Interfacing ANSYS and LS-DYNA

Sample Problem #4: Rigid Cylindrical Bar Moving Along the Z-Axis and Impacting a Plate in the X-Y Plane that is Supported by Other Plates Normal to It

 

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=0.79),

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

 

 

 

Assign Thickness to the Plates

 

 

Define material type.

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

Density (g/cm3) = 19.218

Elastic Modulus (g/msec2 cm) = 2.1

Poisson’s Ratio = 0.0

 

Inelastic, plastic kinematic material is used for group #2 with the following characteristics:

Density (g/cm3) = 7.85

Elastic Modulus (g/msec2 cm) = 2.1

Tangent Modulus (g/msec2 cm) = 1.24x10-2

Yield Strength (g/msec2 cm) = 4.0x10-3

Poisson’s Ratio = 0.3

Hardening Parameter = 1.0

 

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

Density (g/cm3) = 7.85

Elastic Modulus (g/msec2 cm) = 2.1

Tangent Modulus (g/msec2 cm) = 1.24x10-2

Yield Strength (g/msec2 cm) = 2.15x10-3

Poisson’s Ratio = 0.3

Hardening Parameter = 1.0

 

 

 

 

 

 

Create the plates

 

 

WorkPlane

            Offset Work Plane by Increment

                        Rotate +Y (90 degrees)

Create rectangle (0,0,5,31)

shift by 25,0,0

 

 

Create Volume

WorkPlane

            Offset Work Plane by Increment

                        Rotate -Y (90 degrees)

 

 

 

 

 

 

 

 

Note: Turn off smart size if it is on.

Plot

            Areas

Select Mesh Tool

Set Areas

Select the big square

Plot

            Areas

Select Mesh Tool

Set Areas

Select the small rectangle

 

 

Plot

            Elements

PlotCtrls

            Pan, Zoom, Rotate

            Click on Dynamic Mode

                        Use right mouse button

Merge nodes

Some of the nodes are in the same location. They should be merged.

 


 

Boundary conditions

PlotCtrls

            Pan, Zoom, Rotate

Click on right

Choose the nodes on the bottom of the smaller plate. Restrict them completely

 


Click on front

            Choose the nodes on the left edge of the plates. Restrict them UX, RY, RZ.

            Choose the nodes on the lower edge of the plate. Restrict them in the UY, RX, RZ

 


Contact

Make contact between a 4x4 square on the horizontal plate and the lower surface of the cylinder.

 

 

 

 

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 two plates

·         Box #2 encloses the cylinder

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

 

$

$     define section

$

*DEFINE_BOX

$        i         f         f         f         f         f         f

$    boxid       xmm       xmx       ymn       ymx       zmn       zmx

         1-7.302E-07   31.0000-7.302E-07   31.0000       0.0   5.00000

*DEFINE_BOX

$        i         f         f         f         f         f         f

$    boxid       xmm       xmx       ymn       ymx       zmn       zmx

         2-1.565E-07   4.00000-1.565E-07   4.00000   5.00500   30.0000

$

$     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       0.0       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       0.0-1.800e-03       0.0       0.0       0.0

Contact

Another method to define contact

Define contact between the lower surface of the cylinder and a 4x4 square patch of the horizontal plate. Place the text near the end of the *.k file.

 

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

$                              CONTACT DEFINITIONS                             $

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

$

*DEFINE_BOX

$        i         f         f         f         f         f         f

$    boxid       xmm       xmx       ymn       ymx       zmn       zmx

         3,0.00,4.0,0.0,4.0,0.00,0.01

$

*DEFINE_BOX

$        i         f         f         f         f         f         f

$    boxid       xmm       xmx       ymn       ymx       zmn       zmx

         4,0.00,4.0,0.0,4.0,-1.00,0.0

$

*CONTACT_TIED_SURFACE_TO_SURFACE

         0         0         0         0         3         4        0         0

 0.000     0.000     0.000     0.000     0.000             0 0.000    0.1000E+08

 1.000     1.000     0.000     0.000     1.000     1.000     1.000     1.000