超精密滚珠丝杠进给系统谐响应的有限元分析

以超精密滚珠丝杠进给系统试验台为研究对象,使用有限元法对其进给系统的工作台受到轴向正弦力载荷时系统的谐响应进行了分析.由于目前传统的滚珠丝杠进给系统有限元模型不能准确的分析电机轴输出端的转矩动载荷对进给系统产生的谐响应,据此提出了一种新的进给系统有限元模型,保证了其谐响应分析的准确性.并根据分析结果可知,在超精密滚珠丝杠进给系统中,电机轴输出端的转矩动载荷会对进给系统的定位精度产生不可忽视的影响.     

超精密滚珠丝杠进给系统的谐响应分析

超精密滚珠丝杠进给系统除了在工作台轴向存在外界激励,电机在启动和刹车时产生的冲击以及电机轴输出端的振荡特性都可能导致整个进给系统产生振荡,而利用目前的滚珠丝杠进给系统有限元模型不能准确地分析出电机轴输出端的转矩动载荷对进给系统产生的谐响应。针对此问题,提出一种新的进给系统有限元模型,保证了其谐响应分析的准确性。     

大行程超精密驱动系统问世

国防科大研制成功了我国首台大行程超精密驱动系统，它在２５００ｍｍ的大行程上运动，分辨率可达到亚纳米级。 该系统采用了当今扭轮摩擦传动的新概念，对传动过程的运动学问题和动力学问题进行了分析，建立了进给系统运动分辨率的数学模型，分析了影响机床进给定位精度的种种因素及提高控制分辨率的方法。在扭轮机构的动力学问题上以及导程的负载特性上，提出了自己的观点，为解决系统高运动分辨率和长距离驱动这一矛盾奠定了理论基础。在系统的结构设计中，实现了各个环节的优化。在系统设计制造工艺方面有创造性的贡献。大行程超精密驱…     

一种凸凹模独立驱动的冲压机

对凸凹模独立驱动提出了有效的实现技术,即通过精密滚珠丝杠对凸凹模分别进行独立驱动并准确定位;在滚珠丝杠的端部安装制动器,当凸凹模具运动到位,先通过制动器制动滚珠丝杠,然后再开始冲压.具备该技术的压力机,可以实现对大宽度板材的加工,减少生产工序,降低生产成本.     

西门子1FN1直线电机的参数配置及转子位置同步

前言目前,市场上高速高精加工机床的进给驱动,主要由传统的旋转伺服电机和精密高速滚珠丝杠组成,从伺服电机到移动部件间有一系列机械元件,势必存在弹性变形、摩擦和反向间隙,相应造成运动滞后和其他非线性误差,而且滚珠丝杠副的移动速度和加速度已提高接近极限。直线电机的出现,实现了机床直线轴的直接驱动,     

基于LabVIEW的精密数控机床进给系统实验台的构建

针对数控机床进给系统进给运动中产生的振动直接影响数控机床的定位精度和加工精度,导致故障率升高等问题,构建了基于Lab VIEW的数控机床进给系统实验台。采用交流伺服电机作为动力源,用滚珠丝杠螺母副、滚动直线导轨等构成其传动部分,使用脉冲式运动控制卡作为上位机,用Lab VIEW软件实现对电机的驱动与控制。实验结果表明,实验台实现了对刀架的速度、行程的精确控制,为后期数控机床进给系统的实验分析打下了基础。     

基于热阻网络法的一种新型双驱动进给系统热动态特性研究

设计了一种新型的微量进给机构,以"螺母旋转式滚珠丝杠副"为主要传动部件,丝杠和螺母分别由两个电机驱动并同向旋转,其运动合成微量进给,研究在不同电机速度组合下该新型微量进给机构的温度场及丝杠热伸长变化情况。基于传热学理论以双驱动进给系统为研究对象,利用热网络法建立该系统的热平衡方程组,获得温度场分布模型,结合机械热变形理论,用所建立的温度场模型预测双驱动滚珠丝杠的轴向热误差。得到双驱动微量进给机构随螺母、丝杠速度变化的温度场及丝杠热伸长模型,并通过实验验证了所建立模型的准确性。     

