Buckling analysis for an integrally stiffened panel structure with a friction stir weld

The effect of an friction stir weld (FSW) on the buckling behavior of an integrally stiffened panel (ISP) structure was investigated. For proper consideration of the buckling modes, the Riks method based on geometric imperfection was introduced. The Ramberg–Osgood deformation plasticity model was used for the elasto-plastic material behavior. A basic buckling benchmark test with a simple square plate was performed to verify the effect of the element type, Ramberg–Osgood model and the Riks method on the critical buckling load. Buckling analyses with two different sectional shapes were conducted corresponding to 400 and 600 kN buckling loads. After confirming that the predicted results without FSW were in excellent agreement with known analytical solutions, finite element (FE) analyses for 2- and 3-stiffener ISP sections joined by FSW were performed. The simulated results with and without FSW were compared to each other. The presence of the weld reduced the maximum buckling load from 3% to 10% depending on the sectional shape as a result of the reduction in material strength in the weld zone. The reduction in buckling load was greater for the 2-stiffener ISP section than for the 3-stiffener ISP configuration, due to the closer spacing of the welds. For both ISP configurations, the percentage decrease in the buckling load for the higher load case (600 kN) was less than that for the lower load case (400 kN).