直线型超声电机在机床进给系统中的应用

文章简要比较了直线电机驱动和传统滚珠丝杠机床进给驱动的优缺点及直线电磁电机存在的问题;详细介绍了直线超声电机的运动机理,直线型超声电机相对于电磁式直线电机的优点和直线型超声电机的国内外发展和研究现状;并综述了直线型超声电机在机床进给系统中的应用研究现状.     

用于机床进给系统的双向驻波直线超声电机

近年来超声电机在机床进给系统中的应用越来越广泛，针对于传统贴片式驻波型超声电机效率低，功率小，不利于在进给系统中应用的现状，文章提出一种利用夹心式弯振换能器的激励弯曲驻波的驻波直线超声电机。运用振动理论分析了电机的致动原理：通过激励两种不同谐振频率的弯曲驻波，并结合驱动齿的合理分布，可实现双向运动。采用有限元法确定其具体结构尺寸，并验证了各驱动齿端部振动轨迹为倾向一致的斜线。制作了样机并测定了其机械输出特性，达到如下指标：最大推力14N，最高速度180mm／s。     

电极仿生微进给装置的研究

根据电火花微细孔加工的特点和仿生学的蠕动原理,利用WTDS型电致伸缩位移器件驱动,研制了一个电极蠕动微进给机构,由计算机控制可实现10~(-2)μm级的精确进给。在此基础上可以构成一个微小电火花加工系统。     

电极仿生微进给装置的研究

根据电火花微细孔加工的特点和仿生学的蠕动原理，利用ＷＴＤＳ型电致伸缩位移器件驱动，研制了一个电极蠕动微进给机构，由计算机控制可实现１０＾－２μｍ级的精确进给。在此基础上可以构成一个微小电火花加工系统。     

直线电机高速进给系统性能优化研究

高速切削技术越来越引起人们的关注。实现高速切削的关键技术之一,是开发具有高速能力的高性能数控机床。机床主轴的转速近年来有很大的提高,而机床进给系统大我仍采用滚珠丝杆传动的方式,使机床的最大进给速度受到限制,阻碍了机床高速性能的进一步发挥。本文介绍了一种采用直线电机直接驱动的机床高速进给系统。采用非线性系统稳定性分析的方法确定系统的参数,并对伺服系统性能进行实验研究。实验证明,用这种方法优化该类系统     

超声马达式微小电火花加工系统的研制

针对微小型电火花加工装置加工过程中电蚀除产物排出困难的问题，提出了差动驱动电极的方式，且每步进给包含超声频的微振动，该方法提高了加工效率。利用有限元方法对超声定子驱动原理进行了分析，求解出超声马达的合理振动模态。最后还对整个系统进行了实验验证，加工出了Ф85μm微孔和Y异形孔，实验结果表明该系统完全满足微细电火花加工的要求。．     

用于直接驱动机床主轴的大推力圆筒型永磁直线电机的研究

根据机床主轴进给性能指标的要求,计算圆筒型永磁直线电机的主要尺寸参数,然后通过有限元分析对电机的输出性能进行优化。最后设计基于各相独立电流环控制的控制方案,完成机床主轴直线电机进给系统的总体设计。设计的大推力圆筒型永磁直线电机能实现机床主轴的直接进给驱动,具有效率高,精度高,动态响应快等优点。     

微小型五轴数控机床的研制

为了满足微小复杂结构件的加工需要和机床误差补偿技术的研究,研制了一台微小型五轴数控机床实验平台,本体尺寸为580 mm×450 mm×570 mm.机床实验平台为卧式双转台结构,布局紧凑,空间利用率高,各轴采用了直线电机、直驱马达、丝杠滑台驱动方式.分析了机床的主要薄弱环节,并进行了受力分析和优化设计,仿真结果表明机床...     

一种凸轮进给伺服控制系统的研究

利用凸轮机构,结合步进电机细分驱动技术,研制了一种伺服控制系统以满足轧辊表面毛化电极微量进给的要求。实验结果表明该系统运行可靠,毛化效果受加工参数控制。     

直驱型高速数控机床进给系统设计分析及实验

为克服传统机床"旋转电机+滚珠丝杠"进给传动方式存在的弹性变形大、响应速度慢、易磨损等问题,利用永磁直线同步电机(PMLSM)设计了一种直线电机驱动高速数控机床进给系统。从理论上分析了系统机械结构对动态特性的影响,在此基础上,对最大切削力工况下的进给系统主体结构进行了刚度、强度以及模态分析,最后,实验测试了进给系统的位置精度及动平衡精度。结果表明,该进给系统结构变形量小于0.01mm,最大应力为5.7MPa,且在低阶频率范围内,主动避开1、2、5、6阶加工激振频率可使进给系统具有较高的抗振特性,同时该系统的位置精度、平衡精度均在设计指标内,有效的保证了进给系统主体结构的动态精度及稳定性。     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.