PSI - Issue 35

Toros Arda Akşen et al. / Procedia Structural Integrity 35 (2022) 82 – 90 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

87

6

a

0.98 0.99 1 1.01 1.02 1.03 1.04

b

0.6 0.8 1 1.2 1.4

Experiment (TRIP590) Experiment (TWIP940)

Experiment (TRIP590) Experiment (TWIP940)

TRIP590 TWIP940

TRIP590 TWIP940

r value

Yield stress ratio

0 15 30 45 60 75 90

0 15 30 45 60 75 90 Angle from RD [deg.]

Angle from RD [deg.]

Fig. 2. Directionalities of plastic properties predicted by HomPol4 criterion a) yield stress ratios b) r values

6. Finite Element Modeling 6.1. Determination of the damage indicator

In the present work, damage indicator was obtained from the UTT simulations. Dimension of the specimens utilized in the simulations were based on the ASTM-E8 standarts. Specimens were discretized with fully integrated hexahedral solid elements (Hex7) (Marc vol. A (2018), Marc vol. B (2018)). Fig.3 demonstrate the comparison of the engineering stress- strain curves for TRIP590 and TWIP940, separately.

a

b

0 300 600 900 1200

TRIP590

TWIP940

0 200 400 600 800

Experiment FEM

Experiment FEM

Eng. Stress [MPa]

Eng. Stress [MPa]

0

0.1 0.2 0.3 0.4

0

0.1 0.2 0.3 0.4 Eng. Strain [mm/mm]

Eng. Strain [mm/mm]

Fig. 3. Comparison of numeric and experimental engineering stress – strain curves for a) TRIP590 b) TWIP940 steels

As it seen from the Fig. 3 that, the numerical results were in agreement with the experiments. To obtain the damage indicators for both steels, the areas under the equivalent stress – equivalent strain curves were computed and their values are shown in Fig. 4.

a

b

0 300 600 900 1200

1000 1500 2000

TRIP590

TWIP940

C frac = 600.317 MPa

0 500

C frac = 421.262 MPa

Eqv. Stress [MPa]

Eqv. Stress [MPa]

0

0.2

0.4

0.6

0

0.2

0.4

0.6

Eqv. Strain

Eqv. Strain

Fig. 4. Calibration of the critical damage parameters for (a) TRIP590 (b) TWIP940 steels