面向开放式数控系统的高性能自适应插补算法的研究

以PC-based开放式数控系统为平台,提出了一种具有数控代码超前解释功能和微小路径自适应前瞻插补的改进型插补算法,以提高刀具插补的速度和精度,同时还可以减少机床加工时的冲击,提高零件的加工质量。以圆弧的三次NURBS插补为例,经前瞻加减速处理后,能够提前预测曲线的变化趋势,并及时的调整插补进给速度,减少了机床加工时的冲击。仿真测试结果表明,插补运算时间很小,插补运算效率大大提高,达到了较好的实时性和平稳性要求。     

基于Cox-de Boor递推的任意次NURBS曲线插补算法的研究与仿真

论文基于Cox-de Boor递推算法实现了任意次NURBS曲线的插补,利用差分插补方法来预估参数,结合机床实际加工过程中所必需满足的条件,将进给速度,机床最大加速度,最大弓高误差分别约束的参数进行比较,优化出最佳参数值,实现了速度自适应控制。论述了控制顶点、节点矢量、权因子对NURBS的影响,利用二分法线性搜索节点区间,给出了系统生成的NURBS曲线插补的NC代码形式,列出了整个插补算法的流程框图,在C++builder开发环境下完成了对任意次NURBS曲线的插补仿真,验证了算法的可行性。     

基于Windows的全软件数控系统实现方法研究

以基于Windows操作系统的全软件数控系统为例,论述全软件数控系统实时控制及非实时控制两部分内容的具体安排方式及数据通信方法,并给出全软件数控系统定时时钟的测定及中断级别的提升方法,以满足数控进给加工中的加减速控制及插补运算等对实时性的要求。试验结果表明:采用这种方法实现全软件数控,可使控制系统的进给速度得到显著提高。     

NURBS曲线插补的运动规划与自适应速度插补

文章整合了以基于曲率速度插补算法与自适应速度插补规划算法,分析了NURBS曲线的特点和NURBS曲线插补的参数值的求取方法;构建了基于曲线几何特性与动力学特征插补器,几何模块提出如何决定NURBS曲线的速度尖点,并根据速度尖点信息将NURBS曲线划分为曲线段,依据弓高误差及曲线曲率规划进给速度;机床动力学模块依据每段曲线长度对加加速度控制,对于每段曲线采取相应的加减速控制规划,实现了基于S形速度曲线的加速度平滑处理,与传统插补方法相比,该插补器能够保持高速度和高精度加工性能,而且能够抑制在插补过程当中产生的轮廓误差和速度波动.     

一种新型自动切管机床的研制

在分析现有各种切管机床的基础上，基于圆弧插补理论，提出通过水平和垂直进给步进电机实现相应方向的切削进给，从而切割分率管材的新型自动切管机床的设计。该机床具有结构紧凑、切割效率高、刀具寿命长等特点。     

梯形加减速在五轴联动开放式数控系统中的简化实现

加减速控制是数控系统插补器的重要组成部分,是数控系统开发的关键技术之一,在多坐标曲面加工过程中,需要对机床的进给速度进行加减速控制。针对传统梯形加减速控制策略不能直接应用于数控插补的问题,对该加减速控制策略进行了改进,并简化了其实现过程。结合五轴线性插补加工方式,详细介绍了该加减速控制方法在开发的开放式五坐标数控系统中的实现过程。铣削实验表明,该方法能使机床的加工速度变化平稳,加工效率和加工质量得到了明显的改善。     

基于NURBS曲线的扩径头模块插补算法

在分析三次非均匀有理B样条(NURBS)曲线原理的基础上,提出了NURBS曲线的实时插补算法.该算法通过插补预处理以及合理的近似计算,大大减小了插补计算的时间;并且列出了插补误差和进给步长自适应控制,从而实现高速高精度插补加工.     

基于16位单片机控制的普通车床进给系统数控改造设计

提出了采用16位单片机数控系统,对普通车床进给系统进行经济型数控化改造的设计方案,设计和改造了车床的横向与纵向进给系统机械传动机构和自动换刀系统机构.进给系统和自动换刀系统由80C196单片机数控系统控制,根据进给系统设计参数,完成了普通车床进给系统经济型数控化改造的设计、校核与计算.模拟调试与实际运行表明,改造后的机床进给系统稳定性、准确性、快速性比以8位单片机为核心的经济型数控车床有较大改善,零件的加工质量和生产率都得到较大提高.     

基于差分插补原理的多维线性空间插补与仿真

为了实现采用差分插补原理的数控系统能够进行多维线性空间插补,以平面直线插补为基础,对差分插补原理进行了再研究。从差分插补原理的基准轴与非基准轴进给判定中,找到了实现基于差分插补原理的多维线性空间插补的关键点。通过对多维线性插补的分析,给出了多维线性插补的具体流程及其差分代码的初始化,实现了基于差分插补原理的多维线性空间插补。该插补方法简单可行,易于实现多轴控制。通过空间直线插补实例分析以及刀具路径的插补仿真,进一步说明了基于差分插补原理的多维线性空间插补方法能够满足空间多维数控加工的要求。     

基于STM32的改进DDA插补器设计与分析

针对普通DDA进给速度不够快、插补误差较大、插补脉冲分布不均匀等不足,利用改进的DDA算法作为插补算法,以基于ARM Cortex-M3处理器内核的STM32微控制器为插补控制核心,设计了DDA硬件插补系统,实现了高速高精度插补。借助Keil uVision4软件开发环境,利用C语言分别设计了普通DDA和改进DDA的算法程序,并对两种方法的插补结果进行了对比。结果表明:与普通DDA相比,改进DDA在插补速度与插补精度上均有一定的提高,控制器溢出脉冲分布更加均匀。     

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。