Querying mass properties

Context:

The mass properties calculated in Abaqus/CAE account for mass being distributed in a continuum throughout the model, whereas the Abaqus solver calculates the mass properties according to the discretization of the model. When compared to the mass properties provided in the data (.dat) file of an Abaqus analysis, the values of the moments of inertia obtained in the mass properties query may be substantially different, especially for finite element models with coarse meshes.

In the Visualization module, the mass properties are always calculated based on model data (undeformed shape) even if the deformed shape is displayed in the viewport.

If the region that you query contains mesh occupying the space where geometry exists but that mesh is unassociated with any geometry, the volume/area will effectively be counted twice in the calculations. You should query unmeshed regions and/or unassociated geometry to avoid encountering this behavior.

You cannot query for the mass properties of a part to which an Eulerian section is assigned. However, you can query for the mass properties of an Eulerian part, provided it does not have an Eulerian section assignment.

You can query for the mass properties of a model even when portions of the model are not completely defined. For example, if your selection includes a part instance that does not have a section assignment, Abaqus/CAE includes the area of that part instance in mass properties calculations but excludes the part instance from calculations of volume, volume centroid, mass, center of mass, and moments of inertia. Abaqus/CAE also appends a warning message to the data indicating that the data are incomplete; in this example, the message would indicate that a portion of your selection was missing a section assignment. This approach enables you to investigate aspects of your model at various points during the modeling process without displaying misleading information about mass-related quantities.

Abaqus/CAE returns a warning message with the mass properties data in the following situations:

Geometry not considered by the mass properties query: Abaqus/CAE computes mass properties for shells, solids, beams, trusses, and rotary inertia elements; and in modules other than the Visualization module, Abaqus/CAE also includes point and nonstructural mass elements in its mass properties calculations. If your selection includes other geometry such as axisymmetric elements, springs, connectors, or gaskets (or, in the Visualization module, if your selection includes point and nonstructural mass elements), Abaqus/CAE excludes that geometry from its calculations. The exclusion of point and nonstructural mass elements from mass properties results in the Visualization module means that mass properties results may be different in the Visualization module than they are in other modules.
Ineligible thickness values: If your selection includes a section definition with a missing thickness value or a thickness value of zero, Abaqus/CAE excludes the selection from calculations of mass, center of mass, and moments of inertia. Similarly, Abaqus/CAE does not consider regions with a variable thickness (defined using a nodal thickness or field thickness) or regions using a thickness value that is not applicable to the corresponding sections specified.
Density not defined or improperly defined: If your selection includes a region in which a value for density is not available or is defined improperly, Abaqus/CAE excludes that region from all mass-related calculations in the mass properties query. The region's area and volume data are included in the final calculations.
Missing section assignment: If your selection includes a region that does not have a section assigned to it, Abaqus/CAE excludes that region from all mass-related calculations in the mass properties query. The region's area and volume data are included in the final calculations.
Inclusion of shell offsets or reinforcements: Abaqus/CAE does not consider shell offset values when calculating the center of volume or surface area, and Abaqus/CAE also excludes any reinforcements in your model from all mass property calculations. If your query includes shell offsets or reinforcements, Abaqus/CAE returns the query results with an appropriate warning message.
Composite sections: When your mass properties query selection includes a part or region with a composite section, Abaqus/CAE calculates mass- and volume-related values in the mass properties query using smeared properties located on the element.
Inclusion of nonstructural mass entities: Abaqus/CAE does not consider nonstructural mass on wires, such as mass-per-length values. In addition, when geometry is not meshed, Abaqus/CAE cannot compute center of mass and moment of inertia values as accurately as it can for meshed geometry.

