圆锥槽凸轮的廓面设计

以柱面坐标形式 ,建立了圆锥滚子直动从动件圆锥槽凸轮的廓面方程和压力角公式。为此种凸轮的三维坐标设计和数控加工提供了理论基础。当取滚子的锥角λ =0°时 ,所述方程和公式也完全可用于圆柱滚子直动从动件圆锥凸轮的设计。     

柔性声表面波器件的波模式分析

用反应磁控溅射法在柔性聚酰亚胺衬底上沉积了ZnO压电薄膜,并制备了基于ZnO压电薄膜的柔性声表面波(SAW)器件。制备的柔性SAW器件显示了良好的谐振性能,而且展现出两个波模式:模式0和模式1。当波长为32μm,ZnO厚度为4μm时,SAW器件的模式0和模式1的谐振频率分别为34.4MHz和158.5MHz,对应声速为1 100.8m/s和5 072m/s。模式0为已知的瑞利波,模式1为新的高频模式。沉积了不同厚度的ZnO薄膜制备柔性SAW器件,进一步分析了薄膜厚度对SAW器件和模式1的影响。分析认为该高频模式不是传统硬质衬底上SAW器件产生的Sezawa波,而是S_0兰姆波,并且是有衬底情况下的S_0兰姆波。文中还采用Comsol仿真分析了新的高频模式1的粒子振动位移,结果和S_0兰姆波粒子振动位移一致,从而验证了其为广义兰姆波的正确性。     

Theoretical analysis of the non-linear behavior of a flexible rotor supported by herringbone grooved gas journal bearings

This paper studies the behavior of a flexible rotor supported by a herringbone-grooved gas journal-bearing system. A hybrid method is employed to develop a time-dependent mathematical model of the bearing system. The finite difference method is employed with the successive over relaxation technique to solve the Reynolds equation. The system state trajectories, Poincaré maps, power spectra, and bifurcation diagrams are used to analyze the dynamic behavior of the rotor and the journal center in the horizontal and vertical directions under different operating conditions. The analysis reveals a complex dynamic behavior comprising periodic and quasi-periodic responses of the rotor and the journal center. The present numerical study illustrates the relationship between the dynamic behavior of this type of system and the rotor mass and bearing number. As such, the present results provide a deeper understanding of the non-linear dynamics of gas film rotor-bearing systems.     

大型凹球面数控加工工艺研究

以压力杆和支座两类零件的加工为例,分析了大型凹球面的数控加工方法.选择以铣代车的加工工艺方案,对不同的刀具、走刀路线进行了分析比较,得到合理的铣削加工方案,并进行了实际加工验证.结果表明:采用合理的以铣代车工艺可提高生产效率和零件加工表面的质量,降低加工成本.     

Micro-patterning on non-planar surface using flexible microstencil

A method for fabrication of flexible stencil was studied. Flexibility of the stencil allows micropatterning on a curved surface by material deposition or material removal (etching) through patterned hole of the stencil. In this study, low mechanical stability of the thin stencil membrane was improved by bonding the membrane with rim supporter which is thick and strong enough for easy handling of the stencil. Both of the membrane and rim structure were made of elastomer, PDMS using molding process from SU-8 master mold. The application test of shadow deposition and etching on underlying nonplanar surface using the fabricated flexible stencil mask showed the feasibility of the suggested technique into micro- patterning on a curved surface.     

Heat/mass transfer measurement on concave surface in rotating jet impingement

The objective of this paper is to investigate the heat/mass transfer characteristics on a concave surface for rotating impinging jets. The jet with Reynolds number of 5,000 is applied to the concave surface and the flat surface, respectively. The rotating experiments have been carried out at the rotating speed of 560RPM which is corresponding to Ro number of 0.075. The two jet orientation (front and trailing orientation) are considered. Detailed heat/mass transfer coefficients on the target plate were measured using a naphthalene sublimation method. The result indicates that the rotation leads to change in local heat/mass transfer distributions and the slight increase in the Sh level. The front orientation induces asymmetric Sh distributions, whereas the trailing orientation shows the shifted heat/mass transfer feature due to rotation-induced flow behavior. The crossflow effect on heat/mass transfer is also observed as the streamwise direction increases. Compared to flat surface, the heat/mass transfer on the concave surface is enhanced with increasing the spanwise direction due to the curvature effect, providing the higher averaged Sh value. It is proved that the difference of surface geometry affects somewhat the local and averaged heat/mass transfer regardless of rotation condition. This paper was presented at the 9^th Asian International Conference on Fluid Machinery (AICFM9), Jeju, Korea, October 16–19, 2007.     

