Hybrid shock dynamics models for heterogeneous explosives with embedded inert material

Lieberthal, Brandon A

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https://hdl.handle.net/2142/89141 Copy

Description

Title

Hybrid shock dynamics models for heterogeneous explosives with embedded inert material

Author(s)

Lieberthal, Brandon A

Issue Date

2015-12-02

Director of Research (if dissertation) or Advisor (if thesis)

Stewart, D. Scott

Doctoral Committee Chair(s)

Stewart, D. Scott

Committee Member(s)

• Glumac, Nick
• Lambros, John
• Matalon, Moshe

Department of Study

Mechanical Science & Engineering

Discipline

Theoretical & Applied Mechanics

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• detonation shock dynamics
• energetic materials
• metal loaded high explosives
• shock propagation
• numerical simulation
• hybrid shock model

Abstract

Explosive devices with precisely tailored pressure output and detonation shock front velocities are in demand for numerous applications, such as mining, demolition, and defense applications. Heterogeneous explosives, consisting of a high explosive (HE) embedded with binder, combustible additives, and inert particles, enable tailoring of the properties of the detonation shock by specifying the size and properties of the added materials. Traditional simulation methods of these explosives require the resolution of the Euler conservation laws, a constitutive relation, a reaction rate law, and shock capturing methods at each point of the model and at each time step, which tends to be computationally expensive. The theory of Detonation Shock Dynamics (DSD) describes the velocity of the shock front in terms of its geometric shape in the asymptotic limit of small reaction zone length relative to its radius of curvature, and it provides an efficient method for studying detonation front propagation in such materials without the necessity of solving the reactive flow equations for the entire system. This dissertation discusses the application of DSD theory to the simulation of heterogeneous explosives, with each chapter building upon the preceding chapters. The first chapter features the mathematical formulation of a DSD model regarding a detonation shock wave passing over a series of inert spherical particles embedded in an HE fluid. We derive a series of partial differential equations that describe a linear relation between the shock normal velocity and curvature. We solve these equations numerically and observe the short-term and long-term behavior of the detonation shock wave as it passes over a regular, periodic array of unit cells. The second chapter expands upon the first by stochastically varying the properties of the inert particles based on conventional particle manufacturing methods. We predict the probability distribution of the shock velocity based on the distribution of the particle size and compare it to simulation. We also discuss random particle spacing methods and their effect on the average shock dynamics. Finally, we consider mixtures of plastic and metal particles, along with material inconsistencies, and their effects on the reliability of the simulation model. The third chapter introduces the Taylor Blast Wave (TBW) and Geometrical Shock Dynamics (GSD) theories, which each describe a radially expanding blast wave through an inert material, typically an ideal gas, as it decays from a high energy hot spot to its stable acoustic limit. We derive a composite model through simulation that describes the blast front at any velocity and test high velocity versions of classic shock experiments. We also apply the principles of TBW and GSD to materials that follow the Mie-Gruneisen equation of state, such as many plastics and metals, and develop a theory that accurately describes shock acceleration through these solids. Using a hybrid DSD/GSD model, we simulate shock propagation through both the explosive and inert material in heterogeneous explosives and compare our simulation method to traditional direct numerical simulations. Finally, the fourth chapter discusses metal foam blocks that are embedded in nitromethane. These models are of interest because nitromethane by itself is classified as a flammable liquid, not a high explosive, and is thus safer and less expensive to transport. The addition of aluminum, however, causes nitromethane to become sensitive to a detonation blast cap. We run simulations of these models, using a variety of materials and foam structures, to test their viability as explosive components. We also observe radially expanding detonation shocks and develop DSD models for these heterogeneous explosives.

Graduation Semester

2015-12

Type of Resource

text

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http://hdl.handle.net/2142/89141

Copyright and License Information

Copyright 2015 Brandon Lieberthal

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