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The cylinder liners’ surface is really important in an engine because it corresponds with piston rings to a tribologic system indispensable to know for reasons of wear, of oil consumption and engine’s life time. For these reasons, it is important to measure and characterize these surfaces. The first part of the project is the observation of the impact of the number of strokes of the plateau honing on the surface of the cylinder liners. It is interesting to observe the impact of the variation of the number of strokes of the plateau honing on the peaks, plateaus and valleys of the surface. The second part of the project is the simulation of the oil flow on the surface to observe the links between the roughness parameters and the oil flow and the shear stress. The results are interesting, we will observe that the number of strokes of honing as a good impact on the quality of the surface. In the second part of the project, the results show a correlation between the machining parameters and the roughness and functional parameters. It could be interesting to mix the two parts of the project to see the correlation among machining, roughness and functional parameters for the samples made in the first of the project.

The cylinder liners surface is of major importance in an engine since it interacts with the piston rings and creates a tribologic system. This tribologic system has to be qualified and controlled in order to understand and control wear, oil consumption and shelf life. In this purpose, a program has been created in order to analyze SEM pictures and from them qualify the surface. The aim of the project presented here has been to improve the preliminary steps leading to the image computation by standardizing the picture acquisition and improve the image filtering.

The demands on decreased environmental impact from vehicles force the automotive industry to develop engines with reduced engine oil and fuel consumption. Engine oil consumption is recognized to be a significant source of pollutant emissions. Unburned or partially burned oil in the exhaust gases contribute directly to hydrocarbon and particulate emissions. Engine oil and fuel consumption are to a great extend controlled by the topography of the cylinder liner surface. Recent engine tests have shown a promising reduction in oil consumption when using cylinder liners with a smoother finish than the current plateau honing. One approach to produce smoother liner surfaces is to replace SiC ceramic honing stones with diamond tools. However, event though the diamond honing process results in higher productivity, improved demands of quality control is needed to monitor the degree of cold worked material - “blechmantel” (German), and the resulting risk of increased wear and scuffing. A number of petrol and diesel engine cylinder liners have been mapped to be able to verify the quality and consequences, in terms of wear and function, of the honing process. A new mapping method, combining SEM images and quantitative image analysis with traditional 2D profilometry has been developed and tested in this study. The liners where tested in a reciprocating rig of 8 mm stroke and with a frequency of 10 Hz, simulating the top-dead center conditions in a running engine. The tests where carried out in high- and low pressure conditions with smooth respectively rough liner roughnesses against PVD coated piston rings. The developed surface mapping method was employed before and after the test to study effect of running-in wear on the surface, features characterized with the SEM- and the 2D profilometer. The results show that combining SEM- and profilometric methods gives a good picture of the effects of varying the cylinder liner pressure and roughness. The roughness of the core decreases more for diesel liners than for petrol liners. In average (rough and smooth liners) the diesel core roughness decreases 265% while the petrol liners average on a 60% decrease. Blechmantel- and Irregularities ratio show a high sensitivity to varying conditions and decrease 1180% to 100% for the diesel liners while the parameters increase between 106% to 18% for all the petrol liners. A probable cause is the more severe diesel high pressure run-in conditions are able to effectively “truncate” the plateaux and remove residing plastically deformed un-cut honing residues while the less severe petrol liner conditions not manage to remove the blechmantel and irregularities in an important extent.

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