弹性膜盘联轴器盘面曲线的设计与有限元分析

针对膜盘联轴器高转速、高扭矩的工作状态,给出在扭矩作用下,盘面断面的近似等强度曲线.根据联轴器在工作状态时的变形特点,并结合其固有频率,推导联轴器最薄处的厚度.     

Magnetorheological finishing of grooved drum surface and its performance analysis in winding process

The fine level finishing of grooved drum surfaces is an essential requirement for enhancing the performance of the winding machines in today’s textil     

柔性构件和柔性机构自由度分析

柔性机构由刚性构件、刚性铰链、柔性构件和柔性铰链4个元素组成,4个元素的不同组合可以得到11种不同类型的柔性机构.文中分析了其中5种常用的结构形式与特征.柔性构件的自由度及其变形规律在机构功能中起重要作用,它们是几何特性、材料特性和载荷特性的函数.在分析柔性构件自由度的基础上,给出了柔性机构的自由度计算公式,并用实例进行了验算.     

挠性印制电路板焊盘表面缺陷的检测

针对挠性印制电路板(FPC)上的焊盘表面缺陷,提出一种基于图像处理技术的智能检测方法。首先,根据缺陷的表现形式对焊盘缺陷进行归纳与分类,采用最大熵值法量化提取焊盘的颜色特征和面积特征;然后,通过评估灰度共生矩阵(GLCM)对纹理颜色变化特征与纹理结构特征量化的有效性,将其应用于焊盘纹理特征的量化与提取。实验分析显示,缺陷焊盘与非缺陷焊盘在某个或多个特征上存在着明显的差异。基于该特点,建立了BP神经网络,以焊盘的颜色、面积、纹理结构、纹理颜色变化特征值作为神经网络的输入,通过学习大量样本,获取最佳权值参数,最终实现对FPC焊盘表面缺陷的检测,检测准确率高达94.6%,50个焊盘的检测时间为300ms。实验结果表明:本文提出的检测方法不仅能够有效地对焊盘表面缺陷进行识别,而且能够满足在线检测对速度的要求。     

凹球面激光直写系统电控误差分析

高精度激光直写技术是光、机、电综合运用的前沿技术,广泛应用于精密仪器、设备等高新技术领域.而减小电控误差是凹球面激光直写技术的难点.介绍了凹球面自动调焦激光直写系统原理,分析了步进电机驱动的凹球面激光直写系统的电控误差,步进电机的步距误差,动态误差以及传动间隙空走误差等.同时给出了理论公式,并结合实例进行了精度对比分析;针对各个误差源,提出了提高步距角精度、避开共振频率、补偿空走误差等减小误差的方法.最后给出了激光直写纬线程序流程图.     

柔性曲面变形检测的FBG方法

为实现太阳能帆板、飞机机翼等薄板类曲面的动态检测,构建了一种基于光纤光栅（FBG）的传感阵列系统。将FBG传感器分布式地封装在形状记忆合金（SMA）薄片上,并采用增加预应力方式,扩大FBG检测拉应力的检测范围;利用空分复用（SDM）和波分复用技术（WDM）将FBG阵列布置到曲面上,传感器分布根据曲面应力状况采用植入式分布,应变较大的地方布置稠密,反之稀疏;曲面发生变形时,解调仪器解调出波长变化;计算机对采集数据进行处理,重建曲面形状并实时显示,以实现曲面的动态检测和显示。实验结果表明,此传感阵列系统的波长变化与曲率具有较好的线性关系,传感器布置合理、测量精度高,利用FBG能够实现曲面变形检测。     

新型大柔度锥面高速刀柄的性能研究

设计了具有分锥体结构的新型大柔度锥面高速刀柄.利用有限元软件对该高速刀柄的静态和高速性能进行了分析,具体研究了刀柄锥面与端面的压力分布特点以及主轴的膨胀变形规律.研究结果表明,大柔度锥面高速刀柄比常用的HSK刀柄具有更高的极限转速,在高转速下能够保证良好的定位精度和连接刚度,特别适合于高速加工.     

