纳入性能不匹配拘束效应焊接接头蠕变-疲劳断裂寿命评估方法研究

重大高温装备正面临柔性智能化运行和长周期安全可靠运行的需求，负荷多变使得高温焊接装备将承受严重蠕变-疲劳复合载荷，目前针对蠕变-疲劳交互作用下焊接接头断裂评估尚未建立完善的理论基础和安全评估方法，无法满足重大高温装备自主设计和制造需求。本项目围绕国产新一代马氏体耐热钢G115焊接装备，研究不同控制机制下焊接接头蠕变-疲劳交互作用测试和计算方法，发展反映蠕变-疲劳变形与损伤交互作用的统一循环粘塑性损伤理论；研究考虑性能失配和拘束效应的高温断裂参量表征方法；探明残余应力在循环载荷下释放机制和影响作用；揭示焊接接头性能不匹配、拘束效应、残余应力和交互作用对蠕变-疲劳裂纹扩展的影响规律，提出纳入以上断裂因素的蠕变-疲劳裂纹扩展评估方法。通过本项目研究，为能源领域重大高温焊接装备蠕变-疲劳断裂评估提供科学支持，同时为推动我国高温结构安全评定标准的制定提供科学依据。

The challenges of heavy high temperature components are to meet the flexible and intelligent operational conditions and the long-term reliability and safety operation. This leads to much severer creep-fatigue interaction phenomena due to the variation of loading capacity. However, the current theory and structural integrity approaches to predict the facture mechanism and failure life for welded joint components under the creep-fatigue interaction need to be studied and developed to meet the independent design and manufacturing requirements in China. In this project, the welded components made from new heat resistant G115 steel developed in China are focused. The modified testing and characterization approach for the intensity of creep-fatigue interaction under different control modes will be studied. Then, the cyclic mechanical properties and damage evolution mechanism of welded components will be studied and thus a new unified cyclic viscoplastic constitutive model coupled with non-linear damage accumulation considering the interaction between deformation and damage in creep-fatigue regimes will be established. Furthermore, new high temperature fracture parameters considering the mismatch and constraint effect will be developed and the relaxation mechanism of residual stress and its role on the crack growth behavior will be revealed. Moreover, the challenges of the properties gradient of micro zone across the welded joint, the constraint, the residual stress relaxation rules and the intensity of creep-fatigue interaction on the crack growth behavior will be solved to modify the life prediction approaches considering the mentioned factors. This research will provide a theoretical foundation and scientific basis for the creep-fatigue fracture evaluation approach of the heavy high temperature welded components in energy filed, and Chinese national standards and codes of high temperature structural integrity.