DOP Ballistic Investigations With Explicit Analyses

DOP Ballistic Investigations With Explicit
Analyses
Guilherme Pinto Guimarães, M.C. – CTEx
Jheison Lopes dos Santos, M.C. – IME
Eduardo de Sousa Lima, D.C. – IME
André Luís de Vasconcelos Cardoso – D.C. – CTEx
CENTRO TECNOLÓGICO DO EXÉRCITO – CTEx
INSTITUTO MILITAR DE ENGENHARIA – IME
Presentation Outline
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Introduction
DOP Tests and Experiments
Overview of Explicit Problems
Lagrangian Explicit Analyses and Results
Conclusions and Future Investigations
Introduction
The Ballistic Research Group
Introduction
Ballistic Key Designs
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Brazilian Army demands for ballistic protection: Personal – Ground vehicles – Aerial
vehicles – Buildings
Full scale threats profile: Small arms – Grenades – Mines – APFSDS – Hollow charges
– RPG – EFP – IED
Modern warfare scenarios: Urban locations – Assymetric tactics – High mobility
demands – Low weight demands
Academic research for new materials and dynamic behavior of materials
DOP Tests and Experiments
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Military Standard MIL-STD-376 25 Jun 1993:
“BALLISTIC PERFORMANCE RANKING OF CERAMIC ARMOR PLATES AGAINST
HIGH DENSITY PENETRATORS”
 US Department of Defense – Approved for public release
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PURPOSE: Provide a GENERAL METHODOLOGY for the test equipment, procedures,
targets and terminology needed to develop BALLISTIC PERFORMANCE EVALUATION
and ranking of advanced armor materials.
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APPLICATIONS:
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Ballistic tests on armor materials;
Selection of Materials to employ in armor systems;
Tool to promote research and development of new armor materials;
Parametric analyses on the effects of material properties and other factors such as: tile size –
confinement – penetrator properties in ballistic performance;
 Main scope: Armor ceramics and other low ductility materials + Projectiles made of heavy alloy, long
rod type;
 Out of scope, yet feasible: Armor metallic materials.
SUGGESTED REFERENCES:
 MIL-STD-376
 MIL-STD-662 – V50 BALLISTIC TEST FOR ARMOR – US Department of Defense
DOP Tests and Experiments
MIL-STD-376 Definitions
 ARMOR: A shielding material provided for ballistic defeat of projectiles or
fragments when inherent shielding is inadequate.
 ARMOR SYSTEM: A combination of various armor materials with
properties and geometry chosen to defeat one or more specific threat
projectiles.
 BALLISTIC LIMIT: V50BL; V100
 DOP – DEPTH OF RESIDUAL PENETRATION: The length or depth of
the penetration cavity of the steel backing plate after passing through the
ceramic.
 LONG ROD PENETRATOR: Any projectile having a length to diameter
(aspect) ratio greater than five.
DOP Tests and Experiments
MIL-STD-376 Test Procedures
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MIL-STD-376 DOP test procedures:
 Ceramic tile with confinement frame
 0.5mm aluminum sheet behind tile OR attachment of backup square thick plate
 Backup plate made of RHA (or 4340 steel w spec. hardness) with thickness sufficient to be effectively
semi-infinite or with respect to the residual penetration of the tested projectile/material combination
Further definitions:
 RHA - Rolled Homogeneous Armor: Armor steel w MIL-A-12560 requirements
 Semi-infinite: As related to penetration of a thick target, implies that the rear surface of the plate
receives only elastic loading, with no permanent deformation being discernible
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MIL-STD-376 General Squematic –
Standard Target Configuration
SUGGESTED REFERENCE:
 MIL-A-12560 – Armor Plate, Steel, Wrought, Homogeneous (For Use in Combat Vehicles and for Ammunition Testing)
DOP Tests and Experiments
Current Research Goals
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IME Research Goals and Considerations:
 Ceramic and metallic materials separate investigations
 Current metallic materials research: Aluminum alloys
 DOP studies based on MIL-STD-376 with modifications
 Explicit numerical modeling to support research investigations tests and
experiments
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Chosen modifications on DOP Tests:
