Energy savings and limited polluting emissions are crucial for the automotive industry. The micro-geometry of the cylinder-liner-piston-ring contact is studied. Functional parameters are analysed on liners at different number of fired cycles.

Precise control of friction is very important for energy efficiency and sustainability in manufacturing processes. In the present investigation, various surface textures have been employed to vary the frictional conditions. More specifically, textures were varied from unidirectional to criss-cross to unidirectional by grinding the steel surfaces against emery papers for various numbers of cycles. Sliding experiments were conducted using an inclined pin-on-plate apparatus against the prepared steel surfaces under dry and lubricated conditions. In the experiments, it was observed that the coefficient of friction and transfer layer formation on the harder surfaces were controlled by the textures of the harder surfaces under both dry and lubricated conditions. The asperity angle of the harder surface plays a dominant role in controlling the friction and transfer layer at the sliding interface. Thus, by understanding appropriate roughness parameters, the friction and wear performance can be accurately controlled to enhance energy efficiency and the quality of the finished products in manufacturing process.

In self-organized sliding processes, the surfaces align to each other during sliding. This alignment leads to a more ordered contact state and significantly influences the frictional behavior. To understand the self-organization sliding processes, experiments were conducted on a pin-on-plate reciprocating sliding tester for various numbers of cycles. In the experiments, soft magnesium pins were slid against hard steel plates of various surface textures ( undirectional , 8-ground , and random ). Experimental results showed that the transfer layer formation on the steel plates increased with increasing number of cycles for all surfaces textures under both dry and lubricated conditions. The friction also increased with the number of cycles under dry conditions for all of the textures studied. During lubricated conditions, the friction decreased for unidirectional and 8-ground surfaces and increased for random surfaces with the number of cycles. Furthermore, the friction and transfer layer formation depend on the surface textures under both dry and lubricated conditions during the first few sliding cycles. Later on, it is less dependent of surface textures. The variation in the coefficient of friction under both dry and lubrication conditions were attributed to the self-organization process that occurred during repeated sliding.

In normal IC engine operation 1 st compression ring sustains thermal loads effectively. At large radial clearance in low-speed engine start up it has to act as effective seal against thermal loading. Absence of elastohydrodynamic lubricating (EHL) film and secondary displacements expose the ring to adhesive wear in initial engine start up. Isothermal hydrodynamic and EHL models of parabolic-faced ring are developed numerically after incorporating secondary dynamics of piston assembly at a low engine start up speed. Reynolds equation is solved to generate hydrodynamic pressures and film profiles in 4-stroke cycle. In EHL model inverse solution technique and elastic displacements of ring and liner are employed to generate pressures and film profiles. The simulation results suggest that a large ring-to-bore clearance increases eccentricity and affects EHL of 1 st compression ring when a low-viscosity grade oil is used in initial engine start up.

Owing to the fast technological developments, the operating conditions of the machines are becoming very stringent, exact and more demanding. Various journal bearing designs have been developed to prevent the undesired effect of bearing whirl. An example of a successful design is the four-lobe multirecess journal bearing. The bearing which having four curved segments that referred to as four lobes is the four-lobe multirecess journal bearing. Further, as the 4-lobe journal bearing is expected to run over a number of cycles during its lifetime, it is subjected to several start/stop operations. These transient periods causes the bearing bush to wear out between the recesses and significantly affects the bearing performance. The modified Reynolds equation governing the flow of lubricant in the clearance space of bearing have been solved including the combined effects of three aspects, the worn effect, the misalignment angle and offset factors, using an iterative scheme based on FEM and Newton-Raphson method. The simulated results have been presented for a wide range of offset factor δ, wear depth parameter, journal misalignment factors (φ, Ψ) and external load. The simulated results suggests that it is an imperative to account for the effect of wear along with misalignment of journal in order to predict the performance of the bearing accurately. Further, it has been observed that in general as the value of offset factor increases the static and dynamic performance of the 4-lobe four pocket worn misaligned hybrid journal bearing compensated with orifice restrictor is clearly affected as compared to similar four pocket unworn aligned hybrid circular journal bearing. Further the bearing having offset factor δ = 1.2 improves the stability due to increase in the bearing stiffness and reduced magnitude of the cross-stiffness components.

