/PROP/TYPE4 (SPRING)
Block Format Keyword Defines spring property with one translational DOF. This spring accounts for nonlinear stiffness, damping and different unloading. Deformation based failure criteria is available.
Format
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

/PROP/TYPE4/prop_ID/unit_ID or /PROP/SPRING/prop_ID/unit_ID  
prop_title  
Mass  sens_ID  I_{sflag}  I_{leng}  
K_{1}  C_{1}  A_{1}  B_{1}  D_{1}  
fct_ID_{11}  H_{1}  fct_ID_{21}  fct_ID_{31}  fct_ID_{41}  ${\delta}_{\mathrm{min}}^{1}$  ${\delta}_{\mathrm{max}}^{1}$  
F_{1}  E_{1}  Ascale_{1}  Hscale_{1} 
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) 

Mass  Mass.
(Real) 
$\left[\frac{\text{kg}}{\text{m}}\right]$ 
sens_ID  Sensor identifier used for
spring activation or deactivation.
(Integer) 

I_{sflag}  Sensor flag. 2
(Integer) 

I_{leng}  Input per unit length flag.
(Integer) 

K_{1}  If
$fct\_I{D}_{11}=0$
: Linear loading and unloading
stiffness. If $fct\_I{D}_{11}\ne 0$ : Only used as unloading stiffness for elastoplastic springs. (Real) 
$\left[\frac{\text{N}}{\text{m}}\right]$ 
C_{1}  Damping. (Real) 
$\left[\frac{\text{Ns}}{\text{m}}\right]$ 
A_{1}  Nonlinear stiffness
function scale factor. Default = 1.0 (Real) 
$\left[\text{N}\right]$ 
B_{1}  Logarithmic rate effects
scale factor. (Real) 
$\left[\text{N}\right]$ 
D_{1}  Logarithmic rate effects
scale factor. Default = 1.0 (Real) 
$\left[\frac{\text{m}}{\text{s}}\right]$ 
fct_ID_{11}  Function identifier
defining
$\mathrm{f}\left(\delta \right)$
. 4
If H_{1} =4: Function defines upper yield curve. If H_{1} =8: Function is mandatory and defines the force vs spring length. (Integer) 

H_{1}  Spring Hardening flag for
nonlinear spring.
(Integer) 

fct_ID_{21}  Function identifier
defining force as a function of spring velocity,
$\mathrm{g}\left(\dot{\delta}\right)$
. (Integer) 

fct_ID_{31}  Function identifier. If H_{1} =4: Defines lower yield curve If H_{1} =5: Defines residual displacement vs maximum displacement If H_{1} =6: Defines nonlinear unloading curve If H_{1} =7: Defines nonlinear unloading curve (Integer) 

fct_ID_{41}  Function identifier for
nonlinear damping
$\mathrm{h}\left(\dot{\delta}\right)$
. (Integer) 

${\delta}_{\mathrm{min}}^{1}$  Negative failure
displacement. Default = 10^{30} (Real) 
$\left[\text{m}\right]$ 
${\delta}_{\mathrm{max}}^{1}$  Positive failure
displacement. Default = 10^{30} (Real) 
$\left[\text{m}\right]$ 
F_{1}  Abscissa scale factor for
damping functions for
$\mathrm{g}$
and
$\mathrm{h}$
. Default = 1.0 (Real) 
$\left[\frac{\text{m}}{\text{s}}\right]$ 
E_{1}  Ordinate scale factor for
the damping function
$\mathrm{g}$
. (Real) 
$\left[\text{N}\right]$ 
Ascale_{1}  Abscissa scale factor for
the stiffness function
$\mathrm{f}$
. Default = 1.0 (Real) 
$\left[\text{m}\right]$ 
Hscale_{1}  Ordinate scale factor for
the damping function
$\mathrm{h}$
. Default = 1.0 (Real) 
Example (Seatbelt)
#RADIOSS STARTER
#12345678910
/UNIT/2
unit for prop
kg mm ms
#12345678910
/PROP/SPRING/2/2
Seatbelt
# M sensor_ID Isflag Ileng
5E5 0 0 1
# K1 C1 A1 B1 D1
0.001 0 0 0 0
# fct_ID11 H1 fct_ID21 fct_ID31 fct_ID41 delta_min delta_max
1 2 0 0 0 0
# F1 E1 Ascale1 Hscale1
0 0 0 0
/MOVE_FUNCT/1
Seatbelt
# Ascale_x Fscale_y Ashift_x Fshift_y
0.001
#12345678910
/FUNCT/1
Seatbelt loading force vs engineering strain
# X Y
0. 0.
0.005 700.
0.02 3100.
0.03 5500.
0.15 17000.
1000. 17000.
#12345678910
#ENDDATA
Comments
 The spring has one translational degree of freedom in the local x direction which is defined between node N1 and N2 of the spring.
 Spring is activated
and/or deactivated by sensor defined in sens_ID and depends on I_{sflag}:
 If I_{sflag} = 0, the spring element is activated by the sens_ID and cannot be deactivated. The initial length of the spring is based on the spring length at time=0.
 If I_{sflag} = 1, the spring element is deactivated by the sens_ID and cannot be activated. The initial length of the spring is based on the spring length at time=0.
 If I_{sflag} = 2, the spring is activated and/or deactivated by sens_ID and can switch activation state multiple times. If sensor is activated, the spring is active; if sensor is deactivated, spring is deactivated. The spring initial length, ${l}_{0}$ , is the distance between spring nodes at the time of sensor activation.
 If I_{leng} = 1, the
spring properties are based on the initial spring length. The input should be
entered as:
$M=\frac{m}{{l}_{0}}$ $K=k*{l}_{0}$ $C=c*{l}_{0}$ Each spring will then have the following properties in the model:Where,$m=M\cdot {l}_{0}$ $k=\frac{K}{{l}_{0}}$ $c=\frac{C}{{l}_{0}}$  $M$ , $K$ and $C$
 Spring values entered in the spring property fields
 $m$ , $k$ and $c$
 Spring’s actual physical mass, stiffness and damping
 ${l}_{0}$
 Initial spring length which is the distance between node N1 and N2 of the spring
 ${\delta}_{\mathrm{min}}^{1}\text{and}{\delta}_{\mathrm{max}}^{1}$
 Failure values entered as engineering strain
 Force computation. For
additional information, refer to Stiffness Formulation in
the User Guide.
 If I_{leng} =0, the value of
force
$F$
in the spring is computed as:For H_{1} = 1,2,4,5,6,7:
(1) $$F=\mathrm{f}\left(\frac{\delta}{Ascal{e}_{1}}\right)\left[{A}_{1}+{B}_{1}\mathrm{ln}\left(\mathrm{max}\left(1,\left\frac{\dot{\delta}}{{D}_{1}}\right\right)\right)+{E}_{1}\mathrm{g}\left(\frac{\dot{\delta}}{{F}_{1}}\right)\right]+{C}_{1}\dot{\delta}+Hscal{e}_{1}\mathrm{h}\left(\frac{\dot{\delta}}{{F}_{1}}\right)$$
Where, $\delta =l{l}_{0}$ is the difference between the current length and the initial length of the spring element.
with ${l}_{0}<\delta <+\infty $
If H_{1} = 8:(2) $$F=\mathrm{f}\left(\frac{l}{Ascal{e}_{1}}\right)\left[{A}_{1}+{B}_{1}\mathrm{ln}\left(\mathrm{max}\left(1,\left\frac{\dot{\delta}}{{D}_{1}}\right\right)\right)+{E}_{1}\mathrm{g}\left(\frac{\dot{\delta}}{{F}_{1}}\right)\right]+{C}_{1}\dot{\delta}+Hscal{e}_{1}\mathrm{h}\left(\frac{\dot{\delta}}{{F}_{1}}\right)$$Where, $\text{0}<l<\infty $ and ${l}_{0}<\delta <+\infty $
If I_{leng} = 1, the value of force $F$ in the spring is computed as:(3) $$F=\mathrm{f}\left(\frac{\epsilon}{Ascal{e}_{1}}\right)\left[{A}_{1}+{B}_{1}\mathrm{ln}\left(\mathrm{max}\left(1,\left\frac{\dot{\epsilon}}{{D}_{1}}\right\right)\right)+{E}_{1}\mathrm{g}\left(\frac{\dot{\epsilon}}{{F}_{1}}\right)\right]+{C}_{1}\dot{\epsilon}+Hscal{e}_{1}\mathrm{h}\left(\frac{\dot{\epsilon}}{{F}_{1}}\right)$$Where, $\epsilon $
 Engineering strain
 $\mathrm{f}\left(\epsilon \right)$
 Nonlinear stiffness is a function of engineering strain
 $\mathrm{g}\left(\dot{\epsilon}\right)\text{and}h\left(\dot{\epsilon}\right)$
 Damping is a function of engineering strain rate
 If I_{leng} =0, the value of
force
$F$
in the spring is computed as:
 If H_{1} > 0 and fct_ID_{11} = s 0, $\mathrm{f}\left(\delta \right)=1\text{or}\mathrm{f}\left(\epsilon \right)=1$ .