Прогнозування довговічності лонжеронів каркасу основи автобуса в проблемних місцях

Abstract

The paper presents the results of assessing the durability of the base of the body frame in problem areas. The results were obtained by modeling in the environment of Solidworks 2018 and in the analysis of damage to the bodies of public transport bus bodies on the basis of long-term operation according to the operating organizations. It is established that such damages include corrosion and fatigue damage of the base frame and other elements of the body frame. Based on the analysis of the activities of operating organizations, it is established that the bus is undergoing repairs in case of destruction of the base, as further operation is impossible. It is established that the main problem that makes it impossible to operate the bus is structural corrosion in combination with the accumulation of fatigue damage under the action of alternating cyclic loads. The reasons influencing the nature of damages and speed of their formation are revealed: untimely renewal of corrosion protection and lack of processing of hidden cavities, roads of low quality and high speeds of movement on these roads, periodic overloads over admissible size. Damage to the base frame, in most cases, occurs near the mounting elements of the suspension and in the places of the floor difference (especially in buses of the type «low-entry» with low-floor storage pads in the rear of the bus). Large loads on the rear platform of domestically produced buses «Ataman» A092H6 during rush hour, given the fact that the rear platform seats only for standing passengers, lead to the formation of main fatigue cracks. As a result of such operation on low-quality roads, fatigue failure occurs after approximately 210 thousand km, with a service life of 2 years. It is substantiated that to predict the formation of fatigue cracks and, accordingly, to prevent their formation, the results obtained in the conditions of unstable movement in the conditions of real operation are not enough. The simulation results are presented, which show the number of cycles to failure and a comparison with the realities of operation, based on which the formation of foci of fatigue cracks is explained and recommendations for preventing the development of corrosion cracking are developed.