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.
•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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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.
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•A new composite material composed of thermoplastic polyurethane, tetra-needle zinc oxide whisker, and molybdenum disulfide was fabricated.•Tetra-needle zinc oxide whisker reduced the ...deformation behavior of the wear surface, coefficient of friction, and fluctuation range, resulting in the reduction of frictional vibration.•Molybdenum disulfide enhanced the self-lubricating properties of thermoplastic polyurethane, and peeled off and transferred to the contact surface, resulting in low and stable coefficient of friction behaviors.•The synergistic effect of 6% tetra-needle zinc oxide whisker and 9% molybdenum disulfide possessed the best frictional vibration reduction properties.
A novel thermoplastic polyurethane (TPU) matrix composite was combined with tetra-needle zinc oxide whisker (T-ZnOw) and molybdenum disulfide (MoS2) particles. Frictional vibration experiments were conducted to study the effect of T-ZnOw and MoS2 particles on frictional vibration behaviors. The tribological properties and vibration behaviors of TPU composites were synthetically analyzed to reveal the effects of T-ZnOw and MoS2 on the friction excitation force and vibration reduction properties. The results showed that T-ZnOw enhanced anti-deformation property, and MoS2 weakened the friction excitation force in the friction process, which resulted in a lower coefficient of friction (COF) with a small amplitude, and eliminated the high-frequency vibration amplitude. In addition, the particle composition of 6% T-ZnOw and 9% MoS2 was controlled to obtain a low COF and the best vibration reduction properties. The knowledge obtained herein contributes to the understanding of the synergistic effects of T-ZnOw and MoS2 on COF and vibration reduction behaviors, and the development of a water-lubricated TPU composite stern tube bearing with low COF and good vibration reduction properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Frictional vibration and noise usually cause machining error and noise pollution. Stick–slip plays an important role in generating frictional vibration and noise. This study characterized frictional ...vibration and noise during the stick–slip of a Si
3
N
4
ceramic/metal friction by using an acoustic emission method. Experimental results showed that frictional vibration and noise mostly occurred during the slip process. The impacts of the rough peaks between metal disk and ceramic ball during sliding induced the vibration to irradiate noises. The superposition among the frictional vibrations caused the multiplication of vibrational frequency. The major vibrational frequency slowly shifted to a higher frequency as the increase in sliding speed. The vibrational accelerations and their major vibrational frequency increased with the increase in the external load. The knowledge gained herein provides a more comprehensive understanding of stick–slip friction, frictional vibration, and noise, and offers a guidance for controlling or minimizing stick–slip, frictional vibration, and noise.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Lignum vitae was widely applied in water-lubricated bearing because of its green, pollution-free, excellent mechanical, and self-lubricating properties. The slow growth cycle is difficult to meet the ...bearing's rapid development. Lignum vitae chips were used to modify thermoplastic polyurethane (TPU) to extend its good self-lubricating properties and improve tribological behaviors. The results showed that lignum vitae improve TPU's shore hardness, elastic modulus, and elongation, but at the slight cost of tensile strength and thermal stability. Besides, lignum vitae chips endowed TPU with good hydrophilicity and water absorption properties, which conduced to form effective lubricating film and reduced COF behaviors. TPU with 6% lignum vitae chips had the best COF reduction and wear resistance. But excessive lignum vitae chips weakened elastic modulus and elongation to increase COF behaviors and wear process. The outcome obtained herein would provide strong theoretical guidance for developing novel green and sustainable composites with excellent tribological properties.
