Numerical Simulation Of Stress-strain State Research Articles

Numerical simulation of stress-strain state in frozen wall during thawing

Blasting and drilling operations during shaft sinking assume switching off the freezing columns which can lead to stability loss of a frozen wall and inrush of thawed soil into the stope. This work assesses safety of shaft sinking when freezing columns are turned off for a period of four days. It is assumed that the frozen wall loses its bearing capacity when displacement of its unfixed section exceeds 10 cm. Calculations are carried out for silt and sand stratums. Simulation was performed in finite-element software Comsol Multiphysics. Displacements of internal wall were obtained for two initial thicknesses of the frozen wall. In the first case the soil was frozen to the boundary of the future shaft, in the second case initial thickness corresponded to project documentation. It has been shown that frozen wall in silt stratum does not lose its bearing capacity even for complete defrosting. For sand stratum calculated time was equal to 85 days for the first thickness and 24 days for the second thickness of frozen wall.

ЧИСЛЕННОЕ МОДЕЛИРОВАНИЕ УСТОЙЧИВОСТИ БОРТОВ УГОЛЬНЫХ РАЗРЕЗОВ ПОД ДЕЙСТВИЕМ РАСПРЕДЕЛЕННЫХ НАГРУЗОК

The open method of solid minerals winning occupies a significant place in the total opening of the mining complex deposits of the Republic of Kazakhstan. In the energy band, a prominent role belongs to the Ekibastuz coal basin, where a number of large coal strip mine operates. The level of subsurface, equal parts of spoil bank of the external and internal stripping after a while lead to complex problems of ensuring the stability and safety of mining operations. The location of large external rock dumps on the bead surface has a negative effect on the stability of the latter. The purpose of the work was to establish the degree of the external rock dump influence located on the bead surface on the stability of adjacent rock mass of the coalmine depending on the distance of the dump to the upper edge of the side. There was numerical simulation of stress-strain state of adjacent rock mass under action of distributed load from rock dump carried out. It has been shown that studies of any point stability of the array from this type of load should be carried out on the basis of elasticity and the use of the finite element method theory implemented in packages of programs oriented specifically to scientific and engineering applications. There are the methodology and results of numerical modeling of quantitative assessments of various sections stability of the side loaded with an external rock dump with a height of 160m presented on the example of «Ekibastuz» coal mine. Based on a certain theory of rock strength and the criteria for their discontinuity, limit estimates of the critical distance of the external rock dump from the upper edge of the side were obtained, at which the latter may lose stability.

GEOMECHANICAL MODELING IN MINING AT THE ELGINSKY DEPOSIT

Using the Elginsky coal deposit as an example, the relevance of building digital models of geological objects to control the geomechanical condition of open-pit walls is shown. Physico-mechanical properties of overburden rocks are given. The results of numerical simulation of stress-strain state of the rock mass are presented. The directions of general stress displacements and zones of maximum displacements of the open-pit wall are determined and the maps of their distribution are compiled. It is shown that lower benches are more susceptible to tension.

Modeling the stress-strain state of of a municipal solid waste landfill

Introduction. The process of municipal solid waste (further MSW) generation is inextricably linked with the life of humanity. Every day each person generates some, a small amount of garbage. As a result millions of tons of MSW are generated daily in the world which are unsuitable for further use and require disposal. There are various ways of handling MSW including their treatment, recycling and disposal. In Russian Federation the vast majority of MSW are currently located on the specially equipped facilities –– waste landfills. To date the most common waste management strategy remains their placement in a landfill. Waste landfills are arrays of stored waste and are special engineering structures designed for the safe isolation of their contents from the environment. Landfill includes gas exhaust and leachate drainage systems, liner and cover systems. The main component of this structure is waste itself. Mechanical stability of landfills should be provided at all stages of waste storage as well as after it complete filling to designed capacity and at post-closure stage. As the result of deformation of unstable waste, all landfill systems can be destroyed up to the collapse of garbage array leading to the significant environmental and other consequences. One of the most common problems leading to the various incidents at landfills is an incorrect assessment of their stability. MSW landfill is a complex multiphase system in which various interacting processes occur simultaneously. The main factor in the calculation and design of landfills is the forecast of their settlements. Studies by many authors have established that biological decomposition has a significant impact on the properties of MSW after which the waste is considered as the landfill soil with a particle size of up to 20 mm. Materials and methods. The paper presents the methodology and the results of numerical modeling of stress-strain state of the designed object “Waste Landfill”. The facility is an array of municipal solid waste of 38 meters high. Waste is stacked in the layers of 1.75 m thick. Each waste layer is covered by the loam cover of 0.25 m thick. Stress-strain state of municipal solid waste including biological creep was modelled using well-known “Soft-Soil-Creep model” (SSC-model). Results. The results of numerical simulation of stress-strain state of the waste pile at all stages of the filling and in the post-closure period are presented. An assessment of the increase in the capacity of the landfill due to the compaction and biological creep has been performed. Stability analysis of the landfill and potential failure mechanisms at different stages of filling and operation are presented. Conclusions. Numerical modeling of stress-strain state of the MSW array using the “Soft-Soil-Creep model” allows to analyze the stability of the waste pile at any stage of landfill filling and evaluate the increase in landfill capacity due to the waste settlement taking into account the mechanical creep and biocompression during layer-by-layer filling.

