Characteristics of a new plastic track detector of the CZ type

The registration parameters of a new plastic track detector (PTD) for nuclear particles have been experimentally investigated. The PTD is a modification of a CR-39 detector and is labeled CZ. As compared to the CR-39 detector with a similar chemical composition, the CZ PTD produced by the Semenov Institute of Chemical Physics from allyl diglycol carbonate (C₁₂H₁₈O₇) has a considerably higher sensitivity and better dynamical (the track etching rate and the rate of etch removal of a substance from the surface of a PTD plate) and geometrical (etchable track length and diameter) registration parameters. Based on results of the calibration experiments with α particles of different energies, fission fragments of ²⁵²Cf, and accelerated ²⁰Ne ions, the theoretical estimate was obtained for the threshold value of the specific ionization losses, the sensitivity, and the detection efficiency for nuclear particles, beginning with protons.     

Isolation and identification of dry bearing faults in induction machine using wavelet transform

Any vibration signal obtained from electromechanical systems contains a level of random changes. These random changes in the measured signal may be due to the random vibrations that can be related to the health of the machine for some faults such as dry bearing fault or bearing ageing. The presence of dry bearing fault, which is caused by the lack of lubricant, increases the level of random vibrations as compared to those obtained in healthy bearing machine. If these random vibrations could be isolated from the measured signal, useful information about bearing health may be obtained. Therefore, in this paper, signals (three line to line voltages, three currents, two vibration signals, four temperatures and one speed signal) obtained from the monitoring system are treated and analyzed using wavelet transform to correlate it to the dry bearing faults in induction machine. In this study, on-line analysis of the acquired signals has been performed using C⁺⁺, while MATLAB has been used to perform the off-line analysis.     

A light-emitting diode monitoring system of the PHOS photon spectrometer in the ALICE experiment on the large hadron collider

A light-emitting diode (LED) monitoring system of the PHOS photon spectrometer in the ALICE experiment on the CERN large hadron collider is described. The spectrometer includes three modules in the form of 64 × 56 matrices consisting of plumbum tungstate (PWO) crystals. As test light signal sources, Kingbright L934SCC superbright green light-emitting diodes with an individual instrumental regulation of light flash intensities in each channel of the spectrometer are used. The system ensures adjustment and monitoring of the electronics at the stage of preparing for the physical trigger of the PHOS modules and is intended to perform special test measurements with the spectrometer without using high-energy particles. In addition, in the course of the experiment, it allows one to promptly monitor each channel of the spectrometer and keep track of temperature variations of the light yield of the PWO crystals. In this case, the long-term relative channel monitoring stability is ensured at a 1.2 × 10⁻³ level.     

Influence of a tension stress field introduced in the elastohydrodynamic contact zone on rolling contact fatigue

The rolling contact fatigue life of modified NU 209 roller bearing inner races subjected to tensile stress mechanically induced in the contact zone, has been investigated using the four-contact fatigue machine.A high tensile stress of 80 MN/m² by a clamp pressure, acting on the inner surface of the specimen, has a catastrophic effect on fatigue life; all specimens burst earlier than pitting failure would have occurred at a near zero tensile stress level.A theoretical study of the influence of the axi-symmetrical stress field, induced by the steady pressure applied inside the hollow rotating cylinder on the stress distribution in the e.h.d. contact zone of cylinders showed a significant increase of the resultant shear stresses caused by tension. The pure shear stress state may exist in the contact zone when the tensile stress level is high.     

Improvement of the seizure resistance of orifice-type aerostatic bearings (case study)

In this case study, professional equipment installed at several different sites was suffering from recurring seizure of the aerostatic thrust bearings of a linear motor, causing unacceptable downtime and production losses. It was necessary to find a rapid and cost-effective solution that could be applied to equipment already installed in the field, as well as an optimum design solution for new equipment. Analysis of the field failures indicated that failure was due to either the magnetic attraction and trapping of contaminant particles between the thrust pads and bearing track surfaces, initiating adhesive wear and material transfer, or to (temporary) air supply failures or overloading, resulting in contact between the bearing surfaces. The pre-selection of potential solutions to the problem was aimed at reducing both the particle contamination and the tendency for adhesive wear behaviour. Pin-on-disk tests were carried out in order to rapidly identify potential solutions. These tests were followed by actual-scale system tests simulating the crashing of air bearings and the influence of contaminant particles introduced into the bearing gap.The most favourable results in terms of performance and costs were achieved by applying a thermo-chemical carbon diffusion surface treatment (Kolsterising^®) to thrust bearings made of austenitic stainless steel, and applying a pulse plasma nitriding treatment to the bearing track material. This was chosen as the preferred solution for new equipment design. For equipment already installed in the field, a satisfactory solution was provided by replacing the existing thrust pads with pads equipped with partially stabilised zirconia (PSZ) plates on the bearing surfaces.     

