Ukrainian Journal of Mechanical Engineering and Materials Science

8

Authors: Mykola Karpenko, Marijonas Bogdevicius, Olegas Prentkovskis

In the article the review of the problem of improvement of technology of high pressure hoses cutting on the hand cutting machines is analyzed. Different methods of cutting of high pressure hoses into the billets are overviewed and the quality of edge cuts of hoses is analyzed. The comparison of treatment on automatic cutting machines and on hand cutting machines is carried out. Different experimental techniques of improvement of the quality of edges cutting of high pressure hoses are presented. On the basis of experimental method, a new cutting technology which consists in maximally close fixation of high pressure hoses to the cutting disc is proposed. In the basic design of the hand cutting machine, the only supports are provided, so that the cutting of the edge section of high pressure hoses causes the metal braid loosening. The proposed technology excludes the scrolling and bending of high pressure hoses during cutting, so that the loosening of metal braid is also excluded. In the paper it is shown that the scheme of distribution of cutting forces during the cutting of high pressure hoses is presented and the mathematical model of determination of normal and tangential cutting forces is formed. With a help of tensiometric table the values of components of cutting forces during free and fixed cutting of high pressure hoses were defined and their comparison was performed. As a result of the use of this technology the edges of the cut off high pressure hoses meet the necessary requirements without using of complicated technological processes.

10

Authors: Sergii Maksimov, Oleg Oleinik, Anatoliy Gavrilyuk

Investigations on the development of a basic technology of the shielded-gas mechanized arc welding of strengthening structural elements which are used in repair of main gas pipelines were carried out. It is shown that the advanced welding wires Sv08G2S, Е71Т-1, DW-50, DW-A55 are in compliance with the requirements for providing the necessary level of mechanical characteristics, impact toughness of weld metal, content of diffusive hydrogen in the deposited metal and can be recommended for application in the further testing of technology for repair of the operating pipelines under the field conditions. The carried out works resulted in the working out of documentation on the technology of mechanized arc welding in shielding gases in repair of main gas pipelines of Ukraine.

10

Authors: Andrii Dzyubyk, Liudmyla Dzyubyk, Yaroslav Zinko, Stanislav Biruk

The design of banding shells of rotary units is analyzed. It is shown that combined welding and cast manufacturing of bandings is used in the case of large structural sizes. The basic materials (30, 35, 25 HSL and 30 HML), being used in this process, are characterized by the tendency of forming of hardening structures due to the thermal cycle of welding. As a result of this, the cracks in the heat-effected zone, which lead to the destruction of the connection under the influence of welding residual stresses. The analysis of literature sources has shown that the usage of electroslag welding is perspective during the manufacturing and welding of operational cracks. Thus it is important to define the correct parameters of the welding conditions. In the case of electroslag method they are different from the arc methods and are characterized by the larger amount. In the paper the technological process of welding of banding (tread) ring with the external diameter of 4600 mm, wall thickness of 300 mm and wideness of 500 mm, which is made of steel 35. The defining of regime parameters is made using the following recommended techniques: taking into account the chemical composition of the basic metal; according to the nomogram depending on the ratio of the thickness of the metal to the number of electrode wires; using the calculation (design) method according to the conditions of electroslag welding of the banding. Taking into account the tendency of the steel 35 to cracks forming (cracking), the evaluation of the structure and phase composition and mechanical properties of metal of heat-effected zone of the weld. In order to define the microstructure, the cooling rate of the metal in the range of structural transformations was determined and the diagram of anisothermal decomposition of austenite was used. The technique of determination of the metal cooling rate as a result of the influence of thermal cycle of electroslag welding is proposed in the paper. It is based on the usage of special nomograms which characterize the specific features of the process being studied. The cooling rate equals w= 0.1876 degrees per second when using the developed process parameters. Also the investigation of temperature distribution in the cross-section of the weld has been carried out. It is shown that there are no significant deviations of temperature when using the proposed regime parameters. This influences the reduction of the level of residual stresses along the thickness of the weld. The analysis of the diagram of austenite transformation has shown that the structure of the steel 35 in the initial state is ferrite one with the mixture of pearlite and bainite. As a result of welding carrying out the structure will have a similar composition with slightly larger content of perlite and bainite. It was defined that their content in the heat-effected zone is as follows: 39 % for ferrite, 61 % for the mixture of perlite and bainite. At the same time, the investigated technology of electroslag process ensures the slow heating and cooling of the areas around the weld and obtaining of satisfactory mechanical properties of the metal. Therefore, the combined usage of existent techniques of regime parameters determination is expedient. Also it is necessary to carry out the verification of physical and chemical properties of the metal of heat-effected zone in order to prevent the formation of hardening structures.

