Study On Analytical Method And Structural Optimization Of Semi-integral Bus Body

There are three kinds of bus body structures: monocoque body, semi-integral body and body chassis frame construction. The semi-integral body is still best-selling. So, it's significant to study the structure type and analysis method of semi-integral bus.First, this paper makes a discussion about production procession of semi-load bus skeleton and the traditional bus analytical method in details. The semi-load bus structure contains a separate frame. Usually, the bus skeleton is produced in the follow orders: first, form a bus frame, then, install engine and other components to the frame, as a result of the gravity of these components, the frame becomes deformed, then, piece the other sub-assembles together to the frame in case of the suspension support, at last, fix air conditioner, seats and other accessories to the bus skeleton. Through the bus production process, it will be found that when the semi-load bus is in stationary state, loads of engine and other components fixed on the frame will be borne by the bus frame only, while bus is in statement of bumpiness, the loads will be borne by both bus frame and body structure. Other loads, such as accessories installed on the bus skeleton, passengers and luggage will be borne by bus frame and body structure in both stationary and bumpiness statement. The traditional bus analytical method neglects the deformation of bus frame during production procession. This paper proposes a new method to analyze the structure stress based on the stackable of liner system. To divide the bus structure analysis in two parts: bus frame and whole bus skeleton. To acquire the final bus frame stress by making a staking between the two analysis results of the bus frame stress. The final bus body stress is just the second analysis of the bus skeleton. Make a comparison between the two kinds of analysis methods, to find the difference of the methods and verify that the traditional analysis increases the bus body bearing capacity and reduce the bus frame bearing capacity. The analytical results of the new method would be more accuracy to guide the design and improvement of the integer bus.The bus skeleton is a hyper-static structure with the slender bars pieced together. The calculation theory of bus flexure stiffness is based on the bending theory of uniform beams. This paper does some researches on the calculation of bus flexure stiffness, and found that some factors make the calculation results discrete. This paper calculates the stiffness for more times and obtains a group date of the bus flexure stiffness and filters out the data which is discrete far away from normal, then calculates the Pearson statistic of the date and adopts chi-square test to verify that the data is in accordance with normal distribution, then chooses the sample mean of the data to be the bus flexure stiffness. Using this method to calculate the stiffness will reduce the impact of the factors during the calculation, and the result will be more affordable.To study the situation of the bars, the basic unit of the bus skeleton, is an effective way to design the structure. Sometimes, the analysis results would show that some local structures contain high-stress elements, in order to reduce the stress level, the traditional way is to increase the bar section size or thickness. In this way, the bus would be much heavier and sometimes it would not live a good result. This paper proposes an optimal design based on the analysis of the force in bars. The objective of this method is to minimize the non-axial bending force. As the current analysis software could not change the special structure to obtain a better form of the structure, the artificial changes would work well. Therefore, this paper proposes a method that: to analyze the internal force components, the stress components and the load-carrying path of the local structure first, and to analyze the relationship between the internal force and the stress to find out the reasons of the non-axial bending high-stress, at last, to take some measures to change the structure and reduce the stress level.The semi-load bus frame deformation during the production procession affects the bus performance. In order to reduce the negative affect, this paper proposes a modular design method to design the semi-load bus skeleton based on the three-section semi-load bus. The modular is to divide the chassis-frame into three parts, front and rear parts with the engine and other frame components, the middle part would be pieced together with the bus body to form a body skeleton, then, choose a reasonable support to the front and rear parts, join the body skeleton with the front and rear parts with some transition structures, at last, release the front and rear part support, the bus will support by the suspension system so that the engine and other components installed on the frame will be bear by both bus body and bus frame. This paper optimizes a semi-load bus structure with the modular design method, and analyzes the new bus structure. The analysis results of the new structure show good performance and reduce about 260 kg of the bus skeleton.