摘要:

AbstractWith the increasing use of frequency converters as control units for electric motors, bearing failures caused by the passage of electric current through the bearings are more common. This paper discusses the most relevant parasitic current loops in frequency converter‐driven motors that can lead to damage of bearing raceways or deterioration of lubricants. Electrical stray capacitances, which are inevitably present in any electric motor, in combination with the high‐frequency components of the drive voltages, have been identified as the source of electric discharge machining (EDM) currents. Based on an EDM equivalent electric circuit, the passage of electric current through the rolling contact of a bearing is simulated. A set‐up is introduced to initiate EDM processes in bearings under well‐controlled electrical and mechanical conditions. The effect of EDM currents on bearing elements in the presence of different lubricants is studied. Initial results are pr

ISSN:1354-4063    

DOI:10.1002/tt.3020110402

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractInternal combustion engines are still of major importance as propulsion systems. To fulfil future market and legislative demands it is necessary to improve engine performance, reduce fuel consumption, and limit exhaust emissions. Mechanical and thermodynamic losses, wear, and the emissions caused by lubricating oil combustion are principally influenced by the tribological behaviour of the piston assembly. The trend towards compact engines with high power densities and increased thermomechanical loads increases the importance of this tribological system and requires new approaches. One promising possibility is the utilisation of liner surfaces with specially machined microstructures. This paper describes a comparison between a conventional liner surface and a laser‐structured liner as regards their tribological behaviour. Measurements of wear as well as of oil film thickness and friction force in operation have been carried out. The results show better tribological behaviour for the laser‐structured liner surface than for the conventional plateau‐honed surface. This leads to lower fuel consumption and less

ISSN:1354-4063    

DOI:10.1002/tt.3020110403

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractWear in modern mechanical systems is characterised by ultra‐low wear rates in the range of a few nanometres per hour. The surfaces of the materials involved, as well as their volumes, experience modifications as regards morphology, crystalline arrangement, and chemical bonds. The depth of the tribological interactions under given conditions extends to a micrometre or less. To probe these thin modified zones, synchrotron‐based X‐ray diffraction and nano‐indentation were applied. The specimens were taken from tribometer experiments employing the radionuclide technique to measure ultra‐low wear rates. To obtain different degrees of tribological interaction, various loads and sliding velocities were applied. The specimens were subdivided according to the total power dissipated during the tribometer e

ISSN:1354-4063    

DOI:10.1002/tt.3020110404

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractMost mechanical components used for transmission of movement are subjected to repeated impacts or cyclic stress. If these elements are well designed and the materials well chosen, their durability is linked to surface fatigue mechanisms. In order to improve the fatigue behaviour of these parts, hard coatings, such as physical vapour deposition (PVD) or plasma‐assisted chemical vapour deposition (PACVD) coatings, can be appropriate. Unfortunately, such hard coatings cannot be used for elements whose replacement is more difficult than, say, cutting tools. An understanding of failure mechanisms should make it possible to optimise the fatigue behaviour of hard coatings.In order to study the surface fatigue behaviour of thin, hard PVD coatings, a special apparatus has been developed to carry out repeated impacts over a broad range of speeds. The possibility of mapping the fatigue behaviour of different coatings is illustrated through the examples of TiN and TiN/CrN multilayer coatings of different thicknesses deposited on several substrate

ISSN:1354-4063    

DOI:10.1002/tt.3020110405

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractMagnetic fluid rotary vacuum seals have been shown to be effective in machinery operating in a vacuum chamber. Such seals have the advantages of simple design, zero leakage at almost any rotation speed, and low friction. They have no wear and require no maintenance. This paper presents results obtained from experimental investigations of the operation of magnetic fluid rotary seals under vacuum conditions. The paper discusses the test apparatus and the seals used, the test conditions, and the procedure. The experimental results show characteristic phenomena observed in magnetic fluid rotary vacuum seals, including changes in vacuum pressure, temperature, and frictional moment dependent on the rotation speed of the shaft, number of sealing stages, height of the sealing gap, and mean magnetic flux density in the sealing gap.

ISSN:1354-4063    

DOI:10.1002/tt.3020110406

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractData published by the Institute of Materials including information on the volatility, sulphur content, and sulphur volatility of 913 engine oils were compiled. These engine oils were collected in three geographic regions: North America, Europe, and Asia. The volatility data were generated using a Selby—Noack instrument in which all volatilised material is collected for the further analysis of phosphorus and sulphur content. It was found that under the normal Noack test exposure conditions of 250°C for one hour, the sulphur emission index (a measure of sulphur volatility in mg/l) varied markedly among the engine oils. In a correlation study, a minor correlation of up to %R2= 15 was found between sulphur volatility and oil volatility while a greater correlation of up to %R2= 39 was found between sulphur volatility and sulphur content of the formulated engine oils. A new concept and application of the sulphur volatility ratio may be useful in explaining the observations concerning sulphur volatility dependen

ISSN:1354-4063    

DOI:10.1002/tt.3020110407

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

ISSN:1354-4063    

DOI:10.1002/tt.3020110408

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

ISSN:1354-4063    

DOI:10.1002/tt.3020110409

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

ISSN:1354-4063    

DOI:10.1002/tt.3020110401

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY