/MAT/LAW114 (SPR_SEATBELT)

Block Format Keyword This spring material is designed for 1D seatbelt elements.

Format

(1)	(2)	(3)	(5)	(7)	(9)
/MAT/LAW114/`mat_ID`/`unit_ID` or /MAT/SPR_SEATBELT/`mat_ID`/`unit_ID`
`mat_title`
$ρ$		`Lmin`
`K`		`C`
`fct_load`	`fct_uload`	`Xscale`	`Fscale`
`E`		`I`	`J`	`Fmax`	`Mmax`
`AS`		`R`

Definition

Field	Contents	SI Unit Example
`mat_ID`	Material identifier. (Integer, maximum 10 digits)
`unit_ID`	(Optional) Unit identifier. (Integer, maximum 10 digits)
`mat_title`	Material title. (Character, maximum 100 characters)
$ρ$	Density. (Real)	$[\frac{kg}{m^{3}}]$
`Lmin`	Minimum length for mass computation. Default = 1% of average mesh size (Real)	$[m]$
`K`	Linear loading and unloading stiffness per unit length. Used only if `fct_load` is not defined. (Real)	$[N]$
`C`	Damping. If not defined, a small amount of damping is automatically applied. 9 (Real)	$[N s]$
`fct_load`	Function identifier defining loading force versus engineering strain $f (ε)$ . (Integer)
`fct_uload`	Function identifier defining unloading force versus engineering strain $f (ε)$ . Not used when element is inside slipring or retractors. (Integer)
`Xscale`	Scale factor for $ε$ for `fct_load` and `fct_uload`. Default = 1.0 (Real)
`Fscale`	Scale factor for $f (ε)$ for `fct_load` and `fct_uload`. Default = 1.0 (Real)	$[N]$
`E`	Young's modulus for compression and bending. (Real)	$[Pa]$
`I`	Area moment of inertia bending. (Real)	$[m^{4}]$
`J`	Area moment of inertia torsion. (Real)	$[m^{4}]$
`Fmax`	Maximum force for shear and compression. (Real)	$[N]$
`Mmax`	Maximum moment for bending and torsion. (Real)	$[Nm]$
`AS`	Shear area. (Real)	$[m^{2}]$
`R`	Scaling factor for inertia. Default = 1.0 (Real)

Example (Seatbelt)

#RADIOSS STARTER
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/UNIT/1
Seatbelt
                  Mg                  mm                   s
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/MAT/SPR_SEATBELT/1/1
Seatbelt
#            Density                Lmin
                1E-6                   0    
#              KTens               CTens
               10000                 1.1
# fct_load fct_uload              Xscale              Fscale
         0         0                   0                   0
#                  E                   I                   J                FMAX                MMAX
                   0                   0                   0                   0                   0
#                 AS                   R
                   0                   0
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#ENDDATA
/END
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

Comments

The tension behavior can be defined as linear elastic if K > 0 and fct_load = 0.
Loading curve (fct_load > 0) is used both for loading and unloading when unloading curve is not defined (fct_uload = 0).
By default, there is no compression, so function fct_load and fct_uload must be input only for positive strain.
The behavior in compression can be defined with youngs modulus (E), in that case the behavior can only be perfectly plastic, maximum force being defined by Fmax.
Bending and torsion behavior are also defined using Young's modulus, area and area of inertia. The behavior is perfectly plastic.
When the seatbelt element is inside a retractor or a slipring, unloading curve is not used.
Damping is not applied when the element is inside a slipring and retractor.
Minimum length is used only in case of sliprings (/SLIPRING/*) and retractors (/RETRACTOR/*) to prevent stiffness becoming infinite.
It is recommended to use damping for seatbelts. If C = 0, a small amount of critical damping is automatically applied.