In the normal low-speed engine operation, elastohydrodynamic lubrication (EHL) of piston skirts and lubricant rheology reduce friction and prevent wear. In a few initial start up cycles, a very low engine speed and absence of EHL cause adhesive wear. This study models hydrodynamic and EHL of piston skirts in the initial very low cold engine start up speed by using a high viscosity lubricant. The 2-D Reynolds equation is solved and inverse solution technique is used to calculate the pressures and film thickness profiles in the hydrodynamic and EHL regimes, respectively. The work is extended to investigate the effects of three very low initial engine start up speeds on the transverse eccentricities of piston skirts, film thickness profiles and pressure fields in the hydrodynamic and EHL regimes. Despite using a viscous lubricant, thin EHL film profiles are generated at low start up speeds. This study suggests very low speed optimization in the cold initial engine start up conditions to prevent piston wear under isothermal conditions.

In this study, the effect of micro-grooves on hydrodynamic fabrication characteristics between a piston ring and a micro-grooved cylinder liner is analyzed numerically. Elrod’s universal equation satisfying JFO theory is adopted to predict the cavitation region properly and calculate the pressure distribution between a piston ring and a micro-grooved cylinder liner. The analysis is carried out by varying the shape, depth, length, width and location of micro-grooves during the full engine cycle. The results show that micro-grooves can make friction loss decrease in comparison with a non-textured cylinder liner.

The purpose of this study was to investigate the effect of cooling contact surface temperature of the test cylinder when a rise in contact temperature over 100 degree C occurs during boundary lubrication tribological testing. The Hertzian contact pressure in a ball on cylinder tests will be optimized with respect to the contact temperature using Design of Experiment (DOE) software. Several boundary lubrication tests were conducted to study the behavior of 0.1 P% (phosphorus percentage) plain ZDDP oil in the presence of 0.4% FeF 3 under two different rotational speeds (lower stage of 100 rpm for the first 5000 revolutions and higher stage of 700 rpm until failure or 100000 revolutions whichever comes first). The one rotational speed of 700 rpm until failure will be compared to the two speed stages under a contact cooling surface temperature and different contact loads (2.77GPa–3.8Gpa Hertzian contact pressures). The two different speed stages indicate better performance under an extreme contact load and a lower contact surface temperature; whereas higher contact surface temperature and lower load are needed for the one speed stage of 700 rpm cycle.

The contact of two elastic bodies with a frictional interface can lead to friction-induced instabilities. The instabilities are either due to the velocity-dependence of friction, or due to the coupling of friction with the thermal expansion or wear, or due to the destabilization of the interface elastic waves. The instabilities lead to friction-induced vibrations. The linear elasticity usually provides a criterion for the onset of the instability and predicts that the amplitude of the unstable vibration grows exponentially with time. However, it does not provide any information about the amplitudes of vibrations. It is expected that the amplitudes of vibrations grow exponentially until they leave the range of applicability of the linear theory and reach a certain limiting cycle. We discuss how various non-linear methods of pattern-formation analysis can be applied to this problem, including the Turing systems, self-organized criticality, etc.

In the present investigation, various kinds of textures ( undirectional, 8-ground , and r andom ,) were attained on a set of steel plate surfaces. The roughness of the textures was varied using different grits of emery papers or polishing powders. Pins made of pure magnesium were then slid against the steel plates at various numbers of cycles (1, 2, 6, 10 and 20) using an inclined pin-on-plate sliding apparatus. In the experiments, it was observed that the coefficient of friction and the formation of a transfer layer depended on the die surface textures under both dry and lubricated conditions. The coefficient of friction increased with number of cycles under dry conditions for all of the textures studied. Under lubricated conditions, however, the coefficient of friction decreased for unidirectional and 8-ground surfaces and increased for random surfaces with the number of cycles. A stick-slip phenomenon was observed under both dry and lubricated conditions. Occurrence of the stick slip behavior depended on the surface texture, the load and the number of cycles. The variation in the coefficient of friction under both dry and lubrication conditions was attributed to changes in the texture of the surfaces during sliding.

