PSI - Issue 57

Jacopo Pelizzari et al. / Procedia Structural Integrity 57 (2024) 817–823 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

819

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Fig. 2. Geometry of the plain cylindrical specimens tested under strain-controlled fatigue loading. Specimens have been extracted from the trumpet at the location defined in Fig.1. The dimensions are expressed in mm. The axle’s trumpet is made of EN-GJS-500-7 pearlitic cast iron according to EN 1563:2018 [7]. Fig. 3 shows the microstructure of the specimen n°1 tested under static tensile loading, the microstructure of specimen n°2 being similar. The shape and dimension of the spheroids have been assessed according to ISO 945-1:2019 [8] adopting the unetched surface image while the microstructure composition has been assessed starting from the etched surface as reported in Fig. 3b. The graphite nodules can be classified as VI – 6/7 and the average microstructure composition is pearlitic (60%) – ferritic (40%). The Brinell hardness has been measured adopting a SwissMax 600 digital hardness tester and testing parameters HBW 2.5/187.5 according to [9]. The resulting Brinell hardness values fall in the range 220 ÷ 230 HBW.

200 μ m

200 μ m

(a)

(b)

Fig. 3. Microstructures of the EN-GJS-500-7 pearlitic cast iron (a) before and (b) after Nital 2% etching relevant to the specimen n°1 tested under tensile loading. The microstructure is shown at 100x magnification according to ISO 945:1 2019 [8]. 3. Static and fatigue properties of the pearlitic cast iron Two specimens for static tensile tests and nine specimens for strain-controlled fatigue tests have been tested. A 858 Minibionix II servo-hydraulic test machine has been adopted for both the static and the strain-controlled fatigue tests. The strain has been measured by an MTS extensometer 634.12F-24 with a gauge length equal to 25 mm during the static tensile tests while an MTS extensometer 632-13F-20 with a gauge length equal to 10 mm has been adopted to measure the strain during the fatigue tests. The static tensile tests have been performed under displacement control by adopting a displacement rate of 0.45 mm/min, corresponding to a strain rate of 2.5 ∙ 10 -4 s -1 . The obtained static curves are reported in Fig. 4a, while the static properties and the Ramberg-Osgood equation (Eq. 1) parameters are reported in Table 1. The collected static data are greater than the minimum reference values recommended by EN 1563:2018 [7] for specimens in EN-GJS-500-7 cut from the castings (minimum yield strength  p0.2 = 300 MPa, minimum tensile strength  R = 480 MPa and minimum elongation A = 6%). = +( ) 1 (1)