球轴承的摩擦系数分析

运用接触力学与平衡原理，研究了球轴承的摩擦系数。分析了钢球直径、沟曲率半径系数、接触角与载荷对摩擦系数变化的影响。结果表明，摩擦系数随钢球直径的增加而减小；由于沟曲率半径系数变化范围很小，其对摩擦系数影响不显著；摩擦系数随接触角的增大而增加；随径向载荷的增大，摩擦系数增加。     

带滚珠丝杠齿轮自动脱螺纹机构的压铸模

铸件螺纹脱模是压铸模设计的难点之一.自动旋转脱螺纹一般采用齿轮-齿条机构或液压-齿轮机构.本压铸模则采用一种新机构--滚珠丝杠-齿轮脱螺纹机构.该机构利用压铸机推杆为螺纹型环旋转脱模提供动力,通过滚珠丝杠-齿轮机构将压铸机推杆的直线运动,转变为螺纹型环旋转运动,实现螺纹铸件自动脱模.     

Quality improvement of ball-end milled sculptured surfaces by ball burnishing

In this paper, the use of the ball burnishing process to improve the final quality of form tools (moulds and dies) is studied. This process changes the roughness of the previously ball-end milled surfaces, achieving the finishing requirements for plastic injection moulds and stamping dies. Ball burnishing can be easily applied in the same machining centres as those used for milling. In this way, both lead times and production costs can be dramatically reduced.

Both the burnishing system and its main parameters are taken into account, considering their influence on finishing. Workpiece surface integrity is ensured due to the surface smoothing effect of process and the associated cold working. Examples of different materials, machined surfaces, and industrial applications are explained, with respect to the maximum and mean surface roughness achieved.

The main conclusion is that using a large radial depth of cut in the previous ball-end milling operation, together with a small radial depth during burnishing can produce acceptable final roughness. Savings of production times are high, as burnishing is applied using the maximum linear feed of the machine, while milling must be made at moderate feeds. Moreover, ball burnishing NC programming is less critical and needs less care in its definition than CAM for milling.     

高硼铸钢的制备与应用

针对常用磨球材质脆性大、耐磨性低、磨耗高,以硼为主要合金元素,研制了高硼铸钢磨球。为了净化钢液,研究了高硼钢液吹氩净化工艺,选择氩气流量1 5~2 5 L/min,氩气压力1 0~1 5 MPa,吹氩时间5~8 min,吹氩后钢液的静置时间5~8 min的吹氩净化处理工艺,钢液净化效果好。高硼铸钢磨球经9 5 0~1 0 5 0℃加热后快速淬火和1 8 0~2 5 0℃回火处理后,具有硬度高、硬度均匀性好和韧性高等特点,用于研磨矿粉和煤粉,磨耗与高铬铸铁球相当,成本降低3 0%以上,综合效益显著。     

雷达天线座静压轴承的可视化设计

本文通过对雷达天线座液体静压轴承的受力分析与结构设计，利用可视化编程工具Visual Basic6.0编制了一套快捷，实用的垫式静压轴承及节流器的设计软件，应用表明，该软件有助于提高设计效率和质量。     

大型球磨机衬板材料的研究和应用

研究成功了一种适合于制造大型球磨机衬板的新材料.在不含钼、镍等贵重合金元素前提下,设计的中碳钢以硅、锰、铬为主要合金元素,并加入少量钛、钙、硼、钇、钾、钠等元素,改善钢的组织和淬透性.新材料具有足够的淬透性和淬硬性,经油冷淬火和中温回火处理后,硬度大于55 HRC,冲击韧性大于25 J/cm2,断裂韧性大于40 MPa·m1/2.用于制造大型球磨机衬板,耐磨性比高锰钢衬板提高1倍以上,生产成本降低15%,具有很好的经济效益.     

控制力矩陀螺高速转子轴承保持架仿真分析

建立了控制力矩陀螺高速转子球轴承保持架动力学仿真分析模型,并以B7005C球轴承为例,分析了不同引导间隙、兜孔间隙对保持架质心轨迹、保持架摩擦力矩的影响,据此进行了保持架间隙的优化,得出了适用于该工况的最优保持架间隙。     

基于功率谱包络能量和SVM的舰用发动机故障诊断

发动机是军舰上的重要部件之一,其稳定性对军舰的正常航行具有重要影响。以舰用发动机关键部件(主泵轴承)为具体研究对象,提出了基于功率谱包络能量和支持向量机相结合的故障诊断方法。首先获取了大量可表征舰用发动机主泵轴承健康状态的振动加速度信息,对其进行功率谱分析,获得其功率谱的包络能量;以获取的舰用发动机主泵轴承功率谱的包络能量构建特征向量,并设计基于SVM的舰用发动机主泵轴承故障诊断模型,对主泵轴承的故障进行诊断研究。研究结果表明,采用基于功率谱包络能量和SVM相结合的舰用发动机关键部件故障诊断方法,可以很好实现主泵轴承的故障诊断效能,为舰用发动机主泵轴承故障诊断的工程应用奠定了基础。     

板球系统的参数自调整反步控制

为解决系统初始值大范围变化,且控制量受到饱和特性约束的板球系统镇定控制问题,提出一种自动调整待设计参数的反步控制方法.分析了反步法偏差系统的平衡点特性;说明了反步法待设计参数与偏差系统动态间的关系;构造了Mamdani模糊逻辑,以自动调整反步法待设计参数;考虑了控制量受饱和特性限制而引入的约束条件,进而以遗传算法优化了模糊规则.仿真和实验结果均表明,自动调整待设计参数的反步控制方法降低了镇定控制中的位置偏差和位置超调.     

Multibody dynamics analysis of the driveshaft coupling of the ball and tripod types of constant velocity joints

The paper proposes a multibody dynamic simulation to numerically evaluate the generated axial force (GAF) and plunging resistant force (PRF) practically related to the shudder and idling vibration of an automobile. A numerical analysis of the drive shaft coupling of a ball joint (BJ) and two plunging type joints, a tripod joint (TJ), and a very low axial force tripod joint (VTJ), are conducted using the commercial program DAFUL. User-defined subroutines of a friction model illustrating the contacted parts of the outboard and inboard joint are subsequently developed to overcome the numerical instability and improve the solution performance. The Coulomb friction effect is applied to describe the contact models of the lubricated parts in the rolling and sliding mechanisms. The numerical results, in accordance with the joint articulation angle variation, are validated with experimentation. The offset between spider and housing is demonstrated to be the critical role in producing the third order component of the axial force that potentially causes the noise and vibration in the vehicle. The VTJ shows an excellent behavior for the shudder when compared with the TJ. In addition, a flexible nonlinear contact analysis coupled with multibody dynamics is also performed to show the dynamic strength characteristics of the rollers, housing, and spider.