 DOP evaluations only to metallic back plate
 Metallic back plate made of aluminum alloy – 6356 T6
 Long rod penetrator: 7,62 AP commercial projectiles
 Target geometry definition: Thick cylinders entirely clamped
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Threat definition: ABNT NBR 15000/2005 – “Armor for Ballistic Impacts –
Classification and Evaluation Criteria”
DOP Tests and Experiments
The Problem Definition
DOP Tests and Experiments
The Problem Definition
 Modified target geometry for metallic materials
 AP-6 Chosen threat: 840m/s impact velo @ 15m
Overview of Explicit Problems
• Dynamic problems
• The Strain-Rate Issue – The dynamic behavior of materials
Overview of Explicit Problems
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SMALL ARMS BALLISTIC IMPACT ISSUES
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Low to intermediate impact velocity
High deformations and erosion
Heating and melting
Shock waves propagations – Reflections
Several failure modes
Several nonlinearities
Strain-rate dependency
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THE EXPLICIT DYNAMIC SOLUTION
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EXPLICIT NUMERICAL MODELING:
 Lagrangian approach
 Full 3D solid elements
 Transient dynamic impact: ms
magnitude event
 Dynamic constitutive material models
 Equation-of-State (EOS) definitions
 Failure and erosion definitions
 Implicit numerical time integration method: NEWMARK
 Explicit numerical time integration method: CENTRAL DIFFERENCE
Overview of Explicit Problems
 TIME-STEP CONTROL: Courant-Friedrichs-Levy criterion – Explicit stability limit
 FE Mesh issues: forms and sizes – Reduced integrated elements demand (Fully integrated
elements still possible) – 8 node solid HEXAEDRAL elements; other forms to be avoided.
 Hourglass energy numeric issues: Zero-energy deformation modes
Suggested references:
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EXPLICIT DYNAMICS with ANSYS/LS-DYNA Release 5.3 – 1996 – ANSYS, Inc.
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LS-DYNA SHORT COURSE – Matthias Hörmann – CADFEM GmbH – 2008 ESSS South American ANSYS Users Conference, Rio de Janeiro-RJ.
Lagrangian Explicit Analyses and Results
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Hardware & Software
 IME: AUTODYN Academic Research
 CTEx: ANSYS/LS-DYNA (.k file) & LSTC/LS-DYNA
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Contact Issues
Materials Dynamic Setup
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Control cards
 Laboratory tests: SHBT-Split Hopkinson Bar Test
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Hourglass control
 Paper data review
 ANSYS/AUTODYN libraries
 Equation-of-State (EOS) setup: SHOCK & LINEAR
 Failure & erosion criteria: Geometric strain Vs Constitutive model
Lagrangian Explicit Analyses and Results
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Data review - AUTODYN libraries: CART BRASS – 4340 STEEL – LEAD – ALUMINUM
 6061T6 Aluminum Alloy Johnson-Cook Constitutive & Failure Data(#1)
 6061T6 Aluminum Alloy Shock EOS Data (#2)
 Cart Brass (#3)
 4340 Steel Johnson-Cook Constitutive & Failure Data (#4)
 4340 Steel Shock EOS Data (#5)
 Lead (#2)
Suggested references:
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(#1) NUMERICAL SIMULATION OF SOLID PARTICLE IMPACTS ON AL6061-T6 PART I: THREE-DIMENSIONAL REPRESENTATION
OF ANGULAR PARTICLES – M. TAKAFFOLI & M. PAPINI – Department of Mechanical and Industrial Engineering – Ryerson
University, Toronto, Canada – Wear Journal, 2012.
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(#2) EQUATION OF STATE AND STRENGTH PROPERTIES OF SELECTED MATERIALS – DANIEL J. STEINBERG – Lawrence
Livermore National Laboratory, Livermore, USA – 1996.
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(#3) SELECTED HUGONIOTS: EOS – JOHSON & COOK – 7th International Symposium on Ballistics
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(#4) Fracture Characteristics of Three Metals subjected to various strains, strain rates, temperatures and pressures - Johnson
GR, Cook WH, J Eng Mech Vol 21, 1985
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(#5) A HIGH-STRAIN-RATE CONSTITUTIVE MODEL FOR METALS – Steinberg, D.J. & Guinam M.W. - Lawrence Livermore
National Laboratory, Livermore, USA – 1978.
