PSI - Issue 13

V.N. Shlyannikov et al. / Procedia Structural Integrity 13 (2018) 1117–1122 Boychenko N.V. / Structural Integrity Procedia 00 (2018) 000 – 000

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It is found that for all specimens considered here the In-integral is almost unchanged when mode mixity M P < 0.6. Moreover, in this range of mixed mode loading, no significant effect of elastic – plastic material properties is observed. However, in the case of mode mixity when M P ≥ 0.6, the I n -integral distributions differ increasingly as a function of material properties, described by the hardening exponent, mixity M P ranging from 0 to 1. Figure 4 shows the values of the stress triaxiality parameter for all considered test specimen configurations with the set of structural materials of different properties as a function of mode mixity M P . As it follows from these results the stress triaxiality parameter h is almost unchanged for all specimens when mode mixity M P < 0.75. In this range of mixed-mode loading no significant effect of elastic – plastic material properties is observed. However, when the mode mixity M P ≥ 0.75 the stress triaxiality parameter distributions differ increasingly as a function of material properties.

a) c ) Fig. 4. Variation of the stress triaxility h in the CTS (a), CS-1 (b) and CS-2 (c) as a function of mixity parameter. b)

The results of numerical calculations of J-integral for the CTS, CS-1 and CS-2 cracked specimens under mixed mode loading are presented in Fig.5. As it follows from these results, the significant effect on the J-integral associated with the elastic-plastic material properties in comparison with distributions of the I n -integral and stress triaxility parameter. 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. All elastic – plastic parameters considered in this study are sensitive to the changes in mode mixity. Both In integral and the local parameter stress triaxiality as shown in Figs. 2 and 4 moderately increase when M P ranges from 0 to 1. However, the J-integral values decrease in the full range of mixed modes from pure shear M P = 0 to normal tension M P = 1.

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b) c ) Fig. 5. The effect of material properties on J-integral for the CTS (a), CS-1 (b) and CS-2 (c).