重型燃气轮机叶片离心载荷下应力特性的研究

针对重型燃气轮机叶片疲劳寿命研究的需要,通过设计和搭建的全尺寸叶片疲劳试验装置,模拟离心载荷工况下的低周疲劳试验,开展离心载荷下叶片应力分布和疲劳寿命预测的研究。该全尺寸叶片疲劳试验装置能够模拟低周疲劳中的等效离心载荷工况,为叶片试验提供必要的条件和手段。同时,对叶片进行网格划分和有限元仿真计算后,得到叶片Von mises应力分布结果,发现叶身应力最大处位于中部偏下边缘薄壁侧。然后将有限元仿真及应力试验相结合,提出叶片疲劳试验的离心载荷等效方法。在此基础上完成叶片的动应力试验,获得应力时间历程数据,并且给出离心载荷应力谱。结果表明,叶身中部边缘的应力水平最高,动应力谱幅值与频数概率的分布服从6阶麦克劳林拟合函数,用等效离心载荷疲劳寿命进行叶片寿命预测的结果是偏安全的,该结论可作为优化设计和试验研究的参考依据。     

Aero-engine blade fatigue analysis based on nonlinear continuum damage model using neural networks

Fatigue life and reliability of aero-engine blade are always of important significance to flight safety.The establishment of damage model is one of the key factors in blade fatigue research.Conventiona...     

Fretting fatigue in dovetail blade roots: Experiment and analysis

A biaxial fatigue experiment is described which is capable of simulating the loading experienced by a dovetail blade root in an aircraft gas turbine. A comprehensive stress analysis of the experimental configuration has been undertaken and a semi-analytical approach has been developed to provide accurate estimates of surface tractions and subsurface stress fields. The forces (normal and shear) and moment for the semi-analytical model are calculated from the global finite element analysis of the dovetail in which coarse elements were used. The bulk stress and the bending stress in the disk and blade were evaluated by calculating the membrane and bending stresses across the thickness of the disk and blade. Short crack arrest methods have been applied to the results of the stress analysis to predict the fatigue performance of the blade specimens. The results show a good agreement with the experimental observations.     

定向凝固合金涡轮叶片的低周疲劳寿命研究

对某发动机DZ4定向凝固高温合金涡轮叶片进行了有限元应力分析，应力分析中考虑了发动机实际工作过程中的离心载荷和不均匀温度引起的热负荷。利用应力分析结果和该材料的疲劳特性计算了1次飞行起落过程造成的发动机低循环疲劳损伤和900h飞行的总损伤，根据损伤等效原理，确定了试验规定条件下与900h飞行等效的试验谱以及试验寿命折算为飞行小时寿命的计算公式。     

透平叶片固有频率和振型的测试方法分析

以透平叶片为研究对象,采用LMS系统对叶片的静频和振型进行了测试。单只叶片的试验测试结果与数值计算结果吻合良好,说明所提供的叶片分析模型和静动态分析方法具有良好的工程精度,验证了有限元计算的准确性。结果显示,装配后叶片固有频率的分散度加大,因此在以后的装配过程中,需要对装配后各叶片固定力进行控制;如果控制难以实现,则必须对装配后的叶片的固有频率进行测试,使固有频率及其分散达到设计要求,为此类叶片的结构优化或性能优化以及叶片的再设计提供理论依据。     

基于固有频率变化的两焊点接头的疲劳损伤参量

使用有限元软件ABAQUS分析两焊点拉剪试样在疲劳裂纹扩展过程中的动态响应,研究固有频率随裂纹面积的变化.将裂纹截面积作为损伤面积,确定损伤与固有频率变化率的关系.利用损伤力学中损伤随寿命的演化规律,对疲劳损伤达到一定程度的试样进行疲劳寿命预测.结果表明,此损伤参量能较好地描述双焊点结构的疲劳破坏过程.     

Study of creep-fatigue behavior in a 1000 MW rotor using a phenomenological lifetime model

In this study, the phenomenological lifetime model was applied to part of an ultra-supercritical steam turbine rotor model to predict its lifetime as a post processing of the finite element method. To validate the accuracy and adaptation of the post processing program, stress-strain hysteresis loops of a cylinderal model under service-like load cycle conditions in cycle N = 1 and 300 were constructed, and the comparison of the results with experimental data on the same cylinderal specimen showed them to be satisfactory. The temperature and von Mises stress distributions of the rotor during a startup-running-shutdown-natural cool process were numerically studied using ABAQUS and the damage caused by the interaction of creep and fatigue was subsequently computed and discussed. It was found that the maximum damage appeared at the inlet notch zone, with the blade groove areas and the front notch areas also suffering a large damage amplitude.     

