In the BLANK definition page, the user may define part, material, thickness, weld joint between multiple blanks and blank symmetry condition. Its interface for blank definition is shown in Figure 8.2.20.
Figure 8.2.20 Blank definition page
8.2.4.1 GEOMETRY
PARTS
Allow the user to define blank by selecting part or import mesh file directly. After clicking the Parts¡ button as illustrated in Figure 8.2.21, the DEFINE GEOMETRY dialog box, as shown in Figure 8.2.22, is displayed.
Figure 8.2.21 Blank Part
Figure 8.2.22 Define Geometry dialog box
ADD PART¡: This function allows user to define blank by selecting one or more parts from the part list. Selected parts are highlighted in parts list and on the screen.
REMOVE PART: This function allows the user to remove selected parts from the part list.
ADD ELEM¡:This function allows the user to add selected elements to selected part.
COPY ELEM¡: This function allows the user to copy or offset new elements from existing elements. New elements will be added to the part, which is defined as blank.
SPLIT PART: This function allows user to split the blank into several blanks, and then the blanks can be defined different materials and properties. So the user can easily generate the blank of weld forming simulation.
DISPLAY: Allow the user to display all the parts defined as the blank. The user may easily check and repair the mesh without displaying other parts on the screen.
EXIT: Allow the user to dismiss the DEFINE GEOMETRY dialog box.
After the user defines blank parts, all defined parts are displayed in the list under Part. A default material and property is assigned for the part. The user may change the default material, thickness and property for each part.
MATERIAL
The Auto Setup defines a default type 36 material for blank part. The user may click under material to modify or create a
material as shown in Figure 8.2.23. Material definition interface is shown in Figure 8.2.24.
Figure 8.2.23 Define material
NOTE: If the Part has no defined material, the material bar will display None in red. The program will prompt the user to define material for this part. In Auto Setup, the user must define the parameters labeled in red. After defining the material, the material name is displayed on the button.
Figure 8.2.24 Material Define dialog box
TYPE: Displays current user defined material type. eta/DYNAFORM supports several sheet forming material types of LS-DYNA, such as: 1, 18,24, 36, 37, 39 and 64.
NAME: Material name. Displays the defined material name.
NEW¡: Allows the user to setup a new material. After clicking this button, the program will display the Type list. The user may select one of the types from the list as shown in Figure 8.2.25. The MATERIAL dialog box as shown in Figure 8.2.26 is displayed.
Figure 8.2.25 Select material type
Figure 8.2.26 Material Define
Forming Limit Curve (FLC): This parameter is only necessary for material type 39.
At this time, <NONE> is displayed behind FLC curve to indicate there is
no FLC curves defined. If the user needs to define FLC curve for post
processor, click button
to create a FLC curve. When the user enters key word files, the program
automatically defines FLC information, including FLC curve, FLD0 (true and nominal/engineering)
which are output to index file. The post processor will load the FLC
information though the index file written by eta/DYNAFORM.
NOTE: The FLC curve defined in Auto Setup is represented in engineering strain.
After entering FLC curve edit dialog box, the user may enter coordinates of the data points directly in INPUT page to define the FLC curve. Else, the user may switch to FORMULA page to define FLC curve using KEELER¡¯s empirical formula. After the user enters appropriate n and t value, click the APPLY button to generate the FLC. The FLC curve is displayed in the show curve interface as shown in Figure 8.2.27. Detailed description of curve manager operation is provided in Section 8.2.6.5.
Figure 8.2.27 FLC Curve
EDIT¡: Allow the user to edit the current material. After clicking this button, the MATERIAL dialog box as shown in Figure 8.2.28 is displayed.
Figure 8.2.28 Material Edit dialog box
NOTE: Material edit dialog box and material define dialog box are basically similar. The user may modify any parameter in the dialog box, except the material type. If the user needs to change the material type, he/she must redefine the material properties.
IMPORT: Allow the user to import a material file. The extension of the file name is ¡°.mat¡±. After clicking this button, the program displays the import material window as shown in Figure 8.2.29.
Figure 8.2.29 Input Material window
PREVIEW: The user may preview stress strain curve of selected material. See Figure 8.2.30.
Figure 8.2.30 Material Stress-Strain Curve Preview
If the user defines a material for the blank, the preview function will activate the comparison option. This option allows the user to compare the stress strain curve of the defined material and the selected material from the library . See Figure 8.2.31 for a sample comparison.
Figure 8.2.31 Material Stress Stain Curve Comparison
The magenta curve is selected reference material curve. The blue curve is the user defined material curve. The name of current selected material and defined material are both displayed on the top of preview window. Name listed in the parentheses is the name of defined material.
After selecting a file, the user may click IMPORT button to import selected material and assign it to selected blank part.
EXPORT: Allow the user to export current material to a file. File is saved with an extension ¡°.mat¡±. See Figure 8.2.32 for the export GUI window.
Figure 8.2.32 Export Material to a File
MATERIAL LIBRARY: This function enables the user to select a material from the native material library in eta/DYNAFORM. The material standard list will pop up after clicked the Material Library¡ button as shown in Figure 8.2.33 shown. The user can select a material standard from the list. There are four type of standard in eta/DYNAFORM. The available standards are U.S., JAPAN, CHINA and EUROPE.
Figure 8.2.33 Material Library Standard
After selecting a material library standard, the program will display the material library GUI as shown in Figure 8.2.34. Then, the user may select one of materials from library for the blank.
Figure 8.2.34 GUI of Material Library
EDIT MATERIAL LIBRARY: This function enables the user to edit the material library, such as Add, Delete and Modify material. After clicking this button, the program will display the Material Library Edit dialog box as shown in Figure 8.2.35.
Figure 8.2.35 Edit Material Library dialog box
l MATERIAL TYPE: The user may switch the material type to select the corresponding material from material library. There are two types of materials in eta/DYNAFORM: Steel and Aluminum.
l STRENGTH LEVEL: The user can switch the material level to select the corresponding material from material library: Middle, Medium, High, Advanced High, Hot Roll and Stainless.
l TYPE ID: The user may switch the DYNA material type ID to select the corresponding material form material library. There are six material type ID: 1, 18, 24, 36, 37, 39 and 64.
l ADD¡: Import a material file to the material library. The imported material will be added to the material library. Refer to the LS-DYNA User¡¯s Manual of for description of the material types.
l
: The
user needs to pre-select a
material from the material list. Then, click those two buttons to change the
position of the material in the list. Refer to the Figure 8.2.36 for an example.
a) Before Moved b) After Moved
Figure 8.2.36 Change the position of material in material list
l RENAME: Enable the user to change the material name. The MODIFY NAME dialog box as shown in Figure 8.2.37 is displayed. The user may enter the new name in the edit box and click the OK button to accept the modification.
Figure 8.2.37 Modify Material Name dialog box
l DELETE: Enable the user to delete the selected material from material library.
l OK: Save the current setting and exit the Material Library Edit dialog box. The program will display a Question dialog box and prompt the user to overwrite the index as shown in Figure 8.2.38.
Figure 8.2.38 eta/DYNAFORM Question dialog box
l CANCE: Exit the Material Library Edit dialog box without saving the modification.
THICKNESS
Under the default condition, all blank thickness is defined with default thickness in new setup. The user may specify different thickness for each part below the thickness bar.
PROPERTY
The program specifies a default property for each defined blank part. The user does not need to modify property under normal situation. The blank property includes selection of element formulation, selection of integration points number in blank thickness direction, and shear correction factor. See Figure 8.2.39 for the define property GUI window.
Figure 8.2.39 Define Property
ELEMENT FORMULATION: Allow the user to select an element formulation for shell element. eta/DYNAFORM provides 16 regular shell element formulations. The default element formulation is BELYSTSCHKO-TSAY. This formulation is the most commonly used and most efficient in current sheet forming simulation. For springback calculation, the user may select Full Integration element formulation.
NUMBER OF INTEGRATION POINTS: The default number of through thickness integration points is set as five. More through thickness integration points may result in accurate simulation. However, the simulation time is also increased drastically. Despite draw forming simulation with springback, the default 5 integration points are good for most cases. For springback simulation, 7 integration points is suggested as the best option.
OK: Save current modification and exit define property dialog box.
DEFAULT: Use default value for all parameter.
CANCEL: Exit dialog box without saving current modification.
8.2.4.2 SYMMETRY
This function allows the user to add symmetry boundary condition or 1/4 symmetry condition to the blank. For completely symmetrical parts, the user may only define one half blank mesh and add symmetrical condition along the line of symmetry to save calculation time. For 1/4 symmetry parts, the user only needs to define the 1/4 blank mesh. Under default condition, the program considers the input as a whole blank. It displays NO SYMMETRY next to SYMMETRY TYPE, as shown in Figure 8.2.40. If the user defines symmetry or 1/4 symmetry, the program will display the defined symmetry type in the dialog box.
Figure 8.2.40 Define Symmetry
1/2 SYMMETRY
This function allows the user to define 1/2 symmetry blank. The GUI window is shown in Figure 8.2.41.
Figure 8.2.41 Define Symmetry Plane
SYMMETRY AXIS: This function displays the current user defined symmetry plane information. In new setup, the symmetry plane is specified by a point, a vector and WCS direction.
O(0,0): Indicate the required position of symmetry plane the vector starting point position for the defined plane.
X(1,0): Define the end point position of the vector for symmetry plane.
UW-PLANE: eta/DYNAFORM adopts a plane that is parallel to WCS¡¯s UW plane as symmetry plane. The user may specify the plane location by using select points function. XY coordinate is displayed in O (0, 0), direction is displayed as X (1, 0). A vector is displayed in WCS¡¯s UW plane on the screen to show the symmetry plane. See Figure 8.2.42 for more details.
VW-PLANE: eta/DYNAFORM adopts a plane that is parallel to WCS¡¯s VW plane as symmetry plane. The user may specify the plane location by using select points function. XY coordinate is displayed in O (0, 0), direction is displayed as X (0,1).
