Journal ArticleDOI
Worst Multiple Perturbation Load Approach of stiffened shells with and without cutouts for improved knockdown factors
TLDR
In this paper, an optimization framework of determining the worst realistic imperfections was proposed to study the reduction of the load-carrying capacity of unstiffened cylindrical shells.Abstract:
An optimization framework of determining the worst realistic imperfection was proposed by the present authors to study the reduction of the load-carrying capacity of unstiffened cylindrical shells. However, with regard to stiffened shells, especially when cutouts are included, the dimple combination pattern should be judged in a more rational manner. In this study, node coordinates are utilized to describe the position of each dimple-shape imperfection for Worst Multiple Perturbation Load Approach (WMPLA), which is an improvement of the MPLA using an optimization algorithm to find the application positions that will reduce the buckling load. Further, a novel method to determine the density of possible positions of dimple-shape imperfections is proposed based on eigenmode shape for stiffened shells without cutout. In addition, the effects of cutouts on the proposed method are investigated in detail. The effectiveness of the proposed method is demonstrated by comparison of several conventional methods to obtain improved knockdown factors (KDFs).read more
Citations
More filters
Journal ArticleDOI
An integrated framework of exact modeling, isogeometric analysis and optimization for variable-stiffness composite panels
TL;DR: An integrated framework of exact modeling, isogeometric analysis and optimization for variable-stiffness panels is developed for the global optimum, and the proposed method is able to provide a more efficient optimum design with significant less computational cost compared to other traditional methods.
Journal ArticleDOI
Hybrid Framework for Reliability-Based Design Optimization of Imperfect Stiffened Shells
TL;DR: In this article, a hybrid bi-stage framework for reliability-based design optimization of stiffened shells is presented to release the computational burden, where two main sources of uncertainties are considered: variations of material properties and geometric dimensions are described as random variables, while various forms of imperfections are covered by the single perturbation load approach.
Journal ArticleDOI
Efficient Optimization of Cylindrical Stiffened Shells with Reinforced Cutouts by Curvilinear Stiffeners
TL;DR: In this article, an efficient optimization framework of cylindrical stiffened shells with reinforced cutouts by curvilinear stiffeners is proposed, where the numerical implementation asymptotic homogenization method is used to smear out the stiffeners in the far field.
Journal ArticleDOI
Numerically and experimentally predicted knockdown factors for stiffened shells under axial compression
TL;DR: In this article, the imperfection sensitivity of a 4.5m-diam isogrid stiffened shell under axial compression is investigated, and the measured imperfection, NASA SP-8007 and several types of assumed imperfections, including eigenmode-shape imperfection and dimple shape imperfections are introduced into the FE model to predict the knockdown factors (KDFs), respectively.
Journal ArticleDOI
Robust knockdown factors for the design of axially loaded cylindrical and conical composite shells – Development and Validation
TL;DR: In this paper, perturbation approaches for the design of axially loaded cylindrical and conical shells are presented for a physical based estimation of the lower bound buckling load and are suitable for research and industrial applications.
References
More filters
Journal ArticleDOI
Multiquadric equations of topography and other irregular surfaces
TL;DR: In this paper, a method of representing irregular surfaces that involves the summation of equations of quadric surfaces having unknown coefficients is described, and procedures are given for solving multiquadric equations of topography that are based on coordinate data.
Journal ArticleDOI
Surrogate-based Analysis and Optimization
Nestor V. Queipo,Raphael T. Haftka,Wei Shyy,Tushar Goel,Rajkumar Vaidyanathan,P. Kevin Tucker +5 more
TL;DR: The multi-objective optimal design of a liquid rocket injector is presented to highlight the state of the art and to help guide future efforts.
Journal ArticleDOI
Comparative studies of metamodelling techniques under multiple modelling criteria
TL;DR: This paper systematically compare four popular metamodelling techniques – polynomial regression, multivariate adaptive regression splines, radial basis functions, and kriging – based on multiple performance criteria using fourteen test problems representing different classes of problems.
Buckling of Thin-Walled Circular Cylinders
TL;DR: In this article, the buckling of cylindrical shells under various types of static and dynamic loadings is discussed, and the procedures that yield estimates of static buckling loads considered to be conservative.
Journal ArticleDOI
Robust design of composite cylindrical shells under axial compression — Simulation and validation
TL;DR: In this article, a new deterministic approach is presented for determining the lower bound of the buckling load of thin-walled cylindrical composite shells, which is derived from phenomenological test data.