高温低周/高周-超高周复合疲劳损伤多尺度研究

High reliability and long service life are power equipment development goals and urgent requirements in aviation, aerospace, navigation, energy industrial applications. The nickel alloy (Nimonic80A or GH80A) is chosen to do the test. Based on the load character of turbine rotor components, Nickel-based alloy is chosen to study the multi-scale damage in long fatigue life and high temperature (400℃，600℃，800℃) after different aged treatment. After well understanding of the alloy fatigue behaviors in low, high and very high fatigue in high temperature by experimental methods, through the new development long life and high temperature combined fatigue test method, the long life combined fatigue damage is investigated by tests with low/high fatigue load superposition the very high cycle fatigue load. The micro structure of the alloy at different combined fatigue damage stages is analyzed by using Electron Backscattered Diffraction (EBSD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) method in order to obtain the micro structure changing and fatigue damage characters. The effect of precipitation is studied in the micro scale to understand the strengthen mechanisms and fracture mechanism in the combined fatigue tests. The micro deformation, thermal dissipation and damage of the fatigue are estimated by the micro mechanics and crystal plasticity to develop a method to evaluate the fatigue life in high temperature fatigue. The proposed multi-scale method and the combined fatigue test results can be used to improve the aging treatment process and provide a new LCF/HCF combined VHCF life model.

高可靠长寿命是航空、航天、能源等工业领域动力装备的发展目标和迫切要求。本课题选取时效处理后的镍基高温合金(Nimonic80A或GH80A)，根据航空发动机转子部件载荷特点，采用多尺度方法研究高温下（400℃，600℃，800℃）低周/高周复合超高周疲劳载荷作用下材料的损伤和寿命问题。通过自主研发的高温长寿命复合疲劳试验系统，在单独分析材料在高温低周、高周和超高周疲劳和损伤特点的基础上，开展高温合金的低周/高周叠加超高周疲劳载荷的复合疲劳研究。采用电子背散射衍射、扫描电镜、透射电镜等设备研究复合疲劳高温合金的微观结构变化、损伤特性，分析析出相对高温复合疲劳强化效应机理和疲劳裂纹萌生机理。采用微观力学和晶体塑性力学估计弹塑性变形、固有耗散和微观损伤，建立复合疲劳寿命模型。本课题的研究结果可用于优化高温材料的时效处理工艺，提供新的长寿命复合疲劳损伤和寿命估计方法。

高可靠长寿命是航空、航天和能源等工业领域动力装备的发展目标和迫切要求。本课题首先采用低频疲劳机和压电陶瓷超声振动疲劳机耦合加载，研制高温电磁感应加热系统和高温夹具，开发出新的高温下低周/高周-超高周复合疲劳试验系统。选择镍基高温合金材料(GH80A，GH4169)和耐热不锈钢，试验材料的室温和高温低周、高周和超高周疲劳行为，获得复合疲劳试验寿命。分析高温合金材料在不同温度和疲劳载荷加载后的微观结构变化特征及疲劳裂纹萌生机理。基于晶体塑性有限元（CPFEM）的分析了超高周疲劳载荷作用下材料微观应力分布特征，采用固有耗散分析和疲劳损伤理论预测裂纹萌生点位置，建立材料在低周-高周或超高周疲劳载荷下的寿命估计模型。项目开发的高温低周-高周/超高周疲劳试验系统可为航空航天推进系统的高温部件材料的疲劳行为测试提供试验方法和寿命设计数据。