高瞬态高温升下薄壁结构破坏的寿命规律及其预测方法研究

Thermal shock is a typical failure phenomenon of high temperature thin wall structures in service under the condition of high transient, rapid ascending and high gradient temperature field. It will inevitably occur with the cyclic change of thermodynamic parameters of heat engines, resulting in premature failures and cracks in structures which is much different from traditional thermal fatigue and high temperature fatigue. Presently, there is no strength design methods and theories such as calculation method, life model and criterion in the existing structural design system. However, the evaluation results will commonly be seriously dangerous based on the traditional theory and model. In the present project, life behavior and life prediction method for thin wall structure subjected to high transient and rapid ascending temperature field will be extensively investigated. Using the thermal shocking system consisting of Glebble3800 test machine and MEMS thin film sensor, the effect of geometrical structure and load parameters on deformation, failure and life will investigated in macro and micro level. The calculation method of rapid thermal conduction process will be studied. Based on the modified viscoplastic constitutive model considering variable temperature effect, the distribution and cyclic response of temperature, stress and strain field in the near surface of the specimens subjected to thermal shock will be obtained and revealed. Using the observation of the failure mechanism and analysis of the cyclic thermal mechanical response, thermal shock damage model and life prediction method considering high transient and high gradient thermal effects will be proposed. The theory, method and model in this project will provide a theoretical and scientific methods for structural strength life estimation of combustion chamber, guide vane, rotor blade and other high temperature alloy structures.

热冲击是在高瞬态、高温升、高梯度温度场作用下高温薄壁结构在服役中的典型破坏现象，伴随着热机热力循环参数变化而不可避免地发生，导致结构提前发生不同于传统热疲劳、高温疲劳的皲裂破坏。目前，现有结构设计体系尚无热冲击计算方法、寿命模型及准则，而基于传统理论和模型又使得强度评价严重偏于危险。本项目深入研究高瞬态、高温升下薄壁结构破坏的寿命规律及其预测方法。利用Glebble3800试验机和MEMS薄膜传感器组成的热冲击试验系统，研究几何结构和载荷参数对热冲击变形、破坏和寿命的影响机制。开展急速热传导过程的计算方法研究，并基于修正了变温效应的粘塑性本构模型，揭示热冲击下结构近表层温度、应力、应变场分布和循环响应规律。利用机理和热力响应分析结果，提出考虑高瞬态、高梯度热力效应的热冲击损伤模型和寿命预测方法，为燃烧室、导向器叶片、转子叶片等高温合金结构寿命评价提供理论和科学方法。

项目以用于现代高性能航空发动机的薄壁高温合金结构为研究对象，探索了在复杂快速升降温度热循环-机械载荷下的疲劳失效问题，获得了精密铸造薄壁结构的寿命规律，揭示了含典型结构的薄壁结构的破坏规律，得到了气膜孔在反相位和同相位载荷下不同的高温筏化机制、反相位下楔形裂纹萌生机理、同相位下滑移型裂纹萌生机理，建立了一套考虑了损伤演化、应力状态、应力梯度的寿命预测方法，并得到了工程应用。

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