dynamic analysis of a modified truck chassis

the paper investigates into the vibrational characteristics of the truck chassis including the natural frequencies and mode shapes. truck chassis forms the structural backbone of a commercial vehicle. when the truck travels along the road, the truck chassis is excited by dynamic forces caused by the road roughness, engine, transmission and more. modal analysis using finite element method (fem) can be used to determine natural frequencies and mode shapes. in this study, the modal analysis has been accomplished by the commercial finite element packaged ansys. the model has been simulated with appropriate accuracy and with considering the effect of bolted and riveted joints. the chassis has been altered by some companies for using in municipal service (street sweepers) and it raises the question: are natural frequencies of the modified chassis in suitable range? after constructing finite element model of chassis and appropriate meshing with shell elements, model has been analyzed and first 6 frequencies that play important role in dynamic behavior of chassis, have been expanded. in addition, the relationship between natural frequencies and engine operating speed has been explained. the results show that the road excitation is the main disturbance to the truck chassis as the chassis natural frequencies lie within the road excitation frequency range. finally advantages of the modified chassis which leads to the increase of the natural frequencies and placing them in the appropriate range, has been discussed.