Nonlinear effects of bolted flange connections in aeroengine casing assemblies

Aeroengine manufacturers face fundamental limitations when correlating experimental dynamic analysis with finite element method models. The source of inconsistency between model predictions and experimental test data can be attributed to nonlinear behaviour at the bolted flange interface. The two main sources of nonlinearities in aeroengine casing assemblies are damping dissipation and the nonlinear effects of boundary conditions. In this research, a novel and robust analytical formulation is proposed for implementation in FE analysis that accurately captures and represents the nonlinear dynamic characteristics of bolted flange connections. The proposed nonlinear analytical lump model has demonstrated significant accuracy and precision in capturing the nonlinear dynamic characteristics of bolted flange connections with spigots under various loading conditions. The proposed model clearly represents and characterizes the nonlinear phenomena of peak amplitude damping and frequency shift. It is also computationally efficient, making the model feasible for implementation when performing nonlinear analyses of large structural assemblies such as full aeroengine models. Moreover, the proposed analytical lump model is universal, permitting its implementation in various structures with different material properties and geometries. The validity and accuracy of the proposed model has been verified using nonlinear experimental test data for an aeroengine casing assembly.