Using Loads

Forces

To create a force

  1. On the Command Panel, click on FEA BCs and then Force.
  2. Click on the Create action button.
  3. Specify the ID/Name,Force Entity and Entity ID(s).
  4. Select or Deselect Specify Using Vector and enter the appropriate settings.
  5. Click Apply.

Create Force [id] [Name <'name'>] [ {Add|On} {Nodeset|Surface|Curve|Vertex|Face|Tri|Edge|Node} <entity_list>] [Force Value <val>] [Moment Value <val>] [Direction { direction_options}]

Create Force [id] [Name <'name'>] [ {Add|On} {Nodeset|Surface|Curve|Vertex|Face|Tri|Edge|Node} <entity_list>] [ Vector <val> <val> <val> <val> <val> <val>]

To modify a force

  1. On the Command Panel, click on FEA BCs and then Force.
  2. Click on the Create action button.
  3. Specify the ID/Name,Force Entity and Entity ID(s).
  4. Select or Deselect Specify Using Vector and enter the appropriate settings.
  5. Click Apply.

Modify Force {id_list|'name'|all} [Name <'name'>] [ {Add|Remove} {Nodeset|Surface|Curve|Vertex|Face|Tri|Edge|Node} <entity_list>] [Force Value <val>] [Moment Value <val>] [Direction { direction_options}]

Modify Force {id_list|'name'|all} [Name <'name'>] [ {Add|Remove} {Nodeset|Surface|Curve|Vertex|Face|Tri|Edge|Node} <entity_list>] [ Vector <val> <val> <val> <val> <val> <val>]

A Trelis user has the ability to create forces on 0D, 1D, and 2D entities. A force can be created using the direction syntax (see Specifying Direction). If the vector keyword is used, the first three values are the force components, and the last three values are the moment components.

The use of the force and moment keywords specify the type of load. If both a force and a moment are to be applied, first create one of them, then modify it to add the other. Note that every instance of a force or moment keyword must have an accompanying value keyword.

Regarding force and moment keywords, the following detail may be helpful:

A user may create a force and moment at the same time, but can only specify a direction once. If the force and moment have the same unit vector, it will be successful.  If a users wants to create a force in the direction 1,2,3 and a moment in the direction 1,0,0, the user will have to create one, then add the other by modifying it.

Using Pressure

To create or modify a pressure

  1. On the Command Panel, click on FEA BCs and then Pressure.
  2. Click on the Create or Modify action button.
  3. Specify the ID/Name,Force Entity, Entity ID(s) and Magnitude Value.
  4. Enter any other appropriate settings.
  5. Click Apply.

Create Pressure [id] [Name <'name'>] [{Add|On} {Sideset|Surface|Curve|Face|Tri|Edge} <entity_list>] [Magnitude <value>] [TOP|Bottom] [PRESSURE|Totalforce]

Modify Pressure {id_list|'name'|all} [Name <'name'>] [{Add|Remove} {Sideset|Surface|Curve|Face|Tri|Edge} <entity_list>] [Magnitude <value>] [TOP|Bottom] [PRESSURE|Totalforce]

Trelis users can create pressure boundary conditions on 1D and 2D entities. Positive surface pressures acting on solid elements are defined as pointing into the face of the elements. Pressures are always normal to the face. For shells and independent surfaces, a ‘left-hand-rule’ is employed. Point your left thumb at the surface in question. If the direction your fingers curl matches the direction of ascending vertex numbering, the direction of the pressure vectors will match the direction of your thumb.

Value

The value variable is the magnitude of the pressure boundary condition. If the user leaves this value blank, Trelis will assign the pressure magnitude to zero (possibly a trivial case) and issue a warning. Typing a negative value will not flip the direction of the pressure arrows on the display; instead, the pressure magnitude will be negative.

Pressure and Total Force

The pressure and totalforce keywords are used to modify the pressure boundary condition. The pressure keyword is the default. All pressures applied with this keyword present (or with both of these keywords absent from the command string) are pure pressures. If the user enters the totalforce keyword, the pressure magnitude is divided by the area of the surface the pressure is acting on (or the length of the curve, for a curve pressure). In effect, the user is entering a force that is treated and exported as a pressure.

Top and Bottom

The top keyword (default) indicates the pressure will occur on the top of a shell element. Specifying bottom will cause the pressure to be applied to the bottom of the element.

Using Heat Flux

To create or modify a heatflux

  1. On the Command Panel, click on FEA BCs and then Heatflux.
  2. Click on the Create or Modify action button.
  3. Specify ID/Name, Entity List and Entity ID(s).
  4. Enter any other appropriate settings.
  5. Click Apply.

Create Heatflux [id] [Name <'name'>] [{Add|On} {Sideset|Surface|Curve|Face|Tri|Edge} <entity_list>] [Value <value>]

Create Heatflux [id] [Name <'name'>] [{Add|On} {Sideset|Surface|Face|Tri} <entity_list>] [Top <value> Bottom <value>]

Modify Heatflux {id_list|'name'|All} [Name <'name'>] [{Add|Remove} {Sideset|Surface|Curve|Face|Tri|Edge} <entity_list>] [Value <value>]

Modify Heatflux {id_list|'name'|All} [Name <'name'>] [{Add|Remove} {Sideset|Surface|Face|Tri} <entity_list>] [Top <value> Bottom <value>]

A Trelis user may apply heat flux boundary conditions to 1D and 2D entities, including thin-shell elements.

Top and Bottom Values

Heat fluxes can be applied to thin-shell elements as well. The same rules apply to thin-shell heat fluxes as to thin-shell temperatures: thin-shell heat fluxes can only be applied to surfaces and heat flux boundary conditions cannot contain regular and thin-shell heat flux values (see journal below). However, thin-shell heat flux commands do not contain gradient or middle keyword options. Only top and bottom keywords are supported.

Using Convection

To create or modify a convection

  1. On the Command Panel, click on FEA BCs and then Convection.
  2. Click on the Create or Modify action button.
  3. Specify ID/Name, Entity List and Entity ID(s).
  4. Enter any other appropriate settings.
  5. Click Apply.

Create Convection [id] [Name <'name'>] [{Add|On} {Sideset|Surface|Curve|Face|Tri|Edge} <entity_list>] [Surrounding {<value>| Top <value> Bottom <value>} Coefficient {<value>| Top <value> Bottom <value>}]

Modify Convection [id] [Name <'name'>] [{Add|On} {Sideset|Surface|Curve|Face|Tri|Edge} <entity_list>] [Surrounding {<value>| Top <value> Bottom <value>} Coefficient {<value>| Top <value> Bottom <value>}]

A Trelis user can apply convection boundary conditions to 1D and 2D entities. Convection is a transport of thermal energy that is proportional to the difference between the surface temperature and the temperature of the surroundings.

Surrounding

The surrounding keyword specifies the temperature surrounding the entity with the convection boundary condition.

Coefficient

The coefficient keyword is a convection coefficient, in units of energy per length times time times temperature (i.e., [energy]/([length]*[time]*[temperature]) ).