Lagrangian Explicit Analyses and Results
Material Dynamic Models
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JOHNSON-COOK Constitutive model for metals
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A CONSTITUTIVE MODEL AND DATA FOR METALS SUBJECTED TO LARGE STRAINS, HIGH STRAIN RATES AND
HIGH TEMPERATURES. GORDON R. JOHNSON (Honeywell Inc. – Defense Systems Division, USA) & WILLIAM H.
COOK (Air Force Armament Laboratory – Eglin Air Force Base, USA) , 7th Int Symposium on Ballistics, The
Hague/The Netherlands, 1983.
Constitutive model for materials subjected to: LARGE STRAINS – LARGE STRAIN RATES – HIGH
TEMPERATURE with data from torsion, static tensile, hopkinson bar and dynamic hopkinson bar
labortatory tests.
Materials include: Copper – Nickel – Cart Brass – Steels – Aluminums – Tungsten – DU
Complementary Failure calculations
Adequate for computations
Lagrangian Explicit Analyses and Results
Material Dynamic Models
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STEINBERG-GUINAM Constitutive model for metals
– A CONSTITUTIVE MODEL FOR METALS APPLICABLE AT HIGH-STRAIN RATE. D.J.
STEINBERG, S.G. COCHRAN and M.W. GUINAM (Lawrence Livermore Laboratory –
University of California, Livermore, USA), Journal of Apllied Physics, 1980.
Constitutive model for materials subjected to HIGH STRAIN RATES
Shear Mod & Yield Stress dependent on: Equivalent plastic strain – Pressure –
Temperature
Strain-rate dependency limit – Not valid above 10GPa stresses
Complementary investigation for Equation-of-State (EOS) parameters
Suggested reference:
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EQUATION OF STATE AND STRENGTH PROPERTIES OF SELECTED MATERIALS – DANIEL J. STEINBERG – Lawrence Livermore National
Laboratory, Livermore, USA – 1996.
Lagrangian Explicit Analyses and Results
FE Lagrangian Models
AP 7,62 Round – Commercial Design – Full 3D Detailed Geometry – Half Symmetry
Lagrangian Explicit Analyses and Results
FE Lagrangian Models
The Target – Adequate Setup Target-Projectile
Lagrangian Explicit Analyses and Results
FE Lagrangian Models
The Ultimate FE Model
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FE STATISTICS:
120,000 Elements –
Target
45,000 Elements –
Projectile
Lagrangian Explicit Analyses and Results
V1(791,10m/s) – V2(826,04m/s) – V3(887,55m/s) Analyses
Lagrangian Explicit Analyses and Results
Complementary Investigations
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Comparisons with
real firing
Penetration path
investigation
Temperature and
wear effects
Shock condition:
Al HEL < 1GPa
P > 13GPa
Conclusions and Future Investigations
 The demand for a Ballistics Research Group
 The importance of materials research with numerical modeling and simulations
 The current IME research: Importance of several materials characterization –
Processing / Modeling / Testing
 The use of Lagrangian Explicit approach: 3D full detailed model
 The “tools of a trade”: Mesh refinements and mesh dependence upon analysis –
Contact issues – Explicit details – Failure Vs. erosion – EOS
 Modified paths for penetration processes: Different regimes
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Use of other modeling techniques and approaches
Data acquisition – Split-Hopkinson bar tests
Improvement for materials modeling
Improvement for data adjustment and correlation with real firing results
Mesh refinements and adequate correction with failure and erosion models and data
Mesh numerical regularization
THANKS FOR ATTENTION
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SPECIAL ACKNOWLEDGEMENTS
 ESSS/Rio de Janeiro/Brazil: Mr. Ivan Riagusoff/Mr. Luiz Lima/Mr. Roberto Silva
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CONTACTS
 Instituto Militar de Engenharia
 Centro Tecnológico do Exército
www.ime.eb.br
www.ctex.eb.br
[email protected]
[email protected]

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