Problem. Checking the brake system of a vehicle is crucial in terms of assessing its operational safety, and performance indicators and permissible modes are determined by the state standards of Ukraine. However, there are challenges related to the accuracy and objectivity of evaluating the braking efficiency of a car. The coefficient of adhesion between the wheel and the road surface is the primary factor that significantly affects the braking dynamics of a vehicle. This coefficient constantly changes due to various factors such as road surface conditions, tire design and properties, tire effectiveness, and car speed. Assessing the impact of these factors on a car's braking performance is difficult. Goal. The aim of this study is to experimentally determine the influence of tire properties on vehicle braking efficiency by conducting a multifactorial experiment on cars of different brands with different types of tires. Methodology. The study employs the method of conducting braking tests under road conditions using the necessary equipment. Statistical data on braking efficiency parameters were collected from cars equipped with different tire brands. Experimental tests were conducted on Mazda 323F and Hyundai Elantra cars, using tires from various manufacturers such as Sava, Tigar, Nokian, and MICHELIN. The tests were performed on asphalt-concrete surfaces under dry and wet conditions, and the braking efficiency indicators were measured. Originality. The experiment revealed that the quality of the rubber used in car tires has a significant impact on their braking efficiency within a wide range. The deceleration of a category М1 vehicle can exceed the minimum requirements for braking efficiency, established by national and international standards, by 29-67%, depending on the tire brand. This research presents prospects for further development of experimental and statistical studies in this field, aiming to provide a better understanding of car braking efficiency parameters based on tire quality. Practical Value. The data obtained from this study are of practical importance for evaluating the effectiveness of car braking during expert investigations of traffic accidents. This enables experts to draw more objective conclusions about the accident process and determine the driver's ability to avoid such incidents.
Problem. The paper analyzes the possibility of applying various mathematical models and quality assessment criteria in accordance with the problems of modern car diagnostics. The most complex object of car diagnostics is considered - the internal combustion engine and its especially loaded elements, which are part of the cylinder-piston group. The criteria for evaluating the quality of diagnosis of the cylinder-piston group are proposed. The possibility of presenting quality indicators in a multidimensional space, in which each dimension corresponds to a certain group of properties, is shown. In order to provide a comprehensive assessment, a number of indicators of quality properties are described, which have a certain formalized interpretation and make it possible to obtain a more objective, informative and unambiguous diagnostic conclusion regarding the functioning of complex technical objects.. Methodology. Based on the analysis of various types of mathematical models of technical diagnostics of the car engine, the criteria for evaluating the quality of diagnostics of the cylinder-piston group have been revised and improved. Additional data for the formulation of quality assessment criteria are provided by the results of expert studies of the technical condition of engines with serious damage up to the point of inoperability. At the same time, it is important that the assessment criteria for different engine states may be different.. Originality. The document shows a wide range of properties for evaluating the quality of diagnostics of the cylinder-piston group of the engine. A method of comprehensive quality assessment is proposed. An assumption is made about the presentation of quality indicators in a multidimensional space, in which each dimension corresponds to a certain group of properties. Practical value. To improve the quality of diagnosis of the cylinder-piston group of the engine, a comprehensive assessment of the diagnosis quality has been developed and improved, taking into account the conduct of expert studies of severe engine damage.
Problem. The problem of expert assessment of damage to engine parts, especially its mechanisms, which work in conditions of malfunctions of the car is a difficult task. Such an assessment requires certain qualifications, special equipment, is quite expensive and is subjective. The use of mathematical models in conducting such research should improve the objectivity of the expert's opinion. To do this, the paper identifies mathematical models, which are the basis of an improved expert method for estimating engine damage. These models under certain conditions of application allow to solve the inverse problem of destruction of details of the engine mechanism. Previously, such models were used in the design of the engine in the absence of violations of the car. Modeling in the practice of expert research is designed to improve their informational and objective components in determining the causes of engine failures due to violations of the operating conditions of the car. Goal. The aim of the work is to use mathematical models in conducting expert studies of engine damage to improve the objectivity of the expert's opinion. Methodology. Methodical materials for determining the causes of engine failures are not enough to solve practical problems. In many cases, the search for the cause of the fault involves time-consuming work on the analysis of numerous possible causes, which is often subjective, highly dependent on the qualifications of the researcher and can lead to erroneous determination of the cause of the fault. Originality. The problem of correct and effective determination of the causes of malfunctions remains an urgent task at all stages of operation of engines. In expert practice, it is customary to use several methods, which include diagnostic, as well as methods based on the analysis of signs of damage to individual parts. Practical value. Serious development of numerical modeling methods used for ICE design tasks has had almost no effect on the methods of modeling various faults, insufficiently developed issues of applicability of known mathematical models to the problem of damage to parts and components of ICE. In fact, modeling methods are not used at all in expert tasks to determine the causes of faults.
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