Introduction. Transverse axisymmetric oscillations of a bimorph with two piezo-active layers, piezoelectric and piezomagnetic, are studied. This element can be applied in an energy storage device which is in an alternating magnetic field. The work objective is to study the dependence of resonance and antiresonance frequencies, and electromechanical coupling factor, on the geometric parameters of the element.

Materials and Methods. A mathematical model of the piezoelement action is a boundary value problem of linear magneto-electro-elasticity. The element consists of three layers: two piezo-active layers (PZT-4 and CoFe₂O₄) and a centre dead layer made of steel. The finite element method implemented in the ANSYS package is used as a method for solving a boundary value problem.

Results. A finite element model of a piezoelement in the ANSYS package is developed. Problems of determining the natural frequencies of resonance and antiresonance are solved. Graphic dependences of these frequencies and the electromechanical coupling factor on the device geometrics, the thickness and radius of the piezo-active layers, are constructed.

Discussion and Conclusions. The results obtained can be used under designing the working element of the energy storage device due to the action of an alternating magnetic field. The constructed dependences of the eigenfrequencies of the resonance and antiresonance on the geometric parameters of the piezoelement provide selecting the sizes of the piezo-active layers for a given working frequency with the highest electromechanical coupling factor.

Introduction. The paper is devoted to the evaluation of cracking of white layers formed on the surface of the rail while in operation. Cracks are detected in the white layer of rail steel after one thousand test cycles. This is due to tensile and shear stresses on the surface of the wheel-rail contact spot. The paper presents the study results of the morphological characteristics of the white layer on the rail surface.

Materials and Methods. The object of study (rail surface after operation) was examined under a microscope. Then, a two-dimensional model of finite elements of the plane deformation was developed to simulate the dynamic characteristics of the white layer cracking. Mathematical models describing crack propagation are proposed. For this, we applied the criterion of the elastic plastic fracture mechanics, the J-integral method. The SYSWELD program performed numerical modeling of the formation of a white layer and the distribution of residual stresses.

Results. Optical images of the microstructure of the cross section of a white layer on the rail surface after operation are presented. Two different types of cracks were fixed at the trailing edge of the white layer of the samples studied. The SYSWELD program visualized fragments of simulating the mechanism of the white layer formation with the distribution of residual stresses, compression, and tension. The calculation results show that the values of the J-integral for all three cracks slightly decrease if the crack length reaches 10-50 gm.

Discussion and Conclusions. The results obtained are applicable to assess the wear resistance of rail steels and predict the direction of crack growth. Comparisons of J-integral maxima have shown that under identical load conditions, crack no. 1 is likely to grow faster than cracks nos. 2 and 3. With an increase in the length of the crack, the maxima of the J-integral of all three cracks decreased.

Introduction. Loss of stability and buckling of a round plate may be observed if the plate is loaded on the lateral surface. The solution to this problem is based on a bifurcation approach. In this case, a plate is considered as a nonlinear elastic body. It is important to choose the relation between stresses and deformations in sustainability problems of nonlinear elasticity. Simple laws of state (constitutive equations) were considered in early works devoted to this problem, for example, material of the “harmonic type” (Sensenig).

Materials and Methods. Equations of neutral equilibrium for round plates made of Murnaghan and Blatz-Ko materials are obtained. Assuming a uniform initial deformation on the plate, the stability problem is considered. Strict threedimensional neutral equilibrium equations provide exploring related forms of equilibrium taking into account physical and geometric nonlinearity. Derivation of these equations is based on the application of the theory of superposition of small deformation on the final one.

Results. Progress in solution to the corresponding secular equation (with non-linear parameter entry) for practically important laws of elasticity of Murnaghan and Blatz-Ko is possible using the numerical methods only. The developed method for calculating bifurcation values of loading parameters makes it possible to analyze the effect of nonlinearity. Discussion and Conclusions. The influence of physical and geometric nonlinearity on the upper critical value of the initial deformation parameter is explored. The results obtained can be used under the assessment of reliability of elastic third-order moduli for various physical materials. Data on these moduli is still scarce. The numerical research has shown that the constants given in some sources should be treated with caution. The use of elasticity moduli in the law of state of Blatz-Ko is also discussed.

