MATHEMATICAL MODELLING OF VIBRATIONS OF NON-UNIFORM RING-SHAPED ULTRASONIC WAVEGUIDES

The article describes technique for modelling of ultrasonic vibrations amplifiers, which are implemented in the form of non-uniform ring-shaped waveguides, based on application of harmonic balance method. Bending vibrations of the waveguide are described by means of non-uniform integral and differential equations equivalent to Euler–Bernoulli equations in order to simplify calculation of amplitude-frequency characteristics of vibrations, particularly, to exclude the need of working with singular matrices. Using harmonic balance method, equations of vibrations are reduced to overdetermined non-uniform linear system of algebraic equations, which least-squares solution is determined by means of pseudo-inverse matrix. On the basis of analysis of numerical example possibility of existence of variable-sign and constant-sign vibration modes of the waveguide is shown and it is determined that for realization of amplifying function it is necessary to use waveguide at constant-sign vibration mode. The constant-sign vibration modes are combinations of bending defor-mation and extensional deformation of central line of the waveguide and they are detected due to accounting extensibility of the central line in equations of vibrations. Validity of the obtained results is confirmed by comparing them to the results of modelling by means of finite element method.

METHOD OF SELECTING THE OPERATION PARAMETERS OF ELECTRIC SPINDLE WITH AEROSTATIC SUPPORTS FOR SEPARATION OF SEMICONDUCTOR PLATES TO CRYSTALS. PARTS 2–3

The article presents the results of studies of the shaft oscillation processes of a precision horizontal highspeed electric spindle with aerostatic radial and axial supports, used at Planar OJSC in equipment for separation of semiconductor plates into crystals. The studies were carried out using the developed mathematical models that take into account the design features of these electric spindles, including the cantilever mounting of the cutting tool, the imbalance of the diamond disc with the mandrel and the mass ratio of the main components of the electric spindle, as well as the results of their full-scale tests. Based on the analysis of the data obtained, regularities are shown that connect the amplitude values of the oscillations of the electric spindle shaft with the imbalance of the diamond disc with the mandrel and the rotational speed of the electric spindle, which made it possible to propose engineering dependences for choosing the permissible values of the imbalance and rational, from the standpoint of resonance conditions and permissible shaft oscillations, rotational speed of the electric spindle. Recommendations have been developed for the creation of a system for monitoring and active control of the parameters and functioning of the electric spindle in the process of separating semiconductor plates into crystals, which make it possible to use the resonant mode of radial oscillations to improve cutting conditions, excluding direct contact of the working surfaces of aerostatic supports, their seizure and loss of performance of the electric spindle. The article presents a method of selecting the operation parameters of a high-speed precision horizontal electric spindle with aerostatic radial and axial supports and a cantilever mounting of a diamond cutting disc. It is based on the analysis of the simulation results of shaft forced oscillations and data on the shaft oscillations during the operation of the electric spindle with different rotation frequencies and imbalances. The results obtained can be used to monitor shaft oscillations during the operation of the electric spindle, while the high operation efficiency of which is achieved by adaptive control of rotation frequencies taking into account the amplitudes of these oscillations.

AUTOMATIC TRANSMISSIONS. COMPLEX OF ALGORITHMS OF “CLUTCH-TO-CLUTCH SHIFTS” TECHNOLOGY: ANALYSIS OF ARCHITECTURE, GENERALIZED STRUCTURE, DEVELOPMENT. PART 2

The article continues the series of the author publications, which considers the main provisions of the “Clutch-to-Clutch Shifts” (CTC) technology — technology for automatic controlling the switching of automatic transmission (AT) stages, used in the global mass production of vehicles, hybrid and battery electric vehicles. It provides high-quality shifts, brought to the level of continuously variable transmissions. Development of power units in recent years has led to a rapid increase in the number of AT stages, which is accompanied by a complication of kinematic schemes, designs, control algorithms and, in general, an increase in the role of mechatronic control systems (MCS) in ensuring their high technical level. Effectiveness of the CTC technology depends on the perfection of the algorithms used. But their composition is not specified, which, with a large amount of information, makes it difficult for potential users to navigate in this set. In this paper, we propose (for the first time in the Russian language) the generalized structure of a set of standard algorithms necessary for the implementation of this technology in the AT MCS, which is developed on the basis of their selection from a pre-formed database of patents and publications on the theory and technology of AT control, following classification and grouping by functional purpose. For each item of the structure, there are links to patents with matching names. Detailed descriptions of several typical CTC algorithms in the AT MCS of General Motors patents are given.

