Search

The effect of cylinder liners on engine performance is substantial. Typically, the cylinder surfaces were plateau honed. However, recently additional dimples or grooves were created on them. This work discusses the tribological impacts of textured cylinder liner surfaces based on a review of the literature. The results of the experimental research obtained using test rigs and fired engines were critically reviewed. In addition, the results of the modeling are shown. Circular oil pockets and grooves perpendicular to the sliding direction of piston rings of small depths were typically used. Surface texturing of the cylinder liners governs lubrication between the cylinder liner and the piston ring by an increase in oil film thickness near the reversal points leading to reductions in friction force and wear and in the fired engine to a decrease in fuel consumption and to an increase in power or torque. The correct texturing pattern ensures a decrease in the oil consumption, blow-by, and emissions of the internal combustion engine compared to plateau-honed surfaces. Considerations of future challenges are also addressed. The volume of lubricant reservoir in surface topography, called oil capacity, should be a substantial parameter characterizing textured surfaces. [ABSTRACT FROM AUTHOR]

Mechanical losses consume about 40% of the total energy developed by a typical automotive engine. The piston–cylinder system accounts for 50% of the engine frictional losses, of which 70% to 80% is attributed to the piston rings. Inadequate lubrication in the parts of the engine reduces the reliability of engines, since high wear, seizure, or catastrophic failure of the components may occur. Moreover, frictional losses adversely affect the economic use of fuel. Therefore, a marginal reduction in frictional losses enables economic fuel consumption and is a significant achievement. Of the various factors, the surface topography of the piston rings and cylinder liner dominates the lubricant flow between them and influences its tribological behaviour. Surface texturing, lubricant formulation, and lubricant additives have undergone significant technological advancements in recent times to satisfy the global requirements of reduced emission and improved fuel economy. One of the emerging technologies for significant improvement in the tribological properties of mechanical components is laser surface texturing. The precise control of the shape and size of the textures (dimples or grooves) and rapid processing rate makes laser surface texturing advantageous. This article reviews the theoretical and numerical methodologies developed to analyse the impact of surface texturing on the friction behaviour of piston ring–cylinder liner contact. In addition, the article presents future directions for the research work on improving the tribological performance of internal combustion engines. The present Part 1 of the article discusses the laser surface texturing process, and Part 2 reviews its use in piston ring–cylinder contact. [ABSTRACT FROM AUTHOR]

Laser surface texturing (LST) is widely explored for modifying the surface topography of various materials. In this study, a detailed investigation of laser textured surfaces produced on austenitic stainless steel (AISI 304) was carried out. Three different textures (square, parallel, perpendicular) were produced by a Ti sapphire laser. The processed surfaces were characterized by surface morphology, phase structure, microhardness, surface roughness, and wettability. A ball-on-disk tribometer was used to study the tribological performance of both untextured and textured samples. The experimental observations demonstrate that LST improves both surface wettability and surface roughness. Average surface roughness (Ra) was increased by 350% and the contact angle was reduced from 43° to 22°. The textured surfaces show a lower coefficient of friction and better wear resistance than the untextured surface. Out of the investigated patterns, the square textures exhibited a maximum reduction of 68% in the friction coefficient and a 50% lower wear rate. [ABSTRACT FROM AUTHOR]

This paper introduces a new paradigm of surface topography transition and its relation to the functional properties of stratified surfaces. These surfaces are generated by various machining processes that create the particular surface texture components. Therefore, these surfaces are also called multi-process or multifunctional surfaces, because each surface texture component plays a different function. Additionally, during the exploitation period, the wear processes occur. These processes cause the phenomenon of topography transition, which changes the surface features and affects their tribological properties. It is important to understand how surface topography features change due to these processes and how they influence performance aspects. It is also important to understand how these changes and properties can be measured, in order to improve the process of quality control and analysis of functional characteristics. Stratified surfaces with three Gaussian components of the height distribution, such as the surface texture of the cylinder liner after use, are analysed. A new paradigm based on the new mathematical model of the Material Probability Curve (MPC) is proposed to describe and predict the surface transitional transformations and their consequences on the functional properties. The results of the analysis of cylinder liner surfaces are presented on the basis of this model. These results show that this new MPC model effectively characterises the surface topography changes and provides tribologically important information. The adjusted R square value in each case showed that the three-Gaussian model of MPC better fit the MPC of that surface texture than the two-Gaussian model of MPC. The average adjusted R2 for the three-Gaussian model was 0.997564, while for the two-Gaussian model it was 0.980234. This means that this value was closer to 1 for the three-Gaussian model and therefore this model was more accurate for describing the MPC. Additionally, it was found that the two-Gaussian model of MPC overstates values (by 50% on average) for the standard deviation in the plateau part than the three-Gaussian model. The two-Gaussian model cannot distinguish the two Gaussian components that are present in the valley region, so it tries to find their average value. On the other hand, the three-Gaussian model of MPC enables us to identify and analyse in detail the specific Gaussian components in each surface texture area. The model can also provide useful information for controlling the machining and wear processes and improving the quality and reliability of the stratified surfaces; as well as describe the surface topography transition and its relation to the functional properties more accurately than the existing two-Gaussian MPC model. [ABSTRACT FROM AUTHOR]

