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Reducing engine oil and fuel consumptions by multidimensional laser surface texturing on cylinder surface
Abstract
The optimization of cylinder surface topography draws immense amounts of researches, since it has far-reaching effects on engines’ overall performances. In order to promote the lubricity of ring/bore interface, the present study developed the multidimensional laser surface texturing (MLST) process, which fabricates controllable arrays of micro dimples on cylinder surface. The MLST process was achieved by a series of innovations, including its hardware and software systems, and optimization of process parameters and efficiency. A post-process was developed based on the finishing honing process to remove the recast bulges (RCB) induced by laser ablation. Additionally, the cylinder liners with different surface texturing schemes were bench tested on a single cylinder diesel engine. The experimental results indicated that near TDC (top dead center) region and piston skirt contacting region (SKIRT) were two high-impact regions for the technical efficiency of the MLST process. Benefiting from the reasonable optimization of oil distribution and enhanced hydrodynamic lubrication, the MLST process was able to reduce engine oil and fuel consumptions simultaneously. This paper provides a comprehensive introduction of equipment, pre- and post-process, and capacities of the newly developed surface modification technology.
... Ergen et al. [43] obtained smaller oil consumption by creating oval oil pockets only near the reverse point. The authors of the articles [44,45] obtained similar findings. Hua et al. [44] studied the effect of discriminating partition laser texturing on engine performance. ...
... Hua et al. [44] studied the effect of discriminating partition laser texturing on engine performance. Kang et al. [45] textured various cylinder regions. Partial surface texturing caused a lower oil consumption and blow-by than the texturing of the entire cylinder liner surface. ...
... Then, the optimal pa ern of the oil pockets should be searched to decrease the fuel and oil consumptions. In [43][44][45], the pit area ratio near the top dead center was higher than in the middle part of the cylinder liner surface. Wos et al. [46] found that friction reduction due to surface texturing was larger at smaller temperatures, compared to work at higher temperatures. ...
During co-action between contact elements in reciprocating motion, different working conditions exist in outer and inner zones of stationary elements. Because the tribological effects of surface texturing depend on the operating conditions, various dimple patterns were created in the middle part of the steel disc and near the reversal points. The behaviors of variable dimple patterns were compared with those of uniform texturing and untexturing. It was found that the dimple patterns in the middle disc zone depended on the resistance to motion. The best tribological behavior was obtained for a pit area ratio of 13% and diameter of 0.4 mm in the inner zone, and pit area ratio of 3% and diameter of 0.2 mm in the outer zones. Low resistance to motion and the smallest friction variation of all tested sliding pairs were achieved. For the same pit area ratio of 13% in a disc of 0.4 mm, the dimple diameter behaved better than in the 0.2 mm diameter disc. The greatest decrease in the coefficient of friction of 85% compared to untextured sliding pair was achieved for uniform laser texturing with a pit area ratio of 13% and dimple diameter of 0.4 mm, when the normal load was 40 N and frequency of displacement was 20 Hz.
... The highest decrease in fuel consumption (up to 5%) was achieved for surface LST-3, which was recommended. Similar results were reported in [117]. However, in [116,117] the oil capacities of textured and untextured surfaces were not compared. ...
... Similar results were reported in [117]. However, in [116,117] the oil capacities of textured and untextured surfaces were not compared. Information that the surface before texturing was subjected to additional honing to reduce the height of the roughness is substantial [117]. ...
... However, in [116,117] the oil capacities of textured and untextured surfaces were not compared. Information that the surface before texturing was subjected to additional honing to reduce the height of the roughness is substantial [117]. ...
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.
... A number of published works show that texturing can improve tribological behaviour of materials [1,2,[6][7][8][9]. In case of dry friction, several mechanisms can stay behind an enhancement: textured cavities act as reservoir for additional lubricants [2,10,11], and textured cavities collect abrasive wear debris removing it from direct tribocontact [12,13]. ...
... Moreover, Kang et al. investigated the influence of laser-fabricated dimples with a typical depth of 8 µm near the top dead centre (TDC) and the piston skirt contacting region. Their findings highlighted improved hydrodynamic lubrication with reduced engine oil and fuel consumption [7]. Furthermore, Xu et al. studied the effect of larger dimples (500 µm diameter, 2-3 µm depth) produced by electrochemical mask etching and smaller dimples (70-80 µm diameter and 5-7 µm depth) fabricated by laser surface texturing on a) the barrel-shaped ring liner pair, b) the taper-faced ring liner pair, and c) the oil control ring liner pair. ...
Applying texture to a surface in a tribological interface will influence frictional performance, which has been investigated in several previous studies. However, since varying operating conditions heavily affect the frictional performance and optimum texture dimensions, more work in this field is required. There are few experimental studies concerning the influence of texture on friction especially under sliding lubricated conditions and even fewer at high sliding speeds. In this work, the effect of texture on frictional losses between the piston ring and cylinder liner is studied experimentally. The texture is of the dimple type, with a diameter and depth of 300 µm and 3 µm, respectively, applied to the cylinder liner surface. Experiments are performed with sliding speeds close to real piston sliding speeds. A clear reduction in frictional losses is observed with the textured cylinder liner. Moreover, qualitatively comparing the experimental results to a numerical model shows a good correlation.
... Textured surfaces are known to be effective in reducing actual contact area, trapping wear debris, mitigating wear, acting as a reservoir, preventing lubricant starvation, and producing hydrodynamic effects [5][6][7]. Surface texturing technology has a promising application in mechanical manufacturing, medicine, micro-nano electromechanical systems (MEMS/ NEMS), and new energy [8][9][10]. ...
