Interfacing ANSYS and LS-DYNA

Sample Problem #6: Rigid Mass Falling on a plate supported by Beams

 

Pre-Processing

 

Open ANSYS

·         ANSYS Interface has pull-down menu on the top. These menus cover functions such as plotting, display, and selection of entities. Help menu is also at this location.

·         ASNSY has also menus on the left side of the screen. These menus cover pre-processing, processing, and post-processing.

·         ANSYS needs to know that you are planning to create LS-DYNA model. That is why you need to select LS-DYNA Explicit in the Preferences

In Windows, select Start

Programs

ANSYS Release 7.0

ANSYS Interactive

            In Product Selection, choose: ANSYS DYNAPrepPost

                        Run

 

 

Define element type

Element Group #1: solid element,

Element Group #2: shell element (thickness=0.25),

Element Group #3: beam element (thickness=0.5)

 

 

 

 

 


Assign Thickness to the Plates

 

 

 

 

Define material type.

Rigid material is used for group #1 with the following characteristics:

Density (lb sec2/in4) = 2.77x10-3

Elastic Modulus (lb/in2) = 3.0x108

Poisson’s Ratio = 0.3

Transnational constraint = x and y displacement

Rotational constraints = all rotations

 

Rigid material is used for group #2 with the following characteristics:

Density (lb sec2/in4) = 2.77x10-4

Elastic Modulus (lb/in2) = 3.0x107

Poisson’s Ratio = 0.3

 

Inelastic, plastic kinematic material is used for group #3 with the following characteristics:

Density (lb sec2/in4) = 2.77x10-4

Elastic Modulus (lb/in2) = 3.0x107

Tangent Modulus (lb/in2) = 3.0x104

Poisson’s Ratio = 0.3

Yield Strength (lb/in2) = 5.0x104

Hardening Parameter = 1.0

 

 

 

Create the solid

Create key points corresponding to two quarter circles in the positive-positive quarter of the x-y plane of radii 1 and 3 inches respectively.

 

 

 

 

 

Meshing the volume

 

 

 

 

 

Create the plate

 

 

 

Similar to meshing the volume, in mesh tools, choose lines, pick the straight edges of the plate, and divide them into 4 sections.

 

Create the Beams

 

 

Copy the three lines by distance DZ=-2

 

 

Mesh the lines

 

Choose the keypoint at the origin (#1) as it is not attached to any line.

Repeat the same procedure for meshing the lines at the bottom of the model and the plate. Use 2 elements per line.

Use Numbering in PlotCrls to add element number

 

 

Boundary Conditions

Plot

Lines

 

PlotCtrls

            Pan, Zoom, Rotate

                        Dynamic Mode

Click on right mouse button to adjust view

Choose the nodes on the bottom end of the vertical beams. Restrict them completely.

 

 

Add boundary conditions to nodes on planes of symmetry

 

Set Time Controls

Set Output Controls

(You can specify the output to either ANSYS, LS-DYNA, or both)

Specify the Output Frequency

 

Save File (It is very important to save in ANSYS format (*.db) since it cannot read DYNA format (*.k))

File

            Save As

                        Sample4a.db

 

 

Initial Velocity:         

Initial velocity and contact can be input in ANSYS by creating component and assigning the initial velocity or contact specification to this component. It is much easier to create boxes that enclose the nodes within specific segments of your model.  You can do this by adding the following to your *.k program. In this section two boxes are created:

·         Box #1 encloses the solid

·         Box #2 encloses the plates and the beams

Place the text near the end of the *.k file.

 

$

$     define section

$

*DEFINE_BOX

$        i         f         f         f         f         f         f

$    boxid       xmn       xmx       ymn       ymx       zmn       zmx

         1-7.302E-07       3.0-7.302E-07       3.0   -0.0001   2.10000

*DEFINE_BOX

$        i         f         f         f         f         f         f

$    boxid       xmn       xmx       ymn       ymx       zmn       zmx

         2-7.302E-07       3.0-7.302E-07       3.0      -2.3     -0.19

$

$     initial condition section

$

*INITIAL_VELOCITY

$        i         i         i

$     nsid    nsidex     boxid

         0         0         1

$        f         f         f         f         f         f

$       vx        vy        vz        wx        wy        wz

       0.0       0.0     -1000       0.0       0.0       0.0

*INITIAL_VELOCITY

$        i         i         i

$     nsid    nsidex     boxid

         0         0         2

$        f         f         f         f         f         f

$       vx        vy        vz        wx        wy        wz

       0.0       0.0       0.0       0.0       0.0       0.0

Contact

Another method to define contact

Define contact between the lower surface of the mass and the plate. Define also contact between the plate and the horizontal beams to force them to move together.

Place the text near the end of the *.k file.

 

*DEFINE_BOX

$        i         f         f         f         f         f         f

$    boxid       xmn       xmx       ymn       ymx       zmn       zmx

         3,0.00,3.0,0.0,3.0,0.00,0.01

$

*DEFINE_BOX

$        i         f         f         f         f         f         f

$    boxid       xmn       xmx       ymn       ymx       zmn       zmx

         4,0.00,3.0,0.0,3.0,-0.21,-0.20

$

*CONTACT_SURFACE_TO_SURFACE

$     ssid      msid     sstyp     mstyp    sboxid    mboxid      spr       mpr

         0         0         0         0         4         3        0         0

$       fs        fd        dc        vc       vdc    penchk       bt        dt

     0.000     0.000     0.000     0.000     0.000         0    0.000 0.100E+08

$      sfs       sfm       sst       mst      sfst      sfmt       fsf       vsf

     1.000     1.000     0.000     0.000     1.000     1.000     1.000     1.000

*CONTACT_TIED_NODES_TO_SURFACE

$     ssid      msid     sstyp     mstyp    sboxid    mboxid      spr       mpr

         0         0         0         0         4         4        0         0

$       fs        fd        dc        vc       vdc    penchk       bt        dt

     0.000     0.000     0.000     0.000     0.000         0    0.000 0.100E+08

$      sfs       sfm       sst       mst      sfst      sfmt       fsf       vsf

     1.000     1.000     0.000     0.000     1.000     1.000     1.000     1.000