Reliability Copula Model for Wind Turbine Gearbox Based on Failure Correlation

On the basis of each gear’s failure correlation, the reliability Copula model of a wind turbine gearbox is established and a 1.5 MW wind turbine gearbox is taken as the research object. Firstly, based on the dynamic reliability model of mechanical parts, each gear’s life distribution function of a wind turbine gearbox is obtained.The life distribution function can be used as the marginal distributions of the system’s joint distribution. Secondly,Copula function is introduced to describe the failure correlation between parts, and the appropriate Copula function is selected according to the shape characters of Copula probability density function. Finally, the wind turbine gearbox system is divided into three parts according to the failure correlation of each gear. The Sklar theorem and the thought of step by step analysis are used to obtain the reliability Copula model for a wind turbine gearbox based on failure correlation.     

风力发电用齿轮箱齿根应力测试系统的开发

针对风电齿轮箱研制中检验修形效果的难点,提出了齿根应力测试技术,可同时测出齿根处,齿向载荷分布系数和载荷不均匀系数.论述了风机齿轮箱应力测试系统的原理及其主要组成部分,给出了典型的应力分布和均载测试结果;重点分析了测试系统中关键的程控放大模块和I2C总线通信.运行实践表明,该应力测试系统能够对齿轮箱的啮合状态进行定量分析,测试结果对齿轮修形及结构设计等有重要的参考价值.     

1.5 MW风力发电机组动态载荷分析

风力发电机动态载荷是影响风机运行和寿命的重要因素,对动态载荷的分析一般采用模型仿真方法.本文针对1.5MW变速变桨风力发电机,基于Samcef for wind turbine（SWT）软件,应用梁单元和超单元进行了高精度建模.模型的控制部分利用曲线查询模拟.在额定风速的湍流风况下,对动态响应曲线、齿轮箱和主轴的两轴承处动态载荷进行了重点分析,揭示了曲线变化成因.通过与Blad-ed软件的仿真结果对比,证明SWT模型具有较高的有效性和参考价值.     

Data-Driven Process Monitoring and Fault Tolerant Control in Wind Energy Conversion System with Hydraulic Pitch System

Wind energy is one of the widely applied renewable energies in the world. Wind turbine as the main wind energy converter at present has very complex technical system containing a huge number of components,actuators and sensors. However, despite of the hardware redundancy, sensor faults have often affected the wind turbine normal operation and thus caused energy generation loss. In this paper, aiming at the wind turbine hydraulic pitch system, data-driven design of process monitoring(PM) and diagnosis has been realized in the wind turbine benchmark. Fault tolerant control(FTC) strategies focused on sensor faults have also been presented here, where with the implementation of soft sensor the sensor fault can be handled and the performance of the system is improved. The performance of this method is demonstrated with the wind turbine benchmark provided by Math Works.     

Numerical simulation to reliability analysis of fault-tolerant repairable system

In the traditional method for the reliability analysis of fault-tolerant system, the system structure is described by means of binary decision diagram (BDD) and Markov process, and then the reliability indexes are calculated. However, as the size of system augments, the size of state space will increase exponentially. Additionally, Markov approach requires that the failure and repair time of the components obey an exponential distribution. In this study, by combining dynamic fault tree (DFT) and numerical simulation based on the minimal sequence cut set (MSCS), a new method to evaluate reliability of fault-tolerant system with repairable components is proposed. The method presented does not depend on Markov model, so that it can effectively solve the problem of the state-space combination explosion. Moreover, it is suitable for systems whose failure and repair time obey an arbitrary distribution. Therefore, our method is more flexible than the traditional method. At last, an example is given to verify the method.     

一种新的焊接构架疲劳分析方法

为了在多工况下进行焊接构架多轴应力的疲劳强度评估,在直接法和投影法的基础上,将二阶张量坐标变换的性质应用于构架的多轴应力疲劳评估,提出了张量法.该方法将多轴应力转换到同一坐标系和同一截面下,根据获得的最大应力和最小应力进行疲劳评估.以某型转向架焊接构架为例,建立了该构架的有限元模型,计算结构在多工况下的应力,并用直接法、投影法和张量法计算了焊接构架的疲劳强度. 通过临界面法和Ncode软件的计算,验证3种方法的合理性.结果表明:考虑多轴应力方向的张量法明显优于另外两种方法,与Ncode计算结果误差最小,为4.42%.      

