Influence of the cyclic thermal and mechanical loading history on crack closure, fatigue crack growth and damage interaction of cast nickel-base alloys

循环热和机械载荷历史对铸造镍基合金裂纹闭合、疲劳裂纹扩展和损伤相互作用的影响

• 批准号: 392066748
• 负责人: Dr. Christoph Schweizer
• 金额: --
• 依托单位: Fraunhofer-Institut für Werkstoffmechanik (IWM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/392066748?language=en
• 关键词: Influence; cyclic; thermal; mechanical; loading

Components of gas turbines are exposed to high thermal and mechanical loads resulting from start-up and shut-down cycles. Thus, thermomechanical fatigue (TMF) of the used nickel-base alloys is a major criterion for the assessment of the strength of the components. Due to thermal transients and structural mechanics, varying loading histories are present in critical areas of the components during service, where the phase angle between thermal and mechanical load varies locally (ouf-of-phase, in-phase, phase-shift). Meaningful fatigue life predictions can, however, only be obtained if the lifetime limiting mechanisms of crack growth are understood. In this regard, crack closure and the interaction of different damage mechanisms have a significant, but today not quantifiable influence, since the material properties are temperature-dependent, the material behaves time-dependent and, hence, the phase angle plays an important role. In this project, on the one hand, crack growth, crack closure and the damage interaction are investigated experimentally. On the other hand, numerical investigations with the finite-element method are used to identify correlations between crack closure, crack growth and material properties. On the basis of the experimental and numerical results, a mechanism-based model is developed which can reproduce the influence of the temperature-dependent mechanical properties in combination with the phase angle and the time-dependency on the TMF crack growth of the polycrystalline cast nickel-base alloy IN100.

燃气轮机的部件承受着启动和停机循环产生的高热负荷和机械负荷。因此，所用镍基合金的热机械疲劳（TMF）是评估部件强度的主要标准。由于热瞬变和结构力学的原因，在使用期间部件的关键区域中存在不同的负载历史，其中热负载和机械负载之间的相位角局部变化（异相、同相、相移）。然而，只有了解裂纹扩展的寿命限制机制，才能获得有意义的疲劳寿命预测。在这方面，裂纹闭合和不同损伤机制的相互作用具有显着但目前无法量化的影响，因为材料特性与温度相关，材料的行为与时间相关，因此相位角起着重要作用。在该项目中，一方面，通过实验研究裂纹扩展、裂纹闭合和损伤相互作用。另一方面，使用有限元方法进行数值研究来确定裂纹闭合、裂纹扩展和材料性能之间的相关性。在实验和数值结果的基础上，开发了一种基于机理的模型，该模型可以重现温度依赖性机械性能以及相角和时间依赖性对多晶铸镍 TMF 裂纹扩展的影响-基础合金IN100。