|
|
|
|
the Methodology of Tribo-Fatigue
Interactions between scientific disciplines It has already been discussed and shown in Fig. 5 that tribology, the mechanics of fatigue fracture and the theory of reliability of mechanical systems are the foundation of tribo-fatigue. Another aspect of the problem (Fig. 14) is that the results yielded by tribo-fatigue, on their hand, strongly contribute to tribology, the mechanics of fatigue fracture and the theory of reliability of mechanical systems. Tribology (T) due to tribo-fatigue (TF) formulates a new class of essential problems, such as studies of external (in relation to contact) loading and its effect upon the characteristics of friction and wear of units [29–34 and others]. Tribo-fatigue briefly determines this class of problems as the back effect (BE in Fig. 14, for example, see formulas (3), (5), (10)). Then, it is easy to see that, thanks to tribo-fatigue (TF) again, the mechanics of fatigue fracture (F) deals with a new class of essential problems, investigation of friction and wear processes and their effect upon the characteristics of fatigue resistance of materials and structural elements [35–39 and others]. Tribo-fatigue determines this class of problems as the direct effect (DE in Fig. 14, for examples see formulas (2), (4), (9)). Finally, when the theory of reliability (R) is concerned, again due to tribo-fatigue (TF), an individual class of practically essential problems is elaborated: studies of failures of active systems using complex criteria of wear-fatigue damage and fracture [40–42 and others] (see function (8) for example). It is a new S-function (8) of two-dimensional distribution of random values x and y:
Figure 14 – Relationships and interactions between scientific disciplines
where хmin, ymax, a, b, mx, my, x*, y* are the parameters of distribution. An essential feature of the function is that one of the random values has the lowermost limit (х > хmin) and the other has the uppermost limit (у < ymax). Function (11) can be apparently useful in the theory of reliability and in mathematical statistics to analyze a variety of random events. Nevertheless, once again it should be explicitly emphasized that tribo-fatigue not only has yielded new results useful “for tribology”, “for the mechanics of fatigue fracture”, “for the theory of reliability of mechanical systems”, but the most essential is that tribo-fatigue has yielded fundamentally new scientific concepts useful to formulate and successfully solve the problems of great practical significance. For example, the problem of dynamic (optimal) control (U) of the process of WFD of active systems has been formulated. It implies that the time has come to proceed from traditional calculations and designing of basic (individual) parts of machines based on their strength and wear resistance to calculations and designing of mechanical systems, i.e. the same parts, yet with the account of actual interactions between them. The new principle of designing the most essential active systems of a machine based on tribo-fatigue criteria requires to assess precisely and to achieve specified reliable performance with the least cost. Still it should be admitted that there is some cognitive and psychological barrier some specialists confront and have known difficulties to overcome when digesting new ideas of tribo-fatigue. In particular it is due to the fact that the theory of fatigue wear of friction surface has been longly and fruitfully developed in tribology. Following this deep-rooted tradition some tribologists treat tribo-fatigue as fatigue in the process of friction. The II International Symposium on Tribo-Fatigue (Moscow, 1996) much contributed to overcoming this erroneous approach. It can be presumed that the III International Symposium on Tribo-Fatigue to be held in October, 2000, in Beijing [8] will further integrate various scientific schools and stimulate mutual understanding for the purpose of successful solution of theoretical and practical problems of promoting reliability of modern technology using the complex criteria of performance. Hence, it seems natural that some engineering universities, like the Gomel State University named after P. O. Sukhoy, the Belarusian State University of Transport have included the fundamentals of tribo-fatigue as a university discipline into their curricula for mechanical engineers. Experience shows that universities are fast to respond to practical demands for training engineers as soon as new trends emerge in science and technology.
|
,