PSI - Issue 18

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Kim Bergner et al. / Procedia Structural Integrity 18 (2019) 792–801 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Table 2. Chemical composition of the EN-GJS-400-15 casting blanks (weight-%) [Kutz (2018)]

Casting Type

C

Si

Mg

Cu

Mn

S

P

CE

1 – PT_III 2 – GE_I 3 – GE_II

3.72 3.76 3.64

2.66 2.45 2.47

0.034 0.032 0.028

0.062 0.065 0.066

0.120 0.168 0.138

0.009 0.009 0.008

0.011 0.029 0.022

4.61 4.57 4.47

In addition to the castings produced for this project, tests results of EN-GJS-270 were used, since its microstructure shows a pearlitic matrix with graphite lamellae and is thereby comparable to the microstructure of the rim / the degenerated graphite layer [Rausch (2011)].

Fig. 1. Produced casting blank geometry (top left), microstructure of EN-GJS-400-15 without rim with surface roughness – PT_III (top right), with rim of lamellar graphite in pearlitic matrix – GE_I (bottom left) and lamellar graphite in ferritic matrix – GE_II (bottom right)

2.2. Fatigue tests The influence of the casting skin on fatigue lifetime of the cast components was determined by fatigue tests with bending specimens (Fig. 2) under tensile R σ = 0 and alternating load R σ = -1 and under ambient air and room temperature. The fatigue tests were performed on servo-hydraulic test rigs (Fig. 3) with a maximum load capacity of 10 kN, until a loss of stiffness of the specimen of 20 % compared to the initial state, or until the achievement of the limit number of cycles of N lim = 1ꞏ10 7 , with test frequencies between 20 and 40 Hz. The clamping system, which was especially designed for fatigue tests of surface areas, ensures maximum load on the surface of the specimen (with and without casting skin). Two types of bending specimens were manufactured from the bottom of the casting blank (Fig. 1, Fig. 2), with and without casting skin, to investigate the influence of the casting skin on fatigue strength.