Issue № 2(22) Vestnik of Tver State Technical University. Series «Technical Science»

Download issue

• CONDUCTIVITY OF CONTACT CONNECTIONS: DOMINANT FACTORS
  Authors: V.V. IZMAILOV,, A.F. GUSEV
  Abstract: The influence of the parameters of discrete contact of technical surfaces on one of the contact resistance components ‒ constriction resistance ‒ is studied. The dominant factors determining the electrical and thermal conductivity of the rough surfaces contact are the number of contact areas of roughness peaks and their average size. Based on analytical and numerical (computer) models of contact joints, the influence of nominal contact pressure on these factors is analyzed. The adequacy of the analytical and numerical models to the real characteristics of the contact connection has been verified experimentally. It is shown that the real range of possible changes in the average size of the contact areas is very small, and the dominant factor, the targeted change of which can be used to reduce the contact resistance, remains the number of contact areas of the roughness peaks. An example of such a targeted change in this contact parameter is given.
  Keywords: contact of rough surfaces, contact area, number and size of contact areas, contact resistance, constriction resistance, roughness.

• INFLUENCE OF MAGNETIC FIELD ON BRITTLE DESTRUCTION OF FERROMAGNETIC MATERIAL
  Authors: A.N. BOLOTOV
  Abstract: The work is devoted to the study of the influence of a stationary magnetic field on the quasi-brittle fracture of specimens made of a ferromagnetic material – cast iron grade SCh35. It is shown that the anisotropic nature of quasi-brittle fracture is observed in magnetized samples, and the value of mechanical stresses at which fracture occurs somewhat decreases. Cracks dominate, which begin to propagate along the magnetic field lines. A reasonable assumption is made that the magnetic forces acting on the walls of a microcrack stimulate its growth at lower mechanical stresses. The magnetic forces are proportional to the magnetization of the samples to the second power. The maximum effect of the magnetic field is manifested in samples magnetized to saturation, and this condition determines the magnitude of the magnetizing field.
  Keywords: gray cast iron, magnetic field, microcracks, quasi-brittle fracture.

• THE POTENTIAL OF THE MODERNIZED LABORATORY INSTALLATION “ATWOOD MACHINE” FOR STUDYING SLIDING FRICTION
  Authors: A.F. GUSEV, V.V. IZMAILOV, M.V. NOVOSELOVA
  Abstract: A diagram is presented and a description of the design of a laboratory installation for the experimental determination of the sliding friction coefficient, assembled on the basis of the classical Atwood machine, is given. The measurement technique is described and formulas are proposed to calculate the friction coefficient. The advantage of the presented installation is the extremely simple and most reliable loading scheme for the contact of rubbing surfaces - gravitational, which provides stable and absolutely accurate values of both the normal pressure force on the contact and the tangential force. The relative instrumental error does not exceed 0.5 %, which is significantly less than the random error characteristic of experiments measuring friction coefficients. It is recommended to use a modernized setup and methodology to create laboratory work in tribology and triboengineering courses.
  Keywords: tribology, sliding friction coefficient, laboratory work, Atwood machine.

• POWDER LASER CLADDING OF HIGH-SPEED STEEL
  Authors: L.E. AFANASIEVA, I.A. SMOLYAKOVA
  Abstract: The results of metallographic analysis of high-speed steel R6M5 obtained by powder cladding on an automated complex CLT-Yu-5 with multichannel (48 beams) CO2 laser are presented. It is shown that the phase composition of steel is martensite, 10 % of residual austenite and 2 % of V2C carbides. The microhardness of the deposited metal is 8500...9000 MPa. The results of the conducted research may be useful to manufacturers of bimetallic tools with a working part made of fused high-speed steel.
  Keywords: high-speed steel, laser cladding, multi-channel CO2 laser.

• ON SOME CORRELATIONS, RELATED TO WEAR RATE
  Authors: V.V. IZMAILOV
  Abstract: Correlation relationships are considered that describe the dependence of the linear wear rate of a friction contact on the friction coefficient and the hardness of the materials of the components of the friction pair. The relationships were obtained by statistical processing of experimental data relating to the brush-commutator friction pair. A strong correlation has been established between the linear wear rate of the friction pair components and the friction coefficient. A strong positive correlation of the linear wear rate with the hardness of the brush and commutator materials was also discovered, which contradicts the known results indicating an increase in wear resistance with increasing hardness of the rubbing parts. The most probable explanation for this contradiction is given. In addition, this dependence is non-monotonic with a noticeable increase in wear rate if the hardness of the brush material becomes comparable to the hardness of the commutator material.
  Keywords: friction, friction coefficient, linear wear rate, hardness, correlations.

• OPTIMIZATION OF THE INSTALLATION ANGLE OF THE CUTTER OF THE PEAT EDGE CUTTER FROM THE POSITION OF ENERGY INTENSITY OF MILLING
  Authors: А.L. YABLONEV
  Abstract: Peat extraction by milling involves layer-by-layer surface treatment of karst fields. At the same time, the channel strips due to high humidity and reduced load-bearing capacity turn out to be untreated, edges appear that make it difficult to remove moisture from the surfaces of fields and the operation of technological equipment. This problem can be solved by treating the surfaces of the fields with special eyebrow cutters. However, existing models of brow cutters process only one brow in one pass. The concept of a peat brow cutter developed by us, capable of processing both edges of the fields adjacent to the cart channel in one pass, required experimental studies to establish the optimal angle of rotation of the cutter relative to the transverse axis of the machine. In the presented study, which contains the methodology and experimental results, the value of this angle is justified from the perspective of the optimal energy intensity of milling a peat deposit.
  Keywords: peat production field, edge cutter, oblique milling, peat field channel, energy intensity, strain gauging, load cell.

