Investigation of the hydrodynamic impact of a planing small vessel on a water body

Рассмотрен экологический аспект использования маломерных глиссирующих судов. В статье представлен способ оценки характеристик потока, возмущённого движением глиссирующего судна. Способ основан на использовании численного метода гидродинамики. Выбраны параметры и зоны исследования потока вокруг корпуса рассмотренного судна, и разработана последовательность действий их определения. Проанализированы качественные картины изменения потока с ростом скорости глиссирующего судна с заданной геометрией, и выделены составляющие наиболее значимые составляющие. Оценены количественные характеристики возмущённого потока: вызванные скорости, расстояние от транца до точки зарождения системы волн, волновые характеристики. Оценка гидродинамического воздействия на водоём была проведена для двух притоков Волги – р.Керженец и р.Сура. Выполнено определение придонных касательных напряжений в выбранных водных объектах в их естественном и возмущённом присутствием судна состоянии. Проведено сравнение рассчитанных касательных напряжений с пороговыми значениями, что позволило оценить влияние движения маломерного судна на донный грунт. The ecological aspect of the use of small-sized planing vessels is considered. The article presents a method for assessing the characteristics of a flow disturbed by the movement of a planing vessel. The method is based on the use of the numerical method of hydrodynamics. The parameters and zones of the flow study around the hull of the vessel under consideration are selected, and a sequence of actions for their determination is developed. Qualitative patterns of flow changes with an increase in the speed of a planing vessel with a given geometry are analyzed, and the most significant components are identified. Quantitative characteristics of the perturbed flow are estimated: induced velocities, distance from the transom to the point of origin of the wave system, wave characteristics. The assessment of the hydrodynamic impact on the reservoir was carried out for two tributaries of the Volga - the Kerzhenets River and the Sura River. The determination of bottom tangential stresses in selected water bodies in their natural and disturbed state by the presence of the vessel was performed. The calculated tangential stresses were compared with threshold values, which made it possible to assess the impact of the movement of a small vessel on the bottom soil.

Research of Technology For Production Deformed Semi-Finished Products From Chip Waste of Aluminum Alloys And Study Properties of The Obtained Products

The results of studies of some methods of obtaining longish deformed semi-finished products in the form of rods and wires from chips of aluminum alloys 6063 and AlSi12 excluding the melting process during their implementation are presented. At the same time, the main methods used powder metallurgy (briquetting), metal forming (extrusion and drawing), and heat treatment (annealing). Using the developed general technological scheme of thermal deformation processing of chip waste from aluminum alloys, experimental studies of the technology of production of longish deformed semi-finished products from high-quality chips of alloys 6063 and AlSi12 have been carried out. The mechanical properties of metal obtained from shavings of experimental alloys of briquettes, rods, and wires were determined. The change in the structure of semi-finished products at all technological stages of processing was investigated. Computer simulation has been carried out, according to the results of which the regularities of temperature change, degree of deformation, and relative density in the volume of the deformation zone for semi-finished products obtained by the method of combined rolling-extrusion of a porous billet from briquette chips of 6063 alloy. As well as the degree of deformation, average normal and tangential stresses in the zone have been established. Deformation depends on the conditions of contact friction when drawing a wire from this alloy. Using the results of computer simulation, the proposed routes for drawing wire from extruded rods of chips of 6063 and AlSi12 alloys were experimentally tested and with their help, experimental batches of products were obtained for various industrial purposes.

To Solution of Contact Problem for Elastic Half-Strip

Contact problems for elastic stripes have been well studied and published in domestic scientific literature. This is partly due to the fact that normative documents on the foundation structure it is recommended to use this elastic foundation model for simulation of a “structure – foundation – soil foundation” system. Two variants of boundary conditions at the contact between a half-strip and a rigid non-deformable base are usually considered. The first boundary condition nullifies the vertical displacements and tangential stresses, the second one nullifies vertical and horizontal displacements. Contact problems for an elastic half-strip are much less investigated. The paper considers this contact problem when the first boundary condition for zeroing of vertical displacements and tangential stresses at the contact of a half-strip with a rigid, nondeformable base. When performing calculations in the traditional formulation without taking into account tangential stresses in the contact zone, the Zhemochkin method has been used, which reduces the solution of the contact problem of solid mechanics to the solution of a statically indeterminate problem by the mixed method of structural mechanics. Therefore, at first, we have found the displacements of the upper edge of the half-strip from the unit load uniformly distributed over the edge section. The resulting expression is used to compose a system of equations for the Zhemochkin method. The case of translational displacement of the die has been considered, and the graph of contact stress distribution under the die's sole has been given in the paper.

