Finite element analysis of a transit bus

Most of the bus safety standards in the USA are not applicable to cutaway buses for which a production process is split into two stages. First, the chassis and cab section are assembled by automobile manufactures. Then the vehicle is shipped to another company, where bus body and additional equipment are installed. Lack of strict structural standards for transit bus body builders stimulates the need for crashworthiness and safety evaluation for this category of vehicles. Such an assessment process is needed and important since transit buses are often used to transport disabled passengers. Although a full scale crash test is considered the most reliable source of information regarding structural integrity, crashworthiness and safety of motor vehicles, the high Cost Of Such tests and difficulties In collecting data result in an increasing interest in the analytical and computational methods, which allow for extensive safety studies once the finite element model is validated. This Study focused on a selected transit bus, the Ford Eldorado Aerotech 240. Due to the lack of design data the reverse engineering process was used to acquire the geometric data of the bus. The finite element (FE) model was developed based on the geometry obtained by disassembling and digitizing all major parts of the actual bus. The FE model consists of 73,600 finite elements, has 174 defined properties (groups of elements with the same features) and 23 material models. All parts are connected using different multi point constraints and special links with failure to model actual types of structural connections such as bolts and spot welds. LS-DYNA non-linear, explicit, 3-D, dynamic FE computer code was used to simulate behavior of the FE model under different impact scenarios, such as front impact and side impact of two buses at various velocities.