涡轮盘材料低周叠加高周复合疲劳断裂特性研究
A STUDY ON FATIGUE CRACK PROPAGATIONSUPERIMPOSING HIGH CYCLES ON LOW CYCLESFOR TURBINE MATERIALS
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摘要: 航空发动机的载荷谱,包含起飞和着陆间的各种巡航状态,可简化为梯形波表示。在涡轮盘和压气机盘的关键区域,如连接叶片的盘缘,离心力和热应力的变化,以起动——停车作为一个工作循环,称为主循环,是低周疲劳的主要损伤源。在载荷保持期间(巡航状态),局部高应力区可能产生蠕变或应力松弛,实际上还会有低幅值高周振动(称为次循环)应力叠加在主循环上,简化载荷谱如图1所示。这种状态除航空发动机外,在多数动力机械如原子能装置、内燃机等都可能发生。在评定承受低周叠加高周复合作用的构件及材料疲劳断裂性能时,应该考虑高周损伤的重要作用。本文介绍近年来所作初步研究的部分结果。Abstract: The crack propagation under combined fatigue superimposing high frequency vibration with lower amplitude on low cycles with higher amplitude and its fractographic features for GH36 alloy are studied. Experimental results show that the high cycle damage will be a main factor when the amplitude ratio of high cycle to low cycle is larger than 0.98. Then,the surface deformation just ahead of the crack tip is decreased,each wide striation consisting of a number of parallel sub-striations produced by vibration stress and the cyclic hardening are increased. In this case,assessing of the FCG rate is basically independent of the LCF damage.
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