![](../icons_C2/common/areference.gif) |
Distributed Forces
are
force systems statically equivalent to a given pure force resultant at
a given point, distributed on a virtual part or on a geometric selection.
Distributed Force objects belong to Loads objects sets. The user specifies three
components for the direction of the resultant force, along with a magnitude information. Upon modification of any of these four
values, the resultant force vector components and magnitude are updated
based on the last data entry. The resultant force vector remains constant
independently of the geometry selection.
The point of application of the force resultant is
automatically defined as follows:
![](_themes/v5r5/ul1.gif) | For extended geometries, this point is the centroid of the
geometry. |
![](_themes/v5r5/ul1.gif) | For virtual parts, this point is the handler of
the virtual part. |
The given single-force system is processed by the program as
follows:
![](_themes/v5r5/ul1.gif) | In the case of extended geometries, it is transformed into an
equivalent force system distributed over the selected support. |
![](_themes/v5r5/ul1.gif) | In the case of virtual parts connected to deformable bodies, it is
transmitted as a force system collectively to the entire connected geometry. |
Units are force units (typically N
in SI).
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Distributed Forces can be applied to the following types of Supports:
![](../icons_C2/common/iconblck.gif)
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This task shows you how to
create a Distributed Force applied to a virtual part or to a geometry
selection.
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You can use the sample00.CATAnalysis
document from the samples directory
for this task:
Finite Element Model containing a Static Analysis Case and computed corresponding Static
Solution.
Before You Begin:
Go to View -> Render Style -> Customize View and make
sure the Shading, Outlines and Materials options are active in the Custom View Modes
dialog box.
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1. Click the Distributed Force
icon
.
The Distributed Force dialog box is displayed.
![](images/aaaPanelLoadDistribForce.gif)
2. If needed, change the identifier of the Distributed Force by editing
the Name field.
3. Set the Axis System Type.
The Axis System Type combo box allows you to
choose between Global and User Axis systems, for entering
components of the resultant force vector.
![](_themes/v5r5/ul1.gif) | Global: if you select the Global Axis system, the components of the
resultant force vector will be interpreted as relative to the fixed
global rectangular coordinate system. |
![](_themes/v5r5/ul1.gif) | User: if you select a User Axis system, the
components of the resultant force vector will be interpreted as
relative to the specified rectangular coordinate system. |
To select a User Axis system, you must activate an existing
Axis by clicking it in the specification tree. Its name will then be
automatically displayed in the Current Axis field.
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![ainfo.gif (980 bytes)](../icons_C2/common/ainfo.gif) |
![](_themes/v5r5/ul1.gif) | You can define the resultant force
vector direction by using the compass. |
![](_themes/v5r5/ul1.gif) | You can modify the compass
orientation either with the mouse or by editing the compass. |
![](_themes/v5r5/ul1.gif) | By applying the compass to any
part geometry, you can align the compass directions with the implicit axis
directions of that geometry: drag the compass by handling the red square
and drop it on the appropriate surface. The normal direction to this
surface defines the new direction. Then, click on the Compass Direction
button to take this new direction into account. You can now invert the
direction if desired, editing the values of the three components. |
4. Enter values for the X, Y, Z
components of the resultant force vector. For example, enter -50N
as Z value.
The remaining three
fields are automatically computed and displayed.
The visualized symbols orientation will also reflect the modification,
once the support will be selected.
5. Select the support (a
virtual part or a geometry) on which the resultant force vector is
applied at the pre-defined point. Any selectable geometry is
highlighted when you pass the cursor over it.
You can select several supports in
sequence, to apply the Distributed Force to all supports
simultaneously.
A symbol representing the resultant force equivalent to the Distributed Force is displayed
at the application point of the support to visualize the input force
system.
The Distributed Force dialog box now appears as shown here:
6. Click OK in the Distributed Force dialog box to
create the Distributed Force.
A Distributed Force object appears in the specification tree under the active Loads objects set.
![](images/6treeloadforcedistr.gif)
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![](_themes/v5r5/ul1.gif) | Make sure the computation is finished before
starting any of the following operations. |
![](_themes/v5r5/ul1.gif) |
Be aware that the
Distributed Force, as the Distributed Moment, applies directly to the
nodes of the selected entity, whereas a Surface Density Force, or a
Pressure, applies to the element faces of the selected entity. The
latter type of forces is far more accurate and should be used whenever
equivalent to the Distributed Force. |
As an example, consider a
coarsely meshed cylinder whose top surface has been submitted to a
Distributed Force and whose bottom surface is clamped. As the nodes on
the edges have less neighbors that inner nodes, they are pulled a
lot further than the inner nodes, thus leading to an erroneous result
near the edges. Mesh refinement is needed to get proper results. On the
contrary, the Surface Density Force leads to a smoother and more
accurate displacement.
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Open DistribForce.CATAnalysis
in this particular case.
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Applying a Distributed
Force results as shown here:
![](images/aImageDistributedForce01.gif)
Applying
a Surface Density Force results as shown here:
![](images/aImageDistributedForce02.gif)
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![../../../ICONS/icons.doc/src/common/ainfo.gif (980 bytes)](../icons_C2/common/amethod.gif)
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![](_themes/v5r5/ul1.gif) | You can either select the
support and then set the Distributed Force specifications, or set the
Distributed Force specifications and then select the
support. |
![](_themes/v5r5/ul1.gif) | If you select several geometric
supports, you can create as many Distributed Forces as desired with the
same dialog box. A series of Distributed Forces can therefore be created
quickly. The point of application is automatically assumed to be the
centroid of the system of individual supports centroids. |
![](_themes/v5r5/ul1.gif) | Loads are required for Stress
Analysis computations. |
![](_themes/v5r5/ul1.gif) | If several Analysis Cases have been defined in
the Finite Element Model, you must activate a Loads objects set in the features
tree before creating a Distributed Force object. |
![](_themes/v5r5/ul1.gif) | Distributed Force objects can be edited by a double click on the
corresponding object or icon in the features tree. |
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![../../../ICONS/icons.doc/src/common/ainfo.gif (980 bytes)](../icons_C2/common/tips.gif)
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Products
Available in
Analysis Workbench
The ELFINI Structural Analysis
product offers the following additional features with a right mouse click
(key 3):
![](_themes/v5r5/ul1.gif) |
on a Body Force object:
Distributed Force Visualization on Mesh: the translation of your Distributed Force
object specifications into solver specifications can be visualized
symbolically at the impacted mesh nodes, provided the mesh has been
previously generated via a Compute action.
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![](_themes/v5r5/ul1.gif) |
on a Loads objects set:
1) Generate Image: generates an image of the computed Load objects
(along with translating all user-defined Loads specs into explicit solver commands
on mesh entities), by
generating symbols for the elementary loads imposed by the Loads
objects set. The image can be edited to include part or all of the
options available.
2) Report: the partial status and results of intermediate
pre-processor computations are
reported in HTML format. It represents a subset of the
global Report capability and generates a partial report of the Loads
objects set Computation.
See Creating Pressures for more details.
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3) Double-clicking on the Loads set, you will display the
Loads dialog box that lets you choose whether you wish to apply
self-balancing to the load. Example of use: if this option is used with
iso-static specifications, it will allow you to simulate free-body
loading. If you make the option active, the center of inertia results
null.
![](images/aaPanelSelfBalancing.gif)
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