*1.1.1. Authors' own methodology (MB –1)*

In this section the following test parameters were assumed: constant normal pressure N = 350 [kG] ≈ 3433 [N], changeable rotational speed of the bearing : n1= 300 [rpm], n2= 600 [rpm], n3= 1200 [rpm]. Because of changeable rotational speed it was assumed that the number of bearing's cycles will serve as the unit of its operation. Since the tests were treated as pilot ones, at this stage tests were conducted at 20,000 cycles of bearing's operation. It should be noted that before each measurement the bearing was cooled in a stream of air for 4 hours in normal conditions. All the measurements were recorded using a computer system.

**Figure 1.** SMT-1 friction tester a) general view, b) friction node
