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

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

Etude tribo-fonctionnelle des textures bas frottement des cylindres de moteurs générées par le procédé de rodage

Mechanical honing process is still the reference industrial process for high production engine liners. The current manufacturing way use reduced velocity friction and abrasion mechanisms to print a multiscale and anisotropic texture on the liner surface. The texture signature characteristics satisfy multifunctional requirements of the liner (friction, lubrication, wear, oil consumption etc.). It is generated by a stratified honing process for industrial production which consists of three stages with scale effect: rough (macroscopic scale), finish (mesoscopic scale) and super-finish honing (microscopic scale). Different honing methods emerged during last decade in which the technological and economic differentiation is essentially based on textural attributes of honed surfaces. The present study analyses the industrial honing processes, the possible surface anisotropy choices and texture parameters with a view to honed liner surface functionalisation. A methodological approach about multiscale honed surface tribofunctionality has been developed and then validated by numerical simulation in the case of ring-liner tribocontact. It builds on the following triptych:- the coupling between honing process and functionality through its multiscal textural signature,- the exploitation of the controlled anisotropy by numerical simulation which conducts to fonctionality,- the surface-process interaction which becomes indivisible, particularly in texture manufacturing and its tribofunctional qualification though tribometric trials.The methodology has been applied to industrial honing processes (plateau honing (PH), slide honing (SH) and helical slide honing (HSH)). The results show that smooth texture with lower plateau roughness and valley depth contributes to reduce frictional performances of honed surfaces. Nevertheless, Helical slide honed surfaces are less sensitive in friction to the plateaudness i.e., to superficial roughness comparatively to PH textures. This is promising for HSH process optimization, in which the third stage can be reduced or deleted. Then the developed approach has been extended to honing development for innovative texture anisotropy (circular, undulatory, mixed, trajectory assisted) for low-friction performances. The results show that assisted trajectory (without inversion grooves at top dead (TDC) and bottom dead centers (BDC)) and 45-130-45 mixed textures (with 45° cross-hatched grooves at TDC and BDC, 130° cross-hatched grooves at mid-height) enhance significantly frictional performances in comparison to HSH conventional process.Le rodage mécanique demeure encore le procédé industriel de référence pour la finition des cylindres de moteurs dans le cadre des productions de grande série. La voie actuelle de fabrication en rodage procède par frottement et abrasion à vitesse réduite pour imprimer une texture anisotrope et multi-échelle sur la surface du cylindre. La signature de cette texture a la particularité de satisfaire des exigences multifonctionnelles du cylindre (frottement, lubrification, usure, consommation d'huile, etc.). Elle est cependant générée par un rodage stratifié en production industrielle qui consiste en trois étapes successives avec effet d'échelle: ébauche (échelle macroscopique), finition (échelle mésoscopique) et superfinition (échelle microscopique). Plusieurs méthodes de rodage ont émergé cette dernière décennie et dont la différentiation technologique et économique se fait essentiellement par le choix des attributs texturaux et topographiques de surface de rodage. La présente étude analyse les processus de rodage industriel, du choix d'anisotropie possibles et paramètres texturaux dans une optique de fonctionnalisation de la surface rodée du cylindre. Une approche méthodologique sur la tribo-fonctionnalité multi-échelle de la surface de rodage du cylindre a été développée, puis validée par simulation numérique dans le cas du tribo-contact segment-cylindre. Elle s'appuie sur le triptyque suivant :- le couplage entre le processus de rodage et la fonctionnalité via la caractérisation de sa signature texturale multi-échelle,- l'exploitation de l'anisotropie contrôlée par simulation numérique qui conduit à la texture de fonction,- l'interaction surface – procédé de rodage qui devient indissociable, notamment dans la fabrication de la texture de fonction et sa qualification tribo-fonctionnelle par des essais tribométriques.Cette démarche méthodologique a été appliquée aux procédés de rodage industriel tel que le rodage plateau (PH), glissant (SH) et hélico-glissant (HSH). Cela a permis de démontrer qu'une texture anisotrope fine de type PH composée de plateaux et vallées de faible amplitude présente les meilleurs attributs fonctionnelles en frottement. Cependant, une texture anisotrope de type HSH avec un angle de striation de 130° est moins sensible en frottement à l'aspect plateau obtenu par écrêtage des pics de rugosité. Ce résultat ouvre une évolution potentielle du process HSH où la dernière étape de rodage peut être réduite voire supprimée. Par la suite, la démarche développée a été étendue aux textures innovantes à bas frottement de rodage en développement avec une anisotropie circulaire, ondulatoire, stratifiée mixte, ou assistée en trajectoire. Les résultats ont montré que des textures HSH optimisées en trajectoire (avec suppression de stries d'inversion au niveau des points mort haut (PMH) et point mort bas (PMB) du cylindre) ainsi que des textures stratifiées mixtes 45°-130°-45° (stries à 45° au PMB et PMH et 130° au milieu du cylindre) permettent une réduction significative du frottement segment-fût en régime de lubrification mixte en comparaison par rapport au texture de rodage HSH conventionnel

Effect of Low-Temperature Plasma Jet on Thermal Stability and Physical Structure of Type I Collagen

This work is devoted to the characterization of type I collagen treated by a low-temperature plasma jet generated in ambient air to determine whether the resulting fibrous material is structurally preserved or reinforced. The physical structure of collagen is checked by differential scanning calorimetry (DSC), which is a well suited technique to analyze thermal transitions in proteins, such as denaturation. DSC is used to evaluate the thermal stability of collagen after the plasma treatments while Fourier transform infra red spectroscopy is used to check the integrity of triple helical domain and to investigate the effects of plasma treatments on the functional groups of collagen. It is more particularly shown that the plasma treatment can stabilize the collagen structure without altering the triple helical structure. This observation is supported by 1) the shift observed toward high-temperature range of the collagen denaturation and 2) the stiffening of the chains by a cross-linking action when compared to the control sample

Study of Formation and Decay of Rare-Gas Excimers by Laser- Induced Fluorescence

The aim of this chapter is to review the experimental and numerical techniques for the estimation of the laser-induced fluorescence (LIF) decay in rare gases using time-correlated single-photon counting. The advantages of single-photon counting technique are discussed by means of measurement uncertainty analysis. In addition, this chapter provides information concerning the application of this technique to filamentary dielectric barrier discharges (DBD) and radiation trapping of the resonant transitions

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