Publications

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Predicting failure of thin-walled structures from explosive loading is a very complex task. The problem can be divided into two parts; the detonation of the explosive to produce the loading on the structure, and secondly the structural response. First, the factors that affect the explosive loading include: size, shape, stand-off, confinement, and chemistry of the explosive. The goal of the first part of the analysis is predicting the pressure on the structure based on these factors. The hydrodynamic code CTH is used to conduct these calculations. Secondly, the response of a structure from the explosive loading is predicted using a detailed finite element model within the explicit analysis code Presto. Material response, to failure, must be established in the analysis to model the failure of this class of structures; validation of this behavior is also required to allow these analyses to be predictive for their intended use. The presentation will detail the validation tests used to support this program. Validation tests using explosively loaded aluminum thin flat plates were used to study all the aspects mentioned above. Experimental measurements of the pressures generated by the explosive and the resulting plate deformations provided data for comparison against analytical predictions. These included pressure-time histories and digital image correlation of the full field plate deflections. The issues studied in the structural analysis were mesh sensitivity, strain based failure metrics, and the coupling methodologies between the blast and structural models. These models have been successfully validated using these tests, thereby increasing confidence of the results obtained in the prediction of failure thresholds of complex structures, including aircraft.

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Computational fluid dynamics simulations for dispersal of explosive vapors in interior spaces have been performed including details of typical ventilation systems. The interior spaces investigated include an office area, a single-family house, and a warehouse store. Explosive vapor sources are defined in the various interior spaces, and contours of the vapor concentration in the interior spaces relative to the source concentration are presented for relative concentrations down to 10-5. Training protocols for detection of explosive vapors in interior spaces should include an awareness of the time to equilibrium evident in these simulations as well as the significance of ventilation zones.3

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Assessing the risk of malevolent attacks against large-scale critical infrastructures requires modifications to existing methodologies that separately consider physical security and cyber security. This research has developed a risk assessment methodology that explicitly accounts for both physical and cyber security, while preserving the traditional security paradigm of detect, delay, and respond. This methodology also accounts for the condition that a facility may be able to recover from or mitigate the impact of a successful attack before serious consequences occur. The methodology uses evidence-based techniques (which are a generalization of probability theory) to evaluate the security posture of the cyber protection systems. Cyber threats are compared against cyber security posture using a category-based approach nested within a path-based analysis to determine the most vulnerable cyber attack path. The methodology summarizes the impact of a blended cyber/physical adversary attack in a conditional risk estimate where the consequence term is scaled by a ''willingness to pay'' avoidance approach.

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Military test and training ranges operate with live-fire engagements to provide realism important to the maintenance of key tactical skills. Ordnance detonations during these operations typically produce minute residues of parent explosive chemical compounds. Occasional low-order detonations also disperse solid-phase energetic material onto the surface soil. These detonation remnants are implicated in chemical contamination impacts to groundwater on a limited set of ranges where environmental characterization projects have occurred. Key questions arise regarding how these residues and the environmental conditions (e.g., weather and geostratigraphy) contribute to groundwater pollution. This final report documents the results of experimental and simulation model development for evaluating mass transfer processes from solid-phase energetics to soil-pore water.

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Assessing the risk of malevolent attacks against large-scale critical infrastructures requires modifications to existing methodologies. Existing risk assessment methodologies consider physical security and cyber security separately. As such, they do not accurately model attacks that involve defeating both physical protection and cyber protection elements (e.g., hackers turning off alarm systems prior to forced entry). This paper presents a risk assessment methodology that accounts for both physical and cyber security. It also preserves the traditional security paradigm of detect, delay and respond, while accounting for the possibility that a facility may be able to recover from or mitigate the results of a successful attack before serious consequences occur. The methodology provides a means for ranking those assets most at risk from malevolent attacks. Because the methodology is automated the analyst can also play 'what if with mitigation measures to gain a better understanding of how to best expend resources towards securing the facilities. It is simple enough to be applied to large infrastructure facilities without developing highly complicated models. Finally, it is applicable to facilities with extensive security as well as those that are less well-protected.

Vapor detection of explosives continues to be a technological basis for security applications. This study began experimental work to measure the chemical emanation rates of pure explosive materials as a basis for determining emanation rates of security threats containing explosives. Sublimation rates for TNT were determined with thermo gravimetric analysis using two different techniques. Data were compared with other literature values to provide sublimation rates from 25 to 70 C. The enthalpy of sublimation for the combined data was found to be 115 kJ/mol, which corresponds well with previously reported data from vapor pressure determinations. A simple Gaussian atmospheric dispersion model was used to estimate downrange concentrations based on continuous, steady-state conditions at 20, 45 and 62 C for a nominal exposed block of TNT under low wind conditions. Recommendations are made for extension of the experimental vapor emanation rate determinations and development of turbulent flow computational fluid dynamics based atmospheric dispersion estimates of standoff vapor concentrations.

