/PROP/TYPE26 (SPR_TAB)

Block Format Keyword Defines the tabulated spring property.

Format

(1)	(2)	(3)	(5)	(6)	(7)	(8)	(9)
/PROP/TYPE26/`prop_ID`/`unit_ID` or /PROP/SPR_TAB/`prop_ID`/`unit_ID`
`prop_title`
`M`				`sens_ID`	`I`_sflag	`I`_leng	`Dmin`
`Nfunc`	`Nfund`	`Lscale`	`Kmax`		`Dmax`		`Alpha`

Loading function cards (Nfunc)

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
`fct_ID`₁	`Fscale`		`Strain_rate`

Unloading function cards (Nfund)

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
`fct_ID`₁	`Fscale`		`Strain_rate`

Definition

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)
`M`	Mass. 2 (Real)	$[kg]$
`sens_ID`	Sensor identifier. (Integer)
`I`_sflag	Sensor flag. 3 = 0 Spring element activated when `sens_ID` activates and cannot be deactivated. = 1 Spring element deactivated when `sens_ID` activates and cannot be activated. = 2 Spring elements are activated, or deactivated state matches the sensor state and can switch back and forth. The spring reference length ( $l_{0}$ ) is based the spring length at the activation time. (Integer)
`I`_leng	Input per unit length flag. 2 = 0 Spring properties are input as defined. = 1 Spring properties are a function of the spring length. (Integer)
`Dmin`	Failure displacement in compression. 7 Default = -10²⁰ (Real)	$[m]$
`Nfunc`	Numbers of loading curves. (Integer)
`Nfund`	Numbers of unloading curves. (Integer)
`Lscale`	Scale factor for abscissa of loading and unloading functions depending on flag `I`_leng. 6 Default = 1 (Real)	$[m]$
`Kmax`	Maximum stiffness. (Real)	$[\frac{N}{m}]$
`Dmax`	Failure displacement in tension. 7 Default = 10²⁰ (Real)	$[m]$
`Alpha`	Strain rate filtering factor. Values between 0.0 and 1.0. Default value = 1.0 (no strain filtering) (Real)
`fct_ID`₁	Function identifier defining f( $δ$ ) or f( $ε$ ) depending on flag `I`_leng. (Integer)
`Fscale`	Scale factor for loading and unloading functions. (Real)	$[N]$
`Strain_rate`	Displacement or strain rate depending on `I`_leng which corresponds to a loading or unloading function. (Real)	$[\frac{m}{s}]$

Comments

Let $δ$ = L - $L_{0}$ be the difference between the current length and the initial length $L_{0}$ of the spring element.

If I_leng=1, the spring properties are based on the reference spring length. The input should be entered as:

$M = \frac{m}{l_{0}}$	$K = k * l_{0}$

Each spring will then have the following properties in the model:

$m = M \cdot l_{0}$	$k = \frac{K}{l_{0}}$

Where,

$M$ and $K$: Spring values entered in the spring property fields
$m$ and $k$: 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
Dmin and Dmax: Entered as engineering strain
Strain_rate: Entered as engineering strain rate

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.
Force calculations:
- If I_leng =0, the force is defined as a function of displacement:(1)
  $F = f (δ, \dot{δ})$
- If I_leng =1, the force is defined as a function of strain:(2)
  $F = f (ε, \dot{ε})$
Where,

$ε$

Engineering strain.

$L_{0}$

Reference length of the element, with $- L_{0} < δ < \infty$
Spring forces are calculated using loading and unloading functions for different rates.
- The rate is determined and the maximum loading force as well as the minimum unloading force is determined by interpolation from the input curves.
- The behavior between the loading and unloading curves is linear, using Kmax value as the spring stiffness.
- For both loading and unloading, input curves should be defined in order of strictly increasing strain rate values.
- To describe spring compression behavior, input curves Force(strain) should be strictly positive.
- In traction, spring behavior is linear with stiffness equal to Kmax.
  
  Figure 1.
  
  Figure 2.
Lscale is used only when the I_leng =0 (abscissa unit is length); otherwise the default value = 1.(3)
$F = F s c a l e \cdot f_{1} (\frac{L}{L s c a l e})$

Where, $f_{1}$ is the function of fct_ID₁.
The failure of the spring is triggered by two displacement values, one negative value for compressive loadings Dmin and one positive value for tensile loadings Dmax. Thus, failure occurs when:(4)
$\begin{matrix} δ \leq - |D m i n| & o r & δ \geq |D m a x| \end{matrix}$