摘要:

AbstractThe applicability of the field desorption mass spectrometry (FD‐MS) technique to the determination of the molecular weight distribution parameters of various commercially available petroleum sulphonates is demonstrated. The technique has been substantiated using standards such as polyethylene glycols, polystyrenes, and sodium petroleum sulphonates. This study of molecular weight averages compares the results from gel permeation chromatography and FD

ISSN:1354-4063    

DOI:10.1002/tt.3020090202

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractIn the present work, several molecular dynamics simulations have been performed to clarify dynamically the contact mechanism between the specimen surface and probe tip in surface observations by an atomic force microscope (SFM) or friction force microscope (FFM). In the simulation, a three‐dimensional model is proposed where the specimen and the probe are assumed to consist of monocrystalline copper and rigid diamond or a carbon atom, respectively. The effect of the cantilever stiffness of the AFM/FFM is also taken into consideration. The surface observation process is simulated on a well‐defined Cu{100} surface. From the simulation results it has been verified that the surface images and the two‐dimensional atomic‐scale stick‐slip phenomenon, just as is the case for real AFM/FFM surface observations, can be detected from the spring force acting on the cantilever. From the evaluation of the behaviour of specimen surface atoms, the importance of the specimen stiffness in deciding the cantilever properties can also be understood. The influence of the probe tip shape on the force images is also evaluated. From the results it can be verified that the behaviour of the specimen surface atoms as well as the solid surface images in AFM/FFM surface observations can be understood using the molecular dynamics simulation of the model

ISSN:1354-4063    

DOI:10.1002/tt.3020090203

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractA new method has been developed for tribological testing of thin, hard antiwear coatings, using a ball‐on‐disc tribosystem, under conditions of dry sliding. In this, an Al2O3ball is pressed against a coated steel disc. Wear debris is removed from the contact zone by a stream of dry argon in this novel method. This improves the stability of the tribological properties and the repeatability of the test results. All test conditions are precisely defined, in particular: the type of motion, air relative humidity, ambient temperature, sliding speed, load, tribosystem spatial configuration, substrate material, substrate hardness and roughness, and coating thickness. The method developed has been used to test various physical vapour deposition coatings (deposited by the vacuum arc method), i. e., single‐layer TiN, Ti(C,N), CrN, and Cr(C,N), and multilayer Cr(C,N)/CrN/Cr and Cr(C,N)/(CrN+Cr2N)/CrN/Cr. It is shown that CrN coatings exhibit the best antiwear properties, and Ti(C,N) the worst. Friction coefficients for CrN and Cr(C,N) coatings are much lower than for the more commonly used TiN. Multilayer coatings have better antiwear properties than single‐lay

ISSN:1354-4063    

DOI:10.1002/tt.3020090204

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThermo‐oxidation of base oils is the primary cause of lubricant degradation and engine failure during use. Degradation is mainly due to high‐temperature oxidation and thermal decomposition near the piston ring zone, forming oxygenated compounds that polymerise to form high‐molecular‐weight insoluble deposits. New‐generation base oils are found to be more stable towards oxidation and deposit formation due to the absence of aromatics and polynaphthenes. However, compatibility with antioxidants and other additives is now of greater concern because of the poor solvency of these oils. With the increase in the purity of the oil, sometimes the oxidation performance is poor in comparison to group I oils, mainly due to the removal of sulphur compounds, which act as natural antioxidants.Thermal techniques, such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), are emerging as fast and accurate methods for determining the thermo‐oxidative stability of base oils and their additive blends, making it possible to measure the oxidation induction time, incipient oxidation temperature, and deposit‐forming tendency. The objective of this work is to evaluate the thermo‐oxidative stability of new‐generation group II/III base oils without antioxidant additives, using DSC and TGA. The kinetics of base oil oxidative degradation are studied using different heating rates. The data obtained from thermal techniques are correlated with the micro‐oxidation data obtained from the Penn State Micro‐Oxidation (PSMO) test. The response of a typical antioxidant additive, zinc dialkyldithiophosphate, towards oxidative degradation of base oils

ISSN:1354-4063    

DOI:10.1002/tt.3020090205

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThis paper describes the results of accelerated and operational life tests on bearings for the Moderate Resolution Imaging Spectroradiometer (MODIS). It also describes the post‐test analysis of the disassembled bearings. Analysis was performed using micro‐Raman, micro‐FTIR, X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and size exclusion chromatography (SEC). In general, the three sets of bearings in each of three test stations were in very good condition after accumulating 68, 144, and 209 million cycles, respectively. Some of the bearings exhibited lubricant degradation, indicated by viscous lubricant deposits on the cage and r

ISSN:1354-4063    

DOI:10.1002/tt.3020090206

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThis paper presents a new method and criterion for predicting the occurrence of the interruption of a kinematic joint contact in a multi‐bar mechanism. The method is based on the elastic interactions in the tribosystems of the joints with imposed clearances. The method was used in a four‐bar mechanism with clearance in the joint formed from the coupler and the rocker. The analytical results were experimentally confirmed by measurement of the acceleration of the roc

ISSN:1354-4063    

DOI:10.1002/tt.3020090207

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

ISSN:1354-4063    

DOI:10.1002/tt.3020090208

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

ISSN:1354-4063    

DOI:10.1002/tt.3020090209

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

ISSN:1354-4063    

DOI:10.1002/tt.3020090201

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY