Shock and Blast Wave Testing
Shock Wave Engineering has extensive experience measuring the effect of shock and blast waves on structures and this is obviously the origin of the company name. The shock waves can either be generated in a laboratory environment using a shock tube or by using explosive charges on a bomb range. Highly specialized instrumentation, signal conditioning, and data acquisition systems are required for measuring such high speed transients.
Shock Tubes are useful for producing highly repeatable shock waves in a very cost effective manner. The figure below shows a sphere placed in a shock tube. The purpose of the testing was to determine the drag on the sphere as a shock wave passed over the sphere. Pressure transducers are used to determine the shock strength. Some results are shown in here.
A very simple rapidly opening (1 millisecond) valve has been developed for use in shock tubes. More details of the valve are given here.
Explosive charges are useful when large scale tests are required. The figure below shows a typical Explosive Ordinance Disposal (EOD) suit test. The suit is on a dummy in a standing position 3 m from a 5 kg Pentolite charge. There are a number of pressure transducers measuring the pressure inside and outside the suit. There are also accelerometers to measure the head acceleration. Part of the challenge of the testing is ensuring that sensitive instrumentation, cables, and data acquisition systems are not damaged by the blast. The data acquisition system is placed about 20 m from the blast. A special cable has been developed to transmit the transducer signals from the suit to the data acquisition system. To the left of the explosive charge a Free Field Blast Probe can be seen. The probe measures the static pressure generated by the blast and is used as a control between blasts.
The photo above gives an indication of the energy released during a blast.