AOCMT机床旋转轴几何误差辨识方法的研究

以AOCMT型五轴超精密加工机床为例,运用球杆仪对其旋转轴C轴进行测量,测量时采用机床两个平动轴和一个旋转轴同时运动,测量方式分轴向,径向,切向三种。以多体系统运动学理论为基础,运用齐次坐标变换矩阵建立机床旋转轴几何误差模型,并提出一种误差辨识方法。该方法利用误差模型推导出各项误差与球杆仪轨迹偏心率关系的数学表达式,设计进行不同位置,不同高度的测量,以此可以将与位置点无关的静态误差和与位置点相关的动态误差同时分离出来,准确高效。     

五轴数控机床旋转轴误差辨识方法研究进展

随着五轴联动数控机床在先进制造行业的地位越来越重要,机床空间定位精度显得尤为重要。旋转轴误差辨识和补偿是提高零件加工质量的一大重要指标。分析和比较近年来国内外基于球杆仪和R-test装置的五轴机床旋转轴误差辨识方法的主要特点,总结了旋转轴误差在不同定义下的辨识方法,从方法的可靠性、精度指标以及可行性等方面来综述该方法对五轴数控机床的应用价值。根据辨识原理的不足,系统性地指出了目前五轴数控机床旋转轴误差辨识存在的主要问题,并对未来的进一步研究提出了建议,为五轴数控机床旋转轴误差辨识方法提供了参考。     

基于球杆仪的数控机床误差识别与补偿

论述了数控机床几何误差的球杆仪识别及软件补偿技术。提出了从Renishaw球杆仪测量数控机床的联动误差数据中识别反向间隙、直线度、垂直度、定位误差的一种方法;建立了机床结构的每个误差元和切削刀具相对工件位置误差相联系的通用数学模型;用球杆仪在数控机床上进行补偿前后加工轨迹的测量实验表明该方法效率高、效果显著。     

基于SAPSO-GA算法的高速曲轴随动数控磨床几何误差辨识方法

以某型数控曲轴磨床作为研究对象,对其结构和运动进行分析,推导出曲轴磨削时理想的砂轮轨迹方程。根据多体系统理论建立含有误差参数的模型,并推导出机床-工件和机床-刀具的运动链位置矩阵,得出机床精密加工的约束方程。对磨床的几何误差进行研究,建立几何误差模型。为快速、准确辨识出各项几何误差,提出一种混合SAPSO-GA算法。通过对比球杆仪测量补偿前后的运动轨迹,分析补偿效果。结果表明:所提方法提高了辨识准确性,通过补偿大大提高了曲轴随动磨床的加工精度。     

5轴数控机床空间误差模型及辨识方法研究

对于5轴数控机床而言,多轴插补存在着大量的耦合现象,对于空间误差主要存在着进给轴直线误差与旋转轴旋转误差。依据原有的辨识方法,大多改变球杆仪安装高度与球杆仪长度方法,该方法容易在调整过程中加入干扰误差,导致求解结果不准确。文章提出了一种改变球杆仪工作空间轨迹的方法,并依据此方法进行空间误差建模工作。在使用球杆仪的基础上,结合激光干涉仪,可同时进行两个坐标系共12项误差元素的辨识,经试验结果验证,可求得刀具坐标系与工作台坐标系旋转误差元素精确解。     

机床工作台精度测试的球杆仪空间PPSPS机构方法

提出了球杆仪测试机床两轴工作台精度的机构学分析方法。建立了球杆仪测试机床两轴工作台精度的空间PPSPS五杆机构模型,包括球杆仪的两个球副(S)和一个移动副(P)以及机床工作台的两个移动副(P);给出了基于机构模型的比例不匹配、不垂直度、反向越冲和反向间隙的误差辨识方法。实验结果表明,PPSPS机构模型可以一次辨识出球杆仪安装位置误差、机床移动副的方向偏差和移动副的误差运动,提高了测试效率; PPSPS机构法不作平面假设,测试结果与安装位置无关。     

基于空间样条曲线的数控五轴机床误差辨识研究

在划分球杆仪空间误差辨识区域的基础上,基于NUBRS空间样条曲线生成辨识轨迹。分析球杆仪空间辨识原理,并依据此原理建立适用于NUBRS空间曲线的误差辨识模型,该模型包含18个误差因素。依据五轴机床多体运动学的分析结果,提出了一种空间误差辨识方法。通过激光干涉仪的测量及误差补偿,在消除9项空间位移误差的基础上,使用生成的NURBS曲线对剩余9项角度误差因素进行辨识。经实验验证,在进行NUBRS曲线修正后,该方法可有效辨识出3个坐标系中的18项误差因素。     

基于球杆仪的VMCL600型立式加工中心精度检测与分析

基于球杆仪的误差检测原理,通过球杆仪检测VMCL600型三轴立式机床5个不同位置的误差,找出影响该型号加工中心几何精度的主要因素是垂直度误差、y轴和x轴的反向间隙、比例不匹配误差等。分析了这些误差产生的原因、对加工精度的影响并提出相应的解决措施。     

非正交五轴数控机床旋转轴误差辨识方法的研究

针对国内外对于非正交数控机床的斜摆轴B轴误差辨识研究较少问题,基于多体系统理论建立非正交五轴数控机床运动误差模型,此模型包含了旋转轴B轴的共计12项静态误差和动态误差,在对此运动误差模型进行数学表达与分析后,结合Renishaw公司的QC10球杆仪测量方式设计了8种不同测量模式。最后结合测量结果可实现斜摆轴B轴的12项误差辨识,快速高效。经试验验证,这种辨识方法测量结果精确,可用于非正交五轴数控机床旋转轴误差辨识。     

车铣复合数控机床空间误差建模和补偿

空间误差是影响车铣复合数控机床零件加工精度的最重要因素，现有方法对机床各轴的定位精度提升效果不好，为此设计车铣复合数控机床空间误差建模和补偿方法。忽略机床两个旋转轴的位置无关误差，通过齐次坐标变换理论构建其几何误差辨识模型，对几何误差辨识模型进行简化，实现两轴的几何误差辨识。在工件坐标系下，根据旋转轴几何误差辨识结果，采用多体理论构建机床空间误差模型。基于此误差模型，利用理想状态的逆运动学设计同步空间误差补偿策略，通过迭代方式对各轴补偿值进行计算，实现空间误差补偿。测试结果表明：设计方法补偿后，实验机床X轴、Y轴、Z轴的定位精度提升了0.6μm,B轴、C轴的定位精度提升了4″、3″,各轴的重复定位精度有很大提升，机床的反行程实验圆度也有所提升。     

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.     

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.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.