Introduction LS-DYNA Session delivered by Mr.Suman M.L.J

Intro for Ls dyna

1. PEMP
AME2510
M.S. Ramaiah School of Advanced Studies, Bengaluru
Introduction LS-DYNA
Session delivered by:Session delivered by:
Mr.Suman M.L.J.Mr.Suman M.L.J.

2. PEMP
AME2510
M.S. Ramaiah School of Advanced Studies, Bengaluru
Introduction to LS-Dyna
Applications of LS-Dyna
LS-Dyna analysis capabilities
Features available in LS-Dyna
Comparison of Implicit and Explicit Solution Techniques
Element Library available in LS-Dyna
Material Library available in LS-Dyna
Types of Contact available in LS-Dyna
Time Integration
Output files
Post processing
Session Topics
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3. PEMP
AME2510
M.S. Ramaiah School of Advanced Studies, Bengaluru
Introduction
LS-Dynaisadvancedgeneralpurposemulti-physicssimulation
softwaredevelopedbyLivermoreSoftwareTechnology
Corporation[LSTC].
LS-DynaisaNon-linearExplicitTransientDynamicFEcode
Originatedfromthe3-DFEAprogramDYNA-3Ddevelopedby
Dr.John.O.HallquistatLawrenceLivermoreNational
Laboratory,Californiain1976.
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4. PEMP
AME2510
M.S. Ramaiah School of Advanced Studies, Bengaluru
ItwasdevelopedtosimulatetheimpactofDial-a-yieldnuclear
bombforlowaltitudereleasewithimpactvelocityofaround
40m/s.
Theearlyapplicationswereprimarilyforthestressanalysisof
structuressubjectedtoavarietyofimpactloading.
Definingasuitablemeshforhandlingcontactwasoftenvery
difficult.Thefirstversioncontainedtrusses,membranes,anda
choiceofsolidelements.
PURPOSE OF DEVELOPMENT
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5. PEMP
AME2510
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CAPABILITIES
LS-DYNA is not limited to any particular type of simulation.
In a given simulation, any of LS-DYNA's many features can
be combined to model a wide variety of physical events.
An example of a simulation that involves a unique
combination of features is the NASA JPL Mars Pathfinder
landing which simulated the space probe's use of airbags to aid
in its landing.
Airbag analysis
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6. PEMP
AME2510
M.S. Ramaiah School of Advanced Studies, Bengaluru
Non-lineardynamicsandquasi-staticproblems,especially
thoseinvolvingImpact,contactandotherhighlydiscontinuous
events.
Itsupportsstress-displacementanalysisaswellasfully
coupledphysicsanalyses,suchascoupledtemperature-
displacementandcoupledfluid-structuralanalyses.
Formaterialflowmodeling,LS-DynausesclassicEulerian
frameofreferenceinwhichthefiniteelementmeshdoesnot
distort;butremainsfixedinspace.
LS-Dynaelementlibrarycomprisesofcontinuum,structural,
inertial,rigid,capacitance,connectors,cohesive,spring,
dashpot,andspecialpurposeelements.
CAPABILITIES CONTINUED……
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7. PEMP
AME2510
M.S. Ramaiah School of Advanced Studies, Bengaluru
TheEulerianformulationinLS-Dynaallowsthemodelingof
notonlyliquidsandgasesbutalsostructuralmateriallikesteel
PrescribedconditionsinLS-Dynaincludeamplitudecurves,
initialconditions,boundaryconditionsandloads.
Kinematicconstraints,contactmodelingareunique
capabilitiesinLS-Dyna.
Specializedcapabilitiesformodelingairbags,seatbeltsand
sensorshavetailoredLS-Dynaforapplicationsinthe
automotiveindustry.
Smoothed-particlehydrodynamics(SPH)isacomputational
methodusedforsimulatingfluidflows.