NEW STEELS AND TECHNOLOGIES FOR NITRIDED PARTS OF LONG LIFE MACHINES

The analysis of the used steels for nitrided parts is carried out. On the basis of a new methodology for increasing the strength of structural steels and parts, new scientific approaches and practical solutions are proposed and considered for the creation of gear wheels strengthened by nitriding both when using aluminum containing steels and a new material, 40ХМФА (40KhMFA) steel, that does not contain aluminum. To improve the efficiency and manufacturability of parts production from aluminum-containing 38Х2МЮА (38Kh2MYuA) steel, widely used in mechanical engineering, a fundamentally new technology of preliminary heat treatment of part blanks, “incomplete quenching”, has been developed, which provides both an increase in the machinability and accuracy of large-sized gear wheels, and an increase in strength due to the elimination of flaking of nitrided layer. The research results are presented on 40ХМФА (40KhMFA) steel, which does not contain aluminum, has increased heat resistance, hardenability and workability of parts, as well as the characteristics of the hardened layer. The nitrided layer of gears with a thickness of 0.5–0.7 mm does not contain brittle components, which, with a core hardness of 300–320 HB, also excludes its flaking and subsequent destruction of parts. The use of 40ХМФА (40KhMFA) steel makes it possible to solve the problems of reliability and life of large-sized nitrided gears, but it is also promising for the entire range of gears with internal gearing, as well as parts of movable spline gearings and fine-modular gears in order to replace carburizing with nitriding.

DETERMINISTIC ANALYTICAL MODEL OF RESISTANCE TO DEEP CONTACT FATIGUE OF A STRESSED MATERIAL

The stress state of the surface layer in the contact zone of the mating teeth of cylindrical gears is considered. It is shown that under contact loading, the stress state of the surface layer is inhomogeneous and changes with the distance from the surface. It is established that the value of the equivalent tangential stresses does not depend on the standard size of the gears, but is determined by the surface contact stresses σH. Moreover, the depth of occurrence of the maximum equivalent tangential stresses depends on the gear modulus (the reduced radius of curvature of the mating surfaces of the teeth) and, to a lesser extent, on the surface contact stresses σH. The inhomogeneity of the stress state and the structural characteristics of the diffusion layers of surface-hardened gears is a prerequisite for the appearance of critical zones in them, in which fatigue processes of contact failure can originate and develop. A deterministic analytical model of the resistance to deep contact fatigue of hardened tooth surfaces is proposed, based on determining the service life of the gear before the appearance of progressive deep contact chipping of the active tooth surfaces with a regulated variation of the microhardness values in different zones of the diffusion layer.

ENERGY EFFICIENCY OF GEARBOXES APPLICATION IN POWER UNITS OF ELECTRIC VEHICLES

With all advantages, electric vehicles have a significant disadvantage — a relatively small driving range on a single charge of the traction battery compared to cars using hydrocarbon fuel. The solution to the issue is to choose a rational structural scheme of an electromechanical power unit to obtain its high energy efficiency regardless of the operating conditions. A significant number of electric vehicles produced today either do not contain gearboxes or contain single-speed reducers. The use of a multi-speed gearbox solves the problem of adapting the working processes of a traction electric motor to the loading conditions, bringing its efficiency as close as possible to the range of highly efficient values. Calculated estimation of energy consumption of the MAZ-4381EE electric delivery truck is carried out in the paper for various versions of the mechanical part of power unit: without a reducer, with the use of a reducer and two types of two-speed gearboxes (shaft and shaft-planetary). The evaluation is made based on consideration of the European test driving cycle NEDC, taking into account the use of efficiency maps of the traction induction electric motor. The calculation results showed that the use of two-speed gearboxes can reduce the total energy consumption by more than 1.8 times compared to a power unit with a high-torque motor and without a gearbox.

DEVELOPMENT OF THE COMPONENT COMPOSITION OF THE BIODEGRADABLE LIQUID LUBRICANT FOR SAW CHAINS

The procedure of working out of the component composition of the biodegradable liquid lubricant for the saw chains is shown. The experimental statistical mathematical model is developed for the optimization of the formulation of the main base taking into account the necessary viscosity and temperature parameters. At the same time the kinematic viscosity of the base body at the temperature of 40 °C and its pure point are chosen as the optimization criteria and the following three factors are used as the optimization parameters: the content of vegetable (rapeseed) oil in the composition, the viscosity of mineral oil at the temperature of 40 °C and the content of an adhesive additive in the base composition. The component composition of the lubricant is adjusted to achieve the required level of tribological properties of the saw chain oil and to ensure the stability of all its characteristics during storage (at least 12 months) and operation at a given level of biodegradability (at least 90 %). In particular, the biodegradable calcium sulfonate grease OIMOL KSC BIO was selected as an additive to improve tribological parameters. The special adhesive additive for vegetable oils of the Petrolad 484BD brand is used to increase the sedimentation stability, and the highly refined oil of group III according to the API standard is recommended to use as a mineral component. The developed lubricant has the following characteristics: density at 15 °C — 926 kg/m3, kinematic viscosity at 40 °C — 47.3 mm2/s, kinematic viscosity at 100 °C — 9.9 mm2/s, viscosity index — 202, pour point — –28 °C, flash point — 272 °C, critical load — 872 N, welding load — 1,600 N, wear index at 200 N — 0.39 mm, biodegradability — 93 %.

CONTACT PROBLEM OF INTERACTION OF A GUIDE ROLLER WITH A MINE CONDUCTOR

The article considers the force interaction contact problem of a guide roller with a mine conductor during the movement of a mine lifting conveyance on the example of a model problem of the contact interaction of a torus with a beam. The model problem analytical solution is considered, a finite element model of the system under study is developed. Contacting bodies materials elastoplastic behavior was taken into account when solving the problem. The various contact types between guiding roller and the conductors were considered. The values of critical loads leading to plastic deformations occurrence in a conductor with various types of contacts are determined and their relationship with the friction coefficient value is established. Comparative analysis of the obtained analytical and numerical results demonstrates a high degree of correlation.

RATIONAL FOR REHEATING IN THE AUTOMATED LINE FOR RING BLANKS PRODUCTION

Features and requirements to the use of reheating of ring blanks in the conditions of production on the automated line are considered. An assessment is given for a technological temperature state of ring blanks at various stages of production under conditions of the automated line. For assessment of rational for reheating at production of ring blanks, a classification of ring manufacturing technology is proposed with the production of a pressed non-core blank in an open die, with the production of a pressed profile blank in a closed die, with the production of a pressed profile blank in a stamp with reverse extrusion. The technology of ring rolling with the production of a pressed non-core blank in an open die is the most economical and does not require the use of reheating in the manufacture of rings made of medium-alloy steels. The technology of ring rolling of a profile blank obtained in a closed die does not require the use of additional heating after pressing, in the case of manufacturing rings with a simplified profile on the outer or inner diameters of the ring. In the manufacture of rings with a more complex profile on the outer and inner diameters of the ring, as well as rings made of high-alloy steels, the final decision on the need for additional heating is made depending on the temperature of the end of intensive plastic deformation for the selected steel grade of the ring. The technology of ring rolling with the production of a pressed profile blank in a die with reverse extrusion requires the use of reheating after the pressing operation before the ring rolling operation, and is recommended for the manufacture of rings from medium- and high-alloy steels with a complex profile section on the outer and inner diameters, wall thicknesses, with a ratio of wall thickness to outer diameter D within h / D = 0.011...0.016 and with a ratio of wall thickness to ring height L within h / L = 0.020...0.041. The proposed recommendations are intended for use in the development of technological support for the operation of the automated ring-rolling complex at OJSC “BELAZ”.

DEVELOPMENT OF THE METHOD AND OPTIMIZATION OF THE COMPOSITION AND MODES OF OBTAINING THE BIODEGRADABLE GREASE WITH THE LITHIUM-CALCIUM THICKENER

It is noted that the development of biodegradable lubricants is an integral part of the development of a modern “green” economy. The distinctive features of the proposed method are described for producing a biodegradable grease on a mixed lithium-calcium thickener, providing for the introduction of alkaline initial components of the dispersed phase (lithium hydroxide monohydrate and calcium hydroxide) into the reaction mass not in the form of their aqueous solutions, but in a powdery state, and the exception of prolonged exposure to water and high temperature on a component of a dispersion medium of plant origin (rapeseed oil) in the process of lubricant synthesis. Along with this, it was proposed to use a highly refined oil of group III according to the API (American Petroleum Institute) standard as a mineral component of the dispersion medium. This provides, in aggregate, the higher stability of the rheological and tribological characteristics of the grease (for at least 12 months) at a given level of biodegradability. The experimental-statistical mathematical model of the process of obtaining the biodegradable lithium-calcium grease is developed, which makes it possible to determine the parameters of the component composition (the content of the mixed lithium-calcium thickener in the grease and the content of lithium stearate in the mixed thickener) and the synthesis modes (the heat treatment temperature of the reaction mass) to achieve the given level of the main characteristics of the finished grease (penetration, dropping point) while ensuring its biodegradability of at least 80 %.