Experimental Theoretical Research Research Articles

SPEED-STRENGTH PREPAREDNESS AS ONE OF THE BASIC PRINCIPLES IN JUDO

The article is aimed at identifying the ways of development of speed- strength abilities of judoists in domestic and foreign literature sources. The ways of development of speed-strength abilities of judoists and aspects of their use in competitive activity to achieve higher results in competitions are revealed. The most common methods of development of speed-strength abilities in other sports with the possibility of their application in judo are analyzed. A number of innovative methods of development of speed- strength abilities of wrestlers, which were proposed in the studies devoted to competitive activity in martial arts, including judo, are considered. Differences in the use of means for the development of speed- strength abilities of judo wrestlers are noted. The errors concerning individual psychological and pedagogical peculiarities of developing speed-strength abilities of judoists are revealed, which can become the subject of future scientific research. The results of this analytical review can be useful for specialists and coaches in the field of combat sports when conducting further experimental-theoretical research and training process with judoists.

ALGORITHM AND METHODOLOGY FOR EVALUATING RELIABILITY INDICATORS OF A LARGE GEAR WHEEL OF A TRACTION GEARBOX FOR AN ELECTRIC LOCOMOTIVE

This article presents experimental-theoretical research on strengthening the frames of VL-80 electric locomotive bogies during overhaul with service life extension in the conditions of UE "O'ztemiryo'lmashta'mir".

A new direction for calculating the strength of bent reinforced concrete elements along inclined sections with an example of calculating an experimental beam

The reliability of the operation of structures and structures as a whole Received: March 25, 2021 during their operation significantly depends on many factors that are not always Revised: May 27, 2021 fully taken into account by the calculation. One of the reasons for this may be a narrow Accepted: June 3, 2021 focus of many experimental researches, the results of which are taken for guidance in the development of the theory of calculation. Sometimes the calculation theories are not at all substantiated by experimental research. The experimental research methodology will give a positive effect for the development of a reliable theory for the calculation of bent reinforced concrete elements along inclined sections only when it combines the whole variety of influence of the main factors on the operation of the investigated elements, including the type of loads applied during testing - evenly distributed or focused, with deep analysis of the obtained results. In the proposed theory of strength calculation for inclined sections of bent reinforced concrete elements the relationship in the development of the stress-strain state under the action of a load both in normal and inclined sections to the longitudinal axis of the elements, up to the destruction of beams, obtained as a result of experimental theoretical research, is used. This ensures a close coincidence of the experimental and calculated data, increases the reliability, durability and economic efficiency of structures during their operation.

Experimental-theoretical method for studying the vehicle airbag modules functioning

Introduction (problem statement and relevance). The airbag belongs to the passive vehicle safety system (SRS - Supplementary Restraint System) and is the most important (together with the seat belt) restraint system that protects the driver and passengers in a collision with static or moving objects. The main task of the SRS is to minimize injuries to the driver and passengers and reduce deaths in various road traffic accidents. For the development and testing of modern high-tech airbag modules, it is necessary to have informative theoretical and experimental methods for studying the non-stationary processes of their functioning.The purpose of the study was to develop an experimental-theoretical research method based on modern highly informative tools of experimental physics of fast processes and numerical methods for continuous media dynamics.Methodology and research methods. To study the functioning dynamics of vehicle airbag modules, an experimental method for determining the kinematic and acoustic parameters has been developed and implemented, and a mathematical model of an airbag functioning process has been formulated and implemented in the LS-DYNA environment with the help of corpuscular particles method.Scientific novelty and results. The created experimental-theoretical method allowed both to simulate the functioning processes of the developed and tested airbag modules, and to carry out field tests of these modules. In addition, the experiment made it possible to carry out a detailed verification of the numerical method for calculating the airbag operation, on the basis of which it was also possible to perform numerical calculations interaction of the airbag and an anthropometric dummy model.Practical significance. The developed method for studying the processes of airbag modules functioning is an important and necessary component of creating a scientific, technical and experimental base for the development and production of passive safety systems.

