PSI - Issue 21

Serhat Onur Çakmak et al. / Procedia Structural Integrity 21 (2019) 224–232 Serhat Onur C¸ akmak, Tuncay Yalc¸inkaya / Structural Integrity Procedia 00 (2019) 000–000

231

8

the higher martensite content case the di ff erence in the amount of accumulated plastic shear is visible rather than the location.

(Avg: 75%) SDV109

(Avg: 75%) SDV109

(Avg: 75%) SDV109

(Avg: 75%) SDV109

1.054

0.665

0.721

0.603

0.017 0.075 0.133 0.192 0.250 0.308 0.367 0.425 0.483 0.542 0.600

0.025 0.067 0.108 0.150 0.192 0.233 0.275 0.317 0.358 0.400

0.012 0.050 0.087 0.125 0.162 0.200 0.237 0.275 0.312 0.350

0.010 0.053 0.097 0.140 0.183 0.227 0.270 0.313 0.357 0.400

−0.100 −0.058 −0.017

−0.100 −0.063 −0.025 −0.134

−0.120 −0.077 −0.033

−0.100 −0.042

Y

Y

Y

Y

Z

X

Z

X

Z

X

Z

X

(a)

(b)

(c)

(d)

(Avg: 75%) SDV109

(Avg: 75%) SDV109

(Avg: 75%) SDV109

(Avg: 75%) SDV109

0.704

0.767

0.629

0.467

0.025 0.067 0.108 0.150 0.192 0.233 0.275 0.317 0.358 0.400

0.017 0.075 0.133 0.192 0.250 0.308 0.367 0.425 0.483 0.542 0.600

0.010 0.053 0.097 0.140 0.183 0.227 0.270 0.313 0.357 0.400

0.012 0.050 0.087 0.125 0.162 0.200 0.237 0.275 0.312 0.350

−0.100 −0.058 −0.017

−0.120 −0.077 −0.033

−0.100 −0.063 −0.025

−0.100 −0.042

Y

Y

Y

Y

Z

X

Z

X

Z

X

Z

X

(e)

(f)

(g)

(h)

Fig. 7: The accumulated plastic shear strain at the onset of necking for di ff erent volume fraction and initial orientation sets (a-d) oriset1, (e-h) oriset2 and (a,e) VF15, (b,h) VF19, (c,g) VF28, (d,h) VF37.

5. Conclusions

The micron size specimens of di ff erent DP steels are investigated numerically through J2 plasticity and crystal plasticity theories for martensite and ferrite phases respectively. The attention is focussed on the localization and necking phenomena for specimen under uniaxial loading conditions. The e ff ect of martensite grain distribution and initial ferrite grain orientation distribution is discussed in detail. The main conclusions are as follows, • The location of the necking depends highly on the martensite distribution in micron sized specimen no matter what the volume fraction of the martensite is. The di ff erence is also visible in the softening regime of macro scopic stress-strain responses, which becomes pronounced in the case with higher martensite volume fractions. • The ferrite orientation distribution a ff ects primarily the necking behavior of specimens with low martensite content in terms of both the necking location and the softening regime in stress-strain response. • The shear band formation in the necking region depends also on the orientation distribution in the case with low martensite content which is consistent with the necking location.