防爆液压提升机制动系统的可靠性仿真

以矿用防爆液压提升机制动系统为对象建立其故障树模型,运用蒙特卡罗法对制动系统关键部位可靠性进行仿真分析。实际使用情况及仿真结果表明,在防爆提升机液压制动系统中采用基于故障树的可靠性仿真分析,能够提高可靠性分析精度,发现制动系统的薄弱环节,为制动系统维修提供科学依据。     

基于蒙特卡罗法的液压试验平台可靠性分析

工程机械液压试验平台是一个复杂的机电系统,具有故障多样、成因复杂、隐蔽性强的特点,因此不宜采用传统的数值解析方法或者直接移植其他类型系统的可靠性分析方法来分析系统的可靠性。根据实际液压试验测试平台系统的结构组成,构建系统的故障树;采用蒙特卡罗随机模拟方法对故障树的失效模型进行仿真评估,得出系统的可靠性指标和系统可靠性的最薄弱点,提出提高可靠性的方法,使系统的可靠度指标提高了31%。仿真结果也为系统的进一步优化设计和维修工作提供参考意见。结果表明:基本故障树的蒙特卡罗法适用于大型复杂液压系统或机电液系统的可靠性评估,为大型复杂系统的可靠性分析提供参考。     

超声汽化蒸汽驱动的尿道阀可靠性分析

尿道阀是控制尿道启闭的元件,一旦发生失效将导致严重后果。为了提高尿道阀的可靠性,采用故障树分析法分析了尿道阀可靠性,基于尿道阀故障树分析和蒙特卡罗法提出了尿道阀可靠性仿真算法,仿真计算了尿道阀可靠性指标,实验验证了仿真结果的正确性。结果表明:驱动囊的腐蚀和老化是尿道阀的薄弱环节,尿道阀平均寿命达到50 000次的可靠度为0.85,算法简捷有效。研究结果可为尿道阀的结构优化设计和可靠性分析提供依据。     

基于ANNES的矿井提升机故障诊断系统模型

针对矿井提升机的具体状况提出了一种基于神经网络和专家系统相结合的故障诊断系统模型,重点介绍了该模型的结构和实现方法.     

基于蒙特卡罗方法的机床主轴可靠性预测

针对机床主轴可靠性的预测,提出了一种基于蒙特卡罗模拟仿真的机床主轴可靠度求解方法。阐述蒙特卡罗理论并建立主轴可靠性预测模型,采集机床主轴输出端电机的电压和电流信号,计算出电机的输出功率,并画出功率的时域图,结合数理统计和概率论相关理论得到样本均值的置信区间和可信度。利用蒙特卡罗仿真产生符合抽样样本的总体分布的随机数,通过置信区间和功能函数计算出机床主轴可靠性的无偏估计,判断数控机床运行状态下主轴的可靠性。实验数据结果分析表明,该方法可以有效地判断机床主轴可靠性预测,验证了方法的可行性。     

基于动态故障树的铸造起重机起升机构可靠性分析

针对铸造起重机起升机构可靠性问题，提出一种基于动态故障树的起升机构可靠性分析方法。首先介绍动态故障树理论与动态故障门，对铸造起重机进行动态故障树建模，通过线性搜寻法对动态故障树进行分层，得到其动态子树和静态子树，采用马尔可夫链和二元决策图相结合的方法对子树模块进行求解，最后综合各个子树故障率得到起升机构故障率。     

基于故障树自动建造的线控转向系统的可靠性分析

电动汽车采用线控转向(Steering By Wire,SBW)系统会导致汽车转向可靠性的降低。采用故障树自动建造的方法,对SBW系统结构与部件的正常运行和失效模式进行规范化描述并建立标准件库,采用拖拽的方式搭建标准的故障树。故障树自动建造完成后,基于故障树对SBW系统进行可靠性定量分析,结果表明:故障树法可以迅速找出系统的薄弱环节,在系统优化设计基础上,提高了SBW系统的可靠性。     

再制造盾构机刀盘液压驱动系统的可靠性分析

再制造作为绿色制造的重要组成环节,是解决资源短缺和环境污染问题的有效途径之一。盾构机刀盘与其它部件相比,有着对可靠性要求特别高的特点,因此开展盾构再制造刀盘的可靠性研究十分必要。考虑到盾构机的掘进工况,建立刀盘液压驱动系统的可靠性框图与数学模型,通过仿真得到的可靠度曲线进行了可靠性分析。建立马达模块的故障树模型并对马达故障树进行分析,找到了导致马达失效的关键因素,为提高盾构液压驱动系统的可靠性提供了理论措施。     

基于故障树蒙特卡洛的双动力刀架可靠性分析

文章采用故障树蒙特卡洛仿真针对双动力刀架进行可靠性分析。首先根据刀架故障模式建立双动力刀架系统故障树,得到刀架系统的最小割集;然后利用MATLAB进行蒙特卡洛仿真,结合函数关系对双动力刀架可靠性进行估计,并与传统分析方法所得数据比较,验证仿真正确性;最后确定刀架薄弱环节并预测可靠性。解决了传统可靠性分析试验周期长、数据样本大且难于处理、运算缓慢的问题。     

基于单片机控制的矿井提升机运行系统设计

本文介绍了基于单片机的变频控制系统对矿井提升机工作过程进行控制的系统设计，包括硬件电路、部分软件程序和程序流程图。通过矿井提升机交流调速系统的分析，采用直接转矩控制技术对提升机制动力矩进行自动调节。     

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。