伺服压力机双动肘杆机构的设计与研究

针对伺服机械压力机双动肘杆机构双自由度的特点,采用逆推设计原理对双动肘杆机构的主肘杆系统进行解耦,以滑块下死点作为起点进行设计分析,利用矢量方程解析法与动态静力学方法建立机构运动学与动力学的数学计算模型;采用MATLAB软件优化工具箱对主肘杆系统的运动学与动力学的多目标函数进行优化,得到了满足公称压力行程滑块速度波动小以及所需机构驱动扭矩小的一组参数;采用ADAMS软件对已有的等长肘杆机构、三角肘杆机构以及双动肘杆机构进行建模仿真,并对滑块的运动状态以及曲柄所需扭矩情况进行对比分析,得出双动肘杆机构符合伺服压力机设计要求。     

曲柄驱动双肘杆传动机构的设计与优化

为加工高强度、回弹大的轻量化板材,设计了一种曲柄驱动的立式传动肘杆伺服压力机。采用ADAMS软件对比分析了两种不同传动机构的工作特性。针对曲柄立式传动肘杆机构,通过矢量法建立滑块变速移动特性的运动学方程;运用ADAMS对传动机构各尺寸变量进行敏感度分析,以减少设计变量,再运用遗传算法对传动机构进行多目标优化,以减小滑块最大速度、滑块最大加速度和机构高度为优化目标。研究结果表明,优化后的曲柄立式传动肘杆机构的工作性能有较大提高,滑块最大速度降低了8.5%,滑块最大加速度降低了37.6%,曲柄最大扭矩降低了9%,机构高度降低了1%;同时该机构具有良好的保压性能和急回特性。     

几种伺服压力机传动结构方案的分析与比较

介绍了几种不同的单驱动和混合驱动伺服压力机传动结构方案,对各自的运动学和功率特性进行了分析;在同一的负载条件下,对曲柄连杆式、单肘杆式、双肘杆式不同传动结构的单驱动伺服压力机的滑块行程、速度曲线、作用扭矩和功率消耗进行了比较;构建了轮系混合驱动三维结构模型,并从结构特征、伺服电机与常规电机所需功率以及两者间的功率比,对轮系混合驱动和杆系混合驱动伺服压力机的传动结构进行了分析.为伺服压力机的开发研究和设计制造提供了有益参考.     

变速驱动曲柄压力机运动分析

介绍了运用机构的正向和逆向分析方法为变速驱动曲柄压力机曲柄滑块机构的运动建立的数学模型,编制应用程序进行了若干示例的仿真研究,在普通曲柄压力机上实现了能满足特殊工艺要求的滑块运动特性。这一方法为实现伺服驱动曲柄压力机的运动控制奠定了基础。     

伺服式热模锻压力机关键技术的探讨

在分析传统热模锻压力机的基础上阐述了伺服式热模锻压力机的优点。伺服式热模锻压力机的关键技术包括驱动电机、工作机构和传动方案等。在驱动电机方面,分析了交流异步电机、变频调速电机、开关磁阻电机和交流伺服电机在伺服式热模锻压力机上应用的合理性。在工作机构方面,提出了将肘杆机构应用于热模锻压力机的新方法。在传动方案方面,对多电机驱动、多齿轮分散传动和多套传动机构同步方案进行了研究。最后对伺服式热模锻压力机的关键技术进行了总结。     

肘杆式伺服压力机运动学仿真与工艺轨迹规划

基于肘杆式压力机的基本结构,进行运动学逆解分析。提出一种参数化组合式正弦函数作为加速度曲线的加减速算法,规划滑块的运动轨迹,使滑块的运动轨迹更加平滑,提高了伺服压力机高速工作时平稳性,降低了对伺服控制系统瞬态响应的要求。利用Matlab平台搭建肘杆式压力机的运动学模型,由给定的滑块运动轨迹曲线,仿真得到精确的曲柄角位移、角速度和角加速度曲线,可作为伺服电机控制的输入量,为伺服压力机的控制提供重要依据,为其他伺服压力机传动机构的分析和控制提供一种可行的方法。     

回转头压力机交流伺服直驱方式的研究

随着电机调速与伺服控制方式、电机技术等的飞速发展,交流伺服直驱控制技术得到广泛应用.本文分析了目前直线电机直接驱动式、伺服电机直接与曲柄相连式、伺服电机通过减速器与曲柄肘杆等机构相连式、双伺服电机驱动丝杠螺母机构4种不同的交流伺服直驱传动方式的工作原理、输出特性以及用于回转头压力机中的优缺点.获得了交流伺服电机的转速、最大扭矩、当量负载扭矩、连续过载时间等主要技术参数选取的合理方式,并建立了相应的计算公式.     

基于ADAMS的微型压力机多连杆机构运动学及动力学分析

压力机输出部件滑块的运动学特性和各连杆铰接点的受力情况是评价微型压力机工作质量的重要指标,该微型伺服压力机多连杆机构由曲柄摇杆机构和摇杆滑块机构串联而成,并能满足压力机工作要求。通过对该多连杆机构和一般曲柄滑块机构的运动学及动力学分析作对比,阐述了该机构滑块的位移、速度、加速度及铰接点的受力情况相较于一般曲柄滑块机构的不同特性。     

基于遗传算法的双曲柄伺服压力机杆系的优化设计

双曲柄伺服压力机具有低速急回和增力的特性。通过双曲柄杆系模型的建立,借助语言编程工具,利用遗传算法,进行单目标优化设计。据此设计了双曲柄杆系参数,分析了滑块位移、速度、加速度以及大齿轮所需转矩曲线。有效降低了伺服电机功率,为大吨位伺服压力机的设计提供一定的理论计算基础。     

构件设计对伺服压力机三角肘杆传动机构动力的影响

针对伺服机械压力机三角肘杆传动机构,采用矢量方程解析法与动态静力学方法建立机构运动学与动力学的数学计算模型。在优化得到的可靠实用参数的基础上,不考虑摩擦,研究了在不同曲柄转速情况下,各构件重量、质心位置对整个机构所需驱动扭矩的影响。     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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).     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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.