•A novel green TPU matrix water-lubricated bearing was fabricated by adding lignum vitae chips.•Lignum vitae possessed many polar bonds and hydrophilic functional groups.•Lignum vitae chips endow TPU with hydrophilicity and excellent water absorption properties.•TPU with 6 wt% lignum vitae chips presented the best COF reduction and wear resistance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Water lubricated stern bearings (WLSBs) are the critical component of ship propulsion system and have important effect on navigation safety. Operating temperature plays a main role on the performance ...of WLSBs. This paper aims to investigate the effect of operating conditions on bearing temperature characteristics under hydrodynamic lubrication. A novel CFD simulation method developed to improve calculation accuracy. Finite difference method was used to decrease the error of geometric modeling while the experiment and experimental correction formula were exploited to obtain improved boundary conditions. Based on the new method, the effects of operating conditions on temperature characteristics for two typical WLSBs were studied, and mechanisms of bearing temperature field evolution were discussed. Results show that the max friction coefficient appears when bearings are in low velocity and low load condition. Total heat flux density is a function of linear velocity, pressure and friction coefficient. Max temperature of bearing at 0.4 MPa decrease along with increased velocity, while decrease first and then increase at 0.2 MPa. Moreover, peak temperature appears at eccentric side and beyond minimum water film thickness position about 4–40°. High temperature area mainly located at the position of 80–140° in circumferential direction and 0.2–0.13 m in axial direction. With the increase of inlet water velocity, the max temperature of bearing changes slightly. It is appropriate to set the inlet velocity at 2 m/s to obtain better cooling performance. This work can provide theoretical basis for the operation monitoring of WLSBs and the development of new materials.
The
Editorial Office retracts the article "The Effect of Intrinsic Mechanical Properties on Reducing the Friction-Induced Ripples of Hard-Filler-Modified HDPE" ....
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Ripple deformations induced by friction on polymeric materials have negative effects on the entire stability of operating machineries. These deformations are formed as a response to contacting ...mechanics, caused by the intrinsic mechanical properties. High-density polyethylene (HDPE) with varying silicon nitride (Si
N
) contents is used to investigate different ripple deformation responses by conducting single-asperity scratch tests. The relationship between the intrinsic mechanical properties and the ripple deformations caused by filler modifications is analyzed in this paper. The results show the coupling of the inherent mechanical properties, and the stick-slip motion of HDPE creates ripple deformations during scratching. The addition of the Si
N
filler changes the frictional response; the filler weakens the ripples and almost smoothens the scratch, particularly at 4 wt.%, but the continued increase in the Si
N
content produces noticeable ripples and fluctuations. These notable differences can be attributed to the yield and post-yield responses; the high yield stress and strain-hardening at 4 wt.% provide good friction resistance and stress distribution, thus a smooth scratch is observed. In contrast, increasing the filler content weakens both the yield and post-yield responses, leading to deformation. The results herein reveal the mechanism behind the initial ripple deformation, thus providing fundamental insights into universally derived friction-induced ripples.
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Gear systems are an essential element widely used in a variety of industrial applications. Since approximately 80% of the breakdowns in transmission machinery are caused by gear failure, the ...efficiency of early fault detection and accurate fault diagnosis are therefore critical to normal machinery operations. Reviewed literature indicates that only limited research has considered the gear multi-fault diagnosis, especially for single, coupled distributed and localized faults. Through virtual prototype simulation analysis and experimental study, a novel method for gear multi-fault diagnosis has been presented in this paper. This new method was developed based on the integration of Wavelet transform (WT) technique, Autoregressive (AR) model and Principal Component Analysis (PCA) for fault detection. The WT method was used in the study as the de-noising technique for processing raw vibration signals. Compared with the noise removing method based on the time synchronous average (TSA), the WT technique can be performed directly on the raw vibration signals without the need to calculate any ensemble average of the tested gear vibration signals. More importantly, the WT can deal with coupled faults of a gear pair in one operation while the TSA must be carried out several times for multiple fault detection. The analysis results of the virtual prototype simulation prove that the proposed method is a more time efficient and effective way to detect coupled fault than TSA, and the fault classification rate is superior to the TSA based approaches. In the experimental tests, the proposed method was compared with the Mahalanobis distance approach. However, the latter turns out to be inefficient for the gear multi-fault diagnosis. Its defect detection rate is below 60%, which is much less than that of the proposed method. Furthermore, the ability of the AR model to cope with localized as well as distributed gear faults is verified by both the virtual prototype simulation and experimental studies.
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