Surface texturing is a potential approach to achieving excellent surface performance. To realize high precision and efficiency in micro-texturing fabrication, a surface texturing method utilizing an ultrasonic surface rolling process is proposed. Firstly, the feasibility and geometric controllability of micro-texture preparation using ultrasonic surface rolling process are analyzed. Then, a contact theory model of ultrasonic rolling texturing process is established, which can describe the geometric relationship of the micro-texturing generation region. Based on the elastic–plastic theory, simulations of single-pass and multi-pass ultrasonic rolling texturing processes are developed to elucidate the formation and strengthening mechanism of micro-textures, and further characterize the effects of ultrasonic rolling machining parameters on micro-textures. A series of validation tests of ultrasonic rolling texturing are implemented on AISI 5140 steel. Simulation and experimental results show that the ultrasonic surface rolling process can fabricate micro-groove arrays with the periodic distribution. The validity of the theoretical and finite element models is confirmed by the comparison results. It is demonstrated that the ultrasonic rolling texturing process is a feasible and efficient way to fabricate controllable micro-textures.
... Textured surfaces are known to be effective in reducing actual contact area, trapping wear debris, mitigating wear, acting as a reservoir, preventing lubricant starvation, and producing hydrodynamic effects [5][6][7]. Surface texturing technology has a promising application in mechanical manufacturing, medicine, micro-nano electromechanical systems (MEMS/NEMS), and new energy [8][9][10]. ...
Surface texturing is a potential approach to achieving excellent surface performance. To realize high precision and efficiency in micro-texturing fabrication, a surface texturing method utilizing an ultrasonic surface rolling process is proposed. Firstly, the feasibility and geometric controllability of micro-texture preparation using ultrasonic surface rolling process are analyzed. Then a contact theory model of ultrasonic rolling texturing process is established, which can describe the geometric relationship of the micro-texturing generation region. Based on the elastic-plastic theory, simulations of single-pass and multi-pass ultrasonic rolling texturing processes are developed to elucidate the formation and strengthening mechanism of micro-textures, and further characterize the effects of ultrasonic rolling machining parameters on micro-textures. A series of validation tests of ultrasonic rolling texturing are implemented on AISI 5140 steel. Simulation and experimental results show that the ultrasonic surface rolling process can fabricate micro-groove arrays with the periodic distribution. The validity of the theoretical and finite element models is confirmed by the comparison results. It is demonstrated that the ultrasonic rolling texturing process is a feasible and efficient way to fabricate controllable micro-textures.
... Optimising the surfaces of friction pairs is the main approach to improve the tribological performance and reliability of internal combustion engines (ICEs). 1 As the most important component, the PRCL system is a main source of friction loss, [2][3][4] and its scuffing failure is related to the reliability of the engine, so the optimization of the PRCL system surfaces has been the focus of research. Existing researches show that a smooth cylinder liner surface is not conducive to lubricating oil storage and is more likely to cause scuffing failure. ...
The oil storage effect of textures is beneficial for lubrication performance under starved lubrication. When the larger of the two surfaces in friction pairs is textured, the moving textures should be considered because the boundary conditions are transiently changed at each moment. This is especially for the cross-hatched textures, which are manufactured on the cylinder liner while not on the piston ring. However, it means that the calculation cost will be very expensive for engineering friction pairs because the required calculation scale is very large and the required time step is very small. So the dynamic characteristics of moving textures on engineering surfaces are normally neglected in the existing researches. In this study, a starved lubrication model of the piston ring-cylinder liner (PRCL) system is established considering the oil storage effect, local hydrodynamic effect and dynamic characteristics of the moving cross-hatched textures. To speed up the calculation, an efficient parallel algorithm is developed. The results show that there is a significant difference in minimum oil film thickness (MOFT), wear load and oil film boundaries between stationary textures and moving textures, so the moving textures should not be simplified. This is helpful to find a better design of textures for engineering friction pairs. K E Y W O R D S cross-hatched texture, moving texture, parallel computing, piston ring-cylinder liner, starved lubrication
... Anderberg et al. [8,9] proved that oil consumption is also affected by the surface topography of the cylinder liner. Recently, Koszela et al. [10,11], Tomanik [12], Brinkman and Bodschwinna [13], Kang et al. [14] and Yin et al. [15] combined honing with additional surface texturing, depending on the creation of separated dimples. Therefore, it is possible to reduce the fuel/oil consumption and emissions of IC engines by improving the finishing process of cylinder liner surfaces. ...
The surface of cylinder liner is tribologically important. In most cases, it has a two-process cross-hatched structure created by the plateau honing process. Because the surface topography of cylinder liners is complicated, its analysis is challenging. Special methods have been used to analyse the textures. In this article, first, the parameters in the standard are reviewed. Next, the methods for selecting the reference elements are presented. Other comprehensive methods of cylinder surface analysis are described. Finally, methods of cylinder texture modelling are analysed.
The tribological performance of internal combustion engines (ICEs) has an important impact on fuel efficiency and power consumption, and the wear of cylinder liner-piston ring (CLPR) system affects the operation reliability. The surface texture of CLPR can significantly improve the tribological performance of ICEs. Aiming at the friction and wear of CLPR, the different textures (dimple, equilateral triangle and square) are generated on the CLPR using laser processing, and the different tests are conducted on the UMT-TriboLab tester. The coefficient of friction, wear topography, surface roughness parameters and profiles are measured. The results show that, compared with the non-textured surface, the dimple texture surface of piston ring or cylinder liner has better tribological performance. If the textures coexist on the cylinder liner and piston ring, the tribological performances are better than single surface texture. Furthermore, the mixed textures can significantly improve the surface lubrication performance and the ability to store abrasive particles, and better surface quality can be obtained at the same operating conditions to enhance the tribological performance. This study can provide guidance for reducing the friction and wear of CLPR system of ICEs, and achieve energy saving and emission reduction of ICEs.
