scholarly journals Determination of the safety factor of cement stone based on numerical modeling of the stress-strain state of the near-wellbore zone, taking into account the change in the elastic-strength properties of cement during its hardening and under the influence of an acid reagent

2021 ◽  
pp. 8-16
Author(s):  
S. N. Popov ◽  
Keyword(s):  
Finite Element ◽  
Numerical Modeling ◽  
Safety Factor ◽  
Strain State ◽  
Strength Properties ◽  
Cement Stone ◽  
Elastic Model ◽  
Stress Strain ◽  
Stress Strain State ◽  
Acid Reagent

The results of laboratory studies of the elastic-strength properties of cement stone samples depending on the hardening time and the effect of an acid reagent, and approximated dependences of the change in the elastic modulus, Poisson's ratio and strength properties, depending on the time characteristics for two types of plugging materials are presented. A finite element scheme of the nearwellbore zone has been developed, taking into account the cement stone and the production casing. The results of numerical modeling of the stress-strain state of columns with a diameter of 146 and 178 mm, cement stone and reservoir rocks near the well based on an elastic model are presented. The analysis of the stress field for the occurrence of zones of destruction in the cement stone using the Coulomb-Mohr criterion is carried out. It is shown that, depending on the time of hardening and the effect of an acidic reagent, cement does not collapse and retains a sufficient safety factor. Keywords: cement stone; plugging material; elastic-strength properties; near-wellbore zone; numerical model; finite element method; stress-strain state; safety factor.

Estimation of the accuracy of numerical analysis for the deformed state of power structures of technical objects

2018 ◽  
Author(s):  
А.Н. Рогалев ◽  
С.В. Доронин ◽  
В.В. Москвичев
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
Safety Factor ◽  
Stiffness Matrix ◽  
Strain State ◽  
Power Structures ◽  
Safety Factors ◽  
Rounding Errors ◽  
Stress Strain ◽  
Stress Strain State

Под силовыми конструкциями понимают технические устройства, составленные из различных частей, воспринимающие комплекс эксплуатационных нагрузок в штатных и аварийных режимах нагружения. При решении прикладных задач исследования напряженно-деформированных состояний силовых конструкций важна оценка степени близости к точному приближенного решения, полученного на вполне определенной сетке конечных элементов с конечной величиной шага сетки. С учетом влияния ошибок округления сходимость метода конечных элементов контролировать сложно: при большом числе конечных элементов решение может расходиться из-за накапливающихся ошибок округления, даже если условия сходимости выполняются. Описанное в статье применение методов обратного анализа ошибок позволяет достаточно точно контролировать точность численных оценок деформированного состояния силовых конструкций, что подтверждают расчеты, выполненные для практических задач. The solution of applied problems of technogenic safety, survivability, risk and protection is performed for structures which are close to limiting states. These states are characterized by decreasing safety factors down to one. In this case a mistaken estimation for safety factor may cause the situation when the calculated safety factor will be greater than one but the real safety factor will be less than one. Safety factors estimation is performed on the basis of calculation for stress-strain state characteristics. Thus, the issues of accuracy and reliability of determining stresses and deformations are an integral part of the problem of man-made safety. In the numerical analysis of the stress-strain state, the stiffness matrix of the design model is formed, the dimension of which reaches up to tens of millions. A large number of computations for tasks of this dimension is presumably leading to significant rounding errors. Ensuring the grid convergence of results by decreasing the grid spacing is inconsistent with the growth of computational errors due to rounding. For finite element analysis of power structures of technical objects, methods of a posteriori reverse error analysis are proposed that control the effect of rounding errors on the result when solving a solving system of linear algebraic equations. The coefficient matrix of this system is the stiffness matrix of the finite element model. The basic idea is to obtain and solve a system of equations with a known exact solution. Comparison of the results of exact and numerical solutions allows us to estimate the magnitude of the error.

КОНСТРУКТИВНО-ТЕХНОЛОГІЧНІ ОСОБЛИВОСТІ ХВОСТО-ВИХ БАЛОК СІТЧАСТОГО ТИПУ З ПОЛІМЕРНИХ КОМПО-ЗИЦІЙНИХ МАТЕРІАЛІВ ВЕРТОЛЬОТІВ ТРАНСПОРТНОЇ КАТЕГОРІЇ

2020 ◽  
pp. 15-30
Author(s):  
А. Г. Гребеников ◽  
И. В. Малков ◽  
В. А. Урбанович ◽  
Н. И. Москаленко ◽  
Д. С. Колодийчик
Keyword(s):  
Finite Element ◽  
Strain State ◽  
Layer Structure ◽  
Metal Structure ◽  
Element Model ◽  
Stress Strain ◽  
Element Analysis ◽  
Mesh Structure ◽  
Stress Strain State ◽  
Mesh Structures

