Impact Analysis Using LS-DynaTutorial Click to edit Master subtitle style

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Ravishankar

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Problem Definition Primary requirement for the impact / drop

test are

Boundary condition Initial Velocity

Contact Definition based on element strategy.

Main Steps involved in setting up a simulation Import Geometry Define Element Type, Material, Section Properties

(Real Constants)2 2 Meshing

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Starting LS-Dyna using AnsysUsing Ansys Product Launcher. Set License to Ansys Academic Research

LS-Dyna

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GeometryImport geometry through various cad

translators using menu shown below.

Catia, Pro-e or Parasolid

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Material Models in LS-DynaMaterial input GUI consistent and similar to

implicit interface.

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Mesh and Element TypeLS-Dyna Element type in Ansys

pre-post are 16x series element. LINK160: 3-D explicit pin-jointed truss

(similar to LINK8) BEAM161: 3-D explicit beam (similar to

BEAM4) PLANE162: 2-D explicit planar solid

(similar to PLANE42) SHELL163: 3-D explicit thin shell

(similar to SHELL181) SOLID185)

SOLID164: 3-D explicit brick (similar to

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COMBI165: 3-D explicit spring or

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damper (similar to COMBIN14)

Defining ContactThere are various contact families

in LS-Dyna

Single Surface Contact Algorithm Nodes-to-Surface Contact Algorithm Surface-to-Surface Contact

Algorithm

General (Basic) Contact Family Automatic Contact Family Rigid Contact Family7 7

Tied Contact Family Tiebreak Contact Family

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Boundary ConditionApply boundary condition in the Constraints

module, it includes fixed condition for immovable parts like floor or wall.

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Boundary ConditionInitial velocity is most commonly used input

for a impact/drop test.components.

Initial Velocities are applied on node

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Solution- Ls Dyna SolverThe termination time is the actual time for

which the simulation of physical process is run (often in ms).

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Output request and frequencySpecify how often results for the entire

model are written.

can output a series of LS-DYNA ASCII output

files that contain specialized information

energy

GLSTAT BNDOUT RWFORC DEFORC MATSUM NCFORC RCFORC DEFGEO SPCFORC

- Global statistics data - Boundary condition forces and Rigid wall forces Discrete element forces Material energies summary Nodal interface forces Resultant interface forces Deformed geometry data Single point constraint reaction Nodal constraint reaction forces Rigid body data Geometry contact entities Sliding interface energies data Joint force data Node data

forces

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SWFORC RBDOUT GCEOUT SLEOUT JNTFORC NODOUT

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Post ProcessingPOST1, the ANSYS General PostprocessorAnimation Deformation, Stresses

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Post Processing : Time HistoryPOST26 Time History PostprocessorPlot time-history curves, plot acceleration,

velocity, displacement vs time .

Access LS Dyna Ascii output files.

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Example Plate impacting Plate

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DefinitionA Shell Elements drop and rebounds from a

elastic plate.

Plate measure 40*40*1 mm3 (16 elements) Dropped shell has 10mm side length and 2

mm thickness.

Drop height is 10mm Element formulation is Belutschko-Tsay Define a surface to surface contact with 2

way detection.

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Define the elastic plate as Master and 5/3/12

impacting shell as slave.

Set-UpFor model setup we use various option in

the preprocessor tab.

Create 2 areas with required dimension as

shown below (Preprocessor-Modelingcreate-).Transform drop shell to required drop

height.

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MeshingDefine Element Type 163 (Preprocessor-Elementtype-add/edit/delete-)

Part should be defined using right

combination of material , real contact , element type. Before meshing this has set and can be confirmed at status bar.

Part 1 2 Status Bar

Material 1 1

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Element Type 1 1

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Real constant 1 2

Meshing contDefine Real Constant to assign section

properties or thicknesses. For each thickness there should be one real constant. (Preprocessor-Real Constants)

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Meshing ContMaterial PropertiesDefine material properties for various parts

using option shown below. (PreprocessorMaterial Props-Material Models)

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Creating PartsAssign the correct material, section

properties and element type to create parts. be a group of elements that have the same combination of element type, real constant set, and material reference numbers (Preprocessor-Meshing Mesh Attributes)

For LS-Dyna to recognize a part, its should

Repeat this to all area/components

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Revisiting MeshingSet line seeding or element size.

(Preprocessor-Meshing-Mesh tool-Set) solid, shell or beam elements.

Mesh Volume ,Areas and lines to generate Refer images below to access the meshing

tool.

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Creating ComponentsWe need to create node and elements

components for

Adding Constrains to a group of nodes Defining Velocity to a part (part nodes need to

be grouped)Defining a master surface and node surface

(associated nodes of surface need to be grouped)To request output for required parts/region of

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In this model create node and element

component for both the areas you could name

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Adding Constrains to ModelThe plate is fixed at its boundaries

(Preprocessor-LS-DYNA-Constraints-On Nodes) desired nodes to apply the constrains. options to add constrain.

Create a node component or select the Refer images below to access the menu

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Defining contactsIn this model we will create a Automatic

Surface to Surface Contact. Choose the moving plate as contact surface and fixed plate as target surface. (Preprocessor-LSDYNA-Contact-DefineContact)

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Initial VelocityThe moving plate has initial velocity of

100,000 mm/s in vertical direction.

Initial velocity can be applied using option

under LS-Dyna Option tab as show below. (Preprocessor-LS-DYNA-Initial Velocityw/Nodal Rotate)

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Solution SettingAs per problem definition end time is

0.0002 sec, remember that most of impact problem occur over a time of ms. (Solution Time Controls Solution Time)

We now use option in the solution tab

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Output ControlsIn output controls weRequest for both Ansys and LS-Dyna Result

formats written

Set the frequency at which result files are Request for Special Ascii files which has

information on system energies, Nodal and You could request for 10 Elemental results. Ascii files at a time the mostSelect the components for which Time-History

results has to be written.27 27

frequent used are Global statistics data Boundary condition forces and energy Material energies summary Geometry contact entities Node data

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Solution and ResultsClick on the Solve option in run the

simulation (Solution Solve)

As Discussed before this example Post

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processing option are test.avi General Post Proc Time History Post Pro 5/3/12 Attached is the animation of the solved

Time- History Post ProcessingTimeHist Postpro > Variable Viewer > File

> Open > Explicit Dynamics Results (*.his) > Jobname.his

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