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.

燃气轮机的组件暴露于启动和关闭周期引起的高热和机械载荷。因此，使用的镍基合金的热机械疲劳（TMF）是评估组件强度的主要标准。由于热瞬变和结构力学，在服务过程中，组件的临界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在本地变化（相对，相位，相位，相移）。但是，只有在理解裂纹生长的生命周期限制机制时，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不是可量化的影响，因为材料特性取决于温度，因此材料行为时间依赖于时间，因此相位角度起着重要作用。一方面，在这个项目中，通过实验研究了裂纹生长，裂纹闭合和损伤相互作用。另一方面，使用有限元方法的数值研究用于识别裂纹闭合，裂纹生长和材料特性之间的相关性。基于实验和数值结果，开发了基于机制的模型，该模型可以与相位角结合温度依赖性机械性能的影响以及时间依赖性对多晶铸成镍基碱合金的TMF裂纹生长的影响。