An initial investigation of the damped resonant behaviour of gas-operated pressure balances

The aim of this investigation into the damped resonant behaviour of the piston of gas-operated pressure balances is to provide insights into ways of improving the short-term performance of gas-operated pressure balances. Initial measurement results are reported for the damped resonant behaviour of two different pressure balances as a function of system volume. The pressure balances are operated using air in absolute mode at 100 kPa and the system volume is varied from about 10 mL to 250 mL. Values for the period, the logarithmic decrement λ and the Q of the oscillation are obtained by fitting the measured damped oscillatory motion of the piston height to a classical damped oscillator model. Results show that the damping is dominated by non-adiabatic pressure variations in the system volume and not by viscous damping of the vertical motion of the piston in the cylinder. The settling time for the oscillations to damp out is primarily determined by the period of oscillation with a lesser influence from variations in λ. Implications for improving pressure balance performance are discussed.     

具有动压反馈的配流轴设计方法

径向柱塞泵配流轴摩擦副的静压支承系统,采用动压反馈设计思想增加压力补偿元件,能有效地防止配流轴摩擦副的“抱轴”。     

Development of low-pressure calibration system using a pressure balance

A new calibration system for low-pressure is now under development at NMIJ/AIST. The new system is designed to calibrate pressure transducers in the pressure range of less than 10 kPa in absolute mode. The pressure generation technique needs only a single pressure balance and the pressure in the bell-jar is used as a calibration pressure instead of the system pressure. In this paper, the outline of the calibration system and the measurement results are described.     

聚合物挤出压力测试系统设计方法及功能分析

从挤出过程中压力的特点 ,提出了对测试系统有采样频率的要求。最后,从使用者的角度和挤出试验的特点出发,给出了一套测试系统所应该具备的功能。     

Computer simulation of a 1.0 GPa piston–cylinder assembly using finite element analysis (FEA)

The paper reports a preliminary study of the behavior of a high performance controlled-clearance piston gauge (CCPG) in the pressure range up to 1 GPa through finite elemental analysis (FEA). The details of the experimental characterization of this CCPG has already been published (Yadav et al., 2007 [1]). We have already pointed out that the use of Heydemann–Welch (HW) model for the characterization of any CCPG, has some limitation due to the fact that the linear extrapolation of the cube root of the fall rate versus jacket pressure (v^1/3–p_j) curve is assumed to be independent of the rheological properties of the pressure transmitting fluids. The FEA technique addresses this problem through simulation and optimization with a standard ANSYS program where the material properties of the piston and cylinder, pressure dependent density and viscosity of the pressure transmitting fluid etc. are to be used as the input parameters. Thus it provides characterization of a pressure balance in terms of effective area and distortion coefficient of the piston and cylinder. The present paper describes the results obtained on systematic studies carried out on the effect of gap profile between piston and cylinder of this controlled-clearance piston gauge, under the influence of applied pressure (p) from 100 MPa to 1000 MPa, on the pressure distortion coefficient (λ) of the assembly. The gap profile is also studied at different applied jacket pressure (p_j) such that p_j/p varied from 0.3, 0.4 and 0.5.     

扩散硅压力传感器热灵敏度漂移补偿方法的研究

分析了恒压源供电和恒流源供电两种情况下扩散硅压力传感器的灵敏度随温度变化的关系式，提出了用软件补偿其热灵敏度漂移的计算方法，并且就恒流源供电且灵敏度温度系数大于零的情况，推出了用并联电阻补偿热灵敏度漂移时，并联电阻阻值的计算公式，模拟结果表明补偿效果非常显著。     

农船螺旋桨静平衡检验方法的确定

本文通过建立螺旋桨静平衡的力学模型,结合国内外现有螺旋桨标准,对其静平衡作些浅短的分析、比较,从而定出农船螺旋桨静平衡的检验方法.     

液压系统油液压力非插入式测量的新方法

本文基于液压系统压力变化引起油液声速变化这一物理特性,提出了通过测量超声波在油液中的传播速度实现压力非接触式测量的新方法,该方法不但完全克服管道壁厚影响,而且有效地消除固有声电延时误差,达到了较高的测量精度,所研制的非插入式压力检测系统是实现液压系统快速故障定位的先进检测手段,具有重要的应用价值。     

均匀化理论在多孔板结构优化中的应用研究

多尺度均匀化理论自从上世纪 70年代产生以来 ,就被认为是确定复合材料当量性能的一种不可替代的方法。本文将多尺度均匀化方法应用于基于有限元分析的多孔板结构优化设计中 ,简述了求解当量板有效弹性常数的均匀化理论 ,在此基础上 ,建立了基于有限元分析的多孔板结构优化流程 ,编写了FORTRAN程序 ,并将其与AN SYS软件相连接 ,完成了一个多孔板结构的优化设计 ,所得结果表明 ,它能够满足工程应用的需要 ,并为多孔板结构设计提供了一种新思路     

新型电梯平衡系数测量系统的研究

针对传统的电梯平衡系数测试中,人工检测平衡状态所带来的误差大、效率低、成本高等问题,设计了一种基于超声波的电梯平衡状态自动检测系统,该系统运行后无需人工干涉,在电梯运行过程中自动检测平衡状态,并通过无线传输检测结果,准确、稳定、高效、安全。该系统摒除了人为因素对获取平衡状态的影响,使检验手段更加科学合理。     

