一种基于单谐次角振动信号的内燃机工作状态监测新方法

分析了内燃机轴承低阶扭振振型特性;提出了单谐次准等差振幅模型。当内燃机轴系满足此条件时,提出一种利用曲轴低谐次扭振信号幅值监测内燃机工作状态的新方法。并以某机车柴油发电机组轴系为对象进行了应用研究,验证了本方法的实用性和诊断准确性。新方法不需要其他结构参数,简便易行,而且准确度高,适用广泛,有较强的工程实用价值。     

机车轴承新的动态检测技术

介绍了机奉轴承新的动态检测系统的构成及主要参数。该系统使用灰色系统多参数诊断法对轴承的质量进行动态检测，很好地反映了轴承的质量状况，为铁路应用部门提供了可靠的动态检测设备。     

打靶法在非线性转子—轴承系统中的应用

以转子动力学和非线性动力学理论为基础，针对非线性弹性转子－轴承系统的具体特点，用打靶法对采用短轴承模型的弹性转子－轴承系统的周期解进行了求解，并用数值积分和庞加莱映射方法对其动力学特性随某一参数变化时稳定性的改变进行了分析，计算结果表明，系统具有发生倍周期分叉及概周期运行的可能。用数值方法得到系统在某些参数域中的分叉图，直观显示了系统在某些参数域中的动态状态。数值分析结果为该类转子一轴承系统的设计和运行状态控制提供了理论参考。     

支持向量机和BP神经网络在水轮发电机轴承故障诊断中的应用

支持向量机(SVM)与BP神经网络相比各有优缺点,通过对支持向量机和BP神经网络在水轮发电机滚动轴承故障诊断中的仿真实验,来对比两者在轴承故障诊断上的泛化能力。首先通过应用经验模态分解(EMD)的方法将轴承振动信号进行分解,得到本征模函数(IMF),再将IMF的平均能量值作为故障特征向量。将这些特征向量作为支持向量机和BP神经网络的学习样本。经过仿真研究结果表明,在小样本集的前提下,支持向量机在轴承故障诊断中的精确度不但受样本数量变动的影响较小,准确度也高于BP神经网络,具有较强的泛化能力。对水轮发电机滚动轴承故障诊断模型的应优先考虑选择SVM。     

监测大型汽轮发电机组四可倾瓦轴承负荷的试验研究

讨论了支承力法（即用测力传感器直接监测大型汽轮发电机组四可倾瓦轴承负荷的方法）的原理和误差，介绍了轴承试验台结构及其测试系统，并在试验驯进行了四可倾瓦轴承负荷测试试验研究和误差分析，试验结果表明，支承力法有较高的测试精度，它的综合误差小于５％，可满足工程测试要求。     

用于带轴涡轮转子超速试验的电磁轴承控制器设计

本文提出了在转子超速试验中利用电磁轴承控制振动的设想。通过对电磁轴承及带轴涡轮转子系统模型的建立和研究，获得系统状态方程和传递函数，并介绍了一种利用根轨迹法，求取PID控制器参数的设计方法。仿真控制结果表明，该装置可以减弱转子振动，实现在超速试验下平稳运行。     

叶片固有频率散度的计算

根据文献[1]提出的参数小变化对本征值影响的思路及弯矩法导出在参数小变化时固有频率散度的简便计算公式。并以某型压气机叶片为例,给出小偏差的理论计算值与实测数据的对比结果,其方法可用于叶片固有频率散度的工程计算和频谱分析。     

基于改进自适应多元变分模态分解的轴承故障诊断方法研究

为解决多元变分模态分解(MVMD)经验参数设置对分解结果的影响,提出一种新的自适应多元变分模态分解(AMVMD)方法并将其应用于轴承的故障诊断方面.首先,将最小平均包络熵(MAEE)作为适应度函数,采用灰狼算法(GWO)寻求MVMD参数的最优解,并按照最优参数对原始信号进行分解.然后,计算各本征模态分量(IMF分量)的...     

