PSI - Issue 28

Ezio Cadoni et al. / Procedia Structural Integrity 28 (2020) 964–970 Author name / Structural Integrity Procedia 00 (2020) 000–000

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Fig. 1. Quasi-static stress versus strain curves.

Fig. 2. Signals from a high strain-rate test.

and 6 m, respectively (Cadoni et al. (2016); Singh et al. (2013)). The first 6 m of the longer bar is used as a pretensioned bar and the other 3 m as input bar. The second bar is entirely used as output bar. The cylindrical sample is screwed into input and output bars. The testing velocity is governed by the amplitude of the stress of the pretensioned bar obtained by pulling it with a hydraulic actuator. The input and output bars are instrumented with semiconductor strain gauges which measure the incident ( I ), reflected ( R ) and transmitted ( T ) pulses acting on the cross section of the specimen. The tests is performed as follows: • firstly, a hydraulic actuator (having maximum loading capacity of 600 kN) pulls the first 6m of the input bar (pretensioned bar), the pretension in this bar is sustained by the blocking device, • secondly, by loading with another hydraulic actuator directly connected with the blocking device, the fragile bolt of the theta clamp system suddenly breaks giving rise to a tensile mechanical pulse of 2.4 ms duration with linear loading rate during the rise time (30 µ s), propagating along the input and output bars bringing to fracture the specimen, • finally, the measurement of I , R and T pulses are obtained by the semi-conductor strain-gage station glued on the input and output bars as shown in Fig. 2.