Theoretical and experimental investigations, including fracture tests, acoustic emission (AE) studies, fractography, micro-sclerometric analyses, and spectral/chemical analyses of specimens, have established the possibility of revealing, recognizing in-service acquired, age-related, and prefabricated flaws based solely on AE data. Results show a linear dependence between AE and mechanical deformation power of steel specimens in original and creep stage 3a-3b conditions, decreasing fracture load and J1c value for aging steel, creep processes at stage 3a-3b having J-integral value below 0.05J1c, possibility of assessing and distinguishing different flaw development stages with ≥87% accuracy, revealing zones of tough and brittle fracture, and recognizing inclusions/pre-fabricated flaws and assessing individual/interacting flaws. Experiments confirmed the absence of the Kaiser effect under repeated loading of flawed specimens and demonstrated using AE for defect revelation. Analysis showed that creep-associated AE is mainly continuous, with repeated loading decreasing burst AE contribution during plastic deformation development.

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