PSI - Issue 37

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Pedro J. Sousa et al. / Procedia Structural Integrity 37 (2022) 826–832 Sousa et. al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Nomenclature ADC Analog-to-digital converter DAQ Data acquisition DIC Digital image correlation

GPIO General purpose input/output SHPB Split Hopkinson pressure bar UART Universal asynchronous receiver-transmitter

1.1. Control setup The first step in the development of this control system was the definition of the necessary inputs, outputs and interfaces, summarized in the schematic of Fig. 3. The main control loop requires a pressure sensor with analogue output, as well as the different solenoid-controlled valves, thus being capable of firing the mechanism at a user-defined pressure, set from a computer using a custom interface software.

Fig. 3. Schematic of the final assembly of the Split Hopkinson Pressure bar, with the developed controller

The output signals are then used to feed the DAQ, the high-speed camera and, optionally, an illumination source. Thus, the DAQ is responsible for acquiring not only these output signals, but also the previously mentioned strain curves, which results in synchronized signals similar to the ones shown in Fig. 4. If necessary, an additional single usage strain gauge on the specimen may also be used, which simplifies the data extraction.