PSI - Issue 18

A.P. Zakharov et al. / Procedia Structural Integrity 18 (2019) 749–756 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

755

7

of the Ramberg – Osgood constitutive equation, respectively.

Table 1. Elastic-plastic mechanical properties. Material E [GPa] σ 0 [MPa]

σ u [MPa]

n

α

Steel P2M Steel 34XH3MA

226.9

362.4 714.4

1190.0 1260.4

4.141 7.889

4.131 0.529

216.21

Al 7050 Ti6Al4V

70.57

471.6 885.5

701.0

10.851 12.588

1.570 1.225

118.01

1289.6

Shlyannikov and Zakharov (2017) obtained elastic-plastic parameters such as the governing parameter of the elastic-plastic crack tip stress field I n -integral, the stress triaxiality and the plastic SIF under small-scale yielding for specified test specimen geometries above, mixed mode loading conditions and material properties. In the present study the mixed mode crack behaviour was characterized by large-scale yielding plastic SIF. Fig.6 shows the distributions of the J -integral for all considered test specimen configurations with the set of elastic-plastic materials properties as a function of mode mixity M P ranging from 0 to 1.

Fig.6. J -integral distributions for the CTS (a), CS-1 (b) and CS-2 (c).

As it follows from these results, the significant effect on the J -integral associated with the elastic-plastic material properties in a full range of mixed modes. It should be noted that the J -integral at pure Mode I is less than that at pure Mode II. It can be explained in terms of the plastic zone that develops directly ahead of the crack tip in a large scale under a mixed mode loading with respect to pure Mode I. For the test specimen configurations considered here values of the large-scale yielding plastic SIF are presented in Fig.7 in comparison with results of small-scale yielding FE analysis obtained by Shlyannikov and Zakharov (2017). Note, that plastic SIF for small-scale yielding ( K ssy ) and large-scale yielding ( K p ) were calculated by Eq.(2) and Eq.(8) respectively.