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8. PEMP
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Fluid analysis
Fluid analysis
Eulerian capabilities
ALE (Arbitrary Lagrangian-Eulerian)
Fluid-structure interactions
FEM-rigid multi-body dynamics coupling (MADYMO)
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9. PEMP
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M.S. Ramaiah School of Advanced Studies, Bengaluru
CAPABILITIES CONTINUED………
Nonlinear dynamics
Rigid body dynamics
Quasi-static simulations
Linear static
Thermal analysis
Underwater shock
Failure analysis
Crack propagation
Real-time acoustics
Ballistics
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10. PEMP
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AUTOMOTIVE APPLICATIONS
a.Airbag deployment
b.Frontal analysis
c.Side impact analysis
d.Pedestrian safety
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11. PEMP
AME2510
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•Crashworthiness Analysis
Frontal Crash Analysis
Side impact Analysis
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LS-DYNA's specialized Automotive
features:
1.Seatbelts
2.Slip rings
3.Pretensioners
4.Retractors
5.Sensors
6.Accelerometers
7.Airbags
8.Hybrid III dummy models
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14. PEMP
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M.S. Ramaiah School of Advanced Studies, Bengaluru
Aerospace applications
a.Blade containment
b.Bird strike
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15. PEMP
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1)Metal cutting process
2)Metal forming process
3)Stamping
4)Deep drawing
5)Hydro forming
6)Rolling
7)Extrusion
8)Drilling
9)Machining
Metal forming and
manufacturing
applications
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16. PEMP
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OTHER APPLICATIONS
•Drop testing.
•Can and shipping containers.
•Biomedical .
•Seismic study
•Civil engineering applications
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17. PEMP
AME2510
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ELEMENTS AVAILABLE IN DYNA
•Different solid elements
•8-node thick shells
•Different 3-and 4-node shells
•Beams
•Welds
•Trusses and cables
•Nodal masses
•Lumped inertias
•Arbitrary Lagrangian/Eulerian
elements
•Eulerian elements
•Element Free Galerkin
formulations
•SPH elements
•Elements for 2D-analysis
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18. PEMP
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MATERIAL MODELS AVAILABLE IN
DYNA
1.Provide Constitutive equations for more than 120 material
models
2.Default parameters from best practices
3.Material Models
•Elastic
•Elastic-Plastic
•Viscoelastic
•Rubber
•Foams
•many more …
4. SECTIONS
•Solids
•Shells
•Bars
•thick shells
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19. PEMP
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MATERIAL LIBRARY AVAILABLE IN
LS-DYNA
Linear Elastic Models
•Isotropic (MAT1)
•Orthotropic (MAT2)
•Anisotropic (MAT2)
Nonlinear Elastic Models
•Blatz-Ko Rubber (MAT7)
•Mooney-Rivlin Rubber (MAT27)
•Viscoelastic (MAT6)
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Plasticity Models
•Bilinear Isotropic (MAT3)
•Temperature Dependent Bilinear Isotropic (MAT4)
•Bilinear Kinematic (MAT3)
•Plastic Kinematic (MAT3)
Plasticity Models
•Powerlaw Plasticity (MAT18)
•Rate Sensitive Powerlaw Plasticity (MAT64)
•Strain Rate Dependent Plasticity (MAT19)
•Piecewise Linear Plasticity (MAT24)
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21. PEMP
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Foam Models
•Low Density Foam (MAT57)
•Viscous Foam (MAT62)
•Mooney-Rivlin Rubber (MAT27)
•Viscoelastic (MAT6)
Spring Damper Models
•Linear Elastic Spring (MAT18)
•Linear Viscous Damper
•Nonlinear Elastic Spring
•Nonlinear Viscous Damper
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22. PEMP
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•Elasto-plastic spring
•General Nonlinear Spring
Composite Models
•Composite Damage (MAT22)
•Enhance Composite Damage(MAT54-55)
•Laminated composite Fabric (MAT58)
Others
•Rigid (MAT20)
•Cable (MAT71)
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23. PEMP
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LS-DYNA'S CONTACT
ALGORITHMS
•Flexible body contact
•Flexible body to rigid body contact
•Rigid body to rigid body contact
•Edge-to-edge contact
•Eroding contact
•Tied surfaces
•Rigid walls
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24. PEMP
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M.S. Ramaiah School of Advanced Studies, Bengaluru
CONTACT TYPES
•Single surface
•Nodes to surface
•Surface to surface
•Normal
•Automatic
•Rigid
•Tied
•Tied with failure
•Eroding
•Edge
CONTACT OPTIONS
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25. PEMP
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TIME INTEGRATION
Fornonlinearproblem,onlynumericalsolutionsare
possible.LS-DYNAusestheexplicitcentraldifferencemethodto
integratetheequationofmotion
The semi-discrete equations of motion at time n is given as
Ma
n
= P
n
-F
n
+ H
n
Where, M is the diagonal mass matrix,
p
n
accounts for external and body force loads,
F
n
is the stress divergence vector, and
H
n
is the hourglass resistance.
