SL500/HZ超精密平面磨床的试验模态分析

为了改善S1500/HZ超精密平面磨床的动态性能,应用模态分析的基本理论,得出了试验模态分析的理论和方法.根据SL500/HZ超精密平面磨床的实际工作状态和试验的实际环境条件,采用脉冲锤击法对SL500/HZ超精密平面磨床进行了试验模态分析,得到了该机床结构的前8阶模态参数和模态振型,然后对所得模态参数进行了参数识别,...     

超精密平面磨床关键技术的发展

随着硬脆材料应用领域的扩大以及砂轮电解在线修整技术的发展,超精密磨削技术在近年来得到了飞速发展,其中超精密平面磨削技术的应用最为广泛。本文介绍了国内外超精密平面磨床的关键技术,包括总体结构、砂轮主轴及驱动系统、导轨及驱动系统、温度及热变形控制等。     

基于灵敏度分析与优化的精密运动平台模型修正

针对超精密运动平台部件中部分材料精确参数未知、粘结层准确模拟困难导致动力学建模精度相对较低的问题,提出一种基于参数灵敏度分析和优化的模型修正方法,获取面向精确动力学分析所需的高精度动力学模型.建立虚拟材料属性的粘结层单元代替原有的节点重合建模方法,利用参数灵敏度分析得到未知材料参数对结构模态影响的大小,以模态实验结果为目标选取灵敏度大的未知的材料参数进行优化,得到超精密运动平台部件的修正模型.实验结果证实,修正后动力学模型的模态频率及传递函数与实验结果之间的误差较修正前均明显降低,可用于后续超精密运动平台整体动力学特性的精确预测.     

超高速平面磨床动力学分析

以超高速平面磨床作为研究对象,基于HYPERMESH建立了各零部件的有限元模型,并在ANSYS中采用弹簧阻尼器单元COMBIN14建立各结合部的动力学模型;建立微进给机构整体有限元模型。采用8种材料组合方案对整机进行模态分析,并得到了前六阶模态,识别出了超高速平面磨床的刚度薄弱环节,为超高速平面磨床的结构设计以及材料选择提供了科学依据。     

微驱动进给结构设计与模态分析

介绍了用于半导体晶圆加工的超精密磨床微驱动进给结构的设计目标及设计原理,提出了微驱动进给结构模态分析的评价指标,对微驱动进给结构进行了模态分析,通过模态分析确认了微驱动进给结构的合理性。     

超精密大尺寸光学玻璃平面磨床的研制

光学玻璃广泛应用于激光技术、光电通讯、航空航天以及国防工业等领域。上海机床厂有限公司开发了超精密大尺寸光学玻璃平面磨床,对该磨床的结构及相关技术进行了介绍。     

微驱动进给结构设计与模态分析

介绍了用于半导体晶圆加工的超精密磨床微驱动进给结构的设计目标及设计原理,提出了微驱动进给结构模态分析的评价指标,对微驱动进给结构进行了模态分析,通过模态分析确认了微驱动进给结构的合理性.     

树脂混凝土在MK7132B数控卧轴矩台平面磨床上的应用

通过对MK7132B数控卧轴矩台平面磨床进行有限元模态分析,表明立柱是MK7132B数控卧轴矩台平面磨床的薄弱部件之一;在立柱内部空间增加树脂混凝土材料,并对立柱进行有限元模态分析,分析结果显示,改进后立柱的动态性能有明显的提高,所做的研究对机床设计具有指导意义。     

平面磨床床身结构分析与优化设计

平面磨床床身动静刚度直接影响机床的加工质量。通过建立某型平面磨床床身有限元分析模型并进行静态和模态分析,对床身结构进行改进,然后在此基础上进行结构优化,优化后床身质量下降15.6%,而结构的固有频率和刚度变化不大,取得明显的优化效果。     

