Full Ship Shock Test Modeling

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Full Ship Shock Test Modeling
Dr. Tom Moyer, NSWC/Carderock 15 April, 2008
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MS For Ship UNDEX Response

• Modeling Simulation (MS) Is Used By The Navy
  To Predict Ship Structure Systems Response To
  Underwater Explosion Threats
• Design Qualification Of Ship Systems
• Pre-Test Prediction Of Full Ship Shock Trial
  Response
• MS Being Evaluated For
• More Extensive Use For Design Qualification Of
  Ship Systems
• Major Component In FSST Alternative(s)

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Summary of Underwater Explosion Phenomena
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DYSMAS

• DYnamic System Mechanics Advanced Simulation
• A fully-coupled hydrocode for simulating
  underwater explosion phenomena and their effects
  on naval structures

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DYSMASDYnamic System Mechanics Advanced
Simulation

• .

DFBEM BEM solver Bubble Fluid Dynamics
HYDROCODE FOR SIMULATION OF UNDERWATER EXPLOSION
EFFECTS
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DYSMAS V V Approach

• Verification Procedure
• Documentation of the DYSMAS code and its
  capabilities
• Documentation of configuration management model
  verification calculations
• Documentation of laboratory and small-scale
  validation calculations
• Comprehensive report applicable to UNDEX
  applications
• Validation Procedure (Phase I - General
  Validation)
• Acquire validation-quality UNDEX loading and hull
  response data for platform design and weapon
  lethality applications using surrogate ship
• Pre- and post-test comparisons of DYSMAS
  simulations vs test data
• Code validation against full-scale, realistic
  ship structure
• Validation Procedure (Phase II -
  Application-specific Validation)
• Design acquire validation-quality UNDEX loading
  and response data for specific (local) platform
  structures
• Code validation against design-specific concepts

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TYPICAL DATA ANALYSIS
Full Record
1/e Pmax
Shock Wave
Shock Wave (extended)
1st Bubble Pulse
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EFSP
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Lagrangian Model

• 16,165 Nodes
• 21,053 Elements

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Results Innerbottom, Vertical Velocity Below
FWD STBD Mount
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Eulerian Simulation
T 5.0 msec
T 5.4 msec
T 5.9 msec
T 6.8 msec
T 8.3 msec
T 11.8 msec
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Lagrangian Simulation
T 10.0 msec
T 6.2 msec
T 50.0 msec
T 13.2 msec
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Innerbottom Vertical AccelerationDYSMAS vs EFSP
Test
FWD
60 lbs HBX, 20 ft Hrz Stdf
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DYSMAS/SUMMARY

• DYSMAS Is Widely Used In Navy Community For UNDEX
  Simulations
• 2007 JASON Review Concluded
• Good Agreement With Liquid Response
• Good Agreement With Short-time Structural
  Response
• Structural Response After Initial Impulse Can
  Be Improved
• A validated MS could evaluate/improve
  component-testing methodology

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Beyond DYSMAS gt CREATE

• DYNA_N/PARADYN Lack Many Of The FEM Features
  Needed For Improved UNDEX Simulations
• DYNA_N/PARADYN Employ Antiquated Software
  Constructs
• Maintenance Difficult/Time Consuming
• Adapting To Evolving Computer Hardware
  Challenging
• Gemini Is Sufficiently Validated Employs Modern
  Software Engineering Constructs
• Standard Coupler Interface Limits Calculation
  Scaling On Parallel Platforms

SOLUTION Develop Gemini/Lagrange Solver With
Parallel Coupling
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CREATE Objectives For UNDEX

• Develop Robust Computational Capability To
  Predict
• Response Of Surface Ships Submarines To UNDEX
  Loading
• System/Component Environments
• Structural Response Damage
• Scenarios
• Stand-Off UNDEX
• Close-In UNDEX
• SURFEX
• Interface w/ Ship State Modeling
• ASAP/ARM
• FASST

