PSI - Issue 18

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

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Fig.7. Plastic SIF distributions for both small-scale yielding ( K ssy ) and large-scale yielding ( K p ) for the CS-1 (a), CS-2 (b) and CTS (c).

Plastic SIF in Fig.7 are presented as a function of mixed mode loading for high strength steel with strain hardening exponent n = 4.141 and titanium alloy ( n = 12.59). In Fig.7 solid lines correspond to the plastic SIF at small-scale yielding as well as dashed lines correspond to large-scale yielding plastic SIF. As it follows from results presented in Fig.7, there is a significant difference between small- and large-scale yielding plastic SIF in the full range of mixed modes. Therefore in the case of cracked bodies under mixe d mode loading it is doesn’t correct to use the plastic SIF formulation for small-scale yielding in accordance with Hutchinson’s (1968) and Shih’s (1974) relations between the J -integral and K p . 5. Conclusions The infinite sized central cracked plate under biaxial loading as well as cruciform specimens of two configurations and a compact tension – shear specimen subjected to mixed Mode I/II loading were used to study the crack-tip fracture resistance parameters by using an elastic – plastic FE analysis. Coupling effects of crack tip configuration, biaxial stress ratio and applied nominal stresses on the J -integral and governing parameter of elastic plastic crack-tip stress fields I n -integral as well as the plastic SIF behaviour were stated. The contrary trends of biaxiality effects on J -integral behavior were established depending on crack tip configuration. In the CCP with finite radius crack tip a significant difference between plastic SIF obtained for small-scale yielding ( K ssy ) and large scale yielding ( K p ) was observed with respect to CCP with mathematical notch type crack. Special emphasis was put on the behavior of J -integral and the plastic SIF for specified test specimen geometries under mixed mode loading. For all considered test specimen configurations trends of the J -integral as well as the plastic SIF behavior as a function of mode mixity and material nonlinearity were founded. The applicability of the plastic stress intensity factor approach to large-scale yielding analysis of cracked bodies under mixed mode loading was demonstrated. References Hutchinson J., 1968. Singular behaviour at the end of a tensile crack in a hardening material. J. Mech. Phys. Solids 16, 13 - 31. Shih C., 1974. Small - scale yielding analysis of mixed mode plane - strain crack problems. ASTM STP 560, 187 - 210. Hilton P., Hutchinson J., 1971. Plastic intensity factors for cracked plates. Eng. Fract. Mech. 3, 435 - 451. Hilton P., Sih G., 1973. Applications of finite element method to the calculations of stress intensity factors. Mechanics of Fracture. Methods of Analysis and Solution of Crack Problems. 1, 426 - 483. Hilton P., 1973. Plastic intensity factors for cracked plates subjected to biaxial loading. Int. J. Fract. 9, 149–156. Shlyannikov V., Tumanov A., 2014. Characterization of crack tip stress fields in test specimens using mode mixity parameters. Int. J. Fract. 185, 49 - 76. Lee J., Liebowitz H., 1977. The nonlinear and biaxial effects on energy release rate, J - integral and stress intensity factor. Engng. Fract. Mech. 9, 765 - 779. Shlyannikov V., A.P. Zakharov A., 2017. Generalization of mixed mode crack behavior by plastic stress intensity factor. Theoret. Appl. Fract. Mech. 91, 52 - 65.