液压缸缸体 材料 缸径 承受压力与安全系数之间的关系

本文以强度理论为依据,推导出了液压缸缸体材料、缸径、承受压力与安全系数之间的关系.从而使工程技术人员在设计中能根据已知参数迅速、简便地求得其安全系数.     

全矢谱技术在轴振与瓦振信号处理中的应用

建立了转子-滑动轴承-基础动力学分析模型,利用全矢谱技术分析了转速对轴振和瓦振以及轴振与瓦振比例关系的影响程度.结果表明,在刚性转子条件下,瓦振与轴振椭圆轨迹随转速变化较为相似;而在柔性转子条件下,两者主振矢之比和副振矢之比随转速变化更为相似.该结论为全矢谱技术在轴振与瓦振信号处理中的应用提供了理论参考.     

The Effect of Time,Temperature, and Environment on the Sliding Behavior of Polytetrafluoroethylene

In sliding tests, a weighted sled on PTFE runner, was pulled over a PTFE track by a stationary friction force. It was found that the sliding speed was influenced by rest periods between tests and by the nature of the preceding experiment. These time effects were investigated and are described.

Other sled tests were carried out with curved contacting surfaces such as a surfaces such as a cross-cylinder and a sphere-on-flat geometry. Sliding speeds of PTFE sliding against steel and against itself were measured for several stationary friction forces. Time effects were checked.

Friction tests were made with a scratch tester by dragging fine diamond styli across a flat PTFE surface and the results compared with free-rolling friction.

Experiments were also conducted in dry nitrogen, in air of various humidities, and in pure helium and oxygen. The results are described.     

摩擦副组合对摩擦磨损性能的影响

在1：1惯性力矩制动试验台上研究了两种不同石墨形态的铸铁制动盘与两种混杂纤维增强的酚醛基制动闸片配副时的摩擦磨损性能。结果表明，对于某一配方的制动闸片，使用灰口铸铁盘的摩擦副具有较高的摩擦系数，但制动盘表面温度较高，闸片磨损量较大；对于某一种制动盘，使用B配方制动闸片时，制动盘表面的温度较高，但闸片的磨损量较小；在所有四种组合中，B配方制动闸片与灰口铸铁盘配副的瞬时摩擦系数能够完全满足有关技术要求。     

阀门流量系数和流阻系数计算式中量单位的分析

分析了公英制流量系数单位的导出过程和计算式的转换过程,探讨了多项标准的流量系数定义和计算式中量的单位。同时分析并提出修正流阻系数计算式及流量系数和流阻系数关系式。建议在阀门流量系数的通用计算式中引入公英制单位换算系数,用介质的相对密度代替密度。     

不同流量系数下叶顶间隙对离心压缩机模型级性能的影响

通过CFD技术,分析了不同流量系数下叶顶间隙对离心压缩机模型级性能的影响。结果表明,对于中、小流量系数模型级,叶顶间隙越大,其效率曲线下降越大,而对于大流量系数模型级,有一定的叶顶间隙可改善叶轮内流场,反而有利于离心压缩机效率性能。无论何种流量系数模型级,存在一定的叶顶间隙则可提升能头曲线。     

The effect of frequency of vibration and humidity on the coefficient of friction

Variation of friction coefficient with the variation of frequency of vibration and relative humidity is investigated experimentally on a mild steel disc. A pin-on-disc apparatus having facility of vibrating the disc at different frequency and amplitude is used for the experiment. During the experiment, normal load, speed and relative humidity were varied. The surface conditions of the mild steel base plate were ‘as-turned’ and ‘as-ground’. It is found that friction co-efficient under no vibration condition is higher than that under vibration condition, and the values of friction co-efficient decrease with the increase of frequency of vibration. Similarly, the friction co-efficient decreases with the increase of relative humidity. It is also observed that the rate of reduction of friction co-efficient has a particular relationship with the frequency of vibration and the relative humidity.     

