Nonlinear Acoustic Landmine Detection: Profiling Soil Surface Vibrations and Modeling Mesoscopic Elastic Behavior
Abstract
Acoustic-to-seismic (A/S) coupling involving airborne sound is used to generate soil vibrations that interact with the top plate of a buried landmine. Due to scattering, the interaction at the soil-mine interface produces an enhanced and strongly nonlinear soil surface vibration directly over the buried landmine. Resonant tuning curves of the soil-mine system show that the nonlinear behavior observed near resonance for "on the mine" locations is considerably stronger than that seen "off the mine." This suggests that some false alarms due to the resonant effects of the ground's natural layering may be eliminated by comparing the frequency softening in resonant tuning curves between "off" and "on target" locations. Experiments with the soil-mass oscillator (SMO) apparatus show that the nonlinear acoustic landmine detection problem involves mesoscopic nanoscale nonlinear elastic behavior. Resonant tuning curves have linear backbones, a behavior also characteristic of certain geomaterials (sandstone) Elasto-slip (Iwan 1966) and LISA (Scalerandi et al 2002) models of hysteresis are used to explain this phenomenon. The soil-mine interface, which is modeled using a soil-plate oscillator (SPO) apparatus, is extremely nonlinear. The SPO is excited using both acoustic and electromagnetic means. A/S coupling experiments are employed to simultaneously measure vibrations at the underside of a buried clamped plate and the soil surface. Electrodynamic experiments determine the motional impedance of a combined soil-plate system. Nonlinear acoustic landmine detection experiments are performed in the anechoic chamber facility using both a buried acrylic drum-like mine simulant and a VS 1.6 plastic anti-tank landmine. Using an automated laser Doppler vibrometer, soil surface vibrations are profiled as a function of scan position. Elements of both the elasto-slip and bilinear hysteresis models appear in these experiments.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 04, 2007
- Accession Number
- ADA473345
Entities
People
- Sean A. Genis
Organizations
- United States Naval Academy