Stress intensity factors for cracks in patched and orthogonally stiffened sheets
Stress intensity factors for cracks in patched and orthogonally stiffened sheets
A theoretical formulation is presented for determining stress intensity factors for cracks in an infinite orthogonally stiffened sheet, including the effects of rivet deflection, in-plane bending of stiffeners and remote biaxial loading. New results are obtained for the effects of biaxial stress on the stress intensity factor, rivet loads and maximum stiffener stress for an infinite sheet having equally spaced stiffeners along lines perpendicular to the crack. It is shown that the stress intensity factor is only affected by a remotely applied stress parallel to the crack when at least one of the stiffeners is broken or runs out. The Boundary Element Method is applied for the first time to the study of the effect of boundaries on stiffened structures. New results are obtained for the effect of the boundary of a rectangular sheet reinforced by a single stiffener which is centrally or asymmetrically located and loaded uniformly and uniaxially. The boundary of the rectangular sheet parallel to the stiffener is shown to considerably increase the stress intensity factor as the crack approaches the sides. The effects of circular and rectangular reinforcing patches over a crack in an infinite sheet are investigated using strip patches modelled as finite length stiffeners with zero and stresses. It is found that both circular and rectangular repair patches should be large enough to cover the crack, otherwise the crack will grow rapidly. It is also shown that attachment flexibility and patch stiffness can significantly affect crack growth. Comparison of theoretically and experimentally determined crack growth rates for the circular patch showed an improved correlation when finite width effects and adhesive flexibility are included, but for a more complete agreement it would be necessary to include debonding and out of plane bending effects. (D74039/87)
University of Southampton
1986
Dowrick, Graham
(1986)
Stress intensity factors for cracks in patched and orthogonally stiffened sheets.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
A theoretical formulation is presented for determining stress intensity factors for cracks in an infinite orthogonally stiffened sheet, including the effects of rivet deflection, in-plane bending of stiffeners and remote biaxial loading. New results are obtained for the effects of biaxial stress on the stress intensity factor, rivet loads and maximum stiffener stress for an infinite sheet having equally spaced stiffeners along lines perpendicular to the crack. It is shown that the stress intensity factor is only affected by a remotely applied stress parallel to the crack when at least one of the stiffeners is broken or runs out. The Boundary Element Method is applied for the first time to the study of the effect of boundaries on stiffened structures. New results are obtained for the effect of the boundary of a rectangular sheet reinforced by a single stiffener which is centrally or asymmetrically located and loaded uniformly and uniaxially. The boundary of the rectangular sheet parallel to the stiffener is shown to considerably increase the stress intensity factor as the crack approaches the sides. The effects of circular and rectangular reinforcing patches over a crack in an infinite sheet are investigated using strip patches modelled as finite length stiffeners with zero and stresses. It is found that both circular and rectangular repair patches should be large enough to cover the crack, otherwise the crack will grow rapidly. It is also shown that attachment flexibility and patch stiffness can significantly affect crack growth. Comparison of theoretically and experimentally determined crack growth rates for the circular patch showed an improved correlation when finite width effects and adhesive flexibility are included, but for a more complete agreement it would be necessary to include debonding and out of plane bending effects. (D74039/87)
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Published date: 1986
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Local EPrints ID: 461116
URI: http://eprints.soton.ac.uk/id/eprint/461116
PURE UUID: 81763ab9-da5b-401d-a2a1-fc1dcee790cb
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Date deposited: 04 Jul 2022 18:36
Last modified: 04 Jul 2022 18:36
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Author:
Graham Dowrick
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