TMF本构和寿命模型:从光棒到涡轮叶片

针对空心涡轮叶片，发展了考虑瞬态变温效应的热机械疲劳（TMF）本构模型和寿命预测方法。第一，以某涡轮叶片用定向凝固合金DZ125为对象，开展了光棒、缺口TMF试验，结合已有的高温疲劳试验数据，获得了相位、温度范围、应力集中等因素对TMF寿命影响规律；第二，利用材料微观组织分析手段，揭示了导致光棒和缺口TMF失效的疲劳裂纹萌生机理；第三，借助于Chaboche本构模型，进行了各向异性、变温、蠕变损伤修正，建立了考虑变温效应的循环-蠕变本构模型，实现了DZ125合金拉伸、等温循环、蠕变、疲劳-蠕变以及TMF应力应变响应的统一建模和预测；第四，发展了疲劳-蠕变-氧化损伤累积的TMF寿命模型，利用简单纯疲劳和蠕变基础数据获得了寿命模型参数，并进一步发展了名义应力法预测了缺口模拟件的TMF寿命；最后，以某涡轮叶片为对象，进行了模拟飞行载荷谱条件下的瞬态变形响应计算和叶片TMF寿命预测。

TMF constitutive and life modeling: From smooth specimen to turbine blade

Thermomechanical fatigue (TMF) constitutive and life models considering transient temperature effect are developed for hollow turbine blades. Firstly, TMF tests of smooth and notched specimens are carried out to test a directionally solidified superalloy DZ125 that is used for the turbine blade. The effect of phase, temperature range and stress concentration factor on TMF lives are obtained. Secondly, The mechanism of fatigue crack initiation that lead to failure of light bar and notch TMF is revealed by means of material microstructure analysis.Thirdly, based on the Chaboche type constitutive model, a cyclic and creep constitutive model is established to investigate the anisotropic, isothermal and creep damage effects. Stress and strain responses under tensile, isothermal cyclic, creep, creep fatigue and TMF are simultaneously modeled and predicted. Fourthly, a TMF life modeling coupling fatigue, creep and oxidation damage is developed and using baseline data including pure fatigue and creep, the parameters of the model are obtained. A nominal stress based method is further developed to predict TMF lives of notched specimens. Finally, the transient deformation and life prediction carried out for a turbine blade subject to a certain loading profile.