PSI - Issue 68

Gomez-Mancilla J / Structural Integrity Procedia 00 (2025) 000–000 St

ScienceDirect Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2025) 000–000 Available online at www.sciencedirect.com Procedia Structural Integrity 68 (2025) 1208–1215

www.elsevier.com/locate/procedia

European Conference on Fracture 2024 Novel Indicators & Nonlinear Method for Onset Damage Detection in Very High Cycle Fatigue Tests (VHCF) a Gomez-Mancilla J.C. * a Laboratorio de Vibraciones & Rotodinamica, Instituto Politecnico Nacional IPN, UPALM Lindavista CDMX, México Abstract Modern industry and demanding markets require engineering products characterizing their performance in Very High Cycle Fatigue (VHCF). An international testing standard must not be limited to the number of endured load cycles, but at a minimum, the probe’s damage onset and characterization should be detected. The author poses three criteria based on a proposed test set-up that adds another synchronous channel to the current axial (Ch1), an orthogonal bending monitoring at the probe’s tip (Ch2). The first proposed criterion uses axial response data, and its results perfectly coincide with the existing Nonlinear Acoustic Emission NAE criterion. The second relies on the bending BFSI indexes obtained from the author's proposed added monitored direction, where the damage indexes can be used to estimate the crack-like gravity. The third criterion relies on trends and application of the NAE criterion to the bending amplitude, which is more sensible than the current monitored axial vibration. Criteria 2 and 3 are impossible to achieve should the current experimental set-up not add the (Ch2) bending response. To validate, these criteria are applied to a real test using PIMM Lab sophisticated VHCF equipment yielding PSB onset detections. Further validation, XCT tomography detects intergranular microcracks extending in a zigzag pattern; this damage pattern suggests a significant advance in the material degradation due to fatigue, as PSB, microcracks near to coalesce. Previous validation results are coherent with the proposed three initial damage criteria and this work’s analyses. © 2025 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 ECF24 organizers Keywords: VHCF; test-set-up; fatigue; PSB; experiment; nonlinear acoustic emission; onset damage; damage index, STFT, vibration. 1. Introduction The bibliography lists the first book on Giga cycle fatigue written by Bathias C et al. (2006), co-authored by a pioneer of Fracture Mechanics, Prof. Paul C. Paris, during his stay at the PIMM Laboratory, ENSAM , Paris. This book is the only one published on the topic and there are only articles published in international journals. © 2025 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 ECF24 organizers

* Corresponding author. . E-mail address: gomezmancilla@gmail.com

2452-3216 © 2025 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 ECF24 organizers 10.1016/j.prostr.2025.06.189