铁路客车风缸吊装结构强度仿真分析

文中基于我国某25G型检修客车车下副风缸的特殊吊装结构,采用HYPERMESH软件建立了风缸有限元模型,并采用Ansys对处理后的模型进行了强度计算分析,计算结果表明,在各超常工况下,风缸单元的最大应力均出现于吊座与缸体的衔接焊缝处,但其值并未超过材料的屈服极限,满足相关的轨道车辆标准要求,符合车辆的安全运营需求,也为...     

高强度27MnCr5钢变速器传动轴冷锻工艺研究

运用DEFORM 3D软件对高强度27MnCr5钢变速器传动轴冷锻成形进行了有限元仿真,获得了始锻和终锻的应力和应变。对始锻、终锻下的冷锻传动轴试样进行了拉伸和疲劳试验,获得了传动轴抗拉强度和疲劳应力值,并与仿真结果进行了对比分析。结果表明:随着冷锻成形的进行,传动轴等效应力、等效应变、极限抗拉强度、张紧应力幅值、张紧平均应力、弯曲应力幅值、弯曲平均应力都逐渐增加;有限元仿真应力值与试验应力值的最大相对误差为3.41%,说明仿真分析是比较准确和可靠的。     

基于FEM的超高压液压顶升装置力学特性分析

液压顶升装置各部件在超高压下的力学特性是影响其性能的主要因素，也是超高压技术的难题。采用有限元方法研究超高压液压顶升装置各部件的材料、内径、厚度等不同时，其液压系统刚度、模态、固有频率、位移、应力的变化规律。有限元计算结果与压力试验结果较为接近，验证了有限元模型及边界条件的有效性。结果表明：液压弹簧刚度随液压缸内径增大而增加、随振幅增加而下降，其影响随内径增加而减少；系统前3阶固有频率随地面强度增大而增加；Bonded工况极限应力值最小，Frictionless工况极限应力最大，极限应力随地面强度增加而减少；C20地面时，最大位移随摩擦因数增加而增加，最大应力随地面强度增加而增加；C30地面时，最大位移随摩擦因数增大先增后减，其位移、应力临界摩擦值分别为0.43、0.59；结构钢地面时，极限位移显著减少。液压缸同长度不同位置极限位移差值随地面强度而增加；液压缸底端应力值随地面强度增加而增加；液压缸外表面一孔侧位移均小于二孔侧，且极限位移更靠近顶端，并交替出现极值。分析了超高压液压装置的应力-应变过程，为其结构设计、密封设计及使用提供了参考。     

井架结构的疲劳寿命预测及承载试验研究

为了计算在役JJ113/32型井架结构的承载力与剩余疲劳寿命,在现场对该井架进行了静、动态载荷测试。利用I-DEAS软件建立了有限元仿真模型,在测试钩载下二者的结果吻合较好,验证了模型的准确性。经综合分析,井架承载的薄弱杆件位于1号立柱的下部,承受的最大应力小于材料的极限应力值,满足原最大设计钩载的要求。对井架杆件的疲劳寿命的计算结果表明,该井架有较大的寿命安全系数,能够在服役期继续使用。     

极限挖掘载荷下挖掘机铲斗轻量化设计

为研究如何在满足强度要求的前提下降低铲斗的质量,提出一种基于连续挖掘轨迹和极限挖掘力的铲斗轻量化设计方法。基于连续轨迹理论选定当挖掘机器人动臂处于主挖区内,由铲斗、斗杆液压缸交替挖掘的4段轨迹作为研究前提,计算并分析了连续轨迹上极限挖掘力的数值变化规律;使用APDL语言建立铲斗参数化模型,以极限挖掘力为外载荷研究铲斗结构强度的变化规律;以铲斗质量和应力为优化目标建立铲斗结构优化模型,使用遗传算法对铲斗进行优化。结果表明：铲斗液压缸挖掘时铲斗的应力、变形明显大于斗杆挖掘;优化后铲斗的质量减少了5.27%、最大应力减少了6.23%,验证了优化方法的可行性。     

