/PROP/TYPE32 (SPR_PRE)
Block Format Keyword This property describes the pretension spring property set that can be used to model seat belt pretensioners or apply pretension to a bolt.
Format
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
/PROP/TYPE32/prop_ID/unit_ID or /PROP/SPR_PRE/prop_ID/unit_ID | |||||||||
prop_title | |||||||||
M | sens_ID | Ilock | |||||||
fct_ID1 | fct_ID2 | Ascale_2 | Ascale_1 | Fscale_F |
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) |
|
M | Spring mass. (Real) |
|
sens_ID | Sensor
identifier. (Integer) |
|
Ilock | Lock feature flag.
(Integer) |
|
Spring stiffness before sensor
activation, unloading stiffness after sensor activation, and spring stiffness after
the spring has locked. (Real) |
||
Force at sensor
activation. (Real) |
||
Piston's slide
length. (Real) |
||
Initial internal energy at sensor
activation (Real) |
||
Loading stiffness after sensor
activation. (Real) |
||
fct_ID1 | Pretension loading force function versus
displacement after sensor activation
. (Integer) |
|
fct_ID2 | Pretension loading force function versus
time after sensor activation
. (Integer) |
|
Ascale_2 | Scale factor for abscissa (time) for fct_ID2. (Real) Default = 1.0 |
|
Ascale_1 | Scale factor for abscissa for fct_ID1. (Real) Default = 1.0 |
|
Fscale_F | Scale factor for ordinate (force) for
the functions fct_ID1 and fct_ID2. (Real) Default = 1.0 |
Example (Pretension)
#RADIOSS STARTER
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#- 1. LOCAL_UNIT_SYSTEM:
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/UNIT/2
unit for prop
# MUNIT LUNIT TUNIT
kg m s
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/PROP/SPR_PRE/11/2
PRETENSIONNER
# M sensor_ID Ilock
.05 1 0
# Stif0 F1 D1 E1 Stif1
100000 0 .25 0 0
#funct_ID1 funct_ID2 Ascale_2 Ascale_1 Fscale_F
1 0 0 0 0
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/SENSOR/TIME/1
pretentionner
# Tdelay
0.1
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/FUNCT/1
Loading force function vs displacement after sensor activation
# X Y
-1 0
-.1 95
0 100
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#ENDDATA
Comments
- Pretension elements are /SPRING elements with two nodes. These elements can be used to model seat belt pretensioners or apply pretension to a bolt.
- The pretension element can be visualized as a piston with slide length that moves to create the pretension force.
- The pretension element force
starts after sensor activation and can be defined using a linear or nonlinear force:
- The linear model is defined by entering any two of these parameters; force at
activation (
), piston slide length (
), initial internal energy (
), and loading stiffness (
)
The other two parameters are calculated using:
and
Figure 1. - The nonlinear model is defined by entering curves as a function of displacement, fct_ID1 or as a function of time, fct_ID2. If either function is used, the previous input for
,
and
are ignored. If both functions fct_ID1 and fct_ID2 are defined, the function fct_ID2 acts as a scaling function of fct_ID1. The pretension force is then defined as:
(1) Where,- Time at sensor activation.
- Length at sensor activation with
- The linear model is defined by entering any two of these parameters; force at
activation (
), piston slide length (
), initial internal energy (
), and loading stiffness (
)
- If slide length is defined, then the pretension force is set to zero and spring is locked when the spring shortens in length by the slide length .
- If Ilock = 1, the spring is locked when the spring shortens by the slide length or the pretension force is zero as defined by the force functions fct_ID1 or fct_ID2:
- If
Ilock=2, the spring is locked after any
unloading.Lock examples for force versus displacement, fct_ID1 but also valid for force versus time fct_ID2
-
Figure 2. Ilock= 1, spring locks when force = 0 -
Figure 3. Spring locks when is reached -
Figure 4. Ilock= 2, Spring locks due to unloading
-
- After the spring is locked, the spring stiffness is .
- The pretension spring can become unstable if the length of the spring approaches zero.
- Elongation output, LX, LY, LZ from /TH/SPRING is elongation velocity.
- If used for bolt
pretensioning:
- A duplicate spring with /PROP/SPR_BEAM should be used to model 2 – 6 degrees of freedom of the bolt.
- Use Ilock=1, and define force versus time
function fct_ID2 with a force=0 at the time required for the pretension spring to lock. In Figure 5 the spring is locked at t=5.5.
Figure 5.