Derivation of Knockdown Factors for Common Bulkhead Structures Considering Geometric Initial Imperfection and Heat Transfer Effects

The common bulkhead structure can be used to reduce the weight of the space launch vehicles. In this paper, the nonlinear postbuckling analyses are conducted to derive the buckling knockdown factor (KDF) for the common bulkhead structures considering geometric initial imperfection and thermal imperfection. A commercial finite element analysis program, ABAQUS, is used for modelings and numerical simulations. The single perturbation dimple approach (SPDA) is used to implement the geometric initial imperfection. The thermal imperfection is obtained from thermal–structural coupled analyses. The most conservative KDF in this work is 0.465 when both the geometric initial imperfection and the thermal imperfection are considered. This result is 132% higher than that of the NASA’s buckling design criteria (0.200). Therefore, the lightweight design of the space launch vehicles may be possible using the present buckling KDFs.