Numerical modeling of fatigue crack growth in single crystal nickel based superalloys
Numerical modeling of fatigue crack growth in single crystal nickel based superalloys
复制标题
单晶镍基高温合金疲劳裂纹扩展的数值模拟
DOI：
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发表时间：
2010
期刊：
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通讯作者：
O. Aslan
中科院分区：
文献类型：
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作者：
O. Aslan
在高温下工作的单晶元件受到严重的热机械载荷条件的影响。这些组件的几何形状和行为现在非常复杂。一个主要问题是建立模型来预测在强应力和温度梯度存在下的裂纹萌生和裂纹扩展。必须考虑单晶镍基高温合金材料的强各向异性弹粘塑性行为。相应的模型应能够考虑复杂应力场中各向异性裂纹扩展和裂纹分岔。此外，该模型不仅要能够预测裂纹扩展速率，而且要能够预测非直线裂纹路径。各向异性损伤力学是发展单晶裂纹扩展模型的一个非常合适的理论框架。在之前的项目中已经开发了一个耦合晶体塑性和循环损伤的模型，该模型显示了该方法的兴趣，但也显示了其当前的局限性，特别是结果的强网格依赖性。最近在广义连续体力学框架内的非局部模型的发展可以帮助克服这些困难。单晶镍基高温合金的起裂和裂纹扩展具有较好的实验基础。涡轮叶片热力学的有限元模拟提供了有关应力和塑性应变分布的详细信息，特别是在几何奇点附近，如冷却孔和狭缝。首先，在晶体塑性理论的基础上，提出了基于有限元计算历史的非耦合损伤力学模型，该理论提供了应力和塑性应变之间的牢固联系。随后，提出了基于广义连续体的增量损伤模型，并通过求解网格依赖关系对微裂纹的起裂和扩展进行模型预测。
Single crystal components operating at elevated temperatures are subjected to severe thermomechanical loading conditions. The geometry and behaviour of these components are now very complex. A major issue is to develop models to predict crack initiation and crack growth in the presence of strong stress and temperature gradients. The strongly anisotropic elastoviscoplastic behaviour of the material which is a single crystal nickel base superalloy, must be taken into account. The corresponding model should be able to account for anisotropic crack growth and crack bifurcation in complex stress elds. Moreoever the model must be capable of predicting not only the crack growth rate but also the non-straight crack paths. Anisotropic damage mechanics is a well-suited theoretical framework for the development of crack growth models in single crystals. A model coupling crystal plasticity and cyclic damage has been developed in a previous project, that shows the interest of the approach, but also its current limits, in particular the strong mesh dependence of the results. Recent development of nonlocal models within the framework of the mechanics of generalized continua could help overcoming these difficulties. A large experimental basis exists concerning initiation and crack growth in single crystal nickel base superalloys. Finite element simulations of the thermomechanics of turbine blades provide detailed information about stress and plastic strain distribution, in particular near geometrical singularities like cooling holes and slits. First of all, on the basis of crystal plasticity theory which provides a solid link between stress and plastic strains, an uncoupled damage mechanics model based on the history of FE calculations will be presented. Afterwards, an incremental damage model based on generalized continua will be proposed and model predictions for the initiation and growth of microcracks by solving the mesh dependency, will be discussed.