Running-in wear modeling of honed surface for combustion engine cylinder liners

The texture change during running-in alters the performance and efficiency of a tribo-mechanical system. During mass production of cylinder liners, a final finishing stage known as ‘‘plateau honing’’ is commonly added to reduce the running-in wear process of the liner surface. The majority of researchers think that this operation improves the engine efficiency and decreases oil consumption. It was believed that there are close links between the surface topography of honed cylinders change and their wear resistance during running-in. However, these interactions have not yet been established. Some running-in wear models were developed in the open literature to predict topographical surface changes without considering the running-in conditions. The present paper thus investigates the various aspects of the wear modeling that caused running- in problems in honed surfaces and its implications on ring-pack friction performance. To illustrate this, plateau honing experiments under different conditions were first carried out on an instrumented vertical honing machine. The plateau honing experiments characterize the surface modifications during running-in wear of cast-iron engine bores using advanced characterization method. Based on the experimental evidence, a running-in wear model was developed. Finally, a numerical extension of the developed model was applied to solve the Reynolds equation by taking into account the real surface topographies of the engine bore. This enables us to predict realistic friction performance within the cylinder ring-pack tribosystem

Mutual influence of cross hatch angle and superficial roughness of honed surfaces on friction in ring-pack tribo-system

The cylinder bore surface texture, widely produced by the honing technique, is an essential factor for a good engine performance (friction, oil consumption, running-in, wear etc.). This explains the improvement and development of various new honing techniques. These different honing processes generate surfaces with various texture features characteristics (roughness, valleys depth, cross hatch angle, etc.). This paper addresses a comparison of ring-pack friction for cylinder surfaces produced by plateau honing and helical slide honing. It takes in consideration the mutual effect of superficial plateau roughness amplitude and honing angle. A numerical model is developed to predict friction within the cylinder ring-pack system in mixed lubrication regime. The results show the effectiveness of helical slide honed surface texture in comparison to plateau honed bore surface

A Thermodynamic and experimental study of low-alloy steels after carbonitriding in a low-pressure atmosphere

The effect of the composition of two steels (B and 6MnCr5) on precipitation of undesirable phases (carbides, nitrides and carbonitrides) under thermochemical treatment (low-pressure or vacuum carbonitriding) is investigated. Metallographic and x-ray diffraction studies and thermodynamic computations are performed.BMI Fours Industriels, St. Quentin Fallavier, Franc

Smoothness and plateaudness contributions to the running-in friction and wear of stratified helical slide and plateau honed cylinder liners

Cylinder liner surface has a great influence on frictional and wear performances of combustion engines during the running-in period. Two surface texture anisotropies produced by plateau honing (PH) and helical slide honing (HSH) processes (which consist of 50° and 130° cross-hatched grooves, respectively) are commonly used in automotive industry for thermal combustion engine cylinder liners. They are generated by a three stages process. The first stage, rough honing, removes enough material to obtain the desired cylindricity. The second step, finish honing, generates the honed texture which consists of grooves with a specific cross-hatch angle. The third stage permits to reduce the surface peaks and therefore allows varying plateau superficial roughness amplitude. This paper is devoted to studying the influence of respectively smoothness and plateaudness on honed surface wear and friction performances during running-in. For that, HSH and PH textures are generated using different final honing stage durations in order to obtain different levels of surface peak clipping. Then, friction, wear and surface topography evolution were analyzed during running-in tests on a reciprocating ring-liner tribometer under mixed lubrication regime. The results show that the superficial surface roughness generated by helical slide honing has a very low contribution into friction. This is promising for the honing process optimization, in which the third stage can be significantly reduced or avoided

Tribological performances of elliptic and circular texture patterns produced by innovative honing process

Honing is a manufacturing process which uses friction and abrasion mechanisms at a reduced velocity to print a multiscale and anisotropic texture on the liner surface of automotive engines. It enables to enhance the functional performances of a ring-pack system. However, industrial honing basically generates cross-hatched rectilinear textures. This paper proposes new surface textures, generatedby an innovative honing prototype machine, with original patterns (circles and ellipses) at different size and aspect ratio. Then, the friction performances of each generated surface are evaluated using a reciprocating ring–liner tribometer and compared with industrial helical slide honed (HSH) texture. The results show that ellipse patterns oriented at ring sliding direction contribute the most to reduce the friction coefficient

