<p>This study presents a fuzzy-Weibull framework for assessing the fatigue reliability of steel pipelines under both random (aleatory) and knowledge-based (epistemic) uncertainties. Existing fatigue-life evaluation methods often treat these uncertainties deterministically or rely on limited probabilistic assumptions, without providing an integrated framework that combines experimental material data, in-service loading histories, and fuzzy uncertainty modeling. The framework induces in-service random load data, experimental material properties, stress–strength interference analysis, and the fuzzification of Weibull life parameters for fatigue reliability assessment. Fuzzy membership functions for experimental Weibull fatigue-life distribution parameters are labeled low, medium, and high estimated from five years of in-service random load records and measured material properties. The findings showed that material yield strength varied between 366 and 594 MPa, producing an interference region where applied stress and material resistance overlap. The fuzzy-Weibull model estimated mean fatigue lives as 1.03 × <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$10^{9}$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mn>10</mn> <mn>9</mn> </msup> </math></EquationSource> </InlineEquation> cycles to failure of operational stresses region and 5.48 × <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$10^{5}$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mn>10</mn> <mn>5</mn> </msup> </math></EquationSource> </InlineEquation> cycles to failure for interference region, which showed good agreement with experimental S-N data. Defuzzified reliability values ranged from 0.38 to 0.46, corresponding to reliability indices of approximately 2.2 to 5.1 under operational stress levels. Within the interference region, the reliability index decreased from about − 0.6 to − 2.25 as the Weibull shape parameter increased, indicating the transition from fatigue failure to early failure. Hence, this study induced experimental and computational reliability framework based on non-deterministic techniques that provide an improved fatigue reliability prediction and integrity assessment of API grade steel pipelines.</p>

Experimental and Computational Assessment of Pipeline Fatigue Reliability Using Fuzzy-Weibull Model under Stochastic Loading with Epistemic and Aleatory Uncertainties

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发表日期：

2026年5月13日

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M. A. Khan,
S. S. K. Singh,
S. Abdullah,
A. Arifin,
M. Z. Kamardin,
M. Bashir

摘要

This study presents a fuzzy-Weibull framework for assessing the fatigue reliability of steel pipelines under both random (aleatory) and knowledge-based (epistemic) uncertainties. Existing fatigue-life evaluation methods often treat these uncertainties deterministically or rely on limited probabilistic assumptions, without providing an integrated framework that combines experimental material data, in-service loading histories, and fuzzy uncertainty modeling. The framework induces in-service random load data, experimental material properties, stress–strength interference analysis, and the fuzzification of Weibull life parameters for fatigue reliability assessment. Fuzzy membership functions for experimental Weibull fatigue-life distribution parameters are labeled low, medium, and high estimated from five years of in-service random load records and measured material properties. The findings showed that material yield strength varied between 366 and 594 MPa, producing an interference region where applied stress and material resistance overlap. The fuzzy-Weibull model estimated mean fatigue lives as 1.03 × $10^{9}$ $10^{9}$ cycles to failure of operational stresses region and 5.48 × $10^{5}$ $10^{5}$ cycles to failure for interference region, which showed good agreement with experimental S-N data. Defuzzified reliability values ranged from 0.38 to 0.46, corresponding to reliability indices of approximately 2.2 to 5.1 under operational stress levels. Within the interference region, the reliability index decreased from about − 0.6 to − 2.25 as the Weibull shape parameter increased, indicating the transition from fatigue failure to early failure. Hence, this study induced experimental and computational reliability framework based on non-deterministic techniques that provide an improved fatigue reliability prediction and integrity assessment of API grade steel pipelines.