ON THE ISSUE OF DETERMINING THE CRITICAL CUTTING SPEED OF THE MECHANISM FOR FORMING AND TRIMMING THE FALSE EDGE OF THE DORNIER RAPIER LOOM

In this paper, an attempt is made to develop a method for determining the critical cutting speed of the threads of the false edge of the edge-forming mechanism of the weaving rapier machine. The proposed calculation method takes into account the impact nature of the cutting process at a critical speed, which allows taking into account the mutual influence of the parameters of the working process and more fully assess the mechanics of this process, in which the intensity of the cutting force and the value of the contact stress take the maximum value. The paper calculates the critical cutting speed for some of the main types of threads used and the parameters of the knife blade. The presented calculation results can be used to select rational design parameters of the knife blade, depending on the type of processed threads, when designing and researching new edge-forming mechanisms on looms.

Ballistic design of a launch vehicle with a reusable payload fairing

The paper focuses on the problem of the ballistic design of a two-stage launch vehicle for the case when the payload fairing is returned by using its flaps as the lifting surfaces of the first-stage reusable boosters. The fairing flaps must be opened after the velocity pressure reaches its maximum value. Therefore, the trajectory in the operation section of the first-stage boosters is assumed to be vertical. The flight along the curved part of the trajectory is carried out by the second-stage booster. In this study, we introduced an algorithm for selecting design parameters, developed an original program in the Wolfram Mathematica computer algebra system, and found the rational design parameters of the launch vehicle.

Design of impact dampers for transporting cargoes by two-link vehicles

This paper considers the influence of the transitional modes of movement (acceleration, braking) of a multi-link vehicle on the vibration protection of transported non-fixed or partially fixed cargoes. The impact phenomenon, in this case, can be strengthened by the existence of coupling mechanisms between the links of a multi-link vehicle. To reduce such horizontal impact loads, it is advisable to use elements with viscoelastic damping in the coupling devices of a multi-link vehicle. To study the actual impact phenomena during the transportation of non-fixed or partially fixed cargoes under the extreme modes of movement of two-link vehicles, it is proposed to use a flat two- and three-mass dynamic model with viscoelastic damping. At the same time, the theory of elastic impact has been applied while the elastic-damping characteristics of vehicles' suspensions were not taken into consideration. It has been shown that the reported research results make it possible to estimate the approximate values of the mechanical parameters for restrictive devices that protect non-fixed or partially fixed cargoes from impact, during the transition modes of transportation, depending on the conditions of motion. This practically makes it possible to select the rational design parameters for the elements of viscoelastic restrictive devices, in particular elastic elements and dampers, in order to reduce impact loads on non-fixed heavy cargoes during transportation under extreme modes of movement. Based on this study, a procedure of vibration protection of non-fixed or partially fixed cargoes in the body of a two-link vehicle during its uneven movement has been proposed, which implies determining the maximum dynamic loads on these cargoes as well as the possibility of choosing the rational design parameters for restrictive devices in order to prevent or reduce the impact of these cargoes hitting the restrictive devices

APPLICATION OF KINEMATIC STABILITY ANALYSIS IN DETERMINING RATIONAL DESIGN PARAMETERS OF CAREER STEPS

The main factor that determines the stability of the pit benches in rocky and semi-rocky rocks is geological and structural since potential collapse prisms of a particular configuration are formed by differently oriented ruptured faults (cracks) with certain spatial relationships between themselves and the pit surface. Evaluation of possible planar, wedge-shaped, and overturning collapses of individual benches is carried out by analyzing the parameters of structural disturbances identified within the rock mass of the studied section of the open pit relative to the orientation of open pit edges. The article presents the results of the analysis of the kinematic stability of the optimal parameters of the benches on the example of the Kurzhunkul open pit, which ensures their stability on the limiting contour. A sequence of actions is proposed for determining the stability parameters of rock benches in a quarry. Performing a kinematic analysis based on the identified systems of cracks allows us to determine the probable failure patterns of the slopes of the benches and select the calculation schemes for their stability to substantiate their optimal parameters and make decisions on their stabilization. Geological and structural zoning of the quarry space according to this method allows analyzing the holding capacity of safety berms to control detected collapses, to highlight benches that need to be brought into a safe state with the determination of their stable parameters, and to recommend options for optimizing the design profile.

Multi-section coupling device for aggregation of modern seeding machines

Choosing rational design parameters of the coupling device for multi-section aggregation of seeders, it is possible to ensure full loading of the power unit while maintaining quality indicators of the technological process at a sufficiently high level. Foreign aggregates are not suitable for use in the Russian Federation due to the different soil and climatic conditions. Purpose of the study: to develop an effective device for multi-section aggregation suitable for domestic modern seeding machines. Subject of the research: the relationship of design parameters and modes of operation of the device for multi-section aggregation of seeders with indicators of the technological process of sowing. A monographic survey of known structures has been carried out, a device for multi-section aggregation of seeding machines has been substantiated by the design and construction method, indicators of the technological process of sowing have been experimentally obtained. The developed coupling device for multi-section aggregation consists of a central frame resting on the wheels and articulated side sections: left and right, which fold when transporting the seeding unit. The total working width of the seeding unit is up to 12.5 meters. According to the research results, the quality of the technological process by the seeding devices meets the regulatory requirements. The instability of the total seeding (0.6–1.1 % for barley and 0.4–0.7 % for wheat) is within the tolerance (up to 3 percent); uneven seeding between devices 3.9–4.2 percent (barley) and 2.6–4.2 percent (wheat) corresponds to the norm (up to 5 percent). The number of seeds embedded at a predetermined depth of the soil corresponds to the required (not less than 80 percent) and was 81.8–83.9 percent for barley and 80.1–83.3 percent for wheat. Not embedded seeds were found in the soil.