Multi-scale analysis of the roughness effect on lubricated rough contact

Determining friction is as equally essential as determining the film thickness in the lubricated contact, and is an important research subject. Indeed, reduction of friction in the automotive industry is important for both the minimization of fuel consumption as well as the decrease in the emissions of greenhouse gases. However, the progress in friction reduction has been limited by the difficulty in understanding the mechanism of roughness effects on friction. It was observed that micro-surface geometry or roughness was one of the major factors that affected the friction coefficient. In the present study, a new methodology coupling the multi-scale decomposition of the surface and the prediction of the friction coefficient by numerical simulation was developed to understand the influence of the scale of roughness in the friction coefficient. In particular, the real surface decomposed in different roughness scale by multi-scale decomposition, based on ridgelets transform was used as input into the model. This model predicts the effect of scale on mixed elastohydroynamic point contact. The results indicate a good influence of the fine scale of surface roughness on the friction coefficient for full-film lubrication as well as a beginning of improvement for mixed lubrication

Impact of superficial surface texture anisotropy in helical slide and plateau honing on ring-pack performance

The improvement of environment efficiency of automotive internal combustion engine becomes a fundamental objective. The cylinder engine surface texture considerably influences the functional performances of the ring-pack tribo-system. These surfaces are obtained by honing process that was pioneered in the last decade. Several innovative honing techniques were developed resulting in new surface textures with different cross-hatch angle obtained after several stages: the rough and finish honing and final stage. The aim of this study is to investigate the effect of variable cross-hatch angle generated at a final stage. These measured obtained surfaces are measured by a 3D white light interferometer and used as input data of the numerical model to estimate the friction. The results show the importance of this ‘residual’ angle

A Thermodynamic and experimental study of low-alloy steels after carbonitriding in a low-pressure atmosphere

The effect of the composition of two steels (B and 6MnCr5) on precipitation of undesirable phases (carbides, nitrides and carbonitrides) under thermochemical treatment (low-pressure or vacuum carbonitriding) is investigated. Metallographic and x-ray diffraction studies and thermodynamic computations are performed.BMI Fours Industriels, St. Quentin Fallavier, Franc

Influence de l'échelle de rugosité sur le frottement dans les contacts lubrifiés

La réduction du frottement, de la consommation d'huile et la limitation des émissions de gaz à effet de serre sont les principaux objectifs de l'industrie automobile afin d'améliorer l'efficacité environnementale des moteurs de véhicules. Cette efficience énergétique passe par une fonctionnalisation de la surface de la chemise du tribosystème segment piston chemise, responsable d’environ 45% des pertes par frottement dans le moteur. La surface rodée et le segment du piston constituent donc un système tribologique qui influe sur la longévité du moteur. En général, la surface rodée est obtenue par une succession de procédé d’abrasion (rectification, rodage, polissage…) permettant de répondre aux fonctionnalités requises relatives à leur durabilité et leur fiabilité. Ces procédés utilisent des grains abrasifs de différentes tailles allant du plus grossier au plus fin générant ainsi une texture de surface multi-échelle. La texture ainsi générée affecte de manière significative la performance du triplet piston segment chemise (SPC), bien que les effets de la topographie n’est pas clairement comprise. Dans cette étude, une caractérisation avancée de la surface est utilisée pour étudier les effets d’échelle de rugosité dans les contacts lubrifiés. La topographie de surface est basée sur la décomposition de la surface en deux éléments: la rugosité superficielle (reliée au frottement et à l’usure) et les vallées (servant de réservoirs). Les résultats montrent une dépendance entre l’exposant d’Hölder et le frottement ainsi qu’une échelle critique inversant l’influence de la profondeur des vallées sur le frottement

Geotechnical and thermal analysis and complex impedance spectroscopy characterization of pure Moroccan bentonite material for civil engineering applications

Combined modulus and impedance spectra are employed in the present work to explore electrical inhomogeneity and carriers’ behaviors in a pure bentonite Moroccan clay based on equivalent circuit. It has been clearly observed that the electrical properties change due to the increase of temperature from 300 °C to 700 °C. The frequency-dependent imaginary modulus M" and imaginary impedance Z" curves has only one peak at each temperature indicating the predominance of the contribution of grains to the total electrical conduction in bentonite. The positions of these peaks move to higher frequencies when the temperature increases in relation with the distribution of relaxation time. Moreover, the activation energy for the conduction process in bentonite is determined from the slope of ln(ρdc) versus of 1/T in the order of 700 meV in good agreement with that obtained from the proposed equivalent circuit. On the other hand, let’s present a geotechnical study that show that our material is a swelling clay, very plastic and could be used as a binder. The external stress dependence of the bulk density, Young’s module and maximum stress are analysed. The thermal conductivity determined following the device of Lee's disks where two copper disks of thickness of 15 mm and diameter of 30 mm were use