PSI - Issue 28

Giovanni Pio Pucillo et al. / Procedia Structural Integrity 28 (2020) 1998–2012 GP Pucillo et al. – Part I / Structural Integrity Procedia 00 (2019) 000 – 000

2001

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2. Experimental campaign To evaluate both the strain field during the process and the residual strain field after mandrel removal, a rail segment was considered, having six holes of the same diameter of real railway joints, 32 mm. As shown in Fig. 1, before expanding the holes, part of the rail foot and of the rail head have been removed, with the aim to create the gripping areas of the specimens that will be extracted from the expanded and not expanded drilled rails, and that will be submitted to fatigue tests. In (Pucillo 2019), finite element analyses have demonstrated that the removal of part of the foot and of the head does not modify the residual stress distribution due to cold expansion compared to that obtained with the full rail section, so the modified rail was assumed to be representative of the real drilled rail. The experimental results presented in this work concern the cold expansion process applied on holes #2, #5, and #6. To achieve a 2.0% of cold expansion (see (Pucillo et al. 2020), Section 1), an FTI RTS 32-0 mandrel, and a RTS32-0 self-lubricated split-sleeve, the sleeve having a thickness of 0.3 mm, were used (see Fig. 2).

E60 railway rail

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hole #1 hole #2 hole #3 hole #4 hole #5 hole #6

Head

Head and foot removal

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Foot

Fig. 1. Rail segment used for the experiments.

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b

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d

Fig. 2. FTI’s tooling: (a) mandrel; (b) split sleeve; (c) power units; (d) puller.