Study Of Stress-strain State Research Articles

Study of stress-strain state of thin-sheet billet during its deformation by new composite working tool

The results for solving of the finite element problem of thin-sheet billet deformation by composite and simple elastic working tool based on SKU-7L polyurethane are presented. Comparative analysis of the obtained results is performed. The technological improvement for obtaining process of the thin-sheet products— elements of flat heat exchangers, decorative panels and similar thin-sheet products is presented.

Біомеханічне моделювання та проблемні питання хірургічної корекції вродженої лійкоподібної деформації грудної клітки

Congenital funnel chest deformity (CFCD) is noted in 0.6–2.3% of the population and accounts for 90% of all congenital chest deformities. Nuss thoracoplasty is the most common method for treating CFCD, which is considered a minimally invasive technology and provides a quick cosmetic effect. Purpose is to search for models of CFCD and its surgical correction in order to create a technique that is as close to reality as possible, which will make it possible to optimally plan and rationally carry out the forthcoming operation. Analysis of literature sources showed that, on the one hand, the construction of simplified models of the chest allows quick research, but these simplifications do not allow for an objective assessment of the influence and interaction of various elements of the complex biomechanical system «sternum–rib–spine». On the other hand, complex models are more reliable, but hardly available for implementation due to their ultra-high manufacturability and cost. In addition, in studies of stress-strain state on models of the chest, the presence of the spinal column or the interaction of the ribs with the vertebrae has been insufficiently studied. When in the works on modeling road traffic injuries this is justified due to the support of the spine on the seat, then when modeling the correction of chest deformities, the lack of consideration of the mobility of the articular joints and the flexibility of the spinal column can lead to incorrect and false results. It is promising to create a technique for modeling CFCD and its surgical correction in conditions close to reality. This will make it possible to develop a rational modification of thoracoplasty based on the D. Nuss operation under the condition of one–stage full–fledged stable correction and minimal biomechanical loads in the «sternum-rib-spine» system. No conflicts of interest was declared by the authors. Key words: funnel chest deformity, thoracoplasty, biomechanics.

ТЕОРЕТИЧЕСКОЕ ОБОСНОВАНИЕ ПОВЫШЕНИЯ ЭФФЕКТИВНОСТИ АРМИРОВАНИЯ ИЗГИБАЕМЫХ ЯЧЕИСТОБЕТОННЫХ КОНСТРУКЦИЙ

Aerated concrete is actively used in energy efficient construction, mainly as a masonry material for vertical load-bearing structures. At the same time, the creation of a closed thermal contour of the building, which is the basis of modern energy saving requirements, is rational by the use of aerated concrete in load-bearing horizontal structures that require reinforcement. Traditionally bar reinforcement is ineffective in aerated concrete due to low specific adhesion at the contact of the reinforcement with concrete and significantly less than that of heavy concrete, the distribution capacity of concrete around a rod, which evenly transforms concrete stress to bar extension, the consequence of which is the significant bar understress while pulling it in concrete. The authors’ research in the field of rationalization of reinforcing elements that are effective in cellular concrete, aimed at increasing the contact surface of the reinforcing element with concrete while maintaining the original steel consumption, makes it possible to recommend tape reinforcement for use in reinforced aerated concrete structures. Punched steel tapes equal to the bar reinforcement of the cross-sectional area, but having developed lateral surface, provide an increase in the adhesion strength of the reinforcement and preventing its pulling. The article presents the results of a numerical study of stress-strain state in reinforced aerated concrete beam with rectangular section, reinforced with the proposed tape reinforcement in comparison with traditional bar reinforcement

ОБЕСПЕЧЕНИЕ ЭКСПЛУАТАЦИОННЫХ ХАРАКТЕРИСТИК ЖЕЛЕЗОБЕТОННЫХ ЭЛЕМЕНТОВ КАРКАСОВ ЗДАНИЙ, ПОДВЕРГШИХСЯ СЕЙСМИЧЕСКИМ ВОЗДЕЙСТВИЯМ