The analysis of the design and technological features of the tail boom (ТB) of a helicopter made of polymer composite materials (PCM) is carried out.Three structural and technological concepts are distinguished - semi-monocoque (reinforced metal structure), monocoque (three-layer structure) and mesh-type structure. The high weight and economic efficiency of mesh structures is shown, which allows them to be used in aerospace engineering. The physicomechanical characteristics of the network structures are estimated and their uniqueness is shown. The use of mesh structures can reduce the weight of the product by a factor of two or more.The stress-strain state (SSS) of the proposed tail boom design is determined. The analysis of methods for calculating the characteristics of the total SSS of conical mesh shells is carried out. The design of the tail boom is presented, the design diagram of the tail boom of the transport category rotorcraft is developed. A finite element model was created using the Siemens NX 7.5 system. The calculation of the stress-strain state (SSS) of the HC of the helicopter was carried out on the basis of the developed structural scheme using the Advanced Simulation module of the Siemens NX 7.5 system. The main zones of probable fatigue failure of tail booms are determined. Finite Element Analysis (FEA) provides a theoretical basis for design decisions.Shown is the effect of the type of technological process selected for the production of the tail boom on the strength of the HB structure. The stability of the characteristics of the PCM tail boom largely depends on the extent to which its design is suitable for the use of mechanized and automated production processes.A method for the manufacture of a helicopter tail boom from PCM by the automated winding method is proposed. A variant of computer modeling of the tail boom of a mesh structure made of PCM is shown.The automated winding technology can be recommended for implementation in the design of the composite tail boom of the Mi-2 and Mi-8 helicopters.

Analysis of the stress-strain state of copper M0B under different schemes of equal channel angular pressing and its effect on the structure and physical and mechanical properties

2019 ◽  
pp. 47-53
Author(s):  
L. F. Sennikova ◽  
G. K. Volkova ◽  
V. M. Tkachenko
Keyword(s):  
Equal Channel Angular Pressing ◽  
Strain State ◽  
Physical And Mechanical Properties ◽  
Strength Properties ◽  
Stress Strain ◽  
Loading Pattern ◽  
Stress Strain State ◽  
Angular Pressing ◽  
Fine Copper ◽  
Copper Structure

The results of studies of the stress-strain state of copper M0b after deformation under different schemes of equal channel angular pressing (ECAP) are presented. The level of macro and micro stresses in copper has been determined in various ECAP modes. It is shown that the strength properties, deformation porosity and parameters of the fine copper structure differ depending on the loading pattern.

scholarly journals On the issue of dynamic loading of supporting structures of special wheeled chassis

2019 ◽  
pp. 73-83
Author(s):  
V. I. Tarichko ◽  
P. I. Shalupina
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Dynamic Loading ◽  
Strain State ◽  
Element Model ◽  
Stress Strain ◽  
Full Size ◽  
Equivalent Stresses ◽  
Stress Strain State ◽  
Supporting Structures

The paper focuses on a method for assessing the dynamic loading of the frame of a special wheeled chassis when it moves on roads of various categories. Based on the developed finite element model of the frame, we obtained and analyzed full-size patterns of the stress-strain state of the frame and oscillograms of equivalent stresses in the most loaded zones of the frame.

scholarly journals The stress-strain state of gondola mounting bracket of a transport aircraft

2020 ◽  
pp. 117-123
Author(s):  
Sergii Trubachev ◽  
Olga Alexeychuk
Keyword(s):  
Finite Element ◽  
Power Plant ◽  
Strain State ◽  
3D Model ◽  
Stress Strain ◽  
Transport Aircraft ◽  
Finite Element Grid ◽  
Stress Strain State ◽  
Heavy Loads

The bracket is used to attach the gondola, which is an important part of the aircraft power plant. The gondola is constantly subjected to heavy loads when starting the engine, in flight, takeoff and landing. Therefore, the strength of the brackets of its attachment is very important. The geometric 3D model was built in SOLIDWORKS and imported for further calculations in ANSYS. A grid of tetraidal elements was created by the program. Thanks to the obtained FE (finite element) grid, we make the calculation of the stress strain state. Comments are provided on changes in the geometric and mass parameters of the bracket, based on the results of calculations.

scholarly journals Settlement and bearing capacity of water-saturated soils of foundations of finite width under static impact

Vestnik MGSU ◽  
2021 ◽  
pp. 463-472
Author(s):  
Zaven G. Ter-Martirosyan ◽  
Armen Z. Ter-Martirosyan ◽  
Ahmad Othman
Keyword(s):  
Bearing Capacity ◽  
Strain State ◽  
Water Saturation ◽  
Strength Properties ◽  
Finite Width ◽  
Stress Strain ◽  
Linear Deformation ◽  
Stress Strain State ◽  
Linear And Nonlinear ◽  
Water Saturated

Introduction. In case of brief exposure to static loads or dynamic loads, in conditions of absence of drainage, distribution of total stresses between the skeleton of soil and pore gas-containing water should be taken in account. The situation of the stress-strain state of the base is further complicated when we consider the degree of water-saturation of soil of the foundation (0.8 < Sr ≤ 1). The aim of the study is to pose and solve problem of the stress-strain state of a water-saturated soil massif, Including settlement and bearing capacity of a water-saturated base of a foundation of finite width, depending on the degree of water saturation of soils, taking into account the linear and nonlinear properties of the skeleton of soil and the compressibility of pore gas-containing water. Materials and methods. Henckyʼs system of physical equations are used as a calculation model to describe the relationship between deformation and stresses of soil, which takes into account the influence of the average stress on the deformation and strength properties of the soil. This system allows us to represent the linear deformation of the soil as the sum of the volumetric and shear components of the soil of this deformation. In addition allows us too to determine the deformation of the layer of soil, as part of the compressible thickness of the base of foundation with finite width under conditions of free deformations. Results. Depending on the linear and nonlinear deformation parameters, the settlement can be developed with a damped curve (S – p) and stabilize, and can be developed with a non-damped curve (S – p) and moved to the stage of progressive settlement. Conclusions. Solutions have been made for cases when the water-saturation of the base soils changes in the range of 0.8 to 1.0. It is shown that the settlement and bearing capacity of a water-saturated base significantly depends on the degree of water saturation of soils.

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