Abstract Stresses in the steam-side oxide of boiler tubes are evaluated based on analytical derivations and numerical simulations. With only thermal strain considered, analytical solutions of stress distribution are obtained for a cylindrical geometry representative of boiler tubes and a flat-plate geometry—a typical simplification assumed in the literature to represent boiler tubes with extremely thin oxide scale. In these analytical derivations, the substrate metal has finite dimensions or is assumed to be very thick. The solutions under the approximations of flat-plate geometry and very thick substrate are employed to examine the accuracy of various approximations adopted in the literature to analyze the stress distribution in boiler tubes. For more complicated situations where the contributions from thermal strain, interface roughness, creep of the oxide and metal, and oxide growth are considered, numerical simulations are performed for a cylindrical geometry to evaluate the stress distribution in boiler tubes. The simulation results reveal that: (1) the local radial stress at curved oxide–metal interfaces is enhanced by interface roughness with implications about interfacial crack growth; (2) contrary to the general belief that creep relieves the oxide stresses, creep may actually increase the stresses in the oxide due to different creep rates of the oxide and substrate metal; and (3) the geometrically induced oxide growth strain substantially increases the magnitudes of the hoop and axial stresses in the oxide. Based on the assumption that the failure of the oxide scales is caused by crack growth which is dominated by the stress intensity factor, damage maps are plotted directly using the hoop, axial, and radial stresses as the critical variables. Our work provides a quantitative understanding of the interactions between different thermomechanochemical processes and oxide scale failure in boiler tubes. Graphic Abstract

中文翻译：

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锅炉管蒸汽侧氧化物的应力分析：热应变、界面粗糙度、蠕变和氧化物生长的贡献

摘要 基于解析推导和数值模拟，评估了锅炉管蒸汽侧氧化物中的应力。仅考虑热应变，可以获得代表锅炉管的圆柱几何形状和平板几何形状的应力分布解析解——文献中假设的典型简化代表具有极薄氧化皮的锅炉管。在这些分析推导中，基材金属具有有限尺寸或假定非常厚。平板几何和非常厚的基板近似下的解决方案用于检查文献中采用的各种近似值的准确性，以分析锅炉管中的应力分布。对于更复杂的情况，其中来自热应变、界面粗糙度的贡献，考虑到氧化物和金属的蠕变以及氧化物的生长，对圆柱形几何形状进行数值模拟以评估锅炉管中的应力分布。模拟结果表明：（1）弯曲的氧化物-金属界面处的局部径向应力因界面粗糙度而增强，对界面裂纹扩展有影响；(2) 与蠕变减轻氧化物应力的普遍看法相反，由于氧化物和基底金属的不同蠕变速率，蠕变实际上可能会增加氧化物中的应力；(3) 几何诱导的氧化物生长应变显着增加了氧化物中的环向应力和轴向应力的大小。基于氧化皮破坏是由应力强度因子主导的裂纹扩展引起的假设，使用环向、轴向和径向应力作为关键变量直接绘制损伤图。我们的工作提供了对不同热机械化学过程与锅炉管中氧化皮失效之间相互作用的定量理解。图形摘要