基于模态实验的机床进给系统的分析

基于模态分析理论,应用锤击法对机床进给系统进行了实验模态分析。研究了该机床进给系统的动态特性,获得了该机床进给系统的固有频率、阻尼比和模态振型。通过对机床进给系统各阶模态振型的分析,找到了结构的薄弱环节,并为进行机构优化设计提出了改进措施。     

高速数控车床进给系统静动态特性分析

高速数控车床的进给系统是重要部件,其静动态特性对机床整体性能的影响非常突出,应用ANSYS软件对高速数控车床进给系统进行了有限元分析.为了提高分析效率,对高速数控车床进给系统原始设计进行了简化,这些简化均不会对整体应力分布有明显影响.建立了高速数控车床进给系统有限元模型,分析其静态特性.通过模态分析得到高速进给系统固有频率和主振型,为高速数控车床的动态性能评估提供依据.     

液压金刚石飞切机床整机模态分析

以我国自主研制的某液压金刚石飞切机床为研究对象,对考虑地基的机床整机动态性能进行研究。使用UG和ANSYS Workbench联合仿真对机床整机进行有限元模态分析,得到机床的前6阶固有频率和振型;运用模态测试系统对机床整机进行模态测试,基于实模态参数识别方法获得机床的模态参数。通过有限元仿真与试验结果对比分析发现,前6阶固有频率误差均不超过10%且对应模态振型基本一致,验证了研究结果的正确性。机床整机低阶模态振型表现为床身系统相对地基的整体转动与平动,说明机床整体机构设计合理,为机床整机进一步的时变多体动力学规律预测奠定了基础。     

基于有限元法6-UPS并联机床模态分析

文章应用有限元法,对一种6-UPS型并联机床进行了详细的模态分析,分别获得了该机床的低阶固有频率及其对应的振型和振型动画,通过对分析结果进行数据处理,得到了该机床的低阶固有频率在其工作空间中的分布规律,为机床的结构设计以及进一步深入的动力学分析提供了可靠依据。     

磁悬浮直线进给单元工作台模态分析

磁悬浮直线进给单元是一种新型的机床功能部件,振动问题是其结构设计中所面临的问题之一,它会造成机床的加工误差,影响零件的加工精度和表面质量。建立了进给单元工作台的三维有限元模型,利用有限元分析软件ANSYS对工作台初始模型进行模态分析,求得其固有频率和振型,并据此改进工作台的结构,以便在设计阶段预测工作台的性能,并为工作台的结构优化提供理论依据。     

KDP晶体超精密加工机床主轴系统模态分析

KDP晶体超精密加工机床的加工精度与主轴系统的振动存在着密切的联系。为了解决KDP晶体超精密加工机床的加工稳定性差、精度难以保证的问题,利用ANSYS Workbench软件建立了主轴系统的三维有限元模型,在此基础上对机床主轴系统进行模态分析,得到主轴系统的前6阶模态频率和振型并分析了主轴系统的模态频率及振型之间的关系。最后对主轴系统进行模态实验,实验结果与有限元分析之间基本吻合,最大误差为4.9%,验证了有限元分析结果的可靠性,为KDP晶体超精密加工机床主轴系统的优化设计以及轻量化研究奠定了基础。     

某机床计算模态分析及其实验验证

为了优化机床的动态性能,进一步提高机床的加工精度和加工效率,分别利用计算模态分析方法和实验模态分析的方法对一数控机床的动态特性进行了研究。得到了该机床的前三阶模态的固有频率,阻尼比和振型。通过对计算和实验结果的对比分析发现前三阶固有频率误差分别为8.7%,9.8%和8.1%,阻尼比误差分别为18%,9.3%和17%,模态振型基本一致。发现在低阶时计算模态分析准确度较高,该机床的薄弱环节为其立柱。提出的方法和得到的结论可应用于机床动态特性的设计与研究中。     

龙门铣床双摆头动力学特性实验研究

结合实验模态分析技术对龙门铣床双摆头的动力学特性进行研究。对双摆头结构进行模态测试，获取频率响应函数，并进行拟合，分析得到结构固有频率、阻尼比与振型等动力学参数；对安装在双摆头上的螺旋立铣刀进行锤击实验，获取机床-主轴-刀具系统的加速度频率响应函数，结合再生颤振理论，预测其铣削颤振稳定域。根据可视化的整机振型，提出改进机床结构的方案，并提供合理的切削参数。     

考虑结合面影响的立柱-滑座动态性能分析

立柱作为机床的重要组件，直接影响机床的加工精度。由于立柱与滑座间的结合面对结构的动态性能有重要影响，该研究以静力分析所得接触面节点压力为桥梁结合分形理论模型与APDL有限元分析软件对立柱-滑座系统进行模态分析，获得系统考虑结合面时的系统固有频率及相应振型，以完成立柱-滑座系统动态性能分析，从而为结构的设计优化提供理论基础。     

微小型车铣复合机床模态分析

微小型零件切削加工设备精度的提高对于微小型结构件切削加工质量的提高起到巨大的作用.通过对某大学自主研制的微小型车铣复合机床KNC-50FS进行模态测试,得到该机床的低阶模态振型,并通过切削实验进行验证.模态分析结果为机床颤振研究和加工参数选择提供了基础.     

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。