Випуск 55

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Application of the partial accelerations method in large-scale modeling of mechanical systems
(Харківський національний автомобільно-дорожній університет, 2024) Bogomolov, V.; Podrigalo, M.; Shein, V.; Baitsur, M.; Богомолов, В. О.; Подригало, М. А.; Шеїн, В. С.; Байцур, М. В.
Problem. Modern trends in the design of mechanical systems require the application of efficient methods to reduce time and resource expenditures during the development and testing of new structures. Large-scale modeling serves as a critical tool for verifying theoretical principles, evaluating the safety, and assessing the functionality of mechanical systems at early design stages. However, the complexity of dynamic models that describe the behavior of mobile machines in a scaled format necessitates the development of approaches to simplify such models. One promising approach is the method of partial accelerations, which enables mathematical and computational optimization of modeling processes. Purpose. The purpose of this study is to improve large-scale modeling methods by employing the method of partial accelerations in the study of mobile machine dynamics. Methodology. The research is based on the principle of superposition in mechanics, which enables the replacement of classical dynamic equations with equations of partial accelerations in a homogeneous vector space. This approach significantly simplifies the mathematical representation of system dynamics. Results. It has been established that the acceleration scale for mechanical systems operating within Earth’s gravitational field is always equal to unity, simplifying the process of determining the scaling factors for other physical quantities. The study proposes equations for partial accelerations that provide an accurate representation of the kinematics of both prototype and scaled models of mobile machines. Furthermore, the application of the multi-component complex motion model demonstrated its ability to evaluate dynamic deviations in mobile machines and account for the effects of active and reactive forces. Originality. The proposed method of partial accelerations introduces a novel approach to large-scale modeling of mechanical systems. By operating within a homogeneous vector space of accelerations, this method eliminates the need for inertial forces, reducing the complexity of mathematical models and enhancing the accuracy of predicting system dynamic behavior. Practical meaning. The method of partial accelerations can be applied in the following areas: designing mobile machines, including vehicles and planetary rovers; optimizing dynamic tests using accelerometers; modeling the energy efficiency of vehicles under steady and unsteady motion; enhancing scaled models for safety and maneuverability analyses.
Cycle mechanical coefficient of useful effect of motor-transmission installations of transportation and tractor vehicles
(Харківський національний автомобільно-дорожній університет, 2024) Podrigalo, M.; Podrigalo, N.; Vakhniuk, S.; Bisha, V.; Подригало, М. А.; Подригало, Н. М.; Вахнюк, С. А.; Біша, В. М.
Problem. When determining the efficiency coefficient of the motor-transmission systems of cars and tractors, it is necessary to consider not only the losses due to viscous and dry friction but also the losses caused by the circulation of potential and kinetic energy within the transmission. These losses result from the use of typical internal combustion engines in motor-transmission systems. Currently, existing studies do not take into account the dynamic cyclic energy losses in the transmission, which prevents an accurate assessment of the cyclic efficiency coefficient. Purpose. The purpose is to determine the cyclic efficiency coefficient of motor-transmission systems with internal combustion engines, taking into account the cyclic dynamic efficiency coefficient of the transmission in vehicles equipped with internal combustion engines. Methodology. The approaches adopted in this work to achieve the stated goal are based on the theoretical foundations for determining the dynamic efficiency coefficient, the work balance in the motor-transmission system of a car (or tractor) over one oscillation period of the indicator torque and the angular velocities of the engine's crankshaft during one oscillation period of its torque. Results. The cyclic mechanical efficiency coefficient of motor-transmission systems in wheeled machines has been determined, accounting for the losses associated with the acceleration of moving masses and the torque irregularities inherent to internal combustion engines. A relationship has been established in which the cyclic coefficients of dynamic and elastic losses are equal to zero when the torque irregularity coefficient is zero, a characteristic typical of electric motors. Originality. The results of the study provide a general understanding of the proportionality of the cyclic dynamic coefficient of mechanical losses in the transmission to the torque irregularity coefficient and the difference between the squares of the circular frequencies of torque oscillations and the natural (free) oscillations of the transmission input shaft. Practical meaning. The obtained results can be recommended for identifying frequency coincidences that lead to resonance, where the cyclic coefficients of elastic and dynamic losses increase sharply.

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