Study on the Suppressing the Chatter of the Workpiece with Vari-Speed Grinding Wheel in Grinding Process

On the basis of establishing of the dynamic model of the cylindrical grinding process,this paper demonstrates the relationship between the contact stiffness of the grinding wheel and workpiece and the chatter frequency of the workpiece by matrix perturbation theory,and probes into the relationship between the radial grinding force and the contact stiffness,and between the rotational speed of the grinding wheel and the radial grinding force.It is obtained that the rotational speed of the grinding wheel and the chatter frequency of the workpiece has a corresponding relation.When the rotational speed of the grinding wheel is changed periodically,the chatter frequency of the workpiece varies periodically,so that the growth of the chatter of the workpiece is suppressed.     

砂轮变速磨削抑制工件颤振的研究

在建立外圆磨削过程动力学模型的基础上,应用矩阵摄动理论论证了砂轮与工件接触刚度与工件颤振频率之间的关系,探讨了径向磨削力与接触刚度之间、砂轮转速与径向磨削力之间的关系,得出了砂轮转速与工件颤振频率之间具有相对应的关系。     

自适应4点同心手爪机构研究设计

随着机器人产业的发展,越来越多的机械加工行业开始使用机器人进行机床上下料及加工件的搬运,而手爪是机器人应用最重要的组成部分。自适应4点同心手爪能够根据工件外形自动调整旋转关节上的2个接触点,保证4点同心,确保手爪抓取的位置精度,并且最大程度上保证4个接触点处受力均匀,减少手爪对工件表面质量的损坏。     

旋回流气爪流场特征的数值分析

基于在旋回流气爪腔体内增设绕流柱的设计方案,采用数值方法分析气室内旋回流的形成、发展过程,进一步明确了气爪内部的流场特征、压力分布规律及其吸附原理。数值计算结果表明:增设绕流柱后,可改善气爪内部和被吸附工件表面的压力分布趋势,增加吸附力,提高吸附稳定性;提高供气量,会导致旋回流的流速增加,强度提高,负压程度和吸附力也相应增大。     

基于Reynolds 方程的磨削流体动压特性的研究

由于旋转砂轮与工件表面之间存在楔形间隙,当磨削液进入楔形区域后,就会产生磨削流体动压力。以流体动压润滑理论的Reynolds方程为依据,推导出描述平面磨削时磨削流体动压力方程。采用VB和MATLAB混合编程开发出磨削时磨削流体动压力场的计算软件GRWHP。该仿真软件可用于计算磨削流体动压力的分布及磨削流体动压力对砂轮的法向作用力,且仿真结果与实验结果相符。仿真结果表明:最大磨削流体动压力产生于最小间隙附近,且位于磨削引入区内;最大磨削流体动压力随着砂轮转速的提高而增大,随着最小间隙的减小而增大。     

半履带气垫车气垫特性的试验与仿真研究

半履带气垫车是用于软湿路面运输的特种车辆,对其气垫系统的研究对提高此车辆的性能具有重要意义。在气垫系统设计过程中需要对风机转速、等效飞高、静压转换率等参数进行测量,为解决部分参数难以测量的问题,提出半履带气垫车气垫系统中各参数之间关系的求解方法。在自行设计的半履带气垫车原理样机上进行气垫力试验,得到气道特性曲线及气垫力和悬架弹簧的变形关系。通过相应的流体力学仿真,分析气垫系统中风机转速与等效飞高之间的关系及其对静压转换率的影响;通过进一步建立气垫系统的垂向刚度弹性模型,对等效飞高和气垫系统的垂向等效弹簧刚度等参数之间的关系进行分析。此结果为带气垫系统的车辆的设计提供了参考。     

Development and experimental evaluation of air flotation element with additional air‐intake capacity

