机床主轴轴承保持架动力学的研究及其发展现状

从力学模型和试验研究两个方面对国内外滚动轴承保持架动力学的研究现状和各阶段的主要成果进行了综述。国外学者认为保持架的设计参数尤其是保持架与滚动体间的工作间隙与摩擦力对滚动轴承保持架的动力稳定性有很大的影响。国内的研究水平较之国外还存在着一定的差距,必须建立自己的滚动轴承及保持架分析软件,以实现轴承保持架设计的参数化。针对滚动轴承保持架的动力学提出了今后需要研究的若干问题,并指出了滚动轴承保持架的设计和研究方向。     

数控机床主轴系统动力学特性分析方法研究

数控机床主轴系统的动力学特性直接影响着机床的加工精度、加工效率。文章在总结前人研究成果的基础上,对数控机床主轴系统动力学分析方法进行了综述研究。介绍了表征主轴系统动力学特性的参数,主要有静刚度、动刚度、极限切削宽度、固有频率及振型、阻尼特性和动响应。对现有的关于主轴系统动力学特性分析方法进行了归纳与总结,主要包括有限元法、传递矩阵法、阻抗耦合法、实验法等。指出了主轴系统结合部的动力学建模与参数辨识是研究主轴系统动力学特性的关键问题。最后,简要论述了主轴系统动力学研究的发展趋势,即未来应从主轴系统的精准建模、动力学综合优化和动态测试及分析等方面进行深入研究。     

铝酸钠溶液晶种分解过程动力学初步研究

本文在研究铝酸钠溶液晶种分解过程动力学时采用了一种新的研究方法,采用降温作业,利用分段抛物插值法求反应速度,用计算机求出过程表观活化能为 E_a=82.118KJ/mol,同时还求出了其它一些动力学参数。动力学方程反映了晶种系数、温度、时间以及精液苛性碱浓度、苛性比值等因素对分解速率的影响。     

可锻铸铁国内外发展近况

近年来国外对可锻铸铁石墨化理论、石墨化动力学、热力学开展了新的研究。关于研究孕育处理、热处理的理论与实践方面的报导也很多。对白口铁凝固过程和可锻铸铁的机械、物理性能的研究也十分重视。国外一些公司和研究工作者还对可锻铸铁与球墨铸铁在性能、成本、可靠性、加工性能等多方面进行了分析比较,提出了较全面深入的看法,为正确评价和选用这两种铸铁提供了科学依据。     

铝熔体除气

本文介绍了有关铝熔体氧化和吸氢的热动力学以及反应动力学的作用,还阐述了动态变化过程。是通过采用恰当的熔体处理作为动力学的问题加以说明的。对各种可能性及其作用进行了研究。铝中氢溶解度问题,特别是从固态过渡到液态时期的溶解变化问题,已是长期以来众所周知的了。最近,对熔体吸氢的敏     

铬酸钾对铝在磷酸溶液中的缓蚀作用

<正> 一、前言 近年来,人们对常用金属铁在酸中的腐蚀作了较多的研究,但对铝在磷酸中的腐蚀规律的研究还不多见。虽然Colegate等人也曾研究过铬酸钠对铝在磷酸溶液中的缓蚀作用,但未详细讨论动力学方程及动力学参数等重要问题。本工作采用经典的失重法,     

稀土镁球墨可锻铸铁的研究及应用

作者根据研究工作实践并结合有关资料评述了获得球墨可锻铸铁的各种方法及其生产可行性。着重指出了稀土镁球墨可锻铸铁在工艺性能和材质性能方面的优点;给出了稀土镁球墨可锻铸铁的最佳化学成分、适宜的熔炼工艺和热处理制度。讨论了该材质的机械性能和实际应用情况,本文还记述了用定量金相法研究该材质石墨化动力学的结果。     

“活度在冶金物理化学中的应用”

