摘要:

A high molecular weight alcohol mixture has been found to offer higher grinding rates over time in machining ceramics using diamond tools. The benefits can be attributed to surface interactions of the alcohols with diamond surfaces forming a tenacious protective film under grinding conditions. The diamond particles are then protected from wear and remain sharp under grinding conditions. This allows sustained high machining rates over a much longer period of time. The ability of the alcohols to enhance grinding rates has been observed in a laboratory diamond cutter, a vertical grinder, and a surface grinder. A subsequent field trial was conducted in a manufacturing plant for five months, grinding cemented tungsten carbide cutting inserts using diamond tools. Results validated the observed laboratory benefits.Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982249

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The thermo-elastohydrodynamic lubrication is considered for Newtonian and power-law fluids. A numerical method available in the literature is utilized in obtaining solutions, for a given set of parameters, leading to establishing the maximum carrying load in terms of the slider velocity. Comparison is made with the classical lubrication theory. It is shown that there exists a threshold of the slider velocities for which increase of the slider velocity is detrimental to the ability to support loads.

ISSN:1040-2004    

DOI:10.1080/10402009908982250

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This study demonstrates that insight into the tribological reactions taking place in mixed and boundary lubrication can be provided by combining microsample four-ball wear tests with chemical analysis using gel permeation chromatography (GPC) as the principal analytical tool. At the end of the microsample four-ball wear test the lubricant turns into a grease-like mixture preventing the liquid lubricant from recirculating into the wear track and thus causing failure. Analyses of the various lubricant samples after their failure in the microsample test all show a relatively small amount of insoluble deposits and a large quantity of unreacted fresh lubricant. Virtually no intermediate reaction products were found. Combining this information with lubricant stability and the fact that a large quantity of lubricant flowed through the sliding junction while only a small portion was oxidized suggests that two very different thermal environments existin the concentrated contact. The insoluble deposits are typical of thermal oxidative reactions that require temperatures of400°C or above. The unreacted lubricant found at failure indicates that this portion of the lubricant sample was maintained at temperatures of 150°C or below. The formation of grease-like mixture with as little as four percent reacted material indicates the remaining liquid lubricant and its insoluble reaction deposits were well mixed throughout the test. These findings suggest that the hot zones causing severe lubricant degradation are in the immediate vicinity of the asperity-asperity contacts while the low temperature zone - the valleys between asperities which are in the majority - are much cooler.Presented at the 50th Annual Meeting in Chicago, Illinois May 14–19, 1995

ISSN:1040-2004    

DOI:10.1080/10402009908982251

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Seal clearance control is an advancement in noncontacting mechanical face seal operation because seal clearance variation caused by process disturbances may cause either severe face contact or excessive leakage, each of which is regarded as seal failure. The objective of this research is to control the seal clearance at a desired value overcoming operation disturbances, including variations in shaft speed and sealed fluid pressure. A flexibly mounted rotor (FMR) noncontacting mechanical face seal test rig is used in this study. The clearance control concept is to adjust the closing force that acts upon the flexibly mounted rotor. The seal clearance is measured by an eddy current proximity probe. The seal axial dynamic model is experimentally determined for the design of a proportional-integral (PI) controller with anti-windup. The controller is then applied to the test seal. Results show that the controlled seal maintains or follows set-point clearance changes with and without disturbances in sealed water pressure and shaft speed. The controlled seal is shown to respond quickly (having a small time constant) with a small control effort.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Toronto, Ontario, Canada, October 26–28, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982252

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Tests were conducted to measure the operating characteristics for two types of five-shoe tilt pad journal bearings, having a load-between-pads configuration. The bearings differed with respect to the pad arc length, the pad thickness and the pivot type. Each bearing had a diameter of 126.9 mm, a L/D ratio of 0.3, an assembled diametral bearing clearance of 0.19 mm, and a bearing preload of 0.35.

ISSN:1040-2004    

DOI:10.1080/10402009908982253

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Noise generated by car components is more noticeable today because cars have generally become quieter. In one case, the power steering units in some cars emitted perceptible and very annoying noise from the power steering unit. The nature of the noise and its exact source was not clear. Experiments conducted to pinpoint the noise source are discussed in this paper. The results suggest that vibration of the pinion seal is the most common noise source. Two types of elastomer materials used for pinion seals have been tested for noise at a range of temperatures, pressures, and shaft speeds. A new criterion is suggested for prediction of vibration occurrence in seals and other rubber frictional members. The paper summarizes the investigation of this noise, and concludes with measures to prevent it.Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982254

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The stringent and often competing requirements of high fuel economy and low emissions are placing increasing emphasis on the selection of appropriate base oils for modem engine lubricants. Two properties now recognized as important in engine oil design are the elastohydrodynamic (EHD) traction coefficient and the pressure-viscosity coefficient. The former determines the level of friction in high pressure contacts such as cams, while the latter plays a major role in determining the EHD film thickness. Unfortunately, for many fluids there is a broad correlation between the two properties so that a low traction coefficient implies a low pressure viscosity coefficient and thus film thickness. This paper measures the traction and film-forming properties of a wide range of base oil types at realistic engine oil temperatures in order to both explore the extent of this correlation and to determine the dependence of EHD lubricant properties on base oil compositions.Presented as a Society of Tribologists and Lubrication Engineers paper at the World Tribology Congress in London, United Kingdom, September 8–12, 1997

ISSN:1040-2004    

DOI:10.1080/10402009908982255

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The minimizing of friction loss of helical gears is one of today's most important problems. Though helical gears are very widely used in power transmissions of automobiles and ships, basic research on helical gears is comparatively scarce. Under these circumstances, the authors studied the friction loss of helical gears in view of various helix angles, loads, and rotational speeds. Further the relationship between temperature rise of teeth and friction loss was made clear. The results were discussed from the viewpoint of reduction of friction loss and were related to the results of the authors' spur gear tests. Friction loss and temperature rise of helical gear teeth were also investigated while the helix angles were widely varied. All these results, based on experimental investigations, were summarized and general formulas were established in view of gear design.

ISSN:1040-2004    

DOI:10.1080/10402009908982256

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Analyzing the contact between rough surfaces plays a key role in studying friction, wear, and lubrication in tribological systems. A proper description of the lubrication state and thermal condition also relies on a thorough understanding of the contact phenomena. The existing models for simulating the contact between rough surfaces are reviewed in this paper in three aspects: descriptions of rough surface profiles, expressions of the relations between the contact pressure and the surface displacement, and techniques used to solve the contact equations for the contact pressure and the surface displacements. Recent advancements in contact-models development are also briefly introduced.Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982257

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Utility of boric oxide particles in PTFE and epoxy composite materials, in sliding contact with stainless steel, is explored. Boric oxide filler can provide PTFE with a two-decade reduction in wear rate, to 10−5mm3/N-m. With adequate ambient humidity reduced wear rate can be achieved without inducing counterface abrasion, and the friction of PTFE is further reduced slightly. In such environments, boric oxide fillers can also reduce friction coefficient of epoxy from μ>0.7 to as low as μ=0.07. This lubrication mechanism results from replenishment of lubricous boric acid lamellar solid provided to the sliding interface by reaction of boric oxide with ambient water. Maintenance of the lubricating effect depends upon a sufficient rate of boric acid formation, relative to subsequent removal by wear. It is demonstrated that this formation/removal balance is affected by relative humidity and volume fraction of boric oxide filler, as well as normal load and sliding speed.Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982258

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor