柔性机械臂关节刚度的一种间接测量方法

给出一种分析柔性机械臂关节刚度的间接测量方法。该方法在机械臂末端执行件上的不同位置加载，测量载荷与载荷方向上的位移数据，然后使用有限元方法计算不含关节时结构对应点的载荷、位移关系，从测量结果中排除不含关节时的位移。利用这些仅包含关节信息的载荷和位移数据通过求解一个线性方程组，可以得到各个关节的刚度数据。最后通过一个实际的例子，说明了该方法的有效性。     

Q235钢等离子熔覆的残余应力及变形数值模拟

基于ABAQUS软件有限元模拟和Goldak热源模型,考虑材料非线性特点,采用热力耦合的方法对等离子熔覆Q235钢的温度场、应力场和位移场进行模拟,并采用盲孔法测量了其实际残余应力。结果表明,采用Goldak模型可以较好地仿真等离子热源,热循环模拟结果稳定,且与实际熔覆结果符合;在X和Z向上,残余应力的计算值与测量值变化趋势一致,沿X向测量点纵向残余应力试验值与模拟最大差值为43MPa,平均差值为6.2MPa。沿Z向存在一些偏差,但总体趋势趋于一致,纵向残余应力模拟平均值为-189.54MPa,试验平均值为-211.5MPa;熔覆完成后最大变形量为0.05mm,出现在熔覆层中心位置,Q235钢基体变形量0.01mm。     

加工中心静刚度特性分析及实验研究

应用理论分析方法对影响加工中心静刚度的因素包括丝杠结构静刚度、进给伺服系统刚度、主轴-刀具系统静刚度、滚动导轨刚度等进行了分析.以立式加工中心VICTOR为例,分别采用数控进给加力方式和螺旋加力结构方式进行加力,实测了加工中心主轴端面与工作台间Z向和X向的静刚度值,测量结果显示加工中心的静刚度并不明显高于普通机床.为加工中心结构及系统的设计、工艺参数的选取等提供借鉴.     

高性能直驱混联数控机床静刚度分析

基于模块化设计技术,开发了一种由直线电机驱动的高性能混联数控机床,主要由2-DOF并联主轴头和XY工作台两大功能模块组成。以该机床并联主轴模块为研究对象,基于边界元和刚度矩阵组集方法,建立了机床静刚度模型,并编制了刚度计算软件,由此计算得到机床主轴在整个工作空间内位置刚度和旋转刚度的分布。数值仿真表明:该机床具有较好的刚度特性,满足轻切削加工静刚度设计要求。     

3-TPT型并联机床静力学及刚度研究

以一种3-TPT并联机床为研究对象,研究该机床在承受静态外力负载时静力学问题及运动平台的刚度问题.首先利用虚功原理建立了并联机床的静力学正解方程,然后推导出该并联机床的柔度矩阵,在此基础上利用Matlab软件对该机床的静力学及刚度进行了研究,仿真出了该三杆并联机床的运动平台静力学特性及其刚度的变化曲线.研究结果表明:驱动杆所承受的最大载荷不超过运动平台负载的2.5倍,且随着运动平台远离Z轴,其Z方向刚度变化较其他方向尤为明显.这一分析为并联机床的结构优化设计和动力学研究提供了理论基础.     

基于ADAMS的3-TPS混联机床动态特性分析

利用ADAMS软件对3-TPS型混联机床进行振动测试分析和加工仿真分析,建立了机床动态仿真分析的刚柔耦合模型,分析了机床在各个方向的振动特性,仿真分析了切削力下机床刀尖位置的位移偏差。结果表明,该机床Y、Z方向的振动响应较大,X向的响应较小;在铣削力作用下,刀尖点位移产生了明显的偏移,致使机床的加工精度降低。     

新型3UPS+1RPU混联机床的静刚度与动态特性分析

以一种新型3UPS+1RPU混联机床作为研究对象,对该混联机床在不同位姿下的刚度和动态特性进行研究。首先运用Solid Works对该混联机床建立三维实体模型,然后导入到有限元分析软件ANSYS Workbench进行刚度分析,找出了机床刚度的薄弱部位,通过比较得知位姿α下机床的刚度好于位姿β,并得出刚度随位姿变化的规律。然后进行模态分析,得到不同位姿下机床的1~6阶固有频率和振型,找出机床运动过程中易发生共振的位置;在模态分析的基础上,对该混联机床进行谐响应分析,得出动平台在X,Y,Z轴方向的位移响应曲线,找出该机床应该避开的敏感频率,并通过比较得知位姿α下的混联机床动态特性好于位姿β。因此得出结论:机床在加工零件的过程当中,应尽量避免达到极限位置(位姿β),从而使机床保持较高的刚度和较好的动态特性。     

利用纳米压痕加载曲线计算硬度-压入深度关系及弹性模量

通过对纳米压痕法基本原理的分析与实验研究，证明了一般材料的接触刚度-位移（压入深度）为线性关系．该关系可从两个不同压入深度的压痕实验得到，利用该关系可从任意一条加载曲线计算出材料的硬度-位移关系及弹性模量值．实验结果表明这个计算结果是可靠的．     

铜包装线液压升降平台刚度的研究

为确定铜包装线液压升降平台许用的最大负载,运用ANSYS仿真方法,研究铜自动包装生产线上料工位工作时,液压升降平台的液压缸缸筒变形,并计算其容积变化;分析上料过程活塞杆的位移变化及影响位移变化的因素,并在MATLAB中得到活塞位移变化曲线;分析影响液压升降平台垂直刚度的因素,并仿真得到刚度曲线。为实现精确控制和确定升降平台最大负载提供依据。     

机械结合面法向接触刚度三维分形理论模型北大核心

为了解决以往在结合面上法向接触刚度分形建模理论研究的计算过程中存在的一些问题,所以专门对结合面上单个微凸体的弹性、弹塑性接触变形模型中的法向载荷和刚度的计算过程进行了适当的改进,从而建立了一种考虑弹性、弹塑性和塑性3种变形机理的法向接触刚度模型。通过模型理论预测值与实际测量值的比较可知,所建立的分形模型可以较好地预测法向接触刚度,进一步说明了所建模型的可靠性和精度,也证实了改进算法的可行性。所建模型可以用于相关接触刚度的计算与分析,有助于对结合面的刚度动态特性做进一步的研究。     

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.     

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.     

A Concordant Shift Model for Flow in Bulk Metallic Glasses

The homogeneous plastic flow in bulk metallic glasses(BMGs) must be elucidated by an appropriate atomistic mechanism. It is proposed that a so-called concordant shifting model, based on rearrangements of five-atom subclusters,can describe the plastic strain behaviour of BMGs in a temperature range from room temperature to the supercooled liquid region. To confirm the effectiveness of the atomic concordant shifting model, a comparative investigation between the vacancy/atom model and the concordant shifting model is carried out based on the estimation of the strain rate deduced from two models. Our findings suggest that the atomic concordant shifting model rather than the vacancy/atom exchange model can well predict the large strain rate in the superplasticity of BMGs.