PSI - Issue 68

Eren Çelikses et al. / Procedia Structural Integrity 68 (2025) 1045–1050 E. C¸ elikses et al. / Procedia Structural Integrity 00 (2024) 000–000

1047

3

Fig. 1: (a) Banded and (b) dispersed martensite microstructures of DP800.

Table 1: Results of tensile tests.

Yield Strength [MPa]

Tensile Strength [MPa]

Elongation [%]

r

n

DP800 Banded DP800 Dispersed

535 534

841 847

17 18

0.79 0.82

0.13 0.13

material thickness. On average, the DP800 steel with banded structure exhibited a hole expansion ratio of 8.9, while the DP800 with the dispersed martensite distribution demonstrated an average ratio of 21.3. Forming Limit Curve (FLC) is used to assess whether a material will undergo tearing after deformation under various stress conditions. In this study, FLCs are generated following the guidelines in the ISO 12004-2 standard. Eight di ff erent geometries are tested to establish varied strain paths, with each geometry tested in three repetitions. The final results are obtained by averaging the three tests. During the experiments, the digital image correlation (DIC) technique is employed to measure plastic deformations on the sample surfaces. GOM ARAMIS equipment is utilized for DIC measurements, enabling the capture of FLC curves. The results are illustrated in Fig. 2 where a noticeable decrease in formability is observed for the banded DP800 specifically towards the biaxial tension case..

0.4

0.3

0.2

0.1

0

-0.1

0

0.1

0.2

0.3

Fig. 2: FLC results of DP800 samples.