U75V钢轨材料在疲劳载荷下应力强度因子的探讨

以U75V钢轨材料紧凑拉伸(compact tension, CT)试样为研究对象,应用理论公式、弹性位移外推法/弹性应力外推法、弹塑性位移外推法/弹塑性应力外推法,求解在疲劳载荷作用时不同裂纹长度下的应力强度因子及幅值。结果显示,弹性位移外推法/弹性应力外推法计算的应力强度因子及幅值和理论解基本一致;裂纹长度小于12 mm时各种计算方法的应力强度因子以及幅值几乎一样,但随裂纹长度的增大,弹塑性位移外推法/弹塑性应力外推法计算的应力强度因子Kmax以及幅值呈增大趋势。在疲劳裂纹扩展阶段中后期,考虑小范围屈服时,使用弹塑性位移外推法/弹塑性应力外推法计算的应力强度因子及幅值用于疲劳裂纹扩展速率和疲劳剩余寿命的计算会更安全。     

非均匀磁场作用下磁流变弹性体悬臂夹层梁振动响应实验分析

流体压力脉动致振是影响大型服务器液冷系统管道可靠性的重要因素之一。基于ANSYS workbench中的模块连接功能,提出一种液冷管道振动应力分析方法。首先在Static Structural模块中分析管道在稳定流体压力作用下的应力情况,然后在Harmonic Response模块中分析管道在流体压力脉动作用下的响应情况。测量实际管道的振动加速度,并结合有限元仿真计算结果进行对比分析,确定液冷管道中流体的压力脉动幅值。分析结果表明：弯管处是管道上应力最大的部位,应优先进行振动可靠性分析。该成果可为大型服务器液冷系统管道可靠性研究提供了一种可行的振动分析方法。     

铁液脱硫搅拌器的热-结构耦合分析与优化

针对某炼铁厂脱硫搅拌器服役寿命短和设计周期长等问题,从降低耐火材料最大应力值和提高寿命的角度出发,采用正交试验法进行结构优化。基于有限元软件对正交试验设计的方案进行热-结构耦合应力场分析,得到各组方案下搅拌器耐火材料的最大应力值,通过极差分析获得了最优的参数组合及各个参数不同水平对最大应力值的影响程度,顺序从大到小为:迎铁面偏移角、叶片过渡圆弧半径、背铁面偏移角、叶片直径、叶片端面倾角。结果表明,优化后的搅拌器耐火材料最大应力值由优化前的56.22 MPa减小为35.66 MPa。正交试验法能为提高搅拌器寿命和优化设计提供理论指导。     

四辊光整机牌坊的设计与研究

针对热镀锌板的光整工艺要求,对四辊光整机牌坊进行结构和尺寸设计,并应用Ansys软件对光整机牌坊进行应力、应变和位移的有限元分析,通过分析得出:最大应力值出现在上横梁圆柱体与立柱上部的过渡圆角处,最大应力值小于材料的屈服极限,满足强度要求。单个机架在6 000k N轧制力作用下,机架Y方向的总变形为0.98 mm,机架X方向的总变形为立柱在M2作用下的弯曲变形,造成立柱中部内弯1.213 mm,满足牌坊刚性要求。     

45碳钢低周疲劳与应力循环棘轮失效的实验研究

对调质处理的45碳素结构钢进行了应变循环低周疲劳实验以及应力控制棘轮失效实验．对于前者进行了带平均应变和不带平均应变的实验，以研究平均应变对低周疲劳特性的影响；对于后者研究了平均应力和应力幅值对棘轮失效的影响．应变循环实验表明：平均应变对循环饱和行为以及低周疲劳循环失效圈数并没有明显的影响，但对材料的循环初期循环塑性行为有影响．棘轮失效实验结果表明：当应力幅值较大而平均应力较小时，材料的棘轮失效主要归于较大塑性应变幅值引起的低周疲劳破坏；当平均应力较大而应力幅值相对较小时，材料的棘轮失效主要归于较大的棘轮应变引起的材料韧性破坏，其失效准则可以用最大单调极限应变来表征．     

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。