新型无杆飞机牵引车夹持举升机构静刚度分析

研究一种新型无杆飞机牵引车夹持举升机构的静刚度建模方法。对机构的夹持举升动作进行分解,重点研究后挡板闭合后提升机轮的过程。在完成对该机构位置逆解分析的基础上,分析连接承载斗的各杆件受力及变形情况。利用虚拟机构法,根据速度映射关系,求出杆件变形引起承载斗的位姿变化,再利用小变形叠加原理,求出机构的整体变形。根据外载荷与机构整体变形之间的关系,求出机构的静刚度矩阵。通过算例确定机构的静刚度在工作空间的分布规律,并利用ANSYS软件验证了该建模方法的正确性。     

无杆飞机牵引车夹持举升机构的运动学分析

夹持举升机构是无杆飞机牵引车同飞机直接相连接的部分,需要完成夹持机轮并抬离地面的动作。建立了常见的夹持举升机构的机构简图,利用K-G公式计算夹持举升机构的自由度。以D-H变换矩阵作为建模工具,建立其位姿运动方程,求出其解析正解,利用解析法求出其理论的速度表达式。结果表明:机构的自由度数与机构主动件的数目相同,具有唯一的确定运动,D-H变换矩阵与几何方法求出的位姿表达式相同,角度变换的仿真结果与理论计算值近似。证明了机构的有效性,并为夹持举升机构的创新设计和进一步的机构综合提供了参考。     

基于AMESim的自卸汽车举升机构的建模与仿真

以前置直推式自卸汽车举升机构为研究对象,利用AMESim软件建立举升机构液压系统模型。根据整个机构的几何关系计算举升过程中负载的变化;设置一些主要的参数,对整个举升机构进行仿真。根据仿真结果得出液压回路压力对举升缸的影响。这种方法较以往的编程建模方法和软件协同建模方法更加简便和有效,具有一定的推广价值。     

直线滚动导轨静刚度研究

针对机床中重要的运动结合部——直线滚动导轨的刚度进行理论分析，提出一种直线滚柱导轨静刚度计算的方法。推导了在垂直力、水平力和转矩联合作用下直线滚柱导轨受力变形的基本方程，应用赫兹接触理论建立了承载和变形的关系；利用该分析方法对某商用导轨的刚度特性进行了分析和数值计算。实例计算验证了理论分析和计算软件的正确性。     

大型锻造操作机钳头夹持机构受力分析

针对3000kN／7500kN·m操作机钳头夹持机构,分别夹持不同重力、不同夹持力矩的锻件,在钳杆不同转角位置、钳口不同夹持直径等工况下,进行三维建模和有限元仿真。分析在复杂工作条件下各主要零部件的受力状况,得到相应零部件上危险点应力值的变化规律,根据材料力学性能对其进行静强度和疲劳强度校核。结果表明,材料的静强度及疲劳强度完全满足使用要求。     

三移一转并联机构运动学分析

为满足钢铁搬运行业的应用需求,提出了一种新型三移一转并联机构。该机构的每条分支包含驱动支链RPR和执行支链RPaPaR,其执行支链中的平行四边形铰链Pa具有封闭环结构特性,使机构有较大的刚度。借助螺旋理论分析了该并联机构的自由度。采用机构杆件之间的几何条件以及坐标变换求出机构的位置逆解,得到驱动杆件与动平台位姿的关系。根据钢铁搬运任务需求,使用五次多项式计算出动平台分段驱动函数,在仿真软件ADAMS中实现机构末端由初始到目标位置的轨迹规划,并由驱动杆的仿真数据与计算数据一致,验证了机构位置逆解数学模型的正确性。利用PID控制器搭建机构的位置控制模型,实现动平台的实际位置与理论位置轨迹的一致性。使用CAD变量几何法得到了机构的可达位置工作空间,并对其进行了分析,得出工作空间分布特点。     

一种弹性折叠梁的刚度建模分析

刚度对微动平台的驱动行程具有极大影响,为了有效提高微动平台的行程范围,提出一种弹性折叠梁代替传统的弹性薄板结构。首先将整体结构划分为横梁和竖直梁两种不同单元,并建立相应的刚度方程,然后和各个节点的力平衡方程相结合,得到单侧结构的刚度方程。再根据结构的对称性,建立另一侧结构的刚度方程。最后根据两侧结构的变形协调关系推导出弹性折叠梁的整体刚度矩阵。最后给出了数值算例,表明刚度建模方法在分析驱动载荷方向的变形时候偏差很小,但是其他方向的牵连变形精确度较低,因此应以ANSYS分析结果为准。     

大型镁合金压铸机的有限元建模与分析

压铸机的整体变形情况对压铸机性能和铸件质量有重要影响。本文通过有限元方法，基于ANSYS平台，利用特征建模和等效的方法，对大型镁合金压铸机进行整体建模，通过计算获得压铸机在满载工作时的变形情况和应力场分布，并对其强度刚度进行验证。从整个分析结果来看，目前镁合金压铸机的结构设计可以满足工程要求，但仍有改进余地，本文工作为压铸机设计提供了重要的参考。     

自卸车举升机构的显式统一模型研究

举升机构的分析计算是自卸车设计的关键内容,传统的分析方法主要有以铰接点坐标为变量的二元二次方程组方法和以杆件角度为变量的三角代数方程方法,这两种方法往往存在判根取舍的麻烦,而且不同类型举升机构的方程和判根准则也存在很大差异。基于线性变换与向量代数理论,提出一种无需判根的举升机构分析新方法,用统一的显式线性模型描述四种典型举升机构,只需要进行简单的线性代数运算即可得到任意状态下各铰接点的位置,仅需要求解二阶方程组即可得到各杆件受力,特别适合于编程实现。通过不同举升机构的分析实例,验证了所提出的模型和分析方法的有效性。     

基于kane方法的关节机器人举升机构的动力学分析

以应用于平板玻璃基板搬运领域的关节机器人的举升机构为研究对象,针对举升机构由串联的两个平行四连杆机构组成以及各组成构件间存在着复杂的动力学非线性耦合关系的特点,采用kane方法建立了该机构的递推动力学方程,基于动力学方程对举升机构的动力学特性进行了仿真分析,分析的结果表明延长驱动关节的加速时间是提高举升机构运行平稳性的可行方法,从而为机器人举升机构的优化设计和平稳控制提供了理论依据.     

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.     

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。