簧片式弹性阻尼支承(大型汽轮发电机组用)的固有频率分析和计算

一、问题的提出弹性阻尼支承(或挤压膜轴承)在航空发动机上用得很广泛,对于大型汽轮发电机的转子,也有应用先例。由于发电机转子重量较大,弹性阻尼支承必须承受相当大的静载荷,所以文献中提出了一种簧片式弹性阻尼支承,并提供了计算该支承刚度的公式,我们对一台125MW 双水内冷汽轮发电机转子的外伸集电环部份设计了一个簧片式弹性阻尼支承,并且进行了静刚度的测定,发现文献所推荐的公式与实测结果相差较大。     

二维表面粗糙度的分形模拟与分析

利用Ｗ－Ｍ函数对二维表面粗糙度进行模拟，并利用其功率谱计算表面粗糙度的分形维数。最后分析了分形维数与表面的支承长度率曲线的关系。     

一种新型两维水平传感器

探讨了以十字簧片为敏感元件的二维水平传感器的基本原理，并作了理论分析，讨论了有关各种多数的选取。在此基础上制作了传感器，并对其性能进行了测试。结果表明，该传感器测局误差可达1弧秒左右。     

大口径光学二维角度调整机构的支承优化设计

设计了"三顶三拉"的大口径光学二维角度调整机构,并探讨支承分布方式对基于三点支承调平机构的调整性能、抗倾覆能力和抗变形能力的影响,为机构设计提供了理论依据。分别建立了调平机构的几何模型、力学模型和优化模型。推导了支承调整量对平板二维倾角的贡献值,通过比较证明支承呈对称分布的调平机构更易达到快速调平的目的。介绍一种抗倾覆几何测度的概念,从中给出支承呈任意三角形分布的调平机构抗倾覆几何测度公式,并给出了对称分布调平机构的抗倾覆几何测度解析解。通过ANSYS优化模块对前内环的支承位置进行优化,得到最优的支承跨距。     

三维异形件CAD系统

以簧片为例,介绍了三维异形件的设计与显示,采用VC.net和面向对象编程方法,使用openGL三维图形库设计三维CAD系统,实现三维模型构建、模型真实和实时渲染。采用曲面拟合确定加工曲面,系统可以显示簧片数据的三维效果,并且可以修改簧片加工曲面的控制曲线。由于系统的设计对象是具有复杂加工曲面的簧片,因此对于类似复杂曲面的CAD有借鉴意义。     

主动控制空气支承动态特性的研究与优化

基于现代控制理论,提出了一种新型的主动型空气支承,不改变供气压力,利用压电陶瓷（PZT）的伸缩量来补偿空气膜厚度随外部干扰的变化对支承精度的影响。在建立理论模型的基础上,介绍了二维自由度控制器的优化设计方法,使系统具有精度高、响应速度快和抗干扰能力强的特点,并对主动空气支承系统的动态特性进行了分析研究,为主动空气支承的应用提供了理论依据。     

汽车行业几种机加工件支承率的含义及其测量

支承长度率是反映零件表面微观状态的一种二维参数，随着检测技术的发展，越来越多的在汽车中起着关键作用的机加工零件的表面质量都是通过支承率来表征。本文作者通过自己对全新支承率概念的通俗理解，详细阐述了支承率的含义及几种不同的标注方法的意义，通过具体的检测实例解释了不同标注的测量方法。     

回转压缩机簧片阀流动特性的研究

簧片阀运动对回转压缩机有很大影响,压缩机性能和簧片阀的流动特性随它的运动而定。因此,为了分析簧片阀的流动特性,我门采用了模型阀装置,模拟簧片阀的动作。用这个装置研究通过阀的压力差、阀位移、阀倾角对簧片阀流动特性的影响。这个试验系以空气作为工作流体。 试验的评价系借助于流量系数、有效通道面积和升力系数分析的。以这些结果获得了簧片阀流动特性数据,供回转压缩机分析。     

推力轴承支承方式及间隙影响研究

研究了推力轴承支承方式及油膜间隙对推力轴承性能的影响,利用Newton-Raphson法编制差分计算程序,求得了推力轴承Reynolds方程和二维能量方程的数值解,得到了不同支撑方式下瓦块的油膜厚度、压力分布和温度分布。计算结果表明,点支承扇形瓦推力轴承的热力学性能要好于线支承扇形瓦推力轴承,同时支承处的油膜厚度对瓦块的承载能力影响很大。可以通过控制每个瓦块支承处的油膜厚度,避免推力轴承内部偏载的发生,降低推力瓦块的最大温升。     

