Model Element

Description

Force_MultiPoint defines a force and torque acting between many Reference_Markers. The force and the torque can only be linear functions of the relative displacement and velocity of the various Reference_Markers.

Format

< Force_MultiPoint

    id                = "integer"

    ref_marker_id     = "integer"

    kmtx_id           = "integer"

 [{ cmtx_id           = "integer"

|   cratio            = "real"

 }]

  [ preload_mtx_id    = "integer" ]

  [ length_mtx_id     = "integer" ]

    n_i_marker        = "integer"  >

integer1   integer1   … integerN  

</Force_MultiPoint >

Attributes

id

Element identification number (integer>0).  This number is unique among all Force_MultiPoint elements and uniquely identifies the element.

ref_marker_id

Specifies the Reference_Marker which serves as the reference frame in which relative velocities are computed.  The components of the relative displacement, relative velocity and force vectors are resolved in the coordinate system specified by ref_marker_id.

kmtx_id

Specifies the Reference_Matrix element which contains the stiffness matrix. This is a 6N*6N matrix, where N is the number ofI Reference_Markers.

This is a required parameter.

cmtx_id

Specifies the Reference_Matrix element which contains the damping matrix.  This is a 6N*6N matrix, where N is the number of I Reference_Markers.

This parameter is optional. Default is a zero matrix.

cratio

Defines a damping scale factor.  If this is specified, the damping matrix is calculated as C = cratio * K.

This parameter is optional. Default is zero.

preload_mtx_id

Specifies the 6N*1 Reference_Matrix element which contains the preload values for each pair of markers between which the Force_MultiPoint is applied. N is the number of I Reference_Markers.

This parameter is optional. Default is a zero matrix.

length_mtx_id

Specifies the 3N*1 Reference_Matrix element which contains the reference length values for each pair of markers between which the Force_MultiPoint is applied. N is the number of I Reference_Markers.

This parameter is optional. When omitted, the I Reference_Markers are taken to be at their reference locations.

n_i_marker

Specifies the number of I Reference_Marker elements between which the Force_MultiPoint is applied.  If there are N such markers, then N integers specifying their IDs must follow.

Comments

Example

The following is an implementation of a Force_MultiPoint element between three markers with ids 101 through 103.  The reference marker has an id of 10.  The stiffness matrix is specified using the Reference_Matrix with id 11. The damping ratio is specified as 0.05. The preload and length matrices are not specified.  

<Force_MultiPoint

    id                  = "1"

    ref_marker_id       = "10"

    kmtx_id             = "11"

    cratio              = "0.05"

    n_i_marker          = "3">

    101 102 103

</Force_MultiPoint>

Model Element

Description

NFORCE defines a force and torque acting between many markers.  The force and the torque can only be linear functions of the relative displacement and velocity of the various markers.

Declaration

def NFORCE(id, LABEL="", J=0, IMARKERS=[], KMATRIX=0, CRATIO=0.0, CMATRIX=0, FORCE=0, LENGTH=0):

Attributes

id

Element identification number (integer>0).  This number is unique among all NFORCE elements and uniquely identifies the element.

LABEL

This attribute describes the name of the NFORCE element.

J

Specifies the ID of marker which serves as the reference frame in which the relative displacement, relative velocity and force vectors are resolved in the coordinate system specified by J.

IMARKERS

Specifies the list of IMARKERS between which the NFORCE is applied.

KMATRIX

Specifies the MATRIX element which contains the stiffness matrix.  This is an 6N*6N matrix, where N is the number of I markers.

This is a required parameter.

CRATIO

Defines a damping scale factor.  If this is specified, the damping matrix is calculated as C = cratio * K.

This parameter is optional.

Default is zero.

CMATRIX

Specifies the MATRIX element which contains the damping matrix. This is a 6N*6N matrix, where N is the number of I markers.

This parameter is optional.

Default is a zero matrix.

FORCE

Specifies the 6N*1 MATRIX element which contains the preload values for each pair of markers between which the NFORCE is applied.  N is the number of IMARKERS.

This parameter is optional.

Default is a zero matrix.

LENGTH

Specifies the 3N*1 MATRIX element which contains the length values for each pair of markers between which the NFORCE is applied.  N is the number of IMARKERS.

This parameter is optional. When omitted, the IMARKERS are taken to be at their reference locations.

Comments

See Force_MultiPoint

Example

The example below shows how an NFORCE element may be defined.

NFORCE(1,LABEL="NFORCE_name", J=10,IMARKERS=[101,102,103], KMATRIX=11, CRATIO=0.05)