Methodological Approach in the Simulation of the Robustness Boundaries of Tribosystems under the Conditions of Boundary Lubrication

Abstract

In the presented work, a methodical approach was developed for determining rational operation modes of tribosystems, taking into account their design. This approach makes it possible in the designing stage, according to the predicted operating modes, to calculate the limits and margins of stable work in operation. The definition of the robustness of the tribosystem and the criteria for assessing the robustness are formulated based on the theory of stability of technical systems. It is shown that such a methodical approach allows for determining the modes of the rational operation of the designed structures without damaging the friction surfaces. Experimental studies have proven that not all designs of tribosystems lose stability due to the appearance of friction surface burrs. There are designs where the loss of stability occurs upon the appearance of accelerated wear. The developed criteria take into account two options for the loss of stability. An experimental verification of the modes of loss of stability of tribosystems was performed by the appearance of a burr or the beginning of accelerated wear with the calculated values of the robustness criteria. The obtained results allow us to conclude that the modeling error is within 8.3–18.7%, which is a satisfactory result in the study of friction and wear processes. Robustness criteria is based on the coefficient of friction RRf and wear rate RRI, and must be used when designing new constructions of tribosystems. Theoretical calculations of such criteria and the dependence of their change on changing the predicted operating modes will allow for justifying rational operating modes within their stability.

Substantiation of a rational program for the running-in of tribosystems

“…From the review of the works given in the review of literary sources, it can be concluded that the most promising program or mode of running-in of tribosystems is running-in "on the edge of burr", in our case "on the edge of loss of stability of the tribosystem". From the conclusions of the work [19] it follows that the loss of stability of the tribosystem, depending on the magnitude of the load and speed of sliding and the speed of external influence, may occur in the form of the appearance of accelerated wear or burr. Therefore, the term "on the verge of loss of stability of the tribosystem" is more correct.…”

“…The purpose of running-in modes is determined by the limit of loss of stability of the tribosystem, the method of determining which is given in [19]. During running-in, the process of converting the mechanical energy of friction into internal energy, primarily thermal energy, which is dissipated into the environment due to thermal conductivity, as well as the energy of structural changes in the surface layers of triboelement materials, takes place.…”

“…If the amount of mechanical energy (power -W) will exceed the permissible limit, RR = 1, the formula for calculation is given in [19], loss of stability of the tribosystem may occur, i.e. burr or accelerated wear of the triboelements of the tribosystem occurs.…”

“…where Nload on the tribosystem, dimensions N; Nmaxmaximum load on the tribosystem, on the verge of loss of stability, dimension N; vslsliding speed, dimension m/s; vsl(min)minimum sliding speed, dimension m/s; Wthe power supplied to the tribosystem, dimension W; Wbthe power supplied to the tribosystem on the verge of loss of stability, dimension W; RRthe value of the range of robustness of the tribosystem, a dimensionless value, is calculated according to the formula given in the work [19];…”

“…The proposed program differs from the known ones in that it takes into account the load speed of the tribosystem, which is presented in the paper [19] in the form of load dynamic coefficient kd. This requirement is justified by the right-hand side of the differential equation [19] and represented by the parameter tlload time, s.…”