Marine antifouling behavior of the surfaces modified by dopamine and antibacterial peptide

Marine biofouling causes serious harms to surfaces of marine devices in transportation,aquaculture,and offshore construction.Traditional antifouling methods pollute the environment.A novel and green antifouling strategy was developed to prevent effectively the adhe sion of bacteria and microalgae.An antifouling surface was fabricated via coating Turgencin BMox2(TB)onto dopamine-modified 304stainless steel(304 SS).The surface physical and chemical properties before and after modification were characterized by Fourier transform infrared spectrometer(FTIR),X-ray photoelectron spectrometer(XPS),contact angle measurement(CA),3D optical profilometer,ellipsometer,and atomic force microscope(AFM).Antimicrobial peptide was coated onto the surface of 304 SS successfully,and the surface morphology and wettability of the modified sample were modified.Moreover,cytocompatibility of the peptide was evaluated by co-culture of peptide and cells,indicating promising cell biocompatibility at the modified sample surface.At last,antifouling performance and electrochemical corrosion were tested.Results show that the adhesion rates of Vibrio natriegens and Phaeodactylum tricornutum on the antifouling surface were reduced by 99.85% and 67.93%,respectively from those of untreated samples.Therefore,the modified samples retained superior corrosion resistance.The study provide a simply and green way against biofouling on ship hulls and marine equipment.

Intelligent Identification of Wear Mechanism via On-line Ferrograph Images

Condition based maintenance(CBM) issues a new challenge of real-time monitoring for machine health maintenance. Wear state monitoring becomes the bottle-neck of CBM due to the lack of on-line information acquiring means. The wear mechanism judgment with characteristic wear debris has been widely adopted in off-line wear analysis; however, on-line wear mechanism characterization remains a big problem. In this paper, the wear mechanism identification via on-line ferrograph images is studied. To obtain isolated wear debris in an on-line ferrograph image, the deposition mechanism of wear debris in on-line ferrograph sensor is studied. The study result shows wear debris chain is the main morphology due to local magnetic field around the deposited wear debris. Accordingly, an improved sampling route for on-line wear debris deposition is designed with focus on the self-adjustment deposition time. As a result, isolated wear debris can be obtained in an on-line image, which facilitates the feature extraction of characteristic wear debris. By referring to the knowledge of analytical ferrograph, four dimensionless morphological features, including equivalent dimension, length-width ratio, shape factor, and contour fractal dimension of characteristic wear debris are extracted for distinguishing four typical wear mechanisms including normal, cutting, fatigue, and severe sliding wear. Furthermore, a feed-forward neural network is adopted to construct an automatic wear mechanism identification model. By training with the samples from analytical ferrograph, the model might identify some typical characteristic wear debris in an on-line ferrograph image. This paper performs a meaningful exploratory for on-line wear mechanism analysis, and the obtained results will provide a feasible way for on-line wear state monitoring.

Experimental Study on Wear Performance and Oil Film Characteristics of Surface Textured Cylinder Liner in Marine Diesel Engine

It is of a vital importance to reduce the frictional losses in marine diesel engines. Advanced surface textures have provided an e ective solution to friction performance of rubbing pairs due to the rapid development of surface engineering techniques. However,the mechanisms through which textured patterns and texturing methods prove beneficial remains unclear. To address this issue,the tribological system of the cylinder liner?piston ring(CLPR) is investigated in this work. Two types of surface textures(Micro concave,Micro V?groove) are processed on the cylinder specimen using di erent processing methods. Comparative study on the friction coe cients,worn surface texture features and oil film characteristics are performed. The results demonstrate that the processing method of surface texture a ect the performance of the CLPR pairs under the specific testing conditions. In addition the micro V?groove processed by CNCPM is more favorable for improving the wear performances at the low load,while the micro?con?cave processed by CE is more favorable for improving the wear performances at the high load. These findings are in helping to understand the e ect of surface texture on wear performance of CLPR.

