/INTER/TYPE8
Block Format Keyword This interface is used to simulate drawbeads. It is mainly used in the process industry to model metal forming.
Drawbeads are used to prevent the metal strip from sliding during the stamping process. Normals of the main segments must be oriented toward the secondary nodes (unsorted group).
Format
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/INTER/TYPE8/inter_ID/unit_ID  
inter_title  
grnd_ID_{s}  surf_ID_{m}  I_{form}  
F_{n_first}  F_{t_first}  DEPTH  T_{start}  T_{stop}  
F_{n_last}  F_{t_last} 
Definition
Field  Contents  SI Unit Example 

inter_ID  Interface
identifier. (Integer, maximum 10 digits) 

unit_ID  Unit identifier. (Integer, maximum 10 digits) 

inter_title  Interface
title. (Character, maximum 100 characters) 

grnd_ID_{s}  Secondary unsorted node
group identifier. (Integer) 

surf_ID_{m}  Main surface
identifier. (Integer) 

I_{form}  Friction penalty
formulation type.
(Integer) 

F_{n_first}  Drawbead normal force per
unit length at the first node defined in grnd_ID_{s}. (Real) 
$\left[\frac{\text{N}}{\text{m}}\right]$ 
F_{t_first}  Drawbead restraining force
per unit length at the first node defined in grnd_ID_{s}. (Real) 
$\left[\frac{\text{N}}{\text{m}}\right]$ 
DEPTH  The drawbead
depth. (Real) 
$\left[\text{m}\right]$ 
T_{start}  Start time for contact
impact computation. (Real) 
$\left[\text{s}\right]$ 
T_{stop}  Temporary deactivation
time. (Real) 
$\left[\text{s}\right]$ 
F_{n_last}  Drawbead normal force per
unit length at the last node defined in grnd_ID_{s}. Default = 0 (Real) 
$\left[\frac{\text{N}}{\text{m}}\right]$ 
F_{t_last}  Drawbead restraining force
per unit length at the last node defined in grnd_ID_{s}. Default = 0 (Real) 
$\left[\frac{\text{N}}{\text{m}}\right]$ 
Comments
 The node group for secondary surface must be an unsorted group (/GRNOD).
 I_{form} =1 is not available when using Idt =1 in option /ADMESH/GLOBAL.
 When F_{n_first} ≠ 0, normal force is computed. The normal force is due to the bending of the blank into the drawbead as the binder closes on the die. The total contact force is the sum of the restraining force and normal force.
 F_{n} represents
a limiting value. The normal force begins to develop when the distance
d between the blank and drawbead line is less than the
drawbead depth (DEPTH). When the drawbead is close to blank (distance equal to depth), this normal
force reaches a plateau F_{n}. The
value of normal force depends on the penetration as described here:
Where, $\delta =\mathit{DEPTH}d+\frac{{\mathit{Thickness}}_{\mathit{Blank}}}{2}$ .
 If F_{n_last} ≠ 0, the limit value F_{n} varies linearly between the value F_{n_first} and F_{n_last} from the first node defined in the set grnd_ID_{s} to the last node, according to the curvilinear distance between nodes. Otherwise, the limit value F_{n} is constant and equal to F_{n_first}.
 If F_{t_last} ≠ 0, the limit value F_{t} varies linearly between the value F_{t_first} and F_{t_last} from the first node defined in the set grnd_ID_{s} to the last node, according to the curvilinear distance between nodes. Otherwise, the limit value F_{n} is constant and equal to F_{t_first}.
 If DEPTH = 0 or $\frac{{F}_{n}}{DEPTH}>Stiffnes{s}_{Blank}$ , the slope of the linear part of the curve is reset to the stiffness of the blank, so that the same time step as the one without normal force is used to guarantee the stability.