MOVEMENT STABILITY OF A SECTION OF THE MACHINE FOR BLACK FALLOW CULTIVATION IN A LONGITUDINAL-VERTICAL PLANE

One of the tasks of using the black fallow in agricultural production is the weed control and the moisture conservation in the soil. Application of the most advanced soil cultivation technologies ensures preservation of no more than 75% of precipitations in the soil. To improve the state of this issue, we have developed a special machine for processing the black fallow. A mathematical model has been developed that describes the dynamics of the movement of the harrow section in a longitudinal-vertical plane, and its solution is given, which allows investigation of the impact of this or that design parameter upon the dynamics of the angle of rotation in time. The adequacy of the developed mathematical model is confirmed by special laboratory and field investigations of the created experimental machine. With rational design parameters the rotation angle of the harrow section in a longitudinal-vertical plane will not exceed – 3º, and the time of its exit to the equilibrium position will not exceed 16...17 s.

Shaping the appearance of a long-range aircraft at the stage of developing a technical proposal

Objective. The process of designing a long-range aircraft, in particular at the preliminary design stage, involves comparing and analyzing a large number of design alternatives with specified performance criteria. At the same time, the problem of choosing the composition of rational design parameters is solved, which is an actual problem of the preliminary design stage of a long-range aircraft. Methods. The developed method allows determining the vector of parameters that provides rational characteristics for a given efficiency criterion. In this regard, the authors propose to introduce a global efficiency criterion - the takeoff weight of the long-range aircraft, and the specific criteria are the aerodynamic quality in cruise and the value of fuel efficiency. Results. In this formulation of the design problem, it is necessary to solve several interrelated problems, some of which are formalized, while others do not yet have a mathematical construct and software that allows automating the process. A distinctive feature of the proposed approach to finding a rational design solution is the use of statistical analysis methods in combination with methods of high-precision mathematical modeling, software-implemented in a single information environment using the Fortran V and C++ languages. Conclusion. The proposed method for selecting the composition of rational design parameters allows forming the appearance and providing the specified characteristics for its component elements at the early stages and stages of designing the long-range aircraft.

A Parametric Analysis of Self-Acting Valves of Reciprocating Compressors Using Mathematical Modeling Methods

One of the important tasks in the design and operation of reciprocating compressors is to ensure energy-efficient and reliable operation of self-acting valves. The requirements of efficiency and reliability are largely competing, the simultaneous satisfaction of which is not always possible. This paper presents a calculation analysis of various factors effecting the operation of self-acting valves in order to select their rational design parameters. The results of the analysis for the valve’s changing parameters (spring stiffness and maximum valve stroke) and the crankshaft rotational speed are presented. The results obtained do not contradict the data previously described in the literature by other authors, namely, that a reduction in the spring stiffness leads to a reduction in the work expended on pushing the gas through the valve and to a delay in closing the valve, therefore resulting in the backflow of gas through the valve. Reducing the crankshaft rotational speed causes flutter, which affects both the parameters of the valve itself and the efficiency of the compressor as a whole.

TO THE DEVELOPMENT OF SOIL TILLAGE WORKING UNITS ON THE BASIS OF FIELDS SOLIDGRAMS

When solving engineering problems in soil cultivation, soil resistivity is applied. The use of solidograms is more preferable in the construction of soil-working tools and the operation of agricultural machinery. The developed technologies and instruments for continuous layerwise determination of the longitudinal hardness of the arable layer make it possible to obtain soil maps by hardness, to create a database. Factors affecting hardness variability include crop cultivation technology, row spacing, parameters, number and gauge of movers of mobile power tools and agricultural tools, the width of the technological track. The influence of the degrees of freedom of the working units on the intensity of loosening of the soil, the magnitude and nature of the change in the traction resistance, both as a separate working unit and the entire implement, is considered. A combined working unit consisting of a cutaway knife, a built-in drainer, a spring bender on a spring-loaded draft, which creates conditions for the realization of low-intensity types of deformation, the Baushinger effect is proposed. The advantage of the working unit is the continuous automatic adaptation of geometric parameters. For design and strength calculation of such working units, synthesis of elastic characteristics, it is recommended to use methods of the theory of random oscillations. The force and kinematic perturbation of the oscillations is caused by the variability of the hardness of the arable layer, the speed of movement of the working organ, the vibrorheological properties of the soil, and the parameters of the elastic characteristics of the system of springs. The rationale for the smoothing capability of the dynamical system being designed is substantiated by justifying rational design parameters, selecting the material, determining the system parameters by known characteristics at the input and output.