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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3.1. S900 steel specimens Narimani et al. (2023) experimentally examined the stress-strain behaviour of S900 high-strength steel at elevated temperatures. Their specimen geometry is shown in Fig. 1(a), and the present finite element mesh is shown in Fig. 1(b). The material properties are listed in Table 1. Using the present damage law and gradient enhanced damage methodology, numerical simulations are performed at different temperatures through displacement-controlled loading. The damage parameters is chosen for the material are α = 3.8×10 -11 and β = 18.6. The numerical length-scale ( l ) parameter for non-local damage evolution is considered as (1/100) th of the size of the specimen. In Fig. 2, the simulated plots at different temperatures using gradient damage methodology are compared with the experimental data of Narimani et al. (2023) and with classical von Mises elastoplasticity using Ramberg-Osgood hardening. It can be observed in Fig. 2 that the present damage law with gradient damage-based simulations captures the material softening at elevated temperatures in good agreement with experimental temperatures and with better accuracy as compared to classical elastoplasticity. Table 1. Material properties of S900 steel at different temperatures obtained from experiments of Narimani et al. (2023) Temperature (˚C) Young’s modulus ( E ) (GPa) Yield-stress ( σ y ) (MPa) Parameters of classical elastoplasticity using Ramberg-Osgood hardening: = ( / ) + ( / ) k (MPa) n 25 215 945 1055.0 81.10 400 160 802 946.7 48.54 500 146 681 844.9 40.20 600 78 422 554.5 26.47 700 61 214 247.1 60.46 Fig. 1. (a) S900 steel tensile specimen tested at elevated temperatures by Narimani et al. (2023) (All dimensions are in mm). (b) Finite element mesh for simulation using gradient damage methodology in the present work.

The plots of damage at 10 % strain at room temperature and elevated temperatures are shown in Fig. 3. At the same level of strain, the damage at the gauge portion of the specimens varies with temperatures, with more damage at 500˚C, Fig. 2. Stress-strain plots with elasto-plastic softening of S900 steel at room temperature and elevated temperatures (Comparison of present simulations using gradient damage methodology with experimental data of Narimani et al. (2023) and with classical elasto-plasticity)