焊接残余应力对动车组铝合金车体疲劳强度的影响

采用热-弹塑性法和固有应变法计算了动车组铝合金车体对接接头的残余应力, 并进行了对比, 以验证采用固有应变法计算残余应力的合理性; 建立了车体的板壳有限元模型, 参照标准《铁路应用—铁路车辆车体的结构要求》 (EN 12663), 确定车体服役状态的疲劳载荷工况, 采用惯性释放法计算了车体有无残余应力的疲劳强度; 根据最大主应力原则, 将车体多轴应力转化为单轴应力, 得到焊缝和母材关注点的平均应力和应力幅值; 结合铝合金车体材料性能参数绘制了Goodman疲劳曲线, 计算了每个关注点的可靠性安全系数, 分析了残余应力对车体疲劳强度的影响。分析结果表明: 焊接残余应力对母材关注点影响不大, 其可靠性安全系数降幅小于5%;焊缝关注点的平均应力增加量可达25 MPa, 其可靠性安全系数降幅超过50%, 最大为54%, 使得车体容易疲劳失效; 残余应力对焊缝关注点最大主应力的方向有明显的改变。      

高速列车齿轮箱应力响应与疲劳损伤评估

进行了高速列车线路试验, 研究了GPS信号与齿轮箱结构的受力特点, 获取了扭矩载荷和振动载荷作用下齿轮箱的应力时间历程曲线, 分析了在扭矩载荷、振动载荷作用下齿轮箱的应力响应特性, 并编制了应力谱, 利用疲劳损伤影响参数来反映扭矩载荷和振动载荷对齿轮箱疲劳损伤的影响程度。研究结果表明: 在扭矩载荷作用下, 列车牵引与制动的交替变化会使齿轮箱产生较大的应力响应, 最大应力幅值为25.80MPa; 在制动工况下, 齿轮箱应力呈阶梯形变化; 列车低速运行时齿轮箱吊杆座端部的高应力幅值频次大于高速阶段, 结构疲劳损伤影响参数由0.20减小到0.08, 减小了60.0%。在振动载荷作用下, 列车运行速度由350km·h-1减小到200km·h-1时, 齿轮箱吊杆座端部的应力响应强度由2.08MPa减小到0.97MPa, 降低了53.4%;在同一速度等级下, 列车头部齿轮箱的应力幅值低于列车尾部; 列车由牵引状态转变为惰性运行时, 齿轮箱的应力响应强度由3.4MPa减小到1.0MPa, 降低了70.6%;列车由低速运行转为高速运行时, 齿轮箱端部疲劳损伤影响参数由0.009增大到0.260, 增大了27.9倍。      

高速列车齿轮箱疲劳可靠性及故障诊断研究现状

随着高速列车速度不断提高牵引齿轮箱服役环境越发复杂,齿轮箱服役性能也面临更大的考验。基于齿轮箱内、外及耦合激励对其振动响应的影响,国内外学者对高速列车齿轮箱的振动特性和故障诊断做了大量的研究;针对已有的研究成果,主要从齿轮箱强度、可靠性及寿命、箱体故障诊断及监测方面归纳总结,详细阐述了高速列车齿轮箱振动特性分析及故障诊断所采用的方法和研究现状,并且对未来重点研究方向提出建议和展望。     

Simulation on Reliability Enhancement Testing Technology of Ramming System

Ramming system is the key device to guarantee the firing speed of self-propelled gun. Based on traditional reliability enhancement testing method, a new kind of reliability enhancement testing simulation method of ramming system is put forward firstly. In CAD software Pro/E and dynamic simulation software ADAMS, the virtual prototype of ramming system is established. In EASY5 software, the corresponding hydraulic system and control system models are built. The reliability enhancement testing virtual environment of ramming system is developed using the mechanical-electrical-hydraulic co-simulation technology. Based on the load spectra provided by virtual prototype, and the stress distribution provided by finite element analysis and material's S-N curve(S is fatigue strength, N is fatigue life), a model of fatigue enhancement coefficient is established through the failure mechanism analysis. The simulation processes and simulation results show the feasibility of reliability enhancement testing based on virtual prototype, and provide sufficient theory reference for structure improvement and optimization of ramming system.     

