/PROP/TYPE35 (STITCH)

Block Format Keyword This property describes the stitch spring. The stitch spring is characterized by complex parameterizable failure criteria, which differ in compression and tension.

If maximum deformation is greater than a failure criteria in a given direction, the spring enters a damaged mode. The mode information is transmitted to neighboring spring elements which will begin to fail. The property type STITCH must be used with spring elements.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/PROP/TYPE35/prop_ID/unit_ID or /PROP/STITCH/prop_ID/unit_ID
prop_title
Amas Elastif Xlim1     Xk
fct_ID1 fct_ID2 fct_ID3 fct_ID4 Damg Fdelay    

Definitions

Field Contents SI Unit Example
prop_ID Property identifier

(Integer, maximum 10 digits)

  
unit_ID Unit Identifier

(Integer, maximum 10 digits)

  
prop_title Property title

(Character, maximum 100 characters)

  
Amas Mass per unit length.

(Real)

 [ kg m ]
Elastif Stiffness per unit length.

(Real)

 [ N m 2 ]
Xlim1 Tension transition deformation.

(Real)

  
Xk Stiffness for interface.

(Real)

 [ N m ]
fct_ID1 Initial tension function identifier.

(Integer)

  
fct_ID2 Initial compression function identifier.

(Integer)

  
fct_ID3 Final tension function identifier.

(Integer)

  
fct_ID4 Final compression function identifier.

(Integer)

  
Damg Damage factor 0 < Damg < 1. 4
= 0
No damage.
= 1
Total damage (null stiffness after failure).

(Real)

  
Fdelay Failure delay factor.

(Real)

  

Comments

  1. There are two models defined in the property.
    First model before damage with the following inputs:
    • Elastif
    • fct_ID1 defines yield force versus strain in case of tension
    • fct_ID2 defines yield force versus strain in case of compression
    Second model after damage with the following inputs:
    • Elastif
    • fct_ID3 defines yield force versus strain in case of tension
    • fct_ID4 defines yield force versus strain in case of compression
  2. There are no default values for this property, all parameters should be defined.
  3. The damage begins when:
    • The spring reaches its strain tension limit Xlim1; or
    • A connected spring reaches its own strain tension limit.
  4. Damg is used only after n=1/Fdelay cycles:
    • Damg = 0 the spring remains on fct_ID3 and fct_ID4
    • Damg = 1 the internal force is reset to zero within one cycle

    This coefficient was introduced to improve stability when the internal forces are set to 0.0, due to failure.

    A value of 0.8 is recommended.