A multi-level mathematical model was used to estimate the stressed-strained state of a cylindrical reservoir with a defect in the wall shape in the form of a dent; the concentration of stresses in the defect zone was studied. The proper choice of the mathematical model was verified; it has been shown that the engineering assessment of the stressed-strained state of the wall of a cylindrical tank with the variable thickness could employ ratios for a cylindrical shell with a constant wall thickness. The spread of values is 2‒10 %. This indicates the proper choice of the mathematical model, as well as the fact that it is possible, for an engineering assessment of the stressed-strained state of the wall of a cylindrical tank with variable thickness, to use the ratios for a cylindrical shell with a constant wall thickness. The stressed-strained state of the dent zone in the tank wall was numerically estimated, which proved the assumption of significant stress concentrations in the dent zone and indicated the determining effect on the concentration of stresses in the dent zone exerted by its geometric dimensions and its depth in particular. The concentration of stresses in the zone of dents in the tank wall was investigated in the ANSYS programming environment at different sizes of dents on the tank wall, for which two dimensionless parameters were introduced: the dimensionless radius of the dent and the dimensionless depth of the dent. Based on the results of a numerical study into the stressed-strained state of the dent zone in the tank wall, graphic dependences were derived of the stress concentration coefficient on the dimensionless depth of the dent for various values of the dimensionless radius of dents, which does not exceed 2 % of the indicator. Based on fitting the stress concentration curves on the dimensions of the dent and tank, a formula was derived for calculating the stress concentration coefficient as a function of the dimensionless radius ξ and the dimensionless depth ς of the dent. The resulting formula makes it possible, with known dimensionless parameters of the depth and radius of the dent, to determine the coefficients of stress concentration in the dented zone of the tank wall. На основе использования многоуровневой математической модели оценено напряженно-деформированное состояние цилиндрического резервуара с дефектом формы стенки в виде вмятины и изучена концентрация напряжений в зоне дефекта. Проведена верификация правильности выбранной математической модели, и показано, что для инженерной оценки напряженно-деформируемого состояния стенки цилиндрического резервуара с переменной толщиной можно воспользоваться соотношениями для цилиндрической оболочки с постоянной толщиной стенки. Разброс значений составляет 2–10 %. Это указывает на правильность выбранной математической модели, а также на то, что для инженерной оценки напряженно-деформируемого состояния стенки цилиндрического резервуара с переменной толщиной можно воспользоваться соотношениями для цилиндрической оболочки с постоянной толщиной стенки. Проведена численная оценка напряженно-деформированного состояния зоны вмятины в стенке резервуара доказала предположение о значительных концентрациях напряжений в зоне вмятины и указала на определяющее влияние на концентрацию напряжений в зоне вмятины ее геометрических размеров и особенно, ее глубины. Исследована концентрация напряжений в зоне вмятин стенки резервуара в среде ANSYS при различных размерах вмятин на стенке резервуара, где введены два безразмерных параметра: безразмерный радиус вмятины и безразмерная глубина вмятины. По результатам численного исследования напряженно-деформированного состояния зоны вмятины в стенке резервуара получены графические зависимости коэффициента концентрации напряжений от безразмерной глубины вмятины для различных значений безразмерного радиуса вмятин и не превышает 2 % показателя. На основе аппроксимации кривых зависимостей концентрации напряжений от размеров вмятины и резервуара получена формула для расчета коэффициента концентраций напряжений в зависимости от безразмерного радиуса ξ и безразмерной глубины ς вмятины. Полученная формула позволяет при известных безразмерных параметрах глубины и радиуса вмятины...

This paper proposes a mathematical model and a procedure for calculating the thermal state of the enclosing structure of the building, which includes an energy-active panel that accumulates solar radiation due to the phase transition of the heat-accumulating material. The mathematical model is based on a two-dimensional non-stationary nonlinear equation of thermal conductivity, which describes the process of heat transfer in the bearing layer of the enclosing structure and the energy-active panel. The model also includes equations describing radiant heat transfer between opaque and translucent bodies. To correctly describe solar insolation, the ASHRAE 2009 model was used in conjunction with the daily change in the position of the Sun in the sky. To solve the system of equations that make up the mathematical model, an iterative procedure has been developed, which involves alternating solution at each time step of the two-dimensional equation of thermal conductivity and a set of algebraic equations of convective and radiant heat transfer. The study’s result established that the amount of accumulated energy in the heat-accumulating material of the phase transition during daylight hours increases significantly, from 15 to 35 %. At night, the surface temperature of the heat-accumulating element in structures using a material with a phase transition is greater than in the case of heat accumulation only in the bearing layer. As a result, it is possible to select from 70 to 120 % more accumulated heat while the presence of high-thermal partitions in a heat-accumulating material with a phase transition contributes to an increase in accumulated heat and usable heat

This paper considers the structural solution for a main above-ground pipeline with a pre-stressed winding, which makes it possible to improve the efficiency of operation and reduce material consumption. The results from studying experimentally the features in the operation of prestressed pipelines under static operating loads are given. It is shown that the radial movements of the wall of a pre-stressed pipeline are constrained by the strained winding, which prevents its deformation. It was revealed that increasing the tension force of the winding wire reduces circular stresses in the pipeline wall by 1.3...1.6 times and increases meridional ones by 1.2...1.4 times. The experimental study into the models of prestressed pipelines with free vertical and horizontal oscillations has established the dependence of frequency characteristics on the operating conditions and pre-stress parameters. It was found that the envelope amplitude on the oscillogram of free attenuated oscillations takes the shape of an exponent, which indicates the damping effect of the pre-stress. Analysis of the change in the dynamic characteristics of the models depending on the pre-stress force has revealed that the frequencies of free oscillations increase by 1.5÷1.6 times while the oscillation decrement decreases by 1.2÷1.25 times. This paper reports the results of studying the influence of pre-stress parameters on the stressed-strained state of the pipeline model under forced horizontal and vertical oscillations. It is shown that the diagrams of circular dynamic stresses and deformations in the models of a prestressed pipeline are smoother compared to similar characteristics of a conventional pipeline tested at the same experimental parameters. The study results have made it possible to quantify the features in the operation of a pre-stressed pipeline under static and dynamic influences, taking into consideration the pre-stress parameters and operating conditions.

In current conditions, higher educational institutions have to develop innovative mechanisms of education quality assurance independently. One such mechanism is the implementation of the European Foundation for Quality Management (EFQM) model, although the 9001:2001 International Organization for...

This paper conducted an experimental study of reduced models of a main gas pipeline for avalanche damage considering operational conditions. Two options were considered as a method of avalanche damage prevention: single steel rings at the crack edges and steel winding with a winding pitch of 0.25 m. For the tension force, 5% of the steel wire breaking force was taken, which was equal to 1 mm. The ambient environment was simulated by a climatic chamber, where two options of temperature loads were considered: +20 °C and −10 °C. It was found that reinforcement with single rings of pipeline models under conditions of positive (+20 °C) and negative (−10 °C) temperatures showed that the crack opening width in the ring direction decreased 1.63 times and 1.9 times, accordingly. The crack length (longitudinal direction) decreased 2.18 times and 2.45 times, accordingly. The reinforcement of the pipeline models with prestressed wire winding on the crack propagation under conditions of positive (+20 °C) and negative (−10 °C) temperatures showed that the width of the crack opening in the ring direction decreased 1.5 times and 1.46 times, accordingly. The crack length (longitudinal direction) decreased 1.4 times and 1.44 times accordingly, which is a positive moment in addressing the issue of the localisation and stoppage of a crack fracture in main gas pipelines. Simultaneously, the analysis of the prestressed pipelines model test results on crack fracture propagation showed that single rings are more effective, which decreased the crack opening width by 1.1 times and the crack length up to 1.5. Therefore, the experimental results obtained positively complement the available methods of crack localisation in main gas pipelines, which can be used by engineers and research communities when designing or reinforcing existing operating main steel gas pipelines.