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Modeling Entities

SimOffice provides for either importing modeling entities from a CAD system or creating them directly. SimOffice uses the exact definition of the originating geometry for most CAD systems such as AutoDesk and Unigraphics parasolid. Geometry accuracy is important, but often times, importing a CAD Model into SimOffice brings in too much detail. Sometimes it is important to idealize the engineering model especially when much of the CAD detail does not apply to the analysis and only adds complexity. In this case, it is best to create your own geometry or edit the CAD geometry. SimOffice provides for many geometry construction and editing features. The modeling entities available for use in SimOffice are as follows:

•	Coordinate frames

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Points

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Curves

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Surfaces

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Solids

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Nodes

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Elements

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MPCs

Coordinate Frame Definitions

SimOffice can create and support three types of coordinate frames:

•	Rectangular (X,Y,Z)

•	Cylindrical (R, Theta, Z)

•	Spherical (R, Theta, Phi)

SimOffice also has a default global rectangular coordinate frame, Coord 0. Coord 0 is the default reference coordinate frame for many application forms (which can be changed to another coordinate frame). Also, Coord 0 cannot be deleted.

Each coordinate system defined in SimOffice has three principal axes. These axes define how spatial locations are determined in that coordinate system, and are internally numbered 1, 2 and 3. The meaning of each principal axis depends on the type of coordinate frame (rectangular, cylindrical or spherical).

When a coordinate frame is created, its principal axes and its orientation are displayed at the appropriate location on the model. The ID of the coordinate frame is also displayed at the coordinate frame’s origin.

Important:

Coordinate frame angles for the cylindrical and spherical coordinate frames (that is, and ) are expressed in degrees.

Rectangular Coordinate Frame

Figure 0‑1 shows the principal axes of a rectangular coordinate frame and a point, P, in rectangular space. In a rectangular frame, the principal axes 1, 2 and 3 correspond to the X, Y and Z axes, respectively. Points in space specified in a rectangular coordinate frame are entered in the order: x-coordinate, y-coordinate and z-coordinate.

Rectangular Coordinate Frame

Cylindrical Coordinate Frame

Figure 0‑2 shows a cylindrical frame in which the principal axes 1, 2 and 3 correspond to the R, T () and Z axes, respectively. Points specified in a cylindrical coordinate frame are entered in the order: radial-coordinate, theta-coordinate and z-coordinate.

Cylindrical Coordinate Frame

Spherical Coordinate Frame

Figure 0‑3 shows a spherical frame in which the principal axes 1, 2 and 3 correspond to the R, T () and P () axes, respectively. Points specified in a spherical coordinate frame are entered in the order: radial-coordinate, theta-coordinate, and phi-coordinate.

Spherical Coordinate Frame Definition

A node’s local directions (1, 2, 3) can vary according to its position within the spherical coordinate frame. For example:

If node lies along R direction, then dir 1 of node is along +R

If node lies along R direction, then dir 2 of node is along -P

If node lies along R direction, then dir 3 of node is along +T

If node lies along T direction, then dir 1 of node is along +T

If node lies along T direction, then dir 2 of node is along -P

If node lies along T direction, then dir 3 of node is along -R

If node lies along P direction, then dir 1 of node is along +P

If node lies along P direction, then dir 2 of node is along +T

If node lies along P direction, then dir 3 of node is along -R

Creating Coordinate Systems

There are two ways you can create a local rectangular, cylindrical or spherical coordinate frame in SimOffice.

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3Point

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Normal

3 Point Method

This method creates a new rectangular, cylindrical, or spherical coordinate system using 3 points as shown below.

Normal Method

The Normal method uses a point on a surface to create a coordinate frame. The point defines the origin. The positive axis 3 direction is normal to the surface by using right-hand rule and crossing the surface’s parametric direction with the direction. The axis 1 direction is along the surface’s direction and the axis 2 direction is orthogonal to axis 1 and 3.

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To create a coordinate system using the 3 Point method:

1.	Click the Geometry tab, then select the 3 Point command under the Coord group.

 

Note:

The three points that will define the coordinate system must be created prior to defining the coordinate system.

2.	On the Geometry dialog box, select the type of coordinate system you wish to create, then select a point at the origin of the new coordinate system.

3.	Select a second point that lies on the Z-axis of the new coordinate system.

4.	Select third point that lies i the X-Z (R-Z or R-P) plane of the new coordinate system.

The new coordinate system axes should appear at the origin of the new coordinate system.

 

To create a coordinate system using the Normal method:

1.	Click the Geometry tab, then select the Normal command under the Coord group.

 

Note:

The point at the origin and the surface that will define the coordinate system must be created prior to defining the coordinate system.

2.	On the Geometry dialog box, select the type of coordinate system you wish to create, then select a point at the origin of the new coordinate system.

3.	Select the surface that will define the z and x axes.

The new coordinate system axes should appear at the origin of the new coordinate system.

Points

Points are modeling entities that represent a geometric point in 3-D space and have 3 coordinates, X, Y and Z as attributes. Points also have a label or ID. Points can be assigned properties such as a concentrated mass for use during a dynamic analysis. Points can also be assigned loads or constraints such as temperature in a thermal analysis.

To add a new point:

•	Click the Geometry tab, then select one of the point creation commands.

For descriptions of the point creation commands, see Geometry.

Curves

Curves define a locus of points through 3-D space and have both a start point and an endpoint. A curve has a label or ID. Curves can be used to idealize slender geometry or as a construction starting point for surfaces and solids. Loads and Boundary Conditions can be applied to curves and their endpoints. Curves can be meshed with beam finite elements.

To add a new curve:

•	Click the Geometry tab, then select one of the curve creation commands.

For descriptions of the curve creation commands, see Geometry.

Surfaces

Surfaces define regions in 3-D space without thickness bounded by edges and can include interior cutouts. A surface has a label or ID. Surfaces can be used to idealize thin geometry or as a construction starting point for solids. With surfaces, you can:

•	Apply Loads and Boundary Conditions over the whole surface, or individual edges and vertices

•	Assign properties such as thickness and material orientations

•	Mesh with triangular finite elements

•	Query for attributes such as ID and area

•	Construct more geometry

To add a new surface:

•	Click the Geometry tab, then select one of the surface creation commands.

For descriptions of the surface creation commands, see Geometry.

Solids

Solids define a region in 3-D space bounded by faces and may include cut-outs or interior voids. A solid has a label or ID. With solids you can:

•	Apply Loads and Boundary Conditions over the whole solid, individual faces, edges and vertices

•	Assign material properties and orientations

•	Mesh with tetrahedral finite elements

•	Query for attributes such as ID and volume

To add a new solid:

•	Click the Geometry tab, then select one of the solid creation commands.

For descriptions of the solid creation commands, see Geometry.