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HOSS: A Toolkit for Non-Linear Damage
Prediction for NPH Risk Assessments
E. Rougier, E.E. Knight and Z. LeiEES-17 Geodynamics Team
Los Alamos National Laboratory
October 2016
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Why HOSS at LANLNuclear Source Phenomenology
The prediction of a cavity radius and spall signature from a
nuclear source is inherently important for determining seismic
yield. They are part of the fundamental phenomenology controlling
the way energy from the source couples to earth and ultimately
becomes part of the far field seismic signal.
Pressure Cavity from a Test Vertical Displacement
Cavity Radius
Spall Signature
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HOSSHybrid Optimization Software Suite
HOSS-Solid– The next generation FDEM
technology– Multiplicative decomposition-
based large deformation– Linkage to nonlinear material
packages – Incorporates material
stochastic framework– Non-locking finite elements– Next
generation fracture model– State-of-the-art contact
detection algorithms – Latest generation discretized
distributed smooth contact force based approach
– 2D/2.5D/3D general/irregular shapes of discrete elements
– Rock joint handling
HOSS-ISF– Naturally integrates solid with
all regimes of fluid flow at material point level
– Not a coupling approach– Supports any explicit solid
solver and any explicit fluid solver
– Resolves transient and steady state flow through crack
manifolds as well as existing rock joint manifolds
– Resolves transient and steady state flow between crack/joint
manifolds and rock matrix
– Resolves transient and steady state anisotropic flow through
porous geo-material (seepage)
HOSS-Fluid– Universal explicit CFD solver
for all flow regime– Suitable for both steady state
and developing transient flow– Stable for all flow regimes–
Combines all flow regimes in
the same problem– Material law is supplied
separately through material packages
– Includes non-inertial Eulerian formulation
Initially developed for high strain rate analysis of underground
explosive events
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FDEM in a NutshellHybrid Continua-Discontinua
Incipient Fracture
Developing Well Developed Fracture and
Fragmentation Processes
Smooth Transition from Continua to
Discontinua
FEM Domains
DEM Domains
Fracture Initiation in the Solid
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• Four main factors for a FDEM fracture/interface modeling:
tensile strength, shear strength andthe specific fracture energies
in tension and in shear• In FDEM there is a smooth representation
of the transitioning of the material from continuumto discontinuum
behavior via the incorporation of cohesive models at the interfaces
of the finiteelements• The cohesive model is described as
follows:
• Elastic until the relative displacement (normal or
tangentially to the interfaces), δ, reaches the elastic limit, δe.•
When δ is greater that δe, the cohesive model enters into the
strain softening region. Full breakage occurs when δ isgreater than
δc.• Same type of cohesive model is implemented in tension and in
shear, but with different parameters.• The shaded portion of the
curve shown in right figure represents the fracture energy for both
tension and shear.
δ
σcoh
Material Fracture Energy
δe δc
1
Ecoh
σtensile Cohesion points
Schematic representation of cohesion points between two
tetrahedral cells
Typical strain softening curve for FDEM fracture model. δe is
the elastic fracture
aperture, while δc is the maximum fracture aperture
FDEM in a NutshellHybrid Continua-Discontinua
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HOSSSoftware in Action
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Advanced Developments under HOSSSolid Material Model
Isotropic
Anisotropic
Features a unified hypo-hyper approach with multiplicative
decomposition based selective integration approach.
Eliminates volumetric locking. Multiplicative decomposition
allows for the
linkage to nonlinear material packages. Anisotropic properties
of the solid can be
specified in a cell by cell basis.
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2015
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Advanced Developments under HOSSSolid Material Model
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Advanced Developments under HOSSSmooth Contact Algorithm
A improved discretized distributed contact force based approach
which exactly preserves the contact energy.
The smooth approach greatly improves accuracy especially for
dynamic fracture related simulations.
A robust algorithm that overcomes the problems observed with
existing contact enforcement approaches (“non-smooth contact
forces” and “dead contact zones”).
2011
With this new algorithm the contact search and interaction is
resolved only around the areas of interest, i.e., fractures
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Advanced Developments under HOSSUnified Cohesive Model
Features a unified cohesive model, which incorporates most of
the advantages from existing approaches.
Automatically and dynamically inserts damaged surfaces into the
material according to the stress state.
Smoothly transits state variables from continua to discontinua.
Incorporates the smooth contact algorithm which greatly
improves
both the efficiency and accuracy.
δt δ
ft
σSmooth Transition from Continua to
Discontinua
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Advanced Developments under HOSS1st Generation vs. Next
Generation
Next Generation FDEM
Non-locking Elements Smooth Contact Algorithm Unified Cohesive
Model
Combined Single Smeared Crack Model
Discrete Element based Contact Algorithm
Constant Strain Elements
1st Generation FDEM
Smoo
ther
Str
ess
Fiel
d
Smoo
ther
Con
tact
For
ce
Smoo
ther
Fra
ctur
e Tr
ansi
tion Continua
Discontinua
Continua
Discontinua
Y-code based
HOSS based
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Solver for FrackingIntegrated Solid–Fluid Solver (ISF)
Specially designed for modeling hydrofrac type of processes
ISF accounts for:– Fluid flow through fracturing porous
solid
in 2D/3D– Fluid flow through crack manifolds– Pressure wave
propagation through fluid– Fluid-solid interaction
Fluid phase is described using the same grid of solid phase via
a modified Eulerian formulation.
