Torsional Oscillator Experiments with High Stability and Reproducibility

We report experiments of the torsional oscillator to observe the superfluid transition in ⁴ He films in porous glass (the pore diameter is 1m). Stability and reproducibility of the oscillator, which quite often is problematic in previous experiments, is essential for a quantitative analysis of observations in different conditions. It follows that the friction of the superfluid films and the energy dissipation of the solid films are derived from comparisons of measurements for different film thickness.     

Torsional Oscillator Study of Thin He Films Under High Speed Rotation

Superfluidity is often compared with superconductivity and rotation is contrasted with magnetic field. In the case of superconductors, it is possible to destroy the superconducting state by application of a sufficiently high magnetic field. Agthough it is not yet technically feasible to destroy the superfluid state through rotation, significant modification of the superfluid can be achieved through rotation. In the experiments reported here we are studying the influence of rotation on the dissipation in superfluid films adsorbed in a porous medium. A new peak in the film dissipation is observed while under rotation at a temperature somewhat below the transition temperature. The dissipative feature we observe is related to the resugt for 2D films under rotation previously reported by Adams and Glaberson, however our observations for films in a porous medium under rotation differ considerably in detail. A theoretical discussion of these resugts has recently been given by Fukuda, et al. (to be published).     

Switching of Dislocations in Solid Helium Between Pinned and Unpinned States in the Torsional Oscillator Experiments

The anomalous temperature dependence of the period of a torsional oscillator (TO) containing solid helium can be explained by the dislocation-vibration model. Namely, the dislocations in solid helium vibrate in phase with the torsional oscillation and the TO-period change varies as the square of the average dislocation pinning length which becomes shorter at lower temperature due to pinning of dislocations by ³He impurity atoms. This dislocation-vibration model is further developed by introducing distribution functions for the network pinning lengths for dislocation segments and by considering the mechanisms of pinning of dislocations by and unpinning of dislocations from ³He impurity atoms. Experimental data, such as the TO-period change at different ³He concentrations, the rim-velocity dependence of the TO period, the hysteresis of the TO period with respect to the rim velocity and to the temperature, are analyzed based on the dislocation-vibration model. Above all, the hysteresis is caused by switching of dislocations between pinned and unpinned states.     

Effect of Helium Elasticity on Torsional Oscillator Measurements

In 2004 Kim and Chan performed a torsional oscillator measurement of the rotational inertia of solid helium-4. They found frequency changes which were interpreted in terms of a non-classical rotational inertia, that is a partial superfluidity or ??supersolidity?? of solid helium-4. Since then there have been many further studies using various versions of this technique. One important question that arises in these experiments is the possible effect on the oscillator frequency of changes in the elasticity of the solid helium; this can produce a change in frequency that adds to any effect due to superfluidity. In this paper we give a general discussion of the effect of changes in elasticity on the oscillator frequency and consider how the magnitude of the effect is influenced by the oscillator design. Our results should help make it possible to discriminate between frequency changes due to changes in elasticity and changes due to supersolidity.     

Periodical Oscillation Phenomena Observed in Salt-Water Oscillator Experiments under Small Gravity Conditions

We examined periodical oscillation phenomena that were observed during salt-water oscillator experiments under a small gravity condition. This condition was realized by situating a lower-density gadolinium chloride (GdCl ₃) aqueous solution on a higher-density sodium chloride (NaCl) aqueous solution and applying a downward magnetic force. The GdCl ₃ solution concentration was 0.15 mol/kg (density ρ=1.03×10³ kg/m ³), and the NaCl concentration was varied to (A) 4.35 mol/kg (ρ=1.15×10³ kg/m ³), (B) 3.79 mol/kg (ρ=1.12×10³ kg/m ³), and (C) 2.49 mol/kg (ρ= 1.09×10 ³ kg/m ³). The magnitude of magnetic flux density was varied from 0 to 4.00 T. As the magnetic flux density grew larger, the GdCl ₃ solution was pulled downward by the magnetic force, and upward and downward flows were generated simultaneously at the orifice. These flows were accompanied by a periodical, locally thickened part. The thickened part was only observed when the magnetic force magnitude was small in cases (A) and (B). This flow pattern was not observed in case (C), in which a conventional salt-water oscillation was induced instead (C). In this paper we discuss new experimental results in which the oscillation cycles in cases (A) and (B) are strongly associated with the magnitude of the magnetic force and the density difference in the biphase solutions.     