Introduction. The study results on the multicontact shock-vibrating machining using a ball-rod hardener are presented. Methods of surface plastic deformation processing, their advantages are described. The tool circuit diagram is given. Features, technological advantages, and the application area of the ball-rod hardening are specified.

Materials and Methods. When conducting theoretical studies on the processing, factors, which affect the quality of the surface layer of the machined parts, were established. Dependences are given for calculating the surface roughness, the hardened layer depth, and the deformation ratio under ball-rod hardening. While studying the generation of residual stresses, the dependence for calculating the residual stresses generated in the surface layer of the machined part was specified.

Results. The experimental findings of the processing requisite for verification of the adequacy of the theoretical models, as well as the routine of the experiments, are presented. A table and graphs clearly confirming good convergence of the theoretical and experimental data are given (the difference does not exceed 20%). Residual stresses in the surface layer are compressive which enables to predict high performance properties of the machined parts. The value of residual stresses on the workpiece surface is in the range of 130÷200 MPa. The depth of compressive residual stresses is in the range of 0.9-1 mm. The fatigue characteristic variation, the ultimate stresses of the cycle in depth, which affects the endurance limit, is calculated. It has been established that the processing of workpieces by a ball-rod hardener provides increasing the ultimate cycle stress under repeated loading by 27-35%.

Discussions and Conclusions. The design methodology of technological process of ball-rod hardening can be used under the development of production at the machine-building enterprises. In accordance with the recommendations, the limits of the required quality parameters of the workpiece surface layer are set; the parameters of the ball-rod hardener, the interference fit and the radius of rod sharpening are selected. Quality parameters of the surface layer are calculated. Correction of the selected modes and re-calculation of the parameters of the machined surface are carried out until all the specified characteristics are located within the required limits.

Introduction. The paper is devoted to the comparison and evaluation of the quality of a car using the method of mathematical simulation of the integral performance index. The work objectives were to develop a mathematical modeling technique for the integral performance index, to draw up a step sequence of quality assessment, to analyze most common brands of passenger cars on the domestic market, to sum up and validate the result obtained.

Materials and Methods. The sequence of simulating the integral performance index is proposed. Numerical modeling of the integral performance index is carried out on the example of six most common brands of passenger cars on the domestic market.

Results. A method of modeling the integral performance index is developed. A step sequence of the analysis is described. An additive form of determining the integral performance index which provides combining single, unrelated quality indices into a complex indicator in the process of comparison is proposed.

Discussion and Conclusions. The proposals presented can be used in the process of assessing and diagnosing the competitiveness of not only cars, but also of other products with a large set of independent quality indicators.

Introduction. The mobile machine design is impossible without considering the vibration parameters of their units. This requires the development of specialized dynamic models that take into account the probabilistic nature of these parameters. The root cause for the occurrence of vibration effects is the profile irregularity of the mobile machine path, and the variability of physicomechanical characteristics of the soil. Problems that consider these features are solved linearly with sufficient accuracy; but in multidimensional dynamical systems, such an approach is unacceptable due to the presence of a large number of interrelationships. The work objective is to conduct a comparative analysis of the efficiency of existing calculation methods of statistical characteristics of uncorrelated external actions as applied to a mobile machine presented as a multidimensional dynamic system with actions having different correlations.

Materials and Methods. External actions in the multidimensional dynamical systems are considered in a matrix form. When calculating statistical characteristics, intercouplings in the spectral density matrices are taken into account. The elements of the main and secondary diagonals are determined; the correlations between the effects are taken into account. These features significantly complicate the calculations. So, to get matrices of uncorrelated actions, the matrix of external actions is reduced to a diagonal form.

