Перегляд за Автор "Saraiev, O. V."

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Application of logical methods in expert analysis of automotive engine failures in operation
(Харківський національний автомобільно-дорожній університет, 2023) Khrulev, A. E.; Saraiev, O. V.; Saraieva, I.; Хрулєв, О. Е.; Сараєв, О. В.; Сараєва, І. Ю.
It is known that the causes of failures in automotive engines can be determined based on existing experience in studying various engine malfunctions. However, an analysis of known methods for determining the causes of car engine failures shows that their use in practice, including in diagnosing the technical condition of engines, requires a lot of work and highly qualified personnel that in many cases is practically ineffective. Logical-probabilistic methods are also known, including those based on fault tree analysis. However, it is not possible to use such models and methods in searching for the c auses of engine failure. Goal. The purpose of the study is to create a methodology for determining the causes of faults and failures in engine operation, which can be applied with help of a logical way and applicable not only by the specialists with expert level, but also the wide qualification. Methodology. The solution to this problem was found in several stages. Initially, by structuring the symptoms, a fault tree was constructed that logically describes the cause-and-effect relationships between the failure event and the original damage that caused it. Data from expert studies of engine failures were used to construct the graph. This was done for each of the engine failure types selected for analysis. Next, a modified (inverted) fault tree was developed for a finite number of selected failure types. Results. Obtained logical graphs allow you to perform a simple logical analysis in the opposite direction from the generally accepted one, from the event of a system failure to the basic damage events that cause it. After obtaining logical graphs for each type of failure, a modified engine fault tree can be compiled, common to the considered types of failures. Originality. The proposed method was widely used previously in the study of reliability of various technical systems, however, this method for the first time has been proposed to determine the causes of engine failures. Practical value. As a result of using the proposed methodology in practice, it it became possible to determine the causes of failure in the engine with enough reliability for practice and minimal time expenditure.
The method of expert assessment of the technical condition of an automobile engine after overheating
(Харківський національний автомобільно-дорожній університет, 2021) Khrulev, A. E.; Saraiev, O. V.; Хрулєв, О. Е.; Сараєв, О. В.
Problem. For expert studies of the technical condition of a car, a difficult task is to determine the causes and development of malfunction of engine mechanisms and systems. The paper proposes a model of engine malfunction during overheating, including in emergency mode caused by rapid loss of coolant. It has been established that thermal damage to the cylinder head is possible within 10 seconds after the cooling failure. The piston heats up more slowly and can only be damaged in the upper part and for a much longer time. According to the results of the study, it was found that in the event of an emergency loss of coolant, the driver does not have the technical ability to see the temperature rise, which may be important when investigating the causes of engine malfunctions associated with overheating. Goal. The goal is to investigate and reproduce the model of engine failure after overheating. Methodology. The theoretical calculated data are confirmed by real experimental studies of engine overheating failures. Results. It was calculated by calculation that in the absence of coolant, the temperature sensor, if it is located on the outlet pipe of the cylinder head, will not increase the temperature until the engine fails. A certain definite character of malfunction of parts of engine mechanisms during its sudden overheating is shown. Originality. On the basis of the developed models, a methodology was drawn up and the calculation of the thermal state of engine parts after overheating was performed. Practical value. The research carried out and the computational models compiled allow the expert to make a more objective assessment of the development of the engine malfunction mechanism when it overheats during the operation of the car.