后驱车动力传动系扭振分析

研究后驱车辆动力传动系扭转振动分析方法,根据实际工程问题,建立合适的仿真模型,计算传动系扭振模态频率,并与测试结果进行对比,验证该方法和仿真模型的正确性;在此基础上,分析了动系各部件对扭振模态的灵敏度,以便项目前期根据目标对扭振模态进行控制。本研究提供了一套有效的传动系扭振的分析方法,并取得良好的工程应用效果。     

Torsional Oscillator Study of Thin Helium Films on Hydrogen Substrates

We have made torsional oscillator measurements of thin helium films on a Mylar surface preplated with 2 and 5 layers of H ₂ . The minimum ⁴ He coverage needed for superfluidity, or inert layer, n _o on both surfaces is found to be 6 mole/m ² . This is equivalent to 1/2 of a monolayer at bulk liquid density. The superfluid transition in coverages above n _o is similar to that found on bare Mylar, exhibiting the standard Kosterlitz-Thouless characteristics. We find no anomaly in _s or the dissipation in the film that can be identified with a second transition reported in recent third sound experiments.     

基于加速度传感器测量扭振方法的研究

介绍一种把加速度传感器直接安装在转子上,在旋转坐标系下测量转子扭振的测量方法.简述其实现原理,设计利用单盘转子产生扭振的实验装置,并进行实验.实验结果与位移传感器测量结果进行比较,表明该方法可以测量小幅值的扭转振动,且具有较高的精度.在旋转状态下进行齿轮实验装置的测试,同样得到与已知故障特征一致的扭振信号.     

含齿侧间隙两挡变速器电动汽车传动系统扭振分析

针对一款含两挡变速器的纯电动汽车,建立电机、电机轴、两挡变速器、变速器中间轴、变速器输出轴、主减速器/差速器总成、左右半轴、轮胎/车身等子模块模型,考虑常啮合齿轮副、一挡齿轮副、主减速器齿轮副的齿侧间隙,建立整个传动系统的非线性扭振动力学模型.运用MATLAB软件,采用龙格库塔法进行数值求解,分别对比分析不同齿侧间隙对...     

Interpreting Torsional Oscillator Measurements: Effect of Shear Modulus and Supersolidity

The torsional oscillator is the chief instrument for investigating supersolidity in solid ⁴He. These oscillators can be sensitive to the elastic properties of the solid helium, which show anomalies over the same range of temperature in which the supersolid phenomenon appears. In this report we present a detailed study of the influence of the elastic properties of the solid on the periods of torsional oscillators for the various designs that have been commonly employed in supersolid measurements. We show how to design an oscillator which measures supersolidity, and how to design one which predominantly measures elasticity. We describe the use of multiple frequency TOs for the separation of the elastic and supersolid phenomena.     

晶体振荡器减振应用研究

由于晶体振荡器在随机振动试验时出现输出波形异常的现象,对该现象进行探讨,并通过运用无谐振隔振技术以及片弹簧知识,确定片弹簧尺寸,安装试验,最终解决了试验中出现的问题。     

发动机曲轴系统扭转振动分析

关于曲轴扭转振动特性的研究是基于在三角皮带轮上的测量结果,而不是那些与三角皮带轮有相对关系的结果.在三角皮带轮上的测量结果包括假设曲轴是弹性时的曲轴扭振和假设曲轴是刚性时的曲轴角速度随气缸压力波动的变化.认为评价曲轴系统扭转振动特性应该用相对角位移而不是在三角皮带轮上测量的扭转振动角位移.     

Measurement Techniques of Torsional Vibration in Rotating Shafts

The measurement of torsional vibration is a common practice in certain fields, such as the automotive industry, power generation, or large alternative engines. Similarly, functional analysis and diagnostic of other equipment, which are not traditionally measured, can benefit greatly from this type of measurement. This review discusses some techniques used in industry to measure torsional vibration, briefly describing the types of sensors used and the transduction procedures. Choosing the most appropriate technique in each case not only responds to economic reasons, but also to other conditions of the given equipment, such as its design, coupled machines or devices, functional status and operating environment, and the possibilities to install the instrumentation.     