Results. A numerical comparison of spectral densities and intensity of the mobile machine oscillations under variation of speeds and nature of the soil fertility microprofile was carried out using various methods of calculation. Certain characteristics of spectral densities and oscillations of mobile machines of agroindustrial complex enabled to develop recommendations on the practical application of the presented dependences for designing this machinery.

Discussion and Conclusions. The results of solving the matrix of spectral densities of external actions by various methods are presented on the diagram of spectral oscillation velocities. The analysis of characteristic curves has shown that the identical results, regardless of the calculation method, are obtained only for machines with weak functional relations under the uncorrelated external action of the soil fertility. For some cases, the resonance machine speeds are set. The effect of irregularities of the soil fertility on the oscillation intensity of the machine units and the dispersion of loads on the units is shown in the graphical representation.

Introduction. It should be noted that the study on the problem of the effect of the mass of parts on the vibration-abrasive processing is insufficient. In the works of A.P. Babichev and M.A. Tamarkin, the fact of such an effect is mentioned, but the degree and mechanism of the effect are not disclosed. In the metal removal formulas, only the number of interactions leading to microcutting is taken into account. The present work objective is to determine the effect of the mass of parts on the metal removal rate under vibroabrasive machining.

Materials and Methods. An empirical, i.e., experimental, approach is used. Parts from D16 and 30KhGSA materials which are widely used in the aviation industry were selected as samples. To change the mass, holes were drilled in the blanks; lead was poured into some samples, and plugs made of the same material as the blanks themselves were clogged into the others. Thus, experiments were carried out with solid, hollow, and weighted with lead samples. The working abrasive medium was scrap of grinding wheels of 40 x 80 mm, 25 grain size, and of trihedron prisms of 15 x 15 mm, 16 grain size. The experiments made it possible to clearly demonstrate the effect of grain size on the removal rate of the workpiece.

Results. The parameters of the effect of the mass of parts on the removal rate under vibroabrasive processing are determined. The results obtained show the removal per unit area. The data are approximated by the least squares method with a linear function. A version of its distribution is selected using the Fisher statistical criterion.

Discussion and Conclusion. It is shown how the workpiece mass determines the specific removal rate under the vibroabrasive machining. In the future, the database which is used to determine the effect of the work material characteristics on the process under consideration should be replenished. This will allow introducing a correction factor for the influence of mass in the metal removal formula, which will provide more accurate prediction of metal removal at the design stage of technological processes of vibration-abrasive machining.

Introduction. The paper is devoted to the analytical determination of general criteria for predicting the wear resistance of heavily loaded friction couples, in particular, stamping tools, operating under various loading conditions. The proposed system of criteria is based on physical dependencies that link the basic wear index, i.e. the number of loading cycles NF with crack resistance parameters n and C. The work objectives were the development and analytical foundation of the calculation technique that provides for predicting the wear resistance of the stamping tool for various loading conditions, as well as the predetermination of experimental verification of the efficiency of the developed methodology.

Materials and Methods. Mathematical models that link the key criterion of wear-resistance, the number of loading cycles NF with crack resistance parameters nand C, are proposed. An analytical verification of the proposed models is carried out.

Results. Mathematical models are developed for predicting the wear resistance of a stamping tool operating under various loading conditions. In particular, for the following cases: under sliding and rolling friction of the tool on a plastically deformable metal, for conditions of thermo-mechanical contact fatigue, for high-cycle brittle contact damaging, for pulsating contact on a plastically deformable metal, as well as for combined types of frictional contact.

Discussion and Conclusions. The results obtained can be used in the design and structural optimization of the stamping tool operating under various loading conditions, as well as in predicting its life cycle.

