链式刀库及机械手可靠性试验台设计

针对链式刀库及机械手的可靠性问题,提出并设计了一种针对链式刀库及机械手的可靠性试验装置.首先对试验台的总体方案和系统构成进行了设计,然后详细设计试验台结构、控制系统及检测系统.最后分析链式刀库及机械手的常见故障,并结合其换刀过程,提出了其可靠性试验方法,为提高链式刀库及机械手可靠性提供了实验手段和方法.     

盘式刀库及机械手可靠性增长试验方法研究

车铣复合加工中心用盘式刀库及机械手是大型复杂的机电产品.针对该盘式刀库及机械手的结构特点,进行了可靠性增长的研究.搭建了便于可靠性分析和性能检测的可靠性试验台,分析了其可靠性试验系统的组成,随后总结了盘式刀库的早期故障模式及影响,找出其薄弱环节.且针对这些故障制定了一套基于 Duane 模型的可靠性增长试验方案,绘制了可靠性增长计划曲线,并提出了后期试验跟踪及控制的方法和要点.该可靠性增长试验方法对同类刀库机械手的可靠性研究具有重要意义.     

链式刀库及机械手早期故障筛选试验及分析方法

介绍了国内外链式刀库及机械手早期故障的研究现状和现存问题.针对该系统的结构特点,采用台湾吉辅刀库为核心部件,搭建了链式刀库及机械手可靠性试验台.通过对系统常见故障模式与失效机理的分析,提出一种基于环境应力筛选的早期故障试验方法,激发其早期故障与薄弱环节,对系统缺陷进行有效排除.最后采用FMECA分析方法对链式刀库及机械手进行了定性分析,提出后续分析的方法要点.该早期故障筛选试验与分析方法对同类产品的可靠性研究具有重要意义.     

盘式刀库可靠性试验状态监测及故障预警研究

盘式刀库是加工中心的重要功能部件,其运行状态直接影响整机可靠性及工作效率。文章针对盘式刀库可靠性台架试验,设计了状态监测方案,研制并搭建了状态监测系统的硬件系统和软件系统。监测系统采用一种改进的相邻系数法对采集的状态信号进行降噪处理,建立刀库电机电流能量的时变模型,实现电机堵转故障报警;基于遗传算法(GA)与支持向量回归(SVR)理论,建立刀库机械手振动与转位偏差的预警模型,试验结果表明,GA-SVR方法可以实现刀库机械手转位偏差故障的准确预警。     

链式刀库换刀控制程序设计及可靠性保障措施

链式刀库及机械手换刀系统的控制程序设计是其电气控制可靠性的重要因素之一.以高可靠性数控系统FANUC-0iD内置PMC为逻辑控制器,对链式刀库的工作原理和换刀过程作了详尽介绍后,从刀库选刀和刀具交换两方面分析了链式刀库换刀程序设计方法,进一步在细节方面提出了相关可靠性保障措施,实现了换刀程序较好的执行效果.对类似刀库机械手换刀的软件设计有一定的借鉴意义.     

刀库及自动换刀装置可靠性熵法评定技术

刀库及自动换刀装置属于典型高可靠性要求的复杂机电系统,针对小子样产品在可靠性评定中试验信息量较少的缺点,文章利用信息熵的相关理论,提出一种可靠性数据折合与评定方法,进行不同环境试验单元之间和“金字塔”式多级系统相邻两级之间的信息折合.讨论了基于经典法的串联系统可靠性评定第一近似限.并以链式刀库及机械手的可靠性综合评定进行实例验证,证明该方法适用正确有效,在大型数控机床可靠性评定方面具有广泛的应用价值.     

链式刀库及机械手综合性能检测规范研究

针对链式刀库及机械手出现的各种故障问题,为提高其性能检测水平,结合加工中心的各项检测标准,展开对其综合性能检测规范的研究。确定了检测项目和检测方法,搭建链式刀库及机械手性能检测平台。结合平台,确定了一套完整、具体的检测规范,为其在生产和使用过程中的检测提供理论指导。     

盘式刀库及自动换刀装置可靠性评价

圆盘式刀库及自动换刀装置是加工中心的重要功能部件,也是加工中心故障部位的薄弱环节,其可靠性水平直接关系到主机的性能.目前圆盘式刀库及自动换刀装置的可靠性还没有适当的标准.鉴于此,在对国内外数控机床及其关键功能部件可靠性评价研究进行归纳分析的基础上,本文通过平均故障间隔换刀次数MTCNBF及平均修复时间MTTR指标对YP系列圆盘式刀库及自动换刀装置进行了可靠性评价.并基于可靠性加速试验数据对圆盘式刀库及自动换刀装置的故障模式、故障原因进行了分析,得到了圆盘式刀库及自动换刀装置最容易发生故障的部位、主要故障模式,可为刀库及自动换刀装置的改进设计提供依据.     

机械手的一键恢复

加工中心在机械加工中的应用越来越广泛,刀库的使用也越来越频繁,非正常停机和复位将会使刀库的机械手或刀套停在非正常位置,这对刀库的恢复造成一定的困难.本文介绍了一种一键恢复机械手的方法、基本设计思路和工作原理,给出了控制机械手的主要梯形图.     

加工中心链式刀库的设计

链式刀库结构紧凑,位置精度高,适用于技术规格较大的加工中心。其结构特点是将刀套座布局在封闭的环形链条上用来实现刀具的存储,采用机械手实现刀具的交换,换刀动作多而复杂。不仅要求各个换刀动作之间的衔接流畅,而且在换刀过程中不允许掉刀。针对链式刀库的技术要求,根据VMC630型立式加工中心的结构特点,设计与其相配的链式刀库,分析换刀过程中刀具定位、夹紧所采取措施的可靠性,归纳链式刀库在设计和调试中应把握的若干关键技术,并在试制中得到了验证。     

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.