基于EEMD峭度-相关系数准则的多特征量风电机组轴承故障诊断

针对风力发电机组轴承故障振动信号具有高噪声、非线性、非平稳的特性,提出了一种集成经验模态分解与峭度-相关系数准则和多特征量提取的风电机组轴承故障程度的诊断方法。利用集成经验模态将振动信号分解成若干个本征模态分量,采用峭度和相关系数准则选取一组包含信息量最丰富的分量,对该组分量从时域指标、自回归模型参数矩阵的奇异值和能量熵3个角度的变化中提取和构造多特征量矩阵,输入支持向量机建立故障程度不同的多分类预测模型,优化核参数和惩罚参数取得轴承故障程度最佳预测精度。通过实验室数据验证了该方法是一种可行的风电机组轴承故障诊断方法,可实现对风电机组轴承故障早期处于的轻度、中度和重度等3种相对故障程度的准确分类和识别。     

具有裂纹的曲轴-轴承系统动力学与摩擦学耦合分析

以实测示功图为计算依据,以4缸柴油机的曲轴-轴承系统为研究对象,应用动力学仿真软件ADAMS耦合分析了具有裂纹的曲轴-轴承系统动力学行为和摩擦学特性,提出了"等效直径法"建立具有不同深度裂纹的弹性曲轴有限元模型.由于裂纹的扩展是曲轴动力学响应的慢变参数,从启裂到曲轴断裂采用线性插值法,分别建立具有不同深度裂纹的曲轴-轴承系统动力学和摩擦学耦合分析ADAMS模型并求解.结果表明,裂纹对其附近的曲轴轴承的动力学和摩擦学性能影响较大,随着裂纹深度的增加,裂纹附近的主轴承反力、最大油膜压力峰值和最小油膜厚度均减小,但曲轴轴颈中心径向振动响应振幅增加.     

滑动轴承非线性动态油膜压力分布特性的研究

针对有限长径向滑动轴承非线性动态油膜压力的分析与计算,定量阐明了非稳定润滑油膜的动态压力特性,进一步研究了轴承中转子自转速度、涡动速度及转子偏心速度等参数对非线性油膜压力分布变化规律的影响。图8参6。     

考虑曲轴倾斜和摩擦接触的主轴承润滑分析

采用有限元、多体动力学和弹性流体动力润滑理论来联合计算16V240ZJB型柴油机主轴承的润滑情况,将曲轴当作弹性体,以考虑曲轴的弹性变形对主轴承润滑状态的影响.曲轴工作过程中受外力的作用,会产生弹性弯曲变形,使主轴颈在主轴承内倾斜,甚至与主轴瓦的边缘发生摩擦接触,本文采用了Greenwood-Tripp粗糙接触模型计算接触摩擦力.根据AVL相关标准评价了润滑计算结果,九个主轴承均润滑良好,其中第8主轴承粗糙接触压力最大、油膜厚度最低,润滑的情况相对最恶劣.     

官地水电站重力坝深层抗滑稳定分析

官地水电站坝址区地质条件复杂,缓倾角错动带和裂隙较发育,分布比较普遍,因此坝基深层抗滑稳定问题受到高度关注。利用ANSYS有限元分析软件,选取#13坝段作为典型坝段,结合该坝段工程实际和概化的滑移通道,建立三维有限元模型,采用强度储备法分析坝基的深层抗滑稳定性、坝体及坝基的位移和应力变化规律。结果表明,三维非线性有限元分析在以塑性区贯通为失稳判据的情况下,最危险的滑移通道1的深层抗滑稳定安全系数大于3.0,可见#13坝段深层抗滑稳定满足规范要求。     

融合维纳过程和粒子滤波的风力发电机轴承剩余寿命预测

提出维纳过程与粒子滤波相结合的滚动轴承剩余寿命预测方法,将维纳过程引入粒子滤波状态空间模型,充分利用其随机增量性质,增强模型的非线性表达能力,提高预测的准确性。提出弱跟踪粒子滤波策略调整维纳过程,解决概率密度分布方差过大的问题。该方法在试验台轴承和风力发电机轴承测试数据中均得到验证,可准确预测轴承剩余寿命。     

General static load‐carrying capacity of four‐contact‐point slewing bearings for wind turbine generator actuation systems

