Extension of substructuring technique in the nonlinear domain

Conventional finite element models based on substructures allow only linear analysis. Some load-bearing structures such as energy absorbers and impact attenuators are designed to perform their useful functions in the nonlinear domain. Evaluating engineering design concepts of those structures objectively and with a certain rigour is challenging. Finite element analysis (FEA) as a potentially suitable tool for the evaluation typically is not computationally efficient and affordable in the conceptual design phase. An idea of extending the substructuring technique to be used for the concept evaluation by allowing substructures to exhibit a nonlinear response and use them in finite element models to reduce the computational cost is investigated in this chapter. For this reason, it was necessary to introduce a new algorithm capable of substructuring nonlinear structural models with sufficient accuracy. The main requirement for successful application of substructuring to this class of design problems is the definition of structural stiffness within an engineering design concept, which is, in fact, the minimal requirement for FEA functionality as well. In this work, the expansion of the substructuring technique beyond the linear response expectancy application is achieved by employing a scalar qualifier to economically modify original substructure matrix for substructures to exhibit a nonlinear response. This extension and integration of substructuring are crucial in allowing FEA to become more computationally efficient and affordable in the conceptual design phase. This chapter provides a comprehensive overview of the traditional substructuring process, followed by a detailed description of the developed method that extends substructures beyond the linearity domain. The implementation of the extended substructures within a commercial FEA code (ABAQUS) is then presented.