A. V. Morozov

Mechanical and tribological properties of nanostructured coatings based on multicomponent oxides

The mechanical and tribological properties of thin (up to 300 nm) oxide coatings that are produced by the carboxylate method and have various chemical compositions and thicknesses and are deposited on substrates from different materials (steel or quartz glass) have been assessed. The study involves the surface examination and the determination of the surface roughness of specimens using optical and atomic force microscopes, the determination of the elastic properties of the coatings based on indentation results, as well as the study of their tribological behavior during dry and lubricated sliding.

Method of evaluating the coefficient of friction of frost-resistant sealing rubbers

The results of an experimental study of the effect of the normal pressure in the range of 0.1–0.3MPa, a velocity of sliding of 1–100 mm/s, and a bulk temperature of 22 to–27°C on the coefficient of sliding friction of an elastomer–steel friction pair have been presented. Two types of elastomeric materials have been considered, i.e., frost-resistant rubber based on synthetic propylene oxide rubber and this rubber filled with the antifriction additive of ultrafine polytetrafluoroethylene powder in an amount of 1 weight part per 100 weight parts. The results have shown the efficiency of filling rubbers with ultrafine polytetrafluoroethylene; the coefficient of sliding friction at temperatures below–15°C decreases by more than two times.

Experimental determination of static and dynamic coefficients of sliding friction of epilam-coated materials

The effect of the method for depositing epilam coatings on materials on the static and dynamic coefficients of sliding friction is experimentally studied. Experiments were carried out using the pin-on-plate arrangement under dry friction conditions at a constant velocity of sliding under pressures of 0.5–5 MPa. It has been found that, for a like friction pair made from the 14Kh17N2 steel, the deposition of epilam coatings on materials reduces the coefficients of friction, but the wear resistance of the coated materials changes only slightly because the epilam film has a molecular-layer thickness. Thermovacuum tests carried out at T = 350°C under a pressure of 10−6 Torr have shown the loss of the antifriction properties of the materials covered with the 6SFK-180-05 epilam.

Wear mechanisms of structural steels and effect of wear on their mechanical and acoustic properties during tension

Optical and scanning electron microscopy have been used to study the wear mechanisms of structural steels with various structures and strengths, as well as to assess their mechanical and acoustic properties after friction. The prevailing wear mechanisms have been revealed; they are governed by the strength and structure of the steels and involve the refinement and rotation of grains, the formation of parallel rows of microcracks, the strain dissolution of cementite, and martensitic transformation, as well as the formation of seizure sites in the friction contact zone, shear and intergranular pores, and microcracks. The low-carbon steel with a ultrafine-grained structure has demonstrated a high wear resistance. Friction for 3000 h had a weak effect on the mechanical properties of the steels during tension.

Experimental and theoretical evaluation of the deformation component of the coefficient of friction

An analytical model for the calculation of the deformation component of a friction force in sliding of a hard spherical indenter on a viscoelastic material that is modeled as a Kelvin solid is constructed. The influence of mechanical properties of a material and slip velocity of an indenter on the contact characteristics and deformation component of the coefficient of friction is studied. An experimental method for estimation of deformation loss under friction of a high-elasticity material is proposed. A comparison of the results obtained with the use of theoretical model with experimental data is performed.

Experimental estimate of tribological characteristics of epilam-coated materials that operate in threaded joints under dry friction

Friction in the threaded joint of a screw and nut, the surfaces of which are treated by an epilam, is experimentally studied and an analytical engineering calculation of the coefficient of friction in this threaded joint is presented. Results of the study show the efficiency of the method for depositing a molecular film of the fluorine-containing surfactant (epilam) in order to reduce the friction losses in the screw-nut joint. It is shown that the coefficients of dynamic and static friction in the threaded joint are substantially smaller than those for the material without an epilam coating. The wear resistance of the epilam-coated materials increases due to the formation of a solid lubricant on the surfaces of the materials in contact. The results of the study show that the ultrathin epilam film prevents the occurrence of seizures in the threaded joint. The thermal tests have demonstrated that, after heating the epilam-coated material to a temperature of over 300°C, the coating loses its unique antifriction properties.

Tribological studies for developing friction modifiers in the wheel–rail system

In this work, friction modifiers in a wheel–rail system and their operation mechanism are considered. Three stages of a complex tribological study and tribological tests are applied within the development of friction modifiers and estimation of their tribological properties. The first stage (Institute of Element and Organic Compounds, Russian Academy of Sciences) is to elaborate hydroalcoholic soluble compounds and polymeric binders, as well as of methods of applying them to steel surfaces, and to study their tribological characteristics using an I-47 friction machine. The second stage (Institute of Mechanics Problems, Russian Academy of Sciences) is devoted to probing of tribological characteristics and durability of the elaborated composites on a tribometer, which allows to implement a cylinder–plate contact interaction under full slip conditions. The third stage (JSC “Railway Research Institute”) is aimed at studying the tribological parameters of the developed modifier composites at rolling-sliding conditions under real contact pressure of 1200 MPa.

Video-tactile pneumatic sensor for soft tissue elastic modulus estimation

BackgroundA new sensor for estimating elasticity of soft tissues such as a liver was developed for minimally invasive surgery application.MethodsBy measuring deformation and adjusting internal pressure of the pneumatic sensor head, the sensor can be used to do palpation (indentation) of tissues with wide range of stiffness. A video camera installed within the sensor shell is used to register the radius of the contact area. Based on finite element model simulations and the measured data, elastic modulus of the indented soft tissue can be calculated.Results and conclusionsThree phantom materials, namely plastic, silicone and gelatin, with varied stiffness were tested. The experimental results demonstrated that the new sensor can obtain highly reliable data with error less than 5%. The new sensor might be served as an instrument in laparoscopic surgery for diagnosis of pathological tissues or internal organs.

Friction of bicomponent coatings condensed from metal vapors

Comparative tribotests of single-component and bicomponents coatings condensed from In and Al vapors have been carried out. It has been found that the coatings produced by the codeposition of these metals have the best tribological characteristics. It has been shown that probable causes of the decrease in friction and the increase in the wear resistance of these coatings compared to those of single-component and lamellar systems is the reduction of strain hardening due to the mutual movement of clusters of the deposited metals and to the arrest of fatigue cracks on the boundaries of these clusters.

Young’s Modulus Estimation of Soft Tissues by Video Tactile Pneumatic Sensor

An indentation technique is one of effective methods to determine the elastic modulus of materials using information about contact geometry, indenter shape and applied load. This paper presents a device and a method that allow us to estimate elastic modulus of soft materials through indentation by video tactile pneumatic sensor. The device is a sealed metal cylinder ending with a soft silicone shell of a semispherical shape with 5 mm radius. During penetration by the silicone tip into investigated material the measured parameters are contact radius and displacement of the central point of the shell.