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Load hold at peak stress can drastically reduce the fatigue life of Ti-6Al-4V alloys, a phenomenon known as dwell-fatigue life debit. Unlike normal fatigue, dwell-fatigue exhibits a characteristic three-stage strain accumulation curve: an initial rapid strain increase (primary), followed by a steady strain-increase (secondary), and finally an accelerated stage leading to failure (tertiary). In the current study, flat specimens made out of three distinct microstructures of Ti-6Al-4V alloys were subjected to uniaxial fatigue load with 120-second peak stress hold and 0.1 load ratio with real-time acoustic emission (AE) measurement. The microstructures, namely, equiaxed, bimodal, and lamellar, were tailored through different heat treatment procedures. Bayesian statistical analysis of AE data enabled both the detection of stage transition points using Markov chain Monte Carlo (MCMC) simulation and the selection of strain accumulation models through replica MCMC method. The results demonstrated that two change-points detected showed strong correlation with the transitions in the creep-like three-stage curve of strain accumulation. The strain accumulation behavior was successfully predicted using AE parameters. Furthermore, average frequency proved crucial in monitoring the beginning of dwell-fatigue process.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Ti-6Al-4V, Dwell-fatigue, Acoustic emission, Strain accumulation, Bayesian statistics

Date published: 2025-09-15

Publisher: Iron and Steel Institute of Japan

Journal:

• ISIJ International (ISSN: 09151559) vol. 65 issue. 10 ISIJINT-2025-110

Funding:

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.2355/isijinternational.isijint-2025-110

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Updated at: 2025-10-01 16:30:33 +0900

Published on MDR: 2025-10-01 16:23:27 +0900