Sub-Structured Approach for Occupant Head Injury Simulation

The current conference paper presents the "Sub-structured" engineering work methodology for Interior Head Impact development and assessment, designed to: (a) improve Finite Element Analysis (FEA / CAE) turnaround; (b) reduce the number of computations, and (c) increase the level of accuracy on trim / Body in White (BIW) structure. The proposed methodological concept, already successfully implemented to ensure the Jaguar X-Type compliance with Interior Head Impact (FMVSS201) legislation, establishes that CAE studies are to be performed up-front to CAD and subsequently as a final check. These studies will allow the analyst to gain confidence in the test facilities, in the accuracy of the CAE computation and, finally, generate a set of guidelines to be used to lead the vehicle design.
Traditionally, the assessment of Interior Head Impact Development entails numerous design iterations prior to selection of and agreement on final form and materials. Currently, engineering companies tend to over-use Finite Element Analysis for each design Computer Aided Design (CAD) iteration. Meshing and analysing every iteration can be time inefficient and cumbersome, while CAE predictions are often performed following the completion of the design phase.
The proposed methodology involves splitting the structure into sub-models of assemblies to be locally analysed. These assemblies may comprise such components as pillar trims, seatbelt adjuster, seats, bumper beams and so on. Firstly, physical tests in a strictly controlled environment, using simple rolled sheet or already existing manufactured components, are to be performed to define the exact component behaviour. The proposed test set-up is comparable to a test scenario in the vehicle. Of utmost importance is the tuning of material properties, contact interfaces, interdependence with adjacent parts and so on. Secondly, a statistical analysis method is used to quantify the test repeatability. Finally, upon successful completion of the tests, follow-up statistical analyses are to be performed on the CAE simulation. These are aimed at quantifying the simulation and fine tuning the emergent computer model.
As demonstrated in the Jaguar implementation, the "sub-structured" approach enables its users to attain an in-depth knowledge at component level and, consequently, achieve project completion 'right first time'.