PSI - Issue 17

Pavel Konopik et al. / Procedia Structural Integrity 17 (2019) 479–486 Konopik P. et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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5. Result discussion

Tensile test performed on both investigated materials show very homogenous results which is necessary for further investigation of size factor in case of fracture toughness. The result of fracture toughness summarized in Table 3 and depicted in Fig. 7 do not show clear trend for both materials. While the results for 27NiCrMoV 15-6 steel indicates almost pure linear dependency of specimen thickness B on fracture toughness, the result for 34CrNiMo6 steel shows almost clear independency. This can be caused by higher tensile strength and less elongation of 34CrNiMo6 steel which may cause less plastic deformation on the tip of sharp fatigue crack and therefore, the crack resistance for material with higher strength is less.

Table 3. Chemical composition of investigated materials Material Type J Q , J IC B kN/m mm 27NiCrMoV_1 0,16 CT 194,8 4 27NiCrMoV_2 3PB, 3x4 202,9 3 27NiCrMoV_3 3PB, 10x10 420,6 10 27NiCrMoV_4 1 CT 648,8 25 34CrNiMo6_1 3PB, 3x4 193,2 3 34CrNiMo6_2 3PB, 10x10 192,7 10 34CrNiMo6_3 3PB, 15x30 196,2 15

Fig. 7. Dependency of fracture toughness

6. Conclusion

Tensile test and fracture toughness tests were performed using standard and miniaturized specimens. The investigated materials were two steels used for production of several parts in energy industry – namely 34CrNiMo6 and 27NiCrMoV 15-6. The results indicates that fracture toughness do not depend only on constraint effect and geometrical factor but on other mechanical characteristic as well. The data contribute to global knowledge in this field. Further investigations with additional materials and specimen geometries are planned to provide sound base for the methods applicability for the currently investigated materials.