Mathematical Model of Forecasting Durability of Bus Bodies and Checking it for Adequacy
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Abstract
A mathematical model for predicting the durability of bus bodies has been developed. The model allows you to predict the resource of the bus body before the destruction of the elements of the frame framework. The example of the model of predicting the durability of the body of type «Low-entry» bus "Ataman" A092H6 is considered in the work. Factors affecting the durability of the body frame are used in the model: road micro-profile, passenger loading, speed and climate corrosion. The model is based on a system of differential equations describing the transmission of perturbations from the road micro-profile through the tires and suspension to the body frame elements. As a result of previous studies, the problem areas in the body frame elements were identified. Such places are subject to research during modeling. The model works as follows. First, the acceleration in the center of mass of the bus is determined. Then there is a given value of acceleration in cross section of the element under study. Multiplying the obtained acceleration by the given mass in the test section determines the effort. Knowing the cross-sectional area of the element being investigated, the voltage in that element is determined. The cross-sectional area of the body frame elements will be steadily reduced by corrosion. This dependence was obtained experimentally. It is established that the dynamics of reducing the thickness of the walls of the pipe frame will depend on the population of the city where the bus is operated. With the increase in the number of inhabitants, the intensity of corrosion will increase, which will cause a decrease in the thickness of the pipes. After determining the time diagram of the stresses in the element under study, the spectral density is determined, and then, according to the Rice formula, it is possible to determine the time before the fatigue of the element under study. Knowing the speed of movement, you can determine the mileage of the bus to the appearance of fatigue cracks, which determines its durability. The developed model is implemented in the Matlab 2017b software environment. The adequacy of the mathematical model was confirmed by road tests of the A092H6 bus, in which the stresses in the elements to be simulated were determined.
