长跨距滚珠丝杠振动分析与减振提速方案

大型和高速机床中的长跨距滚珠丝杠,由于行程长、丝杠长径比过大,导致挠度大、运行中易发生抖动等一系列问题,严重影响机床的动态性能。根据丝杠结构和滚珠丝杠驱动方式的不同,分析长丝杠的振动方式,长丝杠振动对机床临界转速和传动精度的影响。通过ANSYS Workbench动力学分析模块,对丝杠进行模态和振动响应分析。针对出现的问题,提出了相应的技术解决方案。研究结果为解决长跨距丝杠工程应用问题提供了参考依据。     

高速绣花机不同工况振动特性研究

针对高速绣花机工作转速和振动共同作用时引起的绣花质量和断线率问题,从横梁和转轴出发找到了解决问题的方法。通过对某公司生产的高速ZY-EMSD-A920型绣花机的研究、采点及测试、数据处理分析、计算机模拟验证探讨了不同工况引起的振动位移变化和振动变化程度。结果表明：横梁水平方向的振动和上转轴运动引起的振动对绣花机断线率的影响最大,为今后绣花机结构改进和新机型的开发提供了新的参考依据。     

Vibration-assisted dry polishing of fused silica using a fixed-abrasive polisher

Glass is a ubiquitous but essential material in everyday life and industry. The most common method for polishing glass involves the use of free abrasives. However, this method is basically non-deterministic and lacks efficiency. Therefore, vibration has been employed to aid fixed-abrasive polishing in our research. It is found that the vibration can increase the material removal rate while maintain surface quality in fixed abrasive polishing. Normalized Preston coefficients that are the index of the polishing capability of a certain polishing process considerably increase in vibration-assisted polishing process. A mathematic model is set up to interpret the increase in material removal rate for vibration process. The modeled results show that the vibration can improve material removal by increasing vibration amplitude in vertical direction while the horizontal vibration contributes little to increasing material removal rate, which agrees well with experimental results. Aside from material removal, surface morphology of polished glass was also modeled for both vibration and conventional processes. Both experimented and simulated morphology evidence that the vibration some periodic structure on polished surface. The possible mechanism in dry fixed abrasive polishing was also chemically analyzed and a probable mechanism is put forward to clarify the material removal in dry fixed abrasive polishing.     

快锻油压机高压管道的振动分析

针对80kN快锻压机管系振动问题,分析了压力管道振动原因,采用有限元方法,重点对高压管段进行了模态分析与谐响应分析;为避免管道结构共振,分析了增加管夹支承及改变支撑性质对管道振动频率、应力、应变的影响.同时考虑了存在预应力管道的模态分析,得出预应力的存在会使管道固有振动频率略微增加.通过对高压管道进行了流场分析与单向流固耦合作用下动力学分析,获得了管道中流体速度、压力的分布规律与应力、应变云图,得到管道动态力作用下的危险部位,分析结果对快锻压机管道结构设计具有一定理论与实践意义.     

结晶器振动系统机电液协同仿真技术研究

连铸机铸坯质量的好坏与结晶器振动系统的工作性能关系密切,应用ADAMS建立了结晶器振动系统刚柔耦合机械模型,并在MATLAB中根据机械电气液压的关系,搭建了控制框图,利用软件之间的接口建立了结晶器振动系统协同仿真模型,并对正弦和非正弦信号下的结晶器动态响应进行了分析,该方法可以为冶金机电液设备的设计与优化提供理论指导。根据现场测试的数据,对振动系统刚柔耦合机械模型进行了验证,结果表明所建立的模型是正确的。     

Shear Model of Metal Melt Flowing on Vibration Wall and Effect of Shear Stress on Solidification Microstructure

In this work,the shear model of metal melt flowing on vibration surface is established,and coupling effects of vibration and shear on the distribution of shear stress in melt and melt solidification microstructure are analyzed.Calculation results show that the transition of melt from laminar flow to turbulent flow occurs earlier with increasing vibration frequency and vibration amplitude.In the laminar flow melt,shear stress in melt decreases with increasing vertical length,but it decreases firstly and then stabilizes with increasing flow length.In the turbulent flow melt,shear stress decreases firstly and then stabilizes with increasing vertical length,but it increases with increasing flow length.With the increase in vibration frequency and amplitude,shear stress along flow direction in laminar flow melt increases,while shear stresses along both flow direction and vertical direction in turbulent flow melt increase.Shear stress in melt decreases with increasing length along vertical direction.With the increase in flow length,shear stress decreases firstly and then stabilizes in laminar flow melt,while it increases in turbulent flow melt.With the increase in vibration frequency and amplitude,shear stress increases in laminar flow melt,while it stabilizes in turbulent flow melt.Based on theoretical calculation,the maximum shear stress in melt during vibration shear flow is always much lower than the yield strength of a-Al grain,so the shear stress induced by vibration shear flow cannot break columnar crystal,which agrees with the experiment result.So,the model can explain the shear constitutive relation of melt flow on vibration surface relatively well.     

Control of ball screw drives based on disturbance response optimization

This paper presents a new method for designing control laws for ball screw drives by directly optimizing the load side disturbance response against cutting forces. The design applies, concurrently, the principles of pole placement and loop shaping, and is easy to implement in practice. In addition to good low frequency disturbance rejection, the control law provides active vibration damping, which reduces the magnification of tracking errors near the drive's mechanical resonance. Effectiveness of the proposed strategy is demonstrated in machining and high speed tracking experiments, where its performance is compared to the industry standard P-PI cascade control law.     

Effect of nanoclay on vibration welding of LLDPE nanocomposites in presence and absence of compatibiliser

Abstract

Welding is employed to develop bonded joints with mechanical properties that draw near the parent material. Vibration welding has been applied to join pure and nanoclay filled linear low density polyethylene (LLDPE). Ethylene maleic anhydride copolymer (PE‐g‐MA) is used as a compatibiliser in this study. High resolution transmission electron microscopic images showed the combination of exfoliation and intercalation of nanoclay platelets in LLDPE in the presence of a compatibiliser. The mechanical properties were studied for both the body part and the welded joints. The tensile strength and modulus of the body part for the nanoclay filled LLDPE in the presence of a compatibiliser were substantially improved. The welded joints of the same system showed better enhancement in the modulus. X‐ray diffraction analysis observed from the welded joints showed that the crystallite size of the nanoclay filled LLDPE composites in the presence of a compatibiliser was lower than that of nanocomposites in the absence of a compatibiliser.     

轧辊表面裂纹位置确定方法研究

轧辊是轧钢生产中的主要部件,在复杂应力下容易产生表面裂纹,对轧辊的使用寿命、轧材质量有严重的影响,因此轧辊表面裂纹检测至关重要.轧辊出现损伤时,其固有频率也会发生改变.采用振动法比较分析不同位置的表面裂纹对轧辊固有频率、位移模态、应变模态和一阶模态下轴向位移频响函数的影响.结果表明:一阶模态下的轴向位移对轧辊表面裂纹位...     

车用电子水泵噪声和振动特性试验分析

设计试验方案对不同的电子水泵进行NVH试验,在不同工况下通过数据采集系统对电子水泵的噪声和振动信号进行记录和分析.试验结果表明:电子水泵径向噪声明显大于轴向噪声;试验泵的噪声明显大于对标泵;在电子水泵的加速过程中,转速波动是电子水泵产生噪声和振动突变的主要原因.通过分析电子水泵噪声阶次图,发现电子水泵在4500 Hz频...