考虑结合面因素的加工中心关键部件动态特性研究

结合面是影响高端数控机床整机刚度的重要因素,工作台竖直移动式卧式加工中心中,结合面对系统动态特性的影响尤其显著。根据机床固定结合面及滑动结合面的特点,将动力学模型中的结合面表达为一系列刚度-阻尼单元;利用影响系数法建立工作台竖直移动式卧式加工中心Y轴进给系统动力学模型,并分析床身-立柱固定结合面、立柱-工作台滑动结合面刚度阻尼特性对系统动力学响应的影响规律,绘制工作台、拖板、立柱位移响应的FFT图。研究结果对于优化机床装配工艺具有指导意义。     

立式加工中心动力学分析及结构优化研究

研究了通过机床的动态特性分析进行结构优化的方法,提出了一种新的优化设计方案。针对对机床整机模态特性和谐响应特性,在有限元分析软件中对机床动态性能进行了仿真。分析结果表明,主轴箱和立柱为机床敏感部位,因此使用有限元分析软件对主轴箱进行拓扑优化,并且为立柱增加筋板。根据优化结果重新设计机床主轴箱和立柱结构,将优化后与未优化的机床的分析结果进行对比,结果表明机床的动态性能得到明显改善,主轴箱各阶固有频率提高10%左右,机床整机固有频率提高4%左右,x方向上的响应峰值减少约2%。     

激光全息术在组合机床滑座体选型设计中的应用

目前国内动力滑台部件中的滑座体由于刚度较差很难满足组合机床高精度加工的需要。因此,有必要对滑座体进行多种结构方案的分析比较,以寻求高刚度滑座体的合理结构。文章着重介绍应用激光全息技术对组合机床HY32型滑座体进行结构分析和优化。首先用散斑照相术对滑座横截面有机玻璃片模型进行加载变形试验,分析滑座体横截面结构的薄弱环节及影响因素。在此基础上设计制做了一组滑座有机玻璃整体模型作为改进型。然后应用全息双曝光法拍摄不同工况下模型前表面位移场全息图,通过对该图的定量分析及与用时间平均法拍摄的全息振型的对比试验,可对不同模型静、动态参数进行定量比较,为新型滑座体的结构设计提供了试验依据。图13幅、表3个、参考文献3种。     

滚齿机主轴-立柱动态特性分析

针对滚齿加工切削力大,对主轴-立柱刚度要求高的特点,以一台小模数滚齿机为对象,在考虑结合面刚度特性的基础上建立了其主轴-立柱有限元模型,并对主轴、立柱及主轴-立柱系统进行了模态分析和谐响应分析。分析结果表明:该机床整体刚度良好,能满足齿轮加工的需要,但主轴、导轨和滚珠丝杠为其刚度薄弱环节,低频时主要表现为主轴振动,高频时主要为导轨和丝杠振动并会引起立柱振动频率的降低,且主轴-立柱系统的整体性能在很大程度上受到结合面动力学特性的影响;此外法向切削力也是引起滚刀主轴变形的重要因素。     

基于元结构的加工中心立柱动态优化设计

以加工中心立柱为研究对象,根据快速设计及框架结构优选的设计思想,利用结构动态设计原理及有限元分析技术对立柱进行动态设计分析与结构优化.首先根据立柱结构的分析提取典型的元结构单元,然后对元结构进行拓扑优化设计,提出若干改进方案,并对改进方案进行模态对比分析.最后以立柱固有频率为优化目标,以优选的元结构为依据,对立柱进行重构设计,提高了立柱的动态特性.在机床的初步设计中,为其部件的优化设计提供了一定的参考价值,缩短了设计周期,提高了设计效率.     

基于遗传算法精密机床立柱的多目标优化

立柱是机床的核心部件之一,其动态特性是决定超精密机床加工精度的重要因素之一。以精密光纤微V沟磨床的立柱结构作为研究对象,通过仿真实验的方法给立柱的刀具磨削点上施加谐响应力,获得立柱在0～175 Hz下的动态响应参数。综合利用中心复合实验设计、响应曲面法、多目标遗传算法对立柱结构的最大谐响应振幅、立柱的质量及一阶固有频率为目标变量进行多目标优化,获得立柱设计变量的Pareto解。结果表明：经过多目标优化设计后,立柱质量没有增加的前提下,立柱的最大响应振幅大大降低,从而提高立柱的动态刚度和机床的加工精度。     

面向加工中心动态特性的立柱分析及优化设计

针对加工中心机床VMC850B的立柱进行结构优化设计,提出了一种基于神经网络和遗传算法优化的结构设计方法。基于有限元设计方法,建立立柱的三维模型,并运用ANSYS软件对立柱进行静力学分析和模态分析,采用不同的遗传算法优化结果对立柱进行优化设计,对优化结果进行静动态特性分析。结果表明,在保证立柱刚度和稳定性的前提下,优化后立柱的一阶固有频率有不同程度的提高,有效改善了立柱的动态性能,提高了整机的稳定性,为机床的进一步优化提供了有效的理论依据。     

VHT800立式车铣加工中心立柱结构静动态优化及轻量化设计

研究了VHT800立式车铣加工中心立柱结构的静动态优化及轻量化设计方法,解决了企业经验设计结构存在的静、动态性能不足以及结构过于笨重的问题.首先基于机床实际典型工况下的立柱载荷及边界条件,运用拓扑优化技术建立了体积约束下的立柱结构多工况静态性能和动态性能多目标拓扑优化概念模型;然后对概念模型进行结构刚度设计及工艺设计.最终为企业提供了新的立柱结构方案,该方案的结构刚度和一阶固有频率比经验设计结构分别提高了13.6%和17.1%,同时质量减轻了9.7%,表明该设计方法能够有效提高机床立柱结构静、动态性能并实现结构轻量化设计.     

基于ANSYS的横梁进给系统结构优化

横梁进给系统作为龙门式机床的主要组成部分,其静动态性能直接影响机床的性能,而横梁进给系统的结构决定着它的静动态特性,因此很有必要对其进行结构优化。利用有限元软件ANSYS对横梁进给系统进行静动态特性分析,分别研究单丝杠的安装位置、单双丝杠的使用以及双丝杠的跨距对横梁进给系统的影响。结果表明:单丝杠安装在十字滑座质心时横梁进给系统静动态性能最好;双丝杠两点支承比单丝杠一点支承抗扭转能力好,出现扭转振型时,双丝杠频率比单丝杠高18.9%;双丝杠的跨距越大,横梁进给系统抗扭转能力越好,对应频率最大提高36.3%。     

立式钻床立柱结构动静态分析与结构改进

以有限元理论为基础,建立立式钻床立柱结构的参数化模型,进行静态有限元分析,分析立柱结构承载及变形特点。在此基础上,采用选型法对立柱进行结构改进,并对改进后的模型做动态性能分析。结果表明:优化后,立柱静态性能提高,质量减少12.8%;立柱固有频率值与原固有频率值相近,满足结构动态性能的要求。     

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).     

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.     

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.     

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。