/PROP/TYPE8 (SPR_GENE)
Block Format Keyword This spring property works with six independent modes of deformation. This spring accounts for nonlinear stiffness, damping and different unloading.
Deformation, force and energy based failure criteria are available. The general spring property is often used to model a joint connection between two parts.
Format
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

/PROP/TYPE8/prop_ID/unit_ID or /PROP/SPR_GENE/prop_ID/unit_ID  
prop_title  
Mass  I  Skew_ID  sens_ID  I_{sflag}  I_{fail}  I_{fail2}  I_{equil} 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

K_{1}  C_{1}  A_{1}  B_{1}  D_{1}  
fct_ID_{11}  H_{1}  fct_ID_{21}  fct_ID_{31}  fct_ID_{41}  ${\delta}_{\text{min}}^{1}$  ${\delta}_{\text{max}}^{2}$  
F_{1}  E_{1}  Ascale_{1}  Hscale_{1} 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

K_{2}  C_{2}  A_{2}  B_{2}  D_{2}  
fct_ID_{12}  H_{2}  fct_ID_{22}  fct_ID_{32}  fct_ID_{42}  ${\delta}_{\text{min}}^{2}$  ${\delta}_{\text{max}}^{2}$  
F_{2}  E_{2}  Ascale_{2}  Hscale_{2} 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

K_{3}  C_{3}  A_{3}  B_{3}  D_{3}  
fct_ID_{13}  H_{3}  fct_ID_{23}  fct_ID_{33}  fct_ID_{43}  ${\delta}_{\text{min}}^{3}$  ${\delta}_{\text{max}}^{3}$  
F_{3}  E_{3}  Ascale_{3}  Hscale_{3} 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

K_{4}  C_{4}  A_{4}  B_{4}  D_{4}  
fct_ID_{14}  H_{4}  fct_ID_{24}  fct_ID_{34}  fct_ID_{44}  ${\theta}_{\text{min}}^{4}$  ${\theta}_{\text{max}}^{4}$  
F_{4}  E_{4}  Ascale_{4}  Hscale_{4} 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

K_{5}  C_{5}  A_{5}  B_{5}  D_{5}  
fct_ID_{15}  H_{5}  fct_ID_{25}  fct_ID_{35}  fct_ID_{45}  ${\theta}_{\text{min}}^{5}$  ${\theta}_{\text{max}}^{5}$  
F_{5}  E_{5}  Ascale_{5}  Hscale_{5} 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

K_{6}  C_{6}  A_{6}  B_{6}  D_{6}  
fct_ID_{16}  H_{6}  fct_ID_{26}  fct_ID_{36}  fct_ID_{46}  ${\theta}_{\text{min}}^{6}$  ${\theta}_{\text{max}}^{6}$  
F_{6}  E_{6}  Ascale_{6}  Hscale_{6} 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

F_{smooth}  F_{cut} 
Definitions
Field  Contents  SI Unit Example 

prop_ID  Property
identifier. (Integer, maximum 10 digits) 

unit_ID  (Optional) Unit Identifier. (Integer, maximum 10 digits) 

prop_title  Property
title. (Character, maximum 100 characters) 

Mass  Mass. (Real) 
$\left[\text{kg}\right]$ 
I  Inertia. (Real) 
$\left[{\mathrm{m}}^{2}\mathrm{kg}\right]$ 
Skew_ID  Skew system identifier.
1 (Integer) 

sens_ID  Sensor
identifier. (Integer) 

I_{sflag}  Sensor flag. 6
(Integer) 

I_{fail}  Failure criteria.
(Integer) 

I_{fail2}  Failure model flag.
(Integer) 

I_{equil}  Equilibrium flag. 4
(Integer) 

K_{i}  If
fct_ID_{1i} =
0: Linear loading and unloading stiffness. If fct_ID_{1i} ≠ 0: Only used as unloading stiffness for elastoplastic springs. $i$ = 1, 2, 3 are translation DOF. $i$ = 4, 5, 6 are rotation DOF. (Real) 
$\left[\frac{\text{N}}{\text{m}}\right]$
if
$i$
= 1, 2, 3 $\left[\frac{\text{Nm}}{\text{rad}}\right]$ if $i$ = 4, 5, 6 
C_{i}  Damping. 1 $i$ = 1, 2, 3 are translation DOF. $i$ = 4, 5, 6 are rotation DOF. (Real) 
$\left[\frac{\text{Ns}}{\text{m}}\right]$
if
$i$
= 1, 2, 3 $\left[\frac{\text{Nms}}{\text{rad}}\right]$ if $i$ = 4, 5, 6 
A_{i}  Nonlinear stiffness
function scale factor. $i$ = 1, 2, 3 are translation DOF. $i$ = 4, 5, 6 are rotation DOF. Default = 1.0 (Real) 
$\left[\text{N}\right]$
if
$i$
= 1, 2, 3 $\left[\text{Nm}\right]$ if $i$ = 4, 5, 6 
B_{i}  Scale factor for
logarithmic rate effects. $i$ = 1, 2, 3 are translation DOF. $i$ = 4, 5, 6 are rotation DOF. Default = 0.0 (Real) 
$\left[\text{N}\right]$
if
$i$
= 1, 2, 3 $\left[\text{Nm}\right]$ if $i$ = 4, 5, 6 
D_{i}  Scale factor for
logarithmic rate effects. $i$ = 1, 2, 3 are translation DOF. $i$ = 4, 5, 6 are rotation DOF. Default = 1.0 (Real) 
$\left[\frac{\text{m}}{\text{s}}\right]$
if
$i$
= 1, 2, 3 $\left[\frac{\text{rad}}{\text{s}}\right]$ if $i$ = 4, 5, 6 
fct_ID_{1i}  Function identifier
defining nonlinear stiffness
$\mathrm{f}\left(\right)$
. 5
If H_{i}=4: Function defines upper yield curve. $i$ = 1, 2, 3 are translation DOF. $i$ = 4, 5, 6 are rotation DOF. (Integer) 

