Characterizing the Break-up and Reaction of Fragments upon Rapid Impact
Abstract
Developing advanced munitions with pre-formed reactive fragments holds the promise of improving the nation’s ability to destroy weapons of mass destruction (WMD) while reducing collateral damage in urban environments. However, to optimize the properties of these preformed fragments we need to know how and when they break-up and react upon impact with a target. The ability to visualize their break-up and reaction in situ, and at high rates, is critical to understanding how their performance depends on loading rate and the chemistry, microstructure, and properties of the reactive material. Thus, in the proposed effort we will focus on developing and utilizing advanced in situ techniques to probe the processes and mechanisms that control the break-up and reaction of metallic reactive fragments as they hit steel anvils at high velocities (~1km/s). More specifically, our team of experts will develop, enhance, and apply state-of-the art and novel x-ray and optical techniques to characterize deformation, fracture, and fragmentation processes during impact, and to characterize the size, trajectory, temperature, and reaction of the particles that are generated by the impact event. In the proposed effort, we will develop and use in situ x-ray and optical techniques at the Advanced Photon Source (APS)/Dynamic Compression Sector (DCS), at the Army Research Laboratory (ARL), and at Johns Hopkins University (JHU) to study reactive fragments impacting anvils at velocities ranging from 0.5 to 2 km/s. We will combine x-ray phase contrast imaging (XPCI) and digital image correlation (DIC) to characterize and image the deformation and fragmentation of specimens on impact with microsecond time resolution at APS. We will also characterize the chemical reaction of the particles that result from fragmentation using x-ray diffraction (XRD) at APS with sub-microsecond time resolution. Novel test geometries and advances in detector capabilities will be leveraged. At the Army Research Laboratory (ARL) we will use state-of-the art, high-speed passive and active optical imaging, spectroscopy, and pyrometry to characterize deformation, fragmentation, and reaction of specimens on impact, and to characterize particle motion, reactions and temperatures within the resulting debris cloud. At JHU we will leverage compressed sensing to develop and apply 3D particle tracking velocimetry (PTV) to characterize the size, trajectory, and velocity of the particles resulting from fragmentation, and hyperspectral imaging to improve measurements of plume temperature. In years 1 to 3, we will test Al, Al-Mg, and Al-Zr specimens machined from wrought plates, and we will vary the grain size and crystallographic orientation of the specimens. In years 4 to 5, we will test specimens formed by cold-swaging Al-Zr composite powders to vary the size and ignition of the resulting particles. We will characterize the microstructure of the initial samples and the final location, size, chemistry, and phase of the dispersed particles. Lastly, we will compare the observed processes and final particles with theoretical predictions of fragmentation and combustion to increase our understanding and to improve fragmentation models.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 16, 2019
- Source ID
- HDTRA11810016
Entities
People
- Timothy P. Weihs
Organizations
- Defense Threat Reduction Agency
- Johns Hopkins University