Showing papers in "Tribology Transactions in 2001"
TL;DR: In this article, a model is presented to study the potential use of micro-surface structure in the form of micro pores to improve tribological properties of reciprocating automotive components, where the Reynolds equation and the equation of motion are solved simultaneously for a simplified “piston/cylinder” system with surface texturing.
Abstract: A model is presented to study the potential use of micro-surface structure in the form of micro pores to improve tribological properties of reciprocating automotive components. The Reynolds equation and the equation of motion are solved simultaneously for a simplified “piston/cylinder” system with surface texturing. The solution provides the time behavior of both the clearance and the friction force between the “piston ring” and “cylinder liner” surfaces. It is shown that surface texturing can efficiently be used to maintain hydrodynamic effects even with nominally parallel surfaces. It is also shown that optimum surface texturing may substantially reduce the friction losses in reciprocating automotive components. Presented at the 56th Annual Meeting Orlando, Florida May 20–24, 2001
472 citations
TL;DR: In this paper, a unified numerical approach for point contact problems is presented, which is capable of simulating the entire transition from the full film EHD, mixed, down to boundary lubrication, using measured 3-D roughness.
Abstract: A complete computer program package has been developed in the present work based on a recently developed unified numerical approach for point contact problems. This approach is capable of simulating the entire transition from the full film EHD, mixed, down to boundary lubrication, using measured 3-D roughness. The numerical solution can cover a full range of λ ratio, from infinity down to zero. Based on the calculated film thickness (or gap) and pressure distribution in the contact, subsurface stresses can readily be predicted. Also, friction and flask temperatures can be computed by using a non-Newtonian fluid model in the hydrodynamic regions and a measured (or assumed) coefficient of friction for boundary lubrication in the contact regions. Sample cases show that this computer program package is robust with no convergence problems encountered even under severe operating conditions. It appears to be a useful engineering tool for industrial applications.
200 citations
TL;DR: In this article, the relationship between central and minimum film thickness and rolling speed at the interface between elastohydrodynamic and boundary lubrication for a series of lubricating fluids was explored.
Abstract: Measurement technique for the study of very thin lubrication films down to one nanometer in a point contact between a steel ball and a transparent disc is used to explore the relationship between central and minimum film thickness and rolling speed at the interface between elastohydrodynamic and boundary lubrication for a series of lubricating fluids. This technique based on the colorimetric interferometry combines powerful film thickness mapping capabilities with high accuracy. It was confirmed that both hexadecane and mineral base oil obey the linear relationship between log central and minimum film thickness and log rolling speed predicted by elastohydrodynamic theory down to approximately one nanometer. Conversely, squalane and additive-treated mineral base oil showed film thickness enhancement at slow speeds caused by boundary layers formation within the lubricant film. Obtained experimental data was used for the determination of pressure-viscosity coefficients of test fluids. The measurement techniq...
166 citations
TL;DR: In this paper, a finite element model was developed to study the hydrodynamic effect of micro-pores generated by laser surface texturing (LST) in a circumferential gas seal.
Abstract: A theoretical finite-element model was developed to study the hydrodynamic effect of micro-pores generated by laser surface texturing (LST) in a circumferential gas seal. The seal is represented by two non-contacting annular surfaces of a rotating shaft and a stationary ring. The micro-pores of spherical segment shape are distributed uniformly over one of the annular surfaces. The hydrodynamic dimensionless pressure distribution in the uniform clearance between the annular surfaces is obtained from a solution of the Reynolds equation for compressible viscous gas in a laminar flow. Results of a parametric study along with a numerical example for a specific circumferential seal demonstrate a substantial hydrodynamic effect that can raise the opening average pressure in the seal clearance above the ambient one by up to 50 percent. Presented at the 56th Annual Meeting Orlando, Florida May 20–24, 2001
137 citations
TL;DR: The authors presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in San Francisco, CA October 21-24, 2001.
Abstract: Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in San Francisco, CA October 21–24, 2001
122 citations
TL;DR: A technique of relative optical interference intensity (ROII) and a high-precision force measuring system were used to measure film thickness and friction force of the oils added with ultra-fine diamond powder (UDP) in the nano-scale.
