PSI - Issue 21

Tuncay Yalçinkaya et al. / Procedia Structural Integrity 21 (2019) 52–60 Yalc¸inkaya et al. / Structural Integrity Procedia 00 (2019) 000–000

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7

corresponds to the moment at which the specimen carries the highest load. Initial pore fraction is taken as 0.05, 0.1 and 0.2 for the figures in column 1, 2 and 3 respectively. It can be seen that for higher initial pore fraction values, the specimen’s stress carrying capacity reduces and the maximum stress magnitude gets smaller. This is also related to the fact that the crack propagation occurs earlier for the higher initial pore fraction values.

Force vs Displacement

Force vs Displacement

7

7

h 0 =0.1, f 0 =0.05 h 0 =0.1, f 0 =0.1 h 0 =0.1, f 0 =0.2

h 0 =0.1, f 0 =0.2 h 0 =0.15, f 0 =0.2 h 0 =0.2, f 0 =0.2

6

6

5

5

4

4

3

3

Force [N]

Force [N]

2

2

1

1

0 0.005 0.01 0.015 0.02 0.025 Displacement [mm] 0

0 0.005 0.01 0.015 0.02 0.025 Displacement [mm] 0

Fig. 7. Force-displacement response for constant h 0 , and changing f 0 (left), and for constant f 0 , and changing h 0 (right)

Similar conclusions can be obtained from the load displacement curves presented in Fig. 7. For the cases with higher porosity the maximum stress gets smaller and the sudden drop in stress carrying capacity is observed at an earlier global strain level. Additionally, toughness of the specimen reduces with higher initial pore fraction.

(Avg: 75%) S, Mises

(Avg: 75%) S, Mises

(Avg: 75%) S, Mises

0.000 35.417 70.833 106.250 141.667 177.083 212.500 247.917 283.333 318.750 354.167 389.583 425.000

0.000 35.417 70.833 106.250 141.667 177.083 212.500 247.917 283.333 318.750 354.167 389.583 425.000

0.000 35.417 70.833 106.250 141.667 177.083 212.500 247.917 283.333 318.750 354.167 389.583 425.000 446.178

Y

Y

Y

Z

X

Z

X

Z

X

(Avg: 75%) S, Mises

(Avg: 75%) S, Mises

(Avg: 75%) S, Mises

0.000 35.417 70.833 106.250 141.667 177.083 212.500 247.917 283.333 318.750 354.167 389.583 425.000

0.000 35.417 70.833 106.250 141.667 177.083 212.500 247.917 283.333 318.750 354.167 389.583 425.000

0.000 35.417 70.833 106.250 141.667 177.083 212.500 247.917 283.333 318.750 354.167 389.583 425.000

Y

Y

Y

Z

X

Z

X

Z

X

Fig. 8. Stress distributions at the same time increment for di ff erent initial pore fractions

The e ff ect on ductility can be observed in Fig. 8, where distributions are shown at the same time increment. For the same global displacement the crack propagates more for higher pore fraction which can also be seen in 7a. Therefore,