天车定滑轮轴防护装置的设计

天车通过定滑轮的转动带动钢丝绳收放完成吊运作业,钢丝绳从定滑轮脱槽后极易造成钢丝绳在定滑轮轴上直接摩擦,致使定滑轮轴磨损断裂,从而导致吊物、吊具、吊钩及钢丝绳瞬间坠落的重大安全险肇事故发生。为此,设计了一套定滑轮防护装置,用以避免钢丝绳脱槽情况的发生,提高定滑轮轴及钢丝绳的使用寿命,也为同类设备的改进提供一定参考。     

挖掘机销轴的断裂失效分析

挖掘机的销轴在工作过程中发生断裂。本文通过对断裂销轴的宏观断口、微观形貌、显微组织、化学成分、材料硬度及销轴的受力等分析,结果表明,销轴断裂为典型的疲劳断裂。疲劳源位于油孔处,属油孔部位应力集中造成的。因此,油孔位置设计不合理是销轴断裂的主要原因。另外,疲劳源始于油孔内的切削刀痕,切削刀痕也是销轴断裂的原因之一。结合以上分析,本文提出了解决问题的方法,优化了工艺路线方案,为提高销轴的使用寿命指明了方向。     

锪抛轴油孔过渡圆角工具

在机械零件中的轴与轴套有转动要求时,需注加润滑油。润滑油一般是由套上的油孔流入转动表面的,也有从轴孔流入转动表面的。如内燃机的曲轴就是这样。轴上的油孔一般在设计时都考虑防止油孔口刮伤轴套。要求在油孔倒角处还要倒一个过渡圆角(图1)。它表面粗糙度一般不超过     

海上平台起重机A字架定滑轮销轴拆装装置研究与应用

海上平台起重机A字架顶部定滑轮销轴随着磨损的增加会出现异常响声,需要对其进行拆除更换,针对海上平台起重机A字架顶部定滑轮销轴拆装的特点,设计了一套拆装装置,通过所设计的装置将定滑轮固定,从而方便销轴拆装工作,并在实际生产中得到成功应用。     

高速高压轴向柱塞泵缸体的气穴机理研究

以斜盘式柱塞泵为例,利用计算流体动力学(computational fluid dynamics,CFD)仿真分析计算了其在同一转速下不同直径比的情况下气穴发生情况,给出在保证泵流量情况下柱塞及吸油孔极限直径比的计算公式。并比较了在同一工况同一直径比不同进油口结构的气穴情况。通过计算结果的分析知道柱塞直径与吸油孔直径的直径比对缸体的气穴影响较大,不同的吸油孔结构对气穴的影响较大。从气穴产生的原因分析柱塞泵的气穴,对于柱塞泵缸体及柱塞的设计提供了理论依据及设计指导。     

单向皮带滑轮组接触强度及承载特性的研究

通过对单向皮带滑轮组接合以及分离过程中的受载特点进行了理论分析,得出该类构件结构性能的相关结论,并对该类构件影响因素进行了分析。在此基础上,基于有限元理论,借助于ANSYS Workbench建立了单向皮带滑轮组的有限元计算模型,研究了不同摩擦系数对单向皮带滑轮组各个部件承载的影响,分析了单向皮带滑轮组的工作过程中的接合、分离特性。并与传统的赫兹理论计算结果及有限元计算结果进行了对比,证明了该有限元模型的正确性。以上研究成果对设计、优化单向皮带滑轮组的工作特性具有指导意义。     

起重机起升滑轮轴承损坏原因及改进措施

正某履带式起重机在使用中,其臂架顶端滑轮组轴承经常出现损坏,由此造成滑轮组不能旋转、钢丝绳严重磨损,导致该起重机不能正常施工。为此我们对其原因进行了分析,提出了改进方法,并制定了预防措施。1.臂架顶部结构该履带式起重机臂架顶部结构主要由上节臂、导向滑轮组、起升滑轮组等组成,如图1a所示。其中起升滑轮组主要由轴承、滑轮、隔套、起升轴等组成,如图1b所示。每个起升滑轮内安装有2个滚动轴承,轴承安装在起升轴上,起升轴安装在上节臂顶部,轴承之间使用隔套     

接触网滑轮组传动效率试验研究

本文对接触网滑轮组传动效率试验进行了研究。在原有PLS-40型接触网零部件疲劳试验机的基础上设计了一套位置加载系统。用采测试滑轮组在不同传动比下的传动效率。通过服务器／客户端的结构实现了传动效率的实时联机传送，由客户端对数据进行处理、储存以及打印报表。     