采用加速度输入等效风力发电机组塔筒实测响应方法研究

通过对单自由体系的分析,得到风荷载激励和从基底输入的加速度之间的关系。通过对风力发电塔的模态分析,得到简化为广义单自由体系的广义质量和广义刚度,求得风力发电塔塔顶位移的时程曲线,采用Savitzky-Golay平滑算法和差分法求得顶点的加速度和速度时程,以此求得合成后的等效加速度。对直接合成后的等效加速度进行傅里叶变换,采用低通滤波器剔除高频分量,进行傅里叶逆变化后得到最终等效加速度。有限元分析结果表明,在此等效加速度下的结构响应和已知响应吻合一致,从而为风力发电塔的减振试验在振动台上完成成为可能。     

基于小滚轮高频激励的高速列车齿轮箱箱体振动试验

为探究高速列车齿轮箱箱体振动特性和疲劳损伤, 应用小滚轮高频激励台架试验, 将滚轮表面加工成径跳量幅值为0.05 mm的13阶多边形, 可等效成20阶车轮多边形, 研究了某型齿轮箱箱体在不同垂向载荷与速度工况下的振动特性; 通过雨流计数法及Miner线性损伤法则, 分析了齿轮箱箱体单位时间应力累计损伤。研究结果表明: 受齿轮箱箱体共振影响, 不同垂向载荷与速度工况下, 高速列车运行速度为200 km·h-1时, 齿轮箱箱体各测点的垂、横向加速度均方根值均为最小; 当垂向载荷为23 t时, 大部分测点的垂、横向加速度均方根值均为最大; 齿轮箱箱体存在573 Hz的局部固有频率被激发共振, 其原因是试验速度为100 km·h-1时试验台发生共振, 以及试验速度为300 km·h-1时, 受到20阶多边形车轮转频约580 Hz的主频激扰; 车轮初始速度从0加速到200 km·h-1及从300 km·h-1减速至0的速度等级之间时, 齿轮箱箱体各测点的单位时间应力累计损伤波动较大, 其余速度等级段各测点的单位时间应力累计损伤波动很小; 单位时间应力损伤最大值出现在大齿轮箱齿面观察孔, 为3.72×10-10, 损伤最小值位于小齿轮箱轴承正上方, 仅为8.29×10-18。可见, 箱体共振、试验台减速运行、速度等级对齿轮箱箱体振动加速度影响较大; 非共振、试验台不减速运行、相同速度等级下, 垂向载荷对单位时间应力累计损伤影响甚微。      

Design of Wind Turbine Blade for Solar Chimney Power Plant

Aiming at the global efficiency of solar chimney power plant (SCPP), we design a wind turbine generation device to elevate its electricity generating efficiency. Based on wind power utilization theory, a new method is proposed to design a type of wind turbine blade for SCPP. The lift and resistance coefficients on different Reynolds numbers of NACA4418 airfoil, which is suitable for experimental solar electricity generation system, are determined by Profili-V2.0 airfoil design software, a program written in Matlab to calculate chord length of the airfoil. The optimization is conducted by class-shape-transformation (CST) parameterization method and Xfoil software. An airfoil design program is designed on the basis of blade element theory and attack angle with the highest lift coefficient to iteratively determine the inflow angle and setting angle. Prandtl’s tip-loss factor is applied to correct the setting angle, after the airfoil data are input into AutoCAD to build an airfoil model which is then imported into Solidworks to draw blades. A new way is put forward to design wind turbine blades in SCPP.     

湛江海湾大桥索梁锚固结构足尺模型试验

为了深入研究锚拉板式索梁锚固结构的传力机理和应力分布规律，评估其安全性和可靠性，以湛江海湾大桥为工程背景，对锚拉板式索梁锚固结构进行了足尺模型试验，并与非线性有限元仿真结果进行了比较．研究表明：锚拉板与锚拉筒连接焊缝处应力水平较高，远离焊缝应力分布趋于均匀；结构整体受力合理，具有足够的安全储备，但局部存在应力集中，设计时应予以注意．     

