VICKSBURG, Miss. — The U.S. Army Engineer Research and Development Center (ERDC) has a lead role in the study of blast effects, and a newly upgraded facility allows for even more innovative research to better protect structures, facilities and most importantly, people.
From testing military helmet designs to evaluating full-scale walls and high-performance materials, the Geotechnical and Structures Laboratory’s newly updated Advanced Blast Load Simulator (ABLS) facility allows researchers to get a first-hand look at blast effects in a controlled environment at the ERDC-Vicksburg site.
ERDC previously relied on full-scale, high-explosive field testing to investigate blast response issues; however, those large experiments are very costly and time-consuming. Dr. Carol Johnson, research civil engineer with the Geotechnical and Structures Laboratory, is responsible for designing and executing the experiments within the ABLS facility.
“The Blast Load Simulator (BLS) devices are more efficient and economical for testing rather than going out to the field. Here in Vicksburg, we can conduct more research and gather data at a faster rate with significantly reduced costs,” said Johnson. “We can then confirm a final design and take it out to the field to get validation.”
The facility simulates explosive devices detonating at a certain distance from a target. Research engineers can replicate the air blast associated with that particular explosive event and from the results can understand the capacity of a structure, the response of buildings or how to better retrofit structures.
The original BLS is a compressed gas driven device with a pressure vessel on the front end. Research engineers pump air and helium into the pressure vessel and use steel and aluminum diaphragms to confine the gases. While under pressure, a mechanical striker impacts the diaphragms and forces them to rip and rupture. The blast wave then travels down the expansion cone, through the rings and hits the target at the far end. After the blast wave impacts the target, it rebounds and travels back through the rings and vents out of the gaps of the BLS.
“New components were recently added to the BLS to expand the target size of 71 inches by 53 inches to a maximum target size of eight feet by eight feet. The largest experiment conducted in the original BLS replicated a maximum pressure and impulse combination of 55,000 pounds of TNT roughly 120 feet away from the target,” said Johnson.
“The BLS is about 20 years old, so the new ABLS devices take advantage of a new patent and technological developments in this area. Due to target size limitations in the BLS, we've had to evaluate individual components in our experiments instead of testing full-scale targets. The new Advanced Blast Load Simulator allows us to conduct full-scale testing within minutes as opposed to hours,” said Johnson.
The new ABLS is a combustible gas driven device with a booster chamber on the front end. Research engineers fill the booster chamber with a fuel/air mixture and then detonate it causing a “fireball” effect. Oxyacetylene is used and initiated with an electric match. Once initiated, the shock wave from the booster detonates the ethylene and air behind it and sends the blast wave towards the target. The ABLS has a louver system on top that opens when detonated which eventually releases the blast wave after it impacts the target.
One type of target tested is fully reflected and typically consists of windows, walls and doors. The other type is referred to as diffraction/engulfment experiments, which means a blast wave is sent towards an object and researchers study how the blast propagates around that target. An example of a diffraction experiment would be placing a mannequin in the target space and testing for traumatic brain injury or personal vulnerability.
“The ABLS can hold a maximum target of 14 feet by 14 feet, and being able to conduct full-scale testing allows us to expand our knowledge base,” Johnson explained. “The ABLS has increased our performance envelope because we have the ability to conduct very low reflected pressure experiments required for personal vulnerability research and higher reflected pressure experiments required to evaluate blast designed structural elements – all in one device.”
For example, multiple mannequins, each with different protective equipment, can be tested simultaneously. They can be rotated at different angles to see the various results. Even an entire wall system with blast-designed window and door framing can be evaluated in a singular experiment within the ABLS.
“If customers bring in something that can fit in the space of one of these target vessels, we can and will shoot it for you,” Johnson said, highlighting the versatility of the ABLS.
The facility also includes a functional, smaller prototype of the ABLS that can support a target size of four feet by four feet and is generally used for testing new helmet designs, hearing protection or new high-performance material samples. All of the simulators can be operated daily with testing starting small and advancing to larger experiments which can be more efficient and economical than field evaluation. The data generated from the BLS and ABLS experiments is transitioned to ERDC engineers and researchers to validate and develop new numerical models for blast protection.
“The work we do here helps us better protect our structures, facilities, and our Soldiers,” said Johnson. “ERDC makes a huge difference in not only protecting our Warfighters but also making our Nation and our world safer and better.”