PSI - Issue 8

V. Dattoma et al. / Procedia Structural Integrity 8 (2018) 444–451 Author name / Structural Integrity Procedia 00 (2017) 000–000

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Fig. 3. Transversal section of wrinkled specimens: (a) 50-33-24-WD10; (b) 50-33-24-WD20; (c) 50-33-24-WD40; (d) 17-67-24-WD10; (e) 25 50-16-WD10.

2.2. Test methods

Mechanical tests have been carried out on a servohydraulic testing machine INSTRON8850 having a load capacity of 250 kN. Each series was tested both in tension and compression on at least five specimens. Open Hole Tension tests are carried out following the indication of ASTM D5766. During test, an extensometer with a gage length of 50 mm was installed in correspondence of the middle section. Open Hole Compression tests are carried out following the indication of ASTM D6484 procedure B. In particular the test fixture reported in the standard has been used to avoid the specimen instability. After the specimen assembly procedure, the fixture has been positioned between two load plates fixed to the grip of testing machine. In order to assure the correct alignment of the specimen along the load train of the testing machine, the plates are equipped with an adaptable alignment system constituted by two screw acting on the external surface of the fixture. In this manner, even during the test,