Display Mass/COG/MOI information
Altair EmployeeHypermesh proposes multiple tools to evaluate mass, center of gravity and moments of inertia. The article below describes each tool, its inputs, and outputs. Feel free to use the links below If you want to look directly for one of these tools:
Measure
Validate -> Mass
Aerospace -> Mass and COG review tool (OptiStruct and Nastran)
Matrix browser
Tcl instructions
About mass computation
Measure
From the Home tools, click the Measure tool satellite icon.
The tool allows component, element or geometry selection.
In case of geometry selection, it returns length for line selection, area for surface selection and volume for solid selection.
In case of component or element selection, it returns:
- Area
- Volume
- Mass, both structural and non-structural
- Center of gravity expressed in global system
- Moments of Inertia computed from the COG of the selection
- Bounding box dimensions
Display options are available, for:
- Plotting COG of the selection
- Optionally creating a node at COG location
- Plotting component bounding box, either from global system axis or part orientation
Limitations:
not recommended in 2021.x and 2022 for sequential component selection, that is to say for evaluating one after the other different components. Select Elements -> by Components instead or use the other tools available if you want to get component information for a selection of components.
Validate -> Mass
Validate -> Mass scan all the model and returns by default mass details (*), plus COG and moment of inertia (to be requested through micro dialog 
), per component:
(*) see the About mass computation section at the end of the article for extra details
For each component, moments of inertia are expressed from the global origin (0,0,0).
For the complete model (info at the bottom of the table), moments of inertia are expressed from the model center of gravity.
Limitations:
For running the tool on a limited number of components, the components to be ignored have to be deactivated first from the Entity State browser, which can be set visible from the top menu View.
Aerospace -> Mass and COG review tool (OptiStruct and Nastran)
This tool is especially intended for graphical display.
Aerospace menu is hidden by default. It can be shown by right clicking in the top drop-down menu.
It allows either to select components or elements.
Once the selection done, user can display one of the following dimensions:
- Masses (*)
- COG coordinate, X, Y or Z
- Moments of inertia components expressed from the origin (IXX, IYY, IZZ, …)
- Moments of inertia components expressed from the component COG (IXXcog, IYYcog, IZZcog, …)
(*) see the About mass computation section at the end of the article for extra details
The Draw Shape option allows to bring in the graphic are some markers whose size will change depending on the value of each component.
Matrix Browser:
Matrix Browser is a tool available in Hypermesh/HyperView, which allows to query information on entities within the model, and optionally to change attributes on the fly.
It is available from the Post ribbon. You can also retrieve it any version by searching Matrix from CTRL + F or the top right search icon.
As a first step, you need to populate the cells:
- Click on HM Data source, select Entities=Components and click on Query to select the components of interest
- Once the component selected, click on Component’s column o get access to data names. Consider data names as component attributes.
- Select the data names of interest and click on Query
Among the component attributes, you can access to:
- Masses (*)
- COG coordinate, X, Y or Z
- Moments of inertia components expressed from the origin (IXX, IYY, IZZ, …)
- Moments of inertia components expressed from the component COG (IXXcog, IYYcog, IZZcog, …)
(*) see the About mass computation section at the end of the article for extra details
Tcl instructions
Mass, COG and moment of inertia can also be requested for tcl instructions.
hm_getmass is recommended for getting the mass of a selection. See the About mass computation section for the different type of mass that can be returned
For Center of Gravity and moments of Inertia, you can do almost the same that what does the matrix browser, using the hm_getvalue instruction:
hm_getvalue comps id=14 dataname=cogx
Matrix Browser can help retrieving the attributes to be queried by selectin the entity of interest and checking what are the Datanames available.
You can also check for dataname section of the help.
About mass computation
Most of the tools above return different mass information: structural, non-structural, transferred, lumped, engineering.
For more information about the different tools, please refer to the help page below