PSI - Issue 37

Rogério Lopes et al. / Procedia Structural Integrity 37 (2022) 81–88 R. F. Lopes et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 6. Displacement amplitude distribution obtained on: a) 1 st , b) 2 nd , c) 3 rd , d) 4 th , e) 5 th , f) 6 th , g) 7 th and h) 8 th natural frequency for the full capacity, values are in [mm]. 4. Conclusions An articulated vehicle is a dynamic system of masses connected solely by a joint, in which the relative rotation motion between the tractor and the trailer module may be uncontrolled. However, this issue has been overcome in the recent manufacturing technology by implementation of viscous dampers (oil-pneumatic actuators with oscillation control). Such developments provide an excellent contribution to guarantee the stability between two bodies (tractor and trailer) when transient lateral forces (e.g. wind gusts) act laterally only on one of the axles. The expected effect on a vehicle without damping on the trailer hinge would be a loss of stability with an uncontrollable oscillation effect between the tractor and the trailer. In this paper, an articulated bus structure was studied considering an oversimplification of the real model. With regard to the suspension, only two connections were considered, one representing the wheel-to-ground contact and another to the wheel/body through a pneumatic suspension arrangement. Concerning the connection between both modules, it was streamlined as a damped component. The obtained results confirm that oil-pneumatic actuators are extremely useful in controlling the oscillation verified in the trailer hinge under lateral disturbances. The vibrations generated by the movement of the bus, such as track irregularities, can cause motion amplification. If the frequencies, caused by external factors, coincide with natural frequencies, it would endanger to the bus body integrity and passengers ’ safety. Albeit the bus passenger capacity directly increases the vehicle weight, reflecting a significant decreasing trend on natural frequencies, such behavior can result in passengers’ injury, given by potentially large amplitudes for the frequencies oscillations due to unexpected loads affecting the bus. Acknowledgements Authors gratefully acknowledge the funding of Project POCI-01-0247-FEDER-039711- CRASH – Novas soluções tecnológicas de segurança passiva para autocarros, cofinanced by União Europeia, through Fundo Europeu de Desenvolvimento Regional (FEDER). Behzad V. Farahani sincerely acknowledges the funding received from Ministério da Educação e Ciência, Fundação para a Ciência e a Tecnologia (Portugal), under grant PTDC/EME-EME/29339/20147.