Tribological properties of rapeseed oils manufactured and processed by different methods and modified by the anti-wear additives were analysed. Tribological tests presented that unrefined rapeseed oil has better wear resistance compared to refined oil. Modification of rapeseed oil with 2% of special biological anti-wear additives has the greatest influence on refined rapeseed oil. Chemical analysis shows that refinement removes acids from oil. Refinement and lower acidity allows more efficient operation of special biological anti-wear additives.

The tribological study of the parameters of piezoactuator when switching over contacts a trib- ocouple deals with of rotation of piezoactuator steady during 500 m when the rotor from polished steel C45 (HRC 50, R _a = 2 μm) is used. Often the rotation speed leaps up to 16-18 min-1. The coating with fluoroli- gomeric material stabilizes the rotation and continuous operation of piezoactuator. The steady rotation speed starts from a 50-m run (350 rotor revolutions, i.e., cycles of repeating impacts on the surface). The lower dam- age of the friction surface takes place after a 500-m run when the rotor is coated with fluoroligomeric mate- rial. Scratch tests show that steel surface with the fluoroligomeric layer has a lower hardness and 20% higher elasticity compared to a noncoated surface.

Investigations presented in this paper were carried out using an originally designed rotary piezoelectric motor of a standing wave tribotester. Test conditions, such as the normal force value in the friction pair, the rotor stop torque value, and the test duration can be programmed and changed in a desirable mode. The rotation speed, covered distance and loading torque of a piezo actuator were measured. Two different coatings (WC-Co8 and TiC15-Co6) were tested as the rotor friction surface and the wear of friction pairs (rotor, counter body) was evaluated after the tests. Investigations reveal an incidental advantage of output parameters of the piezo actuator with the TiC15-Co6 coating on the friction pair. Besides, high hardness of carbide surfaces requires paying more attention to the wear resistance of the frictional material of the counter body.

Purpose: The purpose of this paper is to report on the tribological properties of beef tallow grease and improvements therein through modification with special processing, polymeric compounds and additives. Design/methodology/approach: Pure original beef tallow grease was used as a biological lubricating grease reference material for the tribological research. Beef tallow was modified and synthesized by adding special biological anti-oxidant additives, LZ anti-wear additives, waste polyethylene terephthalate (PET) polymer compounds and thermally processed graphite. Findings: Rheometric measurements indicate that the beef tallow grease modification technology used in this study enables control of the synthesis process to produce lubricants with the required microstructure. Investigation results of the tribological properties of differently modified greases show that beef tallow synthesized with polymer additives efficiently operates together with anti-wear additives to reduce friction and wear. The grease compound with thermally processed graphite has good tribological properties at 300 N load levels. The critical load level of lubricating greases could be significantly increased through the use of anti-wear additives and thermally processed graphite. Originality/value: Investigation results of the tribological properties of differently modified beef tallow greases show that beef tallow synthesized with polymer additives efficiently operates together with anti-wear additives to reduce friction and wear. The critical load level of lubricating beef tallow greases could be significantly increased using anti-wear additives and thermally processed graphite.

The aim of the paper is to describe the ways to increase the reliability of the piezoelectric motors, related to tribological processes of the contact zones piezoelectric transducer—rotor or slider, in which both static forces and ultrasonic two dimensional vibrations are taking place. The problems of frictional wear are dealt with introducing and realizing the concept of adaptive tribological pair with optimal rheological parameters of components, enabling to effect self-diagnostics of the pair by exploiting direct piezoelectric effect of already existing piezoelectric transducers. This will allow for the forecast of durability and its significant increase when using new advanced materials (including nano-particles). Some results of experiments are given, including correlation of diagnostic signals with the parameters of wear.