Introduction. To increase the decision-making efficiency at the enterprise, it is advisable to use a special software package of intellectual support. Such a product is necessary when designing an information security system and increasing its invulnerability during modernization or configuration changes. Research objectives are as follows: to develop an algorithm and a mathematical model of the software package for intellectual decision support.

Materials and Methods. The decision support method under designing an information security system is based on the use of a neural network (multilayer perceptron). For an objective assessment of the initial security of an information system (IS), a mathematical model for the analysis of security events is developed.

Results. The statistics of malicious attacks on the IS of enterprises is analyzed. The need for timely and accurate modernization of the information protection system is determined. Important characteristics of the designing an information security system are the speed at which the result is obtained and the reduction in the residual risk of IS. In this regard, the use of artificial intelligence systems in the process of determining the best set of protection subsystems is important. The threats to cyber security (CS) are classified. The main classes of security events are defined. A mathematical model of the neural network is developed; the input parameters of its operation are indicated. The current enterprise IS generates numerous events which necessitates the automatic collection and analysis of data from subsystems for registering IS objects. The process of analyzing security events is considered in detail since the adequacy of the generated design decisions depends on the correctness of the data obtained in this way. The algorithm of the software package is formed.

Discussion and Conclusions. The results can be used in the design of the information security system at the enterprise. In addition, CS administrators can use the developed software package to adjust the configuration settings of information security tools. The proposed solution will minimize the destructive influence of the developer of the security system which may and happen to be subjective.

Introduction. Digital systems that control the maintenance of separate mechatronic process facilities (MPF) and sets of production machines are mainly considered. Numerous issues on maintaining the reliability of the condition and emerging malfunctions, as well as the multifactorial nature of the using the existing monitoring and diagnostic systems, are noted. In this regard, the relevance of the tasks of developing methods of processing equipment maintenance to make decisions under the data veracity and limitation is specified.

Materials and Methods. To analyze the criticality of the technical condition, an assessment of the efficiency of the autonomous control of the device state is formed. The method of the neuro-fuzzy system is used to determine the aggregate criterion of criticality. It is proposed to apply this approach to develop recommendations on equipping a production facility with the necessary means of maintaining overall performance and reliability.

Results. The solution provides predicting the development of the state of mechatronic process equipment, alerting personnel in case of emergency and other dangerous conditions, and, if necessary, updating or adjusting control programs. Provision is made for performing of some of the technical state maintenance functions by the mechatronic facility itself, i.e., equipment self-service. The concept of “autonomous management of the technical condition” is formulated. The system structure and control functions are considered. It is noted that the implementation of the systems under consideration will significantly increase the efficiency of the equipment use. The performance of the autonomous control of the device or MPF in general is evaluated in accordance with ISO 13381-1: 2004. Based on this standard and the data presented earlier, a neural network structure is built to assess the autonomy of state management. The system training efficiency is considered taking into account the standard deviation of the network outputs from the target values of the training sample.

Discussion and Conclusion. A list of the basic control functions at different levels of maintenance autonomy is presented: from alarm for failure prediction to complete maintenance autonomy without the direct involvement of an operator.

Introduction. The artificial intelligence (AI) performance in data storage systems is considered. When working with data, the advantage of its use both in economic terms and for security is determined. The work objective is the introduction of artificial intelligence in data storage systems. The key tasks involve the description of methods for data separation, organization of itsstorage and counteraction to security threats.

Materials and Methods. The data that should be fed into the drives is divided into parts so that it can be restored without one of the parts. This is necessary to be able to access and recover information in the event of a software or hardware failure.

Results. The AI performance under detecting security threats is considered. Since the model implies the interaction of users with data, it was found out how the data access control is carried out and the keys are stored.

Discussion and Conclusions. The use of AI in organizing a data warehouse will speed up the system. Artificial intelligence with built-in machine-learning algorithms will provide responding to a situation that affects the state of the sys-tem. Analysis of the state of the drives will avoid a possible hardware or software failure. Minimization of the human factor in the system operation contributes to the improvement of its work.