Publications Details

Numerical Simulations of Cratering Effects in Adobe

Pena, Jeremy; Brundage, Aaron; Attaway, Stephen W.; Korbin, John P.

This paper outlines a new simplified approach to developing a material model for adobe. The approach is to fit the equation of state (EOS) using a Mie-Gruneisen (MGR) analytical model with a P-Alpha compaction law, and to fit the pressure-dependent yield surface with the Geological Yield Surface (GEO) modeled in CTH using well characterized adobe. By identifying key parameters that governed material response, this simplified modeling approach aimed to increase the understanding of the shock compaction and compression behavior of adobe. The new simplified model for adobe represented in this paper replicated the features of past experimental penetration data. At low velocities the penetration behavior of steel spheres into adobe is captured by Stokes law, where the drag coefficient is inversely proportional to the Reynolds number. Each inherently different adobe material investigated had a separate linear region with the slope equal to the inverse of the coefficient of drag multiplied by impact velocity. A transition region following the Stokes region was identified in each adobe material, where the penetration depth was constant with increasing impact velocity. This penetration depth limit was shown to be dependent upon the yield strength of the adobe and inversely proportional to the initial density. Finally, examining the sensitivity of the penetration depth to the key model parameters, the material model for adobe was adjusted to provide the best fit to the experimental penetration data. In addition, a simplified water content, or initial saturation of the adobe, was introduced as another relevant parameter to characterize the response. Using this simple material model for adobe, validated with experimental penetration data, the response of adobe targets to hypervelocity impact of a variety of projectile types can be reliably predicted.