Creating Moments

This task shows you how to create a Moment applied to a virtual part or to a geometry selection.

Moments are force systems statically equivalent to a given pure couple (single moment resultant), distributed on a virtual part or on a geometric selection. 
Moment objects belong to Loads sets.

The user specifies three components for the direction of the resultant moment, along with a magnitude information. Upon modification of any of these four values, the resultant moment vector components and magnitude are updated based on the last data entry. The resultant moment vector remains constant independently of the geometry selection. 

The given pure couple system is processed by the program as follows:

• In the case of extended geometries, it is transformed into an equivalent force system distributed over the selected support.

• In the case of virtual parts connected to deformable bodies, it is transmitted as a force system collectively to the entire connected geometry.

The point of application of the couple is arbitrary.

Units are moment units (typically Nm in SI).

Moments can be applied to the following types of supports:

To know more, refer to Authorized Supports.

Open the sample00.CATAnalysis document from the samples directory.

• 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.

1. Click Moment in the Loads toolbar.

   The Moment dialog box appears.

2. You can change the identifier of the Moment by editing the Name field.

3. Set the Axis system.

   The Axis System Type combo box allows you to choose between Global and User Axis systems, for entering components of the resultant moment vector. Global: if you select the Global Axis system, the components of the resultant moment vector will be interpreted as relative to the fixed global rectangular coordinate system.    User:  if you select a User-defined Axis system, the components of the resultant moment 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.

   You can define the resultant moment vector direction by using the compass.  You can modify the compass orientation either with the mouse or by editing the compass.   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. Select the support (a virtual part or a geometry) on which the resultant moment vector is applied.

   Any selectable geometry is highlighted when you pass the cursor over it. You can select several supports in sequence, to apply the Moment to all supports simultaneously. A symbol representing the resultant moment equivalent to the Moment is displayed at the application point of the support to visualize the input force system. As soon as the support is selected, the Select Mesh Part button is available. To know more about the Select Mesh Part button, refer to Selecting Mesh Parts.

5. Enter values for the X, Y, Z components of the resultant moment vector: the corresponding Norm value is automatically computed and displayed.

   The visualized symbols orientation is also updated to reflect the modification.

6. Click OK in the Moment dialog box. 

   A Moment object appears in the specification tree under the active Loads objects set.

• You can either select the support and then set the Moment specifications, or set the Moment specifications and then select the support.
• If you select several geometric supports, you can create as many Moment loads as desired with the same dialog box. A series of Moments can therefore be created quickly.
• Loads are required for Stress Analysis computations. 
• If several Analysis Cases have been defined in the Finite Element Model, you must activate a Loads objects set in the specification tree before creating a Moment object (only available if you have ELFINI Structural Analysis product installed).
• Moment objects can be edited by a double click on the corresponding object or icon in the specification tree.

The ELFINI Structural Analysis product offers the following additional functionalities:

• Contextual menu on the load object:
  • Moment 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 using a mesh only computation.
    To know more, refer to Visualizing Loads on Mesh.
• Contextual menus on the Loads set:
  • Generate Image: generates an image of the computed loads (along with translating all user-defined load specifications into explicit solver commands on mesh entities), by generating symbols for the elementary loads imposed by the loads sets. The image can be edited to include part or all of the options available.
    To know more, refer to Generating Images.
  • 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 set computation.
    To know more, refer to Generating Reports.
• Self-balancing: you can double-click the Loads set to automatically add inertia forces in order to counter balance external loads.
  Double-click the Loads set to 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.
  To know more, refer to Creating Pressures.