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Title: Investigation of the fragmentation of an explosively driven cylinder

Abstract

Explosively driven fragmentation is highly complex. To better understand the field detonation, different methodologies (Lagrangian (with a failure threshold in VisIt and element erosion), ALE and embedded grid) were simulated to provide a comparison to the experimental data through the utilization of fragment distributions and gross deformation metrics. Provided with the geometrical parameters and the results from the experimental data, the computer simulations were conducted after the successful writing of each input file. Mesh refinement – a scalar multiplier applied to the mesh to refine the results – was then studied. The objective was to find a value that parallels the experimental results as the mesh can be refine indefinitely, theoretically. Various mesh resolution scales were simulated and the results graphically compared, using the damage and failure variables from a statistical Johnson Cook failure model, the number of fragments over time as well as time required for each simulation to run and number of processors utilized. The desired result is a calculated method to quantify the comparison being performed.

Authors:
 [1];  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1179434
Report Number(s):
LLNL-TR-666136
DOE Contract Number:
AC52-07NA27344
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 36 MATERIALS SCIENCE

Citation Formats

Arthur, C. W., and Dunn, T. A.. Investigation of the fragmentation of an explosively driven cylinder. United States: N. p., 2015. Web. doi:10.2172/1179434.
Arthur, C. W., & Dunn, T. A.. Investigation of the fragmentation of an explosively driven cylinder. United States. doi:10.2172/1179434.
Arthur, C. W., and Dunn, T. A.. Fri . "Investigation of the fragmentation of an explosively driven cylinder". United States. doi:10.2172/1179434. https://www.osti.gov/servlets/purl/1179434.
@article{osti_1179434,
title = {Investigation of the fragmentation of an explosively driven cylinder},
author = {Arthur, C. W. and Dunn, T. A.},
abstractNote = {Explosively driven fragmentation is highly complex. To better understand the field detonation, different methodologies (Lagrangian (with a failure threshold in VisIt and element erosion), ALE and embedded grid) were simulated to provide a comparison to the experimental data through the utilization of fragment distributions and gross deformation metrics. Provided with the geometrical parameters and the results from the experimental data, the computer simulations were conducted after the successful writing of each input file. Mesh refinement – a scalar multiplier applied to the mesh to refine the results – was then studied. The objective was to find a value that parallels the experimental results as the mesh can be refine indefinitely, theoretically. Various mesh resolution scales were simulated and the results graphically compared, using the damage and failure variables from a statistical Johnson Cook failure model, the number of fragments over time as well as time required for each simulation to run and number of processors utilized. The desired result is a calculated method to quantify the comparison being performed.},
doi = {10.2172/1179434},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Jan 09 00:00:00 EST 2015},
month = {Fri Jan 09 00:00:00 EST 2015}
}

Technical Report:

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  • High explosive enclosed by a metal case qualitatively describes an essential component of high energy systems of importance to the Department of Energy. Detonation of the high explosive causes intense transient pressure loading of the metal following arrival of normal or obliquely incident explosive detonation wave. Subsequent expansion and deformation of the metal case leads to eventual rupture and the opening of fractures and fissures. Details of the rupture process are critical to performance of the system. Consequently, it is essential that the material and kinematic issues governing the processes of dynamic loading and subsequent failure of an explosive-metal casemore » component within a functioning system be adequately understood. Among the reasons are to quantify existing performance, characterize potential degradation of performance resulting from system aging, and optimizing or maintaining system performance through implementation of structural or material changes. The physical and engineering issues underlying this dynamic response and failure phenomena are not adequately understood. The purpose of the present program is to identify the key issues and develop theoretical, computational and experimental models needed to achieve a satisfactory theoretical and analysis framework for analysis of metal case failure in the explosive environment. Specific tasks within the present program include: (1) Models and theories currently being pursued based on physical principles of both the statistical fragmentation concepts of Mott and the energy-based concept of others show promise of providing the analytic and computational methodology capable of predicting explosion-induced fracture and fragmentation of metal components. Experimental studies initiated in the earlier effort offer promise to provide critical test data for validation. The present task shall involve the further refinement and development of the dynamic failure and fragmentation models and theories, and the concomitant application and validation of these models and theories to experimental test data with the focus of providing the analytic methodology sought in the programmatic effort. (2) Stand-alone engineering algorithms and large-scale computer codes will constitute the calculational methodology developed to simulate and analyze the operational system response of metal components in explosive-loading environments. This task will pursue the preparation and implementation of the models and theories of dynamic fragmentation above to the status of engineering and computational analysis tools. The engineering and computer analysis tools pursued will also be tested against experimental fracture and fragmentation data emerging from the program effort.« less
  • Cylinders and rings fabricated from AerMet{reg_sign} 100 alloy and AISI 1018 steel have been explosively driven to fragmentation in order to determine the fracture strains for these materials under plane strain and uniaxial stress conditions. The phenomena associated with the dynamic expansion and subsequent break up of the cylinders are monitored with high-speed diagnostics. In addition, complementary experiments are performed in which fragments from the explosively driven cylinders are recovered and analyzed to determine the statistical distribution associated with the fragmentation process as well as to determine failure mechanisms. The data are used to determine relevant coefficients for the Hancock-McKenziemore » (Johnson-Cook) fracture model. Metallurgical analysis of the fragments provides information on damage and failure mechanisms.« less
  • Fragmentation experiments on explosively loaded uranium cylindrical shells are analyzed in terms of current statistical and energy theories of dynamic fragmentation. The analysis focuses on particle size distribution data corresponding to the prompt metal fragmentation. Recent two-dimensional calculations of the initial shock hydrodynamics have established the kinematic conditions driving fragmentation. Calculations based on the hydrodynamic expansion strain rates and the surface energy of molten uranium provide estimates of fragment size agreeing in trend and magnitude with the experimental data.