Constitutive Model Evaluation for EOD Ballistic Impact Simulations
Dr. Mark Vulitsky, Naval Explosive Ordnance Disposal Technology Division
Dr. Leonard Schwer, Schwer Engineering & Consulting Services
Mr. Kenneth Poe, Naval Explosive Ordnance Disposal Technology Division
Dr. Kurt Hacker, Naval Explosive Ordnance Disposal Technology Division

Abstract:

The Naval Explosive Ordnance Disposal Technology Division (NAVEODTECHDIV) is examining the use of modeling and simulation as an alternative method for establishing render safe procedures (RSP) for the Joint Service EOD community. The goal of this work is to develop methods that can reduce the time and cost associated with developing an RSP for unexploded ordnance based on empirical data alone. As part of this effort, computer simulations of basic impact scenarios were conducted, experiments were completed to acquire data for comparison purposes, and research on material properties was initiated to provide the correct parameters for the materials under study.

Ballistic penetration simulations with the Smooth Particle Hydrodynamics (SPH) technique, as implemented in LS-DYNA, in general provide good predictions for high velocity impact problems. This technique was used to simulate several EOD projectiles impacting flat 6061-T6 aluminum and A36 steel plates. The SPH method, along with the Johnson-Cook constitutive model, was used to simulate the target material. This material model requires five parameters that need to be determined experimentally, and three additional material characteristics. It is expected that there will be a need to predict the effect of an impact by an EOD projectile when little information is known about the actual target material, such as in foreign munitions. Therefore, a study was conducted in order to determine the sensitivity of simulation results to the variation of the material parameters included in the Johnson-Cook constitutive model. This paper summarizes the results obtained when the individual Johnson-Cook parameters were varied for the target material over a range of up to 100% and compared to empirical results. It was shown that when the velocity of the projectile is sufficiently higher than the ballistic limit, the target material could be represented with a simple elastic, perfectly plastic material model.

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