冶金物理化学的研究一般可分为热力学和动力学两方面,冶金熔体中活度的測定及其在化学平衡中的应用构成了前者的主要內容虼?活度的研究已成为冶金物理化学的一个活跃的領域。国外虽不乏冶金物理化学方面的书籍,但以活度为中心內容的专著也还罕見。国內在这方面迄今只有一些高等学蠳萄в枚幮吹慕滩?正式出版的教科书或参考书极少看到。因此,本书的出版是值得欢迎的。     

显式动力学有限元法分析板宽对板带轧制压力分布的影响

显式动力学有限元法是分析大型接触问题的有效方法 ,近年来在分析板料成形及碰撞冲击问题方面得到了广泛的应用。本文介绍了显式动力学有限元法的特点及在板带轧制过程分析中的研究状况 ,阐述了其基本理论 ,并采用显式动力学有限元法模拟了板带轧制过程 ,模拟计算出的变形区轧制压力分布与实验结果吻合较好。     

金属基复合材料的热力学与动力学研究进展

首先介绍了材料热力学和动力学模型,然后介绍了采用材料热力学和动力学模型在复合材料增强相与基体界面反应控制、反应自生增强相种类选择、反应自生增强相尺寸调控、复合材料体系设计以及复合制备工艺优化等方面研究和应用,最后进行了总结和展望。     

Simulation of parallel kinematic machine tools with minimal effort

New innovative machine tool concepts like parallel kinematics require the development process to be continuously supported by simulation. Otherwise it will be impossible to exploit their full potential due to the complexity of the kinematic and dynamic behavior. Nevertheless, machine tool manufacturers often refrain from employing simulation tools because of the high effort and expenses expected for the introduction of this technology. It is against this backdrop that the paper presents a method to support the development process of parallel kinematic machine tools with a minimum of effort. An analysis of the development process identifies the machine characteristics that have to be determined for each stage. A simulation method is developed based on these results and on the requirements for a seamless integration of the simulation techniques into the different stages of the process. It is implemented and tested by the example of a parallel kinematic machine tool that has already been successfully introduced in industry.     

A direct comparison of the machining performance of a variax 5 axis parallel kinetic machining centre with conventional 3 and 5 axis machine tools

The current trend within the Tool and Die manufacturing sector is to machine components directly from hardened material using high speed 5-axis machining. This has been driven by the increasing requirements for cost competitiveness and lead-time reduction. Significant research effort has been applied to the optimisation of the process with factors such as tooling and machining strategies being considerably improved. However, the underlying structures of the machine tools used have remained unchanged and still consist of a serial kinematic chain. One of the standard justifications for the development of machines designed around parallel kinematic chains is that they should exhibit inherently greater stiffness, have higher axis accelerations and be capable of generating significantly higher cutting forces than conventional serial machines. This suggests that they should be ideally suited to the direct manufacture of tools and dies from hardened material.The comparison of different machine tool types is a complex and difficult process, particularly when their structures are fundamentally different. This paper describes an approach used to compare the performance of three very different types of machines. The technique uses two parameters; surface finish and geometric accuracy to assess the relative performance of different machine tools when cutting hardened material. The method is used to compare a serial kinematic 5-axis machining centre, a serial kinematic 3-axis machining centre and a parallel kinematic 6-axis machining centre.The results of the comparison are presented in this paper and show that all the machine tools performed to an equal standard for materials with a hardness of 54HRc but for very hard materials, 62HRc, the parallel kinematic machine out performed the serial machine tools.     

Parallel Kinematic Machine Tools - Current State and Future Potentials

Parallel kinematics have recently attracted attention as machine tools because of their conceptual potentials in high motion dynamics and accuracy combined with high structural rigidity due to their closed kinematic loops. This paper, prepared with input from CIRP colleagues as well as of machine manufacturers and end-users involved in PKM, attempts to review the development of parallel kinematics for machine tools, their practical application and their performance compared to classical machine tools.     