The multiple normal loading-unloading process of an elastic-plastic sphere by a rigid flat is analyzed for stick contact condition and both kinematic and isotropic hardening models. The behavior of the global contact parameters as well as the stress field within the sphere tip is presented for several loading cycles. It was found that under stick contact condition secondary plastification occurs even after the second loading cycle and that the hardening model used has little effect on the loading-unloading process. The cyclic loading process gradually converges into elastic shakedown.

A pin joint simulation machine has been built to test a real landing gear pin joint under realistic loading and reciprocation conditions. The pin is loaded hydraulically using a hydraulic actuator to apply a fixed displacement cycle whilst measuring the reactive torque. The machine was used to measure the torque cycle (and hence friction coefficient) required to operate the joint. In this work a method of evaluating different formulation greases has been proven. This involved measuring their frictional torque and also evaluating performance using a Sommerfeld type approach that displays the different lubrication regimes in the joint for different conditions. Measured friction coefficients were in the region of 0.02 to 0.12 depending on the joint load and articulating speed. In actual gear the surface sliding speed is low and so the joint operates in the boundary regime. The required torque and coefficient of friction have been related to the lubrication mechanisms occurring as a function of articulation angle, reciprocal frequency and applied axial load for lubrication starvation in a reciprocating journal bearing.

With the development of modern machine, the gear sets have to operate under high power high revolution; lubrication performance plays a vital role to the gear sets. In this study, lubrication analysis of spur gears under high speed is conducted based on the elliptical contact and unified Reynolds equation system model. The transient effect and thermal effect are taken into considered. The results show that the transient effect strongly influences the lubrication characteristics during the mesh cycle, while thermal effect enhances the transient effect.

When two surfaces in static contacts are subjected to combined loads applied in the normal and tangential directions, or just a normal load for dissimilar materials, microscopic slip would take place at certain areas of the contact region even though the contacting bodies remain still without macroscopic movement. The micro-slip is considered a major cause of fretting wear for the materials in contacts under alternating dynamic load or vibration, referred as the fretting contacts in this study. The fretting contact problem was solved using a semi-analytical method (SAM), in which analytical relations between a unite stress and corresponding surface displacement were obtained on the basis of Green functions. The contact pressure and shear tractions were then calculated by minimizing the complementary energy, and by a numerical procedure based on Conjugate Gradient Method (CGM) and Fast Fourier Transform (FFT) technique. The algorithm is very effective since the meshes are applied to the positions just in the contact areas of interest, which saves the computing time. The fretting contacts of dissimilar materials were studied and the effects of surface roughness were analyzed. Results show that the coupled effects of shear traction and material dissimilarity make the traction distributions quite different with the solutions from similar materials. The solutions under dynamic load depend on the path or history of the loading process, but the stress distributions and load-displacement curves will quickly converge to a periodic stability after several load cycles.

A very thin functionalized polyethylene (fPE) film is successfully attached to Si substrate via a reactive benzophenone (Ben) layer. The presence of fPE promotes the wear durability of Si/Ben/fPE to 1000 cycles compares with 100 cycles of Si/Ben under 40 mN applied load and 500 rpm sliding speed. As an enhancement, perfluoropolyether (PFPE) is applied as a top mobile lubricant layer coated onto Si/Ben and Si/Ben/fPE and their tribological properties are evaluated under the same experimental conditions. A significant improvement in the wear durability is observed as Si/Ben/PFPE fails at 250,000 cycles and Si/Ben/fPE/PFPE does not fail till one million cycles. Si/Ben/fPE/PFPE can withstand the maximum applied load of 150 mN that provides the PV limit of 106.6 MPa ms −1 .

Contact-mode polycrystalline silicon microdevices were tested in reciprocating sliding in high vacuum. Changes in the adhesion and friction properties of the microdevice sidewall surfaces were evaluated by tracking the development of the adhesion force and static friction coefficient with the accumulation of sliding cycles. After a run-in period of no discernible changes, the adhesion force increased monotonically with the number of sliding cycles, while the static coefficient of friction decreased continuously. Scanning electron microscopy revealed the existence of two sliding regimes where asperity deformation and adhesion were the dominant wear processes. The evolution of adhesion and static friction at sidewall contact interfaces is interpreted in the context of physicochemical phenomena intrinsic of poly-crystalline silicon microdevices.

