Force: Frequency Dependent

Description

It can be used to model a frequency dependent force or a torque. The frequency dependent force or torque are defined with respect to another Reference_Marker. The components must be defined using a user defined subroutine. They may be a function of any system state and time.

Format

<Force_FreqDependent
       id                         = "integer"
     [ label                      = "string" ] 
       i_marker_id                = "integer"
       j_marker_id                = "integer"   
       ref_marker_id              = "integer"
       preload_expr               = "motionsolve_expression"
       dof                        = "real"  
       {
            usrsub_dll_name       = "valid_path_name"
            usrsub_param_string   = "USER( [[par_1 [, ...][,par_n]] )"
            usrsub_fnc_name       = "custom_fnc_name" >
          | script_name           = valid_path_name             
            interpreter           = "string"  
            usrsub_param_string   = "USER( [[par_1 [, ...][,par_n]] )"
            usrsub_fnc_name       = "custom_fnc_name"     
       }               
/>

Attributes

id: Element identification number (integer>0). This number is unique among all Force_FreqDependent elements.
label: The name of the Force_FreqDependent element.
i_marker_id: Specifies the Reference_Marker at which the force is applied. This is designated as the point of application of the force.
j_marker_id: Specifies the Reference_Marker at which an equal and opposite reaction force is applied.
ref_marker_id: Specifies the Reference_Marker whose coordinate system is used as the basis for defining the components of the force.
dof: Specifies the degrees of freedom in which Force_FreqDependent is defined from 1 to 6, representing the translation x,y,z and the rotation z,y,z.
preload_expr: Specifies the time domain preload as a function expression. This preload from the previous static or transient analysis is used in FFOSUB in a frequency response analysis.
usrsub_param_string: The list of parameters that are passed from the data file to the user defined subroutine. Use this keyword only when type = USERSUB is selected.
usrsub_dll_name: Specifies the path and name of the DLL or shared library containing the user subroutine. MotionSolve uses this information to load the user subroutine in the DLL at run time.
usrsub_fnc_name: Specifies an alternative name for the user subroutine FFOSUB.
script_name: Specifies the path and name of the user written script that contains the routine specified by usrsub_fnc_name.
interpreter: Specifies the interpreted language that the user script is written in (example: "PYTHON"). See User-Written Subroutines for a choice of valid interpreted languages.

Example

The following example shows the use of a Force_FreqDependent element to model a force in the X direction along Reference_Marker 1, using the subroutine ffosub.py with a preload expression from a previous time domain simulation.

<Force_FreqDependent
     id                   = "18"
     dof                  = "1"
     i_marker_id          = "1801"
     j_marker_id          = "1802"
     ref_marker_id        = "1"
     usrsub_param_string  = "USER()"
     interpreter          = "Python"
     script_name          = "ffosub.py"
     usrsub_fnc_name      = "FFOSUB"
     preload_expr         = "DZ(30101011,30102020,30101010)"
/>

Comments

i_marker_id is designated as the point of application of the Force_FreqDependent.
preload_expr can be any time domain expression, depending on the usage in FFOSUB
Force_FreqDependent can act on all types of bodies: Body_Rigid, Body_Flexible, and Body_Point.