Finite-element simulation of residual stress induced by split-sleeve cold-expansion process of holes

Abstract

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. A three-dimensional finite-element simulation was conducted for a split-sleeve coldexpansion process in order to determine the residual stress field around an expanded hole.The commercial FEA software DEFORM-3D TM , a Lagrangian implicit code designed for metal forming processes, was used to model the cold-expansion process of a fastener hole. The results show a through-thickness residual stress field in good agreement with the analytical solution developed by Guo. Moreover, the simulation has highlighted the effect of the split sleeve and the plate thickness on the residual stress field.

On the Measurement and Prediction of the Out-of-Plane Displacement Surrounding Cold-Expanded Holes

“…It was clearly observed in the comparison between 5 mm and 3 mm thick plates. A similar reduction in residual stresses for increasing thickness of the plate was also observed in a previous work [12].…”

“…One possible explanation may be that the boundary conditions assumed by the theories do not match those of the cold-expansion process. This has been also shown by previous experimental [13] and finite element [9,12] works that highlight how the predicted residual stresses would have to be compared with those on the outlet face rather than the mid-thickness one. Moreover the three-dimensional nature of the process is strongly affected by the presence of the split sleeve and this fact is not considered in the theories in which the plate thickness does not play any role.…”

“…Given the complex form of the equations (7b) and (8), the solution of out-of-plane displacement, v z(r) , cannot be readily solved by integrating equations (12). Therefore, an approach based on Riemann's integral was adopted to partition the plastic domain [a,r p ] into i sub-intervals [r i-1 ,r i ].…”

“…One of these [10] highlighted that the residual stress distribution is not uniform across the thickness being the magnitude of residual stresses close to the mandrel outlet face greater than those of the mandrel entrance face. Moreover, a recent analysis [12] highlighted that at pip location corresponding to the split of the sleeve, the hoop residual stress is significantly lower than that at 90°from the pip. Among the experimental techniques, Sach's boring out technique was used by Ozdemir et al [13] to measure the 3D residual stress distribution around cold-expanded holes.…”

Residual strains around cold worked holes from statistical view

“…al. (1999), Jahed et al (2000), Zhao et al(2003), Pinho et al (2005), Matos et al (2005), Hojjati and Hassani (2007), Nigrelli and Pasta (2008), Su et. al.…”