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Hardware benchmarking of body overall stiffness and joint stiffness of the best-in-class competitive vehicles is a common practice in the automobile industry. However, this process does not provide design insights of competitive body structures, which relate stiffness performance to key architectural designs. To overcome this drawback, a CAD body-in-prime model of a competitive vehicle is developed using laser/optical scanning technology and a corresponding CAE model is built based on the CAD data. A deep-dive structural efficiency study is conducted using this model and “pros” and “cons” of the architectural design of each individual joint and each section of major load-carrying members of this body structure are identified. This analytical benchmarking (or reverse engineering) process enables a company to adopt best-in-class design practices and achieve competitive advantages in vehicle designs.

Joint stiffness is a major contributor to the vehicle body overall bending and torsional stiffness which in turn affects the vehicle NVH performance. Each joint consists of spot welds which function as load paths between adjacent sheet metal. Spot welds tend to lose structural integrity as a result of fatigue, loosening, aging, wear and corrosion of parts as a vehicle accumulates mileage. Experimental methods are used to identify potential degradation mechanisms associated with a spot weld. A CAE model which simulates a vehicle body joint generically is used to determine the effects of each individual degradation mode of a spot weld on joint stiffness. A real life B-pillar to roof joint CAE model of a production vehicle is then employed to examine the significance of weld distribution on joint stiffness degradation. The knowledge derived from this study can be used as a guidance in designing vehicle body structures with respect to spot weld distribution.

Squeak and rattle is one of the major concerns in vehicle design for customer satisfaction. Traditionally, squeak and rattle problems are found and fixed at a very late design stage due to lack of up-front CAE prevention and prediction tools. An earlier research work conducted at Ford reveals a correlation between the vehicle overall squeak and rattle performance and the diagonal distortions of body closure openings under a static torsional load. This finding makes it possible to assess squeak and rattle performance implications between different body designs using body-in-prime (B-I-P) and vehicle low frequency noise vibration and harshness (NVH) CAE models at a very early design stage. This paper presents an application of this squeak and rattle assessment method for a design feasibility study concerning a cab structure of a super duty truck for weight reduction using high strength steel and adhesive bonding.

Squeak and rattle is one of the major concerns in vehicle design for customer satisfaction. Traditionally squeak and rattle problems are found and fixed at a very late design stage due to lack of up-front CAE prevention and prediction tools. A research work at Ford reveals a correlation between the squeak and rattle performance and diagonal distortions at body closure openings and fastener accelerations in an instrument panel. These findings make it possible to assess squeak and rattle performance implications between different body designs using body-in-prime (B-I-P) and vehicle low frequency noise, vibration and harshness (NVH) CAE models at a very early design stage. This paper is concerned with applications of this squeak and rattle assessment method for up-front body designs prior to a prototype stage.

There are two distinct classes of body CAE models (detailed and concept models) that can be used to support vehicle body design and development. A detailed finite element model achieves computational accuracy by precisely simulating component geometries and assembly interfaces. On the other hand, a concept model simulates stiffness behavior of joints and major load-carrying members (e.g., pillars, rails, rockers, etc.) in a body structure. The former is quite useful for conducting trade-off studies when detailed design drawings become available. The latter is valuable for up-front design direction studies prior to detailed design evolution. In concept models, major load-carrying members are universally represented by cross sectional properties (e.g., area, moments of inertia and torsion constant). The key difference between various kinds of concept models is the representation of body joints.

Liftgate chucking is one of the major squeak and rattle concerns for vehicles with a large body closure opening in the liftgate area. High frequency chucking noise is generated as a result of the contact between the latch and striker of a liftgate. Traditionally, liftgate chucking problems (if present) are found and fixed by using a more robust latch/striker mechanism at a very late design stage that normally results in cost penalties for vehicle programs. Significant effort has been made at Ford in identifying and clarifying up-front drivers or body performance metrics that predominantly influence downstream squeak and rattle sensitivity. Two key body performance metrics (diagonal distortions at the liftgate opening and relative displacement between the latch and striker of a liftgate) are found to affect liftgate chucking sensitivity. The effects of body joint designs on liftgate chucking performance are discussed using these metrics in CAE analyses.