船舶动力系统中齿轮箱故障特征提取与模式识别方法研究(英文)

A marine propulsion system is a very complicated system composed of many mechanical components.As a result,the vibration signal of a gearbox in the system is strongly coupled with the vibration signatures of other components including a diesel engine and main shaft.It is therefore imperative to assess the coupling effect on diagnostic reliability in the process of gear fault diagnosis.For this reason,a fault detection and diagnosis method based on bispectrum analysis and artificial neural networks (ANNs) was proposed for the gearbox with consideration given to the impact of the other components in marine propulsion systems.To monitor the gear conditions,the bispectrum analysis was first employed to detect gear faults.The amplitude-frequency plots containing gear characteristic signals were then attained based on the bispectrum technique,which could be regarded as an index actualizing forepart gear faults diagnosis.Both the back propagation neural network (BPNN) and the radial-basis function neural network (RBFNN) were applied to identify the states of the gearbox.The numeric and experimental test results show the bispectral patterns of varying gear fault severities are different so that distinct fault features of the vibrant signal of a marine gearbox can be extracted effectively using the bispectrum,and the ANN classification method has achieved high detection accuracy.Hence,the proposed diagnostic techniques have the capability of diagnosing marine gear faults in the earlier phases,and thus have application importance.

智能水润滑轴承的设计与可行性综述

Water-lubrication bearings are critical components in ship operation.However,studies on their maintenance and failure detection are highly limited.The use of sensors to continually monitor the working operation of bearings is a potential approach to solve this problem,which is collectively called intelligent bearings.In this literature review,the recent progress of electrical resistance strain gauges,Fiber Bragg grating,triboelectric nanogenerators,piezoelectric nanogenerators,and thermoelectric sensors for in-situ monitoring is summarized.Future research and design concepts on intelligent water-lubrication bearings are also comprehensively discussed.The findings show that the accident risks,lubrication condition,and remaining life of water-lubricated bearings can be evaluated with the surface temperature,coefficient of friction,and wear volume monitoring.The research work on intelligent water-lubricated bearings is committed to promoting the development of green,electrified,and intelligent technologies for ship propulsion systems,which have important theoretical significance and application value.

Tribological Properties of DLC Film Prepared by C^+ Ion Beam-assisted Deposition (IBAD)

C^+ ion beam-assisted deposition was utilized to prepare deposit diamond-like carbon(DLC) film. With the help of a series of experiments such as Raman spectroscopy, FT-IR spectroscopy, AFM and nano-indentation, the DLC film has been recognized as hydrogenated DLC film and its tribological properties have been evaluated. The ball-on-disc testing results show that the hardness and the tribological properties of the DLC film produced by C^+ ion beam-assisted deposition are improved significantly. DLC film produced by C^+ ion beam-assisted deposition is positive to have a prosperous tribological application in the near future.

Tribological Behavior of Ni-based Self-lubricating Composites with the Addition of Ti3SiC2 and Ag2W2O7

The tribological properties of Nickel-based composites containing Ti3SiC2 and Ag2W2O7 fabricated by spark plasma sintering against Si3N4 balls were investigated using a ball-on-disk tribometer from room temperature to 600℃. The tribolayers formed on the friction surface and their effects on the tribological properties of composites at different temperatures were discussed based on the worn surface characterization. The results show that Ag2W2O7 is decomposed into metallic silver and CrWO4 during the high-temperature fabrication process. The composite with the addition of 20 wt% Ti3SiC2 and 5 wt% Ag2W2O7 exhibits a friction coefficient of 0.33-0.49 and a wear rate of 7.07x 10~5-9.89x 10~5 mm3/(Nm) over a wide temperature range from room temperature to 600℃. The excellent tribological properties at a wide temperature range are attributed to the formation of a glaze layer at low temperature and a tribooxide layer at high temperature, which can provide a low shearing strength for the synergistic effects of Ag and tribooxides.