Abstract: A technique of relative optical interference intensity (ROII) and a high-precision force measuring system were used to measure film thickness and friction force of the oils added with ultra-fine diamond powder (UDP) in the nano-scale The results show that the oil containing UDP nano-particles forms a thicker film than does the pure base oil In the rubbing process, the hard spherical UDP nano-particles plow the two surfaces and produce many smooth micro-grooves The friction force decreases with sliding distance The possible mechanisms for such reduction and physical model of diamond nano-particles as additives in oils are discussed
87 citations
TL;DR: In this paper, the effects of rough surface topography and orientation on the characteristics of EHD and mixed lubrication were investigated by using a numerical approach recently developed by the present authors.
Abstract: Effects of rough surface topography and orientation on the characteristics of EHD and mixed lubrication are investigated in this paper by using a numerical approach recently developed by the present authors. This approach is capable of handling measured engineering surfaces under very severe operating conditions, and simulating the entire transition from the full film EHD continuously down to boundary lubrication. In the present study, three typical machined surfaces are employed for cases in circular contacts: a shaved surface with nearly isotropic topography, a transversely ground surface and a longitudinal ground surface. For elliptical contacts (ellipticity 4.0), 3-D sinusoidal wavy surfaces with different wavelengths in x- and y-directions are used. More than 80 cases have been analyzed, covering a very wide range of operating conditions, including full film EHD, mixed and boundary lubrication. The results indicate that at low λ ratios, the average film thickness in rough surface contacts is often sl...
81 citations
TL;DR: In this article, a series of bearing tests using the modified DIN 51 806 test designated R2F(M) have been carried out using two greases: additized and non-additized.
Abstract: Grease is degraded during use in rolling element bearings and as a result the lubrication performance can deteriorate. Under severe conditions this can result in lubrication failure and, thus, the grease life will effectively limit the bearing life. At present there is a lack of detailed information regarding the changes that occur in the grease and the way in which this degradation affects lubrication performance and failure. This paper reports an initial study into grease degradation in bearings. The aim of the work was to characterize the changes that occur to the chemical and physical properties during use. A series of bearing tests using the modified DIN 51 806 test designated R2F(M) have been carried out using two greases: additized and non-additized. The tests have been run for different temperature and speed conditions for up to 300 hours. The aim was to examine the grease during normal running rather than after failure. At the end of the tests the bearings were dismantled and grease taken from di...
71 citations
TL;DR: In this paper, the effect of surface roughness on the performance of hydrodynamic slider bearings is studied and the results are presented both graphically as well as in tabular form.
Abstract: The effect of surface roughness on the performance of hydrodynamic slider bearings is studied. A generalized form of surface roughness characterized by a stochastic random variable with non-zero mean, variance and skewness is assumed to define the bearing surface topography. Various film shapes such as: plane slider, exponential, secant and hyperbolic are considered. The results are obtained for the general lubricant film shape in integral form which are numerically computed for the shapes under consideration. The results are presented both graphically as well as in tabular form. The performance of a rough bearing can be considered in terms of an identical smooth bearing with an equivalent film thickness. It is observed, for the lubricant film shapes under consideration, that the increasing positive values of α, σ and e decrease the load carrying capacity, frictional force and temperature rise while it increases the coefficient of friction. Increasing positive values of α and e shift the center of pressur...
66 citations
TL;DR: In this paper, a stress-based fatigue life model is proposed, which is based on the induced stress field in a power function form, and the empirical data required to complete the model can be obtained using element testing in lieu of the complete bearing testing employed by LP.
Abstract: Life prediction is an essential tool in optimizing the selection of rolling bearings in machinery. Over the last several decades, the life factor-based model, based on the Lundberg and Palmgren (LP) model, has been widely accepted both for industry standards and in manufacturers' catalogs in the bearing industry. However, modeling the increasingly demanding operating conditions of modem machinery, the LP model, even modified by life factors, tends to underestimate bearing fatigue lives, particularly for lower load applications. This is particularly critical for aerospace engine and power transmission applications. A new stress-based fatigue life model is proposed (2). It has-been developed in a way such that fatigue life is associated purely with the induced stress field in a power function form. Because the model is stress-based, the empirical data required to complete the model can be obtained using element testing in lieu of the complete bearing testing employed by LP. The fatigue data for the new fati...
