As well recognized, a functional surface finish can determine how well the surface wears, transmits heat, and distributes a lubricant. Among the large number of surface parameters available to describe surface finish requirements, the arithmetic mean of surface roughness, Ra, is the most specified surface finish parameter across most industries and applications. However, Ra may not fully describe the functional requirement of the surface. This study is focused on the selection of surface parameters based on local contact pressure, an important indicator of friction and wear. Surface parameters are obtained from measured or generated three-dimensional topographies. Surface performance responses, evaluated by local contact pressures, are calculated from micro-contact analysis based on the rough surfaces. The analysis of correlation, indicated by Pearson correlation coefficient that is a measure of correlation strength of linear relationship, is performed among these surface parameters and between surface parameters and responses. A set of functional parameters is identified to properly specify a surface evaluated by local contact pressure.

The thermal properties of engine oil are important traits affecting the ability of the oil to transfer heat from the engine. The larger the thermal conductivity and specific heat, the more efficiently the oil will transfer heat. In this work, we measured the thermal conductivity and specific heat of a conventional mineral oil-based diesel engine lubricant and a Group V-based LHR diesel engine lubricant as a function of temperature. We also measured the specific heat of ethylene glycol. The measured values are compared with manufacturers’ data for typical heat transfer fluids. The Group V-based engine oil had a higher thermal conductivity and slightly lower specific heat than the mineral oil-based engine oil. Both engine oils had values comparable to high-temperature heat transfer fluids.

A finite element analysis of head/disk sliding continuous contact was performed to investigate the fields of temperature rise and thermal stress due to friction heat, and to develop the critical conditions for heat-induced demagnetization of the disk. Sliding contact was continued for a sufficient time to attain a relatively constant maximum temperature magnitude. The characteristic temperature increasing with whole sliding time was presented under various operating conditions. The demagnetization map for hard disk was developed by combining the simulated results together with available demagnetization temperature, a critical temperature magnitude at which occurrence of demagnetization is observed.

An improved HVOF spray process called “Gas-shrouded HVOF” (GS-HVOF) has been developed over the past several years. By using an extension nozzle at the exit of a commercial HVOF spray gun, GS-HVOF is capable of controlling the oxidation of sprayed materials during flight as well as achieving higher velocity of sprayed particles. These features result in extremely dense and clean microstructure of the sprayed coatings. The process has been successfully applied to corrosion resistant alloys such as SUS316L, HastelloyC, and alloy 625 as well as cermets such as WC-Cr 3 C 2 -Ni. Wear properties of WC cermet coatings were measured by using a pin-on-disk wear tester. The specific wear rates of the coatings prepared by the GS-HVOF with a reducing (fuel rich) flame were close to that of chrome plating. The wear amount of the heat-treated GS-HVOF coatings could not be detected after testing. It is believed that transition to mild wear appeared early because of the increased surface oxidation due to the heat treatment.

A numerical model designed to simulate a moving line contact of two rough layered bodies is presented. The model predicts contact pressures and deformations, contact temperature rise and resulting thermal stresses. The heat division between the contacting components is fully accounted for as is the interaction between the mechanical and thermal displacements. Some results are presented to illustrate the potential importance of a full thermo-mechanical analysis as compared to a purely mechanical one.

A thermal elasto-plastic contact model is developed in this paper to investigate the influences of steady-state frictional heating on the contact performance of surface asperities and subsurface stress fields. This model takes into account the asperity distortion caused by temperature variation in a tribological process, micro plastic flow of surface asperities, and the coupled thermo-elasto-plastic behavior of materials, with and without considering the strain-hardening property of the materials. The model is verified through the contact analysis between a rigid, isolated cylinder and a plane. Furthermore, the thermal effects on the contact pressure, real contact area, and average gap of rough surfaces in contact with different frictional coefficients and heat inputs under the thermal elasto-plastic contact conditions are studied.

Premature failure of mechanical seal components is often a result of the elevated temperatures at the sealing interface that arise due to frictional heating. The Heat Sink Mechanical Seal (HSS) is a new approach to interface cooling in which a micro heat sink is constructed within millimeters of the sealing interface. Coolant circulated through the highly structured pin fin region carries away the generated heat. This work investigates the impact of interface cooling on carbon wear rates for a tungsten carbide (WC) and carbon graphite material pair. Experiments are performed using a thrust washer rotary tribometer to simulate a mechanical seal operating in dry running conditions within and in excess of the PV limit for the material pair (17.5 MPa*m/s or 500,000 psi*ft/min). Results show stable operation of sealing components in harsh operating conditions as well as the potential to reduce the occurrence of thermally induced wear and failure.

