PSI - Issue 17

Pranav S. Patwardhan et al. / Procedia Structural Integrity 17 (2019) 750–757 Author name / Structural Integrity Procedia 00 (2019) 000 – 000 In Eq. (14), both constants c and a are functions of the true plastic yield/Luder’s strain, − , as it is shown in Fig. 3. Now, the N values for a given material can be calculated using Eq. (14) together with the corresponding true plastic yield/Luder’s strain at the end of the plateau , − . 753 4

As can be seen from various experimental stress-strain curves depict in Fig. 4, that some materials show a plateau at yielding, where applied stress remains almost constant whereas associated Luder’s strain increases. This maximum value of th e plastic Luder’s strain would be used in estimation of the strain hardening exponent, N . Fig. 3. Graphs of a and c in Eq. (14) for different plastic yield strain value, ε py .

0 100 200 300 400 500 600 700

0 100 200 300 400 500 600 700 800 900

(a)

(b)

 p-L = 0.0061

 p-L = 0.0143

SM490 Kamaya (2016)

SQV2B Kamaya (2016)

Experimental Ramberg-Osgood fit Estimated

Experimental Ramberg-Osgood fit Estimated

True Stress,MPa

True stress, MPa

0

0.05

0.1

0.15

0.2

0

0.05

0.1

0.15

True Strain

True strain

0 100 200 300 400 500 600 700

0 100 200 300 400 500 600 700 800 900

(c)

(d)

STS 370 Kamaya (2016)

S45C Kamaya (2016)

 p-L = 0.0106

Experimental Ramberg-Osgood fit Estimated

Experimental Ramberg-Osgood fit Estimated

True stress, MPa

True Stress, MPa

0

0.05

0.1

0.15

0.2

0

0.05

0.1

0.15

0.2

True strain

True Strain

Fig. 4. (Cont.)