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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but less damage at 700˚C. This behaviour in Fig. 3 occurs due to low amounts of softening at temperatures above 500˚C for this material, which can also be seen in Fig. 2.

Fig. 3. Damage in the S900 steel specimens at a strain of 10 % at room temperature and elevated temperatures

3.2. Q960 steel specimens Wang et al. (2020) experimentally investigated the stress-strain behaviour of Q960 high-strength steel at elevated temperatures. Their specimen geometry is shown in Fig. 4(a), and the present finite element mesh is shown in Fig. 4(b). The material properties are listed in Table 2. For simulating using the present damage law and gradient-enhanced damage methodology, the damage parameters chosen for the material are α = 4.2×10 -12 and β = 8.2. The numerical length-scale ( l ) parameter for non-local damage evolution is considered (1/100) th of the size of the specimen. The simulated plots at different temperatures using gradient damage methodology are compared in Fig. 5 with the experimental data of Wang et al. (2020) and with classical von Mises elastoplasticity using Ramberg-Osgood hardening. Similar to the previous example, it can also be observed that the present simulations better capture the material softening at elevated temperatures and are found in good agreement with the experimental data.

Table 2. Material properties of Q960 steel at different temperatures obtained from experiments of Wang et al. (2020) Temperature (˚C) Young’s modulus ( E ) (GPa) Yield-stress ( σ y ) (MPa) Parameters of classical elastoplasticity using Ramberg-Osgood hardening: = ( / ) + ( / ) k (MPa) n 20 204 965 1084.2 39.43 300 193 870.6 1021.8 38.89 450 186.5 821.7 1055.0 24.85 550 170 701.5 903.6 25.07 600 159.8 631.1 723.2 37.41 700 92.5 215.8 296.5 23.63 Fig. 4. (a) Q960 steel tensile specimen tested at elevated temperatures by Wang et al. (2020) (All dimensions are in mm). (b) Finite element mesh for simulation using gradient damage methodology in the present work.