58 citations
TL;DR: In this paper, the influence of geometry, roughness of the sensor system and gap size on the rheological measurements of a commercial lubricating grease was investigated, and the experimental results were discussed taking into account the wall slip phenomenon.
Abstract: The objective of this paper is to investigate the influences that geometry, roughness of the sensor system and gap size exert on the rheological measurements of a commercial lubricating grease. With this aim, creep and stress growth experiments, stepped strain rate ramps and dynamic measurements were performed using different geometries and roughness. A significant influence of gap size was found in transient and steady-state experiments in a certain range of strain rate. Roughening the surface of the geometry increases considerably the values of the stress in comparison to the measurements performed with smooth surfaces. The experimental results are discussed taking into account the wall slip phenomenon. In addition to this, different grooves made in the surfaces of the tools seem to eliminate or considerably decrease these wall slip effects. However, the influence of geometry or roughness was not detected in oscillatory tests performed inside the linear viscoelastic range.
TL;DR: The authors presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in San Francisco, CA October 21-24, 2001.
Abstract: Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in San Francisco, CA October 21–24, 2001
TL;DR: In this paper, an isothermal elasto-plastic asperity contact model is developed and presented, which deals with micro plastic flows of materials and the influence of the elastoflastic deformation of materials on the behavior of contacting surfaces.
Abstract: An isothermal elasto-plastic asperity contact model is developed and presented in this paper, which deals with micro plastic flows of materials and the influence of the elasto-plastic deformation of materials on the behavior of contacting surfaces. The model is solved with the incremental form of a simplex-type algorithm. The von Mises yield criterion is used to determine the onset of the plastic deformation. The effectiveness and validity of the model are studied through analyzing a Hertzian contact problem. Substrate stresses are calculated and differences are observed. Furthermore, the contact pressure, real area of contact, and average gap of real rough surfaces under the elastic, elastic-perfectly-plastic, and the elasto-plastic contact conditions are numerically investigated and the results are compared. Presented at the 56th Annual Meeting Orlando, Florida May 20–24, 2001
TL;DR: In this paper, a test method for measuring steady-state stiffness of foil air journal bearings is extended to measure trends in bearing stiffness at high temperature, and it is found that the stiffness of the tested bearing decreases in general as the temperature increases from 25° to 538 °C.
Abstract: A previously developed test method for measuring steady-state stiffness of foil air journal bearings is extended to measure trends in bearing stiffness at high temperature. Steady-state stiffness of the tested foil bearing is found to decrease in general as the temperature increases from 25° to 538 °C. The magnitude of stiffness change observed is roughly a factor of two, which is important information for the design of future high speed turbomachinery. It is expected that damping in foil bearings may also be affected by changes in temperature necessitating future testing to evaluate the trends in dynamic bearing characteristics. Presented at the 56th Annual Meeting Orlando, Florida May 20–24, 2001
TL;DR: In this article, three base fluids of very similar viscosities, a polyalphaolefin, a diester and an alky lated aromatic, have been obtained and their EHD film thickness and traction behavior measured at a range of pressures.
Abstract: The aim of this study was to investigate the elastohydrodynamic (EHD) properties of lubricant blends. Three base fluids of very similar viscosities, a polyalphaolefin, a diester and an alky lated aromatic, have been obtained and their EHD film thickness and traction behavior measured at a range of pressures. Blends of these fluids have been prepared and the influence of blending on film thickness and traction has been investigated. Traction measurements were conducted at film thicknesses between 100–200 nm and thermal analysis was incorporated to correct for in-contact shear heating. The blends showed a broadly linear relationship between the inlet pressure-viscosity coefficient and blend composition. Isothermal traction comparisons revealed that traction is not an additive property of lubricant blends. Presented at the 53rd Annual Meeting Detroit, Michigan May 17–21, 1998
TL;DR: In this paper, four rolling-element bearing life theories were chosen for analysis and compared for a simple roller-race geometry model, including those of Weibull, Lundberg and Palmgren; Ioannides a...
Abstract: Four rolling-element bearing life theories were chosen for analysis and compared for a simple roller-race geometry model. The life theories were those of Weibull; Lundberg and Palmgren; Ioannides a...
TL;DR: In this paper, the effects on component materials on friction and wear characteristics correspond well to the knowledge we have gained though experiences, and the predicted friction data of the designed brake pads agreed well with the test data.
