Model Reduction Of Head Impact Simulation On A Vehicle Bonnet

Research and Engineering Objective: To reduce the severity of injuries due to head impact on a vehicle bonnet, car manufacturers have introduced safety measures such as the pop-up bonnet concept. Performance assessment of such systems requires a large number of detailed impact simulations, which results in long computation time. The objective of this research is to reduce the computational burden by developing a reduced order model that meets the accuracy requirements for such a performance evaluation. Methodology: A model reduction technique, based on “Proper Orthogonal Decomposition”, has been applied by using only the results of a commercial Finite Element model for a bonnet of a production car. Special attention has been given to the analysis of information during the model reduction process to determine - at an early stage - the balance between required computation time, speed and accuracy of the resulting reduced model. Results: The performance of the proposed method has been evaluated. Bonnet deformation due to head impact is determined with more than 95% accuracy and computation thereof is approximately a factor of 1000 faster using the reduced order model. Limitations of this study: So far, only the deformation pattern of single type head impacts on a car bonnet were considered. A reduced model which includes more variables, such as acceleration and the head impact criterion, is currently being developed. What does the paper offer that is new in the field including in comparison to other work by the authors: A new approach has been developed to estimate the bonnet deformation by using only information from simulation results of neighbouring impact points. The deformation field is reconstructed by linearly combining the shape functions resulting from the POD analysis of these points. A ‘formula’ is determined which derives the weighting coefficients from a correlation between the deformation in the predefined impact points and the resulting deformation in the impact point for which the solution is required. Conclusions: It is possible to reduce the computation time of head to bonnet impact simulations by using reduced order models with predetermined accuracy. A speed improvement factor of more than 1000 has been achieved without compromising the accuracy.