In tribology, bio-inspired surface textures are a potentially significant area of investigation and have achieved excellent success in past practice. In this study, a texture was designed that can be applied to cylinder liner-piston rings (CL-PR) as a solution for enhancing tribological properties, with reference to the microstructure of ventral snake scales. Three different sizes of bionic textures were processed on CL surfaces by laser surface texturing. Then, a reciprocating friction test machine was used to examine the influence of these textures on the tribological behavior of CL-PRs. A single speed (100 rpm) and three loads (200, 400, and 600 N) were applied. The experimental results showed that the combination of dentate structures and dimples in the artificial texture, mimicking snake ventral scales, could achieve enhanced lubrication. The adoption of these textures reduced the friction coefficient up to 35%. Interestingly, there was a violent interaction between the PR and the CL texture, which was sufficient to change the surface structure of the PR. This effect produced additional friction and reduced the degree of influence of oil film thickness on the friction coefficient. This study provided a reference for the application of friction reduction through texture for CL-PRs in diesel engines. It was simultaneously informative for future in-depth studies of bionic textures.KeywordsBionic surface textureVentral scales of snakeCylinder liner-piston ringTribological propertiesSurface reconstruction
New kite-shaped textures are designed in this paper to improve the lubrication performance of tribological systems under hydrodynamic lubrication. Moreover, pressure distribution and load-carrying capacity of the kite-shaped textures under fixed working conditions are solved using Reynolds' equation based on the form of mass conservation. Lastly, the influence of kite-shaped textures on the friction coefficient under different geometric parameters is investigated. Moreover, a double-layer composite kite-shaped texture is designed, and the influence of parameters on lubrication performance is investigated. Numerical simulations and experiments are used to find the optimal parameters and effectively reduce the friction coefficient, thus providing a reference for reducing frictional wear in mechanical systems under full-film oil lubrication conditions.
Partially surface texturing is a promising technology to improve the performance of thrust pad bearing. Moreover, how to design the distribution parameters of local textures is a crucial issue of the amelioration of lubrication and anti-friction. Hence, the synergistic effect of micro dimples’ distribution parameters was systematically investigated by numerical and experimental approaches. The textured region area ratio (TRAR) was defined to analyze the synergy of radial and circumferential parameters. Then, a series of frictional tests were conducted with different positions and proportions. The results showed that the CPP and RPP directly determined the efficacy of the ‘equivalent Rayleigh step’ which could enhance the cumulative response of hydrodynamic lubrication. Meanwhile, there was an optimal TRAR (about 0.8) according to the favorable fitting curve with R Square (R ² ) being 0.9013. And circumferential proportion parameter (CPP) and radial proportion parameter (RPP) exhibit an interactive relationship which was dependent on the optimal TRAR. On the other hand, for generating the ‘inlet roughness’ and ‘open pocket’, the circumferential location parameter (CLP) of local textures needed to keep close to the inlet without consideration of the radial location parameter (RLP) due to the negligible influence.
Failures in moving parts of mechanical systems can be mitigated or eliminated using appropriate lubricants. While conventional fossil-derived mineral oil-based lubricants have served the mechanical industry for this purpose for over a century, increasingly stringent environmental norms have tended to incentivize eco-friendly and biodegradable base oil additives for lubrication. In this chapter, we have first compared the tribological efficacy of fossil-based and bio-based base stocks (petroleum-derived mineral oils and naturally occurring tree-borne oils) utilizing a combined approach of experimental simulations and molecular modeling to demonstrate that polar end groups in the case of a tree-borne oil-derived lubricant interact strongly with, diffuse slowly from and adsorb efficiently over the substrate, thereby providing superior tribo-performance as compare to fossil derived when compared to mineral oil based lubricants. Having established this point, we then reviewed the extensive literature on using such esters of naturally occurring tree-borne oils. We observed that polyol esters of fatty acids dominate the application landscape. In such lubricant esters, every oxygen atom present is part of an ester linkage. This raises the question of whether other oxygen atom environments, such as ether linkages, could enhance bio-derived lubricants’ performance in specific applications.
The purpose of this work is to study the effect of oil pocket shape and density on friction in reciprocating sliding. The experiments were conducted in reciprocating motion under starved lubrication conditions. Tribological tests were performed using an Optimol SRV5 tribotester. The frictional pair consisted of two discs of 42CrMo4 steel. One disc was laser textured. The oil pockets had circular and sandglass shapes. Disc samples of various texture shapes were characterized by the same pit-area ratios. The operating parameters were the same for all friction pairs. In most cases, surface texturing led to reductions in friction force value and scatter. For both dimple shapes, the best tribological properties were achieved for oil pocket density of 9%. When discs with circular dimples were tested, the highest resistance to motion was received for the highest pit-area ratio of 9%. On the contrary, the worst tribological performance of discs with sandglass-shaped oil pockets of sandglass shape were obtained for the largest oil pocket density of 22%.
