PSI - Issue 5

Mihkel Kõrgesaar et al. / Procedia Structural Integrity 5 (2017) 713–720 Author name / Structural Integrity Procedia 00 (2017) 000 – 000

715

3

Fig. 1. (a) Depiction of the governing challenge in ductile fracture modelling of large structures. (b) Failure strain dependency determined with tensile test. Data from Alsos et al. (2009).

  

   

3















n

0 (1) where ̅ is the equivalent stress, ̅ is the equivalent plastic strain, and 0 accounts for the existence of a strain plateau. Numerical finite element simulations of the dog-bone tests were performed with FE software Abaqus 6.13-3/Explicit using reduced integration solid elements (C3D8R). In-plane element size in the gauge region was 0.3 x 0.3 with 4 elements through thickness. In developing the FE models, 1/8-symmetry of the specimen geometry and loading was exploited, see Fig.2 (c). The computational time in simulations was reduced by mass scaling the entire model in the beginning of the analysis by a factor of 14. Despite this large factor, comparison with non-mass scaled solution indicated that changes in the mass and consequent increases in the inertial forces did not alter the solution accuracy nor did it increase the kinetic energy over 5% of total internal energy. The force-displacement curve obtained from simulations is compared with experimental response in Fig. 2(a). Shell element calibration is described later in the simulations chapter. 0 1 1 exp    1   i i i Q C         

Table 1. Description of tensile tests.

Specimen id.

t1 (mm)

t2(mm)

t (average) Gauge width (mm) Loading speed (mm/min)

DB-1-3 DB-2-3

2.98 3.00

2.98 2.98 2.97 2.99

15.08 15.04

2 2

Table 2. Material parameters for the hardening model

Q 1

Q 2

Q 3

C 1 [-]

C 2 [-]

1.454 C 3 [-]

Thickness

[-]

n

3 mm 280

84.32

470.1

137.8

25

0.6

-0.009

0.18