H_{i}  Spring Hardening flag for
nonlinear spring.
$i$ = 1, 2, 3 are translation DOF. $i$ = 4, 5, 6 are rotation DOF. (Integer) 

fct_ID_{2i}  Function identifier
defining force or moment as a function of spring velocity,
$\mathrm{g}\left(\right)$
. $i$ = 1, 2, 3 are translation DOF. $i$ = 4, 5, 6 are rotation DOF. (Integer) 

fct_ID_{3i}  Function identifier. If H_{i} =4: Defines lower yield curve. If H_{i} =5: Defines residual displacement or rotation versus maximum displacement or rotation. If H_{i} =6: Defines nonlinear unloading curve. If H_{i} =7: Defines nonlinear unloading curve. $i$ = 1, 2, 3 are translation DOF. $i$ = 4, 5, 6 are rotation DOF. (Integer) 

fct_ID_{4i}  Function identifier for
nonlinear damping,
$\mathrm{h}\left(\right)$
. $i$ = 1, 2, 3 are translation DOF. $i$ = 4, 5, 6 are rotation DOF. (Integer) 

${\delta}_{\mathrm{min}}^{i}$  Negative translation
failure limit. $i$ = 1, 2, 3 are translation DOF. Default = 10^{30} (Real) 

If I_{fail2} = 0 or 1: Failure displacement.  $\left[\text{m}\right]$  
If I_{fail2} = 2: Failure force.  $\left[\text{N}\right]$  
If I_{fail2} = 3: Failure internal energy.  $\left[\text{J}\right]$  
${\theta}_{\mathrm{min}}^{i}$  Negative rotational
failure limit. $i$ = 4, 5, 6 are rotation DOF. Default = 10^{30} (Real) 

If I_{fail2} = 0, 1: Failure rotation.  $\left[\text{rad}\right]$  
If I_{fail2} = 2: Failure moment.  $\left[\mathrm{N}\cdot \mathrm{m}\right]$  
If I_{fail2} = 3: Failure internal energy.  $\left[\text{J}\right]$  
${\delta}_{\mathrm{max}}^{i}$  Positive translation
failure limit. $i$ = 1, 2, 3 are translation DOF. Default = 10^{30} (Real) 

If I_{fail2} = 0 or 1: Failure displacement.  $\left[\text{m}\right]$  
If I_{fail2} = 2: Failure force.  $\left[\text{N}\right]$  
If I_{fail2} = 3: Failure internal energy.  $\left[\text{J}\right]$  
${\theta}_{\mathrm{max}}^{i}$  Positive rotational
failure limit. $i$ = 4, 5, 6 are rotation DOF. Default = 10^{30} (Real) 

