Numerical investigation of buckling behaviour of grid stiffened panel with opening during creep age forming

Abstract. This study focuses on the prediction of the formability of the integrally stiffened panels with opening due to buckling during the loading stage and heating stage of the creep age forming (CAF) process. The simplified model of integrally stiffened panels with opening was established to investigate the buckling behavior of the stiffened panel subjected to pure bending moment at room temperature and ageing temperature. The influence of the main geometrical parameters (stiffener thickness and stiffener height) on the critical buckling stress and critical buckling strain of the stiffened panel at the two temperatures was studied by finite element simulation. With the increase of the stiffener thickness and the decrease of the stiffener height, the critical buckling stress will increase to about 570 MPa at room temperature and 475 MPa at ageing temperature, which makes the formability limit increase correspondingly. When the stiffened panel is in the elastic region, the non-dimensional critical buckling coefficient is reduced by 20%, compared with the traditional stiffened panel. When the stiffened panel enters the plastic region, the critical buckling strain increases and the forming limit enhances accordingly. The research results offer a significant reference for the structural optimization design of the stiffened panel, presenting a simplified approach for studying other special shapes of stiffened panels, which is helpful to ensure that the workpiece will not be buckled during the forming process.