Effect of modified glass fiber on tribological performance of water-lubricated bearing

Glass fiber (GF) is becoming one of the most popular reinforcement materials used in many fields. However, it still has some disadvantages such as brittleness and poor wear resistance. In order to improve its tribological property, the GF was modified and use high-density polyethylene (HDPE) as the matrix material to verify it. In this work, friction tests of HDPE samples with seven different compositions of modified GF were carried out. Different working conditions were applied to determine the tribological properties and service life as used in water-lubricated bearings. Their friction coefficient, surface morphology, wear scar, wear quality and wear mechanism were investigated. The results showed that the modified GF could significantly improve the HDPE tribological properties. Moreover, the wear mechanism of pure HDPE was mainly adhesive wear and slight fatigue wear, and the composite material was mainly abrasive wear. The 30% GF composite material had the best wear resistance, its friction coefficient was reduced by 51.56% under 0.4 MPa and 500 r/min. The findings from this experiment will provide a new method for reducing friction and wear of water-lubricated bearings.     

Improved UHMWPE through the control of sterilization dose and atmosphere

In this study, the effects of sterilization dose and atmosphere on UHMWPE wear properties and crosslinking were examined. The relationship between crosslinking and adhesive / abrasive wear mechanisms of acetabular cups was investigated.

The use of a vacuum sterilization atmosphere resulted in improvements in the wear resistance of UHMWPE for the adhesive/abrasive wear mechanisms for the doses examined in this study. The two measures of crosslinking, swelling ratio and gel fraction, values can be used to predict hip simulator wear rates over the sterilization dose range of 0 to 50 kGy for the vacuum atmosphere samples. Of the two measures, the swelling ratio is a more sensitive measure of the extent of crosslinking, particularly for highly crosslinked materials and therefore a more sensitive predictor of adhesive/abrasive wear rates.     

Grey relational analysis for optimization of wear parameters and surface roughness on nano composite coating

The higher wear resistance of Ni based nano composite coatings makes them potential replacement in protecting the substrate materials. The role of surface roughness of the coating along with wear parameters on the specific wear rate, pin temperature, and COF are addressed in the present study. The use of hard nano Al₂O₃ particles found significant role in increasing the resistance to wear for Ni matrix coatings on Al6061 material. The resistance to dislocation offered by these nano Al₂O₃ particles and smear out of debris with plastic deformation indicated abrasive and adhesive nature of wear mechanism in combination. The optimization of wear parameters are carried out by surface response method based grey relation analysis. The normal load applied onto the pin has significant influence on the specific wear rate and temperature rise in the pin. The surface roughness of the coating has also found instrumental in the higher pin temperature and friction coefficient.     

Rapid Procedure to Determine Wear Metals in Lubricating Oils and the Analysis of Variance in the Evaluation of Sample Preparation Procedures

 A new sample treatment is proposed based on a partial wet digestion in closed reactors assisted by microwaves for wear metal determinations by flame atomic absorption spectrometry (FAAS). It is rapid, precise and sensitive and allows the use of inorganic standards. Problems concerning solubility have been overcome with mixed solvents. The repeatability, stability, calibration curve and limit of detection were established. Six samples, with different degree of wear were analyzed for Fe, Cu, Pb and Cr by FAAS using the procedure proposed and other sample treatment procedures from the literature. Pb and Cr were not found in all samples. The one-way analysis of variance for Fe applied to each sample confirms the need of an acid attack and the importance of HCl for the digestion. The results obtained for Cu led us to use a two-way analysis of variance for all the samples considering the preparation procedures and the samples as variation sources. It showed no significant differences for the preparation procedures used. Therefore, treatments implying the use of acids are recommended when several wear metals are analyzed. On the other hand, the differences between the simple dilution and the procedures, implying the dissolution of metallic particles is an index to predict an imminent engine failure. Received March 1, 2001. Revision July 10, 2001.     