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.

Development of a technique for computer simulation of the stress state of the drive drum shell of a belt conveyor to optimize its design parameters

The paper considers the method of computer simulation of the stress-strain state of the drive drum shell in the NASTRAN integrated environment. Due to the complexity of determining stresses and deformations in the drum sections by the analytical method, it is proposed to solve this important problem using the numerical finite-element method. At the preliminary stage of computer modeling, a mechanical design scheme was developed, including a variable pressure that changes depending on the angle of rotation of the drum, the deterministic relations describing the variable force factors are based on the Euler ratio. It is also proposed to take into account the pressure from the variable friction force, which depends on the changing coefficient of adhesion of the belt to the drum. As a result of the computer calculation, the equivalent Mises stresses of 65 MPa were determined, the safety factor was 4.2 and the components of the tangential stresses were determined using the stress tensor marker, the shear stress reached the level τ=16 MPa for fabric tape and τ=3.14 MPa for rubber tape. According to the results of the calculation, the dependence of the tangential stresses on the angle of rotation of the drum was constructed. A diagram of the change in the component of tangential stresses along the forming shell of the drum was constructed. Analysis of stress-strain state allowed us to determine the factor of safety of the drum shell. Based on the analysis of equivalent stresses, it is proposed to further calculate the durability of the drum using the method of long-term fatigue. The computer calculation of shear stresses in the component allows choosing the rational parameters of the lining, based on such indicators as peel strength and break, as well as determining the angle 61° of the slab lining required to improve the reliability and traction ability of the pipeline

Cathodic protection of main pipelines from stress corrosion cracking

The paper analyzes the degradation process of the strength properties of ferritic-pearlitic pipe steels subjected to the influence of cathode hydrogen and the operating pressure in the pipeline. It is shown that the growth stress corrosion cracking deep into the pipe wall occurs along the Chernov-Lüders band, in the direction of the maximum tangential stresses acting at an angle of 30-60 degrees relative to the tensile stresses.

DYNAMICS OF IMPACT OF ABRASIVES ON GEARS ON TEETH

This article discusses the effect of abrasive between the leading and the driven gear teeth on the formation of a stress state. In this case, normal and tangential stresses are calculated under the action of normal and tangential forces Keywords: gears, abrasives, normal and tangential stresses, segmented shapes, fracture limit, wear depth.

The beginning of the movement of bottom sediments in an unsteady flow

This article discusses the problems of determining the friction parameter and non-eroding conditions in a wave flow are considered from the standpoint of an approach using a critical dynamic speed. In the first stage of research, the question of the formation of an unsteady turbulent boundary layer is substantiated. Because of the research, dependences were obtained for the most important value from the point of view of sediment transport - the friction parameter. Based on the data of these measurements, a plot of dependence was built, which differs from the previously obtained analytical relationships. For the convenience of practical use of the obtained empirical connection approximated. The second stage of research is the development of a method for calculating the critical tangential stresses corresponding to the beginning of the movement of bottom sediments. Based on the Shilds method, a curve similar to the Shilds curve for wave flow conditions was constructed, which was approximated for the convenience of practical use.

Experimental studies of profile joints of machine parts under cyclic loading conditions

The increasing demands on the quality of machines, in particular multipurpose CNC machines, determine the tasks aimed at improving the designs of their critical components. The aim of the work is to ensure the accuracy, contact rigidity and durability of torquetransmitting connections of spindle assemblies during reusable replacements of auxiliary tools based on the use of conical profile connections with an equiaxed contour. The paper presents the results of experimental studies of these compounds on models that are made of optically active materials, which allows us to visually study the processes of contact interaction of profile parts under cyclic loading conditions. The method of static photoelasticity in the study of flat profile joints with an equiaxed contour made it possible to establish based on the analysis of isochrome patterns, that the change in the values of maximum tangential stresses per revolution of the profile joint is subject to a pulsation cycle.