In-cylinder wear and friction mitigation is essential for high-temperature, low-heat-rejection (LHR) engines. Under these extreme conditions, the piston ring/cylinder liner interface operates at oil-starved conditions. Surfaces Research has developed superior self-lubricating cylinder liner composite coatings containing novel solid lubricants to improve wear and friction under these conditions.

Component temperatures have a significant influence on ball bearing life and durability. Critical parameters such as internal clearance, contact stress and oil film thickness are influenced by the thermal characteristics of a bearing. Previous heat transfer analyses that predict bearing ring temperatures have been typically based on empirical data. A new physics-based analysis has been developed which is derived from fundamental heat transfer and fluid flow equations. Gyroscopic torque and churning forces are balanced by oil shearing contact traction, using recent developments in new life theory [1] and lubricant property models [2]. Bearing ring temperatures and heat generation calculated by the new analysis have been successfully correlated with test data over a wide range of bearing sizes and operating conditions.

Studies of the fundamental origins of friction have undergone rapid progress in recent years with the development of new experimental and computational techniques for measuring and simulating friction at atomic length and time scales. The increased interest has sparked a variety of discussions and debates concerning the nature of the atomic-scale mechanisms, which dominate the dissipative process by which mechanical energy is transformed into heat. Measurements of the sliding friction of physisorbed monolayers and bilayers provides information on the relative contributions of electronic to phononic.

In the last decade, Surfaces Research and the U.S. Army have made very significant advances in tribology for high-power-density, low-heat-rejection (LHR) diesel engines. High-temperature tribology issues, which had been major technological hurdles for LHR engine technology, have now been solved. We have developed totally new and economical Group V-based lubricants and self-lubricating coatings in our laboratories. These new lubricants enable reliable, long-term operation of diesel engines with oil sump and engine coolant more than 38°C (100°F) higher than conventional operating temperatures. Over 1300 hours of engine testing have provided detailed data on lubricant and engine component performance at high-temperature, high-BMEP LHR engine conditions.

An analytical model is developed for assessment of the steady-state temperature distribution in a wheel undergoing heating in contact with the rail and the brake shoes as well as nonuniform cooling in its periphery. The heat partitioning coefficients in the rail and the brake-shoe contacts with the wheel are incorporated in the model. These heat-partitioning coefficients can be used to evaluate the temperature field in the wheel and the brake shoes. It is shown that the wheel contact temperature is confined to a very thin depth within the surface layer (approximately 6% in the radial direction), but the rest of wheel is at the bulk temperature.

In the present paper, air pressure and temperature on the interface of the polymer matrix composite (PMC) brake pads are measured by disc brake under braking condition, and their influences are studied as well. The experimental results show that the air temperature peak is not as high as that on the surface. The air pressure of the interface varies with the applied load. The air pressure is negative under the small applied load, but positive under the large applied load. The analysis of the experimental results shows that the phenomena are caused by the friction heat and the rotate disc. Since the air pressure is very small comparing with applied load, it influences on the friction coefficient slightly. But, the negative air pressure of the interface increases the chance of the drag friction in the non-braking mode for disc brakes.

Adiabatics INC. with the support of U.S. Army Tank Automotive and Armaments Command has developed a new high temperature lubricant with additives package to work under the rigid regime of advanced Low Heat Rejection (LHR) diesel engine operating parameters. Using the newly developed high temperature lubricant on a laboratory tribology test bench and on a single cylinder LHR engine, the Army specified requirements of 410 °C Top Ring Reversal (TRR), 175 °C sump temperatures, and friction coefficient of 0.085–0.10 have been met. We have used the test data generated from the laboratory tribology test bench, and the LHR single cylinder test engine to validate the eight tribology performance parameters. The eight tribology parameters are: Oil Film thickness, shear stress, shear rate, temperature, effective viscosity, wear, specific friction work, and contact stress. Also this paper includes test data for the newly designed lubricating and cooling system. Further testing will be conducted on a multi cylinder production engine to complete the validation process of the newly developed lubricant and the lubricating and cooling system.

