PSI - Issue 8

J. Srnec Novak et al. / Procedia Structural Integrity 8 (2018) 174–183 Author name / Structural Integrity Procedia 00 (2017) 000–000

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The results obtained with the accelerated models are now described. Stabilization can be reached faster by increasing the original value of parameter b . The increased speed of stabilization is called b a (accelerated). In this study, 6 cases with different b a were studied. In the first case, a value of b a that is 10 times higher than the original one was considered, then b a values respectively 20, 30, 100, 200 and 300 times higher were also used. Only hoop stress strain evolution for the first five cycles and for the stabilized one are presented, see Fig. 6. For low values of b a (10÷30), see Fig. 6a-c, stress-strain evolution is similar to the combined model. On the other hand, when b a is high (100÷300), material is forced to stabilize within few cycles; see Fig. 6d-f.

N=1-5 N stab =212

N=1-5 N stab =81

150

150

100

100

50

50

0

0

σ θ (MPa)

σ θ (MPa)

-50

-50

-100

-100

b a =10 b

b a =20 b

-150

-150

a)

b)

-0.25

-0.2

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-0.1

-0.05

0

-0.25

-0.2

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-0.05

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ε θ (%)

ε θ (%)

N=1-5 N stab =95

N=1-5 N stab =39

150

150

100

100

50

50

0

0

σ θ (MPa)

σ θ (MPa)

-50

-50

-100

-100

b a =30 b

b a =100 b

-150

-150

c)

d)

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-0.05

0

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ε θ (%)

ε θ (%)

N=1-5 N stab =43

N=1-5 N stab =36

150

150

100

100

50

50

0

0

σ θ (MPa)

σ θ (MPa)

-50

-50

-100

-100

b a =200 b

b a =300 b

-150

-150

e)

f)

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0

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ε θ (%)

ε θ (%)

Fig. 6. Hoop stress-strain evolution for different types of accelerated models.

Fig. 7 shows the maximum von Mises stress evolution up to stabilization for the combined and accelerated models. In order to emphasize the differences among the models occurring in first cycles, the N values of each curve are normalized with respect to the corresponding number of cycles to stabilization, N stab . Despite the different values of N stab , the zoom view shows that, at stabilization, all models reach almost the same value of von Mises stress.