Select ToolsQuery from the main menu bar to use the Query toolset, or select the tool in the Query toolbar.
Click Mass properties.
Additional options appear in the prompt area.
If desired, click Options to modify query options.
1. In the Mass Properties Query Options dialog box, you can modify accuracy, density, thickness parameters, and the point about which the moment of inertia is computed. You can click Reset to return the options to the previously stored values.
2. Click OK to save your changes and to close the dialog box.
If you include a native mesh in your selection, you can query for the mass properties of the geometry or of the native mesh. To query for the mass properties of the native mesh, click Options in the prompt area, then toggle on Use mesh when available for accurate properties in the dialog box that appears.
For selections that include complex geometry, Abaqus/CAE may take a long time to compute the volume properties. You can reduce the computation time by instructing Abaqus/CAE to stop the computation when a certain relative accuracy has been achieved. Click Options in the prompt area, then select a relative accuracy of Low, Medium, or High from the dialog box that appears. Higher relative accuracy yields a more accurate result but takes longer to calculate. Relative accuracy settings are available only for geometry selections, not for mesh selections.
If your selection includes regions in which thickness or density is either missing or improperly defined, you can supply values for the thickness or density of these regions for the mass properties calculations. Providing these values to the query does not change these values in the model itself.
Click Options in the prompt area, then provide values greater than zero in the appropriate fields.
If you want to query mass properties for the entire assembly, select Query entire assembly and click Done.
Abaqus/CAE displays the following information in the message area: the volume, volume centroid, mass, center of mass, and moments of inertia about the center of mass or about a specified point. If the assembly includes shell features, Abaqus/CAE reports the surface area and area centroid for one side of the shell faces as well.
If you want to query mass properties for the entire part (when the part is displayed in the Part module or Property module), select Query entire part and click Done.
Abaqus/CAE displays in the message area the volume, volume centroid, mass, center of mass, and moments of inertia about the center of mass or about a specified point for the part. If the part includes shell features, Abaqus/CAE reports the surface area and area centroid for one side of the shell faces as well.
If you want to query mass properties for one or more part instances in an assembly, highlight Select part instances, highlight one or more part instances in the viewport, and click Done.
Abaqus/CAE displays in the message area the volume, volume centroid, mass, center of mass, and moments of inertia about the center of mass or about a specified point for the part instance or instances. If the part instance or part instances you query include shell features, Abaqus/CAE reports the surface area and area centroid for one side of the shell faces as well.
If you want to query mass properties for one or more geometric regions in an assembly, part, or part instance, highlight Select geometric regions, highlight one or more regions in the viewport, and click Done.
Abaqus/CAE displays in the message area the volume, volume centroid, mass, center of mass, and moments of inertia about the center of mass or about a specified point for the region or regions. If the region or regions you query include shell features, Abaqus/CAE reports the surface area and area centroid for one side of the shell faces as well.
If you want to query mass properties for one or more faces in an assembly, part, or part instance, highlight Select geometric regions, highlight one or more regions in the viewport, and click Done.
1. From the prompt area, highlight Select geometric regions.
2. From the Selection toolbar, select Faces from the list of object types.
3. Select one or more faces from the viewport, and then click Done.
Abaqus/CAE displays the total surface area of the selected faces. You can query for multiple shell surfaces or multiple faces, but you cannot perform a query for both shells and geometric faces.
If you want to query mass properties for one or more elements in an assembly, part, or part instance, highlight Select elements, highlight one or more elements in the viewport, and click Done.
Abaqus/CAE displays in the message area the volume, volume centroid, mass, center of mass, and moments of inertia about the center of mass or about a specified point for the region or regions. If the region or regions you query include shell features, Abaqus/CAE reports the surface area and area centroid for one side of the shell faces as well.
If you want to query mass properties for one or more element faces in an assembly, part, or part instance, perform the following steps:
1. From the prompt area, highlight Select elements.
2. From the Selection toolbar, select Element Faces from the list of object types.
3. Select one or more elements faces from the viewport, and then click Done.
Abaqus/CAE displays the total surface area of the selected element faces. You can query for multiple element faces and for element faces from multiple shell surfaces or multiple faces, but you cannot perform a query for element faces from both shells and geometric faces.

You can also use general queries, including querying mass properties, in the Visualization module. For more information, see Querying the model in the Visualization module.