考虑热影响的6300kN多向液态模锻液压机机身结构变形分析

液态模锻模具在生产过程中具有一定的温度,使机架同时受到热和力的作用。在研究液态模锻液压机机架结构特点的基础上,以Ansys Workbench软件为平台,综合考虑温度和受力情况对机架的影响,对液压机机架进行了有限元分析。结果表明:采用结构静力分析与热应力耦合分析时,机架的最大变形都出现在上横梁液压缸法兰作用的环形面上,分别为0.9938和1.2735 mm;考虑热影响时液压机工作台的应力应变值明显增加,并且立柱的最大变形部位发生变化,由结构静力分析时的中上部变为中下部,径向变形明显增大,由0.1827 mm上升为0.6148 mm。     

H型直线电机工作台控制技术研究

分析了直线电机驱动的H型运动平台的结构特点,建立了直线电机H型工作台运动系统,研究了H型工作台双边直线电机基于增量式编码器同步寻相的实现途径并设计了工作台双电机同步寻相程序;研究了几种双边电机同步运动控制的方法,通过分析每种控制方法的原理和实验结果表明,多电机同轴控制是比较适合H型工作台双边直线电机高精度同步运动的控制技术.     

XK2310数控铣床工作台系统的静动态特性研究与分析

XK2310数控铣床工作台系统是机床的关键部件之一,其静动态特性对零件加工精度有很大的影响,为了提高XK2310工作台系统的静动态特性,利用ANSYS Workbench 14.0对工作台系统进行静动态特性分析。静态分析的目的是检验工作台系统是否满足静力学特性,静力分析结果表明,在切削载荷作用下,工作台的最大应力、应变值都远远低于材料的极限值,最大变形量在精度范围内;动态特性分析的目的是了解工作台系统在切削加工时,主轴产生的激励频率是否会引起工作台系统共振,模态分析结果表明,当主轴转速为1539r/min、2052r/min、3077r/min、4214r/min时,产生的激励频率与工作台系统的第1、第2阶固有频率相等,将引起工作台系统共振。     

基于数值模拟的汽车半轴热摆辗成形工艺研究

采用有限元分析软件Deform对汽车半轴热摆辗成形过程进行分析,重点研究了热辗压成形过程中等效应力分布及变化规律。研究结果表明:在成形过程中,工件最大变形程度出现在半轴的法兰区域,且在成形过程中逐渐向底部移动,最大等效应力从开始阶段的193 MPa增加到成形结束时的302 MPa;此外,摩擦系数从0.1增加到0.5时,最大等效应力从235 MPa增加到304 MPa。并通过实验验证了模具下模表面涂抹Mo S2或者机油润滑剂,可以有效减小工件变形程度。     

基于ANSYS的液压剪板机刀架有限元分析

刀架是液压剪板机的重要组成部分,板料的剪切精度很大程度上与刀架的结构有关.目前刀架上承受的剪切力计算大多还是按均布载荷来分析的.采用ANSYS中的ADPL语言编写移动载荷各个载荷步的信息,研究了移动载荷作用下刀架的变形、等效应力和等效应变,并与施加均布载荷时的情况进行了对比,得到的最大等效应力比均布载荷时大18.9%,结果表明施加移动载荷在刀架结构分析中的重要性.对比移动载荷下刀架转轴处作用力和碟簧压力不同分别取不同值情况下刀架的等效应力,发现两处作用力对刀架的影响较小,对比了液压缸处作用力解析计算和数值模拟计算的结果,发现两种结果误差为9.8%,由此可以看出施加移动载荷得到的结果是可靠的.     

耳轴式回转工作台热变形误差补偿研究

针对五轴加工中心直驱回转工作台热变形导致加工误差的问题,以耳轴式回转工作台虚拟样机为对象进行热变形补偿研究。基于R型聚类分析与热误差敏感度理论对温度测点进行优化选取,在降低测点数的同时保留了温升与热变形的对应关系信息。借助MATLAB建立BP神经网络误差预测模型,通过采集工作台特定测点的温度预测台面中心点的热变形位移量,得到误差拟合曲线与补偿残差。优化网络结构,得到最佳的隐含层节点数,提高模型的预测精度。研究结果可为五轴加工中心热变形误差补偿与BP网络的优化设计提供参考。     

某飞机小曲率TC4薄板件热冲压及回弹研究

为减小某飞机小曲率TC4薄板热冲压成形回弹,对热冲压过程进行有限元分析.采用正交试验方法,选取成形温度和冲压速度作为影响因素,建立L16(42)正交试验表得到16组数值模拟方案,分析了板件在热冲压完成时的应力分布.结果表明:减小板件最大等效应力可有效降低其应力分布不均匀性;对最大等效应力模拟结果进行极差分析和方差分析,...     

五轴加工中心耳轴式工作台动力学分析与仿真研究

针对加工中心工作过程中出现的工作台变形、振动影响零件精度等情况,以往均是凭经验解决,不能有效发现实际存在问题的潜在规律性。文章通过计算机建模与仿真技术对课题中五轴立式加工中心耳轴式工作台的进行模态分析和谐响应分析,揭示台面的固有频率、最低刚度方向、共振频率、最大变形等可能造成潜在安全隐患的工作参数。将以上结果作为实际加工参考,实现对回转工作台深层次的理论研究,通过避免以上工作参数可使工作台满足零件的加工精度要求,杜绝凭经验解决。同时文章可为耳轴式工作台台面的设计和优化提供关键性的动力学分析方向和理论基础,使工作台结构趋于规律化。     

不同引线数QFP器件焊点等效应力的数值模拟

采用有限元方法对不同引线数QFP器件焊点的等效应力进行了数值模拟,研究发现,热循环后的PCB板有向外翘曲趋势,但变形较小;陶瓷基板上翘趋势较大,总体变形较明显,且其对引线的拉伸力会加剧焊点裂纹的扩展.在最外侧存在焊点最大应变值,QFP器件鸥翼形引线焊点的焊点根部与焊趾处等效应力较大,焊点根部等效应力比焊趾处大,中间区域等效应力最小.理论计算显示QFP100器件应力最小,QFP48次之,QFP32应力最大.焊点拉伸试验结果显示QFP100器件抗拉强度最大,QFP48次之,QFP32最小,与数值模拟结果完全吻合.     

五轴联动数控磨床直线进给机构静力学分析

针对普通工具磨床和传统生产工艺方法很难加工出特型刀具的品种和刃形的问题,研发了一种五轴联动数控工具磨床,其中五轴联动数控工具磨床直线进给机构的受力和位移情况将直接影响磨床的工作性能。利用Solid Works中的simulation模块对五轴联动数控磨床的直线进给机构进行静力学分析,研究直线进给机构各处的位移和应力情况。结果表明:X轴工作台的最大应力为2 MPa,出现在X轴工作台的滑块和立柱的下部,X轴工作台的最大位移为0.000 015 88 mm,出现在立柱的中部;Y轴工作台的最大应力为2 MPa,出现在Y轴工作台中部,Y轴工作台的最大位移为0.000 003 584mm,出现在Y轴工作台的中部;Z轴工作台应力的最大值为10.3 MPa,位于Z轴工作台右侧,Z轴工作台位移最大值为0.000 030 88 mm,出现在Z轴工作台中部。     

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.