The micro-textures fabricated on the substrate surface of coating are a feasible method to improve the interfacial adhesion of the coating. This research proposes an ultrasonic rolling texturing method, and for the first time reveals how different ultrasonic rolling texturing process parameters (including air pressure, step distance, and feed speed) impact the bonding properties of AlTiN coating. The texture profile, surface morphology, hardness, elasticity modulus, and surface stress state are investigated. Then, the scratch tests are implemented to study the adhesion properties of these textured AlTiN coatings. Results showed that periodic micro-grooves were controllably fabricated, accompanied by high compressive stress and increased surface energy on AISI 5140 steel surface by ultrasonic rolling texturing. The surface morphologies and mechanical properties of the textured surface were strongly dependent on the texturing parameters. And the ultrasonic rolling textured substrate was conducive to the coatings in terms of interfacial contact area, wettability, surface energy, hardness, and residual stress, which could enhance the interfacial adhesion of the coating-substrate. The critical failure loading force of all textured coatings (FN = 43-59.35 N) exhibited higher value in comparison with the polished coating (FN = 37.91 N), demonstrating that ultrasonic rolling texturing presented a great potential in the fabrication of high precision micro-textures for enhancing the interfacial bonding properties of coatings. Furthermore, the enhancement mechanism for the ultrasonic rolling texturing on the AlTiN coating adhesion was discussed. The developed texturing method supports the application of hard coatings on mechanical parts such as molds, bearings, etc.
The protection of polymeric coatings by adapting self-healing mechanisms is a promising strategy in the field of green tribology. Therefore, self-healing can be seen as a subject of several review articles. However, there is no study expressly dedicated to the working mechanism of different functional components (capsules, inorganic nano-fillers) embedded in the coatings. In this article we classified the coating based on the working principle of functional components for a better understanding. Further, the content of this article includes comparisons of different established techniques in self-healing. We also counted the modifications to the established techniques performed by researchers over a period of the last two decades (2000–2020). Additionally, details and working of microscopic techniques used for the analysis of coating are included as well.
The aim of the present study was to develop novel antibacterial touch surfaces through the laser texturing optimization of stainless steel. A wide range of laser fluence (2.11 J/cm²–5.64 J/cm²) and scanning interval (10 µm–30 μm) parameters were explored. The impact of surfaces with different patterns, wettability, and oxidation states on the antimicrobial behavior of Escherichia coli K-12 and biofilm hyper-producing Acinetobacter baumannii MAR002 was assessed. Modification of laser input enacted topographical changes with high scanning intervals leading to ordered surface patterns, while increasing the laser fluence to 5.64 J/cm² created larger and less ordered plateaus and valleys. Texturing also drove a transition from a hydrophilic starting surface with a contact angle of 80.67° ± 3.35° to hydrophobic (138°–148°). Antimicrobial analysis and bioluminescence assays of E. coli, alongside biofilm forming test through A. baumannii MAR002 indicated the ability of laser texturing to produce effective bactericidal touch surfaces. No simple correlation was found between wettability and bacterial behavior, revealing that proliferation is dependent on roughness, oxidation, and wettability. For the conditions selected in this study, a laser fluence of 5.64 J/cm² and a scanning interval of 10 µm showcased the lowest amount of recovered bacteria after 30 min.
In the field of journal bearings, the microtexture processing technology of the bush inner surface has become an effective way to improve the performance of journal bearing. The two-dimensional finite element model of microtexture surface with different shapes of friction pairs is established based on the Navier–Stokes (N-S) equation, and the effect of lubrication conditions on the frictional performance of friction pairs is analyzed. Four microtextures that are radial grooves, circular pits, local reticulation, and circumferential grooved microtexture are processed by laser microcarving on the surface of specimen, and three different lubricating medium conditions are set up with high-viscosity oil, low-viscosity oil, and oil–solid mixture, and the effect of lubrication condition and texture shape on the wear reduction of the microtexture friction pair is studied. Results show that the concave microtexture and the radial groove can improve effectively the friction performance of the friction pair. The microtexture can effectively store the lubricating medium and wear abrasive particles in the mixed lubrication, and avoid effectively the second wear, and its average friction coefficient of radial groove microtexture is 22%, 30% lower than that of high- and low-viscosity lubricating media, respectively. Both theory and experiment have proved that the effect of microtexture on high-viscosity lubricant is better than that of low-viscosity lubricant.
A reduction in frictional loss is an important aspect of efficiency in high-performance internal combustion engines. This can be achieved by the well-designed surface texturing of the cylinder bore, which can reduce friction at the ring/bore interface. In this work, dimples were created using plastic deformation on the cylinder surfaces of high-performance motorcycle engines. Prior to texturing, these cylinders had Nikasil coating. One cylinder was subjected to the deposition of DLC coating and then surface texturing. The results of the functional performance of internal combustion engines with textured cylinder surfaces were compared to untextured ones. The engine performance was analysed in terms of maximum power and maximum torque output. The results showed that cylinder surface texturing improved the functional properties of internal combustion engines. The maximum power increased by up to 5.8%. Best performance was achieved for internal combustion engines with textured cylinders and DLC coating. Such surface modification allows the powering of the motorbike with higher maximum speed and provides better vehicle dynamics at high speeds.
To clarify the correlation between the wettability and friction coefficient, the wettability and friction properties of four different laser-induced surface textures on cemented carbide surface were evaluated in this study using droplet angle measuring meter and pin-on-disc reciprocating tribometer. The fluid used was dilute cutting fluid of volume ratio 1:40 emulsified oil to water. The four textures investigated were orthogonal arrays of circular and square dimples and convex. Results suggest a coupled effect of texture shape and area ratio on surface contact angle. A strong correlation between friction coefficient and surface wettability was also found. Friction coefficient decreases with the decrease in contact angle of the textured cemented carbide surface and the increase in delta wettability (Δθ = θwball–θwdisc) between two sliding surfaces in dilute cutting fluid. This finding indicates that the wettability of cemented carbide surface have significant effect on friction coefficient in dilute cutting fluid condition.