复合式罩极电机扭转振动检测与分析

设计了一种复合式罩极电机,为双定子双转子结构,电机运行时定子绕组施加励磁,产生的旋转磁场带动转子旋转。分析了电机气隙磁场的特性,推导了电磁转矩公式,表明电机运行时存在扭转振动。研制了复合式罩极电机样机,利用传感器对电机在不同励磁状态下的转矩输出进行了检测,表明电机运行时存在扭转振动,且扭振幅值随两相励磁电压的相位差而变化,最后对变化规律进行了理论分析,结果表明:扭转振动波的相位差为两相励磁电压相位差的2倍。     

Study on Forced Torsional Vibration of CFRP Drive-Line System with Internal Damping

The use of CFRP transmission shaft has positive effect on the weight and flexural vibration reduction of drive-line system. However, the application of CFRP transmission shaft will greatly reduce the torsional stiffness of the drive-line, and may cause strong transient torsional vibration. Which will seriously affect the performance of CFRP drive-line. In this study, the forced torsional vibration of the CFRP drive-line system is carried out using the lumped parameter model. In addition, the effect of rotary inertia, internal damping, coupling due to the composite laminate, and excitation torque are incorporated in the modified transfer matrix model (TMM). Then, the modified TMM is used to predict the torsional frequency and forced torsional vibration of a CFRP drive-line with three-segment drive shafts. The results of modified TMM shown that the rotational speed difference of the CFRP transmission shaft segment is much larger than metal transmission shaft segment under excitation torque. And compared the results from finite element simulation, modified TMM and torsional vibration experiment respectively, and it has shown that the modified TMM can accurately predict forced torsional vibration behaviors of the CFRP drive-line system.     

基于扭振分析方法的齿轮传动系统故障辨识

通过分析齿轮啮合过程的数学模型及典型故障,论证了扭振分析方法在齿轮系统故障诊断上的优越性,并提出一种测量齿轮轴上扭振信息的新方法。在此基础上搭建了齿轮传动系统,通过采用永磁旋转(角)加速度传感器检测齿轮系统各个运行状态下不同轴上的扭振信号;然后,分别对齿轮传动系统轴上的扭振信号和平台的振动信号采用小波包分解,提取各个节点的能量作为特征向量;最后,结合以径向基函数(RBF)为核函数的支持向量机(SVM)分别进行故障的辨识。实验结果表明:轴上的扭振信号在齿轮系统故障诊断上的效果要优于平台振动信号的诊断效果。     

Torsional Oscillator measurements of multiply connected monolayer 4He films under high speed rotation up to 4.0 rev./s

No Heading We are studying the physical phenomena of superfluid thin films adsorbed on multiply connected surface of porous glasses under high speed rotation. The combination of thin superfluid ⁴He films on large pore porous surfaces and high-speed rotation gives rise to a new quantum vortex excitation, where vortex lines are pinned on the center of pores and have the core at the pore. This excitation has been predicted and named as a pore vortex. We are trying to measure the behavior of pore vortices using the Torsional Oscillator (TO) technique and we have succeeded in making measurements up to the high-speed rotation of 4.0 rev./s. Here we report the actual design of the TO set up.PACS numbers: 67.40.Vs, 67.57.Fg, 67.70+n, 67.40.Rp.     

瓦楞机系统的扭转振动特性研究

利用传递矩阵建模方法,建立了瓦楞机系统扭转振动的动力学模型,进行了动力学方程求解,得到了系统扭转振动的固有频率和圆频率.     

船舶轴系扭振计算中几个公式的修正

对船舶轴系扭振计算中最为主要的公式，平均指示压力、气体力所产生的干扰力矩、外阻尼等进行探讨和修正，经过实例计算与实际测量证明，完善了船舶轴系扭振计算，提高扭振计算的精度。其中，平均指示压力是计算简谐系数时的惟一参数，气体力所产生的干扰力矩是影响合成简谐系数计算的重要影响因素，外阻尼是计算动力放大系数的主要参数。