PSI - Issue 14

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Taslim D. Shikalgar et al. / Procedia Structural Integrity 14 (2019) 529–536 T.D.Shikalgar et al./ Structural Integrity Procedia 00 (2018) 000–000

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Fig. 10. Numerical J-integral v/s punch displacement data for FEA with GTN model of material (a) 20MnMoNi55, (b) T91.

To improve predictions of J-initiation, computations are repeated incorporating the suggestions given by Dutta et al. (2008). The GTN Parameters used for the present study are same as shown in Table 3, except that parameter q 2 is split into two further parameters namely q 2a and q 2b .

Fig. 11. Comparison of FEA, FEA GTN and FEA GTN with modified q2 result with experimental data of (a) 20MnMoNi55, (b) T91.

Fig. 11 show the comparison between the computed and experimental values of load v/s displacement curves. The GTN damage model with a new form of q 2 parameter has much-improved matching with the experimental results. The value of J-initiation in modified GTN model is calculated as 141.66 kJ/m 2 and 194.22 kJ/m 2 of material 20MnMoNi55 and T91 respectively (Fig. 12), and it is very close to the value of conventional CT specimen. Table 4 shows the J-initiation calculated using the above three methods, namely, elastic-plastic FE analysis, FE analysis using Conventional GTN and FE analysis using GTN with modified q 2 . The experimental values quoted in literature is also seen in the same table. It may be seen that predicted fracture toughness (J i ) value using modified GTN has good matching with the value obtained by the standard test.

Fig. 12. Numerical J-integral v/s punch displacement data for FEA GTN model with q2 variation.