Command Element

Description

Modifies a spring-damper force element.

Format

<Force_SpringDamper

      id               = "integer"

      i_marker_id      = "integer"

      j_marker_id      = "integer"

      stiffness        = "real"

      damping          = "real"

      length           = "real"

      preload          = "real"

/>

Attributes

id

Element identification number (integer > 0).  This number is unique among all Force_SpringDamper elements.

i_marker_id

Modifies the Reference_Marker at which the force or torque is applied.  This is designated as the point of application of the force.

j_marker_id

Modifies the Reference_Marker at which the reaction force or torque is applied.  This is designated as the point of application of the reaction force.

length

Modifies the free-length or the installed (reference) length of the spring.  It has to be strictly positive.  A zero or negative value is not allowed.

stiffness

Modifies the spring stiffness.  For translational spring-dampers, this has units of force/unit translational deflection.  For rotational spring-dampers, this has units of torque/radian.  Note that stiffness > 0.  A negative value is not allowed.

damping

Modifies the damping coefficient.  For translational spring-dampers, this has units of force/unit translational deflection velocity.  For rotational spring-dampers, this has units of torque/unit angular deflection velocity.

Note that damping > 0.  A negative value is not allowed.

preload

Modifies any assembly or pre-load in the spring-damper.  This is the force or torque when the distance or angle between the I and J markers is equal to the value specified by length.

A positive value implies a force that tends to increase the distance or a torque that tends to increase the angle (repulsive), and vice versa.

Example

<Force_SpringDamper

    id        = "105001"

    length    = "334.12"

    stiffness = "138.444"

    damping   = "0."

    preload   = "0."

/>

Command Element

Description

Modifies a SPRINGDAMPER element.

Declaration

def SPRINGDAMPER(ID, LABEL="", I=0, J=0, TYPE="", C=0.0, CT=0.0, K=0.0, KT=0.0, FORCE=0.0, TORQUE=0.0, LENGTH=0.0, ANGLE=0.0):

Attributes

id

Element identification number (integer>0).  This number is unique among all the SPRINGDAMPER elements.

LABEL

Modifies the name of the SPRINGDAMPER element.

I

Modifies the ID of the marker at which the force or torque is applied.  This is designated as the point of application of the force.

J

Modifies the ID of the marker at which the reaction force or torque is applied.  This is designated as the point of reaction of the force.

TYPE

Specifies the type of SPRINGDAMPER.  Select from "TRANSLATIONAL" and "ROTATIONAL".

"TRANSLATIONAL": Implies that the element applies a force between the two markers.  No torque is applied.

"ROTATIONAL": Implies that the element applies a torque between the two markers. No force is applied.

C

Modifies the translational damping coefficient.  This has units of force/unit translational deflection velocity.

CT

Modifies the rotational damping coefficient.  This has units of torque/unit angular deflection velocity.

K

Specifies the translational spring stiffness.  This has units of force/unit translational deflection.

KT

Modifies the rotational spring stiffness. This has units of torque/unit rotational deflection.

FORCE

Modifies the pre-load in the SPRINGDAMPER.

This is the force when the distance between the I and J markers is equal to the value specified by LENGTH.  A positive value implies a force that tends to increase the distance and vice versa.

TORQUE

Modifies pre-load in the SPRINGDAMPER.

This is the torque when the angle between the I and J markers is equal to the value specified by ANGLE.  A positive value implies a torque that tends to increase the angle (repulsive), and vice versa.

LENGTH

Modifies the free length of the spring.

ANGLE

Modifies the free angle of the spring.

Comments

See Force_SpringDamper

Example

The example below shows how a translational SPRINGDAMPER may be modified.

SPRINGDAMPER(105001, C=0, K=138.444, FORCE=0.0, LENGTH=334.12)