Abstract: Stochastic methods were used for the analysis of test data related to the design of brake pad compositions. The friction and wear test data were analyzed by MRA (Multiple Regression Analysis) and the effect of %volume of the components on the friction and wear characteristics was obtained quantitatively in the form of the standard regression coefficients. The analytical results concerning the effects on component materials on friction and wear characteristics correspond well to the knowledge we have gained though experiences. It was also found that the standard regression coefficients, particularly those for the wear are sensitive to the experimental conditions. This finding corresponds to the lower reproducibility of the results of the wear test. The data were then used to design the composition of brake pads. Optimization was conducted using a GA (Genetic Algorithm). The predicted friction data of the designed brake pads agreed well with the test data. The calculation time is about J/700 of that by an a...
TL;DR: In this paper, four roller profiles used in cylindrical roller bearing design and manufacture were analyzed using both a closed form solution and finite element analysis (FEA) for stress and life.
Abstract: Four roller profiles used in cylindrical roller bearing design and manufacture were analyzed using both a closed form solution and finite element analysis (FEA) for stress and life. The analyzed roller profiles were flat, end tapered, aerospace, and fully crowned and loaded against a flat raceway. Four rolling-element bearing life models were chosen for this analysis: those of Weibull; Lundberg and Palmgren; Ioannides and Harris; and Zaretsky. The flat roller profile without edge loading has the longest predicted life. However, edge loading can reduce life by as much as 98 percent. The end-tapered profile produced the highest lives, but not significantly higher than those produced by the aerospace profile. The fully crowned profile produced the lowest lives. Except for the flat roller profile, the predicted lives with the FEA method exceed those with the closed form solution. The fatigue limit proposed by Ioannides and Harris equates to one-half the value of a compressive residual stress that may exist in...
TL;DR: In this paper, an optimized 35mm-bore-angular-contact ball bearing on a high-speed, high-temperature bearing tester was compared to speeds of 2.5¥106 DN.
Abstract: Parametric tests were conducted with an optimized 35-mm-bore-angular-contact ball bearing on a high-speed, high-temperature bearing tester. Results from both air-oil mist lubrication and oil-jet lubrication systems used to lubricate the bearing were compared to speeds of 2.5¥106 DN. The maximum obtainable speed with air-oil mist lubrication is 2.5¥106 DN. Lower bearing temperatures and higher power losses are obtained with oil-jet lubrication than with air-oil mist lubrication. Bearing power loss is a direct function of oil flow to the bearing and independent of oil delivery system. For a given oil-flow rate, bearing temperature and power loss increase with increases in speed. Bearing life is an inverse function of temperature, the difference in temperature between the individual bearing ring components, and the resultant elastohydrodynamic (EHD) film thicknesses. Bearing life is independent of the oil delivery system except as it affects temperature. Cage slip increased with increases in speed. Cage slip...
TL;DR: In this paper, an economic (time and effort saving) and reliable dynamic (considering load and speed variation with crank rotation) analysis to study the combined effect of temperature and lubricant shear thinning on the engine bearing performance is provided.
Abstract: The high shearing stresses encountered in the modern engine bearing lubricant film lead to significant drop in viscosity of multigrade oils and affect the values of film thickness, power loss and oil flow significantly in the engine bearings. The popular mobility method is incapable to incorporate shear thinning, and time-consuming numerical schemes are not readily acceptable in industry. The present study aims to provide an economic (time and effort saving) and reliable dynamic (considering load and speed variation with crank rotation) analysis to study the combined effect of temperature and lubricant shear thinning on the engine bearing performance. The variation in the lubricant viscosity with shear is considered as described by the Cecim-equation. An effective thermal analysis is used to evaluate the operating oil-temperature that determines the low and high shear viscosity, and shear stability parameter. A crankshaft bearing is analyzed and results are presented for various performance parameters suc...
TL;DR: In this paper, the combined effect of non-Newtonian lubricant behavior and bearing shell flexibility on the performance of an orifice compensated multirecess hydrostatic/hybrid journal bearing system is studied.
