Buckling strength analysis and effect of local welds in isogrid cylinder structure

Large cylindrical structures made of metallic isogrid reinforcement are
manufactured by welding of plastically formed panels. Isogrid structures can be
designed using an equivalent monocoque cylinder for compressive buckling mode.
However, the welding joints between panels cause discontinuities that make
different behavior with equivalent monocoque cylinder and cause reduced buckling
strength. In this study, a buckling strength analysis is performed, considering the
geometry of the weld joints, and the effect of the welding area on buckling
strength is evaluated. Since welding joints generally have higher stiffness and
relatively lower bending stiffness than isogrid reinforced areas, local reinforcement
around the weld joints can minimize strength reduction. A non-linear numerical
analysis is conducted by varying the weld joint dimensions, considering the
manufacturing process, to compare the trade-off between increased mass and
strength. Finally, effective reinforcement methods to enhance buckling strength are
studied.