Focusing on the flotation transmission of thin and light glass substrates, we propose a new air flotation element design. This new element takes advantage of a rotating airflow to form negative pressure, which then intakes additional air to support the floating workpiece via an intake hole connecting the negative pressure with the atmospheric environment. This design can effectively improve the flotation height and can reduce air consumption. Here, the structure and operating principles of this new element are illustrated, while the fundamental characteristics are experimentally investigated. We study the variation of negative pressure and the resulting intake flow when the flotation height varies. It is found that the new flotation element can intake additional air when the flotation height is larger than a certain critical value. Also, the additional air is conducive to raising the flotation level of the workpiece. This feature is suitable for applications involving low flotation forces, e.g. the flotation transmission of thin and light glass substrates. Additionally, the performances of the new element and the traditional orifice element are compared, indicating that, for the same flotation force and supplied airflow, the newly designed element can increase the flotation height by 25%. On the other hand, the air consumption can be reduced by approximately 50% using the new element, for the same flotation force and height. Copyright © 2015 John Wiley & Sons, Ltd.     

Scw400钉盘磨开发应用与影响参数研究

论述了Scw400钉盘磨的传动装置、粉碎装置和主动气流密封装置等典型结构及工作原理,分析了磨盘转速、进风口风量、喂料量、物料颗粒的脆性和硬度等主要操作参数对粉碎效果的影响。用Scw400钉盘磨、选粉机、袋式收尘器、风机等设备搭建了实验系统,通过调节两磨盘的相对转速对木屑进行粉碎实验。用80μm的筛网对粉碎后的木粉进行筛余测试,得到了两磨盘相对转速和出料筛余之间的对应关系。实验表明,两磨盘相对转速为5480r/min时,出料80μm筛余可达4.37%。     

磁流变变间隙动压平坦化加工力特性研究

磁流变变间隙动压平坦化加工利用工件的轴向低频振动使磁流变液产生挤压强化效应,可以有效提高加工效果并使光电晶片快速获得纳米级表面粗糙度。通过旋转式测力仪试验研究不同变间隙参数对磁流变变间隙动压平坦化加工过程中抛光正压力的影响规律,结果表明,在工件轴向低频振动作用下,抛光正压力形成脉冲正值和负值周期性的动态变化过程;将工件轴向低频振动过程分解为下压过程与拉升过程,下压速度和拉升速度对动态抛光力有不同的响应特性;随着最小加工间隙的减小抛光正压力会急剧增大;设置最小加工间隙停留时间观察抛光正压力变化,可以发现在工件最小加工间隙停留期间抛光力从峰值逐渐衰减并趋于平稳;挤压振动幅值对抛光正压力影响较小。建立了磁流变变间隙动压平坦化加工材料去除模型,弄清了在动态压力作用下,磨料更新及其附加运动机制,研究了磁流变变间隙动压平坦化加工过程中磨料颗粒对工件表面柔性划擦和微量去除的作用机理,为磁流变变间隙动压平坦化加工的工艺优化提供了理论依据。     

铣削加工中最小夹紧力的计算

提出了一种计算铣削加工中夹紧工件所需最小夹紧力的简洁方法。首先,确定了工件与夹具元件之间的接触刚度;其次,建立了接触变形量与工件位移量的关系;然后,给出了工件的静态平衡方程。通过合并以上方程,建立了线性方程组计算工件与夹具元件之间的切向接触力,并根据最大切向接触力进一步计算出夹具元件与工件之间不发生相对滑动所需理论最小夹紧力。最后,通过算例验证了该方法的正确性。     