This numerical study predicted wear of lubricated total knee replacements with the existing of textured surface and the possibility of surface designs to reduce wear. In the first part, a wear model of metal-on-polyethylene total knee replacement was developed. The medial and lateral knee compartments was accounted for separately, with the contact force and motion during walking cycles applied. An adapted Archard wear formula was employed where the wear factor was an exponential function of the ‘Lambda ratio’ (film thickness to the average roughness). Wear of the soft bearing surface (polyethylene insert) was simulated with regularly geometry update until a steady-state wear observed. In the second part, the effect of surface topography of the knee replacements was investigated. The surface texturing techniques have shown promising benefit to machine components in many areas of engineering practice. The texture parameters were designed using the Taguchi method for the geometry, size, and distribution of the micro dimples. It was observed that the lateral compartment may benefit from surface texturing if dimples were properly designed, while the texturing showed hardly advantageous effect on the medial surface in terms of lubrication enhancement and wear reduction. Some results were presented in the 6th World Tribology Conference.

The frictional capacity of rubber-tired metros decreases over time under the action of metro traffic. It is well known that the texture of rolling tracks contributes to evacuate water from the tire/track interface and generate friction forces. There is then a need to understand the evolution under traffic of the texture of rolling tracks to optimize their maintenance in terms of surface texturing. This paper investigates the friction and wear of steel rolling tracks subjected to laboratory polishing tests. Specimens are extracted from real metro tracks. Different initial textures obtained from different initial treatments of the surfaces are studied. Polishing and friction measurements are performed. During the polishing process, the surface topographies are measured at different polishing states and functional volumes and texture descriptors evaluated. Results show that the surface asperity's height and sharpness decrease with the number of polishing cycles. Also, the wear characterized by the difference in terms of material volumes between the initial and polished states, increases with the polishing duration. This evolution is composed of two phases corresponding respectively to transient and stationary wear. The evolution of wear volume during the stationary phase is in agreement with Archard's wear law. Tight correlation is found between friction and wear volume. [ABSTRACT FROM AUTHOR]

Various micro-scale surface texturing techniques have been used to control surface topography; however, conventional protocols are inherently difficult to adapt in large surface area applications. Micro-scale material removal methods based on superimposed tool modulation offer advantages for overcoming this challenge through direct-write processing. In this study, the ability to prescribe micro-scale textures of controlled size and morphology by control of underlying process parameters in vibration/modulation-assisted machining is demonstrated. Novel surface textures including protrusions (ribs and fins) and depressions (dimples) were generated, and corresponding geometric surface models were developed. The tribological performance of dimple-type textures was characterized by lubricated ball-on-flat wear testing. The dimple-type surface textures resulted in a substantial reduction in wear factor for two material systems, brass and an aluminum alloy. The effect of the texturing process on surface and subsurface microstructure was measured using electron microscopy. Heterogeneities in crystallographic texture and grain size along the textured surface were linked to local variations in machining conditions during surface generation. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is characterised by several unique advantages, such as (freedom of) design, capability of fusing dissimilar materials, near-net-shape, and achieving a more sustainable production. While the increased precision of metal AM in recent years reduced the needed amount of post-processing to meet dimensional tolerance, the requirements for functional surfaces necessitate a well-understood post-processing, ranging from heat treatment to machining and finishing. The inherently rough initial (as-built) surface topography next to complex material microstructure affects the capability of post-processing/finishing operations to smooth the surface texture and obtain a favourable surface integrity. In this respect, a more fundamental understanding of the effects of material properties on post-processing/finishing is needed. Therefore, this review paper aims to establish the relationship between the characteristics of different AM technologies, microstructural properties of materials in as-built and heat-treated conditions, and the physical properties influencing the response of additively manufactured materials during post-processing/finishing operations. In particular, emphasis is placed on the physics-based understanding of how the microstructural characteristics of 316L, Ti6Al4V and Alloy 718 produced using the two principal technologies, Powder Bed Fusion (PBF) and Direct Energy Deposition (DED), influence their mechanical properties like tensile strengths, hardness and ductility. These properties are among the key factors influencing the response of material during post-processing/finishing operations involving material removal by shear deformation. This review paper also discusses the role of post-processing/finishing on fatigue performance, tribological behaviour and corrosion resistance of investigated AM materials. The paper summarises the state-of the art of post-processing/finishing operations and future research trends are highlighted. [Display omitted] • Physics-based description of the microstructure impact on tensile properties is presented. • The material-process-property relationship is discussed based on literature data. • Post-processing methods ranging from conventional machining to laser polishing are covered. • The microstructure impact on material response during post-processing is discussed. • The impact of post-processing on functional performance is reviewed. [ABSTRACT FROM AUTHOR]

Purpose - The purpose of this paper is to build a transient wear prediction model of surface topography of textured work roll, and then to investigate the wear performance of different original textured surfaces. The surface topography of steel sheets is one of the most important surface quality indexes, which is inherited from the textured work rolls in cold rolling. Surface topography of work roll is obviously changing in the cold rolling process. However, surface topography is difficult to measure in the industry production process. Design/methodology/approach - This paper presents a numerical approach to simulate the wear process based on the mixed lubrication model of cold rolling interface developed by Wilson and Sheu (Sheu and Wilson, 1994). It is assumed that wear takes place at locations where the surfaces are in direct contact, and the volume is removed by an abrasive particle which is an abstract concept based on the wear phenomenon of textured work roll. At each simulation cycle, the distribution of the contact pressure is calculated by the lubrication model. The material is removed by an abstract abrasive particle and the surface topography is modified correspondingly. The renewed surface topography is then used for the next cycle. Findings - Through comparative analysis, it can be found that the simulation results possess similar statistical characteristic with the measured data. A set of roughness parameters such as the amplitude, spacing and frequency-domain characteristics are introduced to analyze the wear performance of different textured surfaces. Numerical examples show that the surface topography has a significant effect on the wear performance of work roll in cold rolling. Originality/value - The proposed model can accurately predict the wear process of the surface topography in the cold rolling process, which provides the foundation for optimization of original surface topography of textured work roll. The model can also be considered as a tool applicable for research on control of the surface topography of steel strip in the cold rolling process. [ABSTRACT FROM AUTHOR]

Laser surface texturing is a powerful tool to fabricate functional surface textures, whereby their morphology and cross‐sectional profile greatly depend on laser parameters such as pulse duration and fluence. In this work, the authors fabricate well‐defined groove‐like textures on stainless steel by laser surface texturing using different pulse durations ranging from nano‐ to femtoseconds, while keeping structural parameters such as depth and periodicity fairly constant. By doing so, the influence of the pulse duration on the resulting cross‐sectional profile of the textures and its subsequent impact on the tribological response are assessed. Reciprocating ball‐on‐disk tests and computational fluid dynamic simulations with Abaqus are used to evaluate the tribological performance of the as‐fabricated textures. Their results demonstrate that the use of laser pulses with different pulse durations induce changes in the resulting cross‐sectional profiles with the formation of rims/bulges well as the occurrence of recast phenomena and debris accumulation for nanosecond laser pulses. Decreasing the pulse duration significantly reduces the heat affected zone and the thermal damage, as well as avoided the formation of rims/bulges. Reciprocating ball‐on‐disk tests demonstrated that the differences in the cross‐sectional profiles have a significant influence on friction and wear behavior of the textured surfaces. The tribological properties of surface textures fabricated with different laser pulse durations ranging from nano‐ to femtoseconds are investigated. The influence of the pulse duration on the textures' profile and its impact on the tribological response are assessed. Their results demonstrate that laser pulse duration has a significant influence on the topography of surface textures and thus the frictional response. [ABSTRACT FROM AUTHOR]