精密龙门立卧平面磨床颤振监测分析与诊断

以某磨床厂的一台精密龙门立卧平面磨床为研究对象,针对其在加工过程中出现的颤振现象,综合采用加工过程振动监测、试验模态测试与振动阶次分析相结合的测试诊断方法,判断产生颤振的原因,确定引起磨削颤振的机床结构薄弱环节,并提出改进措施。研究结果表明,加工过程振动监测、振动阶次分析和试验模态测试相结合是一种行之有效的用于磨床颤振监测与诊断的测试分析方法。     

四辊轧机横向振动固有频率的研究

本文按非对称六自由度动力学模型研究了四辊轧机横向振动固有频率的计算方法。文中将轧辊作为变断面的弹性体,用能量法解决了轧机横向振动模型中各质量和刚度的计算问题,给出了四辊轧机横向振动固有频率的计算公式。实验表明,由本文方法得出的基阶频率的理论值与实测值极为相近。     

KEY TECHNIQUES OF MULTI-BODY MODELING OF OCCUPANT RESTRAINT SYSTEM OF VEHICLE SIDE IMPACT

Based on multi-body dynamics, the simulation models of auto-side structures and occupant's dynamic responses are set up, using the occupant injury simulation software MADYMO3D. These models include auto-body structure, impact barrier, seat and dummy. Definitions of multi-body and joints and dynamics properties of joints based on FE combination models, of model setup are introduced. Kelvin element of MADYMO is introduced to show the force action between non-adjoining rigid bodies, too. Then all examples of the methods mentioned are given. By the comparison of simulation and real test, the contract curves between simulation and real test for main structures and biology mechanics properties of dummy are obtained. The result shows the accuracy and validity of the models.     

Plane stress and plane strain assumptions in the stress analysis of laminated bodies

A critical survey is given of the assumptions made in the plane stress and plane strain analysis of laminated bodies. Corresponding numerical results are compared for the pure bending of curved laminated bars, and these are used to draw conclusions for general loading conditions.     

The effect of surface curvature on the friction coefficient

A simple idealized model is considered, which predicts an interesting effect that appears not to have been stressed before. If two bodies whose surfaces are curved are in contact and in relative motion, with factional shear between them, then the force resisting the motion is equal to the sum of two terms. The first of these is the frictional shear integrated over the contact region; this is the usual result. The second term is the one of main interest. It depends upon the relative curvature and is negative. Interpreted as a statement about macroscopic contact of surfaces, this means that if curved bodies are in contact and relative motion then the effective coefficient of friction between them is the sum of the basic friction coefficient between the materials and a negative term depending on their relative curvature. Some observable consequences of this effect are discussed. The phenomenon also has relevance to the building of microscopic models of surface contact. This is also examined in some detail.The effect is a consequence of the fact that, even for symmetrically curved surfaces, the contact region is asymmetrical owing to the frictional shear. This gives rise to an extra force in the direction of motion. The argument assumes that the contact is predominantly linear elastic in nature. Viscoelastic effects tend to reduce and finally to cancel the effect described.     

基于刚柔耦合技术的装载机工作装置动力学研究

装载机工作装置在作业过程中力学特性比较复杂,仅仅从刚性体的范畴对其仿真已不能满足工作需要,为了更真实地了解其工作过程的动力学特性,在ANSYS中将主要受力部件动臂及连杆柔性化．并在ADAMS中建立起工作装置的刚柔耦合模型,对其进行不周工况下的动力学仿真,得到油缸及其关键铰点的受力曲线。分析表明仿真结果更加贴近实际,建模以及分析方法为同类机构的研究提供了一种参考思路。     

A review of two models for tolerance analysis of an assembly: vector loop and matrix

Mechanical products are usually made by assembling many parts. The dimensional and geometrical variations of each part have to be limited by tolerances able to ensure both a standardized production and a certain level of quality, which is defined by satisfying functional requirements. The appropriate allocation of tolerances among the different parts of an assembly is the fundamental tool to ensure assemblies that work rightly at lower costs. Therefore, there is a strong need to develop a tolerance analysis to satisfy the requirements of the assembly by the tolerances imposed on the single parts. This tool has to be based on a mathematical model able to evaluate the cumulative effect of the single tolerances. Actually, there are some different models used or proposed by the literature to make the tolerance analysis of an assembly, but none of them is completely and univocally accepted. Some authors focus their attention on the solution of single problems found in these models or in their practical application in computer-aided tolerancing systems. But none of them has done an objective and complete comparison among them, analyzing the advantages and the weakness and furnishing a criterion for their choice and application. This paper briefly introduces two of the main models for tolerance analysis, the vector loop and the matrix. In this paper, these models are briefly described and then compared showing their analogies and differences.     