A mine dog evaluation project initiated by the Geneva International Center for Humanitarian Demining is evaluating the capability and reliability of mine detection dogs. The performance of field-operational mine detection dogs will be measured in test minefields in Afghanistan containing actual, but unfused landmines. Repeated performance testing over two years through various seasonal weather conditions will provide data simulating near real world conditions. Soil samples will be obtained adjacent to the buried targets repeatedly over the course of the test. Chemical analysis results from these soil samples will be used to evaluate correlations between mine dog detection performance and seasonal weather conditions. This report documents the analytical chemical methods and results from the fifth batch of soils received. This batch contained samples from Kharga, Afghanistan collected in June 2003.

Military test and training ranges operate with live fire engagements to provide realism important to the maintenance of key tactical skills. Ordnance detonations during these operations typically produce minute residues of parent explosive chemical compounds. Occasional low order detonations also disperse solid phase energetic material onto the surface soil. These detonation remnants are implicated in chemical contamination impacts to groundwater on a limited set of ranges where environmental characterization projects have occurred. Key questions arise regarding how these residues and the environmental conditions (e.g., weather and geostratigraphy) contribute to groundwater pollution impacts. This report documents interim results of experimental work evaluating mass transfer processes from solid phase energetics to soil pore water. The experimental work is used as a basis to formulate a mass transfer numerical model, which has been incorporated into the porous media simulation code T2TNT. This report documents the results of the Phase III experimental effort, which evaluated the impacts of surface deposits versus buried deposits, energetic material particle size, and low order detonation debris. Next year, the energetic material mass transfer model will be refined and a 2-d screening model will be developed for initial site-specific applications. A technology development roadmap was created to show how specific R&D efforts are linked to technology and products for key customers.

Buried landmines are often detected through their chemical signature in the thin air layer, or boundary layer, right above the soil surface by sensors or animals. Environmental processes play a significant role in the available chemical signature. Due to the shallow burial depth of landmines, the weather also influences the release of chemicals from the landmine, transport through the soil to the surface, and degradation processes in the soil. The effect of weather on the landmine chemical signature from a PMN landmine was evaluated with the T2TNT code for three different climates: Kabul, Afghanistan, Ft. Leonard Wood, Missouri, USA, and Napacala, Mozambique. Results for TNT gas-phase and solid-phase concentrations are presented as a function of time of the year.

A mine dog evaluation project initiated by the Geneva International Center for Humanitarian Demining is evaluating the capability and reliability of mine detection dogs. The performance of field-operational mine detection dogs will be measured in test minefields in Afghanistan and Bosnia containing actual, but unfused landmines. Repeated performance testing over two years through various seasonal weather conditions will provide data simulating near real world conditions. Soil samples will be obtained adjacent to the buried targets repeatedly over the course of the test. Chemical analysis results from these soil samples will be used to evaluate correlations between mine dog detection performance and seasonal weather conditions. This report documents the analytical chemical methods and results from the fourth batch of soils received. This batch contained samples from Kharga, Afghanistan collected in April 2003 and Sarajevo, Bosnia collected in May 2003.

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A mine dog evaluation project initiated by the Geneva International Center for Humanitarian Demining is evaluating the capability and reliability of mine detection dogs. The performance of field-operational mine detection dogs will be measured in test minefields in Afghanistan and Bosnia containing actual, but unfused landmines. Repeated performance testing over two years through various seasonal weather conditions will provide data simulating near real world conditions. Soil samples will be obtained adjacent to the buried targets repeatedly over the course of the test. Chemical analysis results from these soil samples will be used to evaluate correlations between mine dog detection performance and seasonal weather conditions. This report documents the analytical chemical methods and results from the third batch of soils received. This batch contained samples from Kharga, Afghanistan collected in October 2002.

Military test and training ranges operate with live fire engagements to provide realism important to the maintenance of key tactical skills. Ordnance detonations during these operations typically produce minute residues of parent explosive chemical compounds. Occasional low order detonations also disperse solid phase energetic material onto the surface soil. These detonation remnants are implicated in chemical contamination impacts to groundwater on a limited set of ranges where environmental characterization projects have occurred. Key questions arise regarding how these residues and the environmental conditions (e.g. weather and geostratigraphy) contribute to groundwater pollution impacts. This report documents interim results of experimental work evaluating mass transfer processes from solid phase energetics to soil pore water. The experimental work is used as a basis to formulate a mass transfer numerical model, which has been incorporated into the porous media simulation code T2TNT. Experimental work to date with Composition B explosive has shown that column tests typically produce effluents near the temperature dependent solubility limits for RDX and TNT. The influence of water flow rate, temperature, porous media saturation and mass loading is documented. The mass transfer model formulation uses a mass transfer coefficient and surface area function and shows good agreement with the experimental data. Continued experimental work is necessary to evaluate solid phase particle size and 2-dimensional effects, and actual low order detonation debris. Simulation model improvements will continue leading to a capability to complete screening assessments of the impacts of military range operations on groundwater quality.