STUDY OF THE HEAT-CARRYING FLUID TEMPERATURE INFLUENCE IN THE HEAT SUPPLY SYSTEM ON THE INDOOR AIR TEMPERATURE

This article presents a brief history of the country’s heat supply system development. The types of heat supply systems are considered, their brief characteristics are given. Methods for determining the heat load for household needs (heating and hot water supply) of urban residents are presented. The study of the coolant temperature influence on the air temperature in the room was carried out. The study used an experimental-theoretical research method. As a part of the experimental study, the data of temperature measurements in one of the heating points in Tyumen were requested. Within the framework of a theoretical study, the air temperature in a living room was calculated, depending on the coolant temperature according to the schedule of the CHPP and according to the supply in the supply heat pipe. In carrying out the theoretical study, standard methods were used for carrying out thermal calculations of heat supply systems, statistical research methods, as well as standard computer programs. The need to regulate heat energy is determined and the types of regulation are considered. The analysis of the adopted temperature schedule of the CHPP was carried out and a comparison was made with the calculated temperature schedule. The solution of the equation for determining the air temperature in the room is given. The air temperature in the room depends simultaneously on two factors: the temperature of the heating medium and the temperature of the outside air. As a result of the study, the presence of a discrepancy between the temperatures of the network water supplied to consumers and the created air temperature in residential premises was determined. The intersection point of the calculated temperature schedule and the CHP schedule was determined. The necessity of observing the calculated temperature schedule of the central quality regulation has been substantiated. The necessity of heat supply at a constant flow rate of the heat carrier has also been substantiated.

Experimental-theoretical research of ir heating influence on main properties of hydrated cementitious systems

Проведенные в работе как теоретические, так и практические исследования выявили преимущество предлагаемого способа тепловой обработки и показали возможности улучшения структурных характеристик бетона при тепловой обработке в среде с пониженной влажностью (γ = 5–10%) при условии покрытия открытых поверхностей бетона пленкообразующими составами и уменьшения напряженного состояния при тепло- и массообменных процессах по сравнению с тепловой обработкой в среде влажного насыщенного пара. Это обусловлено двумя обстоятельствами. Во-первых, при таком способе тепловой обработки возникают меньшие, чем при пропаривании, и противоположно направленные градиенты температуры и влажности, а во-вторых, возможное частичное испарение воды затворения в начальный период способствует некоторому уплотнению твердеющей системы и ускоряет образование искусственного камня. Физико-механические свойства бетона, прошедшего тепловую обработку по предлагаемому режиму, приближаются к свойствам искусственного камня нормального твердения. Показана возможность применения данного способа тепловой обработки для изделий с большим модулем открытой поверхности и низким начальным влагосодержанием, а также с повышенными требованиями по долговечности.

Development of a promising system for diagnosing the frogs of railroad switches using the transverse profile measurement method

We have developed a system for diagnosing the frogs of railroad switches, based on the application of modern microcontrollers of the type ESP with high technical characteristics and the simultaneous use of the information technology IoT (Internet of Things). The proposed system has advantages over mechanical systems in terms of the accuracy of data, their operational processing and submission to user in order to analyze technical condition of frogs at railroad switches. The results of measuring the transverse profile of frogs at railroad switches make it possible to take scientifically-substantiated decisions regarding the need for recovery repair of frogs by the method of surfacing and for control over gradual decrease in their carrying capacity, for establishing their actual technical condition and residual resource.We carried out experimental-theoretical research into longitudinal profile of frogs at railroad switches laid on the reinforced concrete bars. It was established as a result that after passing 50–65 million tons of cargo (that corresponds to the medium degree of wear) the trajectory takes the shape of a bump. We observe sharp hollows on the reinforced concrete base in the zone where a wheel rolls from a rail wing onto the core, characterized by significant total inclination. Subsequently, when the passed cargo increases, the number of sinusoidal irregularities grows. At wear close to maximal (80–95 million tons passed), the percentage of unfavorable trajectories (sinusoidal and hollows) grows; at low wear, they make up 49.8 %, at a wear of 5–6 mm and larger – 88.3 %. Sometimes there is a transformation of the sinusoidal irregularities into the wave-shaped ones.We have established characteristic motion trajectories of the center of mass of the wheel over the frog depending on the wear of rail wings and the core of a frog and the passed cargo. A mathematical model was constructed for predicting the wear of frog profile depending on the total weight of passed cargo.

