Overview
You can idealize the inertial effects from a body using a Point Mass. Applications include applying a force with an acceleration or any other inertial load; or adding inertial mass to a structure, which affects modal and harmonic solutions.
The location of the Point Mass can be anywhere in space and can also be defined in a local coordinate system if one exists. The default location is at the centroid of the geometry. The Point Mass will automatically be rotated into the selected coordinate system if that coordinate system differs from the global coordinate system. You can also input moment of inertia values for each direction.
The Rigid Body Dynamics and Explicit Dynamics Solvers consider moments of inertia in the selected coordinates system, rather than in the global coordinate system.
Application
To define a Point Mass:
Select the Geometry object (or a child object).
You can then add a Point Mass object by:
Selecting the Point Mass option from the Mass group on the Geometry Context tab.
or...
Right-clicking the mouse button and selecting > .
or...
Selecting the desired geometry in the graphics window, right-clicking the mouse, and then selecting > from the context menu.
Specify the Scoping Method property as either , , or . Based on the selection made in this step, select a:
Geometry (faces, edges, or vertices) and click Apply in the Details view for the Geometry property.
or...
Single node and click Apply in the Details view for the Geometry property. In order to select an individual node, you need to first generate a mesh on the model, and then select the Node filter on the Graphics Toolbar.
or...
User-defined node-based named selection from the drop-down list of the Named Selection property.
or...
User-defined remote point from the drop-down list of the Remote Point property.
or...
Specify the Point Mass as a (default) or a using the Applied By property. The option uses either a user-defined or a system-generated as a scoping mechanism. is the required Applied By property setting if the geometry scoping is to a single face or multiple faces, a single edge or multiple edges, or multiple vertices. The option allows you to scope directly to a single vertex (Geometry) or a node (using an individually selected node or a node-based Named Selection) of the model.
Enter a Mass value.
Modify Point Mass object Details properties as needed.
When defined as a Remote Attachment, the Point Mass is considered a remote boundary condition. It can make use of remote points that are either specifically defined or created internally by the application. As a visual check, you can display connection lines between your scoping and remote points by selecting the Remote Point Connections option of the Style group (Display tab).
Support Limitations
A Point Mass cannot:
span multiple bodies if the Stiffness Behavior of the bodies is declared as (see Rigid Bodies section for additional information).
be applied to a vertex scoped to an end release.
Explicit Dynamics solutions do not allow scoping via a Direct Attachment.