Surface texturing was widely applied in improving the tribological properties of mechanical components, but study of measurement of this technology was still insufficient. This study proposed the multi-layers fitting (MLF) method to characterise the dimples array texture surface. Based on the synergistic effect among the dimples, the 3D morphology of texture surface was rebuilt by 2D stylus profiler in the MLF method. The feasible regions of texture patterns and sensitive parameters were confirmed by non-linear programming, and the processing software of MLF method was developed based on the Matlab®. The characterisation parameters system of dimples was defined mathematically, and the accuracy of MLF method was investigated by comparison experiment. The surface texture specimens were made by laser surface texturing technology, in which high consistency of dimples’ size and distribution was achieved. Then, 2D profiles of different dimples were captured by employing Hommel-T1000 stylus profiler, and the data were further processed by MLF software to rebuild 3D morphology of single dimple. The experiment results indicated that the MLF characterisation results were similar to those of Wyko T1100, the white light interference microscope. It was also found that the stability of MLF characterisation results highly depended on the number of captured cross-sections.
The dimensions, area densities, and geometry of macroscale surface textures may affect the performance of hydrodynamic lubrication interface. Reported in this paper are the investigations of the effect of surface textures bottom shapes on the friction forces between piston ring and cylinder liner for two-stroke marine diesel engine, using numerically generated textures and average Reynolds equation. These textures are on the cylinder liner surface in the form of circumferential oil grooves with different aspect ratios and different area densities. The hydrodynamic pressure distribution is also calculated using Reynolds boundary condition. The results revealed that the bottom shape could positively affect the friction between moving surfaces, as it could provide a microwedge or microstep bearing that tends to enhance the lubrication condition between piston ring and cylinder liner.
Surface texturing has emerged in the last decade as a viable option of surface engineering resulting in significant improvement in load capacity, wear resistance, friction coefficient etc. of tribological mechanical components. Various techniques can be employed for surface texturing but Laser Surface Texturing (LST) is probably the most advanced so far. LST produces a very large number of micro-dimples on the surface and each of these micro-dimples can serve either as a micro-hydrodynamic bearing in cases of full or mixed lubrication, a micro-reservoir for lubricant in cases of starved lubrication conditions, or a micro-trap for wear debris in either lubricated or dry sliding. The present paper reviews the current effort being made world wide on surface texturing in general and on laser surface texturing in particular. It presents the state of the art in LST and the potential of this technology in various lubricated applications like mechanical seals, piston rings and thrust bearings. The paper also describes some fundamental on going research around the world with LST.
Significant improvement in load capacity, wear resistance, friction coefficient etc. of tribological mechanical components can be obtained by forming regular micro-surface structure in the form of micro-dimples on their surfaces. A feasibility study was performed both theoretically and experimentally using the Laser Surface Texturing (LST) technique to produce the micro-dimples. Each micro-dimple can serve either as a micro-hydrodynamic bearing in cases of full or mixed lubrication or as a micro-reservoir for lubricant in cases of starved lubrication conditions. Theoretical models were developed, and laboratory tests were performed, to investigate the potential of LST in tribological components like mechanical seals, piston rings and thrust bearings. In the entire laboratory tests, friction was substantially reduced with LST compared to the non-textured components.
The bonding of thermal-sprayed coatings largely depends on the substrate surface morphology. This study examines the effect of the substrate surface texture shapes on the adhesion strength of coatings. For that, it used plasma-sprayed Ni-based MoS2 coatings deposited on grit-blasted and laser-textured surfaces, and investigated the coating bonding strength (ASTM 633 pull-off test), and cross-sectional and fracture morphologies, as well as phase compositions and element distribution. The results showed that the surface texture shape has a significant effect on the improvement of coating adhesion. The coatings deposited on sinusoidal-textured surfaces had the highest adhesion strength (50.0 MPa), followed by coatings deposited on groove-textured surfaces, while dimple and dimple–groove textures resulted in the lowest coating adhesion strength. The coating fracture analysis revealed that cohesive failure occurred mainly at the texture positions, while adhesive failure occurred almost always in plain areas. Therefore, it could be concluded that, in the conditions of this study, the existence of plain areas and dimple textures did not improve coating adhesion. Factors such as coating bond mode, contact area ratio, and coating deposition quality should be comprehensively considered in texture design to improve coating adhesion.
The aim of this study was to investigate regulated and unregulated emissions including particulates generated from a gasoline direct injection engine with different oil formulations. Lubricating oil analysis was also performed with focusing on both viscosity and soot-in-oil morphology. According to the Euro-6 regulation, the standard for particle mass emissions of a gasoline engine is 0.005 g/km (6.0× 10¹¹ N/km for particle number). Lubricant oil accounts for a considerable fraction of the particulate volatile fraction. In this study, intentional oil consumption together with different compositions of additives were investigated based on engine dynamometer tests. Regulated (PM, THC) and unregulated (VOCs) emissions were measured corresponding to the different level (baseline, Disp-1.5, Disp-3.0 and Wear-1.5) in lubricant additive formulations. Subsequently, the role of dispersant additives was observed and discussed in terms of additive interaction. Among the test cases, viscosity difference were distinctively observed both in fresh oil and soot (carbon black) containing oil. Higher dispersant level yielded an increase in viscosity of bulk oil, which is consistent with the previous study reported regarding diesel engines. Soot-in-oil morphology was also studied focused on the difference from diesel. The associated higher viscosity of the lubricating oil (Disp-3.0) is considered to yield more inhomogeneity of air-fuel mixtures, which finally results in more soot mass relative to Disp-1.5. engine cases.
This paper presents a novel electrochemical processing technique, mask electrolyte jet machining (MEJM), for the fabrication of surface microstructures. MEJM combines jet electrochemical micromachining (Jet-ECM) and through-mask electrochemical micromachining (TMEMM), combining the advantages of TMEMM, which is a high-throughput process, and of Jet-ECM, with its adjustable flow field. The effects of a mobile nozzle on electrolyte flow are investigated, and a new modeling approach for large translational movements is proposed. An analysis of the accuracy and reliability of the proposed method is presented. Microprotrusions and microdimples are produced to high precision and with excellent consistency of dimensional variation (maximum standard deviation 2.171 μm). The results suggest the possibility of an affordable technique for batch fabrication of surface microstructures with high efficiency and precision.