Eliminates the need of continuously mapping physical variables
between the fluid and solid domains.
Explicit solver with an aperture independent time step
Fluid pressure acting inside of the solid matrix
Fluid flow along the
cracksSeepage in/out of
the solid matrix and into the cracks
Seepage inside of the solid matrix
US Patent #US20150032427 A1
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HOSSR&D 100 Award Nomination
• HOSS was selected as one of the finalist for the R&D 100
Award in two different categories: Software/Services and
Analytical/Test
• The finite element method is used to analyze a material or
object and how it responds to deformation. The discrete element
method analyzes stresses and displacements in a volume containing a
large number of particles, such as grains of sand. Fluid dynamics
analyzes the fluid flow inside, around or through solid
domains.
• With these processes combined, HOSS represents a paradigm
shift when it comes to generating accurate simulations of material
deformation, fracture and failure.
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HOSS Simulation Examples
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HOSS – Solid3D Fracture – SHPB Experiments
Validation of a three-dimensional finite-discrete element method
using experimental results of the Split Hopkinson Pressure Bar
test, Int. J. Rock Mech. Mining Sc. 70:101-108
Animation of the Stress Wave
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HOSS – Solid3D Fracture – SHPB Experiments
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HOSS – Solid2.5D Impact with Fracture – Plane Glass
5 m/s, 2 layers solid-like shell elements
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HOSS – SolidBrick Wall under Blast Load
• 5200 bricks 0.39mx0.19mx0.19m
• 31k finite elements• Run on 64 processors
in 6 hours
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HOSS – SolidBrick Wall under Blast Load
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HOSS – SolidMining Explosives and Slope Stability
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HOSS – Solid3D Impact with Fracture
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HOSS – SolidModern Buildings
• A simplified 3D model of a 51 stories building was built.
• A relaxation step was run in order to apply gravity to the
model
• After the relaxation step, the elements composing the mesh for
floors #37 thru #39 was considered to be weakened (i.e., no
cohesive strength at all)
• As a consequence, the upper floors start to accelerate
downwards, generating a progressive collapse of the building
• Number of Elements: 884k• Run on 552 processors for 100
hours
255
m
50 m
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HOSS – SolidModern Buildings
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HOSS – Solid3D Building under Blast Loading
35 m
Pressure
Pressure
Time
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HOSS – Solid3D Building under Blast Loading
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HOSS – SolidModern Buildings under Earthquake Loads
• A simplified 3D model of a cooling tower was built
• A relaxation step was run in order to apply gravity to the
model
• After the relaxation step, the base of the cooling tower was
shaken following an earthquake signal in three directions
• As a consequence, the stress wave propagates through the
structure of the tower, generating damage at the base and at the
top
• Number of Elements: 120k• Run on 552 processors for 16
hours
130
m
60 m
110 m
Base is shaken following an earthquake signal
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HOSS – SolidModern Buildings under Earthquake Loads
Severe Earthquake
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HOSS – SolidModern Buildings under Earthquake Loads
Extreme Earthquake
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Next Development Steps…
• Develop 3D fluid solver
• Coupling fluid and solid solvers in 2D/3D
• Extending material modeling to address metals
• Incorporate rebars
• etc…
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Summary
• HOSS has been under development at LANL for 12+ years
• The tool has been advanced incrementally to include
multi-physics solvers
• HOSS has been applied to a wide range of programs and
problems
• HOSS can be used to help inform other engineering analysis
tools
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Questions?POCs:
– Esteban Rougier, [email protected], 505-667-1733
– Earl E. Knight, [email protected], 505-667-5584
– Zhou Lei, [email protected], 505-667-2632
HOSS: A Toolkit for Non-Linear Damage Prediction for NPH Risk
AssessmentsWhy HOSS at LANL�Nuclear Source PhenomenologyHOSS�Hybrid
Optimization Software SuiteFDEM in a Nutshell�Hybrid
Continua-DiscontinuaFDEM in a Nutshell�Hybrid
Continua-DiscontinuaHOSS�Software in ActionAdvanced Developments
under HOSS�Solid Material ModelAdvanced Developments under
HOSS�Solid Material ModelAdvanced Developments under HOSS�Smooth
Contact AlgorithmAdvanced Developments under HOSS�Unified Cohesive
ModelAdvanced Developments under HOSS�1st Generation vs. Next
GenerationSolver for Fracking�Integrated Solid–Fluid Solver
(ISF)HOSS�R&D 100 Award NominationSlide Number 14HOSS –
Solid�3D Fracture – SHPB ExperimentsHOSS – Solid�3D Fracture – SHPB
ExperimentsHOSS – Solid�2.5D Impact with Fracture – Plane GlassHOSS
– Solid�Brick Wall under Blast LoadHOSS – Solid�Brick Wall under
Blast LoadHOSS – Solid�Mining Explosives and Slope StabilityHOSS –
Solid�3D Impact with FractureHOSS – Solid�Modern BuildingsHOSS –
Solid�Modern BuildingsHOSS – Solid�3D Building under Blast
LoadingHOSS – Solid�3D Building under Blast LoadingHOSS –
Solid�Modern Buildings under Earthquake LoadsHOSS – Solid�Modern
Buildings under Earthquake LoadsHOSS – Solid�Modern Buildings under
Earthquake LoadsNext Development Steps…SummarySlide Number 31
