Model order reduction and dynamic characteristic analysis of the bolted flange structure with free-free boundaries

Abstract The problem of model order reduction and dynamic characteristic analysis of the bolted flange structure with free-free boundary conditions is studied by proposing a novel simplified modeling method. The proposed simplified modeling method is able to reduce the finite element model of the linear components through free-interface mode synthesis method and condense the number of degree-of-freedom of the joint interface through coordinate condensation, which can fix the model size not to increase with the number of bolts and greatly reduce the computational cost. Rigid-body mode elimination is also considered to further reduce the order of the integrated dynamic equation and avoid the problem of computational instability in the proposed simplified modeling method. An experimental bolted flange structure with free-free boundary conditions is built and the corresponding modal testing is carried out to verify the accuracy of the proposed simplified modeling method. Comparative results of modal testing and simulation indicate that gravity leads to unequal bending frequencies of the same order in X and Y directions, which also proves that the proposed simplified modeling method is able to analyze the dynamic characteristic of the bolted flange structure with free-free boundary conditions.