PSI - Issue 37

Rogério Lopes et al. / Procedia Structural Integrity 37 (2022) 73–80 R. F. Lopes et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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vibrational modes (Fu and He 2001). Their identification is a very important procedure for a safe and efficient structural design, both for the bus body strength to dynamic loads and prediction of the structure to residual fatigue life and, not less important, the passengers ’ comfort when the vehicle is subjected to dynamic disturbances. This theme is unquestionably a constant up-to-date vector of investigation in seeking the excellence of bus body design for the safety and comfort. Gombor, (Gombor 2005), investigated the modal behavior of a bus body frame type structure for transient forces applied at the level of suspension resilient block mountings. Georgiou et al ., (Georgiou, Badarlis, and Natsiavas 2008), proposed a combined model to analyze the structural behavior, the lowest natural frequencies, only dependent of the suspension flexibility, had the bus body modelled as a rigid entity, where its kinematics involved large displacements and rotations, for frequencies in excess of = , then the structure was assumed as a flexible frame, presenting beam type modal displacements and in frequencies exceeding about = , there was a prominence of local bending modes of truss/beam members of the body frame, which non-linear behavior was due to axial force effects. This paper constitutes a further study of Lopes’s study (Lopes et al. 2021), in which they presents a study on a dynamic behavior of a bus length = . This bus intends to establish a new sustainable transport generation, where there are few studies of the dynamic behavior mainly focusing on the modal analysis. This paper will take advantage of previous analytical methods and further numerical results are determined in order to purpose a final summary. 1.1. Model definition of the bus In this work, a 12 − bus is studied, (Solaris). Fig. 1 demonstrates an overview of the vehicle´s geometry with its dimensions. A summary of the bus characteristics is reported in Table 1. It must be stated that the bus is considered as a block, in which the several components such as seats, glass, engine components amongst others are incorporated through equivalent mechanical characteristics. More details can be found in the previously published work, (Lopes et al. 2021).

Fig. 1. An overview on the geometrical dimensions of the studied bus, values are in mm.

Table 1. Characteristics of the studied bus.

Bus main dimensions 12.0 ( ) 2.7 ( ) 3.0 ( ) 10.5 ( ) 5.9 ( ) Suspension system

Battery pack 2.67 ( ) 1.72 ( ) 0.33 ( ) 3.50 ( ) -

Length Width Height Weight

Distance between axles

4.2 × 10 5 (N/m) 4.0 × 10 5 (Ns/m)

Air spring stiffness Damping coefficient

1.2. Analytical model The simplified modal analysis demands a realistically designed dynamic model working as a multibody interaction. More relevant vehicle body displacements are derived by the elastic behavior of the suspension interacting with road irregularities or maneuvers by driving. It includes three axes translations (over , , main inertial symmetry axes),