PSI - Issue 39

9

Abhishek Tiwari / Procedia Structural Integrity 39 (2022) 290–300 Abhishek Tiwari/ Structural Integrity Procedia 00 (2019) 000–000

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(a)

(b)

Fig. 5. (a) Comparison of J -integral behavior for different contours calculated using configurational force method with non-linear elastic assumptions in the load application stage and (b) the path independence of J in the creeping stage for a crack tip location of L / b o = -0.2.

However, the d J /dt vs C t comparison in Fig. 6 shows that both integrals are path independent except the far-field C t values. Another difference between C t and d J /dt values are that there is a constant diefference between the two values unlike creep inhomogeneity study in section 5.1. This may be attributed to the fact that the C t calculation of Abaqus does not consider any other strain than the creep strain. Hence, the plastic strain energy density, which will have a constant contribution once creep starts might be the difference between the two values. The CDF in terms of ratios of J -integral at tip and and for far-field contour is plotted in Fig. 7. The values in Fig. 7 are plotted at a constant value of J far at 39.58kJ/m 2 . The behaviour shows that the initial behavior is similar to a stiff to compliant transition. However, at L / b o = -0.04 the behaviour reverses and the CDF drops down.

Effect of material inhomogeneity under creep

Fig. 6. Differences in path independent C t (except for far-contour) and path independent d J /dt showing a constant difference expected to be due to the time independent strain (elastic and plastic) components in a plastic to creeping material transition.