The objectives of the study were to improve the operational characteristics of buildings with a bearing reinforced concrete framework located in seismic areas of the Russian Federation. The article presents the results of analysis of previous studies of stress-strain state of the framework elements of a multi-storey building under seismic impacts. It has been established that despite a more optimal solution of load-bearing systems of buildings in the form of reinforced concrete frames in seismic areas as a result of periodic actions of background earthquakes, inevitable accumulation of temporary fatigue and damage to structures during operation there is a significant reduction of dynamic resistance of the building as a whole. It is noted, that throughout all term of life of an object except design seismic load, the crucial role is played also by physical wear which development leads to structural modifications of properties of materials and inevitable deformation of technical characteristics of bearing structures. It has been found, that the most dangerous failures associated with the reduction of strength of columns, assemblies, the mating of bearing elements and, as a result, the loss of their stability, leading to the progressive destruction of the building as a whole. Three groups of possible methods of strengthening and increasing seismic resistance of buildings and structures are considered.

Study of stress-strain state of cold-drawn hexagonal steel rods

The results of the stress-strain state during drawing of hexagonal steel rods are presented. The effect of the drawing die angle and the degree of reduction on the distribution of the stress-strain state parameters and the elastic aftereffect of the deformed metal is studied.

Study of Stress-Strain State of an Aircraft Body at Steering Loads

A design scheme is considered: a cylindrical shell, which is loaded concentrated through the frame. A classical mathematical model is used for the adopted calculation scheme. Based on the mathematical model, the initial problem is analytically solved and an effective algorithm for multiparameter solution of the corresponding boundary value is constructed. The results of a quantitative analysis of the stress-strain state for the aircraft body are presented.

Determination of some mining parameters of the long wall for the effective use of plough systems in the Western Donbas mines

Theoretical studies of stress strain state of rock under the extraction pillar working by mechanized complex with plough systems were conducted. As a result of studies the mining parameters of the wall face working are presented. The mining parameters include the width of coal shavings continuously removed before reaching the critical rock pressure in the face and duration of the technological pause between removal of coal shavings, that leads to “relaxation” of rock pressure in the bearing zone to a safe state for continued mining. The use of the values of these parameters during the extraction pillar working ensures efficient and no-failure operation of high-performance mechanized complexes equipped with plough systems as shown by the example of mining and geological conditions of one of the mines of the Western Donbas.

Study of stress-strain state during cross-wedge rolling with one tool

The peculiarity of cross-wedge rolling with one tool is the workpiece deformation with one tool and the fact that the workpiece is not supported with the tool from the opposite side. On both sides of the tool outside the contact with the workpiece, the workpiece is fixed with pairs of upper and lower tools, by means of which the axis of the workpiece is held in a constant position. Such conditions of rolling qualitatively change the deformation zone and, as a result, the stress-strain state.The change in the stress-strain state was qualitatively estimated by comparing the fields of slip lines in the traditional two-tools cross rolling and one-tool cross rolling. One-tool cross rolling increases the normal and average stress at the contact by 7.8–14.5 %, changes the average stress of the specimen from tensile to compressive one in the axial region. This circumstance significantly increases the resource of plasticity and allows rolling metals with limited plasticity without opening the axial cavity. Comparative studies of the stress-strain state from the traditional two-tools cross-wedge rolling and one-tool cross-wedge rolling in the axial region of the workpiece have been carried out by computer simulation.

Stress state of the supporting zones of beams of laminated timber

Providing strength at maximum individual stresses (normal along fibers σx, across fibers σy and tangent) in laminated timber structures, without taking into account the complex stress state, does not provide sufficient strength, and often leads to cracks. This issue requires careful study and the introduction of design rules for mandatory checks of the complex stress state of glued timber with specific recommendations for determining both the individual components of the stresses and zones or points where exactly these checks should be performed.Numerical studies of stress-strain state in beams of different type (ordinary straight-line constant height of cross-section, variable height of cross-section - double-sloping and bent-glued) of glued wood showed a high concentration of all components of the stress state. The analysis of stresses in these zones and the estimation of the complex stress state (SNA) using the calculated strength conditions made it possible to obtain specific recommendations for finding a dangerous place and, as a consequence, to take into account the dangerous concentrations of all constituents of a stressed state in a particular zone.

