Lateral Speeds Research Articles

Low friction in a flywheel system pith passive superconducting magnetic bearings

Abstract A flppheel spstem pith superconducting magnetic bearings pas built and tested. The bearing consists of six melt-textured pBCO pellets mounted inside a continuous flop LN 2 crpostat. A disk measuring O 190 × 30 mm pas safelp rotated at speeds up to 15,000 rpm. The disk pas driven bp a high speed three-phase spnchronous homopolar motor/generator. Maximum energp capacitp pas 3.8 ph, maximum poper pas 1.5 kp. The dpnamic behavior of the prototppe pas tested, characteriped and evaluated pith respect to axial and lateral stiffness, damping, decap torpues and critical speeds. Spin-dopn experiments in a vacuum chamber pere performed to investigate the energp efficiencp of the spstem. Drag torpues pere found to depend upon the gap pidth in the bearing. At a background pressure of 4 × 10 −4 Torr and a gap pidth of 6 mm, the coefficient of friction (drag-to-lift ratio) pas measured to be 9 × 10 −6 at lop speeds. The experiments demonstrate the applicabilitp of superconducting magnetic bearings in highlp efficient, kinetic energp storage spstems.

Modeling Rotating Shafts Using Axisymmetric Solid Finite Elements with Matrix Reduction

An axisymmetric harmonic finite element representation is used to calculate shaft lateral critical speeds and perform stability analysis. Unlike a beam element model, an axisymmetric solid element representation allows the actual rotor geometry to be modeled. A Fourier series representation allows the three-dimensional shaft geometry to be modeled in two dimensions by only considering the radial and axial coordinates. Thus, the degrees of freedom of this element type are different from the usual two translations and two rotations at each node associated with bending of a three-dimensional beam element. A required gyroscopic matrix is also presented for completeness in analysis of rotating shafts. A matrix reduction technique is used to reduce the size of the shaft mass, gyroscopic, and stiffness matrices by condensing out slave degrees of freedom in terms of the retained master degrees of freedom. The formulation is applied to various examples for verification and to investigate the effect of selection of different master degrees of freedom for this element type on the results.

Viscoplastic Buckling of Silicon Ribbon

Silicon ribbon grown by the dendritic web process passes through a rapidly changing thermal profile in the growth direction. This rapidly changing profile induces stresses which cause buckling. Based on a viscoplastic material response function (Haasen-Sumino model), the creep buckling behavior of the silicon ribbon is investigated. The lateral deflection speeds describing the viscoplastic buckling behavior are calculated. It is found that the deflections of some modes increase with time while others die out. The role of the residual stresses in viscoplastic buckling is examined.

Dislocation dynamics and the viscoplastic buckling of dendritic web type silicon ribbon

The effect of dendrites (reinforced edges) on the residual stresses, dislocation densities and buckling behavior during growth of web type silicon ribbon is studied. A viscoplastic material response function (Haasen-Sumino model) is used to calculate the stresses and the disloction density at each point in the silicon ribbon. In addition, the role of dendrites on the viscoplastic buckling behavior of the ribbon is investigated. The critical thicknesses, the corresponding deflection shapes and lateral deflection speeds are calculated. These results are then compared with similar data obtained for flat plates.

The Effect of Bearing Support Flexibility on Critical Speed Prediction

Some vendors and many users of rotating machinery are arbitrarily reducing the bearing damping by as much as 75 percent in order to accurately predict the location of the first and second lateral critical speeds. This paper shows that if the bearing support flexibility is considered, accurate critical speed predictions are possible without reducing the bearing damping. The equations for the equivalent support stiffness and damping are given for a flexible support spring, mass, and damper in series with the fluid film stiffness and damping properties of a tilting-pad bearing. These equations can easily be incorporated with any synchronous response and/or stability computer program. Examples of test stand results for four production rotors are shown illustrating the accuracy of this method.

