PSI - Issue 81

Andrii Gypka et al. / Procedia Structural Integrity 81 (2026) 478–485

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Table 1. Changes in friction and wear processes depending on sliding speed V . Sliding speed, m/s Friction and wear processes 0.2 Running-in process 1 Running-in process 2 — 3 — 4 Normal mechano-chemical process 5 — 6 Damage of tribocouple components 7 — 8 — 9 — 10 — 11 Normal thermo-chemical process 12 Destruction of the base material

As can be seen from the obtained data, throughout the entire range of sliding speed V variation under constant contact pressure P for this tribological pair, an inverse correlation is observed between the parameters I and CER R in the regimes of normal mechano-chemical and thermo-chemical friction and wear processes Gypka et al. (2024). The nominal (minimal) value of wear rate I corresponds to the maximum and stable value of CER R . In the range of normal mechano-chemical friction and wear processes (II, III), CER R reaches its maximum and stable values of 6500 – 7200 Ω, while wear rate remains minimal and stable within I=0.04 – 0.015 μm/10000 m of sliding path, and in the range of thermo-chemical processes (V), with moderate wear intensity I=0.11 μm/10000 m , CER R values lie within 820 – 850 Ω. In the regimes of running -in (I), transitional processes (IV), and bulk material destruction (VI), no clear correlation between these parameters is observed due to wide scatter in their measured values. The presence of a correlation between parameters I and CER R confirms the existence of a general tribological regularity, indicating the presence of unstable process ranges (running-in), ranges of normal mechano-chemical and thermo-chemical processes in which DSS of type I or II are formed on the friction surfaces, transitional (unstable) processes with the possibility of seizure of type I or II, and a range of bulk destruction (where I →max , CER R → 0). The existence of normal friction and wear process ranges characterized by minimal and stable values of I and maximal and stable values of CER R is determined by the structural-energy adaptability of the tribocouple materials accompanied by the formation of protective DSS of type I or type II on the friction surfaces (Fig. 6).

a

b

c

Fig. 6. Structural condition of the friction surfaces of the steel 45 specimen: a – DSS type I (Fig. 6, range II); b – DSS type II (Fig. 6, range III); c – DSS type II (Fig. 6, range V).

Elemental analysis of the DSS formed on the friction surfaces of the steel 45 specimen confirmed the existing viewpoint that DSS type I represent solid solutions of oxides in metals, whereas DSS type II correspond to chemical compounds of non stoichiometric composition. At the second stage, friction and wear processes of tribological components of diesel fuel injection equipment were investigated. The materials of the specimen and counter-specimen were steel 30Kh3MFSA, and the lubricating medium was pure diesel fuel. The experimental studies were carried out under varying contact pressure Р and a constant sliding speed (V=1.0V = 1.0V=1.0 m/s). The results of measuring the parameters μ and CER R are presented in Fig. 7.

Fig. 7. Graphs of the dependence of the friction coefficient μ and contact electrical resistance R for the steel 30Kh3MFSA – steel 30Kh3MFSA tribological pair on contact pressure P in pure diesel fuel.