A model is developed to predict the thermal behavior of two sliding bodies undergoing oscillatory relative motion. The thermal model is capable of predicting the temperature rise distribution within the pin-bushing pair and the housing. The bodies geometrically form a pin-bushing configuration and the Hertzian line contact theory is used to approximate the contact pressure and the width. A quasi- three dimensional temperature model is developed by averaging the temperature in the axial direction. The resulting dimensionless heat equations and proper boundary conditions are solved by the finite element method. A series of dimensionless equations for use at the design stage is presented. A test rig capable of inducing oscillatory motion under heavy loading condition is used for measuring friction and temperature. The measured coefficient of friction history, which is curve fit as a function of time, is used in the simulations. The description of the test rig, modeling aspects, and the future extension of the research comprise the contents of this paper.

This paper reports the development and formulation of a new cost effective means of applying ceramic tribology coatings to sealing rings. This coating, though developed with the support of the U.S. Army Tank Automotive and Armaments Command for use on Low Heat Rejection (LHR) high output diesel engines, can be used on any internal engine compression seal ring. It is not limited for use in LHR diesel engines. Applying ceramic coating, especially on the compression piston ring, reduces the friction losses and wear of sliding contact surfaces. This will result in increased engine efficiency and durability. The work presented examines both laboratory and small bore engine testing of this technology. Laboratory tribometer tests compare the ceramic coating to existing and experimental piston ring tribosurfaces. Friction and wear performance demonstrated in the laboratory is verified for use in LHR diesel engine application. Low raw material cost coupled with ease of application and high deposit efficiency of the ceramic make this coating a viable candidate for commercialization.

While the support bearings are key elements of rotating machinery systems, the overall system performance and design depend on a close integration of several disciplines. For prescribed life and operating environment the applied static loads and speeds on each of the system component may be generally determined by an equilibrium analysis. Conventional rotor dynamics models may be used to model overall system dynamics, rotor response and dynamic loads imposed on the support bearings. As a function of these applied conditions bearing response and dynamic performance is determined by integration of the equations of motion of each bearing element; in the case of rolling bearings, the available bearing dynamics models, such as ADORE (Advanced Dynamics Of Rolling Elements) provide integration of the classical differential equations of motion to model real-time performance of the bearing. With prescribed bearing geometry and applied operating conditions, it is well established that lubricant properties and mechanics play a major role in determining the stability of bearing elements and overall system performance. The rolling-sliding interactions in the concentrated contacts between the bearing elements produce heat, which travels through the bearing and the overall system. This affects temperature of the bearing elements, which in turn changes the bearing geometry and material behavior including the lubricant. Thus overall system design and performance simulation requires a close iteration between the various models at varying levels of sophistication.

The tribological and electrical conduction behaviors of copper under dry sliding against copper-chromium alloys were investigated on the basis of simulation tests. The experimental results show that electrical current and tribological parameters have combined effects on both electrical conduction ability and tribological properties. High sliding velocity and electrical current density deteriorate both the tribological and electrical conduction properties in tribo-electrical sliding system. In the end, the worn surface analysis suggests that friction, resistance heat and electrical arc spoiling are the main factors to influence the tribological and electrical conduction properties.

The 12-stage FZG test (A/8,33/90) was originally developed to determine scuffing load capacity of engine oils [1]. During each load stage, the test is started at the same initial sump temperature. Heat of friction generated during a load stage results in a temperature increase of the lubricant. Final sump temperatures as high as 140 °C are often reached after the final load stage (Load Stage 12). A modified version of the test, (A/2,76/50) is used for laboratory determination of open gear grease performance [2]. In open gear lubrication, typical gear operating temperatures are in the range 50°C–80°C. Test temperatures higher than this may give rise to different wear characteristics than would be found under typical operating conditions. It would therefore be of practical interest to have a laboratory-based means to determine the temperature-dependent characteristics of an open gear lubricant. A compact heat exchanger was designed, built and inserted in the FZG test bed. By manipulating the flowrate of an external cooling medium, the temperature of the test fluid in the sump can be maintained at a desired temperature. Results for four representative open gear lubricants were obtained using the constant temperature test and compared with results obtained with the conventional test. These results indicated that the new test can discern between samples that perform similarly during the conventional test.

The need for rapid development of high efficiency jet engines and other mechanical systems has forced the pace of development of simulation tools so that the detailed behavior of the rolling element bearings can be simulated. This includes modeling of the motions, the exchanged forces, and heat between all the bearing components, i.e. rings, cage and rolling elements. The computer program BEAST is a multi-body computer program with sophisticated and robust modeling of the tribological contacts in the bearing where the exchange of forces between the bearing components takes place.