摘要:

AbstractA method for the tribological assessment of lubricants under conditions of scuffing is presented. The method uses a four‐ball tester, and allows one to assess the effect of lubricant on scuffing intensity through an analysis of changes in the friction torque and wear of the stationary balls, at continuously increasing load. The behaviour of a lubricant under scuffing conditions can be characterised using the so‐called limiting pressure of seizure poz, which depends on the load at which the balls seize and the average value of the wear area calculated from the wear‐scar diameters measured on the stationary balls.A comparison is made ‐ from the point of view of the resolution, time consumption, and cost ‐ of the new method with the existing, standard tests, using a four‐ball tester and a gear test rig (FZG). It is concluded that the proposed method, unlike standard FZG and certain four‐ball tests, enables one to differentiate between gear oils, in agreement with their API GL performance level. The very short run‐time of the new method enables one to perform more tests and obtain a low standard deviation. The new method is much cheaper than the standard four‐bal

ISSN:1354-4063    

DOI:10.1002/tt.3020080402

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractIn the design and evaluation of mechanical system performance it is important to know the frictional qualities of the lubricant. Without correct numerical treatment of the lubricant during simulations of large systems, e.g., drive trains in trucks and buses, the results will, to a large extent, be inaccurate. However, obtaining detailed information places demands on the test equipment as the events are both transient and highly loaded. Under quasi‐static conditions, forces are measured with force transducers, but in elasto‐hydrodynamically lubricated conjunctions, where pressures are so high that the surrounding surfaces deform elastically, this cannot be done without permanently damaging the equipment. The conceptual design of the test equipment must therefore incorporate the measuring process in transient conditions (loading‐unloading times of 200–500 μs) being performed in real time, and allow extreme pressures of up to 3 GPa without component destruction.One way to obtain accurate friction data successfully is to apply a concentrated force pulse to a non‐instrumented surface and to measure the response from that pulse elsewhere. The development of a measurement technique, the Lulea ball and bar apparatus, which utilises wave propagation theory, is presented in this paper. An oblique impact on a robust end plate on a rod was used to generate both non‐dispersive compression waves and dispersive flexural waves. The normal force created by the axial wave was measured using strain gauges, while the transverse force was derived from the fast Fourier transforms of two lateral acceleration histories, using dynamic beam theory. The relation between the normal and tangential force histories showed the frictional properties at the impact as a function of time. A variety of lubricants was also studied at Hertzian pressures of up to 2.5 GPa, and the development of the method and results are presented. Experiments indicate that different lubricants exhibit different frictional properties and that the resolution in the test equipment is sufficient to i

ISSN:1354-4063    

DOI:10.1002/tt.3020080403

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThis paper reports on friction tests of a hard lubricant coating conducted in orbit around the Moon. The measurements included those taken in terrestrial conditions in a vacuum chamber, at the launch site, and in lunar orbit. The paper includes a description of an autonomous friction simulator that was mounted outside the spacecraft. In this device, two types of friction, ‘shaft‐bush’ and ‘disc‐indenter’, have been tested. For the first time, a long experiment exploring the tribological characteristics of an antifriction coating in a real space environment in a lunar satellite orbit has been carried out. Over a fifteen‐month period, the friction units were run in the space environment. These tests indicated a tendency for the friction coefficient to reduce to a limit value in such an orbit an

ISSN:1354-4063    

DOI:10.1002/tt.3020080404

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractTo characterise the friction and wear behaviour of materials and lubricants under a variety of operating conditions, laboratory models are frequently used to provide useful information. For example, during the development and/or selection of tribomaterials and lubricants, laboratory ranking of candidate products can save many hours of field testing. A reciprocating ball‐on‐flat wear test rig has been developed to rank the performance of materials, surface coatings, and lubricants under boundary, extreme‐pressure, or fretting conditions in a variety of environments and at various temperatures. The rig design is based on ASTM G133–1995. The friction force and wear are measured on both specimens while the load, stroke length and frequency, test temperature, lubricant type, test duration, surface topography of both ball and flat specimens, specimen materials, and environmental conditions are noted.The results presented in this paper refer specifically to a series of tests performed to evaluate various anti‐fretting lubricants. Two lubricants are compared in terms of friction coefficient and wear volume over time. A clear difference is shown between the two

ISSN:1354-4063    

DOI:10.1002/tt.3020080405

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractOptical second‐harmonic generation is a recently developed technique in surface science, the range of applications of which has been steadily broadening. It allows, among other things, the direct probing of molecular adsorption on to a solid substrate from a liquid or gaseous environment. This paper reports on the possibility of applying it to tribological studies. A set of possible experiments that could offer information, in particular, on the working principle of those oil additives, commonly used in the lubricant industry, whose effect derives from surface adsorption, are discussed briefly. In addition, the preliminary results of a first experiment are describe

ISSN:1354-4063    

DOI:10.1002/tt.3020080406

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractWork is currently under way within the ASTM D.02 N.07 ‘Hydraulic Fluid Testing’ Committee to evaluate the potential of replacing the Vickers V‐104C vane pump with a newer, more current model 20VQ5 vane pump for use in an updated ASTM D 2882 standard and other national standards. All the round robin work conducted within the Committee thus far has involved the use of non‐aqueous hydraulic oils. Although there are some significant inter‐laboratory reproducibility problems, it appears that the overall ranking of these hydraulic oils by most laboratories appears to be consistent. To further evaluate the potential utility of replacing the Vickers V‐104C pump with the 20VQ5 pump, a series of different water‐glycol hydraulic fluid formulations with significantly different wear rates were evaluated using a ‘modified’ ASTM D 2882 testing procedure. The results showed that expected catastrophic pump failures, which occurred with the V‐104C pump, not only did not occur with the 20VQ5 pump, but the relative orders of wear rates for some of the fluids

ISSN:1354-4063    

DOI:10.1002/tt.3020080407

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

ISSN:1354-4063    

DOI:10.1002/tt.3020080408

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

ISSN:1354-4063    

DOI:10.1002/tt.3020080409

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

ISSN:1354-4063    

DOI:10.1002/tt.3020080401

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY