PSI - Issue 61

Toros Arda Akşen et al. / Procedia Structural Integrity 61 (2024) 268 – 276 6 Toros Arda Akşen, Bora Şener, Emre Esener, Ümit Kocabıçak, Mehmet Fırat / Structural Integrity Procedia 00 (2019) 000 – 000

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4.1. Yield Surface Calibration The HomPol4 yield criterion implemented in this work has nine parameters to adjust. The high number of parameters ensures the high estimation capability of the anisotropic features of the AA6016-T4 aluminum sheet. The adjusted HomPol4 parameters are given in Table 3. Besides, Fig. 2 illustrates the analytical estimations by the HomPol4 criterion.

Table 3. Calculated HomPol4 parameters.

Material

a 1

a 2

a 3

a 4

a 5

a 6

a 7

a 8

a 9

AA6016-T4

1

-2.13

2.67

-1.58

1.03

6.15

-0.38

5.23

5.40

a

b

c

Fig. 2. Analytical predictions, (a) yield surface; (b) yield stress ratios; (c) r values.

The HomPol4 criterion produced a convex yield locus and well predicted the equi-biaxial yield stress data. Moreover, the experimental values of both directional yield stresses and Lankford ’s coefficients were precisely predicted through the implemented model, which shows the performance of the HomPol4 criterion. 4.2. Construction of the Fracture Loci In the current research, VGM and MMC criteria were implemented in the Hypela2 subroutine in Marc software to construct the fracture loci. To this end, each specimen's FE models of the tensile test were generated. Fig. 3 shows the mesh layouts of the specimen's geometrical discontinuity regions.

d

a

e

b

c

f

Fig. 3. Mesh layouts of tensile test specimens, (a) STT; (b) NT5; (c) NT10; (d) NT20; (e) CH; (f) SH.