High Purity Hydrogen Production by Metal Hydride System:A Parametric Study Based on the Lumped Parameter Model

The simulation of hydrogen purification in a mixture gas of hydrogen/carbon dioxide (H2/CO2) by metal hydride system was reported.The lumped parameter model was developed and validated.The validated model was implemented on the software Matlab/Simulink to simulate the present investigation.The simulation results demonstrate that the purification efficiency depends on the external pressure and the venting time.An increase in the external pressure and enough venting time makes it possible to effectively remove the impurities from the tank during the venting process and allows to desorb pure hydrogen.The impurities are partially removed from the tank for low external pressure and venting time during the venting process and the desorbed hydrogen is contaminated.Other parameters such as the overall heat transfer coefficient,solid material mass,supply pressure,and the ambient temperature influence the purification system in terms of the hydrogen recovery rate.An increase in the overall heat transfer coefficient,solid material mass,and supply pressure improves the hydrogen recovery rate while a decrease in the ambient temperature enhances the recovery rate.

Review of the evolution and prevention of friction,wear,and noise for water-lubricated bearings used in ships

With the development of green tribology in the shipping industry,the application of water lubrication gradually replaces oil lubrication in stern bearings and thrust bearings.In terms of large-scale and high-speed ships,water-lubricated bearings with high performance are more strictly required.However,due to the lubricating medium,water-lubricated bearings have many problems such as friction,wear,vibration,noise,etc.This review focuses on the performance of marine water-lubricated bearings and their failure prevention mechanism.Furthermore,the research of marine water-lubricated bearings is reviewed by discussing its lubrication principle,test technology,friction and wear mechanism,and friction noise generation mechanism.The performance enhancement methods have been overviewed from structure optimization and material modification.Finally,the potential problems and the perspective of water-lubricated bearings are given in detail.

Neural Networks Combined with Importance Sampling Techniques for Reliability Evaluation of Explosive Initiating Device

Concerning the issue of high-dimensions and low-failure probabilities including implicit and highly nonlinear limit state function, reliability analysis based on the directional importance sampling in combination with the radial basis function (RBF) neural network is used, and the RBF neural network based on first-order reliability method (FORM) is to approximate the unknown implicit limit state functions and calculate the most probable point (MPP) with iterative algorithm. For good efficiency, based on the ideas that directional sampling reduces dimensionality and importance sampling focuses on the domain contributing to failure probability, the joint probability density function of importance sampling is constructed, and the sampling center is moved to MPP to ensure that more random sample points draw belong to the failure domain and the simulation efficiency is improved. Then the numerical example of initiating explosive devices for rocket booster explosive bolts demonstrates the applicability, versatility and accuracy of the approach compared with other reliability simulation algorithm.

Insight into the Lubrication Performance of Biomimetic Porous Structure Material for Water-lubricated Bearings

Water-lubricated bearings have great advantages in the application of ship tail bearings due to the characteristics of green,pollution-free,and sustainable.However,the poor wettability of water-lubricated materials,as well as the low viscosity and poor load-carrying capacity of water,resulting in poor lubricating film integrity and short material service life under low-speed,heavy-load,start-stop conditions,which limits its application.To study the relationship between wettability and lubrication state and improve the lubrication performance of Si_(3)N_(4) under water lubrication conditions,the characteristic parameters that determine the hydrophilicity of Sphagnum were detected and extracted,and the bionic Si_(3)N_(4) model was established using Material Studio.Then,the molecular dynamic behavior and tribological properties of different Si_(3)N_(4) models were simulated and analyzed.Pore structure affects the spreading and storage of water on the material surface and changes the wettability of the material.Under the condition of water lubrication,better wettability and water storage promote the formation of water film,effectively improve the lubrication state of the material,and improve its bearing performance.

