PSI - Issue 61

Toros Arda Akşen et al. / Procedia Structural Integrity 61 (2024) 268 – 276 Toros Arda Akşen, Bora Şener, Emre Esener, Ümit Kocabıçak, Mehmet Fırat / Structural Integrity Procedia 00 (2019) 000 – 000 5

272

d

a

e

b

c

f

Fig. 1. Uniaxial tensile test specimens with different notch shapes, (a) STT; (b) NT5; (c) NT10; (d) NT20; (e) CH; (f) SH (Zhang et al. (2019)).

The standard tensile test was conducted to acquire the hardening behavior and adjust the yield function. The hardening curve parameters were obtained by employing a curve fitting approach to uniaxial tensile test data, and the specified Swift parameters are demonstrated in Table 1. The hardening curve (Flow curve), according to the Swift law, is also given in Eq. (15).

Table 1. Swift hardening curve parameters. Material C (MPa)

p (-)

ε 0 (-) 0.011

AA6016-T4

539.7

0.247

0 (15) As for the yield surface calibration procedure, the directional variations of the r values and yield stresses are necessary. Moreover, the biaxial yield stress data is essential to define an appropriate yield locus. The yield stresses were normalized based upon the reference (rolling direction) yield stress (185.76 MPa). The parameters which are experimentally procured are presented in Table 2. Table 2. Anisotropic features of AA6016-T4 (Zhang et al. (2019)). 0 (°) 45 (°) 90 (°) Biaxial Yield stress ratio 1 0.979 0.992 1.003 r value 1.14 0.34 0.62 0.61 The other specimens having different notch shapes were utilized in tests to construct the fracture loci of the material. 4. Identification of the Yield Function and Fracture Models This section explains the calibration procedure of the HomPol4 and the acquisition of the plastic equivalent fracture strain values for fracture initiation regarding the loading paths of the notched specimens. An anisotropic yield locus representation is adopted in the FE analyses of the tensile tests to incorporate the effect of the variation in mechanical features into the fracture loci construction. 0 ( p C    = + ) p