Pulse load on a stationary barrier during an explosion in water

С использованием экспериментальных данных о взрывах в воде найдена аналитическая зависимость распределения удельного импульса взрывной нагрузки по длине балки. Учтены эффекты отражения возмущенного потока воды от поверхности преграды, глубина ее расположения в водоёме, взаимное расположение сферического заряда ВВ и преграды в воде, физические характеристики заряда. Using experimental data on explosions in water, an analytical dependence of the distribution of the specific impulse of the explosive load along the length of the beam is found. The effects of reflection of the disturbed water flow from the barrier surface, the depth of its location in the reservoir, the mutual location of the spherical explosive charge and the barrier in the water, the physical characteristics of the charge are taken into account.

Approaches to assessing the effectiveness of earthquake predictions using the LURR (load-unload response ratio) method on Sakhalin

A retrospective analysis of the seismicity of Sakhalin from 1997 to 2019 was performed to demonstrate the possibilities of the LURR technique recently in previous our work. The following results were obtained: 84 % of earthquakes (16 out of 19, with M ≥ 5) are predicted, 25% alarms (4 out of 15 predicted areas) were false. This paper proposes an analytical dependence to describe the forecast effectiveness (Ke) for this research. The extremes of Ke were found at the value of the alarm period of 12 and 24 months. At the same time, Ke is significantly higher for the alarm period of 24 months and decreases after a two-year alarm period. Another way to prove the results obtained is the random spatio-temporal distributions of the predicted objects (19 earthquakes with M ≥ 5). 10 such random sets have been assigned to 15 predicted areas, the result shows a significant advantage of a real sample over random ones, and also practically confirms the reliability of the algorithm for using the LURR technique. The methodology and results of this work can serve as practical recommendations for working with the LURR method for seismologists.

Ensuring fire safety during the operation of oil and gas equipment based on the results of compact specimens tests

The paper considers the application of the test method of compact specimens to assess the degree of damage of steel elements of oil and gas equipment. According to experimental data, an analytical dependence was obtained linking the degree of damage to the index of the specific fracture work, intended to assess the possibility of safe operation of explosive and fire-hazardous equipment.

USING OF THE MATHEMATICAL APPARATUS REGRESSION ANALYSIS TO UNIFY THE CALCULATING METHODOLOGY FOR THE T-64B TANK'S OVERHAUL LIFE

The subject matter of the article is the life cycle of a T-64B tank sample during the period from normal operation in a combat training group to resource consumption and carrying out average and capital repairs. The goal of the study is to develop a model of dependence of inter-repair service life of the T-64B tank sample on the machine operating conditions and, on its basis, a methodology for controlling the parameters of individual assemblies and systems of the tank sample during its life cycle. The tasks to be solved are: to analyze the results of statistical records of tank system failures and damages number and identify the predicates set affect the inter-repair service life of the machine depending on conditions of its tasks for the intended purposes; to create the regression equation for getting the unified analytical dependence of inter-repair service life of the T-64B tank sample in the period from normal operation in training and combat group to service life and overhaul; to investigate specific influence of reliability indices on the machine's service life. General scientific and special methods of scientific knowledge are used. The method of hierarchy analysis, mathematical apparatus of probability theory and multidimensional statistical analysis were used. The following results are obtained. A set of predicates influence the inter-repair service life of the machine depending on conditions of its tasks for the intended purposes fulfillment has been determined. A regression equation has been drawn up to obtain a unified analytical dependence of the overhaul life of a T-64B tank sample during the period from normal operation in a combat training group to the development of a resource and carrying out of intermediate and complete overhauls were drawn up. Engineering solutions have been proposed to implement a methodology for monitoring the parameters of individual units and systems of the tank sample during its life cycle, namely integrated real-time monitoring of oil condition and recording of engine operating hours under various load conditions. Conclusions. The space of features characterizes the conditions of the tank sample tasks for its intended purposes, includes service life, crew training, operation, seasonality of the unit’s performed tasks nature, machine operating time since the last service and range of the vehicle before the next overhaul. The analytical relationship between the individual factors determining the conditions under which the T-64B tank sample performs its tasks for the intended purposes and the machine's service life consumption as a dependent variable can be determined in the form of a regression equation. Differentiated control of the parameters of individual assembly units and systems of the tank sample plays a leading role in ensuring the combat readiness and efficiency of the use of aging samples of weapons, insures personnel against possible accidents and catastrophes, sudden failures.

Ensuring a Stable Relative Area of Burnishing of Partially Regular Microrelief Formed on End Surfaces of Rotary Bodies

The scheme of arrangement of grooves of partially regular microrelief of type II shifted by 0.5 angular pitch is considered. Such grooves are formed by vibration on end faces of rotary bodies. An analytical dependence was obtained to determine the relative area of a partially regular microrelief depending on the geometric parameters of V-shaped grooves. The parameters of the grooves of a partially regular microrelief formed at different distances from the center of rotation are determined, at which the value of the relative area of the partially regular microrelief formed on the treated surface will be stable.

On the issue of the oretical substantiation and development of a cutting working body for harvesting industrial hemp

The interaction of a knife with a stalk of industrial hemp in the process of unsupported cut is described. An analytical dependence of the critical cutting force on the physicomechanical properties of the stem and blade geometry is obtained. The factors influencing the shape of the cutting tooth are analyzed. The profiles of cutting segments have been developed taking into account the peculiarities of the structure of the industrial hemp stem.

Voltage spectral structure of the thermocouple with temperature dependent wires

The article presents a study of the origin of extra harmonics in the frequency spectrum of thermocouple output signal when being heated by sinusoidal waveform current. It is natural to have the first harmonic, which arises according to Ohm’s law, as a product of current and the total resistance of thermocouple and junction conductors, as well as the Peltier, Thomson effects, and the presence of the second harmonic, which is caused by a heating of junction and thermocouple conductors. The fact that third and higher harmonics arise when the resistance of conductors and junction is thermally dependent was identified. The analytical dependence of the resulting voltage across the thermocouple terminals as a function of the total resistance of conductors and junction, and the voltages due to the effects of Joule, Seebeck, Peltier and Thomson, is established. Based on the analysis of the obtained function and experimentally obtained voltage spectra across the terminal of the thermocouple, an assumption was made about the nature of the voltage spectrum that heats thermally dependent wires of the thermocouple. Recommendations are given to reduce the influence of the first, third and higher harmonics, which are uninformative, and to separate the voltage of the second informative harmonic, which is used to get frequency response of the thermocouple. Keywords: frequency response; thermocouple; EMF; spectrum; thermally dependent resistance; voltage

Calculated Model of Endurance Limit Estimation Based on Structural-Strain Analysis of the Critical Condition of Ferrite-Perlite Steels with Macrocracks in Ship Structures

In this study, a structural-deformation analysis of the process of crack development is performed, on the basis of which an engineering methodology is developed for assessing the endurance limit and resource of large-sized structures. A simple analytical dependence (correlation аналитическая зависимость) was obtained, which allows one to determine the critical size of macrocracks for ferritic-pearlitic steels without using the well-known Griffith formula. The results of calculating the cracks critical lengths of various steels depending on their yield strength are presented. The analytical dependence of the calculation of the fatigue limit for the most dangerous symmetric loading cycle according to the standard set of mechanical characteristics of ferrite-pearlite steel is presented. The obtained results make it possible to calculate the endurance limit of structural elements of marine equipment and other structures subject to cyclic loads

OPTIMIZATION OF THE HEAT AND HUMIDITY MODE OF MULTI-LAYER BUILDING ENCLOSING STRUCTURES

The article presents a methodology for determining the required resistance to vapor permeation of the outer layer of a multilayer building envelope, based on the condition that there is no condensation of water vapor in it. When deriving the formula, an analytical dependence was used to determine the elasticity of saturated water vapor, obtained by the authors of this article. With the help of the proposed technique, the assessment of the thermal and humidity regime of the outer wall, insulated facade system using thin-walled plaster, as well as layered masonry using expanded polystyrene and basalt plates as insulation was made. The results of the calculation of the indicated external walls are presented, which show that condensation of water vapor is possible in layered masonry. The proposed analytical dependence for determining the maximum allowable resistance to vapor permeation of the outer layer of a multilayer enclosing structure is recommended to be used in engineering calculations of the humidity mode of external enclosures of buildings and structures.

ANALYTICAL CALCULATION OF DEFORMATIONS OF A PLANAR SINGLE-SPAN BEAM GIRDER WITH FOUR SUPPORTS IN THE MAPLE SYSTEM

A schema of a statically determinate beam girder with a regular structure, which has two supports at the ends, is considered. The descending and ascending braces have different inclination angles. In the system of symbolic mathematics Maple, the analytical dependence of the deflection of the structure and displacement of one of the three movable supports on the number of panels is derived by induction. In the procedure for generalizing several solutions to the general case, the operators rgf_findrecur and rsolve are used to compose and solve recurrent equations, which are satisfied by the coefficients of the sought formula. Cases of kinematic degeneration of the structure are found for a certain number of panels, the corresponding schemes of possible speeds are given, and a static interpretation of this phenomenon is given.