Online Condition Monitoring of Gripper Cylinder in TBM Based on EMD Method

The gripper cylinder that provides braced force for Tunnel Boring Machine (TBM) might fail due to severe vibration when the TBM excavates in the tunnel. Early fault diagnosis of the gripper cylinder is important for the safety and efficiency of the whole tunneling project. In this paper, an online condition monitoring system based on the Empirical Mode Decomposition (EMD) method is established for fault diagnosis of the gripper cylinder while TBM is working. Firstly, the lumped mass parameter model of the gripper cylinder is established considering the influence of the variable stiffness at the rock interface, the equivalent stiffness of the oil, the seals, and the copper guide sleeve. The dynamic performance of the gripper cylinder is investigated to provide basis for its health condition evaluation. Then, the EMD method is applied to identify the characteristic frequencies of the gripper cylinder for fault diagnosis and a field test is used to verify the accuracy of the EMD method for detection of the characteristic frequencies. Furthermore, the contact stiffness at the interface between the barrel and the rod is calculated with Hertz theory and the relationship between the natural frequency and the stiffness varying with the health condition of the cylinder is simulated based on the dynamic model. The simulation shows that the characteristic frequencies decrease with the increasing clearance between the barrel and the rod, thus the defects could be indicated by monitoring the natural frequency. Finally, a health condition management system of the gripper cylinder based on the vibration signal and the EMD method is established, which could ensure the safety of TBM.     

Design of a gripper system for tendon-driven telemanipulators considering semi-automatic spring mechanism and eye-in-hand camera system

Tendon-driven mechanisms are adopted in remote handling manipulators to reduce the weight of the distal parts of the manipulator while maintaining the handling performance. This study considered several approaches to the design of a gripper system for telemanipulators. According to the requirements of the specified tendon-driven mechanism, the connecting position of the spring system on the gripper mechanism was obtained, and kinematic influence coefficient analysis was performed to select the proper spring stiffness. The results showed that the tension force generated by the selected spring module is relatively constant in the gripper’s motion range; the spring module is advantageous for the semi-automatic gripper motion of servo-based tendon-driven manipulators performed in non-accessible experimental facilities which handles many types of sensitive measuring devices with hazardous materials. The motion performance of the proposed gripper module was comparatively verified with a commercialized gripper system which has similar specifications. Additionally, an eye-in-hand camera was also designed to obtain an active-view through a gripper for efficient teleoperation. This gripper system uses a modular-type camera head that can be changed remotely and a proper camera angle to achieve an intuitive view of the remote site. The designed camera system was tested in a large-scale confined cell facility remotely and verified the practical usability for remote handling manipulators.

     

高速主轴离心膨胀及对轴承动态特性的影响

以高速主轴系统为对象,将主轴转子和轴承内圈分别等效为等截面梁和空心圆盘,计算离心力作用下主轴转子和轴承内圈的径向弹性变形,并分析主轴转子与轴承连接状态随转速升高的变化趋势。考虑旋转部件的离心膨胀变形,建立高速主轴轴承动力学模型并进行试验验证。在此基础上,研究离心效应对主轴轴承径向预紧状态的影响,揭示高速主轴轴承动态特性随转速的变化规律。研究结果表明,离心力引起的径向膨胀变形使滚动体与轴承内、外圈之间的接触角减小,接触力增加。主轴轴承的轴向刚度和径向刚度均随转速的升高而降低。轴承内圈的离心膨胀变形对轴承轴向刚度的影响可以忽略不计,而能在一定程度上提高轴承的径向刚度。     

反馈控制式高速旋转接头的研制

高速旋转接头一般采用间隙密封,而密封间隙会由于外界干扰发生变化,间隙变小可能使固定件与旋转件直接接触,导致磨损加剧,寿命降低.间隙变大会导致泄漏增加.所设计的高速旋转接头采用了静压反馈控制密封间隙,使固定件与旋转件在工作时不受外力干扰,保持密封问隙恒定,只产生粘性的液体摩擦,减小了摩擦和磨损,延长了高速旋转接头的使用寿命.     

某ADSL宽带局端插箱的热分析——风机气流旋转角速度对模拟结果的影响

通过模拟仿真和试验测量,介绍了某ADSL宽带局端插箱散热仿真中风机的气流旋转角速度对于模拟结果正确性的影响,通过实验表明：风机的气流旋转角速度对于插箱各个槽位的风量分配有很大影响,气流旋转角速越大,各个槽位的风量分布越不均匀,最差槽位的风量越小.忽略风机气流旋转角速度可能造成元器件的温度模拟的重大偏差,在模拟中必须注意.     