土工二维振动离心机主机结构的设计

土工二维振动离心机是目前最先进的地震模拟试验设备,但其研制技术在国内鲜有报道。通过对二维振动离心机试验工况分析,确定了三层总体布局方案和垂臂/顺臂振动方向。针对二维振动离心机给定技术指标,提出了双吊篮对称臂结构和带工字梁的焊接框架转臂支架,并通过隔振专利技术设计了顺臂隔振和不平衡力检测系统。为保证隔振系统稳定运行和增强主机抗振能力,设计了动平衡调节系统,改进了支承系统与地基的联接方式。最后对主机系统进行了力学分析,其结果表明所设方案满足试验工况和技术指标要求。     

串联弹簧质量系统冲击动态应变分析

采用螺旋弹簧一维等效弹性柱杆的波动模型,研究了一类串联弹簧质量系统的冲击动态应变。分析结果表明,考虑弹簧冲击压缩效应与否,对弹簧固定端动态应变历程有很大影响。此外,中间联接质量的大小对串联弹簧固定端的动态应变幅值及应变循环次数也有较大影响,从而影响其疲劳寿命。     

套装式双片簧三维模拟测头的研制

本文介绍了三维模拟测头的套装式双片簧结构，结构尺寸设计及影响精度的因素，并对测头的精度进行了分析，还介绍了它的测量电路。该测头采用套装式双片簧结构较三层楼式双片簧结构精度高、结构紧凑、体积小巧。它可用于三坐标测量机上作发讯测头，又可作三维测微测头     

Validation of the soft tissue restraints in a force-controlled knee simulator

In vitro testing of total knee replacements (TKRs) is important both at the design stage and after the production of the final components. It can predict long-term in vivo wear of TKRs. The two philosophies for knee testing are to drive the motion by displacement or to drive the motion by force. Both methods have advantages and disadvantages. For force control an accurate simulation of soft tissue restraints is required. This study was devised to assess the accuracy of the soft tissue restraints of the force-controlled Stanmore knee simulator in simulating the restraining forces of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL). In order to do this, human cadaver knee joints were subjected to the ISO Standard Walking Cycle. The resulting kinematics were monitored when the soft tissue structures were intact, when the ACL and PCL were resected, and when they were simulated by springs positioned anteriorly and posteriorly. The stiffness of the springs was determined from the literature. Two different stiffnesses of springs were used which were 7.24 N/mm (designated as soft springs) and 33.8 N/mm (designated as hard springs). All the intact knees showed displacements that were within the range of the machine. Cutting the ACL and PCL resulted in anterior and posterior motion and internal external rotation that were significantly greater than the intact knee. Results showed that when the ACL and PCL were cut hard springs positioned anterior and posterior to the knee returned the knee to near normal anterior-posterior (AP) motion. Using hard springs in the posterior position in any condition reduced rotational displacements. Therefore using springs in a force-controlled simulator is a compromise. More accuracy may be obtained using springs that are of intermediate stiffness.     

线性压缩机盘簧及组件性能分析

现有压缩机用板弹簧刚度小、使用数量多,因此设计了一种盘簧.采用有限元法(FEM)对比了盘簧和柔性板弹簧的刚度,并从8种不同臂形的盘簧中确定了3种性能较优的臂形;分析了弹簧组的9种布置方式,发现将盘簧放置在两等厚柔性板弹簧之间时支撑性能较好;采用响应面目标优化法对弹簧组间距进行优化,优化后的径向刚度增大了37.5％;对优...     

Comparative Study on the Complex Eigenvalue Prediction of Brake Squeal by Two Infinite Element Modeling Approaches

The complex eigenvalue analysis is currently a common approach to predict squealing vibration and noise. There are two methods for modeling friction contact in the complex eigenvalue analysis of friction systems. In one method, contact springs are used to simulate friction contact. In another method, no contact spring is used. However, it has been uncertain whether these two modeling methods can predict approximately identical results. In order to clarify the uncertainty, two finite element models of the same brake system for the brake squeal prediction are established and simulated by using ABAQUS and NASTRAN software tools, respectively. In the ABAQUS model, friction coupling is applied to determine normal contact force and no contact spring is assumed. Whilst in the NASTRAN model, the contact spring is assumed by the penalty method to simulate contact connection. Through the numerical simulations, it is recognized that even if the same mesh geometry is applied, generally, these two finite element approaches are not capable of predicting approximately identical unstable frequencies. The ABAQUS approach can predict instabilities of high frequency up to 20 kHz or more, while the NASTRAN approach can only predict some instabilities of high frequency, not all. Moreover, the simulation results also show that both the contact spring stiffness and mesh size have influences to some extent on the prediction results of squeal. The present comparative work illuminates that the modeling method without contact springs is more suitable to predict squealing vibration and noise, comparing to the modeling method with contact springs. It is proposed that one should prefer using the modeling method without contact springs to predict squealing vibration and noise. The proposed study provides the reference for predicting squealing vibration and noise.     