Tribology and solid mechanics are essential when studying engine lubrications. Very reproducible boundary lubrication tests were conducted as part of Design of Experiment software (DOE) to study the behavior of fluorinated mix in developing environmentally friendly (reduced P and S) anti-wear additives for future engine oil formulations using ball on cylinder testing protocol. In this study fully formulated oil and ZDDP plain oils were tested under the protocol of two cycles. A 100 rpm cycle was used for the first 5000 revolutions and a 700 rpm cycle was used until failure or 100000 revolutions whichever comes first. All tests were generated under extreme boundary lubrication (Hertzian contact pressure of 2.72 GPa). Design of Experiment (DOE) with 2 level factorial was used to investigate the failure and wear responses with respect to fluorinated mix interactions in plain and fully formulated oils. The two cycle’s tests indicate better performance than the one cycle test. Findings indicate that the most significant factors, affecting friction and wear are fluorinated mix concentrations together with oil formulation.

Fretting fatigue has consistently been described as an “insidious” fracture process due to the difficulty in modeling and predicting fretting-induced crack initiation. Components can develop fretting fatigue cracks even when they are designed for minimal relative motion, as in the case of a turbine blade root. Vibrations that are typically small enough to be considered negligible in engineering analysis can cause cracks that will lead to component failure. The sliding distance for fretting to occur is loosely defined as tens to hundreds of micrometers. To date, there has not been a good delineation between the fretting motion and gross-sliding regimes. Likewise, it is not well understood when a given component will experience fretting fatigue or pitting (which is associated with gross sliding and is often seen in gear components). Preliminary data suggest that pitting-like cracks can initiate in a hemisphere-on-flat linear reciprocating configuration at a low number of cycles (10 4 ) and fretting-sized displacements (200–300μm). Because of the differences between the mechanisms for failure in fretting and pitting, new insight must be developed to determine parameters under which to expect either failure mode. This work seeks to characterize these two forms of failure and to determine the conditions under which fretting or pitting becomes dominant to develop a new tool for the prediction and prevention of moving components.

In the normal high speed engine operation at small piston-to-bore radial clearance, elastohydrodynamic lubrication (EHL) of skirts and non-Newtonian lubricant behavior prevent adhesive wear, but in the initial engine start up, the large clearance, low speed and absence of EHL, cause start up wear. This study models 2-D upper convected Maxwell viscoelastic EHL of piston skirts at small radial clearance in a few initial low speed engine start up cycles by solving the Reynolds equation and using the inverse solution technique. The numerical analysis incorporate characteristic lubricant relaxation times and a perturbation method to predict and compare hydrodynamic and EHL pressures and film profiles. The effects of viscoelasticity on the lubricant characteristics, transverse eccentricities of piston, film thickness, and pressure fields in the hydrodynamic and EHL regimes are investigated. This study suggests that EHL film is formed at very small piston-to-bore radial clearance at low start up speed under assumed conditions to prevent start up wear as viscoelasticity produces a beneficial effect on piston skirts lubrication in the initial engine start up.

The contact area, friction force and relative displacement evolution at the very early stage of fretting are investigated experimentally. Copper and steel spheres of various diameters are loaded against a hard sapphire flat by a range of normal loads deep into the elastic-plastic regime of deformation. A reciprocating tangential loading is then applied with a maximum loading below the static friction to avoid gross slip. Real-time and in situ direct measurements of the contact area, along with accurate measurements of the friction force and relative displacement, reveal substantial junction growth and energy dissipation mainly in the first loading cycle. The so called “slip amplitude” is found to be attributed to residual tangential plastic deformation rather than to interfacial slip. Elastic shake-down is observed for the 2.5% hardening steel spheres while plastic shake-down is observed in the case of the elastic perfectly plastic copper spheres.