Issue 46

A. Baltach et alii, Frattura ed Integrità Strutturale, 46 (2018) 252-265; DOI: 10.3221/IGF-ESIS.46.23 255 L (mm) Taper angle α Taper λ % 2 6°35’ 11.5 3 4°23’ 7.667 6 2°12’ 3.833 8 1°39’ 2.875 10 1°19’ 2.3 Table 1 : Parameters of different tapered pin used in the study. F INITE ELEMENT MODEL three dimensional finite element model was performed to simulate the cold expansion procedure. Thus, as already argued in [12], a 3-D model was preferred to the axi-symetric 2-D one because of rectangular plate shape and because it is easy to apply a longitudinal tensile load after cold expanding the plate. More even, the objective here is to analyze the residual stresses along the thickness of the hole. Abaqus 6.14 commercial finite element code was used to carry out this analysis. The finite element modelization for the plates and assembly sets are shown in Figs. 4. Fig. 5 shows the assembled sets for some studied cases. Figure 4 : Finite element model for plate and assembly sets. The studied models are symmetrical with respect to the X–Z and Y–Z planes; therefore only a quarter of these geometries were modeled. The hole diameter is 5 mm and the largest diameter of the tapered pin is 5.23 mm which produces a 4.6% interference fit when it enters the hole. Also, the diameter of the ball is taken 5.23 mm to produce the same interference fit. The simulation of the cold expansion process is carried out by modeling contact between the face of the hole and the mandrel allowing pressure to be transferred between the contacting surfaces but without them penetrating each other. The thickness is divided to 24 linear brick elements (C3D8R) (Fig. 5). This type of element is adapted in the case of elasto-plastic calculations, and also is well conjugated with contact elements [32]. Figure 5 : Finite element detail for the assembled model near the hole edge, (a) Expansion with a tapered pin and (b) expansion with a ball. A a) b)