In Situ Characterization of Dynamic Failure and Physics-Based Constitutive Model Development for Geological Materials
Abstract
There are many circumstances that require weapons to be directed at geological materials; one important example would be bombs intended to destroy buried bunkers. To design such weapons it is important to be able to predict the effect of the weapon on the geological material. For example, if a particular kind of rock is subjected to an explosion, how much damage is done to the rock and what is the effect on the buried target? These kinds of questions can be answered with sophisticated computer simulations (called “hydrocodes”), but the simulations themselves require information about how geological materials react when hit by rapid mechanical forces. In this research program we are developing tools to both predict and measure this response, in order to provide quantitative data on the behavior of geological materials that can be incorporated into simulations. The centerpiece of this program is the development of quantitative techniques for visualization and characterization of dynamic fracture and damage in geological materials. We are doing this by building an instrument to fracture specimens while watching them with x ray phase contrast imaging. We do these experiments at a synchrotron x ray source, which provides high intensity, sub-microsecond pulses of x rays. The experiment must be precisely timed because the entire fracture process is over in a few microseconds, but in that brief time we can capture multiple x ray images of damage in the material as it evolves. In order to understand and quantify the damage, we are also developing theoretical and computational tools that allow us to simulate the x ray phase contrast image formation process. The second major aspect of the program is to use the results of these experiments to develop a quantitative description of the damage, called a damage tensor, that includes information about the number, size, shape, and orientation of defects (such as cracks) as they evolve. The damage tensor will then be incorporated into a quantitative constitutive model of the the behavior of materials under dynamic loading, which can in turn be used in hydrocode simulations. Our models are developed in such a way as to make them readily extensible to a wide variety of relevant geological materials and adaptable to improved experimental capabilities for characterization.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 26, 2016
- Source ID
- HDTRA11510056
Entities
People
- Todd C Hufnagel
Organizations
- Defense Threat Reduction Agency
- Johns Hopkins University