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The first chapter is dedicated to analysis of the previous works related on a study

of vibrations excited by friction is carried out. It is emphasized that in the literature

two main mechanisms for generating vibration signals, which depend on the contact

conditions are distinguished namely a low level of adhesive interaction (normal

friction) and a high level with elements of local adhesion between surfaces (intense

destruction of surfaces). If the interaction between the surfaces takes place under

normal friction, then the acoustic waves are exciting by the collision of rigid

irregularities and propagate in each of contacting surfaces, generating their own

oscillations that are practically independent of each other. In the case of a high level

of adhesive interaction, frictional forces can change the dynamics of the entire

system, and then the system's response becomes nonlinear. Frictional interaction

finally depends on the specifics of the mechanical system, boundary conditions, and

properties of contact surfaces, normal contact load, environment and a number of

other factors. Each of them, in addition to changing the tribological characteristics

(friction coefficient, wear, temperature), affect the systemʼs response, changing the

overall power and spectral composition of vibration signals. Many researchers chose

a simple friction system with one degree of freedom for the analytical and numerical

analysis of vibrations, excited by friction. The friction force in this case is a non-

linear function of the sliding velocity, represented by a power series. Then nonlinear

terms and the damping component can be combined together and the friction-velocity

characteristics can be considered together as the some form of damping. Due to the

nonlinearity of the friction-velocity characteristic and the influence of external

disturbance, stable solutions of the second-order nonlinear differential equation must

be found in different modes of friction. Procedures for obtaining solutions even in the

first approximation are quite cumbersome.

Basing on the results presented in the literature, it can be concluded that a

number of regularities related to the frictional excitation of vibrations were

established and verified experimentally on the basis of this simplest model of the

friction system. However, because of the multi factorial influence on this

phenomenon, many problems remained outside the attention of researchers. One of
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