International Journal of Aerospace and Lightweight Structures 2011 1 2

doi: 10.3850/S2010428611000158

Knockdown Factor based on Imperfection Sensitivity Analysis for Stiffened Shells

Bo Wang^a, Peng Hao, Kai-Fan Du and Gang Li State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Dalian University of Technology, No.2 Linggong Road, Ganjingzi District, Dalian, 116024, China. ^awangbo@dlut.edu.cn

ABSTRACT

Imperfection sensitivities of stiffened shells are investigated in this study. A framework of obtaining rational knockdown factors (KDF) for stiffened shells is proposed based on imperfection sensitivity analysis, which is adaptive and less conservative compared to traditional KDF. Three types of imperfection including first and mixed eigenmode shape, sine wavy shape are considered for an orthogrid stiffened shell. The results indicate that the stiffened shell shows varied sensitivities for different types of imperfection, and the KDF decreases then tends to a lower bound as the diameter of shell increases. Finally, three types of stiffened shell with different stiffened patterns are compared by the proposed approach. In practice, some other manufacturing-process-specific imperfection signatures also can be considered by the proposed approach. The results above indicate that the framework has the potential to provide less conservative KDF, further to enable reduction in conservatism and can translate into weight savings, which can be significant in the development of heavy-lift launch vehicle.

Keywords: Stiffened shell, Imperfection sensitivity, Knockdown factor.

---

Back to TOC

FULL TEXT(PDF)