Issue34

S. Henschel et alii, Frattura ed Integrità Strutturale, 34 (2015) 326-333; DOI: 10.3221/IGF-ESIS.34.35 331 0 50 100 150 200 250 -60 -40 -20 0 20 Height / µm Position / µm 1 2 3 Crack tip blunting Crack path deflection b) Figure 5: Crack path deflection was considerably larger than crack tip blunting. Cast A, dynamic loading. a) Fracture surface, b) Height profile of the lines shown in a). Effect of loading rate Dynamic loading affected the appearance of the fracture surface. Two typical fracture surfaces are compared in Fig. 6. Figure 6: a) Ductile fracture surface, Cast A, static loading; b) flat appearance of ductile fracture surface, Cast C, dynamic loading. It was observed that the material failed by ductile fracture at both loading rates. However, the dimples in Fig. 6b appeared to be flatter than in Fig. 6a. The inclusion content was nearly equal at that position. Furthermore, it was observed that not only Al 2 O 3 inclusions but also MnS inclusions influenced the damage evolution. The MnS inclusions found in the regions of the relatively flat fracture surface had a diameter of approximately 5 µm. However, the majority of the small dimples exhibited no measureable non-metallic inclusions. This was attributed to void initiation at small carbides. C ONCLUSIONS ntentional addition of non-metallic inclusion was utilized to study the effect of an inhomogeneous inclusion distribution on the formation of the crack path. The effect of clustered non-metallic inclusions was demonstrated in the case of a high-strength cast steel G42CrMo4. The main conclusions can be drawn as follows:  Clustered non-metallic inclusions significantly affected the crack path. The inclusion clusters promoted the formation of a crack at the weakest point of the cluster. Hence, the main crack was deflected towards the crack in the inclusion cluster. I