Kent T. Danielson

The Influence of Soil Parameters on the Impulse and Airblast Overpressure Loading above Surface-Laid and Shallow-Buried Explosives

The dynamic airblast, fragmentation, and soil ejecta loading environments produced by the detonation of surface-laid and shallow-buried mines are major threats to lightweight military vehicles. During the past several years, the US Army has focused considerable attention on developing improved methods for predicting the below-vehicle environment from these threats for use by vehicle/armor analysts; thereby, improving the survivability of these platforms. The US Army Engineer Research and Development Center recently completed the first year of a three-year effort to experimentally and numerically quantify the blast and fragment loading environments on vehicles due to surface and subsurface mine and IED detonations. As part of this research effort, a series of experiments was conducted to quantify the effects of soil parameters on the aboveground blast environments produced by the detonation of aboveground bottom-surface-tangent, buried top-surface-tangent, and shallow-buried 2.3-kg (5-lb) Composition C4 charges. The experiments were conducted using three different well characterized soils; 10.8% air-filled-voids (AFV) silty sand, 5.4% AFV clay, and 29.8% AFV poorly graded sand. The combined aboveground loads due to airblast and soil debris were measured by an impulse measurement device. The near-surface airblast overpressure was quantified by a series of side-on measurements above the charges at one elevation and three radial distances. This paper summarizes and compares the results of the experimental program with emphasis on defining the effect of soil parameters on the aboveground blast environment.

Numerical Simulations of Explosive Wall Breaching

Explosive wall breaching will be a key war fighter capability in future military operations by dismounted soldiers in urban terrain environments where the close proximity of urban structures, possibly occupied by noncombatants, significantly restricts the use of large demolition charges or large caliber direct-fire weapons. The US Army Engineering Research and Development Center (ERDC) is currently investigating new explosive wall breaching systems and numerical techniques to model the breaching system interaction with the wall targets. The experimental and numerical programs will conduct comprehensive demolition breaching research on a full range of construction and material types and will fully validate new multi-functional breaching procedures across the spectrum of desired missions. As a first step in this process, the ERDC conducted a baseline study of C-4 breaching effectiveness against steel-reinforced concrete walls in FY04. The goal of this effort was to develop improved methods for breaching these walls with simple arrangements of C-4. The experimental breaching scenarios addressed: (1) a baseline study of C-4 breaching, (2) optimal use of C-4 for concrete removal, and (3) optimal use of C-4 for concrete and reinforcing steel removal. Numerical simulations of two selected experiments were conducted using the coupled Eulerian and Lagrangian code Zapotec. In these simulations, the concrete and reinforcing steel were modeled as Lagrangian materials, and the C-4 and air were modeled as Eulerian materials. Two different concrete constitutive models were used in the simulations: the Karagozian and Case concrete model, which is included with Zapotec, and the Microplane model, which was implemented in Zapotec by ERDC personnel. Comparisons between the experimental results and the numerical simulations will be described.

Modeling Fragment Simulating Projectile Penetration into Steel Plates Using Finite Elements and Meshfree Particles

Simulating fragment penetration into steel involves complicated modeling of severe behavior of the materials through multiple phases of response. Penetration of a fragment-like projectile was simulated using finite element (FE) and meshfree particle formulations. Extreme deformation and failure of the material during the penetration event were modeled with several approaches to evaluate each as to how well it represents the actual physics of the material and structural response. A steel Fragment Simulating Projectile (FSP) – designed to simulate a fragment of metal from a weapon casing – was simulated for normal impact into a flat square plate. A range of impact velocities was used to examine levels of exit velocity ranging from relatively small to one on the same level as the impact velocity. The numerical code EPIC, used for all the simulations presented herein, contains the element and particle formulations, as well as the explicit methodology and constitutive models needed to perform these simulations. These simulations were compared against experimental data, evaluating the damage caused to the projectile and the target plates, as well as comparing the residual velocity when the projectile perforated the target.

Parallel computation methods for large-scale nonlinear CSM

Publisher Summary In this chapter, a parallel explicit dynamic finite element code, “ParaAble”, is used for the three-dimensional analysis of penetration and blast loading events. The analysis of structures undergoing complex inelastic responses to load—such as those resulting from explosive detonations or high-speed impact—are challenging mechanics problems, which can typically require significant computational resources. The analyses presented in the chapter involve large models (up to several million elements) and different types of material models with varying levels of complexity and computational expense. The parallel computational strategy includes an overlapping computation/message passing algorithm and a material-weighting mesh partitioning scheme. These procedures are implemented into a parallel finite element code, “ParaAble”, and then it is used for several large-scale applications.

Validation of the Kerley Soil Model in CTH

Recently Kerley has developed a soil model suitable for implementation in Eulerian hydrocodes. The model has been installed into CTH [1]. While basic features of the model suggest it may be suitable for modeling ground shock and cratering problems, it has not been extensively validated. As such, in order to provide more confidence in the use the model, a series of calculations was conducted to compare Kerley’s model to the Hybrid Elastic-Plastic (HEP) model.Copyright

Vulnerability of Structures to Weapons Effects

The Geotechnical and Structures Laboratory (GSL) has a number of funded research efforts to support Department of Defense (DoD) requirements for understanding the response of structures to explosives/weapons. These efforts are all heavily dependent on high performance computing (HPC) simulations to meet research needs. The research efforts to be supported include Force Protection, Military Operations in Urban Terrain, and Homeland Defense. HPC simulations are used to enhance ongoing experimental programs. The simulations are used to assist in designing experiments, to aid in understanding the experiments, to extend the knowledge beyond the limitations of the experiments, and to develop numerical databases. High priority HPC hours available through the High Performance Computing Modernization Program (HPCMP) Challenge Project were used to perform these simulations. Simulation results are compared with experimental results when available.