Forming Limit Diagram (FLD)

The Forming Limit Diagram ( FLD ) is a map of the strain state of a model. The strains of each node are plotted onto the major and minor strain axes. The position of each point on the FLD can be used to determine what forming mode and the formability of the part in a local area. Formability describes whether the part is safe or will have areas with a tendency to split or wrinkle.

NOTE:  When displaying an FLD for a Tailor Welded Blank simulation, you toggle between materials by using the drop down menu in the top left hand corner of the viewer.

Note:  If you select a point on the Forming Limit Diagram the coordinates for the point will be displayed on the FLD as well the corresponding point on the part and on the blank will also be displayed.

Margins

The appearance of the diagram and safety limits for the FLD can be changed from the Margins button. Select the Margins button at the top of the window to open the Margins dialog box. Edit any of the margin values then click OK, the settings will be applied and the FLD updated automatically.

Safety Margin
The default Safety Margin defining the marginal splitting zone is set to the area between the Forming Limit Curve and the safety curve, which is offset below by 10%. To change this offset, change the setting in the Safety Margin field.

Note: A safety margin of 10% is typical for steels. For Aluminum a typical safety margin is 6-7%.

Plane Strain Margin
The default Plane Strain Margin defining the plane strain zone is set to the area on the FLD where the minor strain is 5% of the major strain. To change this margin, change the setting in the Plane Strain Margin field.

Thinning and Shear Margins
Thinning and Shear Margins can be defined for the Safety Zone plot. The yellow line on the right-hand side of the plot is the Thinning Margin Line. The yellow line on the left-hand side represents the Shear Margin Line. The default values are 0.023 and 0.063 for Thinning and Shear respectively, 10% of the limit values.

Low Strain Margin
A Low Strain margin can be defined for the Safety Zone plot. The Low Strain margin is a circular area centered on the origin of the Forming Limit Diagram (0% major and minor strain). The default value is 0.002.

Thinning and Shear Limits
Thinning and Shear Limits can be defined for the Safety Zone plot. The dark red line on the right-hand side of the plot is the Thinning Limit Line. The dark red line on the left-hand side represents the Shear Limit Line.