摘要:

Performance analysis of a piston ring pack is presented in this investigation with the objective of studying the behavior and interrelationships of key engine parameters such as oil consumption, blow-by/blow-back, power loss and wear loads for typical operating conditions. The analysis is based on an integrated methodology addressing the various physical phenomena associated with ring packs including (a) ring dynamics for axial and twist motions within the grooves to determine flow paths for gases, (b) inter-ring gas dynamics for blow-by and blow-back behavior, (c) mixed lubrication at the ring face-liner conjunction for friction considerations and radial ring dynamics, and (d) oil transport for distribution of lubricant along the liner. Relevant output from each of these phenomenological models such as instantaneous values of (i) inter-ring flow areas, (ii) gas blow-back, (Hi) volume of oil within inter-ring regions, (iv) oil accumulation at top ring's leading edge and (v) liner oil film distribution are utilized by the oil consumption models which enable the calculations from the various consumption mechanisms (due to throw-off, entrainment and evaporation). Additionally, wear loads on the ring faces and liner are calculated based on contact pressures due to mixed lubrication at the ring face-liner interface. Included in this investigation are results from a series of studies undertaken to analyze the behavior of the aforementioned engine parameters over a range of speed and load conditions.Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in Orlando, Florida, October 11–13, 1999

ISSN:1040-2004    

DOI:10.1080/10402000008982325

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Experiments were conducted to evaluate effects of an iron fluoride (FeF2) layer on the self-lubrication and durability of the modified 25-mm-bore ball bearings made of SUS 440C. The modified bearings had a single outer land-guided, glass cloth-reinforced polytetrafluoroethylene (PTFE) retainers with elliptical ball-pockets. An FeF2layer was chemically formed by means of a passivating surface treatment of fluoridation. The untreated and fluorine-passivated bearings were tested in liquid oxygen (LO2), liquid nitrogen (LN2) or liquid hydrogen (LH2) at a speed of 50,000 rpm with thrust loads up to 2740 N for total operation times up to 11.7 hours. Under sufficient cooling conditions, the untreated bearing tested in LO2, as well as the fluorine-passivated bearing tested in LN2, exhibited excellent self-lubrication and durability, demonstrating sound surface conditions with hardly any wear. The fluorine-passivated bearing tested in LO2showed a reduction in self-lubrication. In contrast, even under poor cooling conditions in LH2, the fluorine-passivated bearing was superior to that of the untreated bearing which showed signs of seizure. Wear conditions were also evaluated based on X-ray photoelectron spectroscopic (XPS) analysis of transfer films.Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference In Orlando, Florida, October 11–13, 1999

ISSN:1040-2004    

DOI:10.1080/10402000008982326

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Electrochemical kinetic techniques are widely used for studying redox processes in aqueous solutions and in recent years have begun to be applied in non-polar solvents. This paper describes the application of such techniques to investigate lubricant additive reactions in solution in lubricating oils. The main practical difficulty is the low electrical conductivity of most liquid lubricants. A number of different approaches have been employed to try to overcome this problem, including the use of microelectrodes, of supporting electrolytes to enhance the conductivity of lubricants, and also the use of a scanning tunneling microscope (STM) system, with a Pt-Ir STM tip as the working electrode separated by nanometer scale gaps from a Pt substrate as reference-counter electrode.Presented at the 53rd Annual Meeting In Detroit, Michigan May 17–21, 1998

ISSN:1040-2004    

DOI:10.1080/10402000008982327

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The purpose of this paper is to describe the modern understanding of the contact fatigue phenomenon which occurs in different materials under various loading conditions. Part I presents experimental and theoretical knowledge of the influence of normal and factional contact and residual stresses on contact fatigue. It analyzes relationships between contact fatigue and material defects, inclusions, and lubricant contamination. Furthermore, it discusses crack initiation and crack propagation, the effect of material microstructure on contact fatigue life as well as some theoretical results for surface and subsurface cracks. Part II is devoted to reviewing the existing mathematical models of fatigue life for bearings and gears and to describing a new statistical model of contact fatigue based on contact and fracture mechanics. This new model is based on the assumptions derived from the analysis of the data presented in Part I.Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference In Orlando, Florida, October 11–13, 1999

