PSI - Issue 5

M. Freitas et al. / Procedia Structural Integrity 5 (2017) 659–666 R. Baptista/ Structural Integrity Procedia 00 (2017) 000 – 000

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longer be acceptable, because the difference between the stress level on the specimen center and on the specimen arms is no longer higher than 20%.

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

1000

300

a)

c)

b)

100

1 R m /t.tt [mm/mm 2 ] 10 100

f 2 (x)

y = 70.497x -0.611 R² = 0.9915

y = 64.301x -0.986 R² = 0.9996

10

0.1 Maximum Stress[MPa/kN] t.tt [mm 2 ] 1

0.1

1

10

10

0

100

200

300

t.tt [mm 2 ]

f 1 (x)

1000

1000

100

f)

e)

d)

100

10

1 r m /t.tt [mm/mm 2 ] 10 100

0.1 rr/t.tt [mm/mm 2 ] 1

 /t.tt [  /mm 2 ]

10

y = 66.278x -1.013 R² = 0.9153

y = 8.086x -0.947 R² = 0.992

y = 22.332x -0.971 R² = 0.9853

1

0.1

1

10

0.1

1

10

0.1

1

10

t.tt [mm 2 ]

t.tt [mm 2 ]

t.tt [mm 2 ]

1000

10

10

g)

i)

h)

0.1 k/t.tt [mm/mm 2 ] 1

10 dd/t.tt [mm/mm 2 ] 100

0.1 h/t.tt [mm/mm 2 ] 1

y = 0.7158x -1.002 R² = 0.9997

y = 52.79x -0.978 R² = 0.9997

y = 0.4099x -1.022 R² = 0.9875

0.01

1

0.01

0.1

1

10

0.1

1

10

0.1

1

10

t.tt [mm 2 ]

t.tt [mm 2 ]

t.tt [mm 2 ]

Fig. 3 a) Pareto Fronts obtained for all optimization series; b) Maximum stress level; c) to i) Design variables as a function of ( ∙ ) . As for the value of the minor elliptical fillet radius , this design variable is proportional to the difference between the stress level on the specimen center and the specimen arms, both on the inner and outer parts. Increasing the value of 4 %, increases these differences by 2%. The influence of on the stress level is negligible. Finally, the position of the elliptical fillet center is inversely proportional to the maximum stress level on the specimen center and directly proportional to the difference between the stress level on the specimen center and the specimen arms. Increasing the value of by 2 %, decreases the stress value by 17 % and increases the stress differences by 3.5 %. Therefore it is safe to increase the value of and , without jeopardizing the specimen geometry, at the expanse of decreasing the stress level on the specimen center. It is also noteworthy that the elliptical