PSI - Issue 36

Valeriy Kharchenko et al. / Procedia Structural Integrity 36 (2022) 145–152 Valeriy Kharchenko, Eugene Kondryakov, Andriy Kravchuk et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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Fig. 8 shows the loading diagrams for the specimens of Hardox 450 high strength steel (Fig. 8(a)) and ARMOX 500T (Fig. 8(b)) cut in different directions. It can be seen that for Hardox steel, the direction of specimen cut has almost no effect on the obtained results. An increase in the strain rate from 2600 s -1 to 5200 s -1 leads to an increase in the level of forces and stresses by 20%, thus, the resistance to deformation increases.

Fig. 7. Loading diagrams F(t) for the specimens with shear zone length L = 1 mm (a), 2 mm (b) and 4 mm (c) from steel 20 with chamfer radii R = 0.25 and 0.5 mm.

Fig. 8. Loading diagrams F(t) for specimens of Hardox 450 (a) and ARMOX 500T (b) steels cut in longitudinal and transverse directions. An analysis of the macroscopic fracture surfaces shows that at strain rates 1300 s -1 the macroscopic fracture surface of specimens of steel 20 is very inhomogeneous (Fig.9(a)). The crack propagates with many "shear lips" indicating a ductile fracture under quasi-static shear loading conditions. At strain rates 5200 s -1 (Fig.9(c, d), the macroscopic fracture surface of the specimens of steel 20 is flatter and more uniform as compared with the quasi-static conditions. A lot of oval-shaped dimples are distributed on this surface, i.e. a large plastic deformation of the material. The analysis of the macroscopic fracture surfaces of specimens of steel 20 implied no significant differences in the character of material fracture under shear conditions.