Fundamental Measurements of Landmine Blast Loading, 18-R9841

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Principal Investigators
Scott A. Mullin
James T. Mathis
Joseph H. Bradley
Mark A. Griffin
Erick J. Sagebiel
Carl E. Weiss
P.A. Cox

Inclusive Dates:  07/01/08 – 07/01/09

Background - The objective of this project was to develop the means to more accurately study the response of armored vehicles or armor materials subjected to close proximity landmine explosions. This is an area of much active U.S. Department of Defense research, because of the wide proliferation of buried improvised explosive devices (IEDs) and landmines in conflict areas around the world. There is a need for lightweight, somewhat nimble, military vehicles in urban environments, and these types of vehicles are vulnerable to landmines and similar types of loads.

Approach - Several different, complementary approaches were undertaken to develop and extend SwRI's in-house capability. These included: 1) developing instrumentation methodology; 2) developing test fixtures that are representative and provide repeatable results; 3) performing and verifying sub-scale testing analyses and approach to testing; and 4) developing an improved computational simulation methodology. This project was also conducted as a "learning platform" where junior staff members were given the opportunity to conduct the majority of the research under senior staff guidance.

Accomplishments - In the area of high-rate, high g-loaded gauge technology, SwRI made significant advancement. A calibration fixture was designed and constructed, and using it and the knowledge gained from the blast experiments, the project team understood the characteristics required for the proper gauges, how to best install them to insure their survival and provide high rates of data return, and how to post-process the data to separate the structural response from the many layers of interference. Significant progress was made in this area, and the project team now has the knowledge and experience to instrument these types of tests as well as the best in the field. A rugged test fixture was designed and constructed that allows for testing of different sizes of armor panels with alternative edge constraints (bolting, clamping). The fixture was outfitted with a HMMWV seat to demonstrate the capability to measure loads imparted to personnel. This fixture is now an Institute resource that can be used for future projects. A companion fixture was also designed that holds the instrumentation and cabling and mates to the landmine test fixture. The team developed a test methodology that reduces the variability of the soil loading. Typical landmine tests require a large sandpit that has to be changed for each test. A much smaller explosive / sand holder was designed using inexpensive concrete tubes that greatly simplified the test approach. This approach was verified through experimental tests. This is a unique approach in the field. Small-scale tests offer the potential to greatly reduce costs associated with testing, but are only useful if the results can be extrapolated accurately to full scale. The project team analyzed the approach in detail and designed the test matrix to provide results to verify the utility of scaling. The analyses indicated the approach was sound, and the experimental results verified this conclusion. There are several facets to the computational approach that were studied and enhanced during this project. A method to link two separate codes (CTH and LS-DYNA) to model the different elements of load application and structural response was developed. The method proved to be a significant advance over previous techniques. Advanced soil models were investigated and implemented in the analyses. The simulations were compared to the experimental results and the correlation was excellent. Overall, all the goals of the project were met, and SwRI now has a demonstrated capability and hardware in hand that puts it at the forefront of this technology. The experimental and computational approaches developed during this project have been used as key parts of five proposals for future work. The team wrote three abstracts for conferences where aspects of the research were presented to the armor and vehicle community, further enhancing SwRI's reputation and hopefully leading to future projects.

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