刹车盘对双定子风力发电机主轴振动的影响

作为双定子风力发电机的关键部件,主轴的振动特性直接关系到机组的工作性能。为获得发电机主轴的振动特性,从转子动力学理论出发,应用有限元软件ANSYS对两种结构主轴进行了模态分析,研究了两种结构主轴的固有频率和振型、及振动的特点。分析得到：刹车盘对主轴结构的第一阶固有频率影响不大,但是对主轴结构的振型有较大影响,为发电机主轴及整体结构的设计提供了理论依据。     

对预测含间隙机构运动副元素分离方法的修正

本文通过解析分析，对文献［１］提出的对含有间隙运动副的平面连杆机构中运动副元素分离的预测方法进行了修正，提高了原方法的预测精确性，使得对平面连杆机构运动副元素分离的预测更准确有效。     

基于ANSYS的1.5MW风电机组斜齿轮轴的有限元分析

以风电机组齿轮箱的斜齿轮轴为对象,首先将Pro/E实体模型导入ANSYS建立有限元模型,在此基础上,对斜齿轮轴进行线性静力分析,最后得出形变和应力分布结果。并以此为据判断强度和刚度条件,提出轴的改进方案,提高了设计的可靠性。     

The effect of amplitude of vibration on the coefficient of friction for different materials

This work examines how friction coefficients are affected by amplitude of normal vibration at different frequencies. Variation of friction coefficient with the amplitude of normal vibration is investigated experimentally when mild steel pin slides on different types of material such as glass fiber reinforced plastic, cloth reinforced ebonite, polytetrafluoroethylene (PTFE), rubber and mild steel. For this, a pin-on-disc apparatus having facility of vibrating the test samples at different amplitudes and frequencies of vibration was designed and fabricated. During the experiments, the effects of sliding velocity, roughness, normal load and duration of rubbing were also investigated. Studies have shown that the friction coefficient decreases with the increase of amplitude of vibration within the observed range. The observed ranges of amplitude of vibration were 10–200 μm. In this study, it is also observed that the rate of reduction of friction coefficient has a particular relationship on the amplitude and frequency of vibration. The experimental results are compared with those available in the literature and simple physical explanations are provided.     

微腔对摩擦副摩擦系数的影响机理研究

将微腔模型引入摩擦副摩擦研究,通过建立微腔的气体-压强模型,分析了摩擦副微腔对摩擦的影响机理.并尝试用所建立的模型解释载荷、摩擦副相对运动速度、环境气压、静止接触时间对摩擦系数的影响.     

离合器摩擦副表面温度对摩擦因数的影响

通过对某型离合器摩擦副的摩擦学小样试验,研究了离合器在结合的滑动摩擦过程中,摩擦面温度对离合器摩擦材料摩擦因数的影响.采用扫描电子显微镜(SEM),分析了样件的摩擦表面形貌,探讨了产生影响的机制,并从摩擦因数角度探讨了微车离合器起步发抖和烧蚀的主要原因.微车离合器摩擦材料摩擦因数随着摩擦面温度先升高,然后趋于稳定,最后再降低,其稳定工作的温度区间为130～220℃;在摩擦面温度较低的工况下,摩擦因数较低,微车起步时,离合器传递的扭矩不足以克服道路阻力,引起微车起步发抖的现象;而在摩擦面温度过高的工况下,离合过程中,摩擦因数较低,传递扭矩效率低,导致离合器滑磨时间过长,引起烧蚀现象.     

Effect of Bearing Surroundings on the High-Speed Spindle-Bearing Compliance

This paper investigates the effect of bearing assembly tolerance on spindle-bearing compliance. In a high-speed spindle system, the bearing characteristics are influenced significantly by the initial assembly tolerances and the thermal deformation of the bearing surroundings. In the very early stage of spindle operation, spindle bearings could be under hazardous conditions owing to the rapid change of the internal pressure resulting from thermal deformation or centrifugal force-oriented deformation. The bearing’s internal clearance also may be changed by the operating conditions such as external load, rotational speed, and operating cycle time. To determine the initial tolerance and the optimal cooling regimen, a comprehensive dynamic modelling and analysis of a high-speed spindle system in terms of bearing pressure, bearing compliance, and heat generation is required with consideration of those effects. Moreover, in order to predict spindle characteristics in operation, all of these parameters should be monitored and recalculated in real-time. For this purpose, very simple and effective equations are suggested, representing the bearing stiffness in accordance with the thermal deformation. Most former bearing analyses were based on the Hertzian contact model, without considering the radial elastic defor-mation of the races. In this paper, analytical and experimental investigations of the bearing compliance are conducted with consideration of both the elastic deformation of the race and the thermal deformation of the housing in terms of the bearing stiffness. The experimental results show the effectiveness of the proposed equations, which are simple and useful for fast calculation of the bearing stiffness by dynamic simulation.     