10

Authors: Petro Koruniak, Vladyslav Shenbor, Vitaliy Korendiy, Anatoliy Bezpalov, Volodymyr Brusentsov

The operation of hopper devices, which are used in industry, civil engineering, agriculture and transport, is analyzed on the article. The external factors, which influence the process of charging, storing and discharging of loose cargo (freights) from hopper tanks, are overviewed. The subject of research of presented paper is the improvement of mechanisms of fracturing of products hangs-up (bridges) in hoppers at the stage of designing and setting up of hopper devices. In order to solve the stated problem the schemes of bridges fracturing and the structures of devices for debarment of products bridging and their uniform outflow from the hopper tank are proposed. The proposed schemes are based on the principles used in development of vibratory machinery with mechanical, cam and electromagnetic vibratory principles of structures forming. For cam spring device of bridges fracturing the technique of calculation of stiffness of elastic system and of the necessary forces for performing of technological process of bridges fracturing is presented and the recommendations for choosing of the stiffness of the system of elastic elements are suggested. For the hoppers with spring and electromagnetic blocks of bridges fracturing and of metered (batched) feeding of products the structural diagrams of devices are presented and the recommendations for usage of various modifications of devices are suggested. The influence of parameters of flat spring elements on the efficiency of devices operation is overviewed. The structural diagrams of devices with one-cycle and two-cycle electromagnetic vibration exciters and the modifications of elastic systems are considered. the structural diagram of the production prototype of the hopper feeder is presented. The materials of the article, the proposed structural diagrams, the operation scheme of the hopper feeder and the derived analytical formulas may be used by designers, researchers and technologists while improving of existent and developing of new devices.

22

Authors: Bohdan Diveyev

This study aims to predict the sound transmission properties of composite layered plates structures in the lower frequency range. In present paper a novel procedure to derive the sound isolation parameters for layered plates is under discussion. This paper presents a new stress analysis method for the accurate determination of the detailed stress distributions in laminated plates subjected to cylindrical bending. Some approximate methods for the stress state predictions for laminated plates are presented here. The theoretical model described here incorporates deformations of each sheet of the lamina, which account for the effects of transverse shear deformation, transverse normal strain-stress and nonlinear variation of displacements with respect to the thickness coordinate. The main advantage of the present method is that it does not rely on strong assumptions about the model of the plate. Comparison with the Timoshenko beam theory is systematically made for analytical and approximation variants. The geometrical and mechanical parameters dependent frequency response functions and damping are presented for an arbitrary layered beam. The effective stiffness constants of equivalent to lamina Timoshenko beam (TB) and their damping properties have been determined by using a procedure based on multi-level numerical schemes and eigenfrequencies comparison. Numerical evaluations obtained for the vibration of the equivalent TB have been used to determine the sound transmission properties of laminated composite beams with the system of dynamic vibration absorbers (DVA’s). The optimization of beams – DVA’s system sound absorption properties is performed in the low frequency range. The results have shown that the presence of a DVA causes a decrease in the sound transmission in the low-frequency range. The extension of the present approach to various layered plates with various DVA’s systems will be performed in order to obtain optimal sound insulation.

10

Authors: Andriy Kozak

Automatic dosing system for loose materials is widely used in construction, food and pharmaceutical industries to prepare various mixtures. The main criterion for optimization of such systems is the accuracy of dosing of each component of the mixture, which depends on the speed component dosing and other process factors. Technological requirements for product quality in production and the high cost of individual components of the mixture strictly regulate the developers of the automated system loose materials size dosing errors. Ensuring compliance with the maximumpossible mix recipe requires dosing of each component with high accuracy, which is a daunting task for engineers. Precision dispensing in automated systems is a function of the large number of systematic and random factors: size, shape and relative position of individual particles of the material; coupling coefficient of each other and of the structural elements of the dispenser; relative humidity of material dosage and indoor air; the height of the fall of the material in the receiving container; the value of the dispenser tilt to a level of horizon; electromechanical vibration and noise, etc. Developed simulation model of frequency-controlled electric screw feeder that is different from the known one facts that modeling of screw feeder is considering mass “falling pillar” which is constantly changing as the accumulation of material in the hopper.

10

Authors: Alexander Оrgiyan, Anna Balanyuk, Vladimir Kobelev, Ivan Tvorischuk

On the basis of precision theory we propose the method of computation of static and dynamic errors of cross-sectional shapes of holes in fine boring of smooth and stepped holes. We consider particular cross-sectional shape errors caused by such factors: – Error of the tooled hole form caused by the axis hope displacement in the workpiece relative to the spindle axis; – Error of the tooled hole form caused by the hole out-of-roundness in the workpiece; – Error of the tooled hole form caused by unevenness of the cutter radial compliance at the angle of spindle rotation. According to time characteristics the errors can be divided into static with frequency substantially less than the lowest natural frequency of the process system, and dynamic, caused by vibrations. Static error rate is usually a multiple of the spindle speed. The computations of deviations from the roundness of the cross section caused by vibrations are determined by computing the amplitudes of forced vibrations. Computations of individual static errors based on the average values of compliance, the material being processed and the processing mode are reduced to construction of nomographs for various materials. Dynamic errors are determined by computation of forced vibrations amplitudes on the basis of systems of ordinary differential equations describing the vibrations of a machine closed dynamic system. These equations allow to compute the amplitude of the forced vibrations of smooth and stepped boring bars. A distinctive feature of the computations for multiple tooling is allowance for mutual influence of excitations arising at each step of a boring bar. It is assumed that at multiple tooling each of the working cutters creates its own errors, the values of which are found by the nomograms for single-cutter tooling. Full tooling error at each step caused by some source of error is determined as the sum of the errors: of both, own and additional, caused by all working cutters. Additional errors can be found through coefficients of influence through dividing by the respective cutter's own compliance and through multiplying by the appropriate factor of influence. We obtained results of computations and experiments of the dependence of the total error on the ratio of the boring bar steps lengths. Analysis of roundness charts of the bored holes shows that vibrations can be a factor largely determining the shape of the cross section of the hole. Experiments have shown that when the rotation speed changed the excitations of the spindle poles changed too. Under unfavorable excitation frequencies the tooling errors increase by 1,5–2 times. The study results allow us to compare the two most common ways to reduce the errors caused by elastic deformations: the use of the dynamic damper and the processing of holes in two runs. The experimental results confirm the non-monotonic dependence of the amplitudes of forced vibrations on the ratio of the boring bar steps lengths.

20

Authors: Yuri Chovnyuk, Yuri Gumeniuk, Mykhailo Dikterjuk

Most authors have ignored the effect of rotatory inertia and shear deformation. This practice is justified for slender flexible arms. According to the Timoshenko beam theory, the deflection due to shear force and rotatory inertia should be taken into account in modelling for high speed and high precision requirement when the ratio of the cross-sectional dimensions to length increases. Based on Hamilton’s principle and Timoshenko’s flexible beam theory, the dynamic model of a single non-slender flexible link is derived, and it is shown that the elastic motion is governed by a pair of coupled partial differential equations with coupled boundary conditions. Then the abstract form of the dynamic equations is studied, and the properties of the spectrum of the elastic operator appearing in the evolution equation are given. Furthermore, the eigenvalue problem of the elastic operator is solved in explicit form. The formulation and well-posedness of the state-space equation, as well as the transfer function of the dynamic control system of the non-slender flexible link, are studied by spectral analysis. Spectral analysis is used to study the well-posedness of the dynamic control system. The tracking control problem is studied and a feedback control scheme that controls the rigid-body motion and elastic behaviors simultaneously is derived based on a n-modal model. Closed-loop configuration of a control system, equivalent circuit of a dc-motor and the overall system block diagram are proposed. The stabilization of the closed-loop system is studied analytically. Finally, the tracking control problem is studied, a stabilizing feedback control law based on a n-modal model to suppress vibrations of the flexible link is derived, and the necessary and sufficient conditions that can guarantee the stability of the closed-loop system, are given. Simulation results are given as well.