PSI - Issue 21

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

67 7

1200

1000

800

600

eq (MPa)

DP1−15% FEM results DP2−19% FEM results DP3−28% FEM results DP4−37% FEM results

400

DP1−15% experimental results DP2−19% experimental results DP3−28% experimental results DP4−37% experimental results

200

0

0

0.05

0.1

0.15

0.2

E eq

Fig. 4: Comparison of J2 plasticity based RVE calculations with the experimental data up to necking.

ductility and highest strain hardening (see e.g. Uthaisangsuk et al. (2011) for similar observations). The strain contour plots show rather large bands throughout the ferrite phase, which contradicts with the 2D RVE studies in the literature, that mention the occurrence of narrow bands (see e.g. Paul (2012); Al-Rub et al. (2015)). On the other hand, similar results are reported in the studies focussing on 3D RVEs (see e.g. Amirmaleki et al. (2016)). Strain localization occurs in ferrite region located between the two sharp ends of martensite and sharp ends of martensite as discussed in Kad khodapour et al. (2011b). Very small strain values are obtained in martensite particles of DP1, DP2 microstructures. Some thin martensite-martensite interfaces in DP3, DP4 microstructures show high strain values. Such deformation patterns is usually seen in high martensite volume fractions(Vm > 32%) according to the in situ scanning electron microscopy tests conducted by Ghadbeigi et al. (2013).

(Avg: 75%) S, Mises

1181 1373 1564 1755 1946 2138 2329 2520 3989

225 416 608 799 990

(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 0.84

Min: +2.693e−003

(e)

(f)

(g)

(h)

Fig. 5: Stress (a-d) and strain (e-h) contours (J2 theory) for DP1 (a,e), DP2 (b,f) ,DP3 (c,g) and DP4 (d,h) at E eq = 0 . 12.