Breviary Technical Ceramics



 Tribological systems

Generally speaking, friction and wear are thought of as reflecting the losses in tribological systems. They depend not only on the properties of the individual materials, but also on interactions that occur and on the magnitudes of all the stresses operating in the system. Under some circumstances, even small changes in the system can have significant effects on the coefficient of friction and on the degree of wear.

Friction and wear are therefore properties of a system, not simply characteristics of individual materials!

A tribological system consists of these four elements: the main body, the opposing body, the intermediate material and the surrounding medium. These, together with the total of all the stresses involved, which we may call the stress system, determine the coefficient of friction, the type of wear and the level of wear that occurs.

Figure 94:
Representation of a tribological system

The stress system is composed of the technical and physical parameters of the normal force, FN, the velocity, v, the temperature, T, the duration of the stress ts, the types of movement and the changes of these factors over time.
In practice, tribological systems are divided into

  • closed tribological systems such as bearings and seals, corresponding to Figure 94 and
  • open tribological systems such as chutes, channels and pipe systems. In these cases, the function of the opposing body, which is not present, is performed by the intermediate material.

Systematic analysis of a tribological reaction is treated in DIN 50 320.

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