Dynamic Behavior of Materials IX: Energetic Materials and High Explosives
Sponsored by: TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Eric Brown, Los Alamos National Laboratory; Saryu Fensin, Los Alamos National Laboratory; George Gray, Los Alamos National Laboratory; Marc Meyers, University of California, San Diego; Neil Bourne, University of Manchester; Avinash Dongare, University of Connecticut; Benjamin Morrow, Los Alamos National Laboratory; Cyril Williams, US Army Research Laboratory
Thursday 2:00 PM
March 3, 2022
Room: 263C
Location: Anaheim Convention Center
Session Chair: Benjamin Morrow, Los Alamos National Laboratory; Georges Akiki, Lawrence Livermore National Laboratory
2:00 PM
Energy Localization during the Shock Compression of Nanoscale Plastically Bonded Explosives from All-atom Simulations: Brenden Hamilton1; Tongtong Shen1; Michael Sakano1; Lorena Alzate-Vargas2; Chunyu Li1; Alejandro Strachan1; 1Purdue University; 2Oak Ridge National Lab
The role of materials microstructure in localizing and dissipating shockwave energy is critical to understanding phenomena such as the transition from shock to detonation, shockwave attenuation, and materials failure. However, atomic scale calculations, which can provide significant insight into materials evolution under dynamic loading, have mainly focused on idealized structures such as single crystals with geometrically idealized defects such as cylindrical voids. Therefore, we develop a systematic workflow for generating all-atom, pseudo-2D simulation cells of plastically bonded explosives. Materials properties of the HE crystal, coupled with Monte Carlo techniques, are utilized to generate physically realistic structures, but at significantly reduced length scales. Using a system with a variety of microstructural defects, features, and crystallographic orientations, we run shock simulations to analyze the spatial localization of temperature and strain, as well as the evolution of the wave structure and speed. Temperature fields and shockwave evolution are mapped to initial microstructural features.
2:20 PM
Characterization of Dynamic Hydrostatic Constitutive Response of Closed-cell PVC Foams Using Water Filled Shock Tube and 3D DIC: Piyush Wanchoo1; Shyamal Kishore1; Arun Shukla1; 1URI
Closed-cell PVC foams have been a material of choice in marine sandwich panel applications. These foams, which are an interconnected network of PVC and polyurea, have demonstrated superior performance compared to other foams of similar density under impact and blast loading conditions. In this study, we ascertain the response of crosslinked PVC foams with mass densities varying from 45 kg/m^3 to 130 kg/m^3 under dynamic hydrostatic loading conditions. A novel underwater shock tube facility developed is utilized to study the response of these foams under dynamic hydrostatic conditions where the 3D DIC technique in conjunction with ultra-high-speed photography is used to provide full-field deformation data. This technique enables measurement of volumetric strain of dynamic hydrostatically loaded PVC foams further enabling measurement of bulk modulus under shock loading conditions. Buckling collapse at a high strain rate consistently shows substantial increment under dynamic hydrostatic loading conditions when compared to hydrostatic loading conditions.
2:40 PM
Simultaneous Lattice Strain and Bulk Strain Measurements during Thermal Cycling of PBX 9502: Matthew Schmitt1; Bjorn Clausen1; Travis Carver1; Sven Vogel1; John Yeager1; 1Los Alamos National Laboratory
Triaminotrinitrobenzene (TATB) exhibits irreversible volume expansion upon thermal cycling (“ratchet growth”). Various mechanisms have historically been proposed to explain this phenomenon. Since TATB powder does not ratchet grow, but consolidated pellets do, one hypothesis is that residual lattice strain from the compaction process is released when TATB is thermally cycled, causing volume expansion. To test this, we here simultaneously measure lattice strain and bulk strain during thermal cycling at the Los Alamos Neutron Science Center. Lattice strain was measured using neutron diffraction while the samples were cycled several times from ~25-160°C. Changes in lattices parameters due to temperature were completely reversible and so cannot drive the observed ratchet growth. Recent experiments and analysis have suggested microcracking at grain boundaries and interfaces is instead responsible, itself driven by the high anisotropy in the material. Implications of these findings for mechanical and ignition modeling will be discussed.
3:00 PM
Development of New, Robust Mock Materials for PBX 9502: Alexandra Burch1; Matthew Herman1; Amanda Duque1; John Yeager1; 1Los Alamos National Laboratory
Due to the risk posed by violently reactive materials such as high explosives, it is often desirable to have access to inert substitutes (“mocks”) that will behave similarly to their explosive counterpart in non-detonative applications. Use of mocks is well-established, but many explosives do not have a mock available that suitably mimics more than one or two properties, if there is a mock available at all. The objective of this work is to identify a robust thermomechanical mock for PBX 9502, an composite of the explosive TATB and a polymer binder, which closely matches a set of priorities (e.g. cost, density), and perform a series of mechanical tests. Target mechanical properties include quasistatic and dynamic response at a range of temperatures. Various strategies and methodologies for identifying and manufacturing potential mock materials will be discussed, along with preliminary data on the mechanical similarities of our new mocks to PBX 9502.
3:20 PM Break
3:35 PM
Comparison of Deflagration Modes in a Granular Energetic Material due to Spherical and Planar Impact: Meghana Sudarshan1; Ayotomi Olokun1; Abhijeet Dhiman1; Vikas Tomar1; 1Purdue University
Energetic materials are used as solid rocket propellants and explosives in the aerospace industry. For safe transportation and storage of energetic materials, having a good understanding of mechanical and chemical understanding of materials helps prevent unintended initiations. The current understanding of deflagration modes lacks complete information on hotspot formation mechanisms regarding the nature of the impact. Studies on deflagration to detonation transition focus mainly on planar impact scenarios with detonation under shock. In this study, we compare the likeliness of deflagration with different geometries of the impactor. A cohesive finite element (CFEM) based computational framework is used to simulate the behavior of granular energetic materials with cyclotetramethylene-tetranitramine (HMX) embedded in hydroxyl-terminated polybutadiene binder with planar and spherical impactor profiles. Comparison of the likelihood of detonation is highlighted based stresses created around crystals in energetic on expanding pressure profile of spherical impactor and uniform pressure profile from a planar impact.