新型水润滑动静压高速主轴轴承的流场模拟

轴承过热会造成高速高刚度主轴抱轴,导致主轴失效。如何提高小间隙轴承内的泄油量来降低轴承温升,是高速高刚度主轴轴承设计必须考虑的重要因素。提出一种新型的可应用于高速机床主轴的高速水润滑多孔阶梯轴承,应用FLUENT软件对其流场进行模拟分析。根据轴承的对称性,选用1/8轴承建立流场分析模型。分析结果表明,可以在同一个深腔内开设有进出油孔的结构,从进油孔节流后流入深腔的润滑油不会无效泄漏,可达到降低轴承温升的目的;深腔内的润滑油为紊流,而浅腔中润滑油紊流现象逐渐减弱;进油孔的节流形式为孔式环面节流。     

无碳小车绳轮机构的设计

对可提供4 J重力势能的无碳小车的绳轮机构进行了设计。在设计中,选取定滑轮材料为尼龙,并采用控制变量法对不同材料绕绳的打滑率进行了计算,确认选择聚氯乙烯为绕绳的最佳材料。在初始条件一定的条件下,对绳轮机构的预紧力进行研究,确认预紧力不小于0.5 N时,无碳小车的打滑率最低。通过对绕绳轴直径进行分析,确认圆锥形轴在保持无碳小车平稳性方面具有优越性,并确定圆锥形轴的锥度为4°,底面直径为40 mm,高度为70 mm。     

基于有限元的起重机滑轮轴力学分析

基于有限元理论,选取常规起重机中所用典型吊具滑轮轴,分别对具有不同形式润滑槽的滑轮轴进行应力分析,以探究润滑孔对滑轮轴力学性能的影响。     

变形轴机械定心基准面位置的分析与计算

应用几何图形,分析了变形轴中心孔与其最大内接圆柱体的关系;建立数学模型,计算了变形轴打中心孔时机械定心基准面的最佳位置。计算结果表明:机械定心基准面的最佳位置与轴的长度成正比,与轴的直径和弯曲扰度无关,对所有圆柱轴具有通用性。计算结果为圆柱体加工中心孔实现机械化装夹,并从变形轴中切出最大内接圆柱体,提供了理论依据;对纠正圆柱轴弯曲变形,减少加工余量,提高生产效率和加工精度具有实用意义。     

变速箱变速叉轴断裂分析及优化设计

以变速箱变速叉轴为研究对象,通过对变速叉轴断口位置及形状的分析,给出变速叉轴的优化设计方案。针对优化后的变速叉轴,应用Pro/E软件建立三维数模,应用ANSYS Workbench软件进行强度分析,得出变速叉轴强度满足设计要求。应用ANSYS Workbench软件,结合变速叉轴强度分析结果,计算可知当换档导块实际承受的载荷为1 700 N时变速叉轴的使用寿命为1.2×105次,可以满足变速箱的设计要求。     

Study on the progressive forming mechanism of multi-step shafts based on convex-end billet in the cross wedge rolling technology

The deforming process is complicated and both the end concave and the central defect can be easily formed in multi-step shafts shaped by the cross-wedge rolling technology. To realize the accurate forming of multi-step shafts without stub bar, this article breaks the bondage of traditional flat-end billet, and introduces into convex-end billet. Based on established mechanical models and the damage computation principles, the distribution and change features of stress fields, strain fields and microstructures in different segments of the multi-step shaft during the progressive forming process are analyzed, and the location of the central defect is predicted. It is found that the concave depth of shaft ends decreases as the length of the convex-end of billet increases, the microcosmic grains are affected by the section shrinkage of the shaft segments and the larger the section shrinkage is, the smaller the size of the microcosmic grain will be. It records the longest duration of maximum stress, the largest fluctuation of lateral stress and the most frequent cycle of transverse strain in the multi-step shaft end and therefore the central defect is most likely to occur. The research findings settle a dependable theoretical basis for enhancing the molding quality and realizing the accurate forming for multi-step shafts in cross wedge rolling.

