FLSD Damage

The Forming Limit Stress Diagram (FLSD) damage initiation criterion is intended to predict the onset of necking instability in sheet metal forming. The strain-based forming limit curves (as used in the FLD Damage criterion) are converted to stress-based curves to reduce the dependence on the strain path. This improves the performance of the FLSD damage model under conditions of arbitrary loading.

See Also
In Other Guides
Damage Initiation for Ductile Metals

A FLSD is the stress counterpart of the FLD, with the major and minor principal in-plane stresses corresponding to the onset of necking localization plotted on the vertical and horizontal axes, respectively. The FLSD damage initiation criterion requires the specification of the major principal in-plane stress at damage initiation as a tabular function of the minor principal in-plane stress and, optionally, temperature and predefined field variables, ε m a j o r F L S D ( ε min o r , θ ) . The damage initiation criterion for the FLSD is met when the condition ω F L S D = 1 is satisfied, where the variable ω F L S D is a function of the current stress state and is defined as the ratio of the current major principal stress, ε m a j o r , to the major stress on the FLSD evaluated at the current values of minor stress, ε min o r ; and temperature, θ :

ω F L S D ⁢ = ε m a j o r ε m a j o r F L S D ( ε min o r ,   θ ) .

Similar to the FLD criterion, damage due to bending deformation cannot be evaluated using this model.

Input Data Description
Major Principal Stress The maximum value of the in-plane principal limit stress.
Minor Principal Stress The minimum value of the in-plane principal limit stress.
Use temperature-dependent data Specifies material parameters that depend on temperature. A Temperature field appears in the data table. For more information, see Specifying Material Data as a Function of Temperature and Independent Field Variables.
Number of field variables Specify material parameters that depend on field variables. Field columns appear in the data table for each field variable you add. For more information, see Specifying Material Data as a Function of Temperature and Independent Field Variables.
Use damage evolution Damage evolution defines how the material degrades after one or more damage initiation criteria are met. Select the check box, and specify settings in the Damage Evolution group box; these settings are described in Damage Evolution.