The Wear Resistance of Composite Materials Based on Ultra-High-Molecular-Weight Polyethylene with Fillers of Various Types

The tribological properties and wear resistance under different action of composite materials based on of ultra-high-molecular-weight polyethylene (UHMWPE) and fillers of various types such as organomodified montmorillonite (MMT), graphite nanoplates (GNP), molybdenum disulfide, and shungite prepared via polymerization in situ are studied. According to the obtained results, the introduction of these fillers to UHMWPE in the amount of 0.4–7 wt % has almost no effect on the value of the coefficient of sliding friction on steel in the mode of dry friction. Composites with GNP, MoS₂, and shungite are characterized by a significant (two- to threefold) increase in the wear resistance in the case of sliding friction on steel. The abrasive wear of composites in the case of friction on an abrasive paper is substantially affected by the type of filler, the use of MMT was the most effective for increasing the wear resistance of composites. In the case of a highspeed impact effect of water–sand suspensions all the studied composites are characterized by increased wear resistance in comparison with industrial UHMWPE at a low concentration of fillers and by an increase in the wear with the increase of the filler content.     

Effect of organomodified layered silicates on the properties and structure of polytetrafluoroethylene

The physicomechanical and triboengineering properties and the structures of polymer composite materials based on polytetrafluoroethylene and layered silicates are studied. The triboengineering characteristics are substantially improved by the introduction of a small amount of layered silicates (2–5 wt %). It is found that the introduction of organomodified layered silicates leads to a considerable reduction in the friction coefficient, by an order of magnitude, and causes an increase in wear resistance (2000-fold). With the use of X-ray structural analysis and scanning electron microscopy, it is shown that, during friction loading, filler particles are localized on the friction surface, thereby hampering wear of the material.     

Filling and wear behaviors of micro-molded parts made with nanomaterials

Microinjection molding technology and its various modifications represent established processes for micro-molded parts with high accuracy under large scale production. Recently, the use of plastic material with added reinforced fillers has become a potential alternative approach due to its high strength and the ease of batch fabrication. This paper investigates the moldability and wear properties of a polymer with added nanoceramic materials during microinjection molding. In this study, parts with micro-features were successfully manufactured using a custom-made injection machine. The results show that the polymer with added nanomaterials effectively increased the hardness achieved. In addition, a nanoceramic material, such as ZnO, improved wear resistance by 70% when nanoparticles were uniformly dispersed in the polymer and a suitable surfactant solvent was chosen. However, wear resistance decreased significantly if the nanoparticles were not processed well and a proper surfactant solvent was not chosen. The results also show that high hardness did not result in reinforced parts with high wear resistance.     

Nanowear studies in chemically heterogeneous responsive polymeric brushes by surface force microscopy

In this study, we present nanowear studies using surface force microscopy (SFM), on nanoscopic thin films of reversibly switchable binary polymer brushes [polystyrene (PS) + poly(2-vinylpyridine) (P2VP)] and respective monobrushes [polystyrene and poly(2-vinylpyridine)] synthesized via “grafting to” method. The aim was to tune the wear in nanothin polymer brush surfaces. Therefore, the effect of conformational switching of PS + P2VP brush on treatment with selective solvents for PS and P2VP chains on the wear process was investigated. Wear process on thick spin-coated films of PS and P2VP was also investigated for comparison. Nanowear experiments were performed using SFM tip by repeating scans over the surface to follow the wear process closely. The wear process on different surfaces was explained on the basis of molecular entanglement as well as adhesion and friction on the sample surface. For spin-coated PS film as well as PS and PS + P2VP brush surfaces (treated with toluene) with molecular entanglements at surface, wear mechanism involved formation of ripples. However, in case of spin-coated P2VP films as well as P2VP and PS + P2VP brush surfaces (treated with ethanol) with no molecular entanglements at surface, wear occurred via removal of polymer chains and their accumulation at the rim. For PS + P2VP surface treated with acidic water, wear mechanism was complex and inhomogeneous ripple formation was followed by formation of heaps of polymeric material in the center of scanned area. The extent of wear as measured either by root mean square roughness of the surface or spacing between the ripples, increased with the number of scans for all the surfaces. Our study shows that wear mode of polymer brush surfaces is different for different polymers and can be controlled/tuned by the use of binary polymer brushes.     

The determination of eear elements in aircraft engine oil filter debris by neutron activation analysis

The increasing trend towards the use of fine oil filtration in modern jet engines suggests that the Spectrometric Oil Analysis Program (SOAP), which routinely monitors the health of aeroengines, may no longer be effective in detecting abnormal wear trends. Since the oil filter contains a wealth of information on wear in a system, it may be necessary to perform engine health monitoring through Filter Debris Analysis (FDA). In the present study, a method was developed for the determination of 19 wear elements (Ag, Al, Au, Cd, Co, Cr, Cu, In, Fe, Mg, Mn, Mo, Ni, Sb, Sn, Ti, V, W and Zn) in aircraft engine oil filter debris samples using the analytical technique of Neutron Activation Analysis (NAA). Results obtained by NAA for the analysis of two types of filter debris samples compared well with results obtained previously for similar samples and it appears that FDA should be very useful for following wear trends.     