• A MATHEMATICAL MODEL OF THE FORMATION OF AN EXTERNAL DISTURBANCE VECTOR ON THE AXIAL CROWN OF A BOOM-TYPE HEADING MACHINE
  Authors: O.E. SHABAEV, A.Yu. DOVGAN
  Abstract: A complex model of the formation of an external disturbance vector on the axial crown of the executive body has been developed, taking into account the influence of mining and geological conditions and operating parameters of the combine on the process of destruction of the mountain range, which consists of models of the destroyed array and the face surface, finding the coordinates of the tip of the cutter in the face, evaluating the conditions of contact of the cutter with the array, determining the parameters of the process of destruction of the array by cutters crowns for determining the cutting and feeding forces on the cutter, taking into account the fulfillment of the contact condition of the cutter with the face. The adequacy of the mathematical model was assessed by comparing the indicators obtained during model and experimental studies: average fracture power per cycle, theoretical productivity, specific energy consumption per cycle, and the duration of face treatment.
  Keywords: mathematical model, heading machine, cutter, boom, external disturbance vector.

• EVALUATION OF THE TECHNOLOGICAL MANAGEMENT METHOD QUALITATIVE PARAMETERS OF PEAT RAW MATERIALS
  Authors: E.Yu. CHERTKOVA
  Abstract: The issues of quality management of peat raw materials are considered. A technology has been developed for the extraction of milled peat with the intensification of drying in the field to a harvest moisture content of less than 40 % due to the variable height of the total layer, which makes it possible to control the quality of the extracted raw materials and reduce the energy intensity of the process of its processing. Field tests of this technology have been carried out in a peat deposit. The relative humidity indicators of the harvested peat chips in each cycle were determined using two technologies. The results of a comparative analysis of the operational capacity of machines taking into account different technological parameters of production are presented.
  Keywords: milling peat, qualitative parameters, intensification, peat drying, milling depth, processing, moisture content, cyclic collections, operational capacity.

• AUTOMATED CONTROL OF HEAT TREATMENT PROCESS OF COCOA BEANS USING AN ALGORITHM WITH PREDICTIVE MODELS
  Authors: K.B. FAM, P.M. MURASHEV, V.N. BOGATIKOV, S.M. KIEU
  Abstract: The article describes the design and modeling of an automated control system (ACS) based on the UPM controller algorithm for controlling the heat treatment of cocoa beans in a belt conveyor dryer. Heat treatment processes are modeled as a continuous, spatially distributed system with one input and one output, where the controlled variable is the temperature of the incoming drying air, and the controlled variable is the temperature of the product in the drying chamber. The requirements for the software and hardware of the automated control system are presented and discussed. The numerical simulation of the automated control system was carried out using the Matlab application software package. The results of numerical simulation are presented, confirming that the UPM controller is stable and stable with respect to input interference. It is shown that the system provides a rapid response to displacement and elimination of the steady-state error during heat treatment.
  Keywords: MPC regulator, heat treatment, cocoa, automated control, control strategy, mathematical model.

• THE RELATIONSHIP OF AUTOMATED CONTROL AND DESIGN SYSTEMS IN THE MACHINE-BUILDING ORGANIZATIONAL AND TECHNOLOGICAL SYSTEM
  Authors: G.B. BURDO, A.N. BOLOTOV
  Abstract: A new approach to the organization of interaction of automated systems of machine-building enterprises is proposed. It is shown that the effective implementation of the use of automated systems is possible only on the basis of research and optimization of the processes of a machine-building enterprise, and on the basis of analysis and assessment of the quality of performance of functions by participants in various processes of the enterprise. The methodology is based on the identification of the main functional process within which the preparation of production and the release of finished products are carried out, and the time parameter and auxiliary processes are determined. The basic principles underlying the creation of a complex of automated machine-building systems are formulated. The role and place of each of the main functional automated systems are analyzed. The considerations on the sequence of implementation of the project on digitalization of machine-building production are given.
  Keywords: machine-building production, automated design and control systems, process management, production process, life cycle management.

• CONTROL OF DRYING OF CHLORELLA SUSPENSION TAKING INTO ACCOUNT VISCOSITY
  Authors: O.L. AKHREMCHIK, N.V. KUZNETSOV
  Abstract: The results obtained during structural synthesis of microalgae suspension drying control systems are presented. Reduction of dispersion of chlorella powder quality parameters is ensured by using corrective action by viscosity of suspension in temperature controller of drying agent. Viscosity is measured before the slurry is fed to the spray nozzle further incorporated into the instrument control system. The structure of the suspension viscosity meter is considered. As the temperature controller, it is proposed to use a fuzzy temperature controller of the drying agent. Linguistic assessment of controlled and corrective actions is carried out according to three terms on the basis of rectangular belonging functions.
  Keywords: control, viscosity, temperature, variable, fuzzy regulator, drying, suspension, structure.