Fatigue characteristics of joints with holes cold-expanded in a multi-layer stack

Mann, Jonathan; Sparrow, J. G.; Beaver, P. W.

doi:10.1016/0142-1123(89)90304-6

Cited by 8 publications

(3 citation statements)

References 6 publications

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“…During the SSCE process, the least amount of compressive residual stress occurs in the entry plane, the largest amount of compressive residual stress in the mid-thickness plane, and good compressive residual stress in the exit plane, as shown in Figure 15 , Figure 16 and Figure 17 . The result has been confirmed by several researchers that, with the increase in thickness, the compressive residual stress at the entrance plane decreases [ 40 , 41 , 42 , 43 ].…”

Section: Resultssupporting

confidence: 69%

Finite Element Analysis of Split Sleeve Cold Expansion Process on Multiple Hole Aluminum Alloy

et al. 2023

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Multiple cold expansion holes are widely used in connection areas of aircraft structures, in order to achieve uniform load transfer of the skin or connection parts. Split sleeve cold expansion (SSCE) is widely used to enhance the fatigue life of fastener holes by applying compressive residual stresses around the holes. In this study, the finite element method (FEM) was used to research the distribution and variation of residual stresses along the hole edges of 7075AA single-hole and multi-hole cold expansion (CE) specimens. Full-field strain measurements of single-hole and multi-hole specimens were performed using two-dimensional digital image correlation (DIC), and the residual stress and strain at the hole edge of the specimens measured by FEM and DIC were compared. FEM results shows that the maximum circumferential and radial residual stresses of three-hole specimens with three-hole spacing are increased by 5.37% and 31.53% compared with single-hole specimens. The maximum circumferential residual stress of three-hole specimens with four-hole spacing increases by 7.25% compared with a single hole, but the radial residual stress decreases by 12.98%. In addition, for three-hole specimens with hole spacing three times the hole diameter, the strengthening effect of SSCE in the order of middle hole, then left hole, and, finally, right hole is better than that of SSCE in the order of left to right hole. FEM and DIC full-field strain results are basically consistent.

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Section: Resultssupporting

confidence: 69%

Finite Element Analysis of Split Sleeve Cold Expansion Process on Multiple Hole Aluminum Alloy

et al. 2023

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“…Unfortunately, these investigators did not specify the exact locations of their stress measurements relative to the edge of the hole. Observations of out-of-plane displacements at distances less than about 3.5 mm from the hole [25], and variations in both the post cold-expansion diameter of the hole along its length (bellmouthing) [6,25,36,371 and the width of the remaining ridge in the hole attributable to the slit in the disposable sleeve, also indicate that the radial expansion of the hole is not uniform through the thickness, and tends to be smaller at the entry face than the exit face. The difference in the residual stresses at the exit face compared to the entry face may be manifest as a smaller radius of the compressive hoop stress maximum near the entry face, or lower compressive residual stresses near this face compared to the situation near the exit face.…”

Section: Discussionmentioning

confidence: 99%

Fatigue of Thick‐section Cold‐expanded Holes With and Without Cracks

Pell

Beaver

Mann

et al. 1989

Fatigue Fract Eng Mat Struct

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Fatigue tests under spectrum loading were conducted to evaluate hole cold-expansion in thick-section open-hole aluminium alloy specimens, some of which contained residual fatigue cracks before cold expansion. Cold expansion resulted in an increase in life by a factor of about 7. Small residual fatigue cracks did not inhibit the effectiveness of the cold-expansion process, indicating that it may not be essential to remove such cracks prior to hole cold-expansion. The increase in life is primarily associated with a reduced crack propagation rate compared with that for cracks from non-cold-expanded holes. Cold-expanded hole fractures displayed a marked disparity in crack depths adjacent to the two faces of the specimens. Considerable differences were evident in crack depths and fatigue crack areas at failure between cold-expanded and non-cold-expanded hole specimens. These findings have ramifications in the damage tolerance assessment of aircraft structures.

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“…It appears that fretting initiation of fatigue cracks may be the reason why the full benefit of cold expansion is not realised in multi-layer metal joints. Cold expansion is known [7] to produce permanent out-of-plane displacements at both mandrel entry and exit faces, even in a clamped multi-layer stack, and for each layer. These surface protrusions on the faying surfaces which, in extent, may persist some few millimetres from the hole edge, may then become sites of intense fretting under cyclic loading of the joint.…”

Section: Introductionmentioning

confidence: 99%

Extending the Fatigue Life of Multi‐layer Metal Joints

Finney

Evans

1995

Fatigue Fract Eng Mat Struct

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The influences of both hole cold expansion and interference-fit fasteners for extending the fatigue life of multi-layer aluminium alloy joint specimens under variable-amplitude loading have been examined experimentally. Improvements in fatigue life were markedly dependent on the degree of load transfer in the specimen joint. Secondary bending in the joint also had a major influence, reducing the effectiveness of these life improvement techniques. Depending on the joint configuration, improvements in fatigue life ranged from nothing at all to a factor of about 40. Fretting appeared to be involved in the initiation of all cracks and where this occurred on faying surfaces only small, if any, improvements in fatigue life were obtained.

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Fatigue characteristics of joints with holes cold-expanded in a multi-layer stack

Cited by 8 publications

References 6 publications

Finite Element Analysis of Split Sleeve Cold Expansion Process on Multiple Hole Aluminum Alloy

Finite Element Analysis of Split Sleeve Cold Expansion Process on Multiple Hole Aluminum Alloy

Fatigue of Thick‐section Cold‐expanded Holes With and Without Cracks

Extending the Fatigue Life of Multi‐layer Metal Joints

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