Sequential honing process is usually implemented in engine cylinder bore processing to obtain the cross-hatched surface texture with excellent function to balance lubricant storage capacities and supporting performance. Many researches have devoted to correlating honed surface quality of cylinder bore with honing process parameters by means of experiments or simulations. Quite a few efforts have addressed the effect of sequential multiple steps on the surface texture in the honing of engine cylinder bore. However, these researches cannot provide an explicit and analytical methodology to predict honed surface texture efficiently and accurately. This paper presents an analytical and explicit methodology to incorporate a proposed microscale abrasive model into the analytical simulation process of sequential honing. The proposed abrasive model synthetically considers the shape, size, posture, and position of abrasives randomly distributed in honing stone, which is incorporated into honing head motions in terms of rotation, oscillation and feeding. The kinematics of honing head is calculated by space-time discretization to capture the interaction between honing stones and cylinder bore surface. The above procedure acts as each single step for the sequential honing processes. This study investigates the sequential honing of two stages including semi-finish honing and plateau honing at different feeding speeds by applying the abrasive model with different abrasive sizes. The formation of cross-hatched surface texture was successfully achieved sequentially by semi-finish honing and plateaus honing. Then the Abbott-Firestone Curve of the honed surface can be obtained to analyze the influences of abrasive size and honing time of two stages on the surface roughness. Correctness of surface roughness predicted by the model is verified by comparing with a group of experiment measurements in terms of Abbott-Firestone Curve. Most errors of all the predicted Rk roughness family roughness parameters in the two honing stages are less than 15%. Based on the model, simulations are done to analyze the influences of abrasive size and honing duration time of two stages on the surface roughness. The result shows that the larger abrasive used in finish honing leads to the decrease of the material portions Mr1, Mr2 and the increase of the reduced valley depth Rvk. The longer plateau honing duration time is preferred to produce the larger Mr1, Mr2 and the smaller Rvk.
In this research, the influences of milling parameters on the surface quality and coat adhesion of rigid polyurethane (PU) foam are highlighted. Several surface texture parameters were correlated with the milling parameters. The correlation between the coat adhesion strength, as determined by the pull-off test, and the milling parameters was also established. The investigation revealed that traditional height distribution roughness parameters, such as Ra , Sa , Rz , and Sz , do not offer sufficient information for a proper surface adhesion evaluation. Shaping and bearing surface parameters, on the contrary, provide more information for the surface quality assessment, although the structure of the PU was found to be inhomogeneous. The evaluation of milling process effects on surface texture and coat adhesion and the determination of optimal machining conditions were derived based on response surface methodology. The goal was an adequate surface texture that provides the best coat adhesion strength.
Piston cylinder kinematic pair is the most critical of all the pairs in an Engine contributing to 70% of the engine friction. The piston cylinder tribo-pair wears unevenly due to varying normal pressure. Major Piston rings fail to expand in to this elliptical gap on the major thrust of the engine. This paper proposes a method of regaining compression in an old engine by laser surface texturing (LST) of the piston skirt major thrust side. The engine with textured piston showed 60% improvement in compression, regaining the engine performance and fuel efficiency. The increased compression showed secondary benefits with reduction in HC and CO emissions. The piston slap noise has reduced by the retained oil film reducing the engine sound by 8 decibels. The engine oil consumption was significantly reduced from 65ml/1000 to 25ml/1000.
The tribological performance of piston ring-cylinder bore was investigated through deterministic mixed-lubrication modeling. Bore topographies measured from regular honed Grey Cast Iron (GCI) to “Mirror-Like” coated bore surfaces were used in the investigation. In contrast with typical honed GCI bores composed of relatively well-distributed peaks and valleys, coated bores are composed of a much smoother plateau and localized deep pores. Simulation results indicated that coated bore surfaces generate significantly higher hydrodynamic pressure and lower asperity contacts when compared with regular GCI topographies. The influence of roughness filtering and the associated cut-offs values were also considered in the analysis, showing that the choice of cut-off affects both the predicted hydrodynamic and asperity contact pressures. Furthermore, the simulation results also revealed that most of the fluid pressure was generated by the honing grooves rather than by the localized pores present on coated bore surfaces.
The influence of laser scan speed during nitriding in the range 30–150 cm min⁻¹ on the physical properties, microstructure and corrosion behaviour of Ti6Al4V was studied. The surface energy of nitrided Ti6Al4V remained almost constant up to the scan speed of 60 cm min⁻¹ followed by an increase in the maximum value at 80 cm min⁻¹. A gradual drop in the microhardness of the coating from the outermost surface was noticed for specimens nitrided up to 80 cm min⁻¹; an abrupt decrease, however, was found at a scan speed ≥100 cm min⁻¹. The laser nitriding produced dendritic microstructure; an exponential decay in the secondary dendrite arm spacing (SDAS) with the increase in laser scan speed was revealed. The SDAS produced was smaller at the interphase and centre of the coating, compared to that at outermost surface. The passivation behaviour of Ti6Al4V at lower potentials shifted to the smaller current side after laser nitriding.
It has recently been shown that rectangular surface pockets are effective in reducing friction in a piston-liner type contact, providing they are oriented with their long axis transverse to the sliding direction so that entrained features fit completely within the contact area (1, 2). The aim of the current study was to identify the optimal geometric parameters of theses rectangular features. To do this, a friction rig that simulated a piston-liner contact under highly controlled conditions was used to test a series of textured specimens with pockets of different depth, breadth and density. Each of these geometric parameters was varied and tested independently, while keeping the other two constant. Experimental conditions were set in order to place the contact in different lubrication regimes.