Non-linear oil film response model for the dynamically misaligned sterntube bearing

This paper presents a non-linear oil film response model which has been developed from a model for the aligned full circumferential groove bearing, described earlier by Jakeman¹. The model is specifically intended to represent the dynamically misaligned sterntube bearing, for the purpose of conducting lateral vibration analysies of marine propeller shafting. Some predicted data are presented for the oil film response to lateral and angular motion of the journal axis, upon which the non-linear model is based. A comparison of lateral vibration predictions using the non-linear and linear oil film models, and measurements by Hyakutake et al², will be given in a separate paper.     

Alpha-particle spectrometry using position-sensitive solid-state track detectors

A precision technique for measuring the angular distribution of differential cross sections for elastic scattering of charged particles using position-sensitive solid-state track detectors has been developed. The technique is based on the freedom of choice of the angle pitch under the condition of the minimum angular resolution of the spectrometric system, which is determined by the geometry of the experimental setup. The differential cross sections in the reaction ²⁷Al(α, α)²⁷Al have been measured at an α particle energy of 5.5 MeV.     

A monitor for heavy ion flux density control based on detection of recoil protons during irradiation of polymer films

An monitor for control of accelerated particle flux density used in irradiation of polymer films with heavy ions with a low track density (10³?5 × 10⁷ cm^?2) is based on detection of recoil protons. It has been designed to control irradiation of a film with a width of up to 650 mm and is composed of five PIN diodes with a hydrogenous target placed in front of each diode. The sensitivity of the monitor with a polyethylene target to the density of a xenon ion beam is described by a linear function; its value is (4.0±0.5) × 10^?3 pulses/(ion/cm²). The instrument is capable of monitoring ion flux densities of <10⁶ cm^?2, for which all other methods are ineffective. It can be used to determine the track density in a finished product, bypassing the stage of a check with an electron microscope. The signals from the monitor can also be used to introduce a feedback in a system of automatic beam tuning in order to improve the film irradiation quality. The radiation hardness of silicon detectors is ≈ 10¹² protons/cm². At an average detector load of ≈ 10⁴ protons/cm², the average service life of the monitor is 10⁸ s of continuous operation.     

Study of Flow Characteristics of Lubricant in Spiral-Groove Bearings by the Fluorescent Method

Abstract

The hard disk drive spindle is one of the critical mechanical components in hard disk drives (HDDs). It has great influence on overall performance, including track density, data-transfer rate, energy consumption, noise, and so forth. Nowadays, HDDs with higher density and speed, larger capacity, and smaller size are under active development. This requires that HDD spindles have fast rotating speed, excellent accuracy, and small size. However, ball-bearing spindles, which are widely used in current HDDs, cannot meet these requirements. HDD spindles supported by oil-lubricated spiral-groove bearings are considered to be a candidate to replace ball-bearing spindles. There is no oil-supply device in the bearing, and the flow characteristics of the lubricant in the bearing have a great effect on the performance of the spindle.

In this article, the fluorescent method is used to study the flow characteristics of the lubricant in a spiral-groove bearing. The establishment and recovery of the lubricant film during start/stop of the spindle are observed. The effects of working conditions on the thickness and distribution of the lubricant film are investigated. The influence of oil supply on the performance of the bearing is also studied.     

Starvation and Reflow in a Grease-Lubricated Elastohydrodynamic Contact

The lubrication mechanisms of a grease in a rolling-element bearing has been studied through the measurement of film thickness in a rolling point contact. To simulate bearing conditions the contact runs under fully starved conditions; there is no attempt to maintain bulk flow of the grease into the inlet using an external supply. In consequence the film thickness drops off rapidly as the contact progressively starves. After a few minutes rolling (at constant speed) an equilibrium film thickness is attained which has two components: a residual film (h_R) comprised of degraded grease thickener and a hydrodynamic component (h_EHD) due to the liquid phase from the grease. The hydrodynamic contribution represents a balance between lubricant lost from the contact and replenishment from the grease close to the track. The ability of the grease to replenish the rolling track has been inferred from measurements of lubricant reflow around the static contact. These results are discussed in light of current starvation and grease lubrication models.     