STUDY ON THE MATHEMATICAL MODEL FOR DRILL WANDERING MOTION

~TIONSa--Major axis Of the elliptical motionig--Phase deferenceO--Drill rotational center after initial ski(ldingN--Number of chatter Per drill revolutionco.--Angular velocity of the spindle rotationco.--FreqUency of drill wandering inchon(also angular velocity of the elliptical motion or main chatter freqUency)O,--Drill POint center, its motion relative to the drill mp is an ellipsex, y, z--Sforionary coordinate system, watch is fixed on the workpiecegb' Yb' gb--Drill body ocr)r'linat…     

Methods of Wear Reduction Based on Bioprototypes of Tribojoints

The main biological prototypes for tribomaterials include the surface layers of teeth, and hip and knee joints. Although the methods of functioning are not similar for artificial materials and biotissues, the localisation principle seems to be universal for them. In contrast to traditional composites with stable interfaces between matrix and reinforcing components ensuring constant technologically specified properties, dynamically optimal biotissues and adaptive (quasi‐biological) composites have mobile interfaces. For example, contacting bodies made of multimodular material with moving phase boundaries demonstrate ‘smart’ remodelling of the structure that decreases peak pressures and friction stresses. Cartilage surface microrelief influences the formation of the liquid‐crystalline phase with the molecules oriented in the preferential direction of the cartilage's relative motion, which minimises shear resistance. As a result, these structures have high wear resistance and low friction without seizure. The data obtained have led to a conclusion that the operation of the localisation principle in technical tribojoints brings about an effective control of the wear rate.     

A comparison of tolerance analysis models for assembly

Mechanical products are usually made by assembling many parts. The dimensional and geometrical variations of each part have to be limited by tolerances so that it can ensure both a standardized production and a certain level of quality defined to satisfy functional requirements. The appropriate allocation of tolerances among the different parts is the fundamental tool to ensure that assemblies work correctly at lower costs. Therefore, to ensure their functionality, assembly designers have to apply tolerance analysis. A model based on either worst case or statistical type analysis may be used. Actually, there are some different models used or proposed by the literature to make the tolerance analysis of an assembly constituted by rigid parts, but none of them is completely and univocally accepted. None of them has done an objective and complete comparison for analyzing the advantages and the weaknesses and furnishing a criterion for the choice and application. This paper briefly introduces three of the main models for tolerance analysis, the Jacobian, the vector loop, and the torsor. These models are briefly described and then compared to show their analogies and differences. Some guidelines are provided as well, with the purpose of developing a novel approach which is aimed at overcoming some of the limitations of these models.     

A computational study on the flow characteristics of a self-compensating liquid balancer

An automatic washing machine undergoes rotational unbalance due to unbalanced mass during the spinning process. A liquid balancer is an assembly that plays a role in controlling this unbalance. In recent years, washing machines (drum and automatic types) are becoming larger to handle large laundry items such as comforters. A large-sized washing machine generates a huge centrifugal force in its high speed rotating drum. Thus, a specific vibration reduction technique is required. The design of a liquid balancer has, to date, depended on conventional methods such as experiments and dynamic models. A dynamic model classifies the behavior of liquid inside the balancer into three different patterns, and solutions can be obtained by approximating these patterns as rigid bodies. This method, however, is limited to two-dimensional (2-D) analysis for simple geometry. In the present study, a three dimensional (3-D) computational fluid dynamics (CFD) method is used to analyze flow characteristics inside the liquid balancer for various design parameters. The main parameters include rotational speed, eccentricities of the center of rotation, viscosity of the liquid, gravity orientation, surface tension, and the number of baffles. In particular, the effects of these parameters on the hydraulic force (restoration force) of the liquid balancer are studied.