Abstract: The combined effect of non-Newtonian lubricant behavior and bearing shell flexibility on the performance of an orifice compensated multirecess hydrostatic/hybrid journal bearing system is studied. The analysis considers the constitutive equations for the flow of a non-Newtonian lubricant through an orifice restrictor, the generalized Reynold's equation governing the flow of lubricant having variable viscosity and 3-D elasticity equations. The computed results demonstrate that loss in bearing performance due to the pseudo-plastic effect of the non-Newtonian lubricant can be mitigated by a proper selection of parameters such as the deformation coefficient ([Cbar]4) and non-linearity factor ([Kbar]) or power law index (n).
TL;DR: In this article, a theoretical study describing comparative performance of non-recessed hybrid journal bearing using different flow control devices has been carried out by considering bearing shell flexibility into the analysis, the relevant governing equations have been solved using finite element method.
Abstract: For bearings operating under heavy loads, the elastic deformation of bearing surface induced by fluid film pressures can no longer be neglected as it is comparable to the order of magnitude of fluid film thickness. In the present work a theoretical study describing comparative performance of non-recessed hybrid journal bearing using different flow control devices has been carried out by considering bearing shell flexibility into the analysis. The relevant governing equations have been solved using finite element method. The comparative performance of non-recessed hybrid journal bearings of two separate configurations have been studied for various values of bearing flexibility parameter (([Cbar]d)). The results have been presented for hole-entry type journal bearings compensated by capillary, orifice and constant flow valve restrictors and for a slot-entry type journal bearing, for the same set of values of operating and geometric parameters. The computed results indicates that in order to get an improved ...
TL;DR: In this article, the design and testing of two adjustable hydrodynamic journal bearings are outlined, each of which was designed to replace a conventional bearing in a large marine gearbox.
Abstract: The design and testing of two novel adjustable hydrodynamic journal bearings are outlined. Each was designed to replace a conventional bearing in a large marine gearbox. They were tested in a land based rig and their performances compared with that of the conventional bearing. The novel bearings demonstrated the ability to suppress journal centre orbits, to reposition the journal centre in any direction, and to operate with significantly reduced temperature rise. One of the bearings also demonstrated the ability to translate the journal centre in a controlled manner by an amount exceeding double the clearance of the conventional bearing. Implications of such characteristics are considered as potential benefits in various bearing applications. Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in San Francisco, CA October 21–24, 2001
TL;DR: In this article, the authors evaluated the scuff resistance of surfaces in regular diesel fuel containing 500 ppm sulfur and in Fischer-Tropsch synthetic diesel fuel with no sulfur or aromatics and found that the sulfur-containing fuels have about 20% higher scuffing resistance than does fuel without sulfur.
Abstract: Low-sulfur and low-aromatic diesel fuels are being introduced in order to reduce various types of emissions in diesel engines to levels in compliance with current and impending U.S. federal regulations. The low lubricity of these fuels, however, poses major reliability and durability problem for fuel injection components that depend on diesel fuel for their lubrication. In the present study, the authors evaluated the scuff resistance of surfaces in regular diesel fuel containing 500 ppm sulfur and in Fischer-Tropsch synthetic diesel fuel containing no sulfur or aromatics. Tests were conducted with the high frequency reciprocating test rig (HFRR) using 52100 steel balls and H-13 tool-steel flats with and without Argonne's special carbon coatings. Test results showed that the sulfur-containing fuels have about 20% higher scuffing resistance than does fuel without sulfur. The presence of the carbon coating on the flat increased scuffing resistance in both regular and synthetic fuels by about ten times, as me...
TL;DR: In this paper, a flat-faced thrust washer bearing system was found to experience distress by the combination of rotational speed, axial load, and the sequence and rate of their application.
Abstract: This study addresses the mechanisms that distress a flat-faced thrust washer bearing system. This washer bearing system separates a helical gear and its carrier within a gearset. It was found that the bearing can experience distress by the combination of rotational speed, axial load, and the sequence and rate of their application. Distress is defined as a sudden rise in the real-time frictional torque and temperature. The various tests suggest the presence of hydrodynamic effects at certain rotational speeds and axial load combinations marked by decreases in the calculated effective coefficient of friction with decreases in velocity. In the tested cases, a distinct increase in the coefficient of friction occurs at the instant of distress. Presented at the 56th Annual Meeting Orlando, Florida May 20–24, 2001
TL;DR: In this article, the authors investigated the influence of different parameters on the tribological behavior of MoS2 films and concluded that the frictional properties are dependent on prevalent humidity as well as contact pressure and the drop of μ with contact pressure is independent of frictional heating.