Parametric study of solid-lubricant composites as ball-bearing cages

The performance of two polymer-based materials (polyimide/MoS₂ and ptfe/ glass fibre/MoS₂) as self-lubricating cages for ball bearings has been comprehensively evaluated. The two composites emerged as the most promising for operating at elevated temperatures during screening tests in a thrust-bearing geometry and were then tested in four sizes of 440C stainless steel single-row radial ball bearings at a range of loads, speeds and temperatures.Two regimes of operation were observed: the first with essentially zero steel wear when the lubricant transfer film is complete and bearing life is dictated by cage wear; the second with finite steel wear when the transfer film is only partially effective and bearing life is dictated by increase in internal clearance. The ball/raceway stress at which steel wear starts to occur is very low (< 1.2 × 10³ MN m^?2) compared to the stress implied by the catalogue load capacity of the bearings. The ball/raceway stress also has an important effect on both steel wear rate and cage wear rate.Overall, the ptfe-based composite gave lower steel and cage wear than did the polyimide-based composite, but the latter could be operated at higher temperatures (up to 360° C) and at slow speeds it gave a higher load capacity before the onset of steel wear.Using the wear results as a basis, a Bearing Performance Guide has been produced which provides a convenient means of approximately predicting the bearing life over a wide range of operating conditions     

Isotherm mapping in the bushes of high speed journal bearings

A high speed journal bearing rig has been designed to study thermal effects in bearings operating in turbulent regions. The apparatus consisted of a journal of diameter 7.62 cm with a diametrical clearance of 0.256 mm rotated over a speed range of 20 000 – 55 000 rev min^?1 for a load range of 1100 – 6600 N. Sixty Ni-Cr/Ni-Al thermocouples of diameter 0.5 mm embedded in the bush of the test bearing enabled lines of constant temperature to be plotted over the surface of the bush. Particular studies were made of the influence of carry-over oil and bearing misalignment.     

Appearance of craters on track surface of rolling element bearings by spark erosion

A theoretical investigation has been carried out to determine the time span for the appearance of craters by spark erosion on the track surfaces of rolling-element bearings operating under the influence of shaft voltages. An analytical model has been developed using the continuum theory of Griffith to determine energy per unit area required for the development of craters on the track surfaces. Also, an expression is deduced for the net energy transmitted per unit area on the track surfaces by the leakage of stored charge energy resulting in the appearance of craters under the effect of shaft voltage and bearing capacitance depending on operational and dimensional parameters of a bearing in a given span of operation. By the formulation of capacitive stored energy in a bearing using high resitivity lubricant, along with the developed model and expressions using the ratio of cycles to accumulate and discharge of the accumulated charge energy at the various levels of bearing to shaft voltage, the time span/cycles for the appearance of craters of specified dimensions by spark erosion has been determined. Matching time span/cycles has been ascertained by the investigation of a case history of the diagnosis of bearings that failed by crater formation. The analysis can also be used for determination of shaft voltage if the time span/cycles for the formation of known size craters and bearing capacitance are established.     

On calculation of contact temperatures arising at rotation of ball in spherical bearing

The heat conduction problem for a spherical bearing with a spherical insert is considered. The constant coefficient κ ₁ ^′ from the formula of the average ball temperature in the contact region has been determined.     

An investigation into the generation of corrugation by transient spin creep

It has been suggested that short wavelength corrugation of railway track may arise from a mechanism in which the fluctuating spin moment normal to the contact patch preferentially wears some wavelengths of an initially aperiodic roughness on the rail. This hypothesis has been investigated in the laboratory in a rolling contact disc machine. After running for a total of 7 × 10⁶ cycles the experimental discs were worn to a uniform roughness throughout the appropriate wavenumber range. We therefore believe that it is unlikely that the proposed mechanism is sufficiently selective to produce corrugation. Corrugations of a longer wavelength were produced by a wear mechanism involving the dynamics of the disc machine.     

