Damage Tolerance and Fail Safety of Welded Aircraft Wing Panels

Abstract

An investigation is presented on fatigue crack growth behavior and fail safety of integral stringer panels typified by welded aircraft fabrications. The stringer panel is made of aluminum alloy 2024-T351 and fabricated by the variable-polarity plasma-arc welding process. The sample simulates a part of the lower-wing skin structures. Based on the linear elastic fracture mechanics, numerical simulations are performed for two configurations, two-stringer and nine-stringer panels, and three damage scenarios, in which welding-induced longitudinal residual stresses are taken into account. A typical load spectrum for large transport aircraft is employed for the analysis. For the two-stringer panel life predictions have a reasonably good correlation with the test results. Based on this validation, large-scale nine-stringer panels with three manufacture options, that is, riveted, integrally machined, and welded integral, are simulated for a skin crack under a broken central stringer propagating to two-bay length. Useful comparisons are made among the three variants. Finally, remedies to improve damage tolerance and fail safety of integral stringer panels are explored. The incorporation of crack retarder straps bonded to the inner surface of an integral panel has greatly improved the fail safety behavior of the component with dramatically increased crack growth live. = geometrical average of two transverse shear stresses in adhesive τ u = shear strength allowable of adhesive τ x,i τ y,i = transverse shear stresses in adhesive

Fracture and damage mechanics modelling of thin-walled structures – An overview

“…Recently a new concept of using bonded structures to enhance the damage tolerance of aircraft structures ab initio has been introduced and studied [159][160][161]. The article by Zhang and Irving in this special issue [162] provides additional information on analysis approaches for damage tolerance assessments for structures with bonds or stiffeners.…”

Non-prismatic sub-stiffening for stiffened panel plates—Stability behaviour and performance gains

“…What is more, Bushnell and Rankin [3] demonstrated that including small sub-stiffeners between the conventional primary stiffeners 'can not only lead to an increased buckling resistance, but more importantly to a much more robust optimum in terms of stiffener pitch'. Additionally, the damage tolerance characteristics of stiffener panel structures may be improved by the addition of plate element features designed to retard fatigue crack growth [4][5][6][7]. Considering panel post-buckling, improved plate stability should translate into improved collapse performance.…”

Effect of Thermal Residual Stresses on Bonded Structures Containing Cold Expanded and Bolted Holes

“…Integrally machined processes produces a high scrap rate of expensive aluminium alloys which results in a high manufacturing cost. Structures produced by mechanical fastening have to rely on numerous riveted and bolted joints which are potential failure locations due to a higher stress concentration factor associated with fastener holes [1]. In order to improve the damage tolerance and avoid large penalising safety factors, selective reinforcement such as novel crack retarding features can be incorporated into critical locations within the structure.…”