Results were analysed to determine a set of criteria for the optimum pocket geometry, however, this was shown to change depending on the test conditions and should therefore be adjusted depending on the position along the stroke. Specifically, at low speed when the contact is operating under boundary lubrication, pockets should be deep, wide and densely spaced. This confirms recent findings, which suggested that, in this regime, pocket volume is often a more critical parameter than depth, width, or spacing individually. Conversely, under mixed lubrication towards the transition to the full film regime, pockets should be narrow and sparsely spaced. These results also explain the difficulties encountered in several previous studies that attempted to define a single optimum pocket geometry.
Finally, the impact of pocket position relative to reversal was assessed for various lubrication conditions. This revealed how pockets should be placed close to, but not directly at, top and bottom dead centre so as to provide a beneficial squeeze film, which is present at reversal.
Laser nitriding is known to be an effective method to improve the surface hardness and wear resistance of titanium and its alloys. However, the process requires a gas chamber and this greatly limits the practicability for treating orthopaedic implants which involve complex-shaped parts or curved surfaces, such as the tapered surface in a femoral stem or the ball-shaped surface in a femoral head. To tackle this problem, a direct laser nitriding process in open atmosphere was performed on commercially pure titanium (grade 2, TiG2) and Ti6Al4V alloy (grade 5, TiG5) using a continuous-wave (CW) fibre laser. The effects of varying process parameters, for instance laser power and nitrogen pressure on the surface quality, namely discolouration were quantified using ImageJ analysis. The optimised process parameters to produce the gold-coloured nitride surfaces were also identified: 40 W (laser power), 25 mm/s (scanning speed), 1.5 mm (standoff distance) and 5 bar (N2 pressure). Particularly, N2 pressure at 5 bar was found to be the threshold above which significant discolouration will occur. The surface morphology, composition, microstructure, micro-hardness, and tribological properties, particularly hydrodynamic size distribution of wear debris, were carefully characterized and compared. The experimental results showed that TiG2 and TiG5 reacted differently with the laser radiation at 1.06 μm wavelength in laser nitriding as evidenced by substantial differences in the microstructure, and surface colour and morphology. Furthermore, both friction and wear properties were strongly affected by the hardness and microstructure of titanium samples and direct laser nitriding led to substantial improvements in their wear resistant properties. Between the two types of titanium samples, bare TiG2 showed higher friction forces and wear rates, but this trend was reversed after laser nitriding treatments.
The cylinder liner surface finish, which is commonly produced using the honing technique, is an essential factor of engine performance. The characteristics of the texture features, including the cross-hatch angle, the plateau roughness and the groove depth, significantly affect the performance of the ring pack–cylinder liner system. However, due to the influence of the honed texture features, the surface roughness of the liner is not subject to Gaussian distribution. To simulate the mixed lubrication performance of the ring–liner system with non-Gaussian roughness, the combination of a two-scale homogenization technique and a deterministic asperities contact method is adopted. In this study, a one-dimensional homogenized mixed lubrication model is established to study the influence of groove parameters on the load-carrying capacity and the frictional performance of the piston ring–liner system. The ring profile, plateau roughness, and operating conditions are taken into consideration. The main findings are that for nonflat ring, shallow and wide groove textures are beneficial for friction reduction, and there exists an optimum groove density that makes the friction minimum; for flat ring, wide and sparse grooves help improving the tribological performance, and there exists an optimum groove depth that makes the friction minimum.
Reducing fuel consumption in automotive engines is a key enabler for CO2 emission reduction. Tribology plays a significant role in reducing parasitic losses in an engine and thus reducing fuel consumption. The paper reviews frictional losses in critical engine components and the lubrication regime(s) they operate. This reveals the opportunities for friction reduction at cylinder bore/piston contact, valvetrain, and bearings through deposition of low friction coatings, improved surface finish, surface modifications, and low friction engine oil. The paper also attempted to capture implementation of some of these friction reduction concepts in recent engines.
This study mainly focuses on oil consumption behavior of laser textured cylinder bores. The results of an experimental study performed on a six cylinder, 9.0 L capacity diesel engine is presented. The engine has Compacted Graphite Iron (CGI) cylinder block, and parent bore power cylinder design. Both an instantaneous oil consumption measurement method, sulfur-tracing, and a conventional oil consumption measurement method, drain and weigh, are used in determining the effects of different laser texture parameters at different running conditions. Oil consumption measurement results with the conventional plateau honed surface in comparison with the laser honed surface are also discussed.
Laser surface texturing (LST) technique was utilised on a cylinder liner in a diesel engine. In order to analyse the effect of LST micro-dimples on the lubrication and friction properties of cylinder liner–piston ring (CL–PR), we developed a new mixed lubrication model on the basis of the average Reynolds equation and asperity contacts equation. The model can consider the coupling effects between the surface roughness of non-texturing regions and micro-dimples and the synergistic effects of multi-micro-dimples. The results show that cylinder liner surface by LST can form effective hydrodynamic lubrication effect in most regions of the strokes, only near the dead points, the friction pair is in mixed lubrication state, asperity contact plays a major role in balancing the external load and the asperity friction force is obvious. The micro-dimple parameters were optimised to obtain a better lubrication effect with the following optimised results: rp = 30–60 µm, Sp = 0.2–0.4 and e = 0.03–0.1. Copyright © 2012 John Wiley & Sons, Ltd.
