Analytical lump model for the nonlinear dynamic response of bolted flanges in aero-engine casings

Bolted flanges in aero-engine casings exhibit a nonlinear response when subjected to forced vibration. The current models for the structural dynamic analysis of bolted flanges are accurate, but they are cumbersome for the design of new structures. These models either require model updating from modal testing, or they require a large number of nonlinear elements. This study presents a new lump model that accounts for the nonlinear phenomena of partial clearance and friction, and has analytical parameters related to the flange geometry. The model was implemented in finite element analysis and compared with an experiment where a test structure is excited by an electromechanical shaker. The lump model predicts the structural response better than a traditional linear method; yet it does not require model updating, and it uses a very limited number of nonlinear elements. The model is therefore well suited for the early design phase of new aero-engine casings. This study supports the use of geometric lump models in the field of nonlinear structural dynamics.