PSI - Issue 28

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Cristina Vălean et al. / Procedia Structural Integrity 28 (2020) 1134–1139 V ă lean/ Structural Integrity Procedia 00 (2019) 000–000

1137

( y

)

0.0 1.0 2.0 3.0 4.0 5.0 6.0

2.5

2.0

3D printed Milled

1.5

3D printed Milled

1.0

Load [kN]

Load [kN]

0.5

0.0

0.0

0.5

1.0

1.5

2.0

(b)

(a)

0.0

1.0

2.0

3.0

4.0

Displacement [mm]

Displacement [mm]

Fig. 3. Typical load – displacement curves: (a) Symmetric four point bending; (b) Asymmetric four point bending.

Quasi-brittle behavior was observed during testing with an abrupt decrease of force after reaching the maximum load value, particularly for the asymmetric four point loading case. 3. Results The maximum load P max determined from the load-displacement curves was used to calculate the fracture toughness. The fracture toughness of the two loading cases were determined according to Murakami (1987): - for mode I: �� � �√ ∙ � � � � � (1) with � � � � ��� � � (2) � � � � � � ����� � ����� � � � � � ���� � � � � � � ������ � � � � � � ����� � � � � � � ����� � � � � � (3) where a , B , W are the specimen’s dimensions. - for mode II: ��� � �√ ∙ �� � � � � (4) where � � � � � (5) � � � ��� � � �� � � � �� � (6)