Experiments were carried out on a reciprocating tester. The lubricant was supplied into the inlet side of the contact zone. The construction of tribological tester allows to measure the friction force between specimen and counter-specimen. Tribological behaviours of cylinder liners with and without oil pockets were compared. Specimens were cut from plateau honed cylinder liners made of grey cast iron. Counter-specimens were cut from grey cast iron piston rings. A special tool acted as a hammer to form additional dimples on the liner surfaces. The area density of oil pockets was about 13%. Specimen surfaces had dimples with average depths about 5 μm and diameters in the range 0.15–0.2 mm. Two batches of tribological tests were carried out, in regimes of full and starved lubrication. Friction tests were conducted at three mean sliding speeds: 0.44, 0.66 and 0.88 m/s. Experiments were performed with normal load in the range 50–300 N, starting from the lowest load. Normal load increased in a stepwise manner after 2 min at each load, until the maximum load was reached. Areal surface topographies of specimens and counter-specimens were measured before and after two batches of tests by white light interferometer.
In this paper, based on the Reynolds equation and the dynamic operation conditions of cylinder liner and piston ring of CY6102 type diesel engine, a theoretical model of the load carrying capacity and film thickness for the first compressed ring were developed. Based on the theoretical models, the effects of the texturing parameters on the load carrying capacity and film thickness were investigated under different velocities, and the ranges of optimum texturing parameters were found. An optimal texturing design method on cylinder liner was proposed. It shows that on cylinder liner, texturing with variable parameters in different velocity ranges can produce higher load carrying capacity and film thickness than that with invariable parameters.
The dependence of ablation rate of aluminium, titanium and copper on the nanosecond laser fluence at 532 nm and, respectively, 1064nm wavelengths is investigated in atmospheric air. The wavelength is varied by exchanging the fundamental and second harmonic modules of a Q-switched Nd-YAG laser system, while the fluence of the pulses is varied by changing the diameter of the irradiated area at the target surface. The results indicate an approximately logarithmic increase of the ablation rate with fluence for both wavelengths, and an approximately double ablation rate in the case of visible pulses as compare to infrared pulses. By extrapolating the ablation rate vs. fluence fitting curve toward zero, we estimate the ablation threshold fluence, Fth. The ablation threshold fluence is strongly dependent on the wavelength and target material. Thus, Fth in the case of infrared pulses is twice as large as Fth corresponding to the visible pulses, while Fth is lower for the aluminium and titanium as compared to the copper. A different behavior occurs in the case of copper, for which we obtained a two times smaller Fth when using infrared pulses comparative with the visible pulses.
In this study, the influence of surface wettability (θ) and interfacial energy (γ) on the coefficient of friction (f) of tribopair surfaces in aqueous environment was investigated using a tribotester. The wettability behaviour of various tribopair surfaces [hydrophilic (HL) and hydrophobic (HB)]: (HL–HL), (HB–HB) and (HB–HL) was characterized by friction properties in water and aqueous two-phase lubricants (water + additive). The results show that the level of wettability of the tribopairs [the so-called delta wettability, Δθ = (θDisc − θPin)] is related to friction coefficient (f) in aqueous environment. In view of recent results, we conclude that both the interfacial energy and wettability of tribopair surfaces adequately characterize the lubrication processes.
This paper describes future trends in surface metrology. Measurement techniques are briefly mentioned. A special attention was paid to tactile and optical methods. Selected problems of surface topography characterization are described. The effects of sampling and filtering on surface topography representation are analysed. Structured surfaces are becoming both technologically and economically critical. Therefore their description is a problem of a great practical importance. Multi-process textures are very important from functional point of view. Various methods of their description are compared. Surface texturing as a means for enhancing tribological properties of frictional pairs started to be extremely popular from for about last 10 years. The effects of surface texturing on improving tribological properties of sliding assemblies are analysed. The other influences of surface topography are mentioned in this paper.
Reciprocating piston engines are the major propulsion devices for light aircrafts, helicopters, and essentially all automotive
vehicles. They are expected to fulfil both present-day and future demands for engine performance, durability, fuel economy,
and exhaust emissions legislation. One of the key factors related to these demands is the need to the limit thermomechanical
internal losses, wear, and lubricating oil consumption, which are in turn conditioned by the tribological behavior of the
piston–cylinder assembly. Consequently, this latter system requires a multi-directional approach in terms of manufacturing.
Apart from various modifying techniques (e.g. laser texturing), a conventional plateau-honing operation is still the standard
technology for shaping cylinder liner surface microstructure. This paper describes the distinctions between variations in
the performance of the engines in relation to cylinder liner roughness parameters due to different honing settings. Five air-cooled
reciprocating aircraft engines (FRANKLIN 4A-235-B31) served as the objects of research. The engines passed durability tests
on the dynamometer bed, including operation under artificially intensified wear conditions. The results show a significant
impact of the brand-new honed cylinder liner surface microstructure on the engine output parameters. Detailed study proves
that some of the cylinder liner roughness parameters, specifically, the slope of the root mean square line (RMS) for valley
roughness Rvq and the linear triangle area for valleys A2, are strongly correlated with the engine operational properties. Higher values of Rvq and A2 are associated with an improvement in engine performance but result in a deterioration in the exhaust harmful emission.
KeywordsGasoline internal combustion engine–Engine performance–Plateau honing–Piston–cylinder assembly–Cylinder liner–Surface roughness–Abrasive wear–Tribological behavior
A simple technique for in situ measurements of pulsed Gaussian-beam spot sizes is reported. This technique is particularly useful for measurements on highly focused beam spots. It can also be used for absolute calibration of the threshold-energy fluences for pulsed-laser-induced effects. The thresholds for several effects in picosecondlaser-induced phase transformation on silicon-crystal surfaces are calibrated with this technique.
New technologies of honing
- Klink