低周疲劳失效的涡轮盘可靠性灵敏度设计

将有限元方法、低周疲劳模型、径向基函数神经网络技术与可靠性理论相结合,给出了涡轮盘低周疲劳可靠性灵敏度设计方法。应用径向基函数神经网络拟合得到随机设计变量与失效寿命之间的函数关系式,根据随机摄动法与可靠性灵敏度技术进行灵敏度设计。径向基函数神经网络技术的引入克服了工程实际无法给出极限状态函数显式的问题,而灵敏度技术使各变量对可靠度的影响得以定量表达,具有很好的指导意义。     

Numerical Estimation of Fretting Fatigue Lifetime Using Damage and Fracture Mechanics

Fretting fatigue is a complex tribological phenomenon that can cause premature failure of connected components that have small relative oscillatory movement. The fraction of fretting fatigue lifetime spent in crack initiation and in crack propagation depends on many factors, e.g., contact stresses, amount of slip, frequency, environmental conditions, etc., and varies from one application to another. Therefore, both crack initiation and propagation phases are important in analysing fretting fatigue. In this investigation, a numerical approach is used to predict these two portions and estimate fretting fatigue failure lifetime under a conformal contact configuration. For this purpose, an uncoupled damage evolution law based on principles of continuum damage mechanics is developed for modelling crack initiation. The extended finite element method approach is used for calculating crack propagation lifetimes. The estimated results are validated with previously reported experimental data and compared with other available methods in the literature.     

NTK300型风电机组主轴疲劳断裂失效分析

随着风电机组服役时间的逐年增长,早期投产的风电机组陆续出现主轴的疲劳断裂事故。本文结合国内某风电场的NTK300风电机组主轴断裂问题,对断裂主轴进行宏观和微观断口分析,结果表明:风电机组主轴在额定工况载荷作用下,虽工作应力水平较低,应力集中不明显,但长期服役后仍可能发生疲劳断裂。同时,通过有限元分析发现,额定工况载荷作用下的主轴在断裂位置处应力分布相对集中。通过主轴高周疲劳断面SEM图片的对比发现,主轴在断裂位置的轴向截面应力分布梯度与某一时刻疲劳裂纹萌生和扩张的方向基本一致。     

燃气涡轮转子盘-片系统三维非线性循环应力-应变分析

燃气涡轮转子盘—片系统的几何形状和结构形式比较复杂，在高温、高转速的恶劣条件下工作，准确的应力分析是进行强度计算和疲劳寿命预测的重要前提。使用ANSYS有限元结构分析软件，建立了燃气涡轮盘—片接触系统三维循环对称有限元模型，考虑了叶片材料的各向异性、涡轮盘与叶片榫头之间的接触非线性、材料的弹塑性变形和温度不均匀引起的热应力等情况，数值模拟涡轮盘—叶片组件的受力状态及边界条件，进行三维非线性循环应力—应变分析。     

Probabilistic fatigue-creep life reliability assessment of aircraft turbine disk

Life consumption is one of the serious concerns for turbine disk performance and maintenance cost. The low cycle fatigue of turbine disk coming from the creep and their interaction has a direct influence on life and reliability of an aero engine. So, in this paper, the finite element analysis fatigue creep on Nickel base super alloy GH4133 turbine disk at 650 °C is computed based on the material properties, load and performance parameter of the low cycle fatigue as a random factor. The LCF Manson coffin model for cycles to failure (N_f ) and Larson Miller (N_c) are calculated. Damage fraction summation is used to calculate the low cycle fatigue creep life and fitted by two parameter Weibull distribution. Therefore, Monte Carlo simulation is used in random sampling from two parameter Weibull distribution to estimate the reliability assessment of turbine disk.     

涡轮增压器叶轮模态特性的探究

针对增压器常发生的由于叶片振动产生的叶片损害现象,利用三维CAD建模软件对废气涡轮增压器叶轮进行建模,并 采用有限元分析软件对其进行振型模态分析,找出发生共振的频率,为叶轮的优化设计提供了理论依据。     

叶片的固有频率测试与模态分析

采用了叶片固有频率测试系统对某汽轮机叶片进行测试实验。以模态分析理论和有限元方法为基础,使用Hypermesh和Abaqus对叶片进行联合仿真,分析某汽轮机叶片的动力学性能。比较和分析叶片前三阶固有频率计算值与试验值,得到较满意的结果。     

Explicit finite element modeling of subsurface initiated spalling in rolling contacts

An explicit finite element model was developed to investigate crack initiation and spall formation in machine elements subject to rolling contact fatigue. The modeling approach utilizes continuum damage mechanics to capture the initiation and propagation of fatigue damage that leads to the formation of a surface spall. The material microstructure is modeled via a randomly generated Voronoi tessellation. The material parameters for the model were obtained independently from torsional fatigue life data for 52100 bearing steel. The life scatter (Weibull slope) and the spall geometry obtained from the model correlate well with experimental results available in the open literature.     

