PSI - Issue 61

Sandipan Baruah et al. / Procedia Structural Integrity 61 (2024) 180–187 Baruah and Singh/ Structural Integrity Procedia 00 (2024) 000 – 000

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. The plots of damage at 15 % strain at room temperature and elevated temperatures are shown in Fig. 6. At the same level of strain, the damage at the gauge portion of the specimen varies with temperatures, with higher damage at 55 0˚C and 600 ˚C , but lower damage at other temperatures. This behaviour in Fig. 6 occurs due to that high amounts of softening at these temperature for this material, which can also be seen in Fig. 5. Fig. 5. Stress-strain plots with elasto-plastic softening of Q960 steel at room temperature and elevated temperatures (Comparison of present simulations using gradient damage methodology with experimental data of Wang et al. (2020) and with classical elasto-plasticity)

Fig. 6. Damage in the Q960 specimens at a strain of 15 % at room temperature and elevated temperatures

4. Conclusions The major conclusions that can be drawn from the present work are stated as follows :

a) The temperature-dependent damage evolution law and simulations using gradient damage methodology satisfactorily predicts the plastic softening behaviour at elevated temperatures. The stresses computed by the present gradient damage methodology at strains greater than 3% are successfully captured at all temperatures and are in good agreement with the experimental measurements. b) The limitation of classical elastoplasticity to simulate plastic softening at elevated temperatures is resolved by the present damage-based computations with the proposed damage law. c) The implicit formulation of gradient damage used in the present work may lead to artificial expansion of the damage bands which may violate the actual physical process. At high temperatures, such behaviour may not be visibly dominant. Nevertheless, it is expected that in future, the present work can be improved by using a localizing damage framework at high temperatures. d) Although significant amounts of strains are observed during the softening regimes, the present methodology has been formulated on the basis of small strains in order maintain simplicity of the method and to avoid huge