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Chapter 2. Elements

The following elements can be used in an explicit dynamic analysis:

- LINK160- BEAM161- PLANE162- SHELL163- SOLID164- COMBI165- MASS166- LINK167

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Element Name

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Nodes I, J, K

(K is the orientation node) Degrees of Freedom UX, UY, UZ, VX, VY, VZ, AX, AY, AZ Note For explicit dynamics analyses, V (X, Y, Z) refers to nodal velocity, and A (X, Y, Z) refers to nodal acceleration. Although V (X, Y, Z) and A (X, Y, Z) appear as DOF s, they are not actually physical DOF s. However, these quantities are computed as DOF solutions and stored for post-processing.

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Element Name

BEAM161

Nodes I, J, K (K is the orientation node) Degrees of Freedom UX, UY, UZ, VX, VY, VZ, AX, AY, AZ, ROTX, ROTY, ROTZ Note For explicit dynamics analyses, V (X, Y, Z) refers to nodal velocity, and A (X, Y, Z) refers to nodal acceleration. Although V (X, Y, Z) and A (X, Y, Z) appear as DOF s, they are not actually physical DOF s. However, these quantities are computed as DOF solutions and stored for post-processing.

You can choose from the following materials when working with BEAM161, with the restrictions as noted:

- Isotropic- Elastic Bilinear- Kinematic (Except KEYOPT(1) = 2)- Plastic Kinematic (Except KEYOPT(1) = 2)- Viscoelastic (KEYOPT(1) = 1 only)- Power Law Plasticity (KEYOPT(1) = 1 only)- Piecewise Linear Plasticity (KEYOPT(1) = 1 only)

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PLANE162 Input Summary

Element NamePLANE162Nodes I, J, K, LDegrees of Freedom UX, UY, VX, VY, AX, AY Note For explicit dynamic analyses, V (X,Y) refers to nodal velocity, and A (X,Y) refers to nodal acceleration. Although V (X,Y) and A (X,Y) appear as DOF s, they are not actually physical DOF s. However, these quantities are computed as DOF solutions and stored for post-processing.

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SHELL163 Input Summary

Element NameSHELL163Nodes I, J, K, LDegrees of Freedom UX, UY, UZ, VX, VY, VZ, AX, AY, AZ, ROTX, ROTY, ROTZ Note For explicit dynamics analyses, V (X, Y, Z) refers to nodal velocity, and A (X, Y, Z) refers to nodal acceleration. Although V (X, Y, Z) and A (X, Y, Z) appear as DOF s, they are not actually physical DOF s. However, these quantities are computed as DOF solutions and stored for post processing.

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SOLID164 Input Summary

Element NameSOLID164Nodes I, J, K, L, M, N, O, PDegrees of Freedom UX, UY, UZ, VX, VY, VZ, AX, AY, AZ Note For explicit dynamics analyses, V (X, Y, Z) refers to nodal velocity, and A (X, Y, Z) refers to nodal acceleration. Although V (X, Y, Z) and A (X, Y, Z) appear as DOF s, they are not actually physical DOF s. However, these quantities are computed as DOF solutions and stored for post-processing.

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For this element, you can choose from the following materials:

- Linear Elastic Spring- Linear Viscous Damper- Elastoplastic Spring- Nonlinear Elastic Spring- Nonlinear Viscous Damper- General Nonlinear Spring- Maxwell Viscoelastic Spring- Inelastic Tension or Compression-Only Spring

COMBI165 Input Summary

Element NameCOMBI165NodesI, JDegrees of Freedom UX, UY, UZ, VX, VY, VZ, AX, AY, AZ (KEYOPT(1) = 0)ROTX, ROTY, ROTZ (KEYOPT(1) = 1)NoteFor explicit dynamics analyses, V (X, Y, Z) refers to nodal velocity, and A (X, Y, Z) refers to nodal acceleration. Although V (X, Y, Z) and A (X, Y, Z) appear as DOFs, they are not actually physical DOFs. However, these quantities are computed as DOF solutions and stored for post processing.

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MASS166 Input Summary

Element NameMASS166Nodes IDegrees of Freedom UX, UY, UZ, VX, VY, VZ, AX, AY, AZ Note For explicit dynamics analyses, V (X, Y, Z) refers to nodal velocity, and A (X, Y, Z) refers to nodal acceleration. Although V (X, Y, Z) and A (X, Y, Z) appear as DOF s, they are not actually physical DOF s. However, these quantities are computed as DOF solutions and stored for post-processing.

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The element is defined by nodes I and J in the global coordinate system. Node K defines a plane (with I and J) containing the element s-axis. The element r-axis runs parallel to the length of the element and through nodes I and J. Node K is always required to define the element axis system and it must not be colinear with nodes I and J. The location of node K is used only to initially orient the element. Real constants for this element are link area (AREA) and offset for cable (OFFSET). For a slack element, the offset should be input as a negative value. For an initial tensile force, the offset should be positive.The force, F, generated by the link is nonzero if and only if the link is in tension. The force is given by:

F = K max ( L,0.)

where L is the change in length

L = current length - (initial length - offset)

and the stiffness is defined as:

K = E*AREA/(INITIAL LENGTH OFFSET)

You can use only the material type cable for this element. For this material, you need to define the density (DENS) and Young's modulus (EX) or load curve ID.