IMPACT OF DAM ROCKFILL CREEP ON REINFORCED CONCRETE FACE STRESS-STRAIN STATE

Introduction. Rockfill deformations are developed during long time. It is known that most intensive they are during construction period, but their increment continues also during operation period due to creep. Therefore, creep may affect the reinforced concrete face stress-strain state. Nevertheless, search for the scientific and technical information showed that the problem of creep impact on the face strength is poorly studied. Materials and methods. Studies of stress-strain state were conducted with the aid of numerical modeling by finite element method. They were carried out on the example of in-situ Toulnustouc dam, which deformations during the operation period are known by the results of field measurements. For simulation of the time-dependent dam, deformation increment process there was chosen a rheological model of soil and a technique was worked out for calculating the dam stress-strain state. At plotting the rheological model, the use was made of the simplest exponential relationship of time-dependent deformations. Results. The parameters of the rockfill model were determined by selection from condition of matching between the dam design displacements and the field data. For the considered dam, the rockfill creep has not resulted in cardinal changes in the reinforced concrete face stress-strain state. Conclusion. It was revealed that increase of the dam settlements due to creep has a favorable effect: they create additional compressive longitudinal force in the face.

Proposed Design, Model and Calculations of Stress-Strain State of a Landslide Sill Protective Dam of the Inclined Layered Structures

This article deals with the development of a new high-strength construction of a slide protective earth dam, which is based on the use of conventional local geomaterials such as soils, sand, stones, crushed stone, various kinds of crushed rocks etc., in combination with geosynthetic materials erected by inclined layers. The study describes the technology of construction of trapezoidal in the cross section of the earth dam with horizontal and inclined layers of geosynthetics and algorithms of the developed computational mechanical and mathematical model of the study of stress-strain state (SSS). Some steps of the algorithm of the finite element method and the results of the study of the SSS section of the earth dam for different angles of the inclined layers are presented. The analysis of the results obtained by multivariate calculations are presented in the form of strain and stress diagrams. It is concluded that in the construction of the dam inclined layers with angles φ from 0 to 900 with their gradual growth, the deformation values are reduced inversely, which means that the dam will become more stable in comparison with the construction of traditional horizontal layers.

Исследование напряженно-деформированного состояния колесной пары грузового вагона в процессе торможения

Исследование напряженно-деформированного состояния колесной пары грузового вагона в процессе торможения

Experimental and numerical studies of stress-strain state of concrete structures reinforced with polymer-composite reinforcement

Experimental and numerical studies of stress-strain state of concrete structures reinforced with polymer-composite reinforcement

Integrated Evaluation of the Worked-Out Area Partial Backfill Effect of Stress-Strain State of Coal-Bearing Rock Mass

The paper gives information on the engineering solution concerning the extraction of thin coal seams with partial backfill of the worked-out area. Geomechanical model of coal-bearing rock mass has been substantiated. A technique to carry out computational experiment aimed at the processes of coal-bearing rock mass displacement within a zone of extraction influence has been represented. Curves of rock pressure stress components distribution (i.e. horizontal stresses, vertical stresses, and stress intensity) within the front bearing pressure and worked-out area for traditional methods (if roof is controlled by means of complete rockfall) and for selective mining with partial backfill have been plotted. Relying upon the carried out studies of stress-strain state of coal-bearing rock mass, overall conclusion has been made on the advantage of selective mining with partial backfill from the viewpoint of geomechanics of the rock mass behaviour.

STRUCTURAL AND DESIGN SPECIFICS OF SPACE GRID SYSTEMS

The aim of the study is to identify main trends in the development of space grid structures. In order to reach the purpose it is necessary to conduct a review of the known structural concepts, nodal connections and specifics of the space grid structures and to make conclusions on feasibility improvement of the considered structural concepts that make it possible to develop new solutions without disadvantages residing in the analogues. Analysis of papers written by foreign and national scientists and devoted to theoretical, numerical and experimental studies of stress-strain state, influence of different factors on it and geometrical optimization and designing of space grid structures has been conducted in order to achieve the objectives. Space grid structures and, in particular, flat double-layer grid and most frequent nodes have been studied in the paper. The paper contains a short review of the history on development of space grid structures. It has been found that a rapid development of structural designs was caused by scientific and technical progress and, in particular, improvement of physical and mechanical properties of materials, development of calculation methods, application of software systems for simulating behavior of the structure under load, which significantly increased the calculation accuracy and reduced complexity of design. It has been also established that main parameters that have influence on effectiveness of a structural design are geometric dimensions of its modular elements, ratio of its depth to the span. The world experience on development of connection components has been studied in the paper. The paper presents general classification of nodal connections. Main advantages and disadvantages of existing space grid structures are highlighted and it allows to determine possible methods for their improvement. Theoretical research has permitted to establish that the main direction of spatial grid structures improvement consists in development of new node connection types. Several methods for node improvement have been proposed while taking into account the obtained results.