稀土变质热锻模具铸钢高温磨损性能的研究

研究了稀土（RE）变质热锻模具铸钢的高温磨损性能，并与热锻模具钢H13钢和3Cr2W8V钢进行对比，探讨了稀土元素的作用和热锻模具铸钢的高温磨损机理。结果表明：随着RE加入量的增加，热锻模具铸钢的磨损率先减后增，RE加入量在质量分数为0．05％时热锻模具铸钢具有最佳的高温磨损性能。RE变质热锻模其铸钢的高温耐磨性明最高于H13钢和3Cr2W8V钢。高温磨损机理为氧化磨损和氧化物的疲劳剥落，磨屑为块状的Fe2O3和Fe3O4。     

硫酸钙晶须改性双马来酰亚胺树脂摩擦磨损性能的研究

研究了载荷、偶联剂及硫酸钙晶须用量对双马来酰亚胺树脂摩擦磨损性能的影响及材料的磨损机制.结果表明,当摩擦载荷较大时,树脂基体在摩擦过程中出现明显的塑性变形和裂纹,而经过硫酸钙晶须改性的复合材料体系则塑性变形和裂纹情况得到明显的改善,并且磨损量显著降低.载荷从200 N增大到300 N后,树脂基体的磨损机制从粘着磨损过渡为严重的疲劳磨损,添加晶须体系仍以粘着磨损为主.晶须添加量较小时,复合材料的磨损机理主要为粘着磨损,晶须添加量较高时,磨粒磨损占主导地位.     

C60-丙烯酸月桂酯共聚物的合成及其摩擦学行为

合成了一种新颖的油溶性C60-丙烯酸月桂酯共聚物,采用四球摩擦磨损试验机、扫描电子电镜研究了其作为液体石蜡润滑添加剂的摩擦学特性,结果表明,C60-丙烯酸月桂酯共聚物可提高石蜡基础液的抗磨性能,改善微观磨损状态.     

Nanosized Additives to Lubricating Materials

The review deals with the synthesis and use of nanosized additives in friction and wear processes. Various types of nanosized additives are considered, and their performance as friction modifiers is demonstrated. The influence exerted on the antiwear performance of lubricating materials by the size and concentration of the introduced particles differing in the chemical nature is considered. Methods for preparing nanosized additives and stabilizing them in lubricating materials are described.     

Surface potential and resistance measurements for detecting wear of chemically-bonded and unbonded molecularly-thick perfluoropolyether lubricant films using atomic force microscopy

The wear of perfluoropolyether (PFPE) lubricants applied on Si(100) and an Au film on Si(100) substrate at ultralow loads was investigated by using atomic force microscopy (AFM)-based surface potential and resistance measurements. Surface potential data is used in detecting lubricant removal and the initiation of wear on the silicon substrate. The surface potential change is attributed to the change in the work function of the silicon after wear, and electrostatic charge build-up of debris in the lubricant. It was found that coatings that are partially bonded, i.e., containing a mobile lubricant fraction, were better able to protect the silicon substrate from wear compared to the fully bonded coating. This enhanced protection is attributed to a lubricant replenishment mechanism. However, an untreated lubricant coating exhibited considerable wear as it contains a smaller amount of lubricant bonded to the substrate relative to the partially bonded and fully bonded coatings. A sample subjected to shear is shown to have improved wear resistance, and this enhancement is attributed to chain reorientation and alignment of the lubricant molecules. The detection of wear of PFPE lubricants on Au by an AFM-based resistance measurement method is demonstrated for the first time. This technique provides complementary information to surface potential data in detecting substrate exposure after wear and is a promising method for studying the wear of conducting films.     

