PSI - Issue 5

Sahand Pourhassan et al. / Procedia Structural Integrity 5 (2017) 1355–1362 Sahand Pourhassan et al./ Structural Integrity Procedia 00 (2017) 000 – 000

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The summary of the experiments are included in Table 1. Both geometries for flat specimens made from 2024-T3 Al were manufactured along the rolling direction. 5 experiments were conducted for each geometry and 2D-DIC system with a Qioptiq Rodagon 60mm lens and 4MP camera was used to trace the applied speckle patterns on specimens. While, cylindrical specimens from 2124-T851 Al were all measured using 3D-DIC with the same lenses. For sharp focus on cylindrical specimens and convenient calibration process, depth of field was slightly increased using smaller aperture f/8 and exposure time of 12ms during 3D DIC experiments. Besides image correlation, clip-on extensometer with a gauge length of 50mm was used (only for standard specimens) for confirmation purposes.

Table 1. Summary of experiments Material

Specimen geometry- gauge length (mm) ASTM Standard (60)

No. experiments

velocity of crosshead (mm/min)

Displacement measurement 2D-DIC and extensometer

5

3.6

Al 2024-T3 ALCLAD

Non-standard (20)

5

1.2

2D-DIC

ASTM Standard (60)

5

3.6

3D-DIC and extensometer

Al 2124-T851

Non-standard (20)

5

1.2

3-DIC

2.2. Test setup

Figure below shows the designed gripping system used to test 2024-T3 aluminum alloy. The same gripping system (without the machine adapter) could also be used in Split Hopkinson Tension Bar (SHTB) setup.

Fig. 3. Designed gripping system used to test non-standard specimens

DIC setup used during experiments are as following: Camera : 4.1 MPixel at 150Hz Image sensor : CMOSIS CMV4000 CMOS, 1”, 5.5x5. 5 μ m 2 Resolution : 2048×2048 at 150 fps, Partial Image Modes: single or multiple region of interest Lens : Rodagon 60mm f/4 from Qioptiq with 48 mm extension Lighting system : Hedler 250 Spotlight

The camera´s image sensor was placed 400mm away from the specimen during 2D-DIC measurements. While in 3D DIC, cameras were 600mm away from cylindrical test specimen with stereo angle of 24°. Considering the brightness