The study of stress-strain state of stabilized layered soil foundations

Herein presented are the results of modeling and analysis of stress-strain state of layered inhomogeneous foundation soil when it is stabilised by injection to different depths. Produced qualitative and quantitative analysis of the components of the field of isolines of stresses, strains, stress concentration and the difference between the strain at the boundary of different elastic horizontal layers. Recommendations are given for the location of stabilised zones in relation to the border of different elastic layers. In particular, it found that stabilization of soil within the weak layer is inappropriate, since it practically provides no increase in the stability of the soil foundation, and when performing stabilisation of soil foundations, it is recommended to place the lower border of the stabilisation zone below the border of a stronger layer, at this the distribution of stresses and strains occurs more evenly, and load-bearing capacity of this layer is used to the maximum.

Simulating of the Composite Cylindrical Shell of the Pipe of the Supply Pipelines Based on ANSYS Package

The simulating of the composite cylindrical shell of the antivibration pipe based on a study of stress-strain state caused with excess pressure was carried out. Contacting interaction of the pipe shall wall in the area bordering the metal flange was conducted. The conducted finite element analysis of the stress state of the composite shell reveals the most loaded areas which represent potential danger in terms of the destruction of rubber-cord array.

Stress intensity factor in welded joints out of double angles in lattice steel structures

Steel lattice structures are characterized by presence of zones with constructive stress concentrations and initial technological defects, which usually occur in a result of hand welding. High level of relative loading typical for steel structures, stress concentration and various defects in the weld zones lead to crack initiation. Analysis of building structures failure has shown that from more than 164 steel structure failures that have occurred in 2001-2010, the lattice structures account for more than 64% of total failures. Earlier performed investigations found that approximately 65% of the failures are caused by development of cracks from welding defects, 10% by the initial crack of cyclic origin, 25% - by high stress concentration. Therefore the design of lattice structures without considering the peculiarities of deformation and fracture of steel in zones of stress concentration leads to increased probability of fatigue and quasibrittle failure. The present paper investigates behavior of welded joints out of equal angles. Numerical and experimental studies of stress-strain state in the region of crack tip located in the cross section of gusset plate breakage were performed. The functional dependence was obtained that characterizes shape, finite dimensions of element, loading scheme and allows defining the stress intensity factor in the investigated section.

Выбор рациональных форм разделки кромок сварных соединений с конструктивным непроваром

Regarding welded constructions, not only their strength is of interest, but also saving of the weld metal consumption. For the latter, constructive faulty fusion of the joint can be used. But such joints suffer from stress concentration at the faulty fusion tip. When high-strength steels are used, this may lead to brittle or quasi-brittle failure, even under low loads. To raise the failure resistance power of fillet welded high-strength steels with the constructive faulty fusion, it is suggested to use a composite weld, where the root pass is made with a ductile (soft) welding rod and the rest of the passes with a high-strength (hard) one. Results of the study of stress-strain state and fracture resistance of mechanically heterogeneous fillet joints are presented, and the effects of fillet's bevelling geometry and ratio of mechanical properties of the hard and the soft weld rod metal are analyzed. The stress-strain state was studied using finite element method (FEM). FEM calculations and experiments with real weld joints demonstrate that the joint strength may be raised and expensive austenitic weld rods may be saved at the same time if composite joints are used in making fillet weld joints of high-strength steels with constructive faulty fusion.

FEM Study of Stress-Strain State of Elements of Harmonic Gear Drive with Hollow Shaft and Intermediate Rollers

Stress-strain state (SSS) of the separator as one of the main elements of the geokhod harmonic gear drive with rolling elements with hollow shaft is considered. The study was conducted by Finite Element Method (FEM) using SolidWorks Simulation software.