If I_{fail2} = 0 or 1: Failure rotation.  $\left[\text{rad}\right]$  
If I_{fail2} = 2: Failure moment.  $\left[\mathrm{N}\cdot \mathrm{m}\right]$  
If I_{fail2} = 3: Failure internal energy.  $\left[\text{J}\right]$  
F_{i}  Abscissa scale factor for
the damping functions for the
$g$
and
$h$
. $i$ = 1, 2, 3 are translation DOF. $i$ = 4, 5, 6 are rotation DOF. Default = 1.0 (Real) 
$\left[\frac{\text{m}}{\text{s}}\right]$
if
$i$
= 1, 2, 3 $\left[\frac{\text{rad}}{\text{s}}\right]$ if $i$ = 4, 5, 6 
E_{i}  Ordinate scale factor for
the damping function
$g$
. $i$ = 1, 2, 3 are translation DOF. $i$ = 4, 5, 6 are rotation DOF. (Real) 
$\left[\text{N}\right]$
if
$i$
= 1, 2, 3 $\left[\text{Nm}\right]$ if $i$ = 4, 5, 6 
Ascale_{i}  Abscissa scale factor for
the stiffness function
$f$
. $i$ = 1, 2, 3 are translation DOF. $i$ = 4, 5, 6 are rotation DOF. Default = 1.0 (Real) 
$\left[\text{m}\right]$
if
$i$
= 1, 2, 3 $\left[\text{rad}\right]$ if $i$ = 4, 5, 6 
Hscale_{i}  Ordinate scale factor for
the damping function
$h$
. $i$ = 1, 2, 3 are translation DOF. $i$ = 4, 5, 6 are rotation DOF. Default = 1.0 (Real) 
$\left[\text{N}\right]$
if
$i$
= 1, 2, 3 $\left[\text{Nm}\right]$ if $i$ = 4, 5, 6 
Comments
 The spring local system is defined by a skew coordinate system.The local system can be defined for each element in the spring definition (/SPRING). If a skew is not defined at element level, the /PROP/TYPE8 Skew_ID is used. If a system is not defined in the element or the property then the global system is used. The third node in element definition is not used to determine the local coordinate system of the spring.
 The spring has six
degrees of freedom (DOF) in a skew system:
${\delta}^{1},{\delta}^{2},{\delta}^{3},{\theta}^{4},{\theta}^{5},{\theta}^{6}$
 The six DOF are independent. If the initial spring length is not equal to zero, the force equilibrium is correct but the moment equilibrium may not be correct. Therefore, it is recommended to use spring elements TYPE8 with a zerolength or with one of the two nodes fixed in all directions. For other nonzero length springs, the /PROP/TYPE13 (SPR_BEAM) spring property should be used.
 Positive and negative spring deformations are not defined with the variation of initial length. The initial length can be equal to zero for all or a given direction. Therefore, it is not possible to define the deformation sign with length variation. A deformation is positive if displacement (or rotation) in the spring’s local system of node 2 minus the displacement (or rotation) of node 1 is positive.
 Force and moment
computation.

$\delta $
is a translational DOF, the force in direction
$\delta $
is computed as:
$\mathrm{F}(\delta )=\mathrm{f}\left(\frac{{\delta}^{i}}{Ascal{e}_{i}}\right)\left[{A}_{i}+{B}_{i}\mathrm{ln}\left(\mathrm{max}\left(1,\left\frac{{\dot{\delta}}^{i}}{{D}_{i}}\right\right)\right)+{E}_{i}\mathrm{g}\left(\frac{{\dot{\delta}}^{i}}{{F}_{i}}\right)\right]+{C}_{i}{\dot{\delta}}^{i}+Hscal{e}_{i}\mathrm{h}\left(\frac{{\dot{\delta}}^{i}}{{F}_{i}}\right)$ with $i$ =1,2,3

$\theta $
is a rotational DOF, the moment is computed as:
$\mathrm{M}(\theta )=\mathrm{f}\left(\frac{{\theta}^{i}}{Ascal{e}_{i}}\right)\left[{A}_{i}+{B}_{i}\mathrm{ln}\left(\mathrm{max}\left(1,\left\frac{{\dot{\theta}}^{i}}{{D}_{i}}\right\right)\right)+{E}_{i}\mathrm{g}\left(\frac{{\dot{\theta}}^{i}}{{F}_{i}}\right)\right]+{C}_{i}{\dot{\theta}}^{i}+Hscal{e}_{i}\mathrm{h}\left(\frac{{\dot{\theta}}^{i}}{{F}_{i}}\right)$ with $i$ =4,5,6

$\delta $
is a translational DOF, the force in direction
$\delta $
is computed as:
 Equilibrium:
 If I_{equil} = 0 (no
equilibrium), then:
(1) $$\text{f}\left(\theta \right)={M}_{2y}={M}_{1y}$$Where, ${M}_{2y}$
 Moment in $Y$ by N_{2}.
 ${M}_{1y}$
 Moment in $Y$ by N_{1}.
 If I_{equil} =
1, then:
(2) $${M}_{1y}\ne {M}_{2y}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}{M}_{1z}\ne {M}_{2z}$$(3) $$\text{f}\left(\theta \right)=\frac{{M}_{2y}{M}_{1y}}{2}$$Where, ${M}_{2y}$
 Moment in $Y$ by N_{2}.
 ${M}_{1y}$
 Moment in $Y$ by N_{1}.
 ${M}_{2z}$
 Moment in $Z$ by N_{2}.
 ${M}_{1z}$
 Moment in $Z$ by N_{1}.
 If I_{equil} = 0 (no
equilibrium), then:
 If K_{i} is less than the maximum slope of the yield curve (K_{i} is not consistent with the maximum slope of the yield curve), a warning message is output and K_{i} is set to the maximum slope of the curve.
 Spring is activated and/or deactivated
by the sensor defined in sens_ID and depends on I_{sflag}:
 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.
 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.
 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.