2 POINTS ON UV-PLANE: Enable the user to select two points to define a vector. This vector forms a symmetry plane with WCS¡¯s W axis. The first point of the vector specifies the position of the plane.
SELECT POINT(S): Allow the user to select one or two points to specify symmetry plane. If the user selects UW-plane or VW-Plane, then only one point is required to specify the plane location. If the user selects 2-Points on UV-plane, then two points are required to define symmetry plane.
TOLERANCE: The user may adjust this value to search for nodes in the symmetry plane. After defining the plane, the program will change this tolerance to automatically search for the required nodes to add symmetry boundary condition. Default tolerance is 0.01. If there are nodes with larger tolerance from the defined symmetry plane, the user may adjust this value to extend the search range.
Figure 8.2.42 Define Symmetry
1/4 SYMMETRY
This function allows the user to add symmetry boundary for 1/4 symmetry parts. Its basic operation is same as 1/2 symmetry parts. After defining a vector, the program automatically generates a vector that is normal to the previous vector to specify another symmetry plane. See Figure 8.2.43 for more details.
Figure 8.2.43 Define 1/4 Symmetry
8.2.4.3 WELDS
The user may conveniently set sheet forming of tailor welded blank and composite blank. After the user defined multiple blank parts, the weld option appears in Blank setup page, as shown in Figure 8.2.44.
Figure 8.2.44 Welded Blank Define
If the user has already defined several welding seams, information of welding seams will be displayed in welds list.
ADD¡
This function allows the user to select adjacent nodes to define weld element. After clicking this button, the DEFINE BLANK WELD dialog box, as shown in Figure 8.2.45, is displayed.
NOTE: In LS-DYNA, the defined node pair for weld must be two different nodes at different locations. Different nodes at same location or identical node are not allowed as node pair. In order to reduce the preparative time for user, eta/DYNAFORM will separate automatically the identical nodes which are used to define the weld. User only needs to add the corresponding elements to different parts.
Figure 8.2.45 Define Weld dialog box
NODAL PAIRS: Display number of nodal pairs. After the user selecting nodal pairs to define weld, the number is displayed in the data box.
OVERLAP BLANK: The user needs to select this option for overlap blank. After selecting this option, the line connecting the nodal pair must be normal to its connecting element.
WELD WIDTH: Specifies weld width. Default width is 1.0 (mm). If the distance between selected node pair is smaller than this width, the program will define weld for the node pair. The user may adjust the weld with to include the required nodal pairs with greater distance.
WELD¡: The user may click this button to select nodal pair. After clicking this button, the program display the select nodal pair dialog box. The user may select two rows of nodes for required weld line. After selecting the nodes, the program will automatically define weld on nodal pairs, and highlight the welds as shown in Figure 8.2.46.
Figure 8.2.46 Weld Define
If there is only one row of nodes, the program will separate the node and offset it automatically as shown in Figure 8.2.47.
(a) (b)
Figure 8.2.47 Node Offset (a) Before (b) After
DELETE: This button allows the user to delete all current nodal pairs.
FAILURE: The user may select failure criteria for the weld.
NEVER FAILURE: Under default condition, select NEVER FAILURE option to enable no failure at the welds during the simulation.
CONDITIONAL FAILURE: Allow the user to define conditional failure criteria and the relevant parameters. Detailed description is available in LS-DYNA User¡¯s Manual.
EDIT
This function allows the user to edit the defined weld. Similar to define weld, the user may delete selected nodal pair, add new nodal pair, modify weld failure criteria, etc.
DELETE
After defining a weld line, information of the weld is displayed in the weld list. It includes number of nodal pairs, failure rule, as shown in Figure 8.2.48. The user may delete a weld by clicking the Edit button and the Delete button to delete the current weld.
Figure 8.2.48 Welds List
8.2.4.4 CONTACT
For overlap blanks, the contact interface between blank parts has to be defined. The user may modify contact parameters, such as friction coef., contact coef. type, etc. as shown in Figure 8.2.49. For general welded blank, it is not unnecessary define the contact between the blank parts.
Figure 8.2.49 Define Contact Between Blanks
USE CONTACT BETWEEN BLANK PARTS
This option is only necessary for overlap blanks.
FRICTION COEF
Define friction coefficient between blank parts. Default friction coefficient is 0.125.
ADVANCED¡
The user may modify some contact parameters between blanks through advanced options as shown in Figure 8.2.50.
Figure 8.2.50 Define Contact Advanced Parameter
CONTACT TYPE: This function allows the user to select contact type. eta/DYNAFORM includes commonly used contact types for the blank.
Figure 8.2.51 Define Contact Type
STATIC FRICTION COEF: Allow the user to define static friction coefficient. Default value is 0.125.
VISCOUS FRICTION COEF: Allow the user to define viscous friction coefficient. Default value is 0.
VISCOUS DAMPING COEF: Allow the user to define viscous damping coefficient. Default value is 20.0.
DYNAMIC FRICTION COEF: Allow the user to define dynamic friction coefficient. Default value is 0.
DECAY COEF: Allow the user to define decay coefficient. Default value is 0.