FINITE ELEMENT SIMULATION OF RESIDUAL STRESSES IN DIFFERENT COLD-EXPANDED PLATE TIDCKNESS

In aircraft and aerospace industry, the fastener holes are widely present because a lot
of its mechanical parts need to be connected by rivets or bolts. However, these holes
experience external forces which cause a tensile stress on the surface which lead to
the futigue cracks and eventually lead to fatigue failure of the structure. Hence, cold
expansion method has been used to improve the fatigue behaviour of structures by
inducing compressive residual stresses around the ,holes when a tapered mandrel is
forced through the fastener hole that is a little smaller than the mandrel. In this study,
finite element simulations had been carried out for cold expansion process in order to
determine the residual stresses field around two cold-expanded holes by varying the
centre distance between two holes and the thickness of the materiaL Moreover, the
effect of through thickness position has been investigated by considering the residual
stresses distribution at different position such as at the entrance face, at the middle
thickness and at the exit face of the material. Aluminium alloy 7075-T6 was used as
the material of the model developed in ANSYS. The results show the effect of
different adjacent holes distance on the residual stresses field. Moreover, the
simulation has highlighted the effect of the plate thickness and the through thickness
position on the residual stresses distribution.