空间两弹簧系统的力逆解

讨论了空间两弹簧系统的力逆解问题。空间两弹簧系统是由两根弹簧并行地将空间一点（即两根弹簧的公共球铰中心）与固定平台相联而成,这两根弹簧分别通过转动副和球副与固定平台相联。其力逆解即对于给定的公共球铰中心所作用外力,求解该系统处于静力平衡时的所有构形。文中建立了该系统的力逆解方程组,并用连续法对其进行了求解。算例表明该空间两弹簧系统的力逆解最多具有１０组解。     

驾驶员座椅悬架系统刚度调节特性研究

建立了一种含两水平布置线性弹簧的驾驶员座椅悬架系统垂向力与垂向位移特性关系的理论模型。基于此模型,分析了在悬架运动行程内,弹簧刚度对悬架垂向力-位移特性、垂向等效刚度以及振动固有频率的影响,探讨了通过对弹簧刚度的调节来实现悬架垂向等效刚度调节的可行性。研究结果表明,座椅悬架的垂向力-位移特性具有明显的非线性特性;在座椅悬架整个行程内,垂向等效刚度与振动固有频率随弹簧刚度的增大而增大,且其在悬架伸张行程内的值远大于其在压缩行程内的值;两弹簧刚度对悬架垂向等效刚度的影响程度具有很大的差别。因此,通过调节对垂向等效刚度影响较显著的弹簧刚度实现悬架垂向等效刚度改变的方法是可行的。     

Exact solutions for longitudinal vibration of rods coupled by translational springs

The objective of this paper is to present exact analytical solutions for longitudinal vibration of non-uniform rods with concentrated masses coupled by translational springs. Using appropriate transformation, the governing differential equation for longitudinal vibration of a rod with varying cross section is reduced to Bessel's equation or an ordinary differential equation with constant coefficients by selecting suitable expressions, such as power functions and exponential functions, for the area variation. The exact solutions for free longitudinal vibration of rods with varying cross-section are derived. The initial parameter method and the transfer matrix method are proposed to establish the frequency equation for the longitudinal vibration of two rods coupled by translational springs. The advantage of the proposed methods is that the frequency equation for two rods coupled by translational springs can be established in terms of a determinant of 2-order for any number of translational springs and concentrated masses. The proposed methods can be used to solve the problem of free longitudinal vibration of uniform and non-uniform rods with concentrated masses coupled by various translational springs, and thus to investigate the axial stiffness and mass distribution among the rods to alter the system's dynamic characteristics. A numerical example shows that the fundamental longitudinal natural frequency of two reaction towers coupled by a pipe calculated by the proposed methods is in good agreement with the full scale measured data, suggesting the proposed methods are applicable to engineering practices.     

Static balancing of planar articulated robots

Static balancing for a manipulator’s weight is necessary in terms of energy saving and performance improvement. This paper proposes a method to design balancing devices for articulated robots in industry, based on robotic dynamics. Full design details for the balancing system using springs are presented from two aspects: One is the optimization for the position of the balancing system; the other is the design of the spring parameters. As examples, two feasible balancing devices are proposed, based on different robotic structures: The first solution consists of linkages and springs; the other consists of pulleys, cross mechanisms and (hydro-) pneumatic springs. Then the two solutions are compared. Pneumatic, hydro-pneumatic and mechanical springs are discussed and their parameters are decided according to the requirements of torque compensation. Numerical results show that with the proper design using the methodology presented in this paper, an articulated robot can be statically balanced perfectly in all configurations. This paper therefore provides a design method of the balancing system for other similar structures.     

继电器簧片气隙、超行程和压力的在线同步测量

为满足继电器大规模、高效率、日渐自动化生产的需要,试验研究了一种新的测试方法,便于在线同步测试继电器动簧片与静簧片之间的气隙、超行程和接触压力.依照继电器的结构特点,试验中通过激光位移测量仪和压力传感器在线测试衔铁的进给位移x及作用在衔铁上的压力 p,绘制得到位移-压力(即x-p)曲线.在动簧片接触静簧片之前,该段曲线斜率较小,直线上升比较平缓;当相互接触之后,由于动、静簧片弹性系数的叠加,该段曲线斜率增大,直线上升变陡;当衔铁触及铁芯后,压力急剧增大,曲线呈垂直状态.通过这些阶段变化的曲线最终可计算得到簧片间的气隙、超行程以及压力的大小,且误差小于5.0%.如果对计算公式加以修正系数,则误差将更小,由此实现了三参数的在线同步测量.而测量结果超差的产品可利用激光光源进行快速的在线校正.