Stress Analysis Simulations of Welded and Bolted Joints Method for Full Steel and Composite-Steel Chassis Structure of Electric Low Floor Medium Bus

Abstract

Stress analysis of welded steel-to-steel, bolted steel-to-steel, and bolted composite-steel chassis in an electric low floor medium bus structure is presented in this paper. The analysis was carried out on the condition that is when the bus is full of load in idle/static. This condition reflects the situation of the vehicle in full load with passengers and components, which is important to be analyzed to anticipate the unwanted structural failure of the chassis. Finite Element Method (Harmonic response simulation) is used to investigate the structural behavior of both welded and bolted methods. Several parameters such as 2 Hertz for the maximum frequency, 5000 kg for the total vehicle weight, and the uniform distribution of load are used for this study to simulate the simplified, real application in the real world. The first comparison is between the welded and bolted steel-to-steel chassis which results in the bolted method has a lower stress value by the difference of 4.3 MPa in the joint section than the welded joint. This means that the bolted joint is more recommended than welded for the use as an electric low floor medium bus and has the potential to be optimized further. In terms of reducing the weight of the chassis structure, then lightweight material (carbon fiber composite) is used to replace the full steel chassis to be a composite-steel chassis. The use of this hybrid material depicts the stress value of 61.5 MPa in the joint area, this value is still far below the limit of carbon fiber that is 3200 MPa makes this bolted composite-steel is considerably safe in full load condition as an electric low floor medium bus structure. Using this hybrid bolted composite-steel chassis structure also reduces the total chassis weight by about 22.7 % compared to the full steel chassis structure, thus one could expect to extend the mileage of electric vehicles by more than 20 %