The conditions of contact interaction (pressure, displacement, temperature) of the surfaces of machine parts as the basis for their design and improvement are considered. It is noted that physics is the theoretical basis of the mechanics of interaction of surfaces. A structural hierarchy of interaction types is proposed. The place of mechanical interaction among known to science four types of interaction is defined: strong, weak, electromagnetic and gravitational. A hypothesis has been put forward and justified that in a given range of sizes, mechanical interaction can be considered the fifth interaction between the material objects of the world

We analyzed the methods of determining the characteristics of friction based on the experimental studies using the damped oscillations of a pendulum. It was established that the available studies into characteristics of viscous friction lack the analytical description of the process of damped oscillations at viscous resistance and recommendations regarding practical calculation of the characteristics of friction. Here we propose a theoretical model of the swinging pendulum in the cylindrical sliding supports with a lubricant. It is demonstrated that for a pendulum in the lubricated sliding supports, the process of oscillations is described by a second order differential equation with viscous resistance, proportional to the deflection velocity of the pendulum.It is found based on the solution of the equation that the ratio of adjacent amplitudes of damped oscillations is a constant magnitude, hence it follows that the absorption coefficient is constant over the entire process. We established, based on the theoretical model of pendulum oscillations, that for the viscous friction the absorption coefficient is equal to the doubled logarithmic damping decrement and is determined by one or a cycle of oscillations. The formulas are received for calculating the indicator of dynamic viscosity of a lubricant in the contact by the decrement of pendulum oscillations damping. The developed procedures for determining the characteristics of viscous friction are applied to examine the contact- viscous properties of different combinations of lubricating and design materials. The results received are aimed at searching for design and technological solutions in order to reduce the energy losses to friction in the sliding supports of machines.

This study investigates the technological and chemical causes of early zinc-coating degradation on cold-formed steel sections produced from DX51D+Z140 galvanized coils. Commercially manufactured products exhibiting early corrosion symptoms were used in this study. The entire processing route, which included strip preparation, cold rolling, hot-dip galvanizing, passivation, multi-roll forming, storage, and transportation to customers, was analyzed with respect to the residual surface chemistry and process-related deviations that affect the coating integrity. Thirty-three specimens were examined using electromagnetic measurements of coating thickness. Statistical analysis based on the Cochran’s and Fisher’s criteria confirmed that the increased variability in zinc coating thickness is associated with a higher susceptibility to localized corrosion. Surface and chemical analysis revealed chloride contamination on the outer surface, absence of detectable Cr(VI) residues indicative of insufficient passivation, iron oxide inclusions beneath the zinc coating originating from the strip preparation, traces of organic emulsion residues impairing wetting and adhesion, and micro-defects related to deformation during roll forming. Early zinc coating degradation was shown to result from the cumulative action of multiple technological (surface damage during rolling, variation in the coating thickness) and environmental (moisture during storage and transportation) parameters. On the basis of the obtained results, a methodology was proposed to prevent steel product corrosion in industrial conditions.

In the course of this research in the field of automotive technology, systematic patterns and features of wear of structural materials with wear-resistant coatings that were applied using various technologies, depending on the change in friction modes, were revealed. Our research led to the identification of physical parameters of tribological properties and their changes in the friction process. An interesting property discovered in the course of our work is the fact that changing the contact area several times does not significantly affect the change in the friction coefficient. Instead, changes in the coefficient of friction are mainly related to the chemical composition of the secondary structures that are formed during friction. An important aspect of our findings is that the change in the coefficient of friction is usually due to the chemical composition of the secondary structures, which in turn depend on the chemical composition of the base material, the characteristics of the coating, the characteristics of the environment and the temperature conditions in the friction zone. An analysis of the chemical composition of secondary structures formed during friction was carried out, which allows for a deeper understanding of wear mechanisms and creates opportunities for optimizing materials and coatings in the field of automotive technology.