The split sleeve cold expansion process can be used to improve fatigue life in structural components. Holes are drilled into plates in order to accommodate fasteners. These holes serve as stress concentrations that can lead to fatigue cracks. The objective of the present work is to suggest solutions to reduce the likelihood of cracks near the split in the sleeve for this particular process. Two possible solutions for resolving crack formation are investigated numerically using a finite element (FE) code. The first deals with an optimum orientation of the split with respect to the material symmetry axes. For this purpose, an anisotropic response is provided as constitutive material description in the FE code. The second solution deals with a modification of the split sleeve geometry to reduce the strain concentration. The modified sleeve is made from an oversized blank such that the edges overlap. Upon expansion, the edges slide but do not completely separate, unlike the conventional sleeve. The thickness in the overlapping regions of the modified sleeve is tapered to provide a relatively uniform thickness overall.The new sleeve design is investigated experimentally on a 7085-T7651 aerospace aluminum alloy plate. Although the new design is not optimized, experimental evidence shows that it can significantly reduce cracking near a sleeve split.
Numerical and experimental study of the cold expansion process in 7085 plate using a modified split sleeve
Journal of Materials Processing Technology ; 189 , 1-3 ; 45-57
2007
13 Seiten, 18 Bilder, 5 Tabellen, 34 Quellen
Aufsatz (Zeitschrift)
Englisch
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