The Photodyn project proposes an alternative to the well-known Split Hopkinson Pressure Bar (SHPB) apparatus to identify the high strain rate behaviour of materials. The idea is to perform inertial impact tests using a gas gun system attached to an impact chamber where imaging of the specimen response will be performed using an ultra-high speed camera.

The gas gun has been designed to be capable of impact speeds up to 100 m/s for an aluminium projectile of mass 0.44 kg (impact energy of 2.2 kJ). The barrel of the gas gun is 3 m long and has a 50 mm bore. The pressure reservoir uses compressed air as a working fluid, has a volume of 12 L and a maximum working pressure of 20 bar. The firing valve is a solenoid valve with a 2″ port and a max opening time of 200 ms. The test section has optical access on both sides and is capable of mounting specimens up to 220 x 220 x 220 mm.

Principle of the gas gun

Click on the image for an animation of the principle of the gas gun

Full CAD assembly model of PhotoDyn impact rig

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Full design specification and CAD drawings for the gas gun can be provided on request.

The authors would like to thank the following University of Southampton group design project students: Olivia Fan-Barrett, Joseph Perry, Matthew Leng, Keller Waud and Alexander Conway who produced the initial concept design of the gas gun detailed in this paper.