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Weapons Effects FRMs for Contact or Embedded detonations in Fixed Targets


OBJECTIVE: Develop innovative High-Fidelity Physics-Based (HFPB) Fast-Running Models (FRMs) for simulating the effects of weapons detonated on contact or embedded in fixed target structural materials. DESCRIPTION: Damage to fixed structures resulting from the intentional or accidental detonation of weapons upon contact or when embedded often results in hazards to nearby personnel, equipment, and structures. Currently AFRL/RWWL"s Modular Effectiveness Vulnerability Assessment (MEVA) program does not have the capability to predict these types of problems. In addition, other commercial and military organizations need FRMs that predict the structural damage and characteristics of debris generated by these events. The penetration, perforation, and breach of these structures by munitions involve multi-phase, multi-flow physics that has just recently been adequately modeled in HFPB codes. What is now required by analysts and weaponeers alike are innovative FRM methodologies that are based on these HFPB codes but can be executed without the time penalty associated with them. These users do not have the expertise or the time required to run HFPB calculations do to their need to execute hundreds, if not thousands, of these calculations in very short periods of time. Consequently, the primary requirement is to develop fast-running models based on HFPB analyses that are representative of the HFPB analyses and have an overall accuracy of 80% or better when compared to actual test data. The primary structural damage parameters of interest include hole size and shape, rebar damage, mass and velocity of the debris generated, and residual capacity of the damaged wall. The models must represent both partial and full penetration of the structural materials and the possible detonation of these weapons upon impact or after partial penetration. The key technology areas are Weapon-Target Interaction, Target Penetration, Impact & Delayed Detonation, Back Face Spalling, and Debris generation. Back face spalling of the target materials, including fragment size and velocity (vector) distributions are of interest, particularly as they affect human and equipment vulnerability. The end states of weapon-generated rubble (quantity and spatial distribution) are also desired. When damage levels are sufficient to result in perforation(s) of the structural component, the model must predict the hole size(s) and volume of material removed. The model must output probabilistic debris fragment size and velocity (vector) distributions and debris end-states (quantity and spatial distribution of the debris on the ground). The models must be validated against available experimental data with recommendations for additional testing where sufficient data does not exist for adequate validation. When damage levels are not sufficient to result in perforation of the structural component, the model must be capable of predicting the depth of penetration, the effects of any explosive charge including debris generation, the probabilistic distributions of debris fragment size and velocity, and rubble end state. The model must cover materials such as concrete and masonry (CMU, Brick, Adobe, Tile) used in fixed structures. The predictive accuracy of the models must be quantified, based on comparisons with experimental data and HFPB calculations. Finally, the contractor must implement the FRMs in AFRL/RWWL"s MEVA architecture which is used for assessing the lethality of conventional weapons. To this end, MEVA will be provided along with the necessary integration instructions. If necessary, access to the MEVA developer will be provided or he can be hired to do the integration. Other users include the Army (ARL & AMSAA), AFLCMC, and JTCG/ME. Following this effort, the government will install the FRMs in the AFLCMC FIST program and finally in the JTCG/ME JWS weaponeering program. PHASE I: Develop innovative FRM methodologies that can be trained by state-of-the-art HFPB calculations to simulate the effects of weapon contact or embedded detonations in fixed targets. Demonstrate their ability to capture the important characteristics of these multi-physics phenomena. PHASE II: Develop FRMs to simulate the effects of weapon contact or embedded detonations in fixed structures constructed of concrete & masonry material. The FRMs must capture the important characteristics of the phenomena for a parameter space spanning weapon type and size, and structural geometry and materials of practical significance. Implement these models in the AFRL MEVA program. PHASE III DUAL USE APPLICATIONS: Military: Complete the development of the FRMs for the range of weapons and structural components/materials required. Commercial: Used by HAZMAT teams to asses safety for explosive materials. Used in assessing safety of buildings designed for protection against natural and terrorist threats.
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