Four‐contact‐point slewing bearings are widely used in wind turbine generators (WTGs) to adjust the orientation of the blades and the nacelle to fully exploit wind resources. These bearings must withstand static and fatigue loads; however, at the first stages of the design process, the bearings are commonly selected by considering only static loads. This paper presents a further step of a previous theoretical work published by the authors in the field of the static load‐carrying capacity of four‐contact‐point slewing bearings under axial, radial and tilting‐moment loads. In that work, a generalization of the works by Sjoväll and Rumbarger was presented, providing an acceptance surface of the bearing in the load space. The contact angle of the balls was assumed to be load independent. The present work improves that development by considering the influence of the variability of the contact angle with the applied load, and as a result, the acceptance surface has been redefined. By comparing the results with those of the finite element model published by the authors, it is proven that the new model presented in this work is more realistic than the previous one. Thus, it is believed that this methodology can be easily applied for the initial selection of blade and yaw bearings in WTGs. Copyright © 2012 John Wiley & Sons, Ltd.     

Meshless element free Galerkin method for unsteady nonlinear heat transfer problems

In this paper, meshless element free Galerkin (EFG) method has been extended to obtain the numerical solution of nonlinear, unsteady heat transfer problems with temperature dependent material properties. The thermal conductivity, specific heat and density of the material are assumed to vary linearly with the temperature. Quasi-linearization scheme has been used to obtain the nonlinear solution whereas backward difference method is used for the time integration. The essential boundary conditions have been enforced by Lagrange multiplier technique. The meshless formulation has been presented for a nonlinear 3-D heat transfer problem. In 1-D, the results obtained by EFG method are compared with those obtained by finite element and analytical methods whereas in 2-D and 3-D, the results are compared with those obtained by finite element method.     

On the buckling problem of a pressure vessel torispherical head due to internal pressure

The torispherical head of a circular cylindrical pressure vessel subjected to internal pressure can buckle if the head is very thin and the pressure is high enough. Previously, Aylward and Galletly analyzed this problem by the finite element method, considering the nonlinear prebuckling deformation. In this paper a numerical method is presented for buckling problems of the general axisymmetric shell, including consideration of its nonlinear behaviors in the prebuckling state. By using this method, the buckling problem of the torispherical head treated in Galletly's study is solved, and the results obtained by the present method are compared with Galletly's. It is found that the results coincide closely enough for practical purposes.     

某三缸汽油机气缸盖三维有限元分析

以某三缸汽油机气缸盖为研究对象,通过建立了的气缸盖、机体、气缸垫等零件三维有限元组合模型,使用有限元分析软件ANSYS,在考虑各组件接触关系的基础上,对该气缸盖在预紧工况及爆发工况时(加载温度场)分别进行了三维有限元计算分析。计算结果显示:在预紧工况,该气缸盖变形主要由螺栓拧紧产生;在爆发工况,最高燃烧压力对该汽油机气缸盖应力、变形影响不大;在热负荷作用下,该气缸盖某些区域相对预紧工况应力变化较大,易发生低频疲劳失效。     

The applications of 2D elasto-plastic stochastic finite element method in the field of fracture mechanics

In this paper the stochastic finite element method (SFEM) is applied to the field of fracture mechanics and cracked structures are analysed by using an elasto-plastic methodology. The main random variables considered are Young's modulus, Poisson's ratio and the crack size. The formulae of the mean and variance value of the J-integral for elasto-plastic deformation are discussed and an effective method for the probabilistic safety assessment of cracked structures is given. Some elasto-plastic problems are solved by this method, and numerical examples demonstrate that this method is appropriate for engineering problems and that the related computer program developed in this paper has sufficient precision.     

ABAQUS的二次开发在胶凝堆石坝工程中的应用

鉴于分析胶凝堆石坝结构缺少有效手段,利用ABAQUS的二次开发平台,开发了胶凝堆石料非线性弹性本构模型的UMAT用户子程序,提出了实现胶凝堆石坝的施工模拟及新填筑层位移修正的处理方法,并在两种工况下进行有限元模拟计算。结果表明,该方法合理可靠、符合实际工程规律。