Implementation of automatic optimization on dynamic characteristics of large complex structures

Large structures such as automobile body-in-white, are generally complex systems welded together by hundreds of stamping sheets with different geometry shapes. Being influenced and controlled by lots of parameters, it is difficult to achieve the dynamic optimization automatically by commercial structural analysis software. To reduce the number of design variables, the sensitivity of both natural frequency and mode shape vector to component geometry parameters were derived respectively. Then combining analytical and numerical approach, the commercial finite element software was re-developed. By modifying the thickness parameters of a few components, both frequencies and mode shapes were optimized markedly. Three application examples on automobile body optimization show that the presented method is an effective way attaining automatic optimization of frequencies and mode shapes for large complex structures.