Combined approximation based numerical vibration correlation technique for axially loaded cylindrical shells

As a widely used non-destructive buckling experimental technique, the vibration correlation technique (VCT) is able to determine the buckling load without reaching the collapse point. Following the experimental procedure, the numerical implementation of VCT can be easily realized. That is to say, the numerical VCT (NVCT) can be used for predicting buckling load. In this paper, the derivation of NVCT formulas is firstly presented for cylindrical shells under axial compression load. Aiming at accelerating the repeated eigenvalue analysis in NVCT, the combined approximation (CA) method is combined with NVCT. Then, the computational procedure of CA-NVCT is provided. Aiming at the verification of the effectiveness of the CA-NVCT, three analysis examples are carried out including variable-stiffness composite cylindrical composite shell, isotropic cylindrical shell and composite cylindrical shell with various types of imperfections. Finally, an optimization design is carried out to improve the buckling load of a composite cylindrical shell against imperfections based on the CA-NVCT. In comparison to results obtained by buckling experiments and typical buckling numerical methods, the high prediction efficiency and accuracy of the CA-NVCT in buckling analysis and optimization are verified.