Honing is a superfinishing process that generates fine surface topographies with interesting tribological properties. However the control of the process requires highly experienced operators. The selection of proper stones (abrasive grit size and type) is decisive for reaching the target topography. Furthermore, especially in the case of a feed controlled process, the stone expansion must be in adequacy with the selected stone. This paper proposes to investigate the effect of the abrasive grit size for different stone expansions on surface topographies generated during the honing process. Honed samples are produced by a specific test bench reproducing the honing kinematics and recording process induced forces. In total, two hundred forty areal surface topography measurements are analyzed and discussed alongside with the force measurements. A systemic analysis of a wide range of roughness parameters is performed. Results demonstrate that the grit size has a significant impact on the final topography signature. Furthermore, even though expansion speed was doubled, no obvious influence was observed on the surface roughness parameters except one (isotropy Str). Based on these observations it is suggested that the expansion speed has a limited impact on the number of grooves generated.

In this paper three different combinations were evaluated: (i) steel pin vs steel roller, (ii) steel pin vs tungsten disulfide (WS2) coated roller and (iii) PVD pin vs steel roller. The aim of this paper is to properly quantify the topographical variations of the pin/roller surfaces and asses the appropriateness of the measuring technique before and after the tribological tests primarily performed for friction reduction. In-house tribometer was used to test the friction/wear performance of the three different combinations. Surface topographies were measured by white light interferometer (3D) and mechanical stylus (2D). To enable fast relocation on the stylus and interferometer, a 3D printed mask was used. Regarding the pins, Sa, Sk and Svk have been found to follow the wear changes: the lowest wear change for the combination (ii) and highest for the combination (i) but less for the combination (iii). Regarding the changes of Ra on the pin locations where edge contact occurs, the largest changes were found to be for combination (i), followed by combination (ii) and (iii). Ra and Rk change less significantly for the roller surfaces. Good correlations among the friction, initial/final roughness and radial displacements were also found.

In order to minimize the fuel consumption in internal combustion engines, the frictional losses must be minimized between the moving parts such as the sliding bearings. In this study, the sliding f ...

Topographies are one of the challenges for the development of the metal additive manufacturing promising technique. The article investigates multi scale topographies (from form to roughness) of as built surfaces generated by selective laser melting (SLM). Different building inclinations of samples were observed both for upskin and downskin surfaces with a wide range of measuring techniques. The two main aims are: (i) to make a critical review of measuring techniques at different scales, (ii) to enlighten the different surface generation phenomena (and the corresponding scale) occurring during additive manufacturing. The effect of heat treatment on each scale of the topography is also discussed. It is found that the focus variation technique is well suited for AM surfaces. Concerning the observation of the inclined surfaces, some parameters are emphasized as good indicators of typical signatures of AM surfaces: isotropy for the weld track component, the skewness and Rsm for the staircase effect, fractal dimension for the presence of partly melted particles. The different parameters studied helps to model and understand the different surface generation phenomena aforementioned.

The piston system accounts for about the half of the frictional losses of internal combustion engines and requires special testing methods to understand and improve its function. The most common way to screen the surface performance is to rub ring/liner segments against each other in a reciprocating manner. However, short reciprocating tests have intrinsic low sliding speeds, unable to reach the mixed/hydrodynamic regimes found in the engine, especially at the mid-stroke. This paper presents a rotating test for the oil control ring, which has the largest frictional losses of all other rings. Both reciprocating and rotating tests were conducted using different in-house developed modules and fixtures. Twin land oil control rings against liners with two different finishes commonly used in heavy duty diesel truck engines were tested under similar loads and speeds as in a real engine. Engine oil 5W-30 and room temperature was used for all the tests. Sliding speed, load, friction force and electrical resistance were recorded during the tests. The results show a clear discrimination of the different liner finishes depending on the lubrication regime present.

A low friction piston ring pack, with tangential load halved, was tested in engines with four different cylinder liner finishes. Oil consumption, oil temperature and liner surface temperature were monitored at different load and speed levels, under similar test conditions. The two smoother surfaces generally kept lower oil consumption compared to the two rougher ones. Results were correlated using an area-fractal analysis. The relative area of the surface was calculated at different scales and the result was compared with the level of oil consumption for the different liner surfaces at different engine speeds. It was found that oil consumption was strongly correlated with scale for areas of above 1000 mu m(2) and below 20 mu m(2).

