OXIDE NANOMETRIC PELLICLES FORMATION BY APPLYING ELECTRICAL DICHARGES IN INPULSE

The paper presents the results of theoretical and experimental investigations of phenomena that accompany the formation of nanometer oxide and hydroxide pellicles by applying electrical discharges in impulse (EDI). The chemical content of processed surface analysis (EDX – Energy Dispersive X-ray analysis) attests the presence of oxygen that reaches up to 60% at. for steel surfaces, 30-35% at. for those made of titanium alloys, up to 20% at. for those made of aluminum alloys, and up to 50% at. for those made of copper alloys. The presence of considerable amounts of nitrogen is found only in titanium and iron alloys (and constitutes about 15% at), while in aluminum and copper alloys its presence is not significant. The superficial phase analysis (XPS - X-ray Photoelectron Spectroscopy) of the oxygen allowed us to state that the oxygen in pellicle forms three base structures: -O-2 (oxide), - OH- (hydroxide), and structures of the type О-С and О-С=О. The chemical analysis showed that the concentration of each of the three components is 0.89:1.00:0.50

THEORETICAL CONTRIBUTIONS ON THE SELECTION OF POSSIBLE TRIBOLOGICAL COUPLES OF MATERIALS FOR THE MANUFACTURE OF PRECESSIONAL TRANSMISSIONS

Selecting gear materials is a great challenge for engineers. Gear teeth are subject to difficult and severe loading conditions. Simultaneous action of alternating normal and tangential dynamic stresses occurs, contact deformations accompanied by sliding friction. Gears are subject to increased requirements in terms of strength, geometric accuracy, dimensional stability, and durability. For the manufacture of gears, especially from thermoplastic materials, a theoretical argumentation of the materials is needed. An extensive study of thermoplastic materials, around the world needs to be done and the most efficient tribological couples to be chosen in terms of heat transfer from the gear zone, operation with or without lubrication, and gear life. In this paper, a theoretical synthesis of the Steel / Plastic, Plastic / Plastic, Plastic/Steel tribological couples is made, which were used in conformist and non-conformist experiments. Therefore, selected tribological couples are supposed to be used in the Precessional Transmissions applications

THEORETICAL AND EXPERIMENTAL MODELLING OF THE TRIBOLOGICAL BEHAVIOUR ASPECTS OF CONTACT ELEMENTS IN THE PRECESSIONAL GEARING (PG)

This paper deals with the theoretical-experimental model of the tribological behavior of the contact elements in precessional gears (PG) in the functions of conjugate profiles of linear velocities "convex-concave" or "convex-convex" for the corresponding geometric parameters (ρk i k ρ − r) and the values of the kinematic force parameters (VE 2 , VE i Va) for each concrete position of the ki points. The calculation of the constructivefunctional and kinematic parameters of the “roller-shoe” and “roller-roller” elements of the tribocouple were adjusted for the experimental verification tests on the SMT-1 installation and adapted to the specific test conditions of the tribocouples with conformal contact of gear teeth made of plastics, which will be subjected to sliding friction and rolling processes of the concrete tribocouple elements