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26. PEMP
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OUT PUT FILES
Various binary and ascii outputs available along with
customization options
Primary binary options include
d3plot:Binary file containing voluminous data at
selected time points
d3thdt:Binary file containing time history data for
selected nodes at a number of time points
Activated using the keyword
*DATABASE_BINARY_OPTION
Output to these files controlled using the keyword
*DATABASE_EXTENT_BINARY
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ASCII output activate using keyword *DATABASE_OPTION
Primary ascii options include
GLSTAT:global statistics
SLEOUT:sliding interface energy
MATSUM:material energies
SPCFORC:SPC reaction forces
JNTFORC:joint force file
RCFORCE:Resultant contact force
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28. PEMP
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POST-PROCESSING
Key variables
1.Contact Forces
2.Stresses
3.Deformation
4.Energy plots
5.Energy absorption
6.Acceleration and velocity
7.History Variables
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29. PEMP
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ANALYSIS TECHNIQUES
Explicit
1.Ideal for Highly Dynamic
Events like Crash, explosion
analysis etc..
2.Conditionally stable when
stiffness matrix [K] is linear
i.e,{Q}=[k]{q}
Where,{Q} is nodal
forces,[k] is element
stiffness matrix,{q} is nodal
degree of freedom
3. Does not requires inversion
of nonlinear stiffness matrix
[K]
Implicit
1.Ideal for Static type of
Events like Structural
problems etc..
2.Unconditionally stable
when stiffness matrix [K] is
linear
3.Requires inversion of
nonlinear stiffness matrix
[K]
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30. PEMP
AME2510
M.S. Ramaiah School of Advanced Studies, Bengaluru
4. Global stiffness matrix [K] is
not required i.e, {R}=[K]{r}
Where, {R} is nodal loads,[k] is
Global Stiffness matrix,{r} is
global degrees of freedom of the
structure
5.Explicit calculation leads to
simple equations for each
degree of freedom
6.Explicitanalysis solves using
Central difference method
7. only stable if time step size is
smaller than critical time step
size
4.Global stiffness matrix [K] is
required.
5.Implicit calculations lead to a
system of equations including
the complete model
6.ImplicitAnalysis solves
using forward difference
method
7. For linear problems,time step
can be arbitrarily large
(always stable)
For nonlinear problems, time step
size may become small due to
convergence difficulties
max
2
crit
t t

   
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31. PEMP
AME2510
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FE MODELS FOR DYNAMIC ANALYSIS
SECTION MATERIALSECTION MATERIAL
propertiesproperties
PART IPART I
geometrygeometryTopologyTopology
PART IIPART II
CONTACT INTERFACES CONTACT INTERFACES
CONTACT ENTITIES CONTACT ENTITIES
COMMON NODES COMMON NODES
SPRINGS/ DAMPERS SPRINGS/ DAMPERS
SPOT WELDS JOINTSSPOT WELDS JOINTS
RIGID BODY MERGERIGID BODY MERGE
BOUNDARY COND. BOUNDARY COND.
STONE WALLS STONE WALLS
JOINTSJOINTS
GROUNDGROUND
INITIAL VELOCITIESINITIAL VELOCITIES
MODELMODELSETUPSETUP
OUTPUTOUTPUT
SIMUALATION TIMESIMUALATION TIME
TIME STEPTIME STEP
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32. PEMP
AME2510
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33
2
1
4
ELEMENT TYPE
THICKNESS
GEOMETRY PROPERTIES
STIFFNESS,
DENSITY
1
•Create FE Model
•Choose Material Model and Properties
•Assign Material and Property
•Assign loads and boundary condition
•Specify control parameters
•Create “.k” input file
•Solve the .k file in LS-Dyna solver to get
“d3plot” output file
•Post process the d3plot file in LS-Dyna post
processor
General Approach involved in solving LS-Dyna
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