A vehicle body concept modeling approach using reduced models of beams, joints and panels

The necessity to reduce the time-to-market in car manufacturing industry and the requirement of improving various functional performance attributes (e.g. safety, strength and stiffness, noise and vibrations, ecological impact etc.) lead many researchers to develop predictive Computer-Aided Engineering (CAE) tools, that can be already used in the concept phase of vehicle development [1]. In the early phases of the design process, and so when exact geometrical information are not yet available, conventional software packages (CAD, BEM, FEM etc.) based on detailed geometry data of the vehicle are not directly applicable. Furthermore the calculations are time-consuming, which limits the feasibility of parametric design optimization. The present work proposes a methodology for the concept design of beam-like structures, joints and panels in a vehicle FE model, with the aim of enabling accurate NVH simulations of the Body in White (BIW) already in the initial phases of the vehicle design process. As such, it is an extension of the beam and joint concept modeling approach proposed by Mundo et al. [2], in which concept models of beams and joints are created, by means of a geometric analysis of beammember cross-sections and a static analysis of joints, respectively [3]. The main innovation in this paper is the inclusion of panels in the concept modeling procedure. That is, the concept panels are modeled by coarsening the original FE mesh, while preserving the characteristics of these parts in terms of basic geometric features, such as shape and curvature. This yields a complete body concept modeling approach, in which all constituent parts of the vehicle body (beams, joints and panels) can be included in the concept model. The proposed approach is illustrated by using an industrial case study, where simplified models of beams, joints and panels of the upper region of a vehicle’s BIW are created and validated through full vehicle FE static and dynamic analyses. In particular, the front-upper region of the vehicle has a significant influence on the full-vehicle behavior and it is therefore selected as target of the concept design. A group of 10 beam-like structures (partly labeled in Figure 1 as B1 .. B6) are replaced by equivalent simple beams whereas the four joints (partly labeled as J1 and J2) are replaced by static super-elements. Finally the 3 panels (windshield (P1), front (P2) and rear (P3) panels of the vehicle roof) are modeled with a coarse mesh, connected to the surrounding concept beams by means of rigid connections (see Figure 2). Figure 1: Original FE model of the vehicle body. Figure 2: Concept FE model of the vehicle body. In line with the standards used by automotive manufacturers, two static load-cases are defined and analyzed to assess the accuracy of the concept model. In particular the torsion and bending stiffness of the BIW are evaluated for the original model and for the concept model as well. The results of the simulations, reported in Table 1, show that both the bending and the torsion stiffness of the original