Macro- to nanoscale wear prevention via molecular adsorption

As the size of mechanical systems shrinks from macro- to nanoscales, surface phenomena such as adhesion, friction, and wear become increasingly significant. This paper demonstrates the use of alcohol adsorption as a means of continuously replenishing the lubricating layer on the working device surfaces and elucidates the tribochemical reaction products formed in the sliding contact region. Friction and wear of native silicon oxide were studied over a wide range of length scales from macro- to nanoscales using a ball-on-flat tribometer (millimeter scale), sidewall microelectromechanical system (MEMS) tribometer (micrometer scale), and atomic force microscopy (nanometer scale). In all cases, the alcohol vapor adsorption successfully lubricated and prevented wear. Imaging time-of-flight secondary ion mass spectrometry analysis of the sliding contact region revealed that high molecular weight oligomeric species were formed via tribochemical reactions of the adsorbed linear alcohol molecules. These tribochemical products seemed to enhance the lubrication and wear prevention. In the case of sidewall MEMS tests, the lifetime of the MEMS device was radically increased via vapor-phase lubrication with alcohol.     

AAS法测定航空润滑油中磨损金属含量

本文采用酸溶解处理样品，经乙酸丁酯－导丁醇溶剂稀释后，火焰原子吸收法，直接测定了航空润滑油中铜，镁，铝等１０种磨损金属的含量。     

钛酸钾晶须填充环氧树脂复合材料的摩擦磨损特性

以提高环氧树脂的摩擦磨损性能为目的,研究了钛酸钾晶须(PTW)填充环氧树脂复合材料的滑动干摩擦磨损特性,着重探讨PTW含量、摩擦条件等对复合材料摩擦性能的影响.通过对复合材料磨损表面的形貌分析以及复合材料表面硬度的测定,探讨了复合材料的磨损机理.结果表明:PTW能明显提高环氧树脂耐磨性并降低其摩擦系数,w(PTW)=0.08的环氧树脂复合材料的耐磨性比纯环氧树脂提高近10倍,摩擦系数降低35%.     

Properties of Nanotitanium for Potential Medical Applications

Summary : Two titanium-Grade2 (a course-grained in the received state and nanostructured after hydrostatic extrusion) were examined wear and corrosion tests. Passive oxide layers formed on the surface of both materials had a thickness of about 6 nm and the same chemical composition. The corrosion resistances measured in a 0.9% NaCl solution were comparable. The friction tests show that nano-grained Ti is suitable for use in the tribological par with UHMWPE.     

Enhancement of tribological performance of epoxy bulk composites and composite coatings using micro/nano fillers: a review

Epoxies in the form of bulk and coatings have been used throughout the years for a wide spectrum of applications in various industries ranging from aerospace, oil and gas, petrochemical and marine to several others. Their use in tribological applications, those involving a range of contact conditions and where the requirement is exceptionally low wear and friction coefficient, is often limited by the properties of the pristine epoxy matrix such as low load bearing capacity combined with low thermal conductivity values. These properties have been improved by the addition of nano‐fillers, and numerous studies have been carried out in this regard. This paper presents a detailed review of the works carried out in the recent years where addition of nano‐fillers to formulate epoxy‐based composites and coatings has shown a substantial improvement in wear and friction properties thereby enhancing their potential to be used in demanding tribological applications such as solid lubricant in bearings, as wear‐resistant protective coatings in rotating and stationary equipment and for applications in the construction industry such as floorings and airport runway repairs. Copyright © 2016 John Wiley & Sons, Ltd.     

Investigation of sub‐micron size cenosphere fillers and filler loading on the mechanical and tribological peculiarity of polyester composites

This paper investigates the effect of sub‐micron size cenosphere filler and filler loading on mechanical and dry sliding wear property of polyester composites. Composites are fabricated by filling with 10 and 20 wt% of 800 and 200‐nm size of cenosphere filler particles. Neat polyester composite is also prepared for comparison analysis. Dry sliding wear test is conducted for these composites over a range of sliding distance with different sliding velocities and applied loads on a pin‐on‐disc wear test machine. Taguchi methodology and analysis of variance (ANOVA) is used to analyze the friction and wear characteristics of the composites. The artificial neural network (ANN) approach is implemented to the friction and wear data for corroboration. In this work, mechanical properties of composites such as hardness, tensile strength, tensile modulus, flexural strength, and compressive strength revealed that mechanical properties and wear resistance of the composites increase with a decrease in the particle size. The measured Young's moduli are comparable to standard theoretical prediction models. The morphology of worn composite specimens has been examined by scanning electron microscopy to understand the dominant wear mechanisms. Finally, optimal factor settings are determined using a genetic algorithm (GA). Copyright © 2017 John Wiley & Sons, Ltd.