On a Mathematical Model of Maneuvering Motions of Ships in Low Speeds

A mathematical model has been already established for describing maneuvering motions of ships with relatively large advance speeds. But this model is not applicable to the motions in low speeds, though such motions are of vital importance for ships' safety in harbours. In the present report, an attempt is made to modify the above mathematical model so that it can also express maneuvering motions in low speeds.Utilizing the large-amplitude planar motion mechanism, detailed captive model tests were carried out for two tanker models and a boxtype vassel. To cover various aspects of maneuvering motions, wide combinations of longitudinal and lateral speeds and yawing velocity were employed in the tests. The test results, mainly of a tanker model, are introduced and the method is discussed to describe hydrodynamic forces in simple forms. Starting from the established mathematical model in relatively large advance speeds, some terms of the model are modified from necessity so that it can express hydrodynamic forces in wide combinations of three motions. After these efforts, a new mathematical model is summarised finally. It is needless to say that the model was led, being based on open-water characteristics of hull, propeller, rudder and interaction effects among them.

The kinematics of solar inner coronal transients

The kinematic properties of a dozen ‘loop-like’ coronal transients have been examined over the range 1.2–2.4 R⊙ from Sun center. Values and trends of transient geometry, including radial height, lateral width at maximum extent, distance from loop top to height of maximum width, and lateral width at a fixed height above the instrument occulting disk at 1.2 R⊙, are given. Radial and lateral speeds of expansion are tabulated, and range from 60–900 km s-1, and 10–500 km s-1, respectively. Flare-associated events are found to exhibit the highest speeds, and show little acceleration with height; on the other hand, eruptiveassociated events exhibit large accelerations (some in excess of 50 m s-2). This clear discrimination between flare and eruptive-associated events suggests that two different physical processes are present; it is suggested that flare-associated events result from an impulsive, localized input to the corona. On the other hand, accelerated, eruptive-associated events are subjected to appreciable net forces over radial heights of one solar radius (or more) above the solar limb. It is conjectured that the pressure gradient forces responsible for the generation of the solar wind may play an important role in accelerating these latter events.

AC Induction Motor Torsional Vibration Consideration - A Case Study

Much has been written on the application of high-speed (3600 r/min) motors to pumps and compressors relative to vibration and lateral critical speeds. A reciprocating compressor coupled to an induction motor is a complex torsional system and can present a more complex set of problems to the equipment suppliers because of the wider range of forcing frequencies present. The problems encountered on a specific application with the objective of developing guidelines to be used to avoid similar system torsional problems on the application of induction motors to reciprocating equipment are discussed.

Vehicle Lateral Placements on Urban Roads

Time-lapse photographs were taken of traffic flows on five streets of varying lane width in the Toronto region. From these photographs, time histories of lateral placements and forward speeds were obtained for each vehicle. The analysis of these data indicated that lateral placement is a function of vehicle size, lane width and lane type. It was further found that, in general, the smaller the expected variance in driver response for a given roadway, the closer to the left edge of the lane the vehicles track.

Effect of Damping on the Lateral Critical Speeds of Rotor-Bearing Systems

Rigid support lateral critical speeds along with undamped system critical speeds and mode shapes are presented for typical rotor-bearing systems. The steady-state unbalance response analysis presented shows the effect of fluid-film bearing damping on the rotor response. Experimental results show reasonably good correlation with analytical results. The investigation shows that a rational rotor-bearing system design approach can be made for high-speed rotating machinery using the analytical tools.

Closure to “Discussion of ‘Effect of Damping on the Lateral Critical Speeds of Rotor-Bearing Systems’” (1976, ASME J. Eng. Ind., 98, p. 513)

Closure to “Discussion of ‘Effect of Damping on the Lateral Critical Speeds of Rotor-Bearing Systems’” (1976, ASME J. Eng. Ind., 98, p. 513)

Lateral Vibrations and critical Speeds of an overhanged Shaft

Lateral Vibrations and critical Speeds of an overhanged Shaft