PSI - Issue 28

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Ezio Cadoni et al. / Procedia Structural Integrity 28 (2020) 933–942 Author name / Structural Integrity Procedia 00 (2020) 000–000

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Fig. 2. FEM analysis on two for direct shear test configurations.

Fig. 3. FEM analysis on three di ff erent notches for selected direct-shear test configuration.

The shear specimen consists of two coaxial cylindrical parts jointed at the basis through a thin circular crown which represents the gauge part of the specimen. The thin circular crown is built up by coring the specimen with diameter 60mm with a coring tool with circular crown having inner diameter of 30mm. The di ff erence between the outer diameter of the smaller cylindrical part and the inner diameter of the larger remaining cylindrical part is the considered shear zone.

3.2. High strain-rate testing set-up

The experimental set-up used for direct-shear test (see Fig. 4) at high strain rate is based on the compression set up described in [Bragov et al. (2015); Cadoni et al. (2009)]. The unique modification is at the specimen level.With reference to Fig. 4, the hydraulic actuator (1) pulls the pretensioned steel bar (2) thanks to the blocking device (3). The the input bar (4) and the output bars (7) have 30mm of diameter and made of aluminium alloy 7075, both are instrumented with semi-conductor strain gauges stations (5). The sample (6) is sandwiched between input and output bars with special connector as described in upper left part of Fig. 4. The actual shear specimen has been designed following the previous optimisation study with a short gauge length between 5 and 15mm which permits to achieve homogeneous stress distribution in the gauge part also in case of testing at high strain rate by means of stress wave propagation and reflections inside the gauge length.