低应力长寿命高温部件的蠕变本构及设计准则研究

Focused on the difficult problem of creep strength design in high temperature structures, in the present proposal, the following points will be investigated: In terms of the anatomy and microstructure analysis of the steam turbine rotor after 20-years service, the micromechanism of creep damage at low stress level will be clarified. Based on the combination of consecutive creep test and the interrupted creep test, we hope to establish an algorithm for retrieving creep damage in the long term serviced components. To establish the creep damage constitutive equation involving the complicated mechanisms, the relationship of creep strain rate and the dominated mechanism, i.e. diffusion creep, dislocation creep and void induced creep will be deduced firstly. And then, the creep damage constitutive equation can be established in terms of the superposition principle. The contribution of different strain components to creep damage can be clarified based on the damage finite element analysis and the results of rotor anatomy. Finally, the mapping relation between the creep failure strain, lifetime and the reliability will be studied referring to the technique of data mining. As a result, the new criterion related to the safety margin and design life can be established. The findings of this project are believed to remove the large error in the prediction of creep strain at low stress level and produce the criterion for creep strength design of high temperature components of rotating machine.

针对高温结构的低应力长寿命蠕变强度设计问题，本研究主要包括以下内容：通过对服役二十年汽轮机转子的精细解剖和微观分析，研究阐明低应力下的蠕变损伤微观机理；基于高应力连续蠕变及低应力中断蠕变试验，研究建立长时服役结构的蠕变损伤反演方法；研究建立扩散、位错、孔洞等不同主导机制下的蠕变速率预测及多轴应力效应的修正，进一步基于叠加原理，建立复杂机制下的蠕变本构方程；损伤有限元与转子解剖分析相结合，阐明应变分量对损伤的贡献；基于数据挖掘技术建立蠕变破断应变-寿命-可靠度的映射关系，建立与安全度、设计寿命相关联的蠕变设计新判据。本项目可望解决低应力水平下的蠕变预测误差过大问题，形成高温旋转构件的蠕变应变分类准则及设计判据。

本项目针对高温结构的低应力长寿命蠕变强度设计问题，在低应力下高温装备及材料的蠕变实验及损伤微观机理、扩散-位错交互机制下的蠕变损伤本构模型、高温旋转构件的应变分类准则及蠕变失效判据等方面取得了重要进展，形成了高温结构低应力条件下的蠕变设计准则和方法。发表论文22篇（其中SCI检索论文13篇），国家专利授权1件、软件著作权1件，部分成果获得2018年度上海市技术发明奖一等奖。项目负责人先后入选国家万人计划领军人才、国家百千万人才工程，被授予“有突出贡献中青年专家”荣誉称号，受聘担任中国压力容器学会副理事长、《压力容器》杂志副主编、第七届教育部科技委学部委员等。培养博士研究生3人、硕士研究生3人、出站博士后1人，形成具有较好国内外影响的结构完整性技术领域创新团队。