MW级风力发电机组主轴疲劳分析

基于风力机主轴有限元分析模型,对MW级风力机主轴疲劳损伤进行了研究.利用MSC.Marc/Mentat软件分析了风力发电机主轴的疲劳应力;运用雨流循环计数法计算了主轴的疲劳载荷谱.最后,提出了一种将雨流循环计数法与Palmgren-Miner线性累积损伤理论相结合的主轴疲劳损伤计算的方法,并根据GL规范修正了主轴材料的S-N曲线.分析结果表明,本文提出的方法是可靠实用的,为风力发电机组主轴的疲劳寿命分析提供了一个更为准确的分析思路,具有一定的工程实用意义.     

QT350-22U铸造风力机轮毂疲劳寿命分析

以球墨铸铁QT350-22U铸造件风力机轮毂为研究对象,采用修正的雨流计数法处理载荷谱,并结合Palmgren-Miner线性累积损伤理论和有限元法,分析了铸造件轮毂在不同质量等级下的疲劳损伤。结果表明,不同质量等级下轮毂的疲劳损伤相差较大,但以球墨铸铁QT350-22U为材料的轮毂在两种质量等级下均能满足风力机20年的寿命要求;基于有限元法的疲劳分析还可以找到轮毂累积疲劳损失最大点,为轮毂的优化设计提供参考。     

MW级风力发电机塔顶法兰疲劳分析

对MW级风力发电机塔筒顶部法兰的疲劳损伤进行研究,运用有限元分析软件MSC.Marc/Mentat建立塔顶法兰连接系统有限元模型,对塔顶法兰疲劳应力进行了分析,利用Bladed软件实现了对法兰疲劳工况的载荷仿真,并结合雨流计数法获取法兰疲劳载荷谱,最后运用疲劳分析软件MSC.Fatigue和Palmgren-Miner线性累积损伤理论实现了对塔筒顶部法兰的疲劳分析.结果表明,该分析方法有效实用,为大型风力发电机法兰的疲劳分析提供了一条新思路,具有一定的工程实用价值.     

基于非线性连续损伤的机床轴结构疲劳研究

运用MINER线性累积损伤理论对机床轴结构进行疲劳研究时,由于不能连续描述损伤与载荷之间的关系,在高周疲劳寿命预测过程中其计算结果不能令人满意。为此,基于CHABOCHE提出的单轴非线性连续累积损伤理论,通过对45钢进行疲劳试验获得了轴结构材料的S-N曲线,在对机床载荷谱简化处理的基础上,建立了适于机床轴结构寿命预测的多轴非线性连续损伤累积模型。实例计算证明,该模型能准确描述机床轴结构损伤累积过程,计算结果更符合工程实际。     

基于协同仿真的风力发电机叶片的疲劳研究

对反求得到的叶片实体,应用动力学仿真软件ADAMS和有限元分析软件Ansys进行协同仿真确定叶片疲劳载荷谱以及利用线性损伤累积理论分析玻璃钢叶片的疲劳问题,得到叶片疲劳寿命等数据,为产品的再设计、再创新提供参考。     

风力发电机组内轮毂体疲劳寿命计算与研究

结合有限元和疲劳损伤理论,以轮毂为对象进行疲劳寿命的计算与研究。研究了单位载荷下有限元计算结果、疲劳载荷和材料S-N曲线。对轮毂体的热点使用绝对值最大主应力法,结合拟合得到的铸件材料S-N曲线计算得到疲劳损伤云图,对轮毂的疲劳寿命进行快速评估。该方法的研究为风力发电机组上其他铸件疲劳寿命提供了参考。     

QT350-22L铸造风力机主机架疲劳特性分析

以球墨铸铁QT350-22L风力机主机架铸件为研究对象,采用雨流计数法对载荷谱进行处理;基于Miner准则,应用有限元方法,分析和评估了主机架铸件各种工况下的疲劳状况与使用寿命。结果表明,以球墨铸铁QT350-22L为原料铸造的风力机主机架的疲劳损伤能满足20年的工作要求;基于疲劳理论的有限元分析可以找到结构件累计疲劳损伤最大点,利于优化设计,减少制造和维护成本。     

车体振动模态对疲劳强度的影响分析

铁路运输车辆不断朝着高速以及轻量化方向发展,车体承受着复杂的交变载荷,极大地增加了车体结构疲劳断裂的风险。为探究车体结构振动对车辆结构安全性的影响,利用ANSYS Workbench进行车体模态仿真计算。结合服役环境下动车组车体运行模态测试数据,提取出车体1阶菱形(8~9 Hz)、1阶垂弯(12~13 Hz)、1阶横弯(15~16 Hz)及1阶扭转(17~18 Hz)模态频率,对车体有限元模型进行对比修正。利用雨流计数法对部分实测载荷谱数据谱进行处理,得到载荷谱雨流计数矩阵。在模态分析的基础上进行谐响应分析,得到上述不同模态频段范围内的频率响应函数,结合nCode疲劳仿真软件对车体疲劳强度进行仿真计算,得到不同频段范围内车体的疲劳损伤;采用Miner线性累积疲劳损伤理论对仿真计算结果进行疲劳损伤评估,结果表明:车体1阶菱形模态(8~9 Hz)附近频段对车体造成的损伤最大,其损伤位置在车钩与枕梁交接处附近。     

风力发电机组内铸件的强度分析计算

风力发电机组内铸件的强度分析计算,主要包括极限强度和疲劳寿命计算。铸件的极限强度计算采用有限元法进行,以轮毂为例介绍铸件的极限强度计算。铸件疲劳寿命的计算分为两个部分,即单位载荷下铸件的应力分析计算和根据铸件所承受载荷的疲劳载荷谱和单位载荷下应力值进行疲劳损伤值的雨流统计计算。     

基于不同应力法的焊接构架纵向角接头疲劳累积损伤评估

在焊接构架结构应力计算整体有限元模型基础上,通过考虑接头角焊缝和1 mm焊趾虚拟缺口半径,对转臂定位座板与箱形侧梁下盖板的组焊纵向角接头进行逐步细化,构建热点应力和有效缺口应力计算局部模型.在动态疲劳试验载荷等效的9级载荷谱作用下,分别基于名义、热点及有效缺口三种不同应力参量,结合ⅡW建议的疲劳设计S-N曲线进行累积损伤计算.结果表明,有效缺口应力的累积损伤远高于名义和热点应力,极有可能引起评估结果过于保守.为充分发挥有效缺口应力法的优势,需要以更加符合结构实际的缺口几何数据和强度数据作为支撑.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。