ISSN:1040-2004    

DOI:10.1080/10402000008982328

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Stress concentration due to debris denting in EHL contacts has been analyzed. Quantitative relationships between the geometry of surface indentation, contact load and the maximum stress and its location have been established. Based on these relationships and the Weibull weakest-link theory, a fatigue life reduction model is proposed. Parametric study shows that life reduction is primarily determined by dent slope and life reduction factor decreases as dent slope increases. Indentation area-density is another major factor that affects contact fatigue life. Life reduction factor decreases as dent area-density increases. Life reduction is also affected by contact load. While fatigue life decreases with increasing load, life reduction factor increases as load increases.Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in Orlando, Florida, October 11–13, 1999

ISSN:1040-2004    

DOI:10.1080/10402000008982329

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The concept of pore ensemble is applied to piston ring lubrication. The solution of the two-dimensional Reynolds equation is given for reciprocating motion of a compression piston ring with circular micropores of rectangular profile on its sliding surface. Minimal film thickness between ring and cylinder is considered for identical and diverse pore ensembles. It was shown that the pores provide hydrodynamic load support, sufficient to keep the ring and cylinder apart even in cases of a linear ring profile and ring surface parallelism to the cylinder wall, through the whole piston stroke including the dead points. Calculations for a id pore cluster with diverse pore radius and depth (each with not less than 20 percent variance) show that fluctuation of the resulting film thickness is reduced up to 0.5 percent variance, while the thickness values of ensembles of diverse pores differ by more than 1. 5 times from that found for an identical pore population. There is apparently no need for perfect identity of the pores during production, but pore ensemble statistics must be taken into consideration in proper lubrication calculations. In general, the pore ensemble is an essential aspect in exact determination of the load support and better insight is provided into the tribological behavior of pore-covered surfaces.Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

ISSN:1040-2004    

DOI:10.1080/10402000008982330

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

An existing one-dimensional analysis for powder lubrication was upgraded to a two-dimensional level, providing an analytical tool for predicting side leakage effects. Prediction of side leakage is crucial since it accounts for heat removal from the solid lubricated contact zone and provides a measure of the wear rate. Using the enhanced analysis, a parametric study was conducted of the effect of key bearing geometric design parameters (such as film thickness and pad aspect ratios) on pressure, powder flow, load and friction. The studies revealed that for a film thickness ratio Hrof approximately 2.4, high load-carrying capability, low coefficient of friction and moderate side leakage result. For the optimum Hr, studies of the effect of Breadth to Length ratio (B/L) revealed that decreasing B/L from two results in a broader pressure peak and hence increased load capability. Decreasing the B/L ratio also lowers both the coefficient of friction and the side flow.

ISSN:1040-2004    

DOI:10.1080/10402000008982331

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The lubricating life of a grease in rolling element bearings is limited by operation at high temperatures. The thermal and mechanical stresses imposed result in gross physical and chemical changes to the grease which contribute, eventually, to failure both of the lubricant and the bearing. The problem is very complex as both grease and bearing parameters contribute to failure and these are difficult to disentangle. Most of the research work in this area has been with bearing tests where samples of bulk grease have been removed for analysis after failure. Although this approach will yield results as to grease life and the condition of the grease at the end of the test it provides little insight into the fundamental mechanisms of failure.

ISSN:1040-2004    

DOI:10.1080/10402000008982332

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This paper discusses the effect of the zinc-dialkyldithiophosphate (ZDDP) additive on increasing the friction obtained at the sliding interfaces between the elements and the pulleys of a belt-drive continuously variable transmission (B-CVT).

ISSN:1040-2004    

DOI:10.1080/10402000008982333

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The static sealing performance of compliant metallic gas seals is analyzed, accounting for both surface roughness and rarefaction effects. This is accomplished by a simultaneous solution of the contact and the flow problems for rough surfaces of which the compliant one is curved.

ISSN:1040-2004    

DOI:10.1080/10402000008982334

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor