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Polyurethane elastomers are widely used as functional alternative materials in water-lubricated bearing materials. In this study, three kinds of polyurethane elastomers with different soft chains were prepared to investigate the influence of soft chain materials on their tribological properties. The test results show that the specimen with soft chain polyols as propylene glycol has the best wear resistance, and the friction coefficient is only 0.09 at 0.7 MPa. Due to the excellent buried property, the wear debris can be discharged in time, so the surface of the test specimen is relatively flat, which is conducive to the formation of lubricating water film. This study provides the experimental basis for polyurethane as an alternative material for water-lubricated bearings. • Polyurethane elastomers with different soft chain were designed and prepared. • The samples of different soft chain materials were compared and analyzed. • The influence mechanism of soft chain on PU wear resistance was revealed. [ABSTRACT FROM AUTHOR]

Several soft tissues residing in the living body have excellent hydration lubrication properties and can provide effective protection during relative motion. In order to apply this advantage of soft matters in practical applications and try to avoid its disadvantage, such as swelling and weakening in water, a design strategy of a soft/hard double network (DN) hydrogel microsphere modified ultrahigh molecular weight polyethylene (UHMWPE) composite is proposed in this study. A series of microspheres of urea-formaldehyde (UF), polyacrylamide (PAAm) hydrogel, UF/PAAm double network, and their composites were prepared. The mechanical properties, swelling, wettability, friction properties, and the lubrication mechanisms of the composites were investigated. The results show that DN microspheres can have an excellent stability and provide hydration lubrication. The performance of 75 DN-1 composite was superior to others. This finding will provide a novel strategy for the development of water-lubricated materials and have wide application in engineering fields. [ABSTRACT FROM AUTHOR]

Polyetheretherketone (PEEK) is a kind of polymer with excellent mechanical properties combined with good wear resistance and has been widely used in the engineering field. In order to explore the possibility for PEEK using as a water‐lubricated bearing material, an in‐depth study on the water lubrication performance of PEEK was conducted by using a series of experiments. The water lubrication performances combined with the lubricating mechanism were evaluated both by the friction coefficient and by the wear behavior of PEEK. The results indicated that PEEK was suitable for water‐lubricated bearing productions. The water film could form effectively between the friction pairs under high sliding velocity, while the transfer film could form under low sliding velocity. Both the water film and the transfer film could improve the water lubrication performance for the friction pairs. Moreover, sliding velocities and contact pressures highly influence the water lubrication performance of PEEK. The increase in contact pressure or the decrease in sliding velocity would exacerbate the wear of material. The stick–slip phenomena also occurred on the specimens under low sliding velocity. The main purpose of this study is to provide an experimental basis for PEEK using as a water‐lubricated bearing material. [ABSTRACT FROM AUTHOR]

Purpose: Frictions in cylinder liner-piston ring often cause an inevitable loss of energy loss in the diesel engine. This study aims at evaluating the effect of depths in the cylinder liner groove texture on friction, wear and sealing performances. Design/methodology/approach: Five depths of groove texture cylinder liners (50, 100, 150, 200, 250 µm) were fabricated, and experiments were carried out using a special-purpose diesel engine tester. Comparative analyses of cylinder liner contact resistances, piston ring wear losses and surface appearances were conducted with respect to different surface textures and applied loads. Findings: Under no-load conditions, the cylinder liner with a 100 deep thread groove can significantly improve sealing and optimize its lubrication performance. On the other hand, the sealing is highly correlated with the depth of groove and the load within the cylinder liner. Under loaded conditions, the thread groove has less effect on the sealing performance. Originality/value: The findings can provide feasible basis for the tribological design and production of diesel engines. [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]

The water-lubricated bearing is one of the most important components in machine systems, and significantly affects safe operation. Poor lubrication makes it very difficult to ensure good wear resistance in water-lubricated bearings, especially at low speed or in complex load conditions. However, polyethylene wax (PEW) offers good self-lubricating performance, which may provide lubrication and the required wear resistance in water-lubricated bearing materials. In this reported study, a new water-lubricated bearing composite material comprised of polyurethane (PU) and a small amount of PEW were fabricated to improve the wear resistance of the PU-based water-lubricated bearings. The wear behavior of the PU-PEW composite material and the PU material was investigated at low speed and at different load conditions at room temperature using the CBZ-1 friction and wear tester. The wear resistance of these materials was evaluated based on the experimental results of the friction coefficient and wear morphologies. The experimental results indicated that the PEW additive was heated by the developed friction and was deposited on the surface of the composite material to form a lubricant film with good lubricity. As a result, the load bearing capacity of the lubricant film was improved, which effectively improved the lubrication conditions of the composite material, thereby improving the wear resistance and decreasing the effect of the load. These results suggest that this study may provide a novel approach for improving the wear resistance and lubrication condition of PU-based water-lubricated bearings. • The influence of polyethylene pax (PEW) used as the additive on wear resistance of polyurethane (PU) was studied. • The main wear form of PU basic was fatigue wear and abrasive wear under test conditions. The wear of the PU-PEW composite material mainly occurred in running-in stage. • The PU-based composite material with 6.8 wt% PEW presented the best wear resistance. [ABSTRACT FROM AUTHOR]

Severe abrasion wear of water-lubricated bearings usually occurs during low-speed and heavy-duty working conditions. It is vital to improve the anti-friction and tribological properties of the composites used in the water-lubricated bearings. In this reported work, polymer microcapsules were added to matrix material as compositional modifications, to improve the tribological properties of the bearing as it was worn against a cast copper bushing. These microcapsules appeared to reduce the phase splitting between the low-melting-point lubricant and the matrix. In this particular study, urea formaldehyde (UF) microcapsules loaded with two lubricants included N, N′-ethylene Bis-stearamide and Erucic Amide as core materials were synthesized by double emulsion method (w/o/w) and then blended with high-density polyethylene (HDPE) to form the composites. The tribological properties of the microcapsule-modified composites were investigated using a CBZ-1 tribometer under different running conditions. After testing, the microcapsules were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and the surface morphologies of composites were analyzed by using Scanning Electron Microscopy (SEM). The analytical results revealed that the tribological properties of the composites were improved as the quantity of microcapsules in the composite was increased. The composites containing the microcapsules produced lower sliding friction and exhibited a smoother surface morphology, which was due to the lubrication provided by the Erucic Amide in the microcapsules. As shell of microcapsules was worn away during the test, the encapsulated Erucic Amide was released into the friction pairs, which established a dense lubrication film. When the mass fraction of the Erucic Amide containing microcapsules is 10 wt%, the frictional coefficient of composites is reduced by 66.9% under low sliding velocity and middling applied load conditions. This study also provided an experimental basis for the structural design and performance enhancement of water-lubricated bearings. • The double emulsion method (w/o/w) was utilized in preparation of PU Microcapsules. • The new types of self-lubricating composites with microcapsules was developed. • The COF of composite is reduced by 66.9%, when Erucic Amide microcapsule is 10 wt%. [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]

As one important supporting component in ship propulsion systems, the water-lubricated stern tube bearing has great effects on shipping navigation safety. However, it is difficult to ensure the good lubrication for water-lubricated stern tube bearings under low speed working conditions. The lignum vitae have the significant self-lubricated performance on stern tube bearings. In this study, the present situation of the biomimetic application was introduced. The components of lignum vitae were analyzed to investigate the corresponding mechanism of self-lubricated. The biomimetic materials (0%, 0.5%, 1%, 3% guaiacum and high-density polyethylene (HDPE)) are designed and prepared based on the properties of lignum vitae. A series of experimental tests were then conducted in a specially designed tester to investigate the tribological characteristics of the biomimetic materials. The comparison analyses of the friction coefficients, wear mass losses and the worn surfaces were conducted under different concentration of biomimetic materials and running conditions. The analysis results show that there were significant differences in the tribological properties of the rubbing pairs in different concentration of guaiacum. The wear performance of the biomimetic material with 0.5% concentration of guaiacum was superior to that of other concentrations. In addition, the biomimetic material with 0.5% concentration of guaiacum was the most effective to improve the wear properties at the low sliding velocity of 0.11 m/s. It is believed that the knowledge gained in this study will provide a novel approach for wear reduction and lubrication performance improvement of water-lubricated stern tube bearing in ships. [ABSTRACT FROM AUTHOR]

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]

A marine diesel engine, where the cylinder liner-piston ring (CLPR) pair is one of the most important rubbing pairs, is the heart of a marine system. Studying the lubrication characteristics of the CLPR will provide a guide for rational design of the CLPR to reduce wear and prolong its service life. The surface texture features have a significant impact on the lubricating performance of the CLPR. In this study, the tribological system of the CLPR was investigated. Different surface textures (such as different sizes of surface concaves and grooves, etc.) were designed and produced on the cylinder liners using surface treatment. A series of experimental tests were then carried out in a specially designed diesel engine tester to investigate the tribological characteristics of the treated CLPR pairs. The comparison analyses of the worn surface texture features, element content of the lubrication oil, and abrasive particle characteristics were conducted under different wear surface texture features and cylinder liner speeds. The analysis results showed that there were significant differences in the tribological and lubrication properties of the rubbing pairs in different wear surface texture features. The wear performance of the CLPR pair with a regular concave texture was superior to that of the concave and groove, and regular groove textures. In addition, the regular concave with a depth-diameter ratio of 0.1 was the most effective surface texture to improve the lubrication and wear properties of the CLPR pairs. It is believed that the knowledge obtained in this study provides the real practical basis for tribological design and manufacturing of CLPR pair in marine diesel engines. [ABSTRACT FROM AUTHOR]

The lubricant temperature has a negative impact on the wear resistance of water-lubricated bearings. In this study, three different additive mass fractions polyurethane-polyethylene wax (PU-PEW) composite material were manufactured and tested under the high-temperature conditions compared with pure PU and THORDON. The tribological performance of different materials was then evaluated by the analysis of friction coefficient, wear mass loss and wear micrographs. The results show the PEW could perfectly improve the tribological performance of PU. The changes in average friction coefficient of PU-PEW1 (10 g PEW) is 0.015 lower than that of THORDON at condition of different lubrication temperature. The wear mass loss of PU-PEW1 was 6.33 mg lower and the worn surface has a higher flatness than that of THORDON. This reported study provided an experimental basis for water-lubricated bearing material selection under high-temperature and high-load conditions. • The novel polyurethane-polyethylene wax (PU-PEW) composite materials for water-lubricated bearing was designed. • The tribological properties of PU, THORDON and PU-PEW were investigated under the high-temperature and high-load conditions. • The PEW has positive effect on the tribological properties and PU-PEW's tribological properties is more stable than THORDON. [ABSTRACT FROM AUTHOR]

Water-lubricated bearings usually suffer severe abrasion under low-speed working conditions. Use of microencapsulated lubricants to modify the materials seems to be useful for reducing friction and wear in a bearing. In this reported study, palmityl palmitate microcapsules coated with a shell of urea-formaldehyde resin were prepared by in-situ polymerization and were then added to ultra-high molecular weight polyethylene (UHMWPE). Friction tests were performed using the microcapsule/UHMWPE composites by abrading them against tin-bronze discs under normal or heavy loads at low speeds. The experimental results showed that the addition of the microcapsules to the UHMWPE decreased its friction coefficient, reduced wear loss and optimized the wear surface morphology of the composites, consequently improving their tribological properties. • The palmityl palmitate microcapsules were synthesized by in-situ polymerization. • Composites with different concentrations of microcapsules were designed. • Series of tests were carried out to study the tribological properties of the composites. • The composite containing 15% microcapsules showed superior tribological performance. [ABSTRACT FROM AUTHOR]

The severe abrasion wear of water-lubricated stern bearings usually occurs in the low-speed, heavy-duty working conditions. Consequently, it is vitally important to improve the anti-friction and tribological properties of composite stern bearings. The compound molybdenum sulfide (MoS 2) is a priority additive for enhancing the tribological properties of composites. However, the water capillary effect in the defects in the MoS 2 crystal can easily lead to oxidation and failure of the lubrication properties of MoS 2. In order to eliminate the chemical oxidation of MoS 2 in a humid environment, MoS 2 was microcapsulated to improve the chemical stability of MoS 2 in a humid environment. In this reported work, urea formaldehyde (UF) microcapsules loaded with MoS 2 as the core material were synthesized using in-situ emulsion polymerization. The synthesized microcapsules were added to a high-density polyethylene (HDPE) matrix to prepare composites. The ZCuSn 10 Zn 2 bronze which widely utilized in as the water-lubricated bearing bushing in watercraft was chosen as counterparts material. The tribological properties of the composites modified with microcapsules were investigated using a CBZ-1 tribometer under different running conditions, and the surface morphology of the tested composites was analyzed by using a scanning electron microscope. The test results revealed that the tribological property of the composites filled with the MoS 2 -containing microcapsules was better than the composite that lacked the MoS 2 microcapsules. The composites containing the MoS 2 microcapsules exhibited lower sliding friction and a smoother surface morphology, which was the result of the protection provided by the microcapsule walls. The UF walls of microcapsules isolated the steam produced by water and fiction, which delayed the oxidation of the MoS 2 crystals. Upon fracturing of the walls of the microcapsules, the encapsulated molybdenum disulfide was released between the friction pairs, which reduced the friction coefficient and adhesion wear. This reported study also provided an experimental basis for structural design and performance enhancement of water-lubricated bearings. • The MoS 2 -comtaining microcapsule was prepared via double emulsion method (w/o/w). • The composite modified by MoS 2 microcapsule and the composite filled with MoS 2 were tested under different tested conditions. • The tribology performances of composite modified by MoS 2 microcapsule were superior to the composite filled with MoS 2. • The microcapsule shell relieves the oxidation of MoS 2 under water lubricated condition. [ABSTRACT FROM AUTHOR]

Abstract Ultra-high molecular weight polyethylene (UHMWPE) is commonly used to make water-lubricated bearing in industrial application. The Water-lubricated bearing components often experience boundary and mixed lubrication during operation, which induces the aging of UHMWPE material, affecting the mechanical and tribological properties of UHMWPE. This investigation aims to study how the wear resistance of UHMWPE is affected by aging. A CBZ-1 tribo-tester was used to conduct the sliding wear tests between UHMWPE pins and ZCuSn 10 Zn 2 discs rubbing pair under water lubrication. The comparison analyses of the shore hardness, friction coefficients, wear mass loss and worn surface morphologies were elevated. Also, the Raman spectrum, Infrared spectrum and the change of elements of aged UHMWPE samples were examined. The results showed that the accelerated aging had a significant effect on the mechanical and tribological properties of UHMWPE. Especially, compared with the original sample the average friction coefficient increases by 65.96% under 720 h, 80 °C aging condition. Moreover, accelerated aging also resulted in a fracture of molecular chains and chemical oxidation reaction of UHMWPE, the concentration of O element increased to 12.803% when the aging condition was 720 h, 80 °C, which was closely correlated with the deterioration of its wear resistance. The main wear mechanisms were fatigue wear and abrasive when the aged temperature was 40 °C, 60 °C and the aged time was 120 h, 240 h and 360 h. At the 80 °C, 480 h and 720 h aged conditions, the main wear mechanisms between rubbing pair were adhesin wear and fatigue wear. The knowledge gained herein will be useful for optimizing and designing water-lubricated material in extreme conditions to prolong the service life of water-lubricated bearings. Highlights • The accelerated aging condition had an obvious effect on the mechanical and tribological properties of UHMWPE samples. The average friction coefficient increases by 65.96% when aging time was 720 h and aging temperature was 80 ℃. • It was observed that the mechanical and tribological degradation correlated with molecular structure change of UHMWPE. Aging resulted in a fracture of molecular chains and chemical reaction of UHMWPE, which significantly damaged the properties of UHMWPE material. • With aging time and temperature increased, the wear mechanisms between rubbing pair were fatigue wear and abrasive wear, and then turned into adhesion wear and fatigue wear. [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]

In order to apply the hydration lubrication of soft material in heavy load engineering fields, a series of polyacrylamide (PAAm) hydrogel particle/high-density polyethylene (HDPE) composites were prepared. Their mechanical property, soaking surface morphology, wettability, friction property and lubrication mechanism were experimentally obtained and analyzed. The results show that PAAm hydrogel particles played an important role in the lubrication and antifriction of composites, and the friction properties of 1 wt% PAAm hydrogel particle composite were superior to others of different concentrations. The present study suggests that the composite possesses both the high mechanical properties of HDPE and the excellent hydration lubrication of PAAm hydrogel particles. This finding will provide a novel approach for improving friction properties of water-lubricated materials and are conducive to practical application in engineering fields. Image 1 • A new approach to use soft matters in engineering applications is proposed. • The composite combined hydration lubrication and high strength is prepared. • PAAm hydrogel fragments can provide the good lubricating performances. [ABSTRACT FROM AUTHOR]