Stable oral lubrication enhancer obtained from thiolated polyethylene glycol and mucin

Mucins are vital components contributing to the unique lubrication properties of human whole saliva.For patients receiving medication and or treatment such as diabetes or radiotherapy,xerostomia(dry mouth)is a common with numerous and deleterious side effects.Although products exist on the market to relive the symptoms of Xerostomia there remains a drive to formulate a biocompatible lubricant that replicate the functionality offered by the natural biological environment.Herein,a combination of mucin and thiolated polyethylene glycol(PEG-SH)was proposed as a new saliva substitute.Mucin and PEG-SH molecules could form hydrated layers immediately by chemisorption.Meanwhile,the chemical interactions between mucin and PEG-SH molecules also promoted the formation of a mixed layer.All the pre-formed layers could decrease friction and had the potential to decrease wear,especially mucin and PEG-SH mixed layer when compared to mucin only solutions.Further investigations of tribological mechanism implied that the excellent lubrication performance of mixed layer with long effectiveness was contributed to the frictionreducing effect of PEG/mucin molecules and the mucoadhesive property of mucin.The study provides a guide for using mucin as a mucoadhesive agent to stable lubricative polymers with low molecular weight as novel salivary substitutes for lubrication.

Load and velocity boundaries of oil-based superlubricity using 1,3-diketone

The clarification of the critical operating conditions and the failure mechanism of superlubricity systems is of great significance for seeking appropriate applications in industry.In this work,the superlubricity region of 1,3-diketone oil EPND(1-(4-ethyl phenyl)nonane-1,3-dione)on steel surfaces was identified by performing a series of ball-on-disk rotation friction tests under various normal loads(3.5–64 N)and sliding velocities(100–600 mm/s).The result shows that beyond certain loads or velocities superlubricity failed to be reached due to the following negative effects:(1)Under low load(≤3.5 N),insufficient running-in could not ensure good asperity level conformity between the upper and lower surfaces;(2)the high load(≥64 N)produced excessive wear and big debris;(3)at low velocity(≤100 mm/s),the weak hydrodynamic effect and the generated debris deteriorated the lubrication performance;(4)at high velocity(≥500 mm/s),oil migration occurred and resulted in oil starvation.In order to expand the load and velocity boundaries of the superlubricity region,an optimized running-in method was proposed to avoid the above negative effects.By initially operating a running-in process under a suitable combination of load and velocity(e.g.16 N and 300 mm/s)and then switching to the target certain higher or lower load/velocity(e.g.100 N),the superlubricity region could break through its original boundaries.The result of this work suggests that oil-based superlubricity of 1,3-diketone is a promising solution to friction reduction under suitable operating conditions especially using a well-designed running-in strategy.

Wear monitoring method of water-lubricated polymer thrust bearing based on ultrasonic reflection coefficient amplitude spectrum

The water-lubricated thrust bearings of the marine rim-driven thruster(RDT)are usually composed of polymer composites,which are prone to serious wear under harsh working conditions.Ultrasonic is an excellent non-destructive monitoring technology,but polymer materials are characterized by viscoelasticity,heterogeneity,and large acoustic attenuation,making it challenging to extract ultrasonic echo signals.Therefore,this paper proposes a wear monitoring method based on the amplitude spectrum of the ultrasonic reflection coefficient.The effects of bearing parameters,objective function,and algorithm parameters on the identification results are simulated and analyzed.Taking the correlation coefficient and root mean square error as the matching parameters,the thickness,sound velocity,density,and attenuation factor of the bearing are inversed simultaneously by utilizing the differential evolution algorithm(DEA),and the wear measurement system is constructed.In order to verify the identification accuracy of this method,an accelerated wear test under heavy load was executed on a multi-functional vertical water lubrication test rig with poly-ether-etherketone(PEEK)fixed pad and stainless-steel thrust collar as the object.The thickness of pad was measured using the high-precision spiral micrometer and ultrasonic testing system,respectively.Ultimately,the results demonstrate that the thickness identification error of this method is approximately 1%,and in-situ monitoring ability will be realized in the future,which is of great significance to the life prediction of bearings.