The reliability and lifetime of machine elements such as gears and rolling bearings depend on their wear and fatigue resistance. In order to screen the wear and surface damage, three finishing processes: (i) brushing, (ii) manganese phosphating and (iii) shot peening were applied on three disc pairs and long-term tested on a twin-disc tribometer. In this paper, the elastic contact of the disc surfaces (measured after only few revolutions) was simulated and a number of functional and roughness parameters were correlated. The functional parameters consisted of subsurface stresses at different depths and a new parameter called 'pressure spikes' factor'. The new parameter is derived from the pressure distribution and takes into account the proximity and magnitude of the pressure spikes. Strong correlations were found among the pressure spikes' factor and surface peak/height parameters. The orthogonal shear stresses and Von Mises stresses at the shallowest depths under the surface have shown the highest correlations but no good correlations were found when the statistics of the whole stress fields was analyzed. The use of the new parameter offers a fast way to screen the durability of the contacting surfaces operating at similar conditions.

In order to choose the right manufacturing process in terms of costs and component performance, three differently manufactured surfaces were investigated: brushed, multiple shot-peened and phosphat ...

The possibility to reduce the amount of cutting fluids from machining processes is actively studied by the industrialists and researchers. Minimum quantity lubrication (MQL) is a solution toward cutting fluids reduction. This paper investigates the consequences on friction coefficient induced by the use of MQL. A tribometer is used in order to experimentally simulate the local tribological conditions encountered during machining. As the relative sliding speed increases, a lower amount of oil is deposited on the rough surfaces. Depending on the MQL operating conditions and sliding velocities, it is plausible to reach starvation by leaving the real rough contact partly dry. A model computing a starvation percentage by filling an estimated oil amount in a deformed topography correlates with the experimental results.

It is of a vital importance to reduce the frictional losses in the engines and hence the fuel/energy consumption. The major contributors to this are the oil control ring and cylinder liner interactions difficult to understand when comparing the experimental and theoretical results. The latter largely depend on the liner surface measurement and filtering type used in the simulations. Therefore, low-pass and high-pass filtrations were applied and the friction behaviors between the filtered liner surfaces and a perfectly flat ring surface were simulated for different engine speeds. The surfaces low-pass filtered by lower cutoffs showed higher friction, while the type of de-noising revealed about two and a half times higher friction. Stylus surfaces showed larger friction than the interference ones.

It is of a vital importance for automotive industry to reduce the frictional losses in internal combustion engines and hence their fuel consumption and CO2 emissions. The major contributors to this are the oil control ring (OCR) and cylinder liner interactions. These interactions are of complex multi-physics and multi-scale nature and many attempts have been made to improve the modelling and understanding of the phenomena involved. Even though continuous improvements have been made (see for ex. [1-3]), the form, waviness and roughness variation of real engineering surfaces still cause a large scatter in the results. The most of the models include measured liner surfaces, which are then filtered to capture the micro-effects of the roughness scale. However, by doing this, the contact conditions change (asperity contact distributes more evenly, see Fig. 1) such that the part of the boundary friction reduces and the part of the hydrodynamic friction increases accordingly for a given engine speed. This study focuses on one of these multi-scale problems, namely on how the 3D measurement type/size and filtering affects the predictions of friction between cylinder liner and OCR of truck engines. Two types of 3D liner surface measurements were investigated: (i) interference (with an objective of 2.5x, size of 2.5x3.3mm) and (ii) 4x8mm stylus measurement. The form was removed by fitting and subtracting a 2nd order polynomial and the waviness was filtered out by using a robust Gaussian filter with three different cutoffs: 2.5mm, 0.8mm and 0.25mm. The friction behaviours (i.e. the Friction Mean Effective Pressure-FMEP) between the primary/ filtered liner surfaces and a perfectly flat ring surface were then simulated for different engine speeds. The relative errors of the OCR’s FMEPs with respect to the primary surface were evaluated and results discussed.

The manufacturing and finishing (honing) of cylinder liners for the automotive industry is a constant challenge in order to reduce friction losses and oil consumption. A better knowledge of surfaces generated during plateau honing is then required for optimization of the process. Despite a well-known and controlled honing process, variations in surface roughness appear due to honing tool wear and need to be mapped and analyzed. The following paper proposes to map the variations in roughness by using confocal 3D measuring equipment able to inspect any area of a cylinder liner. Six motor blocks, each with five cylinder liners, were evaluated with 20 topography measurements per liner (giving six hundred 3D measurements in total). In addition to standard 3D roughness parameters, tailor made parameters extracting honing texture information are computed. The results show that only a few parameters (Spk, Ssc and Sk) do correlate with the honing tool wear specific to each cylinder. Tailor made parameters indicate similar results. Indeed, as the honing tool wears down, the cylinder liner surface gets rougher plateau or peaks and sharper asperities indicating that ploughing occurs instead of cutting. In future, experimental models could be built in order to perform production and functional optimizations.