动静压技术在磨床内圆磨具精化中的应用

介绍了一种具有动静压技术原理的缝隙节流静压轴承在普通万能外圆磨床内圆磨具精化中的应用。经过对该机床精化。提高了机床加工精度和质量寿命。实践证明该方法简单有效，对旧机床的改造有一定参考作用。     

固结磨料研磨垫孔隙结构对其加工性能的影响

为了解决铜在研磨过程中铜屑黏附减小了容屑空间,易导致研磨垫钝化问题,本文尝试在亲水性固结磨料研磨垫（FAP）内部添加硫酸镁晶体,利用硫酸镁晶体遇水溶解的特性,在研磨垫表面制造不同特征的孔隙。实验在FAP中添加粒径为8目、170目、500目的硫酸镁晶体制造了3种不同孔隙分布的研磨垫,研究了不同加工参数下FAP研磨铜片时的材料去除速率、摩擦系数、表面形貌及磨屑特征。结果表明,仅含170目硫酸镁的FAP与含8目和500目硫酸镁、质量分数分别为5%和10%的FAP在研磨过程中出现了不同程度的钝化,而FAP表现出良好的自修整性能,研磨过程摩擦系数较大且保持平稳;在研磨液流量为60 ml/min时,其材料去除速率为4.46 μm/min,表面粗糙度R_a为159 nm。     

Experimental study of discharge coefficient of trapezoidal arced labyrinth weirs of widened middle cycle

Arced labyrinth weir is a certain type of nonlinear weirs with a very high discharge capacity. Thanks to the increased effective length and the ensuing increased discharge capacity of these weirs, they can be used in dam spillways and water regulating structures. This study focused on trapezoidal Arced labyrinth weirs (TALW) of widened middle cycle. Various experiments were performed to evaluate the effect on discharge coefficient of various geometric parameters, including the ratio of inside apex width of the end cycles to that of the middle cycle (w₂/w₁) and the ratio of the length of labyrinth weir (Apron) in flow direction to the width of the middle cycle (B/w₁). Results of this study showed that with a decrease in w₂/w₁ from 0.42 to 0.30, discharge coefficient (C_d) would increase by 13–33%.     

水压泵柱塞摩擦副间隙优化及影响因素分析

基于热平衡原理提出了水压泵柱塞摩擦副的间隙优化公式,对结构尺寸、对偶材料配对以及环境参数等影响因素进行了仿真和试验研究。研究结果表明：每对柱塞摩擦副都存在一个最小的热平衡间隙,水压泵柱塞摩擦副的初始间隙必须大于这一间隙,否则就容易发生卡死现象;减小柱塞直径或斜盘倾角、选择合适的对偶材料、减小摩擦因数和充分跑合都是减小最小热平衡间隙的十分有效的措施。     

Experimental study of discharge coefficient for trapezoidal piano key weirs

Piano Key Weirs (PKW) have been invented in the last decade to increase discharge capacity of hydraulic structures. Despite extensive studies on this type of weir with a rectangular plan form (RPKW), there are only a few pieces of research addressing trapezoidal piano key weirs (TPKW). In this experimental study, geometrical parameters of TPKW models were varied under different flow conditions and effects on discharge coefficient (C_d) were investigated. The C_d values were found to be mostly influenced by L/W whereas W_i/W_o had the least effect. Results also showed that TPKW has higher discharge efficiency in comparison with RPKW. This was believed to be related to formation of an “interference wedge” over the TPKW. Finally, quantitative values for distinguishing three flow regimes (i.e. nappe, transition and submergence) as well as criteria for design of TPKW are proposed.     

中低速齿轮副效率与齿数及中心距有限增量的关系

对中低速渐开线直齿齿轮机构稳定运行时齿轮副传递的有效功与齿间摩擦系数,齿数及中心距有限增量等有关参数的关系进行了分析和研究,导出一组可直接确定中低速齿轮副效率的方程组,由该方程组所显示的关系可知,齿轮副效率不仅直接与齿间摩擦系数有关,而且还随齿数、传动比及中心距有有限增量等参数变化而变化。