Insight into tribological problems of green ship and corresponding research progresses

The so-called "green ship" is being regarded as a potential solution to the problems that the shipping industry faces, such as energy conservation and environmental protection. Some new features, such as integrated renewable energy application, biomimetic materials, and antifriction and wear resistant coating have been accepted as the typical characteristics of a green ship, but the tribology problems involved in these domains have not been precisely redefined yet. Further, the related research work is generally focused on the technology or material itself, but not on the integration of the applicable object or green ship, marine environment, and tribological systematical analysis from the viewpoint of the energy efficiency design index(EEDI) and ship energy efficiency management plan(SEEMP) improvements. Aiming at the tribology problems of the green ship, this paper reviews the research status of this issue from three specific domains, which are the tribology problems of the renewable energy system, tribological research for hull resistance reduction, and energy efficiency enhancement. Some typical tribological problems in the sail-auxiliary system are discussed, along with the solar photovoltaic system and hull drag reduction in traditional marine mechanical equipment. Correspondingly, four domains that should be further considered for the future development target of the green ship are prospected.

Numerical surface characterization of wear debris from artificial joints using atomic force microscopy

Study on surface features of wear particles generated in wear process provides an insight into the progress of material failure of artificial joints. It is very important to quantify the surface features of wear particles in three dimensions. In this study, a new approach using atomic force microscopy was proposed to carry out 3D numerical surface characterization of wear debris generated from artificial joints. Atomic force microscopy combined with image processing techniques was used to acquire appropriate 3D images of wear debris. Computerized image analysis techniques were then used to quantify surface texture features of wear debris such as surface roughness parameters and surface texture index. The method developed from the present study was found to be feasible to quantity the surface characterization of nanoand micro-sized wear debris generated from artificial joints.

Application of Bionic Tribology in Water-Lubricated Bearing:A Review

Water-lubricated bearing has become the development trend in the future because of its economy and environmental friendliness.The poor friction performance under low speed and heavy load seriously limits the popularization and application of water-lubricated bearings.Learning from nature,the phenomenon of low friction and wear in nature has aroused great interest of scientists,and a lot of research has been carried out from mechanism analysis to bionic application.In this review,our purpose is to provide guiding methods and analysis basis for the bionic design and theoretical research of anti-friction and anti-wear of water-lubricated bearings.The development of water-lubricated bearing materials are described.Some typical examples of natural friction reduction and drag reduction are introduced in detail,and several representative preparation methods are listed.Finally,the application status of bionic tribology in water-lubricated bearings is summarized,and the future development direction of water-lubricated bearings is prospected.

Tribological behavior of co-textured cylinder liner-piston ring during running-in

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.

Information Fusion of Online Oil Monitoring System Using Multiple Sensors

Machine lubrication contains abundant information on the equipment operation. Nowadays, most measuring methods are based on offline sampling or on online measuring with a single sensor. An online oil monitoring system with multiple sensors was designed. The measurement data was processed with a fuzzy intelligence system. Information from integrated sensors in an oil online monitoring system was evaluated using fuzzy logic. The analyses show that the multiple sensors evaluation results are more reliable than online monitoring systems with single sensors.

Influence Factors of Fractal Characterization of Reciprocating Sliding Wear Surfaces

The principal purpose of this paper is to investigate influence factors of fractal characterization of reciprocating sliding wear surfaces. The wear testing was completed to simulate the real running condition of the diesel engine 8NVD48A-2U. The test results of wear surface morphology dimension characterization show that wear surface profiles have statistical self-affine fractal characteristics. In general, there are no effects of the profilometer sampling spacing and sampling length and evaluation length on the fractal dimen-sions of the surfaces. However, if the evaluation length is too short, the structure function logarithm of the surface profile is scattered. The sampling length acting as a filter is an important part of the fractal dimen-sion measurement. If the sampling length is too short, the evaluation of the fractal dimension will have a larger standard deviation. The continuous wavelet transform can be used to improve surface profile dimension characterization.