About Mass Properties
Mass properties describe the mass and moments of inertia of a mass idealization. You can define mass properties in one of the following ways, depending on the situation.
• Click Refine Model and then click the arrow next to 
Mass. Click 
Mass Properties.
Mass. Click Mass Properties.• If you are defining an advanced mass, you can also use the More button in the Properties area of the Mass Definition dialog box to create a mass property.
In either case, Creo Simulate displays the Mass Properties dialog box, which you can use to create a mass property. From this dialog box, you can also edit, copy, or delete an existing property. To create a new property, click New. The Mass Property Definition dialog box appears. You use this dialog box to define the property.
This dialog box includes the following items:
• Name—Type a name for the mass property, or use the default name provided.
• Description—Type an optional description.
• Mass—Specify the value of the mass and select units of mass from the adjacent drop-down list. You must type a positive value.
• Moments of Inertia—Specify the moments of inertia about each mass element's center of gravity with respect to the axes and principal planes of the WCS. Select units for moment of inertia or retain the principal units.
For 3D models, you can specify values for Ixx, Iyy, Izz, Ixy, Ixz, and Iyz. For plane strain and 2D axisymmetric models, you can specify a value for only Izz. For plane stress models, you cannot specify any moments of inertia. The default value for all moments is 0.
Depending on the situation, you may not need to specify all of the diagonal terms when you specify moments of inertia.
Note that Creo Simulate labels the moments of inertia using Cartesian component directions. To review the equivalent component directions for cylindrical and spherical components, see Axis and Component Equivalents in Different Coordinate Systems.