机床进给爬行时的运动模型与振动方程

本文讨论了机床进给系统中因运动部件移动速度较低，因而产生爬行现象的自激振动机理。并通过对进给系统建立运动模型、导出振动方程从而对爬行现象进行了理论分析。     

数控机床进给系统产生爬行的机理分析

数控机床在低速进给时,产生非匀速爬行,对加工精度和零件表面质量非常不利.本文应用控制理论对机床进给系统的爬行现象进行了理论分析,建立了进给系统的数学模型,用有限差分法对模型进行了求解,在此基础上,系统地研究了产生爬行的各种条件及影响爬行的主要因素,提出了解决爬行问题的几种措施,指出降低导轨摩擦系数是克服爬行的最直接有效的方法.     

重型数控卧式车床进给系统动力学分析

重型数控卧式机床进给系统在低速运行时,易产生爬行现象,严重影响机床的加工精度、表面粗糙度和定位精度。应用齿轮系统动力学理论分析进给系统的爬行机理,建立进给系统动力学模型,利用Newmark数值方法求解该动力学模型,并采用LMS Virtual.Lab Motion软件模拟进给系统拖板箱的进给位移,为爬行问题的解决奠定基础。     

基于西门子802D数控系统的机床进给爬行的模型分析及改进措施

数控机床爬行问题是提高机床加工精度的重要研究课题之一,本文基于产生数控机床爬行现象的原理对机床产生爬行原因进行了理论分析,并建立了爬行的数学模型。在对爬行原因进行合理分析的同时提出了解决数控机床爬行现象的有效措施,并以市场上较为流行的西门子802D数控系统为例,阐述了如何通过相关的机床参数改善进给爬行现象。该项研究对数控机床的设计、制造和维修具有重要意义。     

气缸运动建模及爬行现象判别

由于爬行现象的影响，气缸在低速驱动时不能保持平滑的运动状态，降低了气动系统的控制精度。本文对气动系统进行理论分析，建立系统的动力学方程，引入无量纲参数，并对爬行现象判别式进行理论推导。     

高精度工作台速度反向时摩擦补偿研究

在消除了丝杠导程、间隙等误差之后,进给系统中存在的摩擦是影响工作台运动控制精度的主要因素。由于摩擦的影响,导致工作台速度反向时产生爬行现象,从而使得误差突然增大。文章对摩擦误差产生机理和补偿方法进行了研究,从瞬态响应的视角揭示了摩擦误差产生的机理,通过数学推导精确计算出爬行现象的持续时间,以及由此导致的最大跟随误差。提出了一种零速对称式摩擦补偿方法,该方法在工作台的爬行时间内进行补偿,使工作台尽快脱离爬行状态,仿真结果表明该方法能够显著的减小爬行时间。     

数控磨料水射流切割机伺服进给系统的振动爬行现象分析

提出数控磨料水射流切割机伺服进给系统存在振动爬行现象,并对其危害、影响因素、爬行机理进行分析,通过建立物理模型和分析临界速度找到解决爬行的措施和对策,对提高系统稳定性具有实际意义.     

基于爬行理论的滚珠丝杆进给系统加工波纹度成因的研究

文章根据爬行理论对滚珠丝杠进给系统进行了分析,讨论了滚珠丝杠摩擦力矩的波动以及滚动导轨的摩擦阻力波动现象,认为滚珠进出滚道是引起滚珠丝杠及滚动导轨摩擦力(矩)波动的主要原因,丝杠系统的轴向作用力使得丝杠摩擦力矩的波动加剧,由于轴向作用力下丝杠接触刚度的下降将引起整体刚度的不足,在波动摩擦力(矩)的作用下丝杠进给系统将产生不平稳运动,而造成加工系统表面波纹度的产生。     

数控机床进给运动对加工精度的影响

数控机床进给运动的精度对零件的加工精度有极大的影响。本文通过分析数控机床机械传动部件的特性，得出数控机床进给系统低速爬行的原因，并提出提高数控机床低速进给运动的平稳性和运动精度的措施。     

电源故障引发的加工中心失控现象

在各种数控机床和加工中心的电气控制系统中,都设有断相、相序错误的故障检测及报警功能.当发生电源引线接触不良,或其它原因引起一相电源电压下降很多时,因此会使机床产生一些错误动作,使系统对机床的动作失去控制.表现在驱动部分主要是轴的移动不按位置及速度指令执行,出现突然快速进给、冲击、爬行等现象,当速度较快时常与机械部分发生相撞而导致驱动控制器上过流检测报警,空气开关跳闸或其它保护装置动作而停机.     

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.     

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.     

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.     

Rheology Feature of Simple Metal Melt

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.