PSI - Issue 19

Kim Bergner et al. / Procedia Structural Integrity 19 (2019) 140–149 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 1. Microstructure of EN-GJS-400-15 without rim with surface roughness (W1), with rim of lamellar graphite in pearlitic matrix with surface roughness (GE_I) and lamellar graphite in ferritic matrix with surface roughness (GE_II); Microstructure of the cast blank, which was based on the rim zone microstructure (W3)

Fig. 2. Schematic representation of the cast blanks with sample positions of the bending specimens with and without casting skin and the flat specimens (left); Bending specimen geometry, bending specimen with machined surface and with casting skin (top right); Small flat specimen and its geometry 2.2. Load-controlled fatigue tests on bending specimens The influence of the casting skin on the fatigue lifetime was determined by fatigue investigations with bending specimens (Fig. 2) under load-controlled pulsating R σ = 0 and alternating load R σ = -1, 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 failure or until the achievement of the limit number of cycles of N lim = 1·10 7 , with test frequencies between 20 and 40 Hz. Flat specimens (Fig. 2) removed from W3 cast blanks, which exhibit a pearlitic microstructure corresponding to the rim zone of GE_I, were used to investigate the cyclic material properties of the rim zone microstructure.

Fig. 3. FE-simulation (left) and Fatigue test setup (right) of bending tests under two-point bending

The test setup for the fatigue life investigations of specimens with casting skin ensures maximum stress and failure on the surface of the specimen (Fig. 3, left). The test results are evaluated, in order to determine the slope k of the