AccScience Publishing / IJOCTA / Volume 16 / Issue 5 / DOI: 10.36922/IJOCTA026270148
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RESEARCH ARTICLE

Perceived effects of stress ratio and microstructural heterogeneity on fatigue life through damage accumulation and crack nucleation: A PLS-SEM study of practising engineers in Saudi Arabia 

Shaher Alshammrei1 Sidra Ghulam Muhammad2*
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1 Department of Mechanical Engineering, College of Engineering, University of Ha’il, Ha’il , Saudi Arabia
2 National Business School, University of Faisalabad, Faisalabad, Punjab , Pakistan
IJOCTA 2026, 16(5), 026270148 https://doi.org/10.36922/IJOCTA026270148
Received: 5 July 2026 | Revised: 22 August 2026 | Accepted: 1 September 2026 | Published online: 21 September 2026
© 2026 by the Author(s). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution -Noncommercial 4.0 International License (CC-by the license) ( https://creativecommons.org/licenses/by-nc/4.0/ )
Abstract

Fatigue-related failures are an important limitation on the service life of metallic components subjected to cyclic loading in aerospace, defence, petroleum, and power-generation applications in Saudi Arabia. Guided by continuum damage mechanics, this research examined a mediated moderation model to determine how practising engineers perceive the effects of stress ratio (SR) and microstructural heterogeneity (MH) on fatigue life (FL). The study also examines how damage accumulation (DA) and crack nucleation (CN) mediate these relationships. In addition, the study tests for the moderating effect of operating temperature (TEMP) on each of the two sequential paths: DA → CN and CN → FL; TEMP is modelled as a moderator of these transitions, not as a stage within the serial pathway. A survey was conducted among 410 senior materials and mechanical engineers working for Saudi Arabian companies in the aerospace, defence, petroleum, power-generation, and heavy-industry sectors within the context of the Vision 2030 localisation strategy. Partial least squares structural equation modelling was used to analyse the data and to test for conditional indirect effects and the index of moderated mediation. All but one tested hypothesis was supported; the effects of SR and MH on FL via DA/CN were nearly four times larger across the temperature range examined. Additionally, the proposed model accounts for 35.4% of the variance in perceived FL. All six constructs are latent variables measured by seven-point Likert items capturing the judgements of experienced engineers; none is a physical quantity obtained from fatigue testing or material characterisation. The findings therefore describe perceived relationships among these constructs and constitute statistical evidence from expert judgement rather than experimental validation of the underlying fatigue mechanisms.

Graphical abstract
Keywords
Fatigue life
Stress ratio
Microstructural heterogeneity
Damage accumulation
Crack nuclea-tion
Moderated serial mediation
PLS-SEM
Expert perception
Funding
None.
Conflict of interest
The authors declare no conflict of interest.
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An International Journal of Optimization and Control: Theories & Applications, Electronic ISSN: 2146-5703 Print ISSN: 2146-0957, Published by AccScience Publishing