No abstract

In this paper we review different definitions of Modal Participation Factor (MPF) available in the literature and propose a simple classification and unified concept for their application with particular focus in aerospace engineering. A case study is presented to aid the reader understand under what conditions each definition of MPF applies, its physical interpretation and which definitions have the potential to act as response tracking mechanisms during design optimization.

No abstract

As an industrial practice, complex structures are analyzed under a large set of dynamic operating conditions from which design load cases are selected. During design optimization, response tracking mechanisms based on modal participation factors could lead to large computational savings. In this paper we review the use of static modal participation factors as an inexpensive method to approximate the modal response of a dynamic system and extend the analysis to estimate the peak modal response when the structure is subject to a shock or pulse disturbances. A case study is presented as a proof of concept where the derived approximate peak loads are also estimated.

The current state-of-the-art design optimization of airframes is tightly wounded to its loads analyses as the process is usually conducted employing a deterministic set of critical load cases. The sheer number of scenarios required to estimate the critical loading conditions prevent these two processes from integrating, obstructing the development of a Multidisciplinary Design Optimization (MDO) framework. In this thesis, the problem of high fidelity and efficient estimation of critical dynamic aeroelastic loads is addressed, as a first step, towards the development of an integrated MDO platform for airframes at preliminary and detailed design stages. The method is based on the Kriging metamodeling technique along with the Latin Hypercube scheme for initial sampling and the expected improvement function for subsequent selection of sample points, known formally as the Efficient Global Optimization (EGO) algorithm. Furthermore, different inexpensive metrics, based on the concept of modal contribution factors, are investigated to serve as indicators to determine if a substantial change in the loads has occurred during the design optimization cycle, triggering the requirement for the re-exploration of the loads design space. A case study is presented to evaluate the performance of the proposed methodology versus a full factorial search. A reduction of 84% was achieved in the total time of execution employing the proposed methodology.