Effect of Oxide Film on the Friction of 52100 Steel in Vacuum

To solve the anomalous behaviors of friction coefficient in reciprocated slidings of 52100 steel in ultrahigh vacuum, studies were made if the wear track, friction level, and number of traverses for a 52100 steel test ball sliding on a 52100 steel flat over a pressure range of 760 to 3 × 10^?9 torr. Plots of the friction coefficient versus number of traverses show a maximum (f = 1.0–1.2) followed by a drop (f = 0.5–0.6). Both the friction force-time curves and microscopic friction area change from smooth to rough at the point of the drop in friction coefficient. The shape of the friction plot is ascribed to a build-up and rupture of the oxide film that forms on the surface of the 52100 steel specimen in atmosphere and is affected by applied load, direction of finishing marks and pressure level of the environment. Further, above a critical pressure of 10^?6 torr the drop was not experienced. It was also found that higher friction does not always mean that the sliding surfaces are clear or more oxide-free.     

Magnetic Flux Density Distribution on the Track Surface of Rolling-Element Bearings–-An Experimental and Theoretical Investigation

This paper brings out the theoretical model to determine the developed magnetic flux density on the track surfaces of inner race, outer race and rolling elements of a rolling-element hearing operated under the influence of electric current. The flux density, analytically determined, is compared with that of the flux density developed on the track surface of races and rolling elements of the bearings tested on the bearing test-up under the influence of electric current. Also, the residual magnetic flux density on the damaged bearings of motors and alternators has been measured and the theoretical model is used to determine the amount of current flow through the damaged bearings. The current flow through the bearings, thus established, has been compared with that of the current evaluated by the measurement of shaft voltage and bearing resistance.     

Quantitative aspects of the wear of melamine laminates

The wear behavior of high pressure decorative laminates has been quantitatively investigated by placing a stationary, metal ball rider against the flat surface of a rotating disc of melamine resin reinforced with α-cellulose fibers. The factors most influencing the wear were the load, the humidity, and the nature of the specimen, i.e. reinforced or unreinforced, fully cured or undercured. It was found that the width of the wear track T was related to the number of thousands of revolutions of the disc L by the equation T = ALⁿ where A and n are constant for a given experiment. The equation enables the wearlifetime of a laminate to be established from a few experimental measurements.     

Process compensation and printed circuit board manufacture

The analysis of the current method of transferring data between the designer and the manufacturer of printed circuit boards has suggested that the use of a manufacturing workstation in the manufacturing process can result in the production of higher quality circuit boards. In order to transmit the design between the workstation and the production database, a neutral format is suggested. The various production processes change the physical and electrical properties of the boards, use of the neutral format allows the manufacturer to take into account the idiosyncrasies of his production line and produce boards to a higher standard. By using a generic representation of the machine languages used to drive the tools (along with the neutral format), the manufacturer should be able to add new machines to the production line quickly and easily.Nomenclature Symbol Value Units Meaning - C F capacitance between two tracks - l m length of a track - h m height of a general track - H 2.7×10^–6 m height of a track. This is equal to the amount of copper plate on the board - t m distance between two tracks - dC F capacitance of a thin strip of the track - k None gradient of the line used as an approximation to the true shape of the track - t _o m distance between the two tracks at the base of the tracks after etching - dh m height of a thin strip of the copper track - R resistance of a track - m resistivity of the copper used to make the track - w m width of a track - w _b m width of a track at the base - w _t m width of a track at the top - ₀ 8.85×10^–12 F m^–1 permittivity of free space - _t 1.0005 None relative permittivity of air     

Development of CdO-graphite-Ag coatings for gas bearings to 427 °C

A CdO-graphite coating was developed and successfully tested in foil air bearings for long periods up to a temperature of 427 °C (800 °F) and at a normal contacting load (during starting and stopping) of 14 kPa (2 lbf in^?2) based on the bearing projected area. The addition of ultrafine silver to the CdO-graphite improved the coating endurance. At 427 °C, the CdO-graphite-Ag coating performed better than CdO-graphite without silver, both for extended periods at 14 kPa (2 Ibf in^?2) and for limited periods at 35 kPa (5 lbf in^?2). At 288 °C (550 °F), the coating was tested for an extended period up to 28 kPa (4 Ibf in^?2) and has also successfully completed high speed shock tests to an acceleration level of 100g.