Testing and computational analysis of pressure transducers in water filled tank impacted by hypervelocity projectile

The experimental and computational results of a steel sphere impacting a water filled cylinder are presented here. The focus of the experiments was the measurement of shock loading in water with different gage designs. A single stage powder gun was used to launch a 1.59 cm diameter steel sphere at a nominal speed of 2.4 km/s into a water filled cylinder. There were five test shots with the same nominal impact conditions and different internal pressure gage arrangements. Three different pressure gages made by a pressure transducer manufacturer were used to measure the shock: a conventional tourmaline gage (Tygon), a chemically resistant tourmaline gage variant (PTFE), and a quartz gage that is typically used to measure shocks in gases. The tourmaline gage was first developed by the Navy in 1982 to measure underwater blast and has been used successfully in that environment. In more recent experiments, Tygon tourmaline gages have been used to accurately measure the pressure of water during high speed impacts. However, the Tygon tourmaline gage is unusable in tributyl phosphate (TBP). Using the Tygon tourmaline gage as a reference, the performance of the PTFE tourmaline gage, and the quartz crystal gage was assessed. Computational results from CTH simulations aided in test design and pressure gage placement. The computational results from a pretest calculation under predicted the pressures from the Tygon tourmaline gage. This discrepancy was attributed to shock asymmetry and a CTH calculation which purposefully introduced asymmetry matched the test data more closely. The PTFE tourmaline gage consistently showed a reasonable match to the Tygon tourmaline gage. The PTFE tourmaline gage also displayed direction insensitivity. The pressure data from the quartz gage was consistently higher than the pressure data from the Tygon tourmaline gage.