PSI - Issue 21

10

Tuncay Yalçinkaya et al. / Procedia Structural Integrity 21 (2019) 61–72 T. Yalc¸inkaya et al. / Structural Integrity Procedia 00 (2019) 000–000

70

(Avg: 75%) S, Pressure

17359

1333 2000 2667 3333 4000

−4000 −3333 −2667 −2000 −1333 −667 0 667 −14563

(a)

(b)

(c)

(d)

(Avg: 75%) LE, Max. Principal

0.00 0.04 0.07 0.11 0.15 0.19 0.22 0.26 0.30 0.34 0.37 0.41 0.45 0.48

(e)

(f)

(g)

(h)

Fig. 8: Pressure (a-d) and logarithmic strain (e-h) distributions of DP4 at E eq = 0.1 obtained for triaxiality values 0.5 (a,e), 1 (b,f), 1.5(c,g) and 3 (d,h).

4. Conclusions

Di ff erent DP steels are investigated at RVE level through both crystal plasticity and J2 plasticity theories. The RVEs are subjected to axisymmetric tensile loadings while keeping the value of stress triaxiality constant. The main conclusions are as follows, • Although elastoplastic and crystal plasticity simulations both give a satisfactory and similar overall behaviour, the latter method is able to capture stress partitioning and strain localizations better. Moreover crystal plasticity simulations result in higher local stresses due to orientation mismtach at the ferrite GBs which does not occur in elastoplastic calculations. • Regardless of the constitutive model, ductility decreases with increasing martensite volume fraction. DP steels with a high V m value have higher strengths at the expense of ductility. • The density of void nucleation regions increase with increasing T . High local T values are observed at sharp martensite ends, and at ferrite-ferrite grain boundaries which are in the neighbourhood of martensite islands. • Ferrite goes into plastic regime earlier than martensite. Martensite islands block the plastic deformation in ferrite, and therefore cause high T values at grain boundaries.

References

Al-Rub, R.K.A., Ettehad, M., Palazotto, A.N., 2015. Microstructural modeling of dual phase steel using a higher-order gradient plasticitydamage model. International Journal of Solids and Structures 58, 178 – 189. doi: https://doi.org/10.1016/j.ijsolstr.2014.12.029 . Amirmaleki, M., Samei, J., Green, D.E., van Riemsdijk, I., Stewart, L., 2016. 3d micromechanical modeling of dual phase steels using the representative volume element method. Mechanics of Materials 101, 27–39. doi: 10.1016/j.mechmat.2016.07.011 . Avramovic-Cingara, G., Ososkov, Y., Jain, M., Wilkinson, D., 2009. E ff ect of martensite distribution on damage behaviour in dp600 dual phase steels. Materials Science and Engineering: A 516, 7 – 16. doi: https://doi.org/10.1016/j.msea.2009.03.055 .