Tribology information

After these initial and promising lateral-force results, the friction force microscopy (FFM) was introduced. The FFM is a modified SFM with a four-quadrant photodiode, based on the laser beam deflection technique (Meyer Amer 1988) (Fig. 2.17). The beam is emitted by a low-voltage laser diode and reflected from the rear side of the cantilever to the four-quadrant photodiode. With this detection scheme, normal and torsional forces can be measured simultaneously. The torsional forces correspond to the lateral forces measured with the instrument of Mate et al. (1987). In 1993, Ovemey introduced the threefold measurement of topography, friction and elasticity on a polymer sample using an ITM. With this latest achievement, a wide spectram of tribological information was opened up, limited only by the lattice parameters of the sample. 

VNY HIGH STRENGTH POLYMERS have been developed in recent years. The dreams of all-composite airplanes as well as artificial hearts have become realities. Thus, it is almost a necessity for chemists to acquire tribological information about these new polymers or composites and, vice versa, for tribologists to seek chemical knowledge about these materials. 

Figure 1. General principle of the combinatorial approach a parameter library is produced by varying the tribological stress on a single sample depending on the lateral e.g. radial (R) and angular (> position on the disk. The tribological information acquired during or after the test (coef dent of friction, wear) and the spectroscopic information (chemistry of surface Im) from surface-analytical examination of the sample can...

This section contains fatigue and tribology information for several high-temperature, high-performance plastics. They might be classified or be appropriate to include in another chapter, but they are grouped in this chapter because of their performance levels. 

No general conclusions on the relations among these parameters can be drawn for the scarcity of better information. Experiments should be designed to measure the tribological properties of TFL for engineering applications. 

Somorjai, G. A., Introduction to Surf ace Chemistry and Catalysis, Wiley, New York, 1994. (Undergraduate level. This in-depth treatment of surface chemistry and catalysis brings the experience and perspectives of a pioneer in the field to the general audience. The book is meant to be an introductory-level description of modern developments in the area for students at the junior level. However, it is also an excellent source of the current literature and contains numerous, extensive tables of data on kinetic parameters, surface structure of catalysts, and so on. Chapter 3, Thermodynamics of Surfaces, and Chapter 7, Catalysis by Surfaces, cover information relevant to the present chapter. Chapter 8 discusses applications in tribology and lubrication (not discussed in this chapter).)... 

In spite of the strong economic importance of friction and wear and the resulting scientific effort, our understanding of the fundamental processes is still rudimentary. This results from the complexity of these topics. In addition, this complexity demands a multi-disciplinary approach to tribology. In recent years the development of new experimental methods such as the surface forces apparatus, the atomic force microscope, and the quartz microbalance made it possible to study friction and lubrication at the molecular scale. However, this new wealth of information does not alter the fact, that there are no fundamental equations to describe wear or calculate friction coefficients. Engineers still have to rely largely on their empirical knowledge and their extensive experience. 

Due to the continuous input of thermal energy necessary to maintain mechanical work, tribological systems are in progressive equilibrium. In the tribosystem, the flow of energy is accompanied by an increase in entropy of the total system and is reflected by the tribochemical reactions and deterioration of lubricant quality. Our understanding of tribosystems has been seriously limited by a lack of kinetic information on critical reactions in hydrocarbon formulation and critical reactions at interfaces. 

Oil formulation (a) By using specific examples, what is meant by the tribological system in progressive equilibrium , (b) What information about the molecular structure of additives is indicated by the oil formulation requirements ... 

Scanning Probe microscopy techniques are extremely useful for analysing surfaces, but cannot lead to bulk information. They will be used each time surface properties are important, i.e. when surfaces are used for themselves (tribological applications, adhesion, etc.). However, in some cases, the study of transport phenomena (such as thermal or electrical conductivity) by modified AFM may lead to bulk characterisation such as the formation of a percolating nanotube network for instance. 

The three major new atomic-scale experimental methods developed in the last decade are the quartz crystal microbalance (QCM) [2 4], atomic and friction force microscopes (AFM/FFM) [5,6], and the surface force apparatus (SEA) [7,7a,8]. These new tools reveal complementary information about tribology at the nanometer scale. The QCM measures dissipation as an adsorbed him of submonolayer to several monolayer thickness slides over a substrate. AFM and FFM explore the interactions between a surface and a tip whose radius of curvature is 10 100 nm [9]. The number of atoms in the contact ranges from a few to a few thousand. Larger radii of curvature and contacts have been examined by gluing spheres to an AFM cantilever [10,11]. SEA experiments measure shear forces in even larger-diameter ( 10 pm) contacts, but with angstrom-scale control of the thickness of lubricating hlms. 

Acronym Name Probe Detection Signal Information Space Resolution Tribology... 

Molecular dynamics (MD) methods can be used to simulate tribological phenomena at a molecular level. These have been used primarily to simulate behaviour observed in AFM and SFA measurements. Such simulations are limited to short-timescale events, but provide a wealth of information and insight into tribological phenomena at a level of detail that cannot be realized by any experimental method. One of the most interesting contributions of molecular dynamics... 

Studies with a pin-on-disk apparatus have been performed to elucidate the tribological behavior of aramid containing pol5mier composites. These studies include theoretical considerations and can serve as a diree-tive on how to get information about tribologieal and wear properties in other related systems. ... 

For description of the tribotechnically used machine-elements and more information about tribology, the book Tribology Handbuch - Reibung und VerschleiP [233] is recommended to the reader. 

The results obtained by the EQCM contain information relevant to the understanding of phenomena in the area of nano-tribology, where techniques such as surface force apparatus and atomic force microscopy are used. In both cases the results carry information regarding the properties of a nano-scale layer of liquid at the interface. 

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