先进汽轮机转子蠕变疲劳交互作用下的微观不均匀形变及寿命模型

The increase of steam temperature and pressure in ultra supercritical power plants of offers a challenge for engineers and designers on structural and materials design. In this project, micro-hetegeneous deformation and life prediction of advanced steam turbine rotor under creep-fatigue interaction will be investigated to meet the requirement of long-term and reliable service of ultra supercritical power plants. The following issues will be focused in the present project: (1) Investigating the distribution and development of micro-hetegeneous structure and then clarifying the generation mechanism and evolution rule of micro-hetegeneous deformation under creep-fatigue loadings. This research can be used to describe the accumulation of time- and cyclic- dependent of micro-hetegeneous deformation. (2) Investigating the effects of control mode and micro-hetegeneous deformation on the creep or fatigue damage model and damage summation rule. At last, a non-linear damage summation rule considering the effects of micro-hetegeneous deformation is proposed in this research to describe the creep fatigue interaction. (3) Modeling the evolution of dislocations and its interaction during creep fatigue loadings using a dislocation cell structure with the combined analysis of microstructure and dislocation mechanics. The dislocation based interaction mechanism between creep and fatigue damage can be developed. In this interdisciplinary program, the mechanical, physical and material analyses were included. This project could provide some important insights on the improvement of the long-life design and manufacturing of the key components in advanced power plant. The findings are also helpful to the development of microplasticity and non-linear damage summation theory.

面向超超临界汽轮机转子长周期可靠运行的需求，针对其高温部件在低载下产生的微细观不均匀形变及蠕变疲劳交互作用展开研究。主要内容包括：（1）研究蠕变和疲劳载荷下汽轮机部件在微细观尺度下组织和变形异质性的分布及演化规律，揭示低载荷下微细观不均匀变形来源的物理机制，实现其循环和时间累积过程的科学描述；（2）系统研究载荷控制模式和不均匀形变累积对蠕变和疲劳损伤描述方法及两者耦合竞争效应的影响，形成虑及不均匀形变累积的蠕变疲劳损伤的非线性累积模型。（3）基于位错力学和微观观察分析，定量描述蠕变和疲劳中位错等微结构演化的交互作用过程，形成基于位错理论的蠕变疲劳交互作用判定准则。本项目的开展将为电站等重大装备高温部件的蠕变疲劳损伤评估提供科学支持，同时为推动微塑性及非线性损伤累积理论的进一步发展提供帮助。

服役状态下的高温部件实际承受较低的载荷水平，基于传统的高温度、大应力的加速寿命模拟和试验方法得到的寿命模型与实际部件寿命损耗的物理过程存在较大出入，究其原因在于其并没有考虑低载荷、长时高温环境下部件损伤过程与短时加速试验之间存在的差异性。基于此，本项目围绕着在高温低载荷下产生的微观不均匀形变展开研究，阐明了其带来的特有力学响应及损伤行为。研究内容和取得的主要成果包括：揭示了汽轮机部件在微细观尺度下组织和变形异质性的分布及演化规律，阐明了低载荷下微细观不均匀变形来源的物理机制，基于塑性理论构建了微观本构模型，实现了虑及不均匀形变的循环塑性的科学描述。提出了虑及不均匀形变和载荷控制模式的寿命预测模型，探讨了两者对构件损伤机制及循环塑性变形的影响规律。基于位错力学、晶体塑性理论、微观观察和理论分析相结合的方法，形成了基于位错理论的循环塑性物理模型，实现了高温循环变形过程中的宏观响应及微结构演化的定量描述。最后，通过数值计算并试验验证了奥氏体不锈钢在结构不连续部分的非均匀形变场，并基于此提出了修正的寿命模型，为不均匀变形理论的应用提供了技术基础。本项目的成果将为电站等重大装备构件的损伤评估提供了科学支持，对重新认识循环塑性变形的内在本质及力学行为的跨尺度关联提供了新思路。