Search

The effects of surface-texture technology on the friction and lubrication mechanism of cylinder liner-piston rings (CLPR) were explored in this study. An inclined groove texture was machined on the CL of a S195 diesel engine and dimples designed on the gas ring. Friction and wear tests of nontextured (NT), CL textured (CLT), and PR textured (PRT) conditions were performed on a CLTR friction and wear tester under different temperatures. First, the characteristics of friction and lubrication at different temperatures were analyzed by examining friction and contact resistance. Then, the wear characteristics were analyzed by examining surface morphology parameters of the CL and the PR wear mass after testing. Finally, the friction and lubrication mechanisms of NT, CLT, and PRT were studied by analyses of real-time friction and contact resistance in one cycle. The results showed that, under the same temperature, CLT and PRT increased oil film thickness, improved the lubrication state, and reduced friction, with CLT better than PRT in these respects. With increased temperature, the wear degree of CL liners became larger. The existence of surface texture reduced CL wear, yielded CL surface morphology not excessively changed by temperature, and improved its supporting performance and oil storage capacity. The inlet suction effect, structural effect, micro-wedge action, balancing wedge action, squeezing effect, and cavitation effect should be taken into account together when exploring the mechanism of the influence of surface texture on friction pairs. This study provided a method for scholars to explore the friction and lubrication mechanism of different texture types and provided an experimental basis for improving the performance of CLPR friction pairs. [ABSTRACT FROM AUTHOR]

The running-in of cylinder liner-piston rings (CLPRs) is the most important process that must be performed before a marine diesel engine can be operated. The quality of running-in directly affects the reliability of a CLPR. The surface texture of a CLPR has been proven to significantly affect its lubrication performance. In this study, the tribological behavior of a CLPR during running-in is investigated. Three types of surface textures are generated on the CLPR via laser processing: dimple texture on piston rings, groove texture on cylinder liners, and co-texture on both sides. Subsequently, a series of tests are performed on a slice tester. A load of 300 N (1.64 MPa) is applied, and two speeds (50 and 100 rpm) are adopted. The CLPR running-in quality is characterized based on three parameters, i.e., the friction coefficient, contact resistance, and wear topography. Experimental results show that, compared with a non-textured surface, the three types of surface textures mentioned above improved the friction performance during running-in. The lubricant supply capacity of the dimple texture on the piston ring, as a mobile oil reservoir, is stronger than that of the groove texture on the cylinder liner serving as a static oil reservoir. By contrast, the wear resistance of the dimple texture, as a movable debris trap on the piston ring, is weaker than that of the groove texture on the cylinder liner, which serves as a static debris trap. It is demonstrated that the co-texture combines the advantages of dimples and groove textures. Compared with non-textured surfaces, the friction coefficient decreased the most at 100 rpm (44.5%), and the contact resistance improved the most at 50 rpm (352.9%). The coupling effect provides the surface with improved running-in quality by optimizing the tribological performance, particularly at the dead center. This study provides guidance for the tribological design and manufacturing of CLPR in marine diesel engines. [ABSTRACT FROM AUTHOR]

Abstract In this reported study, 12 types of spherical convex surface textured thermoplastic polyurethanes (TPU) samples were produced using 3D printing technology to determine if these surfaces could improve the performance and service life of water-lubricated bearings. The wear process of the TPU/QSn7-0.2 friction pairs was analyzed using a specially designed testing apparatus under water-lubricated conditions. As part of the analysis, the friction coefficient, surface topographies, grinding marks and the wear mass from the worn specimens were examined. The analysis results showed that the spherical convex texture effectively improved the tribological properties of the TPU material. The friction coefficients between the friction pair were directly related to the test rotation speed and applied loads. Abrasive wear and adhesive wear were found to be the major wear mechanisms of the non-texture specimen, while the spherical-convex textures appeared to facilitate the removal of friction pair debris from the surfaces, reduced the adhesion between the friction pairs and strengthened the wedge effect and cavitation effects of the water flow. Compared to the non-texture samples, the 1/3 spherical texture samples with an S = 38% exhibited improved tribological properties, and the friction coefficient of these samples was decreased by 64.47% at 0.7 MPa and 250 rpm. These results provide an experimental foundation for the textured design and optimization of the water-lubricated TPU bearing surface. Highlights • The spherical convex texture effectively improved the tribological performance of TPU water-lubricated bearing material. • A wedge gap formed between the spherical convex texture and a QSn7-0.2 disc was helpful in forming a local high-pressure water-film. • Cavitation effects produced between adjacent convex bodies during the wear process improved the lubrication performance. [ABSTRACT FROM AUTHOR]

As one important supporting component of the ship propulsion system, the water-lubricated stern tube bearing has profound effects on navigation safety. One the other hand, it is difficult to ensure the adequate lubrication for water-lubricated stern tube bearing under low speed working conditions. In order to mitigate this problem, contemporary bearing systems have been built of Ultra-High Molecular Weight Polyethylene (UHMWPE). However, it is observed that material surface texture features have a significant impact on the lubrication effectiveness. In this research, three types of micro convex textures such as cuboid structure were designed and surfaces of UHMWPE samples were moulded. A series of experimental tests were then carried out in a specially designed tester to investigate the tribological characteristics of different convex texture designs. Comparative analyses were conducted on friction coefficients, wear mass losses and worn surfaces for different convex textures and running conditions. Analysis results showed that there are significant differences in tribological properties of rubbing pairs with different convex textures. The variations of the friction coefficient of convex textured samples are less than the original sample. The wear performance of the convex textured design is superior to that of other convex textures. The convex textured is the most effective design in improving wear properties at a low sliding velocity of 0.063 m/s. This work has established a practical basis for optimal texture design, of water-lubricated material, for reduced wear and improved lubrication performance. • Three convex textures were designed and processed on the surface of UHMWPE sample. • The dimension parameters of convex texture and running condition had the great influence to the tribological performance of rubbing pairs. • The rubbing pairs of cube textured UHMWPE / QSn7-0.2 copper was more suitable for the low-speed conditions. [ABSTRACT FROM AUTHOR]

Surface groove width is of great significance to the performance of the cylinder liner–piston ring (CLPR) with the different surface textures in marine diesel. However, little is understood about the specific application (e.g., the geometric parameters of surface textures and operating conditions) of surface texture in actual marine diesel engines. To address this issue, different surface groove textures including grooves structures with 1-, 2-, 3-, and 4-mm widths were designed based on previous results related to marine diesel engine applications. A series of experimental tests was conducted in a reciprocation tester, and data on the friction characteristics were obtained under different operating conditions. Comparative studies on the friction coefficients, worn surface features, and oil film characteristics were performed. Results showed that the 2-mm groove structure of the cylinder liner was more favorable for improving the wear performances at low speed, whereas a 3-mm groove structure of the cylinder liner was more suitable for improving the wear performance at higher speeds, though its wear performance needs to be improved under high load. These results help to understand the specific application of surface texture on the wear performance of the CLPR pair. [ABSTRACT FROM AUTHOR]

Abstract The ultra-high molecular weight polyethylene (UHMWPE) has become one of the most popular and reliable material for water-lubricated bearings in recent years. In this study, three kinds of new Koch snowflake textures were designed on the surface of the UHMWPE to try to decrease friction and prolong the service life of the bearings. The wear process of the UHMWPE/QSn7-0.2 rubbing pair was analyzed using a specially designed tester under water-lubricated conditions. The analysis results demonstrated the testing velocity and load significantly affected the friction coefficient of the UHMWPE specimens. The UHMWPE specimen without texture-treatment had higher friction coefficient than that of the textured UHMWPE specimens at high velocity, where the maximum rate of increase was 35.2% at the velocity of 350r/min compared with non-texture. The dominant wear mechanism was abrasive wear and slight adhesive wear for the non-texture UHMWPE sample, and the wear mechanism of textured samples was slight abrasive wear. The wear performance of the UHMWPE with composite texture was superior to that of other textures, which was mainly attributed to the micro hydrodynamic bearing effect and stepped bearing effect. As a result, the findings of this work can provide experimental foundation for texture design and optimization on UHMWPE surfaces for better service of the marine water-lubricated bearings. Highlights • The UHMWPE specimen without texture-treatment had higher friction coefficient than that of the textured UHMWPE specimens at high velocity, where the maximum rate of increase was 35.2% at the velocity of 350r/min compared with non-texture. • The dominant wear mechanism was abrasive wear and slight adhesive wear for the non-texture UHMWPE sample, and the wear mechanism of textured samples was slight abrasive wear. The dominant wear mechanism was abrasive wear and slight adhesive wear for the non-texture UHMWPE sample, and the wear mechanism of textured samples was slight abrasive wear. • The wear performance of the UHMWPE with composite texture was superior to that of other textures, which was mainly attributed to the micro hydrodynamic bearing effect and stepped bearing effect. [ABSTRACT FROM AUTHOR]

Purpose Water-lubricated bearings can significantly reduce the pollution to environment because the traditional oil lubricant is replaced by water in the bearings. The ultrahigh molecular weight polyethylene (UHMWPE) has proven to be effective and reliable for the manufacturing of water-lubricated bearings. However, limited work has been done to address the improvement of the tribological performance of the UHMWPE-based water-lubricated bearings using surface texture processing. This paper aims to investigate the effects of bar-grooved surface on the tribological performance improvement of UHMWPE-based water-lubricated bearings.Design/methodology/approach For the first time, the bar grooves were processed on the surfaces of UHMWPE-based water-lubricated bearings. The CBZ-1 friction and wear tester have been used to test the wear and friction performance of the bearing samples. The LI laser interference surface contour graph and the digital microscope have been used to measure the surface morphology of the specimens. The tribological characteristics of the tested bearings were analyzed.Findings With bar grooves added on the surfaces of the specimens, the friction coefficient of the specimens were lower than that of the specimens without surface texture processing; the wear quantity of the two kinds of specimens were almost the same; by using the LI laser interference surface contour graph and the digital microscope to measure the surface morphology of the specimens, the furrows of the specimens with bar grooves were narrower and shallower than that of the specimens without bar grooves.Practical implications The paper implicates that the surface texture processing using bar grooves can reduce the friction coefficient and prolong the service life of the water-lubricated bearings in practical applications.Originality/value This paper fulfills an identified need to provide important theoretical and experimental support to the design of water-lubricated bearings in practical applications. [ABSTRACT FROM AUTHOR]

The hydrodynamic lubrication effect and cavitation effect caused by these micro-convex textures endow the composite with excellent tribological properties, and the micro-convex textures will not disappear completely with the friction process. B Inside Cover b : In article number 2100844 by Zhiwei Guo and co-workers, a hydrophilic composite consisting of thermoplastic polyurethane (TPU) and polyvinyl alcohol (PVA) fibers is designed, which can spontaneously produce many micron-level micro-convex textures on the surface when immersed in water for a period of time. A Novel Finding of Tribological and Mechanical Linking to Micro-Convex Texture on Hydrophilic Composites Surface under Water-Lubricating Conditions. [Extracted from the article]

Wear particle analysis can be developed as an effective method for assessment of the running conditions of concaved cylinder liners. The aim of this study was to numerically characterize the topographical features of wear particles generated from different surface textured cylinder liners and to investigate their changes with alternations in both rotational speeds and surface textures. To achieve this goal, cylinder liners with three different surface textures were prepared and tested in four different speeds. In addition to an untreated surface, concave cylinder liner surfaces with two different diameters (1 and 2 mm) and two different depths (200 and 300 μm) were investigated. Wear particles were extracted from the lubrication oil; three-dimensional images of the wear debris were acquired using laser confocal microscopy; and their topographical features were analyzed quantitatively. This study has revealed that running-in conditions and stable state can be detected using wear debris analysis techniques at a micrometer scale. It has also been discovered that concave B cylinder liner with a depth-diameter ratio of 0.1 always generated wear particles different to those from the other two cylinder liners on each rotational speed. It is believed that the quantitative surface topography characterization results obtained in this study provide a practical base for developing a new, non-intrusive tool for monitoring the operation conditions of cylinder liner-piston rings in diesel engines. [ABSTRACT FROM AUTHOR]

Water-lubricated bearings are essential parts of marine propulsion systems. However, severe friction and wear of water-lubricated bearings usually occur under marine running conditions. Surface texture technology has been verified as an effective method for improving material tribological properties and been successfully applied in many fields. Here, the effects of surface spherical-platform texture parameters on the tribological performance of water-lubricated bearings were investigated using 9 types of spherical-platform textured high density polyethylene (HDPE) specimens, manufactured using 3D printer technology. Two groups of tests with different applied loads and rotational speeds were performed to simulate low-speed and heavy-load conditions of water-lubricated bearings. By analyzing the friction coefficient, wear mass loss, and surface topography, spherical-platform textures were concluded to have had a positive effect on the tribological performance of water-lubricated bearings. Specimens with 1/2 spherical-platform texture showed the best ability to promote the wedge-shaped effect and cavitation effect of lubrication, which improved the bearing tribological performance. This study provided an experimental foundation for optimizing the surface texture of water-lubricated bearings. • A new spherical-platform texture with 9 kinds of parameter for water-lubricated bearings was manufactured and studied. • The wedge effect and the cavitation effect were promoted by the spherical-platform texture to improve the tribological performance. • The specimen with 1/2 spherical-platform texture and 1 mm upper surface diameter presented the best tribological properties. [ABSTRACT FROM AUTHOR]

The performance of diesel cylinder liner-piston ring (CLPR) friction pairs with different surface textures are very important and affect the service life, reliability, and economy of diesel engines. The aim of this study was to gain insights into interactions between thread groove surface texture (TGT) and the friction and wear behavior of a marine diesel CLPR. Four kinds of TGT with different widths, including 1, 2, 3, and 4 mm, were designed and machined on cylinder liners and then tested using a four-stroke CLPR friction and wear tester. The cylinder liner pressure, contact resistance between cylinder liner-piston ring, and worn surface morphologies of cylinder liners were obtained to examine cylinder liner performance with different width TGT. Compared with untextured cylinder liners, the experimental results showed that TGT significantly affected tribological behavior and consequently affected sealing performance of CLPR systems. Specifically, 3 mm TGT had the clearest effect on CLPR system performance, as the CLPR antifriction performance showed an average friction reduction of 30.9%, oil film lubrication performance, reflected by contact resistance, increased by 33.3%, and sealing performance improved by 14.4%. These results aided in the understanding of specific applications of surface texture on wear performance in CLPR friction pairs which could be applied in slower sliding long stroke marine engines. • Thread groove surface texture can significantly improve performance of the cylinder liner-piston ring. • The relationship of the sealing performance and tribological properties is investigate. • Experimental basis for improving performance of the cylinder liner on slower sliding long stroke marine engines is proposed. [ABSTRACT FROM AUTHOR]

The cylinder liner-piston ring (CLPR) is one of the most critical frictional pair for energy conversion in diesel engines. In this study, two forms of surface texture were respectively prepared on the liner surface by laser processing, with the modified copper nanoparticles (CNP) applied as the lubricant additives. The reciprocating tribometer and accompanying tribological testing technologies were then used to explore the synergetic effects of surface textures and additives on the tribological properties of CLPR. The results show that the composite lubrication system exhibits good friction-reduction and wear-resistance as the appropriate texture was adopted. Additionally, the synergetic effects among the storage capability of textures and the self-repairing ability of CNP additives can explain the improvement mechanism of CLPR's tribological properties. • CNP additives combined with variety forms of surface texture were used to improve tribological performance of CLPR. • The synergetic effects of suitable texture forms and CNP additives will enhance the and wear resistance of CLPR. • The storage and release mechanisms of different texture forms determine the performance of CNP additives at various loads. [ABSTRACT FROM AUTHOR]

It has great significance on the performance of cylinder liner-piston ring (CLPR) friction pairs with the different surface textures and affects the service life, reliability, and economy of diesel engines. However, most studies on the surface texture applied to CLPR have concentrated on simulated tests and computations, and the actual hot engine tests were ignored. The aim of this study was to gain insights into the interactions between different types of surface textures and the performance of diesel CLPRs under hot engine conditions. Three types of thread groove textures on cylinder liner surfaces with different widths, including 1, 2, and 3 mm, and a circular dimple texture on a piston ring with a depth of 100 μm were designed and machined, and were then tested under hot test conditions using a four-stroke diesel engine. To investigate the performance of diesel engine using different types of surface textures, the wear mass loss of the piston ring, worn surface morphologies and wear depth of the cylinder liner, exhaust gas emissions performance, and vibration performance of the diesel engine were obtained. Compared with untextured CLPRs, the experimental results indicated that appropriate surface texture (e.g., 3 mm wide grooved texture) significantly affected the comprehensive performance of the diesel engine. These findings will aid in understanding the performance impact of surface texture on diesel under hot engine conditions as well as its actual application to diesel engines. • Surface texture improved the performances of diesel CLPR under hot engine tests condition. • Wear evaluation, emissions performance, and vibration performance of diesel CLPR was studied. • Experimental basis for improving the performance of CLPR on Marine engines was proposed. [ABSTRACT FROM AUTHOR]