钢桥桥面铺装层间剪应力影响因素及简化计算

为了减小钢桥桥面铺装层间剪应力,建立桥面系三维有限元计算模型,分析了不同荷位、钢板厚度、U肋开口宽度、铺装厚度、铺装模量、层间接触条件以及轴载大小对铺装层间纵横向剪应力的影响,推导了实用的应力简化计算公式。研究发现桥面板不均匀变形使得铺装层间剪应力远大于同条件下的路面结构;影响显著的因素依次为轴载大小、钢板厚度、U肋开口宽度以及铺装参数;层间完全光滑有利于抗剪,但降低了桥面系整体刚度;控制重载,加强桥面系刚度与选择柔性层间粘结材料是减小层间剪应力的有效措施。     

基于谱载荷的高速列车转向架构架的疲劳强度

为了有效地预测高速列车转向架构架的疲劳强度或寿命，提出了一种基于试验谱载荷的疲劳强度预测方法．这种方法是用雨流计数法对UIC515-4和UIC615-4规定的构架疲劳强度试验载荷和载荷循环次数进行分级，用有限元法确定构架在每级载荷作用下的应力分布，将多轴应力转化为单轴应力，根据palmgren-Miner线性累积损伤准则计算构架的等效应力，利用S-N疲劳曲线预测构架的疲劳强度或寿命．算例表明，采用该预测方法计算的高速列车转向架构架的疲劳强度与现有文献的结果一致．     

基于谱载荷的高速列车转向架的疲劳强度

为了有效地预测高速列车转向架构架的疲劳强度或寿命,提出了一种基于试验谱载荷的疲劳强度预测方法.这种方法是用雨流计数法对UIC515-4和UIC615-4规定的构架疲劳强度试验载荷和载荷循环次数进行分级,用有限元法确定构架在每级载荷作用下的应力分布,将多轴应力转化为单轴应力,根据Palmgren-Miner线性累积损伤准则计算构架的等效应力,利用S-N疲劳曲线预测构架的疲劳强度或寿命.算例表明,采用该预测方法计算的高速列车转向架构架的疲劳强度与现有文献的结果一致.     

铁路车辆部件抗疲劳评估的进展与挑战

从铁路车辆的安全运用及服役评估出发，论述了转向架部件(如构架、车轴等)的抗疲劳评估及应用进展，重点分析了合金钢EA4T车轴和碳素钢S38C车轴的设计理念差别，阐明了车轴运用评估中存在的难定量和过保守的理论局限性; 首创了“名义应力”+“损伤容限”有机融合的阶梯疲劳评估方法，给出了样本信息聚集改进原理、基于单轴拉伸的裂纹扩展模型、应力-缺陷-寿命的三参数评估图和表面残余应力重建等四大关键技术。分析结果表明:基于传统名义应力法的抗疲劳设计给出的寿命预测偏于保守，导致车辆部件维修不足或者过度维修; 基于单轴拉伸性能的新型裂纹扩展模型的精度优于NASGRO方程; Kitagawa-Takahashi图把基于名义应力的疲劳极限和基于断裂力学的缺陷特征有机关联起来，比Goodman图更直观、定量和全面; 基于表面单位压力法，获得了与实测结果一致的S38C车轴的压缩残余应力分布，表明压缩残余应力的引入提高了新干线车轴的抗微动磨损能力和抗疲劳裂纹扩展能力; 广域环境服役、超高周疲劳、增材修复再制造、断裂求解技术及动力学和强度学结合等问题成为未来研究的重要课题。      

双馈风力发电系统MPPT控制技术的研究

介绍了变速恒频风力发电的基本原理,并采用定子磁链定向的矢量控制方法得到了双馈发电机的矢量控制系统模型.本文利用Matlab软件建立了该系统的仿真模型,仿真结果验证了这种矢量控制策略既能保证定子输出频率的恒定,又能达到有功功率和无功功率的独立解耦控制,同时还能较好地跟踪风力机的最大功率输出.     

基于模糊理论的车辆变刚度弹簧组可靠性优化设计

为提高变刚度弹簧组的设计质量,在传统优化设计方法的基础上,应用模糊设计理论和可靠性设计理论,建立了当弹簧应力和强度分别为随机变量和模糊变量时,综合考虑静强度、疲劳强度、稳定性、质量等因素的变刚度弹簧组的模糊可靠性优化设计模型.以货车某新型变刚度弹簧组为研究对象,利用建立的模型对其进行了优化设计分析,计算结果显示,空重车静挠度分别比原设计方案提高了5.4和3.2 mm,同时还使其总质量降低了约15.8%,表明所建立的模糊可靠性优化设计模型能满足设计要求.