Experimental Investigation of Compressed Thin-Walled Steel Members

The paper presents fundamental information about realized experimental-theoretical research to determinate the load-carrying capacities for thin-walled compressed steel members with quasi-homogenous and hybrid cross-sections. The webs of such members are stressed in the elastic-plastic region. This continuous research joins on previous research of the first author of the paper. The aim of this research is to investigate and analyse the elastic-plastic post-critical behaviour of thin web and its interaction with flanges. The experimental program, test members and their geometrical parameters and material properties are evident from table 1 and table 2 as well as from figure 1 and figure 2. The test arrangement and failures of the test members are illustrated on Figures 3, 4 and 5. Some partial results are presented in Table 3 of the paper, too.

Experimental-Theoretical Research of Mechanical Properties of Perforated Composite Sandwich Panels

This work is devoted to experimental-theoretical analysis of mechanical properties of sandwich panels made of fibrous polymer composite materials. The structures with tubular core were considered. Numerical simulations of the mechanical behaviour and tensile testing of full-scale samples of sandwich panels were done. The analysis of influence of perforation on mechanical properties of fiberglass laminates and sandwich panels was alsoperformed.

Development of Next Generation Heavy Duty Bus Fuel Cells with Enhanced Durability

The large-scale commercialization of durable and cost-competitive Polymer Electrolyte Fuel Cell (PEFC) technology for automotive applications still faces significant challenges. Fuel cell manufacturers need to develop low cost materials and fabrication approaches that surpass current levels of performance and durability. With funding from Ballard Power Systems and Automotive Partnership Canada, the present three-year project is dedicated to research and product development of next generation PEFC stack technology for transit buses [1]. The central objective is to advance the fundamental understanding of membrane degradation mechanisms and failure modes under drive cycles and conditions that are typical of heavy duty vehicle operation, and to leverage this knowledge to develop enhanced durability solutions.The project involves a cohesive research team from Ballard Power Systems, Simon Fraser University, and University of Victoria, with complementary and multi-disciplinary expertise in fuel cell science and technology, materials design and fabrication, multi-scale modeling, system design and engineering, as well as system controls and diagnostics. A comprehensive experimental-theoretical research approach is pursued that ranges from fundamental theory to empirical analysis, with close university-industry collaboration. For validation purposes, the research benefits from extensive real-time field data and field operated material samples extracted from the Whistler, British Columbia fuel cell bus fleet. The results obtained to date have enabled substantial improvements in membrane stability under bus conditions (based on laboratory testing) and enhanced the ability to accurately predict the fuel cell stack lifetime over several years of on-road transit service. This understanding will guide the development of the next generation of heavy duty fuel cell modules that reduce both capital cost and operating costs of fuel cell buses, making them commercially competitive with diesel hybrid buses on a lifecycle basis.

Compressed Thin-Walled Cold-Formed Steel Members with Closed Cross-Sections

The paper presents fundamental information about experimental-theoretical research oriented to determinate the resistance of thin-walled compressed steel members. The investigated members had closed cross-sections made from homogeneous materials. The theoretical analysis in this research is oriented to determinate the resistance of mentioned members according to relevant standards, while the experimental investigation is to verify the theoretical results and to investigate the behavior of mentioned members during the loading process.

Experiments and Simulations of Laminar Forced Convection With Water–Alumina Nanofluids in Circular Tubes

This work reports fundamental experimental-theoretical research related to heat transfer enhancement in laminar channel flow with nanofluids, which are essentially modifications of the base fluid with the dispersion of metal oxide nanoparticles. The nanofluids were synthesized by a two-step approach, using a dispersant and an ultrasound probe or a ball mill for alumina nanoparticles dispersion within the aqueous media. The theoretical work involves the proposition of an extension of the thermally developing flow model that accounts for the temperature variation of all the thermophysical properties, including viscosity and the consequent variation of the velocity profiles along the thermal entry region. The simulation was performed by making use of mixed symbolic-numerical computation on the Mathematica 7.0 platform and a hybrid numerical-analytical methodology (generalized integral transform technique, GITT) in accurately handling the governing partial differential equations for the heat and fluid flow problem formulation with temperature dependency in the thermophysical properties. Experimental work was also undertaken based on a thermohydraulic circuit built for this purpose, and sample results are presented to verify the proposed model. The aim is to confirm that both the constant properties and temperature-dependent properties models, besides available correlations previously established for ordinary fluids, provide adequate prediction of the heat transfer enhancement observed in laminar forced convection with such nanofluids and within the experimented Reynolds number range.