Analysis Of Mechanical Behavior Of ISOGRID Stiffened Shells

The stiffened shells are widely used in aerospace structures. The stiffening patterns can increase the mechanical properties of shells, such as resistanc of bending, torsion and stretching. In the past,±45°stiffened shells and 0-90°stiffening patterns were widely applied in aeropace industry. However, they are inherently four bar links prevented from collapsing by integral skin and as a result have little in-plane torsional resistance capability. A goal was to find a structural arrangement that negated the shortcomings of the±45°and 0-90°stiffening patterns without introducing other penalties such as increased weight. The concept that was found to be the most promising is isogrid stiffening pattern.The main contents are listed as follows:(1) Based on Kirchoff's theory, the radial displacement of rib and skin is assumed to be continuous. The lateral bending stiffness and interaction of ribs are ignored. The basic equation of isogrid stiffed shell, the stiffness coefficients of bending, torsion and stretching were obtained by orthotropic theory and discrete theory of stiffened shells. Some conclusions and approaches that are practical in engineering design are obtained.(2) The tests are carried out on isogrid stiffened shells. The buckling behavior of the stiffened shells is illustrated with analysis. Comparisons between the experiment results and numerical results show the validity of the theoretical analysis presented in this dissertation.(3) The global stability, local stability and inner pressure strength of isogrid stiffened shells are certified by finite element method (FEM). We can prove the fundamental assumptions and the methods of project are validated.(4) The project analysis software of isogrid stiffened shells is developed by c plus language.(5) The critical loads of AGS are obtained by means of generalized stiffness coefficient.