基于缺陷分布形式的粉末冶金涡轮盘可靠度计算模型

为研究微缺陷对粉末冶金涡轮盘可靠性的影响,在有限元分析结果的基础上,基于国内粉末盘中缺陷分布的概率特 点,建立针对低循环疲劳裂纹萌生和裂纹扩展失效模式的可靠度计算模型。该模型可计算不同缺陷分布形式、不同循环载荷条件下的轮盘可靠度。对某型粉末盘失效概率的分析表明：表面质量是导致粉末盘失效的重要因素,这同大量试验研究结果相一致,对粉末盘的设计和使用具有工程指导意义。     

涡轮盘低循环疲劳两种可靠性分析方法的对比

使用基于应力和基于应变的疲劳可靠性分析方法,对比分析了涡轮盘低循环疲劳寿命及可靠性。P-S-N曲线由三参数函数式来描述,并由异方差回归拟合,涡轮盘危险点的应力应变可由有限元分析和响应面法得到,对比了应力寿命、应力强度、应变寿命和应变强度四种疲劳可靠性模型的寿命及可靠度,结果表明基于应力的分析方法,也可用于涡轮盘低循环疲劳可靠性分析。     

叶片振动响应的长度分形故障特征提取与诊断

为有效地从风力发电机组的振动响应中获得反映叶片响应的动态特征,将其作为叶片运行状态分析的特征量,依此达到对风力机叶片故障的检测与诊断识别.应用有限元分析方法,建立了300 W风力发电机组的动力学模型,通过计算与试验模态分析,分别获得整机组的固有频率和振型,并比较验证了试验模型的合理性.用锤击法测得叶片正常状态和偏心故障下的振动加速度响应信号,应用非线性动力系统的长度分形维数理论,计算其长度分形维数,并将其作为叶片偏心故障诊断识别的特征量.研究结果表明,该方法能有效识别风力机叶片正常状态和偏心故障状态,及其偏心位置和偏心量大小.     

高频谐振载荷作用下Ⅰ型疲劳裂纹尖端力学参数变化规律

为研究高频谐振式疲劳裂纹扩展试验中带有Ⅰ型预制裂纹的紧凑拉伸(CT)试件裂纹尖端力学参数的变化规律,利用动态有限元方法,采用ANSYS和MATLAB软件编写程序,计算了CT试件在高频恒幅正弦交变载荷作用下,在一个应力循环及裂纹扩展到不同长度时裂纹尖端区域的位移、应变场及裂纹尖端的应力强度因子,并分析了其变化规律。在计算裂纹尖端应力强度因子时,首先采用静态有限元方法和理论公式验证了有限元建模和计算的正确性,然后采用动态有限元方法研究了裂纹扩展过程中裂纹尖端应力强度因子的变化规律。最后进行了高频谐振式疲劳裂纹扩展试验,采用动态高精度应变仪测量了裂纹扩展到不同阶段时裂纹尖端点的应变,并对有限元计算结果进行了验证。研究结果表明：在稳态裂纹扩展阶段,高频谐振载荷作用下Ⅰ型疲劳裂纹尖端位移、应变及应力强度因子均为与载荷同一形式的交变量;随着裂纹的扩展,Ⅰ型疲劳裂纹尖端的位移、应变及应力强度因子幅不断增大;静态应力强度因子有限元计算值和理论值的误差为2.51%,裂纹尖端点应变有限元计算结果和试验结果最大误差为2.93% 。     

基于悬臂梁位移模型的直升机桨叶损伤检测

从悬臂梁位移模型出发,建立桨叶结构损伤检测的位移残差范数准则,通过桨叶实测位移残差的范数分析结构是否存在局部裂纹损伤,研究一种基于悬臂梁位移模型的桨叶结构损伤检测方法.桨叶结构损伤用裂纹大小或刚度下降等参数指标表示.采用能量方法分析裂纹对梁元弯曲刚度的影响,建立裂纹梁有限元模型,根据桨叶有限元模型构造一种节点力残差向量,利用该力残差向量可确定损伤位置和损伤程度.最后,通过实例验证方法的可行性和有效性.