涡轮盘榫槽的损伤力学研究

NONLINEAR DAMAGE ACCUMULATION MODEL FOR TURBINE DISC SLOTS

本文运用损伤力学方法对涡轮盘试件榫槽在蠕变和疲劳交互作用下的裂纹起始寿命与裂纹扩展寿命进行了分析研究。榫槽的非线性损伤累积模型是由修正的Ｃｈａｂｏｃｈｅ′ｓ低循环疲劳损伤模型和改进的Ｋａｃｈａｎｏｖ′ｓ蠕变损伤模型综合形成的。在此基础上建立了疲劳和蠕变交互作用下裂纹扩展计算模型。从理论分析计算与试验结果的一致性，说明所建模型的正确性。采用损伤有限元素法，以有限元网格尺寸模拟损伤裂纹长度。从试件榫槽的裂纹扩展计算分析中，提出裂纹起始方向和裂纹扩展方向判断准则，并通过计算检验了此准则的正确性。文中所建立的基本理论，计算方法及结果分析在工程实际中具有一定使用价值。

The crack initialization life and crack propagation life of turbine disc slots at high temperature under the fatigue/creep interaction are studied according to damage mechanics.The modified Chaboche's damage model of low cycle fatigue and the improved Kachanov's damage model of the creep crack propagation have been combined to establish a nonlinear damage accumulation model.A model of crack propagation under fatigue/creep interaction has been developed,based on the above mentioned model.The good agreement between the calculated results and experimental data demonstrates that the model is quite effective.Damage FEM has been developed according to damage mechanics and FEM.The method uses finite element mesh dimension to simulate damaged crack length.The criteria for the crack initialization and the crack propagation orientation are established and testified by the calculation of the fir-tree slots of a turbine disc under the two kinds of loading conditions.The effects of mesh's minimum dimension,the stress boundary condition and the displacement boundary condition of the calculation model on the crack initial life of the structure are analyzed.It is also discussed,how the calculation model scale and the peak value of trapezoid loading spectrum affect the crack propagation life of a two-dimensional structure.