数控机床热变形误差补偿技术

热变形误差是影响机床加工精度的重要因素之一,通过实时热变形误差补偿可以提高数控机床加工精度.本文在分析产生机床热误差的原理的基础上, 探讨了热误差的测量方法,利用多元线性回归方法建立了机床热变形与温升之间的数学模型.应用数控系统的PLC补偿功能,对XH178加工中心加工过程中的热误差进行了实时补偿.实验结果表明误差补偿量达到80%以上.     

数控机床三维空间误差建模及补偿技术研究

为了提高数控机床的加工精度,解决由机床三维空间误差引起的工件加工质量降低的问题,在研究多体系统理论误差建模技术的基础上,提出离线补偿和嵌入式补偿两种补偿策略。离线补偿是基于数控加工程序的修正补偿,将机床三维空间误差映射到数控加工程序,通过修改加工程序实现对机床的三维空间误差补偿;嵌入式补偿是基于数控系统的在线补偿,将机床三维空间误差融合到数控系统中,通过修正数控系统中的数据流实现对机床的三维空间误差补偿。实验表明,在不影响机床可靠性的前提下,两种补偿策略均显著提高了数控机床的加工精度。     

高精密数控机床的非线性误差分析、控制及补偿

误差控制及补偿是提高数控机床精度的重要手段,因此误差模型的建立与分析显得至关重要.本文详细阐述了数控机床几何误差、热误差、切削力误差和控制误差的基本概念、起因、建模及参数辨识,综述了误差研究现状,并对今后的研究方向进行了展望.对减小误差的控制策略和误差综合软件补偿两个方面进行了探讨.为提高数控机床的加工精度提出了可行的思路.     

基于FANUC系统的螺纹误差测量与补偿

螺距误差是影响数控机床加工精度的重要因素.根据误差产生原因,介绍数控机床螺距误差补偿的依据和原理;以某一型号数控车床为例,详细说明了利用激光干涉仪实现误差测量及补偿的具体方法.结果表明,该补偿方法能较大程度提高数控机床的加工精度.     

基于FCM聚类和RBF神经网络的机床热误差补偿建模

热关健点的选择和热误差建模技术是决定热误差补偿是否有效的关键,对提高数控机床的加工精度至关重要.为了实现对数控机床热误差的补偿控制,文章利用模糊C均值(FCM)聚类方法,对机床上布置的温度测点进行优化筛选,将温度变量从20个减少到4个,然后给出了基于RBF热误差补偿建模方法.通过建模实例表明,文章提出的建模方法,在保证补偿模型精度的同时有效减少了温度测点,降低了变量耦合影响,并提高了补偿模型的鲁棒性.     

BF-850B立式高速数控机床精度检测及误差补偿研究

机床在加工的过程中会因为物理变形和热变形,使得加工零件的精度难以保证,因此必须对运动中的影响机床精度的误差源进行误差分析及实时补偿。利用激光干涉仪和球杆仪对数控机床定位精度进行检测,并建立了关于机床变形的检测数据的数学模型,确定了定位误差补偿方法,同时以具体的数控机床为例进行了定位精度检测与误差补偿,最后对补偿效果进行了分析。结果表明：该定位误差检测及补偿方法具有可行性与实用性,使数控机床的定位精度得到了显著的提高。     

西门子840D数控系统温度误差补偿的研究与应用

温度变化可以产生数控机床热变形误差,从而影响加工精度.介绍了西门子SINUMERIK 840D数控系统温度误差补偿的原理及相关系统参数,采用Pt100型热电阻设计了温度误差补偿系统的硬件,同时进行了PLC程序的开发.     

模糊神经网络在精密卧式加工中心热误差的预测

为了提高精密数控机床的加工精度,减少精密机床的热误差,文章提出了模糊神经网络径向热误差的建模方法。以数控加工中心关键点的温度和主轴径向的热变形量的关系为基础,应用模糊神经网络建模法,采用精密卧式加工中心主轴径向热误差的数据,对机床主轴热误差进行建模与预报。从数控机床主轴建模试验结果分析表明,模糊神经网络预测模型能够较为精准的对机床主轴径向热误差的做出预测,在实际应用中有利于提高机床的补偿精度,对数控机床热误差补偿提供参照。     

基于PMAC数控机床定位精度控制研究

数控机床定位精度和重复定位精度直接影响数控机床的加工精度。通过分析影响数控机床定位精度的原因,利用系统螺距误差补偿方法对数控机床进给系统的定位精度进行补偿。试验结果表明：该误差补偿策略显著提高了系统的位置精度和运动精度,为提高机床的加工精度奠定了基础。     

基于多体系统理论的数控机床加工精度几何误差预测模型

针对多轴联动数控机床加工精度误差补偿问题,从分析数控机床误差产生机制和建立精度误差补偿模型的角度,提出基于多体系统理论的数控机床加工精度几何误差预测模型。分析B-A摆头五轴龙门数控机床的拓扑结构关系、低序体阵列、各典型体坐标变换,推导出B-A摆头五轴龙门数控机床的精度几何误差预测函数模型。采用平动轴十二线法误差参数辨识算法,计算出B-A摆头五轴数控机床21项空间几何误差,为精度几何误差预测函数提供有效的误差参数。该精度误差参数建模方法,对不同结构和运动关系的数控机床具有通用性,为后续数控机床误差动态实时补偿提高切削加工精度提供了理论基础。     

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.     

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.