Plasma enclosed in a magnetic field produced by flexible surface magnets

A homogeneous steady state plasma with a usable volume of approximately 200 l and with an electron temperature of 1-2 eV and a plasma density of approximately 10(9)-10(10) cm(-3) is produced in a discharge chamber the outside of whose walls is covered with flexible magnetic strips. This magnet arrangement can be built at a fraction of the cost of a conventional system using rigid surface magnets. The magnetic multipole field leads to an increase of the plasma density by one to two orders of magnitude and it is also found to cause trapping of high energy electrons originating from the discharge region.     

Experimental force response of a grooved squeeze film damper

The effects of a circumferential feeding groove on the dynamic force response of a squeeze film damper are determined experimentally. Open end and sealed damper configurations are tested for different groove depths, Journal orbit radii, whirl frequency and fluid viscosity conditions. Significant levels of dynamic pressures are measured at the groove in dampers with groove depth-to-clearance ratios equal to 5 and 10. These pressures affect considerably the dynamic forces of the dampers tested. Large tangential (damping) forces are produced at the circumferential groove which contribute significantly to the damping characteristics of the test articles. For uncavitated lubricant conditions, radial forces of substantial magnitude are determined at the groove and at the thin film land where the squeeze film Reynolds numbers are typically less than 1.     

Research on three-dimensional surface parts in multi-gripper flexible stretch forming

Multi-gripper flexible stretch forming (MGFSF) is a novel flexible forming process of sheet metal based on the multi-point forming principle. The straight jaws in traditional transverse stretch forming (TSF) are replaced by several discrete clamping mechanisms on both sides. To help understand the forming characters of MGFSF, spherical and concave–convex parts were selected as the research objects and finite element analyses on TSF and MGFSF were implemented using an explicit nonlinear finite element code. The influence of the transition length on the forming results in MGFSF was also taken into account in the present work. The simulation results reveal that a shorter transition length in MGFSF would result in an easier conformability of the sheet metal to the desired shape as well as a smaller strain variation in the forming zone. It is also found that, compared to TSF, the sheet metal can be formed without transition zone by utilizing MGFSF, which could significantly improve the material utilization and save the manufacturing costs. Finally, experimental validations were conducted on the self-developed MGFSF apparatus and the experimental results show a good agreement with the numerical results.     

Analysis and modeling for flexible joint interfaces under micro and macro scale

The flexible joint interfaces with random topography are re-constructed by data point cloud obtained by experimental measurements and a contact model between two rough random surfaces is established. Contact analysis is conducted by FEM considering the elasto-plastic constitution of the material. An exponential relationship model between normal pressure and normal deformation of the joint interfaces is presented by least-square method, and furthermore, the normal contact stiffness expressions of unit area of the joint interfaces are deduced. In order to use micro-scale model to deal with large scale practical engineering interfaces, a cantilever structure connected by bolted joint is taken as a macro scale example, and its dynamic model is established with the pressure distribution on the interface and real contact area obtained by simulations and experiments. Modal test experiments are conducted, and the first three natural frequencies and frequency response functions are obtained to validate the model.     

新型大柔度锥面高速刀柄的设计

设计了一种新型结构高速刀柄,刀柄的结构特征为实心短锥双面定位,并在锥面上开环形沟槽形成分锥体。由分锥体组合而成的大柔度锥面允许刀柄与主轴锥孔以较大过盈量配合联接,同时刀柄分锥体高速旋转时能够产生较大的离心膨胀与主轴锥孔膨胀相匹配,提高了刀柄与主轴接口的极限转速和联接刚度。对刀柄结构进行了设计,利用有限元分析对刀柄的主要几何参数、过盈量以及极限转速进行了确定。研究结果证明,与常用的HSK刀柄相比,所设计的新型高速刀柄能够显著提高刀柄的极限转速。     

基于J2EE技术网上采购系统的研究与实现

在研究电子商务与网上采购基本理论与技术的基础上,分析、设计并实现了可在Windows Server 2003环境下运行的网上采购系统.系统实现过程中应用了EJB技术、数据库技术、JSP技术、Servlet技术、Jboss技术等.系统介绍了网上采购系统的基本理论及关键技术,以及网上采购系统分析、设计与实现过程.