NCSA NEWS

The NCSA Computational Structural/Solid Mechanics (CSM) group provides modeling and simulation (M&S) support to Air Force groups at Wright-Patterson Air Force Base near Dayton, Ohio. These groups are interested in all aspects of aircraft survivability. Support from the CSM group ranges from providing mentoring and training to engineers and researchers in the survivability community to performing M&S work on specific aircraft and possible threats to these aircraft.

In order to accurately predict how an aircraft will react to a threat, CSM researchers use state-of-the-art software to capture the important physics of encounters between aircrafts and airborne threats, such as anti-aircraft artillary, surface-to-air, and air-to-air missiles. Generally, scenarios that are simulated by CSM researchers consist of threat systems impacting, penetrating, and detonating in or near aircraft structural components. In these encounters, the structure of an aircraft is likely to be significantly damaged as the threat imposes stresses that are far greater than the structure can withstand.

CSM researchers use a number of software packages and are developing others, which capture the necessary physics to simulate these encounters. The group presently uses the LSDYNA3D, MSC/DYTRAN, and CTH codes for this M&S work. These are explicit time integrating dynamic finite element codes, which incorporate appropriate contact algorithms and failure criteria and have been validated by comparisons with experimental data.

As an example of the type of problem of interest to the survivability community, Figure 1 shows a generic cylindrical projectile approaching a flat plate at a fairly shallow angle and high velocity. The projectile is modeled with solid and shell elements having different material properties and thicknesses. Figure 2 shows the projectile 1.54 milliseconds after impact. Note that the plate, as well as some of the projectile structures, have failed and broken up. Figure 3 shows a closeup of this event with color stress contours superimposed on the model.

Figure 1. Generic Cylindrical Projectile Approaching a Steel Plate

Figure 2. Generic Cylindrical Projectile 1.54 msec after Impact

Figure 3. Close-up of Generic Cylindrical Projectile 1.54 msec after Impact—Stress Color Contours Are Shown

Modeling and simulation of these types of events helps predict test outcomes in advance and assists in test planning. Once the M&S models are validated against post-test data, off nominal numerical tests can be run using the models. For instance, in the example case presented here, a limited number of physical tests can be run at selected impact velocities and angles of incidence. Then, numerical tests, done on a supercomputer can be performed at other velocities and incidence angles to fill in the gaps.

For more information on this type of modeling and simulation, contact Ronald L. Hinrichsen at (937) 904-5137, or hinricrl@asc.hpc.mil.

Access Online | Posted 11-7-2000