     

Lapping high precision polygonal shafts

Lapping has been used as a finishing method to improve roundness accuracy of cylindrical shafts and holes. However, little has been published on the theoretical analysis of the finishing mechanism for high precision polygonal cross sections. This paper offers a method for finishing polygonal shafts, whose shapes are ellipsoidal, triangular, four-lobed and so on. By this method, the amplitude can be increased for any Fourier component of out-of-roundness. Special types of lapping tools were produced by applying the ‘V-block’ roundness measuring method. Using one of the V-block lapping tools, the magnitude for the four-lobed component was increased form 8.4 μm to 9.9 μm, while the other components were decreased; out-of-roundness improved from 35 μm to 25 μm. By setting the angle between the supporting teeth at an appropriate value, any polygonal shaft can be finished with these laps. This method is also applicable to finishing polygonal holes     

进口多级泵国产化转子的改进方案

对进口多级泵国产化转子失效的原因进行了分析,按材质、温度及受力状况,校核计算孔、轴配合的最大允许过盈量和最小过盈量,确定叶轮孔与轴颈配合的公差.根据计算确定的公差值对国产化转子轴进行改进并完成转子装配,使国产化转子达到可靠备用状态.     

Design, manufacture and evaluation of a new and simple mechanism for transmission of power between intersecting shafts up to 135 degrees (Persian Joint)

This paper introduces a new mechanism which is designed for the transmission of power between two intersecting shafts. The mechanism consists of one drive shaft and one driven shaft, six guide arms, and three connecting arms. The intersecting angle between the input shaft and the output shaft can be varied up to 135° while the velocity ratio between the two shafts remains constant. The research also includes a kinematic analysis and a simulation using Visual NASTRAN, Autodesk Inventor Dynamic and COSMOS Motion. The softwares showed that this mechanism can transmit constant velocity ratios at all angles between two shafts. By comparing the graphs of analytical analysis and simulation analysis, validity of equations was proved. Finally, by fabrication and evaluation of the mechanism it was shown that this mechanism can transmit constant velocity practically.     

油膜轴承传动轴系动载系数计算方法

针对传动轴系动载荷变化难以准确用数学函数描述的问题,基于刚体动力学理论,综合考虑轴系刚性与弹性振动特性,提出近似求解动载荷的分析方法,建立轴系动载荷分析模型。通过分析现有油膜轴承试验装置中传动轴系的机械结构组成,推导传动轴系在启制动工况突变时的动载系数计算公式;根据传动轴系的结构参数,确定动载系数取值范围;同时给出该动载系数模型在工程应用中的典型形式。计算表明：轴系在启制动之前,相比没有静压润滑的情况,使用静压润滑的油膜轴承的动载系数相对较小,振动对其油膜稳定性的影响较小。     

Development of a rotary clap mechanism for positive-displacement rotary pumps: Kinematic analysis and working principle

A five-bar spatial mechanism named as a rotary clap mechanism is developed as a pumping device for positive displacement rotary pumps. The mechanism comprises a driving crank, a shaft link with two pins and two gears mounted on the middle and both ends, two rotors with jaws equally spaced along their circumferences, and two fixed internal gears. As the crank rotates, the gear pin-jointed to the crank rotates about the crank pin and at the same time rotates about the center of the fixed internal gears like a hypo-cyclic gear train. The gear-attached shaft link also rotates about the crank pin and about the fixed internal gears at the same time. This motion of the shaft link makes the pins rotate about the center of the fixed internal gears with a periodically varying radius. Therefore, two rotors driven by the pins rotate with different angular velocities. One rotor alternately leads and lags relative to the other rotor. These lead-lag motions between the two jaws of the rotors, which result in suction and discharge required for pumping, resemble hand clapping from which the mechanism was named. Construction and design parameters of the rotary clap mechanism are introduced, and kinematic analysis of this mechanism is performed. The relationships among design parameters, inherent constraints, and effects of design parameters on the displacement of mechanism are also presented.     

Friction analysis according to pretension of laparoscopy surgical robot instrument

Surgical robot instruments are driven by using cable-pulley structure. The elasticity at cable-pulley structure causes slack effect of cable. Elastic region of cable must be compensated for preventing the slack. The surgical instrument inputs a pretension for compensation at cable’s elastic region. Therefore pretension is an important factor in the design of a surgical instrument. However, the pretension is related with friction force which is affected by normal force at the driving shaft pulley. The shaft and contact surface of the pulley consist of sliding bearing structure. Typically, the friction coefficient in the sliding bearing structure is determined by the Petroff equation. The pressure of Petroff equation is related to the denominator of the equation. Therefore increasing normal force brings about an effect which decreases friction coefficient. Eventually, in theoretically, that means the pretension can be increased to infinity to decrease friction coefficient. However actual result comes out different. Therefore in this paper, the friction analysis method according to a pretension is proposed and an experiment method for the analysis of the friction is introduced. The correlation between pretension and friction is estimated by the analysis. The estimated result is compared with the experiment one and is analyzed. Also finally this paper suggests an appropriate pretension for surgical robot instrument by the friction analysis result.