LINK167 Input Summary

Element NameLINK167Nodes I, J, K (K is the orientation node)Degrees of Freedom UX, UY, UZ, VX, VY, VZ, AX, AY, AZ NoteFor explicit dynamics analyses, V (X, Y, Z) refers to nodal velocity, and A (X, Y, Z) refers to nodal acceleration. Although V (X, Y, Z) and A (X, Y, Z) appear as DOF s, they are not actually physical DOF s. However, these quantities are computed as DOF solutions and stored for post-processing.

Chapter 3. Analysis Procedure

The procedure for an explicit dynamics analysis consists of three main steps:

1- Build the model

2- Apply loads and obtain the solution

3- Review the results

3.1. Build the Model

Main Menu> Preferences to LS-DYNA Explicit

- Define the element types and real constants- Specify material models- Define the model geometry- Mesh the model- Define contact surfaces

3.1.1. Define Element Types and Real Constants

Main Menu> Preprocessor> Element TypeMain Menu> Preprocessor> Real Constants

3.1.2. Specify Material Properties

Main Menu> Preprocessor> Material Props> Material Models

In order to specify an orthotropic model that is not aligned with the global Cartesian coordinate system, you must first define the local coordinate system with the EDLCS command (menu path

Main Menu> Preprocessor> Material Props> Local CS> Create Local CS.)

For some material models, you may also need to use the EDCURVE command to define data curves associated with the material (e.g., a stress-strain curve). (To access EDCURVE in the GUI, pickMain Menu> Preprocessor> Material Props> Curve Options.)

3.1.3. Define the Model Geometry

3.1.4. Mesh the Model

Meshing involves three main steps:

- Set the element attributes- Set mesh controls- Generate the mesh

MAIN Menu> Preprocessor> Meshing> Mesh Tool

3.1.5. Define Contact Surfaces

Main Menu> Preprocessor> LS-DYNA Options> Contact> Define Contact

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Components:

Menu> Select> Comp/Assembly> Create Component

Rigid Bodies:

- Select Rigid Element

- The Definition of PART

Main Menu> Preprocessor> LS-DYNA Options> >Part Option

Deform to Rigid

Main Menu> Solution>Rigid-Deformable>switch

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Normal Vector of surface:

view normal vectors:

Utility Menu>PlotCtrls>Symbols- >ESYS(Element Coordinate system)

Inverse direction of normal vectors:

Main Menu > Preprocessor>Modeling>Create>Contact Pair-- >Flip Normals

3.2. Apply Loads and Obtain the Solution

Array Parameters:

Menu> Parameters> Array Parameters> Define/Edit

Menu> Solution> Loading Options> Specify Loads

) (. Basic input for this command is a component name or part number and two array parameter names or a load curve ID number (LCID). The component specified must contain the nodes or elements on which the load is being applied. The array parametersspecified must contain time varying load data (one array for time values and one array for the corresponding load values; the two arrays must be the same length). As an alternative to inputting the array parameters on the EDLOAD command, you can define the load curve using the EDCURVE command

Loads Applicable in an Explicit Dynamics Analysis

3.2.2. Initial Velocities

only shell and beam elements have rotation degrees of freedom

Menu> Solution> Initial Velocity

Main Menu> Solution> Initial Velocity> On Nodes> w/Nodal Rotate (VELO option)Main Menu> Solution> Initial Velocity> On Nodes> w/Axial Rotate (VGEN option)Main Menu> Solution> Initial Velocity> On Parts> w/Nodal Rotate (VELO option)Main Menu> Solution> Initial Velocity> On Parts> w/Axial Rotate (VGEN option)

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3.2.3. Constraints

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Menu> Solution> Constraints> Apply

4.2.2. Welds

Main Menu> Preprocessor> LS-DYNA Options> Spotweld> MasslessSpotwld

Main Menu> Preprocessor> LS-DYNA Options> Spotweld> GenrlizdSpotwld

4.5. Temperature Loading

You may need to define temperature loading in an explicit dynamic analysis in order to accommodate temperature dependent materials, or to include the effects of thermally induced stresses. Temperature loading is applicable to the PLANE162, SHELL163, and SOLID164 element types. The ANSYS LS-DYNA program offers several types of temperature loading:

- Time-varying temperature applied to a nodal component (EDLOAD)

- Constant temperature applied to all nodes in the model (TUNIF / BFUNIF)

- Temperature results from an ANSYS thermal analysis applied as non-uniform temperature loads (that do not vary with time) in a subsequent explicit dynamic analysis (LDREAD; also requires a sequential solution)

Chapter 5. Solution Features

TIME CONTROLS

POST1 is used to review results over the entire model at specific time-points. POST26 is used to track specific nodal and element result items over a more detailed load history.

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TRANSIENT DYNAMIC ANALYSIS

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