Inconel625/BNi-2钎焊接头蠕变裂纹扩展行为及寿命预测研究

The long time and reliable operation are the critical requirements for the design of the aero-engine recuperator. The aim of this proposal is to investigate the creep crack growth behaviors and life prediction of the Inconel625/BNi-2 brazed joint in the aero-engine recuperator. The contents of this proposal are structured as follows: Firstly, the effect of the constraint effect on the creep crack growth behaviors of the brazed joint will be investigated. The mapping relationship between the failure mechanism and the creep crack growth behavior will be proposed. Secondly, the calculation model that considering the diffusion zone, phase transition and thermal elastoplastic will be developed to understand the effect of the diffusion zone and phase transition on the residual stress. Based on this method, the stress distribution at the region of the crack tip can be accurately predicted. Finally, according to the scientific description of the relationship between the micro-defect evolution and the damage state in the brazed joint, a multi-axial creep damage model with clear physical meanings will be proposed, and then to develop a life prediction method combined with the finite element software that considering the as-brazed residual stress and the creep constraint effect. Based on this life prediction method, the life of the brazed joint from the material-component to equipment can be predicted. Through the achievements of this proposal, the effect of the creep constraint and the as-brazed residual stress on the creep crack growth behavior and life of the brazed joint will be clear. And also, it can provide an important insight on the long life design and manufacturing of the aero-engine recuperator.

面向航空发动机回热器长周期可靠性运行的要求，针对工作条件下回热器中Inconel625/BNi-2钎焊接头的蠕变裂纹扩展行为及寿命预测展开研究。主要研究内容为：(1) 研究拘束条件下钎焊接头的蠕变裂纹扩展行为，揭示拘束效应对钎焊接头蠕变裂纹扩展行为的影响规律，建立失效机理与蠕变裂纹扩展行为之间的映射关系；(2) 建立考虑扩散区-相变-热弹塑性的残余应力计算模型，澄清扩散区及相变对残余应力的影响规律，实现钎焊接头裂纹尖端应力的有效预测；(3) 基于钎焊接头中微观缺陷演化与损伤状态定量关联的科学描述，建立物理意义明确的多轴蠕变损伤本构模型，进而利用有限元发展考虑残余应力-拘束效应的材料-组件-装备一体化寿命预测方法，实现钎焊接头寿命的准确预测。通过上述研究，掌握拘束效应及残余应力对钎焊接头蠕变裂纹扩展行为和寿命的影响规律，为航空发动机回热器的长周期可靠性设计提供科学支持。

面向航空发动机回热器、固体氧化物燃料电池、核电等领域换热装备长周期可靠性运行的要求，针对工作条件下回热器中Inconel625/BNi-2钎焊接头的蠕变裂纹扩展行为及寿命预测展开了研究。主要研究内容为：(1) 研究了拘束条件下钎焊接头的蠕变裂纹扩展行为，揭示拘束效应对钎焊接头蠕变裂纹扩展行为的影响规律，建立失效机理与蠕变裂纹扩展行为之间的映射关系；(2) 基于纳米压痕测试技术，建立考虑扩散区-硼化物-热弹塑性的残余应力计算模型，澄清扩散区及硼化物对残余应力的影响规律，实现钎了焊接头裂纹尖端应力的有效预测；(3) 基于钎焊接头中微观缺陷演化与损伤状态定量关联的科学描述，建立了物理意义明确的多轴蠕变损伤本构模型，进而利用有限元发展考虑残余应力-拘束效应从材料到装备一体化寿命预测方法，实现了钎焊接头寿命的准确预测。通过上述研究，掌握拘束效应及残余应力对钎焊接头蠕变裂纹扩展行为和寿命的影响规律。本课题所提出的蠕变损伤本构模型及寿命预测方法进一步应用于航空发动机回热器、固体氧化物燃料电池以及核电等领域高温结构的蠕变裂纹扩展速率及寿命预测，为高温结构的长周期可靠性设计提供了科学支持。