软囊式水下力传感器的力学特性与设计原则

以水下机器人用多轴力传感器的压力平衡结构为研究对象,基于液体的可压缩性,根据弹性薄壳力学分析,选择长壳理论研究软囊变形,并对其进行修正。指出软囊变形所引起的额外轴向力对设计和使用水下力传感器是不可忽视的,提出软囊式压力平衡传感器内外压力差的迭代算法,推导出软囊式压力平衡的内外压差、额外轴向力及相关公式。分析压力差在传感器上产生的额外轴向力及有关的影响因素,总结软囊式压力平衡能够胜任大压力平衡,且对大压力下的微小压力具有极强的平衡能力的特点。得出软囊式水下力传感器结构应紧凑、长径比应小、壁厚应尽可能小、内部存油液应少的设计原则。     

面向手握舒适度应用的分区压力评测方法研究

针对目前手握舒适度研究没有具体的量化评估这一问题,在分析手握时手部功能与了解手部解剖结构的基础上,对手部进行了分区,分析了各个分区生理特性与分区压力数据指标的关联性,提出了分区压力的评测方法,为进一步研究手握舒适度提供了新的思路.     

影响曲轴不平衡的因素及控制方法

通过优化铸造模具设计，控制曲轴两端面工序，控制打中心孔工序和动平衡去重加工工序来控制曲轴不平衡量。     

带式输送机液粘软启动装置的特性及其控制

给出了液粘力矩传递公式及其特性曲线,分析工作特点并设计出了液粘控制系统,为解决多机拖动系统中功率不平衡问题,提出了基于平均电流的模糊控制方法,并在工程中得到验证。     

轴向槽圆柱气体动压轴承的性能研究

采用有限差分法计算轴向槽圆柱气体动压轴承的压力分布,计算轴承的承载能力和偏位角.分析显示,轴向槽位置对轴承性能有较大影响.通过计算结果与相关文献的相应数据进行对比证明,该计算方法的可行性.     

Measurement of the elastic constants of pressure balance materials using resonance ultrasound spectroscopy

To minimise the uncertainty in pressure measured with a pressure balance its pressure distortion coefficient should be determined with a sufficiently low uncertainty. The elastic constants of piston–cylinder assembly (PCA) materials are used in the calculation of the pressure distortion coefficient and thus are one of the uncertainty sources. In this work, the resonant ultrasound spectroscopy (RUS) is applied to determine the elastic constants of PCAs’ tungsten carbide (WC) materials. A validation of the RUS technique has been carried out by measurements on rectangular parallelepiped and cylindrical samples of fused quartz, steel D22S (30CrNiMo8) and a well-known WC material. The WC materials which are used in new 7 MPa absolute pressure balances aimed at a redetermination of the Boltzmann constant have been studied. The measurements demonstrate RUS to be suitable for determining the Young modulus (E) and the Poisson ratio (μ) with standard uncertainties as low as 0.03% and 0.05%, respectively. They show variations in E and μ of up to 4% and 2%, respectively, for different batches of nominally the same material. In a few cases, even for samples cut out of the same WC piece, material inhomogeneities have been observed in both RUS and the density measurements with variations in E and μ of up to 0.8% and 0.5%, respectively.     

压力平衡型指尖密封结构影响因素研究

采用有限元接触分析方法研究了背压腔位置设置和尺寸、指尖曲梁型线和指尖数目对压力平衡型指尖密封工作性能的影响规律。主要探讨了这种指尖密封结构在一定密封流体压差和不同转子径向跳动量条件下 ,对密封性能的影响规律 ,研究工作及结果为压力平衡型指尖密封的结构设计提供了参考依据。     

转子动平衡影响系数法改进

影响系数法是转子动平衡的重要方法。本文结合动平衡实践,针对平衡过程中影响系数法存在的一些问题(残余振动量偏大、配重质量受限等),提出了3种改进方法:即加权迭代最小二乘法、限制配重的最小二乘法和基于遗传算法的最小二乘法。经过模拟实验验证,本文提出的改进方法是可行的、有效的。     

刚性转子自动平衡控制策略

针对无平衡块位置传感器的质量补偿型自动平衡头 ,提出了刚性转子基于影响系数法的快速平衡控制策略 ,它能不停机地辨识出系统主要特征参数 ,准确计算出平衡块的平衡位置 ,成功地解决了自动平衡耗费时间长、精度不足的问题 ,操作简便。为了尽可能减小各种随机误差对平衡精度的影响 ,还提出了递推改进算法。对该控制策略进行了计算机仿真 ,取得了较为理想的效果。     

The Lubrication characteristics of the vane tip under pressure boundary condition of oil hydraulic vane pump

The Lubrication Mode of line contacts between the vane and the camring in an oil hydraulic vane pump has been investigated. First, the variations of the radial force of a vane were calculated from previous measurements of dynamic internal pressure in four chambers surrounding a vane. Next, the lubrication modes were distinguished with Hooke’s chart, which is an improvement over Johnson’s chart. Finally, the influence of the boundary conditions in the lubrication region on the fluid film lubrication was examined by calculating the film pressure distributions. The results showed that the lubrication mode of the vane tip exists in the rigidvariable-viscosity region, and that discharge pressure higher than 7 MPa greatly affects the oil film pressure in the small and the large arc section because of the Piezo-viscous effect.