Применение метода декомпозиции области для решения задачи контактного взаимодействия осесимметричных тел

Several variants of domain decomposition method are presented, including overlapping methods (multiplicative and additive Schwarz methods) and nonoverlapping methods (Neumann-Dirichlet and Neumann - Neumann). The results of their application for solving the two-dimensional problem of loading a section of an elastic pipe with pressure are considered. The dependence of the number of external iterations on the grid step and on the number of subdomains has been investigated. It has been shown that the best results are obtained for the two-level Schwarz additive method. This method is generalized to the case of solving the problem with the contact of the column of the body. To take into account the contact between the bodies when solving the local problem in each subdomain, the Neumann -Dirichlet method is used. Results of application of two-level Schwarz additive method for numerical simulation of stress-strain state of fuel element section are presented.

Numerical simulation of bellows compensators stress-strain state in air in-take system

The numerical simulation of the stress-strain state of the bellows compensator in air intake system is presented. Bellows expansion joints are an integral part of many air or fluid supply systems in many installations and vehicles. A nalytical methods are ineffective due to complex geometry in solv ing the problem of determining the stress-strain state of the bellows compensator in the air intake system, so it is advisable to use numerical calculation methods. T hree-dimensional finite elements in the form of a tetrahedron were used t o construct a finite-dimensional model. Analysis of the stress-strain state has been carried out of the bellows compensator and its main components: the cardan ring, the crosspiece, the inner hinge ring, the outer hinge ring .

Numerical Simulation of Stress-Strain State of Thick Coal Seam at the End of Long-Pillar Work

The article deals with the redistribution of stresses and the formation of fracture regions at the final stage of the excavation post. Considered various options in the formulation of the problem, describe the solution in full and the additional stresses. Presented mechanical model describing the redistribution of the original stresses caused developing mining operations; formation of discharge zones and the additional load near the bottom of the lava and around the DC; areas of possible fall-outs of rocks; displacement of rocks, in particular faith-vertical in roof of recreation center and horizontal to vertical outcrops of in-fighting and dismantling the camera. The deformation model used in solving the problems is built taking into account the possible plastic deformation of both coal and the immediate roof of the formation, which allows taking into account both the fracture of the massif and the nonlinear deformation of the material itself. It is emphasized that the parameters of plasticity can be determined from the solution of the inverse problem using experimental data obtained in situ.

Numerical simulation of stress-strain state of oblique sections of reinforced concrete structures subjected to compression and bending on yielding supports under short-term dynamic load

This research is aimed at studying the method for improving blast resistance of buildings and structures by using yielding supports. The paper reports the data on dynamic analysis of reinforced concrete elements subjected to compression and bending on yielding supports under the condition of elasto-plastic stress-strain state performed in ANSYS software package. Algorithms and techniques for dynamic amplification factor calculation for reinforced concrete elements subjected to compression and bending are presented. The paper provides load diagrams of dynamic amplification factors with the account of yielding capacity of supports for subsequent dynamic analysis of structures for equivalent static load.

FINITE-ELEMENTAL ANALYSIS OF INFLUENCE OF DAMAGES OF BEAMS ON THE GENERAL TECHNICAL CONDITION OF MONOLITHIC REINFORCED CONVERGENCE

Purpose. To perform a simulation to estimate the impact of corrosion damage to the reinforcement of monolithic reinforced concrete flooring on the bearing capacity of a unit width of overlap and overlap in general. Methodology. The integral monolithic reinforced concrete overlay of the boiler house with overall dimensions of 12 × 12 m was to be investigated. The grid of the column was 6 × 6 m. The damage in the form of complete destruction of the protective layer of concrete of one of the 12 secondary beams and corrosion damage to 30% of its bearing reinforcing bars was investigated. Numerical simulation of stress-strain state of reinforced concrete structures was performed in the training version of the NASTRAN Femap 10.1.1 SC 32bit system. Two types of calculation are carried out: 1) calculation of a plate of unit width (in accordance with current regulatory documents); 2) calculation of the entire reinforced concrete floor (taking into account its joint work). Findings. The following is revealed: calculation № 1 proves the necessity of arrangement of strengthening of damages of a secondary beam of monolithic reinforced concrete floor. After the device is strengthened by the cage from the corners of the secondary beam, the stress is reduced both in the reinforcement and in the reinforcing bars to the stress level in the undamaged slab. Calculation № 2 shows that the arrangement of reinforcement of the clip from the corners of the secondary beam with cored reinforcing bars, taking into account the joint work of the whole plate, is not needed. Originality. Numerical modeling of the stressed-deformed state of reinforced concrete slab of unit width taking into account damages and the entire monolithic reinforced concrete slab is carried out, and the obtained results are analyzed. Practical value. The order of creation of models of reinforced-concrete designs and their finite element analysis is briefly given.

