A bus is integral part of public transportation in both rural and urban areas. It is also used for scheduled transport, tourism, and school transport. Buses are the common mode of transport all over the world. The growth in economy, the electrification of public transport, demand in shared transport, etc., is leading to a surge in the demand for buses and accelerating the overall growth of the bus industry. With the increased number of buses, the issue of safety of passengers and the crew assumes special importance. The comfort of driver and passenger in the vehicle involves the vibration performance and therefore, the structural integrity of buses is critically important. Bus safety act depicts the safety and comfort of bus operations, management of safety risks, continuous improvement in bus safety management, public confidence in the safety of bus transport, appropriate stakeholder involvement and the existence of a safety culture among bus service providers. In order to provide buses with minimal vibration resistant superstructure, CMVR- Technical Standing Committee have framed requisite guidelines on Standardization of the Bus Body. AIS-052 (Rev.1): Code of Practice for Bus Body Design Approval, which is then amended as additional Requirements for Bus Construction named ‘Amend. No. 6 to AIS-153 (01/2020)’ to cater vibration requirements.
This paper includes the numerical simulation of vibration test of a full bus body according to AIS-153:2018, clause no.2.3.1 – evaluation of Lowest Natural Frequency of Bus. Standard simulation methodology for finite element model building and analysis to describe the real physical behavior of the vehicle in accordance with this regulation was the need of industry. This paper explains Bus FE modeling methodology for worst-case representation of bus structure for its global mode stiffness and vehicle gross weight. Representation of each of the vehicle aggregates for its mass or /and stiffness is explained. Post-processing approach to distinguish global modes from local modes is formulated. CAE methodology for Bus structural global modes is validated indirectly through historical multiple correlation data points of scaled down models like mini buses, vans, cars, etc. Physically measured Center of gravity of complete bus body in kerb weight condition is one of the parameters used for FE-Test correlation. Established simulation methodology is deployed as a reference framework for Bus industry to evaluate the natural frequency of complete bus body considering the regulatory requirements, evaluation criteria and detailed documentation as per guidelines mentioned in the code.