PSI - Issue 42

K. Koch et al. / Procedia Structural Integrity 42 (2022) 506–512

511

6

Author name / Structural Integrity Procedia 00 (2019) 000 – 000

b)

a)

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

6

EN-GJS-400-18 a 0 / W = 0.5 E 0 = 3 J

Test data Corrected

Test data Corrected

F max

5

42CrMo4 a 0 / W = 0.5 E 0 = 2.5 J

4

3

2.61 J

2

Force [kN]

Force [kN]

2.54 J

0.82 J 0.73 J

1

0

0

200 400 600 800 1000 1200

0

200

400

600

800

1000

Displacement [µm]

Displacement [µm]

Fig. 5. Force-displacement-curves of dynamic fracture toughness tests for (a) steel 42CrMo4 and (b) cast iron EN-GJS-400-18. A comparison of the measured and corrected values show a deviation for the critical integral of more than 10% for 42CrMo4, see Tab. 3. This can be attributed to energy losses. The deviations depend on the impact energy. Therefore, the effect is less significant for EN-GJS-400-18, because of the lower level of force as well as the relatively low strength of the material. The deviations generally lead to an overestimation of the stress on the specimen. Table 3. Effect of energy losses on the calculation of cd . Material (measured) (corrected)

0 [J] 2,0 2,5 3,5 3,0

cd 32 34 29 93

cd 28 30 24 91

Deviation [%]

[kJ/m 2 ]

[kJ/m 2 ]

13 12 17

42CrMo4

EN-GJS-400-18

2

4. Conclusions In this article, the effect of inertia effects on the energy conversion in dynamic fracture toughness tests was investigated. It was possible to identify causes for energy losses in a pendulum impact test machine by displacement measurements with a laser. The amounts of dissipated energy and their effect on the calculation of was examined for both cast iron and high strength steel. It could be observed that an incomplete energy conversion happens due to the elastic deformation of the support, which partially remains after force release of the specimen. This effect is distinct for materials with high strength and at high impact energy. Furthermore, energy losses due to plastic deformation in the area of Hertzian contact between the tup and the specimen were observed. This effect is more significant for materials with a low yield strength and at high impact energy. It should be noted that the investigations were carried out at overall relatively low impact velocities. The effects that occurred in these tests can vary at higher impact velocities ( 0 > 1 m/s) and also depend on the characteristics of the test setup. Acknowledgements The authors thank the German Research Foundation (DFG) for the financial support of the investigations in the Collaborative Research Center 920 - Project-ID 169148856, subproject C05. Special thanks to Moritz Roßberg for supporting the experimental investigations.