Search results

When components made of different materials are combined to make anything mechanical, consideration must be given to the fact that they will not have the same thermal behaviour. Taper roller bearings mounted in light alloy housings provide an example of such a temperature‐sensitive arrangement. Depending on the difference in thermal elongation, large variations in bearing internal clearance can be obtained, and this can have an appreciable effect on the life of the bearings. The adjustment of the bearings on mounting must therefore be carefully determined. A passenger car gearbox with a light alloy casing where the intermediate shaft is supported in two taper roller bearings is studied. When selecting a suitable adjustment, the resilience of the casing must also be taken into account.

The purpose of this paper is to investigate the process of jamming of the hollow parts on the shaft and to derive a mathematical model for jamming in an assembly process.

The mathematical model for jamming of parts on the shaft in an assembly process is based on the sizes, geometry, angular declination of part and shaft axes, and the frictional factor.

The equation for angular positional tolerance of coaxial parts and shafts, based on their geometry and sizes and leading to jamming, was derived.

A mathematical model of parts jamming on the shaft is developed for assembly mechanisms. This research does not consider flexible deformations of components in assembly mechanisms, which results in the axis concentricity of part and shaft in the assembly process.

The results presented in the form of angular positional tolerance for coaxial parts and shafts based on their geometry and sizes make it possible to avoid the jamming of the parts. The results allow for formulating the angular positional tolerance of the assembly mechanisms that clamp the parts.

The proposed method for calculating the angular positional tolerance of coaxial parts and shafts for the assembly process should allow for increasing the reliability of the assembly process in the manufacturing industry.

A fiber Bragg grating (FBG) sensor was designed to measure the door gap of automobile bodies.

The gap sensor was designed through a combination of the sliding wedge and cantilever beam, involving a magnetic force installation and arc structure of the force transmission point. Moreover, the sliding block adopted an anti-magnetic and wear-resistant material and the temperature compensation of the two FBGs was conducted. The magnetic force and contact stress of the sensor were examined to ensure that the sensor exhibited a certain magnetic attraction force and fatigue life. The performance of the gap sensor was examined experimentally.

The sensor could measure gaps with dimensions of 5 mm to 11 mm, with a sensitivity and measurement accuracy of 150.9 pm/mm and 0.0063% F.S., respectively. Moreover, the sensor exhibited a small gap sensitivity, with a repeatability error of 0.15%, anti-creep properties and magnetic interference abilities.

The sensor is compact and easy to install, as well as use for multiple sensor locations, with a maximum size of 43 mm, a mass of 26 g and installation type of magnetic suction. It can be used for high-precision static and dynamic measurements of the door inner clearance with a resolution of 0.013 mm to improve the efficiency of internal clearance on-line analysis and assembly quality inspection.

Many power generation steam turbine generators today are required in service well beyond their intended lifetimes. Dismantling for inspection is expensive, and owners need to consider all relevant information in making the decision. Application of condition monitoring in all the applicable methods is justified, with each showing different degradation modes. Performance analysis is less well publicised, yet unlike vibration analysis and oil debris analysis, it will show conditions which reduce machine efficiency and output, such as deposits on blades and erosion of internal clearances. Data obtained from tests before and after overhaul also reveal whether any restorative work achieved the expected improvements in performance. The paper outlines, with examples, some condition monitoring techniques that have contributed to retaining some large fossil machines in service for up to 17 years without opening high‐pressure sections.

AS air is a compressible fluid, a decrease of pressure occurs with increase of altitude (FIG. 1.) This change gives rise to anoxia or altitude sickness (due to lack of oxygen), expansion of the gas in ear or abdomen and ‘bends’ or decompression sickness. For these reasons (and also because of the low temperature and humidity) it is necessary to protect passengers intending to fly at high altitudes by placing them in a special cabin in which a suitable pressurized atmosphere can be maintained.

Most chemical pumps on the market today were designed 20 to 30 years ago, in the days of shaft sealing by gland packing. Their characteristics include small diameter shafts, with the packing acting as a third bearing to support the overhang; high pressure in the seal chamber; and excessive shaft end‐play.

The aim of this paper is to present a theoretical model to simulate the dynamic behavior of a spur gear, taking into account its ball bearings defects.

The proposed model is based on the implicit Newmark‐β with Newton‐Raphson numerical integration technique in order to analyze the impact of the worn bearings on the non linear dynamic behavior of one stage spur gear transmission system.

The dynamic behavior of spur gear is studied taking into account ball bearings defects thanks to the proposed model.

A new numerical model is proposed to simulate the dynamic behavior of rotating spur gear system taking into account both waviness and backlash defects.

SERVICING, at specified intervals, is essential to the safe and reliable running of all mechanical devices. This is, perhaps, even more important in the case of the jet engine than with other mechanisms. With this object in view, the following paragraphs outline the servicing requirements of the Derwent jet propulsion power unit.

This work aims to compare the vibration behavior of roller and ball bearings operating with clean and quartz‐contaminated lubricants. Wear influence on vibration of both bearing types was also compared.

Experimental tests were run in clean and contaminated mineral oil. Contaminant quartz particles of 59 μm average size were tested in three concentration levels: 0.05, 0.25 and 0.5 g/l. Radial vibration of the roller bearing was measured by accelerometer and wear was analyzed through microscopy of the surfaces and optical spectrometry of oils.

Differences in vibration response among both bearing types were observed regarding the root mean square value of vibration data in the high frequency band (600‐10,000 Hz); differences in wear influence on vibration were also identified and correlated to the differences in the tribological features.

This paper presents a methodology for detecting contamination and wear of roller bearings by applying a simple procedure of vibration monitoring and analysis.