An optimal design algorithm for centrifugal fans: Theoretical and experimental studies

This study examines the inverse design problem (IDP) of determining the optimal three-dimensional shape of a centrifugal-flow fan based on a desired airflow rate. The desired volume airflow rate can be obtained by multiplying the airflow rate of an existing fan by a constant greater than unity. The geometry of the redesigned fan is generated using several design variables, which enables the shape of the fan to be constructed completely; thus, the parameter estimation technique used in inverse design problems can be used. Finally, prototypes of the original and optimized centrifugal fans are fabricated, and the fan performance is tested based on the AMCA-210-85 standard, which uses calibrated nozzles and pressure taps within a standardized test chamber, to verify the validity of this work. The experimental results demonstrate that by using the fabricated optimal fan, the airflow rate can be increased by 11.8 % and the fan noise can be reduced by 3.5 %; as a result, the performance of optimal fan is greatly improved.     

Dynamics of a rotating Rayleigh beam subject to a repetitively travelling force

The dynamics of a rotating Rayleigh beam subject to a force travelling at a constant speed along the axial direction is studied. The beam is chosen as a simple model of the workpiece in the lathing process. A technique is developed for modeling the repetitive cutting force on the workpiece. The amplitude of the cutting force is chosen to be either constant or dependent on the motion of the beam. The discretized equations of motion of the rotating beam are obtained by Galerkin’s method. The time response of the rotating beam subject to the external force is discussed. The possible resonant conditions resulting in divergent solutions are studied. The stability of the response, due to a travelling motion-dependent force, is determined by the method of multiple scales. The effects of varying the rotating frequency, the travelling speed of the external force, and the movement of the force are also investigated.     

DISCUSSING ON SOLID ABRASIVE LAPPING PATH

ＤＩＳＣＵＳＳＩＮＧＯＮＳＯＬＩＤＡＢＲＡＳＩＶＥＬＡＰＰＩＮＧＰＡＴＨＹａｎｇＪｉａｎｄｏｎｇ，ＷｅｎＸｕｅｈｅｎｇＣｈａｎｇｃｈｕｎＩｎｓｔｉｔｕｔｅｏｆＯｐｔｉｃｓａｎｄＦｉｎｅＭｅｃｈａｎｉｃｓＺｈｕＹａｎｑｉｕ，ＷａｎｇＬｉｊｉａｎｇＪｉｌ...     

超声振动承载气膜对电机转子悬浮支承与减摩的研究

设计一种用于支承电机转子的超声波悬浮轴承,该轴承由圆锥形压电换能器辐射端面与连接在电机转子端的圆锥环构成。压电换能器在振动过程中在轴承间隙形成稳定的承载气膜,对电机转子悬浮。对承载气膜产生的承载能力进行分析和测试,获得悬浮力与悬浮间隙之间的关系,从理论上分析在超声悬浮支承条件下,悬浮间隙变化与气膜刚度对电机转速的影响,对转子最高转速与悬浮间隙的关系进行实验研究。结果表明,利用压电换能器圆锥辐射面与圆锥环构造的超声波悬浮轴承,能够形成对电机转子的轴向和径向支承;通过减小悬浮间隙,能够增强间隙气膜的刚度,并提高转子的最高转速,轴承间无摩擦。     

An optimal design for axial-flow fan blade: theoretical and experimental studies

The technique of inverse design problem (IDP) for optimizing the three-dimensional shape of an axial-flow fan blade based on the desired airflow rate is presented in this work. The desired volume flow rate of air can be obtained from the airflow rate of the existing axialflow fan by multiplying it with a constant which is greater than unity. The geometry of the redesigned fan blade is generated using numerous design variables, which enables the shape of the fan blade to be constructed completely; thus the technique of parameter estimation for the inverse design problem can be used in this study. Results show that with the redesigned optimal fan blade, the airflow rate of fan can be increased, thereby improving the performance of the axial-flow fan. Finally, to verify the validity of this work, the prototypes of the original and optimal axial-flow fan blades are fabricated and fan performance tests are conducted with these blades on the basis of the AMCA-210-99 standard. The algorithm used in the present study can be applied to the blade design problem in any propulsion and power systems.