Engineering Dynamics

Traditional disciplines such as ballistics and the loading of structures as a result of an explosion remain important areas of research at the Institute. SwRI engineers and scientists use continuum mechanics and large-scale numerical simulations to study materials and structures subjected to intense loads and extreme environments. Military and civilian applications include analyses of the effects of terrorist activities, prototype improvements of military vehicles, safety analyses, and tests of heavy machinery loads on buried pipelines.

SwRI and Gibraltar Design, Inc., used BlastCAD software to analyze the 1993 City of London Bishopsgate bombing, in which two large buildings were structurally damaged. Shown here is the City of London as modeled by the software. Glass breakage, building envelope damage, building interior damage, and building frame were evaluated. Such analyses will aid in the prediction of facility and personnel vulnerability to internal and external terrorist explosions. BlastCAD was developed by SwRI, Gibraltar, and Science Applications International Corporation.

Institute engineers are applying large-scale numerical simulations using arbitrary Lagrangian-Eulerian methods to study hydrodynamic ram, the complex fluid-structure interaction that occurs when a projectile containing high explosives impacts a fuel-filled container such as a jet aircraft wing. This ongoing project, funded by the U.S. Air Force Wright Laboratory, applies advanced computational techniques to examine and demonstrate their applicability to the goal of designing aircraft structures that can survive such violent events.

Under contract with Los Alamos National Laboratory, SwRI engineers have designed a finger-pin closure system for a large explosion containment vessel. The vessel will be used to conduct routine explosion tests to study the hydrodynamic effects of blasts. The closure system was analyzed using DYNA3D, a commercially available code, to gain an understanding of behavior of contact regions and to account for dynamic plastic response in the structural system.

In projects performed for PRC International and the Southern California Gas Company, buried pipelines were subjected to extreme surface loads, such as those created by large construction equipment, to determine pipeline strength and toughness. A thin-walled pipeline was shallow-buried and subjected to 180,000 pounds of force. Severe deformation occurred, but the pipe did not rupture or collapse. Results of these tests provide the petrochemical industry with confidence in the safety of their pipeline systems.

In support of the U.S. Air Force's continuing program to evaluate the effects of conventional weapons on equipment used to produce weapons of mass destruction - those filled with chemical or biological agents - Institute personnel conducted a series of fragment impact tests on small, liquid-filled containers. The containers were instrumented with laser and optical devices, conventional strain gauges, accelerometers, and pressure gauges. Effects varied from mild splitting and leakage to severe and violent hydrodynamic failure.

SwRI has conducted several test projects for the U.S. Army Corps of Engineers, Huntsville Center (CEHNC), to support the location and removal of on-surface and buried unexploded munitions at former defense sites. Some of these munitions contain chemical or biological warfare agents. Operations at these sites must be made safe for on-site personnel and the public; thus, it is necessary to contain any possible incidents that might take place during this process, including the release of harmful agents. A vapor control structure (VCS) was developed by the CEHNC and tested at SwRI. The VCS is a segmented steel arch structure with roll-up and personnel doors, fitted with a filter and negative internal pressure system. Experiments have been performed on specific weapon types to determine blast load and chemical release effects, to determine the ultimate blast load capacity of the structure, and to document the capability of the VCS to contain the release of chemicals resulting from explosive detonation of simulated weapons. A secondary, fabric structure was constructed around the VCS to create a space where air samples could be collected. These tests will help determine which buried weapon types can be recovered safely in the field using a VCS.

The combination of blast and fragment loading, as well as the synergistic effects for very close-in loadings on reinforced concrete structures, are being investigated by the Wright Laboratory Armament Directorate and the Institute to improve current assessment capabilities for hard targets - structures or vehicles designed to withstand bomb or armament damage. Scale-model experiments of "bare" and naturally fragmenting cased explosive charges were conducted to determine response sensitivity. The targets were instrumented to quantify the effects of combined blast and fragment loading.

SwRI engineers assisted Sandia National Laboratories with safety issues related to centrifuge accidents. A centrifuge accident event was postulated and a dynamic analysis was made to determine the bolting forces required to secure the centrifuge should an accident occur. In another task, a simulation was performed to help explain results observed in such an accident. Spalling of barrier walls also was observed and studied to select the most appropriate design features to prevent spall from occurring.

The Advanced Target/Threat Assessment Code (ATTAC), developed through an international cooperative research consortium, is a PC-based armor development and assessment program that enables engineers and researchers to perform high-resolution shot-line analysis by extending recently developed analytical modeling techniques. The SwRI-developed penetration models are more advanced than models currently employed and can incorporate future enhancements.

1997 Annual Report SwRI Home