并联机床运动学标定研究综述

在分析和总结有关并联机床运动学标定方面资料的基础上，详细地阐述了并联机床的加工误差源和运动学标定的进展情况。对并联机床的运动学标定研究提出了几点建议，并指出运动学标定是提高并联机床静态精度的有效方法。     

A systematic optimization approach for the calibration of parallel kinematics machine tools by a laser tracker

Parallel kinematics machine has attracted attention as machine tools because of the outstanding features of high dynamics and high stiffness. Although various calibration methods for parallel kinematics machine have been studied, the influence of inaccurate motion of joints is rarely considered in these studies. This paper presents a high-accuracy and high-effective approach for calibration of parallel kinematics machine. In the approach, a differential error model, an optimized model and a statistical method are combined, and the errors of parallel kinematics machine due to inaccurate motion of joints can be reduced by this approach. Specifically, the workspace is symmetrically divided into four subspaces, and a measurement method is suggested by a laser tracker to require the actual pose of the platform in these subspaces. An optimized model is proposed to solve the kinematic parameters in symmetrical subspaces, and then arithmetical mean method is proposed to calculate the final kinematic parameter. In order to achieve the global optimum quickly and precisely, the initial value of the optimal parameter is directly solved based on the differential error model. The proposed approach has been realized on the developed 5-DOF hexapod machine tool, and the experiment result proves that the presented method is very effective and accurate for the calibration of the hexapod machine tool.     

少自由度并联机床的构型设计

文章论述了并联机床各分支链的运动约束对运动平台自由度的影响,提出了主动链和约束链的概念.在此基础上讨论了如何根据并联机床的自由度要求,确定约束链机构和各主动链运动副型式的问题.并结合几种实际并联机床构型,验证了该设计模型的正确性.     

用神经网络方法探测机床运动误差通用建模方法

文章在分析了机床运动误差源的基础上,以典型误差源为对象,提出了基于人工神经网络技术的机床运动误差的通用建模方法,总结了基于神经网络方法的建模过程及建模方法;在此基础上建立了机床运动误差模型,通过对该模型的性能分析,用此通用方法建立的机床运动误差模型能达到精度要求,具有很好的通用性和预测性;同时该模型可以用于机床运动误差的智能补偿技术。     

新型并联机床的力／运动传递各向同性性能及其分布

以并联机器人机构为原型的并联机床,其力/运动传递各向同性性能是随其运动平台的位姿变化而变化的。本文应用并联机器人机构学理论,提出基于6-SPS并联三维平台机构的新型6自由度并联机床的力/运动传递各向同性性能评价指标,并给出这些指标在定位姿工作空间内的分布情况,这对该结构形式的并联机床的设计及其任务规划和控制有重要意义。     

Control concept for PKM considering the mechanical coupling between actors

In machines with parallel kinematic structures, the actors will interfere with each other depending on the mechanical setup. Thus, movements of one actor will directly cause disturbances on the other actors and position errors at the tool centre point. Within a research project it was shown by simulations and measurements on a hybrid kinematic machine that this interference limits the possible control loop settings.The first part of this paper discusses the possibility to increase the damping of a parallel kinematic structure, if the transformation of the kinematic coordinate systems is moved into the control loops. If this shift leads to an increased damping in the control loops, it can reduce the influence of the mechanical coupling. The project results yielded that the transformation in the control loops only has scaling effects and that these effects are different with regard to every specific transformation. Thus, the results are not commonly applicable for machine tools and manufacturing.The second part describes another research approach to increase the damping. The coupling of the actors causes the force of the first drive to act as a disturbance on the second drive. With the known disturbance and the use of a feed forward control the position error due to the coupling can be reduced by nearly 60%.     

基于3-PRS-PP的并联机床工作空间研究

工作空间是机床操作器的工作区域,它是衡量并联机床性能及加工能力的重要指标,是机床工作能力的直接反映.本文研究了一种基于3-PRS-PP并联机床工作空间,通过考虑其结构约束条件,采用极坐标搜索法确定了并联机构的工作空间边界点,并在此基础上绘出了工作空间边界曲面的图形,得到了机床工作空间的三维仿真模型,并分析了机床结构参数对工作空间的影响.