulus for two successive cycles against the stress, with the separation between the curves assumed to be the maximum stress previously applied. However, this method is sensitive to time and show its effectiveness under a certain range of time delay only. In this paper, we propose a modification to the TMM that eliminates the time dependency of the method. Uniaxial cyclic loading and unloading (UCLU) tests were performed on cylindrical rock specimens, and the effect of time delay on stress memory was observed. The results obtained from the modified technique indicate that the stress memory in rocks remains unaffected by time delay, contrary to the findings of the conventional TMM analysis. © 2023 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 Prof. Andrei Kotousov Keywords: Stress memory, Kaiser effect, tangent modulus method, TMM,

Keywords: Stress memory, Kaiser effect, tangent modulus method, TMM,

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*Corresponding Author: Zulfiqar Ali ________

Email: Zulfiqar.ali@adelaide.edu.au

*Corresponding Author: Zulfiqar Ali

2452-3216 © 2023 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 Prof. Andrei Kotousov 10.1016/j.prostr.2023.05.014 2452-3216 © 2023 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 Prof. Andrei Kotousov 2452-3216 © 2023 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 Prof. Andrei Kotousov Email: Zulfiqar.ali@adelaide.edu.au