Abstract: The drop of coefficient of friction of MoS2 coatings with increase in contact pressure has been reported by various earlier researchers. Different hypothesis have been put forward to explain this phenomenon. This paper covers details of experiments carried out to investigate this further. Experiments have been carried out on reciprocating sliding wear and friction machine to bring out the influence of different parameters on the tribological behavior of MoS2 films. Role of frictional heating in this behavior has also been brought out. It is concluded that frictional properties of MoS2 are dependent on prevalent humidity as well as contact pressure and the drop of μ with contact pressure is independent of frictional heating.
IBM1
TL;DR: In this paper, contact start/stop (CSS) tests were conducted to investigate the effects of Zdol lubricant bonding, thickness, and relative humidity on magnetic recording disks.
Abstract: The magnetic recording industry predominantly uses Zdol to lubricate the carbon overcoat of magnetic recording disks. Zdol comprises a perfluoropolyether chain terminated with hydroxyl end groups that are capable of reversibly bonding to the carbon overcoat. Contact start/stop (CSS) tests were done to investigate the effects of Zdol lubricant bonding, thickness, and relative humidity on durability. The durability improved with increasing thickness of fully bonded or mobile Zdol. The durability decreased with increasing initial bonded fraction and with decreasing relative humidity. The bonded fraction increased with time during the tests at elevated temperature and low relative humidity. Presented as a Society of Tribologists and Lubrication Engineers Paper at the ASME/STLE Tribology Conference in Seattle, Washington, October 1–4, 2000
TL;DR: In this paper, the authors present a method to predict the bearing frictional heat generation rates with reasonable accuracy considering hearing loading and speeds, realistic lubricant rheological proper tie-off.
Abstract: Friction and heat generation in oil-lubricated ball bearings is mainly the result of sliding in the ball-raceway contacts and agitation of the lubricant in the free space between the balls, cage. and bearing rings. Endurance of a ball bearing is highly dependent on the thicknesses of the oil films which serve to separate the balls from the raceways in a well-lubricated bearing. The film thicknesses, in turn, are dependent upon the lubricant's viscous properties. These are functions of bearing temperatures and are determined by the balance between the rates of frictional heat generation and heat dissipation. Therefore, in the design of a ball bearing application such as the high speed rotor and low speed rotor support bearings in an aircraft gas turbine, it is important to be able to predict the bearing frictional heat generation rates with reasonable accuracy. This paper presents a method to perform the required calculations considering hearing loading and speeds, realistic lubricant rheological propertie...
TL;DR: In this article, the authors used a control volume, numerical formulation to model the three dimensional flow of mass, momentum and energy in the thrust bearing and included thermoelastic deflection of the pad and flow of oil in the groove between the pads.
Abstract: Laboratory experiments that simulate the conditions acting on large spring-supported thrust bearings in hydroelectric generators were performed and film thicknesses, temperatures and pressures were measured. A software package provided theoretical predictions of the experimental results. This software used a control volume, numerical formulation to model the three dimensional flow of mass, momentum and energy in the thrust bearing and included thermoelastic deflection of the pad and flow of oil in the groove between the pads. A detailed comparison of the experimental data with the numerical predictions showed quite good overall agreement, particularly with the deformed shape and temperatures of the pad. The agreement provided evidence of the fidelity of the software package and supported its continued use in analysis and design. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Toronto, Ontario, Canada, October 26–28, 1998
TL;DR: In this paper, a condition monitor for liquid lubricated mechanical seals utilizes actively generated ultrasonic shear waves to determine conditions at the sealing interface, which is suitable for use with both non-contacting and partially contacting seals.
Abstract: A recently developed condition monitor for liquid lubricated mechanical seals utilizes actively generated ultrasonic shear waves to determine conditions at the sealing interface. A shear wave transducer is mounted on the backside of the non-rotating seal face, and generates waves that propagate toward the sealing interface. The amplitude of the reflected waves indicates whether or not face contact occurs and, if there is contact, the severity of contact. Thus, this monitor is suitable for use with both non-contacting and partially contacting seals. Laboratory tests on a commercial, unbalanced seal demonstrate the effectiveness of the approach. Presented at the 56th Annual Meeting Orlando, Florida May 20–24, 2001