The aim of this thesis is to evaluate and develop different modelling tools which can be used in the vehicle crashworthiness design process. These tools will improve the understanding of the vehicle behaviour and thus improve the crashworthiness of the vehicle. The subject of the thesis is limited to early design stages of vehicles and vehicle components subjected to frontal impact.

The present study has demonstrated the utilization of concept models, sub-models, sensitivity analysis and structural optimization in the design process. The sensitivity analysis and structural optimization have been studied in details while the use of concept models and sub-models are only briefly presented.

The sensitivity analysis has been studied in Paper I. As a result it has been shown that the Response Surface Methodology (RSM) can be used with linear surface approximations to determine the sensitivity of different responses due to design parameter variation. Linear surface approximations are applicable if the normalized surface approximation error is less than 10%.

In Paper II, the efficient number of experimental points has been determined for the RSM application on crashworthiness problems. The D-optimality criterion is used as an experimental design method. A general recommendation is that 1.5 times the minimum number of experimental points should be used. A more specific recommendation is for linear surfaces 1.5, elliptic surfaces 2.2 and for quadratic surfaces 1.6 times the minimum number of experimental points.

In the final Paper III, it has been determined that the Space Mapping technique using surrogate models in combination with RSM is very efficient in optimization of crashworthiness and sheet metal forming problems. All examples converged to the correct optimum and the computing time has been decreased with a maximum of 63% relative to the traditional RSM optimization.