冷连轧机辊系参激刚度颤振特性研究

考虑轧辊表面振纹对辊系间的刚度变化的影响以及动态轧制力对振动系统的影响,依据轧机垂直振动的产生机理,建立了冷连轧机单自由度非线性颤振动力学模型。应用多尺度法求解得到了系统发生1/2亚谐共振时的幅频特性响应方程,仿真分析得到了不同参数变化对振动系统幅值以及振动区域的影响,并运用奇异性理论讨论了系统在非自治情况下的分岔特性,得到在3种不同情形下系统的转迁集与分岔拓扑结构图,给出了系统失稳的参数区域,从而可以避免轧机剧烈振动的发生,这为抑制和减少冷连轧机系统的振动提供了技术支撑与理论参考。     

A combined approach to determine workpiece-tool-press deflections and tool loads in multistage cold-forging

Press and tool deflections have significant influence on the accuracy of products and tool service life in cold-forging processes. This paper presents a combined experimental-numerical approach to determine the deflections of the workpiece-tool-press (WTP) system and tool loads to improve product accuracy in a multistage cold-forging process. The measurements of deflections of the vertical mechanical press for the determination of the press flexibility matrix were performed in dynamic operating conditions. Numerical modelling of the vertical mechanical press and a multistage forging system was performed in order to evaluate the tool loads, the displacements and the rotations of the entire WTP system. The press flexibility matrix in combination with finite element (FE) model of the press and multistage process enable predictions of the elastic displacements and rotations of the tool and the press ram as well as determination of the evolution of the resultant force in order to design a reliable multistage cold-forging process. By redesigning the time sequences and evolution of the multistage forming operations during the press stroke, the evolution of the resultant force and the torque are optimized. This approach has been successfully applied to improve the prediction of tool loads, WTP deflections and rotations for the production of the automotive starter side plate.     

高速立式加工中心滑座的设计与拓扑优化

使用SolidWorks对滑座的4种方案进行三维建模,采用ANSYS Workbench对各滑座模型进行静刚度分析,确定较优的滑座模型,并运用ANSYS DesignXplorer对其进行优化设计,保证了滑座的静刚度要求,减少了滑座约10%的质量,提高了相关移动部件的运动性能。     

型钢冷床预弯机构的设计

针对不对称断面型钢在冷床上冷却时易产生侧弯的问题,在冷床输入辊道上增设了一个预弯机构,既避免了高温轧件上冷床时的摩擦损伤,又解决了轧件在冷床上的侧弯问题。     

车灯模具侧花纹结构的制造工艺研究

侧花纹是车灯的重要结构,属于重要的装饰与配光部件。在分析模具侧花纹制造技术背景的基础上,结合模具实际开发情况,给出了侧花纹加工的方法和策略。具体分析了直接机加工生成模具侧花纹以及利用电极生成模具侧花纹2种加工方式,并对其不同子类进行了具体细分,包括加工方法和拆分方法,并提出了相应建议和方案。     

环轧模拟中单元畸变的处理

针对环轧成形模拟所采用的动力显式算法由于沙漏而造成单元畸变的问题,研究了沙漏控制方法,分析了矩形截面环件轧制的成形过程.环轧初始阶段,环件变形量小,沙漏能很小;随变形量增大,控制沙漏所需沙漏能持续增长.采用人工阻尼法需要的沙漏能可达内能的20％,而采用人工刚度法所需沙漏能明显减小,只占内能的5％左右,能减小沙漏能对内能...     

陶瓷电主轴部件径向切削刚度改进

将陶瓷材料Si3N4应用于高速电主轴,利用APDL语言对其进行参数化设计程序开发。分析并计算了陶瓷电主轴的径向切削载荷及刚度,通过有限单元法分析了主轴部件的静力变形和应力分布。以弹簧-阻尼单元COMBIN14模拟轴承支撑,创建了以支撑跨距为变量的主轴参数化驱动模型。采用零阶算法实现了主轴部件静态性能优化,减小了径向载荷作用下的Von Mises应力,并计算出了更为合理的主轴支撑跨距。优化后陶瓷电主轴径向切削刚度提高了1229%,有效改进了主轴部件的加工精度和稳定性。     

Ultrasonic measurement of contact stiffness and pressure distribution on spindle–holder taper interfaces

The measurement of contact characteristics of the spindle–holder taper interface is critical for the evaluation of the performance of a machine tool spindle system. In this study, an ultrasonic method was proposed to measure the contact stiffness and pressure distribution on the taper interface. The taper interface was scanned by an ultrasound transducer, and the nominal contact area was directly estimated from the resulting ultrasonic reflection coefficient. The normal stiffness distribution was determined by the spring-damper model from the reflection coefficient. On this basis, the distributed and global radial stiffness of the taper interface was calculated by the presented theoretical formulas. Meanwhile, a calibration curve was established to convert the ultrasonic reflection to contact pressure. Based on the proposed ultrasonic method, the effects of angle fitting error and clamping force were studied. The results show that the contact area, contact pressure and contact stiffness increase with the clamping force. As the angle fitting error increases, the contact area decreases, while the pressure and stiffness at the big end of the taper interface become much larger than these at the small end. In the meantime, the global radial stiffness increases first and then decreases. This result suggests that a larger angle fit error within the permissible range is better for the global radial stiffness. Moreover, the measured results confirm that a taper joint with an angle fit error larger than +36" is not suitable for practical application, because the contact pressure at the small end is too small. To compare with the ultrasonic method, the geometrical shape profiles of the contact surfaces were constructed, and FE models were also established for contact pressure predictions. The comparison shows that the ultrasound results are consistent with the surface shape profiles and the numerical predictions. Besides, one of the taper interfaces was measured three times with the same clamping force, and the results indicate that the repeatability of the proposed method is good.     

准零刚度隔振器及其弹性特性设计

结合电子行业军用标准《准零刚度隔振器设计与应用技术导则》的编制工作，介绍了准零刚度隔振器的定义、分类及其设计方法，并有线性准零刚度隔振器及非线性准零刚度隔振器的设计示例。     

Design of a kinematic coupling for precision applications

To machine a complex precision product, several tools are needed. These tools are placed on a tool turret. A tool must return several times to its original position. To attain a very high repeatability between the upper part and the base of the tool turret mounted on a precision lathe, it is preferable that the parts of the tool turret are statically determined in their contacts. This is attained by using a kinematic coupling. To attain the required stiffness this coupling is provided with a preload of 1.5 · 10³ N. The machining forces are typically less than 1 Newton. A special kinematic coupling, consisting of grooves and balls, was designed, made, and tested. By providing the grooves with self-adjusting surfaces, hysteresis is reduced to less than one-tenth of a micrometer. Maximum stiffness is aimed at by using cemented carbide, a material with a high admissible stress, at the contact points. Experiments show that this kinematic coupling, under a preload of 1.5 · 10³ N, has a static stiffness of more than 1 · 10⁸ N/m in every direction and a repeatability better than one-tenth of a micrometer.