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Assessment of modelling methodologies for prediction of high-temperature creep-fatigue behaviour of Alloy 617
International Journal of Pressure Vessels and Piping ( IF 3 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.ijpvp.2020.104150
G. Douzian , O. Muránsky , J.J. Kruzic , R.N. Wright , W. Payten

Abstract This study aims to assess the accuracy of various modelling methodologies in predicting creep-fatigue damage ( d c f ) and cycles-to-crack-initiation ( N i ) of Alloy 617 at 850 °C and 950 °C. In the decoupled methodologies, four creep damage models were employed: (i) the time fraction (TF), (ii) ductility exhaustion (DE), (iii) stress-modified ductility exhaustion (SMDE), and (iv) strain-energy density (SED), to capture the creep damage ( d c ) contribution to the overall creep-fatigue damage ( d c f ), while fatigue damage ( d f ) contribution was always calculated using the simple “average” approach. Furthermore, we employed Holmstrom's integrated ϕ model, which combines the d c f into a single parameter without a need of separate assessment of creep damage ( d c ) and fatigue damage ( d f ). The results show that there is no significant difference between the integrated ϕ model and decoupled creep-fatigue methodologies when the creep damage models are calibrated to creep-fatigue (CF) data. However, it is shown that the accuracy of the creep-fatigue damage ( d c f ) predictions using the decoupled approach gets significantly worse when the creep damage models are calibrated against independent creep-rupture (CR) data. It is further shown that when using DE, SMDE, SED creep damage models, the d c f predictions are arranged by strain range, suggesting that these models are better at capturing strain range variations rather than temperature changes. Based on the obtained results it is recommended that any of the employed creep damage models are all suitable for coupling with the “average” fatigue damage model when capturing the creep-fatigue behaviour of Alloy 617, as long as the employed creep damage model is calibrated directly to the experimental creep-fatigue (CF) data.

中文翻译:

评估用于预测 617 合金高温蠕变疲劳行为的建模方法

摘要 本研究旨在评估各种建模方法在预测 617 合金在 850 °C 和 950 °C 时蠕变疲劳损伤 (dcf) 和循环至裂纹起始 (Ni) 的准确性。在解耦方法中,采用了四种蠕变损伤模型:(i) 时间分数 (TF)、(ii) 延性耗竭 (DE)、(iii) 应力修正延性耗竭 (SMDE) 和 (iv) 应变能密度 (SED),以捕获蠕变损伤 (dc) 对整体蠕变疲劳损伤 (dcf) 的贡献,而疲劳损伤 (df) 贡献始终使用简单的“平均”方法计算。此外,我们采用了 Holmstrom 的集成 ϕ 模型,该模型将 dcf 组合为单个参数,而无需单独评估蠕变损伤 (dc) 和疲劳损伤 (df)。结果表明,当蠕变损伤模型被校准到蠕变疲劳 (CF) 数据时,集成 ϕ 模型和解耦蠕变疲劳方法之间没有显着差异。然而,结果表明,当蠕变损伤模型针对独立蠕变断裂 (CR) 数据进行校准时,使用解耦方法进行蠕变疲劳损伤 (dcf) 预测的准确性会明显变差。进一步表明,当使用 DE、SMDE、SED 蠕变损伤模型时,dcf 预测按应变范围排列,这表明这些模型更擅长捕捉应变范围变化而不是温度变化。
更新日期:2020-11-01
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