PSI- Issue 9

Ch.F. Markides et al. / Procedia Structural Integrity 9 (2018) 108–115 Author name / Structural Integrity Procedia 00 (2018) 000–000

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vely brittle and the initial portion of its stress-strain curve is almost perfectly linear, in accordance with the assumptions adopted for the analysis. The mechanical properties and constants were determined by means of standardized uniaxial tests. The modulus of elasticity was found equal to E=3.0 GPa and Poisson’s ratio equal to ν=0.38. The specimens were shaped according to Fig.1b with 2h=0.01m, R 2 =0.05m, r=R 2 /R 1 =2 (Fig.2a). The eccentricity was set equal to c=R 2 /8. The load was imposed with the aid of a 10 kN electromechanical ΜΤS-Insight frame, and the displacement field was measured by means of a 3D-Digital Image Correlation (DIC) system (Limess). For this purpose one of the lateral surfaces of the specimens was painted white and an arbitrary black speckle pattern was sprayed on it, according to the requirements of the DIC technique. The experimental set-up can be seen in Fig.2b. (a) (b)

Fig. 2. (a) A typical specimen while loaded; (b) The overall experimental set-up.

The experiments were carried out under quasi-static conditions and displacement-control mode at a rate equal to 0.1 mm/min. During loading, successive photos of the specimens were taken at predefined time steps (one photo every four seconds). The raw data were then appropriately elaborated and the distribution of the three dimensional displace ment field all over the specimen’s surface was obtained. A typical fractured specimen is shown in Fig.3a while a characteristic picture, provided by the DIC system, is shown in Fig.3b, in which the horizontal displacement component u x , in the central position of a typical specimen, is shown for a load level equal to about 0.3 kN. (a) (b) .

Fig. 3. (a) A typical fractured specimen; (b) The horizontal displacement component as determined by the DIC system.