Численное моделирование напряженно-деформированного состояния трубопровода при пучении грунта

Численное моделирование напряженно-деформированного состояния трубопровода при пучении грунта

Numerical simulation of stress-strain state of electrophoretic shell molds

In the foundry engineering, castings obtained in one-piece non-gas-generating high-refractory electrophoretic shell molds (ShM) by investment patterns (IP) have an increased rejects percentage associated with low deformation resistance and crack resistance of the SM at different stages of their formation and manufacturing. Crack resistance of the ShM based on IP depends mainly on their stress-strain state (SSS) at various stages of mold forming. SSS decrease significantly improves their crack resistance and decreases their rejects percentage of castings occurring due to clogging and surface defects. In addition, the known methods of decreasing the SSS are still poorly understood. Thus, current research trends are to determine SSS at each stage of ShM forming and develop the ways to decrease it. Theoretical predicting of crack formation in multiple-layer axisymmetric shell molds is given in the work [1], and SSS of multiple-layer axisymmetric shell molds is given in the work [2]. Monolayer electrophoretic ShM had a lack of concern in this field, thus it became an argument for the present workMathematical Model of ShM SSS

APPLICATION OF NUMERICAL SIMULATION AND COMPARATIVE ANALYSIS OF THE MACHINE ARRANGEMENTS TO INCREASING THE ACCURACY OF ICE CYLINDER HEAD VALVE SEATS MACHINING

The article provides a general approach to choosing equipment for machining cylinder head valve seats of ICE including short-run, experimental manufacturing and repair. The authors have carried out numerical simulation of stress-strain state of spindle units for various machine arrangements put in the base of specialized machines for valve seats machining manufactured by the main world brands of this equipment type. The results of simulation aid in determining the fields of application for different types of machines depending on the sizes of seats to be machined, which allows giving practical recommendations regarding the choice of equipment for solving specific production tasks.

Numerical Simulation of Stress-Strain State of Asphalt Concrete Pavement on the Carriageway of the South Bridge in Kiev

Taking account of the fact that there is complex space load on the carriageway of the South highway stream crossing it is reasonable to use numerical method for determination of stain and tension pavement condition based on the solution of elasticity theory equations – Finite Element. The application of numerical modeling is determined by the fact that load patterns are becoming more complicated and require spacial concept in order to enhance the quality of overpass pavement design. Atypical example for deformation fields distribution in one of the bridge crossing sections under traffic load is provided. The analysis of the investigation results enables us to conclude that the minimum tension stress in the pavement will be at the pavement thickness 90 mm and stamp diameter 300 mm. under this condition the tension in the pavement will not exceed 3.7 MPa.

Plasticity and creep of steel 3 at room temperature

Results of experimental investigations at the room temperature of specimens made from steel 3 are presented in a paper. It was found, that steel 3 at room temperature demonstrates essential creep, when strains are more than 2%. The anisotropy of creep properties for considered steel was fixed. The values of constants which are included in suggested state equations for steel 3 at temperature 20 С were determined. Comparison between experimental and calculated data show the satisfactory ability of use the suggested state equations for numerical simulation of stress-strain state’s varying in conditions, when load causes the instant stresses which are more than yield limit as well as instant plastic strains occur.

Numerical Simulation of Stress-Strain State for Nonhomogeneous Shell-Type Structures Based on the Finite Element Method

Projective-iterative version of finite element method has developed for numerical simulation of the stress-strain state of nonhomogeneous shell-type structures (shells with openings). Plastic deformation of the material is taken into account when using the method of elastic solutions that reduce the solution of elastoplastic problems to solution of elastic problems. Developed PIV’s significant savings of computer calculation has been compared with the calculation on a fine mesh of traditional FEM. Designed scheme allows analysis of the mutual influence of openings. Analysis of the transformation zone of plastic deformation is developed. For definiteness, the cylindrical shell structures with several rectangular openings are considered.

Numerical simulation of stress-strain state near crack tip in a compact tensile specimen

A computational scheme has been developed and a numerical simulation of the stress-strain state near the crack tip is performed at different levels of the stress intensity factor using a compact tensile specimen as an example. The authors analyze the influence of the finite element size near the crack tip and compare the results obtained in different codes (software packages) for different crack geometries.