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Predicting Low-Cycle Fatigue Life Using New Energy-Based Fatigue Damage Measures
Stanisław Mroziński1, Michał Piotrowski1, Władysław Egner2
1Faculty of Mechanical Engineering, Bydgoszcz University of Science and Technology, Al. Prof. S. Kaliskiego 7, 85-796 Bydgoszcz, Poland.
Materials (Basel, Switzerland)
|January 28, 2026
Summary
This study explores energy-based methods for predicting low-cycle fatigue life in S420M steel. Anisotropy significantly reduces fatigue life, with energy-based predictions often overestimating experimental results.
Area of Science:
- Materials Science
- Mechanical Engineering
- Fatigue Analysis
Background:
- Low-cycle fatigue is critical for structural integrity.
- Predicting fatigue life is essential for material design.
- Anisotropy in materials can significantly affect fatigue behavior.
Purpose of the Study:
- To evaluate new energy-based fatigue damage measures for predicting low-cycle fatigue life.
- To compare empirical (Palmgren-Miner) and thermodynamic (Unified Mechanics Theory) approaches.
- To investigate the influence of anisotropy on the fatigue response of S420M steel.
Main Methods:
- Utilized energy accumulation graphs as a generalization of isodamage lines.
- Compared empirical Palmgren-Miner hypothesis with Unified Mechanics Theory.
- Tested S420M steel samples in orientations parallel and perpendicular to the rolling direction.
- Conducted microstructural analysis to observe anisotropy effects.
Main Results:
- Fatigue life of samples perpendicular to the rolling direction was lower than parallel samples.
- Microstructural analysis revealed banded structures in perpendicular samples due to anisotropy.
- Calculated fatigue life using Palmgren-Miner consistently exceeded experimental fatigue life.
- Unit loop energy was higher in parallel samples compared to perpendicular samples across all strain amplitudes.
Conclusions:
- Energy-based methods show potential but require refinement for accurate fatigue life prediction, especially with anisotropy.
- Anisotropy, induced by sheet rolling, significantly degrades fatigue performance.
- The empirical Palmgren-Miner hypothesis tends to overestimate fatigue life in this context.
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