Author: Burak AKYOL, Mustafa GÜDEN, Alper TAŞDEMİRCİ, Subhan NAMAZOV
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Abstract: The strain rate dependent compressive strength of an autoclaved aerated concrete (AAC) having a density of 600 kg m-3 was experimentally investigated between quasistatic and high strain rates (2x10-3-~4150 s-1) through quasi-static and dynamic compression, confined compression and indentation tests. High strain rate equilibrium and direct impact non-equilibrium compression tests in conjunction with the high strain rate confined compression and indentation tests were conducted in a compression Split Hopkinson Pressure Bar. The experimental results showed two different regions of the compressive strength-dependency on the strain rate: a low-strain rate-dependent region from quasi-static to ~18 s-1 and a high-strain rate-dependent region from ~18 s-1 to ~1000 s-1. The switch of the failure mode from the single axial cracking at quasi-static strain rates to the extensive axial and circumferential cracking at increasing strain rates was ascribed to both the axial and radial inertia. The dynamic increased factor (DIF=dynamic strength/static strength) showed an abrupt increase after ~18 s-1 as similar with the compressive strength. The mean confined and indentation strength values also increased as the velocity increased, while the mean confined compression strength values were shown to be comparable with the dynamic compressive strength values. The inertia and strain rate contributions to the enhancement of DIF until about 1000 s-1 were predicted by taking the quasi-static indentation strength as the full confinement strength.
Keywords: Autoclaved aerated concrete; Split Hopkinson Pressure Bar; direct impact; compressive strength; indentation; confinement; inertia
Author: Nizami YUSUBOV, Heyran ABBASOVA
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Abstract: Based on the developed models, the article reveals the degree of influence on the machining accuracy of a complex of technological factors, including the structure of a multi-tool single-carriage adjustment, the deformation properties of the subsystems of the technological system, cutting conditions. A number of ways to control multi-tool single-carriage machining based on the developed accuracy models are shown, including improvements in the structure of multi-tool single-carriage adjustment, calculations of limiting cutting conditions. The developed control models make it possible to predict the accuracy of machining for given conditions, including such technological components as the adjustment structure, properties of the technological system, machining conditions, thereby creating a methodological base for CAD for multi-tool single-carriage machining. They can serve as a basis for developing a digital twin model of the process.
Keywords: control model, multi-tool machining, multi-tool single-carriage adjustment, machining productivity, predetermined dimensional accuracy, scattering fields, matrix model of accuracy.
Author: Subhan NAMAZOV, Taleh TAGHIYEV, Shahin MASHAYEV
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Abstract: During operation, static and dynamic loads, as well as various types of friction and wear, can simultaneously act on parts of machines and mechanisms. In these cases, as a rule, the problem of ensuring the wear resistance of parts is secondary, since, first of all, it is necessary to give structural elements strength, to exclude destruction and crushing. However, for a more significant increase in the service life of parts, it is necessary to apply comprehensive measures that allow solving these problems together. The mechanism of impact-abrasive wear of materials is primarily determined by their chemical composition and structure. A study of the nature of wear of hardened iron-carbon rolled steels shows that with a change in carbon concentration, the mechanism of impact-abrasive wear also changes. With an increase in the carbon content, the hardness of the metal increases, the depth of the holes from the introduction of the abrasive gradually decreases, however, the wear changes according to a more complex relationship: it decreases with an increase in the carbon concentration to 0.7 + 0.8%, and with a higher content, it increases.
Keywords: structure, carbon, shock-abrasive, composition, material, sintering, wear resistance.
Author: Viktor GUZEEV, Igor DERYABIN, Dmitrii ARDASHEV
Email: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org
Abstract: The paper considers a variant of the predictive determination of the cutting force components for non-free cutting when turning. It is established that both the process of plastic deformation and the process of friction on back surfaces adjacent to main and auxiliary cutting edges of the tool influence the magnitude and direction of a cutting force component. The resulting force is defined as the vector sum of the forces that occur on the main and auxiliary cutting edges. We propose to determine the cutting force direction in non-free cutting as a vector in the direction of chip flow relative to the main cutting edge. The cutting process photography fixes the inclination angle of the chip flow. It is confirmed that in free cutting, the direction of chip flow is perpendicular to the main cutting edge. Contour turning on CNC lathes is accompanied by a change in the direction of feed motion resulting in a change in the main and auxiliary kinematic angles of the cutting tool. An increase in the active length of the main cutting edge in this situation leads to an increase in the contact area of the back surface of the main cutting edge with the workpiece surface, and, consequently, to an increase in the friction component of force, acting on the main cutting edge. Experimental measurement of the cutting force components makes it possible to determine the degree of influence of the force components associated with both the process of plastic deformation of the work material and the process of friction on the back surfaces adjacent to the main and auxiliary cutting edges of the tool. The obtained analytical dependences express the functional relationship between the elements of the cutting modes, the geometric parameters of the cutters, the degree of wear, the shape of the workpiece surface, and physical and mechanical properties of the work material. A large set of parameters included in the formulas for determining the components of the cutting force allows adequate monitoring the nature of the force interaction of the elements in the technological system when processing parts.
Keywords: cutting forces, contour turning, unstable force load on technological system.
Author: Victor ARTEMYEV, Sergey MOKRUSHIN, Sergey SAVOSTIN, Artem MEDVEDEV, Vitaly PANKOV
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Abstract: This article is devoted to the processing of time signals in a discrete time domain. Time signals are the main object of analysis in many areas, such as signal processing, communication, control and much more. Today, for efficient signal processing, it is necessary to use methods adapted to the discrete time domain, using the Z-transform method to solve difference equations in the discrete time domain. The Z-transform method is a powerful and most effective tool for analyzing and solving difference equations, widely used in control systems, signal processing and other fields. The main steps of applying the Z-transformation method are also presented, starting from the formulation of the difference equation to obtaining a solution in the original time domain. Special attention is paid to the Z-transformation process, where the difference equation turns into an algebraic equation with respect to the Z operator. The basic properties of the Z-transformation and the operations with them necessary for the successful application of the method are described.
Keywords: temporary domain, discrete form, transformations, geometric progression, difference equation.
Author: Nizami YUSUBOV, Heyran ABBASOVA, Ramil DADASHOV
Email: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org
Abstract: In the article for practical application within the framework of creating a matrix theory of accuracy of multi-tool machining for a range of multi-tool adjustments (tool setups) of previously developed models of machining error, the necessity of dependence of the coordinate components of cutting forces on technological factors is shown. (parameters of cutting conditions, strength properties of the material being machined, deformation properties of the technological system, etc.). For this purpose, the tasks of cutting force models are established, a systematics of machining schemes used on modern lathes is carried out, highlighting two schemes for the formation of a machined surface (trajectory and profile), and the principles for developing cutting force models are given. Thus, the development of an algorithmic unified complex of mathematical models of cutting forces is substantiated, taking into account the introduced systematics of machining schemes according to the mechanism of formation of the machined surface.
Keywords: Multi-tool machining, Multi-tool adjustment, Systematics of machining schemes, empirical and analytical models, cutting force models, mathematical models of cutting forces.
Author: Ahmad IMANOV
Abstract: In order to take into account more boundary conditions, a new modified equation was obtained to establish the profile of the fist by adding a constant to the equation obtained from the solution of the differential equation of curvature (i.e., - convex profile surface as a special case). Based on this equation, the expression defining the movement of the pusher based on the rotation angle of the fist was deduced. The kinematic report of the punching mechanism was performed on the basis of a modified formula. During the kinematic calculations, it was found that there are no jumps in the displacement, velocity and acceleration diagrams of the pusher, that is, the mechanism works smoothly. In order to verify that the curvature takes a negative value along the profile, the equation of the curvature was deduced, its graph was plotted and its accuracy was confirmed.
Keywords: profile, punch, flat pusher, speed, momentum, punch mechanism, impact, radius of curvature.
Author: Victor Artemyev, Artem Medvedev, Victor Yaroshevich
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Abstract: The article presents a study of systems of difference equations, their role and application in modeling and analysis of dynamical systems in various fields. The purpose of the work is to analyze and develop methods for solving difference equations with a special emphasis on their application in automation and mechanics. Difference equations are mathematical models describing the evolution of variables in a discrete time space. Their study allows for a deeper understanding of complex dynamic processes and effective modeling of systems of diverse nature. The paper presents an overview of various methods of analysis and solution of difference equations. Numerical integration methods, approximation methods and stabilization methods of systems of difference equations are considered. Special attention is paid to the properties of stability, convergence and controllability of such systems. The results of the study contribute to a deep understanding of the dynamics of systems of difference equations and the development of effective numerical methods for their solution. The solution of difference equations is widely used in automatic control, robotics, aviation, mechatronics and other industries. It plays an important role in modeling and controlling various systems, including electromechanical systems, robots, autopilots, automation processes, and others.
Keywords: numerical integration methods, approximation methods, and stabilization methods for systems of difference equations
Author: Allahverdi ALAKBAROV
Abstract: Serial manipulators are a serial of links connected by joints. The manipulator is called serial, because the drives of this manipulator are arranged in series, one after the other. Most often, the drives of the sequential manipulator are located on jointes or are coordinated with the joint. All links, the base, as well as the executive link, make up the kinematic chain of the manipulator. Serial manipulators have a large working area, it is much larger than the working area of parallel manipulators, which allows them to work with large parts, which undoubtedly increases the area in which the manipulator is capable of working. Mass-produced robots typically have six joints because at least six degrees of freedom are required to place a controlled object in an arbitrary position and orientation in the robot's workspace. The inverse kinematics of sequential manipulators with six rotary joints and with three consecutive intersecting joints can be solved in closed form, i.e. analytically This result had a huge impact on the design of industrial robots. This section provides a unified work for the calculation of the mobility and constraints in a general over constraint spherical manipulators based on spherical serial manipulator plus the different spherical structural groups with two, three and four classes. The results of the section can be considered by knowledges of structural groups with general constraint three constructed to the serial spherical manipulator with 3DoF. The 3DoF serial spherical manipulators represent as a series of 1DoF revolute joints with the axises intersecting in the center of sphere. Three illustrative examples showcasing the method are presented.
Keywords: Serial spherical manipulator, end effector, spherical structural groups, structural synthesis, mobility analysis
Author: Husnu KARIMOV
Abstract: During the cleaning process of the raw cotton, in the saw drum and grate network zone of the cotton ginning machines, the cotton mass is being subjected to the mechanical impact. At this moment, when the cotton wicks hit the grates, the cotton seed is mechanically being damaged and free fibers are being formed. When the cotton seed is mechanically damaged, its maturity decreases, and the formation of free fibers reduces the curvature/spinning ability of the fiber. Keeping the natural quality indicators of raw cotton and taking into account its physical and mechanical features, there is a great demand to conduct theoretical studies and researches for designing new machines. Taking into consideration the elastic properties of cotton wicks during their impact on the grate, the formulas revealing the movement speed of wicks and recovery of wicks coefficient were determined. The article reveals the possibility of prevention the cotton elements from damage by determining the interaction characteristics of cotton wicks with grates and by adjusting the technological parameters to the equipment before processing.
Keywords: cotton wick, extraneous impurities, grate, deformation, impact force
Author: Ilham HUSEYNOV
Abstract: In the article, traction transmissions of railway vehicles, which are an important component of the transport industry, are studied. Dynamic events in the functional chain, as the main factors that ensure the structural condition of the main parts of the mechanical system, the longevity of the system, effective measures to improve the operation of the service, effective measures to improve the performance of the structures, the operation of improved structures, the in-depth determination of maintenance and repair technologies, as well as the service outstanding features. The relevance of technical quality assessment is justified by the development of an innovative model. The condition, construction and operation of modern traction drives are explained. Experimental studies are underway and have strong implications for transmission control. With the device that checks the possibilities of using defectoscopic methods, the cases that caused rejections were determined.
Keywords: Railway, train, locomotive, wagon, innovative, transmission, reducer, dynamics, model, gear