Investigation of Vertical Stiffness of the Front Axle Air Springs for Passenger Bus by Experimental and Finite Element Analysis

Abstract

Air Springs have been used for years, especially in commercial vehicles and buses, to maintain the vehicle's height regardless of the load and increase vehicle comfort. It is complex to experimentally determine the changes (reaction force, extension, strain) caused by loading alone to fully interpret the damping ability of air springs under operating conditions. The air springs are exposed to tension and force in different directions as they are made of a rubber composite structure. Therefore, discussing the damping properties of air springs with only the experimental method is difficult. The study aims to obtain information about the damping behavior of the bellows produced from composite materials, such as bellows under static loads, using both experimental and finite element analysis models. The finite element model of the air springs was obtained by modeling the three parts that provide its integrity. The material definitions required for the composite structure were determined by experimental methods and entered into the FEA program. No material is defined for rigid body members. The results of unidirectional and multidirectional tensile tests performed in a laboratory environment were used for material properties. The characteristics of the air were also entered into the analysis software with the information taken from the literature. The analyzes were carried out in three steps inflating the bellows to the specified pressure values, vertical movement, and compression to the specified displacement value. In this study, it was seen that the cord fabrics in rubber composite structures were affected more by excessive tension than rubber material, and the deviation of the static stiffness value was approximately 5% between the experimental study and the analysis studies. Thanks to FEA studies, it has been determined that more results can be obtained regarding values such as regional stress, force, and displacement in the bellows.