我国首台大行程超精密驱动系统研制成功

由国防科大研制的扭轮摩擦驱动系统，采用了当今扭轮摩擦传动的新概念，对传动过程的运动学问题和动力学问题进行厂分析，建立了进给系统运动分辨率的数学模型，分析了影响机床进给定位精度的种种因素以及提高控制分辨率的方法。在扭轮机构的动力学问题以及导程的负载特性上，提出了自己的观点，为解决系统高运动分辨率和长距离驱动这一矛盾奠定了理论基础。在２５０ｍｍ的大行程上运动分辨率可以达到亚纳米级。我国首台大行程超精密驱动系统研制成功@孙福     

机床滚珠丝杠进给系统热误差研究现状与发展趋势

机床的热误差已成为影响机床工作性能的最主要因素之一,滚珠丝杠作为机床进给系统关键部件,其热变形直接影响着机床的加工精度。因此,对滚珠丝杠进行热误差控制与补偿十分重要。过去几十年里,国内外学者对滚珠丝杠进给系统热误差研究可以分成三部分内容:热特性研究,热误差建模和热误差补偿。先通过滚珠丝杠热特性分析获取必要的参数,然后以此为基础进行合理的热误差建模,最后进行热误差检测及其补偿。以此为脉络展开,分别探讨了三部分内容国内外的研究现状以及存在的优缺点,并对未来的研究趋势进行了展望。     

数控机床空心丝杠进给轴热误差补偿研究

文章以提高进给轴的精度为研究对象,目的是减小滚珠丝杠系统的热误差对加工精度的影响。改变传统的实心丝杠而设计成空心丝杠进给轴是减少滚珠丝杠内热量,降低成本的有效方法。然而,压力油在丝杠内循环流动只能够带走部分热量,文章在考虑进给轴结构优化的同时也分析了残余热量的热膨胀和热传导的效应,通过误差补偿的方式减小丝杠受热所带来的影响。实验证明这种补偿的方法是有效的。     

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。     

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.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of     

Information for Contributors

The Transactions of Nonferrous Metals Society of China, founded in 1991 and sponsored by The Nonferrous Metals Society of China, is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology, including mineral processing, extraction metallurgy, metallic materials and heat treatments, metal working, physical metallurgy, powder metallurgy, with the emphasis on fundamental science. It is the unique preeminent publication in English for scientists, engineers, under/post-graduates on the field of nonferrous metals industry. This journal is covered by many famous abstract/index systems and databases such as SCI Expanded, Ei Compendex Plus, 1NSPEC, CA, METADEX, AJ and JICST.     

INTRODUCTION TO PATENTS

The invention provides a method of making a mold which can reduce SOx generation rate while preventing decrease in hardening rate in the case of using sulfuric acid for a hardener composition. The method has a mixture step in which fire-resistant particles, a hardener composition and a binder composition are mixed to obtain a composition for a mold. The hardener composition contains sulfuric acid. In the mixture step, sodium carbonate is added. A molar ratio of the sulfuric acid to the sodium carbonate is 0.5 or more and 4.0 or less.     

China Foundry Week 2014

China Foundry Week, hosted by the Foundry Institution of Chinese Mechanical Engineering Society （FICMES） each year, is a large academic event in China. It is one of the ten high-impact activities sponsored by the Chinese Mechanical Engineering Society.     

17th Conference of Hydrodynamic and Electromechanical Control Engineering Call for papers

正1.Contents In order to promote the academic exchanges and technical communication of the research in the field of fluid power transmission and control,fluid control engineering specialized committee of the Chinese Society of Theoretical and Applied Mechanics will hold the 17th Conference of Hydrodynamic and Electromechanical Control Engineering on July 27-29,2014 in Tibet,Lhasa city.     

Formulas of Tension of Continuous Rolling Process

The development of computer controlled continuous rolling process calls for a mathematical expression that can express the inequality condition of "constant flow". Tension is the link of the continuous rolling process. From the condition of dynamic equilibrium, a differential equation of tension is given out. On the basis of the physical rules established from the industrial practice and experimental studies, the law of volume constancy, the linear relation of forward slip and tension, the state equation of continuous rolling, the formula of dynamic tension, and the formula of static tension have been obtained. These formulae reflect the functional relations between tensions, thickness, roll velocity, and time in the continuous rolling process. It is implied that the continuous rolling process is a gradually steady, controllable, and measurable dynamic system. An assumption of predicting the thickness of a steel plate using these tension formulae is also put forward.