Abstract
This article presents further results of the research of effects of model defects on the local buckling of compressed stiffeners in nonlinear finite element (FE) analyses. The main outcomes are confirmation of trends for 10 sets of profile dimensions, final validations of various sets of FE simulations, and designs of practical types of defects with appropriate ratio values. A single node defect and then complex types of defects with alternating distributions of node shifts along one edge, two free flange edges, one flange surface and both flange surfaces are analyzed in this research project. First parts of this paper describe designed FE models with defects, their effects on simulation results, colored graphic visualizations with stress scales and determinations of the sudden failure of stability in the local mode. Then, particular results of FE analyses are validated by a comparison with the results of analytical methods of stability failure. Final detail comparisons of analytical and FE simulation results with data of experimental tests confirm predicted critical buckling forces. The validation of results and design parameters together with the knowledge of effects of model defects on buckling behaviors allows more accurate simulations of internal stiffeners of thin-walled semi-monocoque structures.
Highlights
Problems of effect of defects on buckling behaviors of semi-monocoque aircraft structures in advanced finite element analyses are at the forefront of many research institutions
The results of finite element (FE) analyses were compared with results of analytical methods of global, local and transition regions of the critical stability failures
The detected geometry values were in the required standard tolerances and these stiffener specimens represent the real quality of manufacturing
Summary
Problems of effect of defects on buckling behaviors of semi-monocoque aircraft structures in advanced finite element analyses are at the forefront of many research institutions. The knowledge of effects and appropriate values of defects is necessary for the proper determination of the total load capacity of complex semi-monocoque structures with the use of numeric simulations. This knowledge can be utilized for the following predictions of buckling failures, where accurate diagrams for a safe design are not available. The comprehensive reviews on stability behaviors of compressed stiffeners in aerospace structures are presented in Niu (1999), from which an analytical approach of determination of critical buckling forces was used. The study Chen (2014) of imperfection types confirmed
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