MULTIBODY MODELLING OF A HEAVY DUTY TRUCK AND ANALYSIS OF THE EFFECT OF FRAME FLEXIBILITY ON VEHICLE DYNAMICS

This Master of Science Thesis is the result of an eight month internship in the CNH Industrial headquarter located in Turin, Italy. The main target of the work was the development of a multibody model of an on-road heavy commercial vehicle, i.e. Iveco Stralis model year 2019. The main programming environment used in this activity was MSC Adams/Car. The significance of a complete and updated multibody model is clear since it provides the starting point of several studies within the Engineering Office of the Company, for instance the handling and the comfort ones as well the extrapolation of the dynamic loads which work on the mechanical elements in order to compute their fatigue life. To achieve this goal, intermidiate steps are required, like the building of little subsystems which are finally assembled to generate the full vehicle. The most relevant innovations of this model compared to the previous ones is represented by the integration of some flexible bodies, such as the frame, and the use of a specific tool in order to model the leaf spring suspension. Normally, the validation of the model, thanks to the experimental data coming from on-road tests, should follow. Regretfully, it was not possible to carry out this step since Iveco Stralis my2019 is not in production phase yet. Thus, the focus of the activity was shifted on studying the influence of the flexible bodies in a multibody model which typically consists of rigid parts. This paper is made up of four main chapters. In the Introduction, an overview of CNH Industrial and Iveco is given; then, the attention is focused on the object of the activity, the Iveco Stralis my2019. In the first chapter Adams/Car Software is discussed as regards both the modelling and the solving phase. The second one deals with the realization of the subsystems which compose the vehicle and the methodology employed. Afterwards, in the thrid chapter, the maneuvers according to ISO standard, performed both on the tractor and the complete vehicle, are described. Finally, in the fourth chater, the results are shown in order to get the difference between a fully rigid heavy vehicle model and a partially flexible one. Besides Adams/Car, other softwares have been needed: Altair Hypermesh, MSC Nastran and MSC Adams/View were used to create the flexible bodies; the 3D starting model was available in Dassault Catia while Siemens Team Center was used like 2D drawings database; Matlab was chosen as the post-processing environment.