Ballistics and Explosives Research and Hazard Assessment

Institute engineers and scientists use experimental, analytical, and numerical techniques to evaluate and understand the performance of advanced armor protection concepts as well as projectile threats that range from small arms to antitank weapons.

Energetic systems and materials and their interaction remain an important area of research at the Institute. A wide range of ballistics and explosives studies are conducted for both the military and civilian sectors. Military projects include studies of high explosive projectiles and containment systems, while civilian projects are devoted to investigations such as analyses of vulnerability to potential terrorist activities and the effects of heavy machinery loads on buried pipelines.

Numerical techniques are used to simulate highly dynamic explosive and ballistic events, and equations defining the physical responses of omplex, nonlinear systems are solved with the aid of high-speed computing. A focused, multi-year internal research program was concluded this year during which techniques and tools were developed to provide more computing power with affordable workstations. By connecting several workstations in parallel, complex problems can be divided into segments, with each workstation performing part of the solution. Parallel processing can reduce the computation time needed to simulate ballistic and explosive events from days to hours.

The defeat of hardened targets, such as munitions bunkers or aircraft hangars made of concrete or geological materials, requires deep earth penetrators whose casings must be made of high-strength materials. However, most high-strength materials have little ductility and are susceptible to crack propagation during penetration. The Institute was awarded a three-year project by the U.S. Air Force Wright Laboratory's Armament Directorate to develop a computational capability to predict dynamic crack propagation in these materials while modeling the penetration event. SwRI personnel are also developing experimental techniques to measure relevant dynamic fracture properties of materials of interest. The techniques will provide a connection between laboratory materials testing and penetrator casing performance, permit trade-off studies of strength versus fracture toughness, and provide a basis for rational design evaluations.

Institute researchers are assessing the ability of computer codes to simulate the complex fluid-structure interaction that occurs when projectiles containing high explosives impact fuel-filled jet aircraft wings. In the initial phase, engineers are studying how well the numerical simulations model the phenomena; the second phase will focus on modifications and improvements to the numerical calculations. Successful accomplishment of this work will permit researchers at the U.S. Air Force Wright Laboratory to use numerical simulations to assist in damage evaluation and design studies.

State-of-the-art computer codes are being examined to see how well they simulate numerically the complex interaction of fluids and structures known as hydrodynamic ram. Hydrodynamic ram is the phenomenon that occurs when an external energy source penetrates a fluid-filled container, such as when a projectile pierces a fuel tank in an aircraft wing.

Large-scale numerical simulations are used to investigate the dynamics of yawed impact, which is often detrimental to the penetration of long-rod projectiles. This simulation shows the result of a high-density tungsten projectile impacting a steel armor target at a 5.9-degree angle.

In a study sponsored by the U.S. Army Research Office, fundamental investigations are being performed at SwRI to examine the effects of strong electromagnetic fields (EMF) on metal rod projectiles, with the objective that EMF might be used as a means to protect armored vehicles. Experimental testing has verified that metal rods become unstable when subjected to large EMFs. A 30-kV capacitor bank was used to discharge extremely large amounts of electrical energy through thin metal wires. Disruption and breakup of the rods were captured with a series of high-speed digital images using an Imacon 468 camera. Measurements obtained from the images showed that the rods tend to break into a series of thin, regularly spaced circular fragments, a result that is in good agreement with theoretical predictions.

Petrochemical industry sponsors are funding a multiyear research project to investigate the effects of loads created by large construction equipment such as bulldozers and earth movers on buried gas pipelines. Institute engineers are conducting full-scale tests of pressurized pipeline sections, with complete internal instrumentation, under a variety of different load conditions, including static surcharge (to simulate structural shoring) and dynamic impact (to simulate large truck impact over ruts). A simplified model for field operations will be developed to aid in the assessment of these pipelines under severe conditions.

Institute engineers are developing several pieces of hardware to assist the U.S. Army Corps of Engineers in the safe excavation and cleanup of formerly used defense sites that contain buried explosive and chemical ordnance. Two devices have been completed -- a portable conventional ordnance demilitarization vessel and a partial containment system (PCS) designed to efficiently capture accidentally released chemical ordnance. The containment vessel permits the repeated on-site destruction of up to six pounds of fragmenting high explosive ordnance. The PCS is designed to be used in conjunction with trench excavation operations of chemical ordnance or stored chemical agent.

For the U.S. Air Force Wright Laboratory at Eglin AFB, Institute engineers are working to better define the effects of conventional weapons on aboveground and hardened enemy targets. Of particular interest is the reduction of collateral effects -- the unintentional release of chemical or biological material into the surrounding environment -- associated with the destruction of enemy chemical and biological weapon targets. Numerical tools are being employed and experimental studies conducted to address these problems.

Institute engineers are designing closure seal systems for the Los Alamos National Laboratory that will be used to quickly gain access to a containment vessel designed for routine explosive tests. The closure system selected by SwRI is significantly lighter in weight than comparable pressure vessel closure systems and permits more efficient containment of blast loads in the main vessel. The structural system is being analyzed using DYNA3D^TM, a commercially available, nonlinear, explicit finite element code.

1996 Annual Report SwRI Home