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CREATE USE CASE IStandoff UNDEX Response

• Objective Quantify ship response to standoff
  UNDEX shot geometries
• Problem Characteristics
• Linear-elastic hull structure (no appreciable
  damage)
• Point-to-point non-linear elements (e.g., shock
  mounts)
• Linear-elastic equipment system response
• End-User Products
• Quantify equipment location shock environments
• Specifications for isolation systems (mounts
  rafts)
• Develop more-representative equipment
  qualification environments for component-level
  testing

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CREATE USE CASE I Standoff UNDEX Response

• Capabilities from CREATE program
• Integrated modal analysis capability
• Integrated (implicit) static pre-calculation
  capability
• Hydrostatic pre-stress, static bending moment
• Optimized explicit code solution procedure for
  pure linear-elastic problems
• Bulk of design cases
• Improved modal characteristics of equipment
  systems
• Enables smoother, more accurate incorporation of
  vendor sub-models
• Results Synthesis gt Design Requirements,
  Performance Assessments, Design Modifications
• Fully Integrated With Ship Design Tools
• Includes Integration w/ ASAP/ARM
• Development of REPLAY strategies
• Meets All Requirements For FSST Replacement
  Calculations

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CREATE USE CASE IISevere UNDEX Response

• Objective Quantify equipment response and damage
  to more severe shot geometries
• Problem Characteristics
• Non-linear hull structure response
• Point-to-point non-linear elements (including
  shock mount bottoming)
• Non-linear equipment and system response
• End-User Products
• Equipment and system damage and operability
  assessments
• Hull structural performance
• LFTE Assessments (w/ limitations)

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CREATE USE CASE II Severe UNDEX Response

• Capabilities from CREATE program
• Includes list from Use Case I
• Multi-length scale modeling strategies
• All-up simulation capability
• Telescoping analysis strategies
• Applications using REPLAY functions
• Fragility assessment capability
• Enables design margins to be assessed
• Enhanced Mission Effectiveness Assessment
• Enhanced Results Synthesis Methodology
• Quantification Of Margin Uncertainty

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CREATE USE CASE III LFTE Assessments

• Objective Quantify ship structural damage due to
  LFTE UNDEX scenarios
• Problem Characteristics
• Extremely Non-linear hull structure response
• Large hull deformations w/ Significant Contact
  Significant Material Failure
• Time Evolutionary Structural Degradation
• End-User Products
• Primary structural damage
• Cascading structural damage effects
• Equipment and system damage and operability
  assessments

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CREATE USE CASE IIILFTE Assessments

• Capabilities from CREATE program
• Improved failure models failure criteria
• Damaged based failure models
• More-accurate damage progression
• Energy conserving damage propagation
• More-accurate damage patterns
• Fracture based damage models (perhaps)
• Particle methods (perhaps)
• More-accurate contact algorithms
• No miss contact detection
• Energy/Momentum conserving forces

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Technical Approach

• Integrate Gemini Into Evolving SIERRA
  Architecture From SNL
• Leverage Existing Substantial DOE Commitment
• Evolve SIERRA To Address
• More Efficient Parallel Workload Distribution
• General, Scale-able Euler/Lagrange Coupling
• Enhance Lagrange Capabilities In SIERRA For UNDEX
  Requirements
• Robust Structural Element Library
• Multi-Length Scale Modeling
• Modal Sub-Structuring (CMS)

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CREATE/UNDEX Development Team Organization
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CREATE/UNDEX Schedule
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Summary

• DYSMAS Provides Navy UNDEX Response MS
  Capability Sufficient For
• FSST Alternative
• Limited System Design/Qualification Support
• Limited Structural Damage Prediction Capability
• CREATE/UNDEX Capability Will
• Expand Application For System Design/Qualification
  
• Enhance LFTE Assessments
• Support Design Of Cheaper Safer Ships