Calculate Mass

Use the Mass tool to calculate the mass, center of gravity (COG), and moments of inertia (MOI) of the model.

  1. From the Validate ribbon, click the Mass tool.


    Figure 1.
  2. Click on the guide bar to select a calculation option.
    Mass only
    Only calculate the masses.
    Mass, Cog and Inertia
    Calculate the masses, center of gravities, and moments of inertia of the model.
  3. Use the drop-down menu to group values based on assembly or include.
  4. Click Compute.
    The detailed mass values are displayed in a table.


    Figure 2.
    Total Mass
    Represents the engineering mass as:
    Total Mass = Structural Mass + Non-Structural Mass
    Structural Mass
    Represents the physical mass of the structure, calculated from the property and material characteristics assigned to the FE mesh.
    Non-Structural Mass
    Represents the additional solver masses added on the structural mesh.
    • In the LS-DYNA profile:
      • *ELEMENT_MASS_PART
      • *ELEMENT_MASS_PART_SET
      • MAREA value in *SECTION_SHELL
      • NSM value in *SECTION_BEAM
      • Lumped Mass
    • In the Radioss profile:
      • /ADMAS/3
      • /ADMAS/4
      • /ADMAS/6
      • /ADMAS/7
      • Lumped Mass
    • In the PAM-CRASH profile:
      • NSMAS /
      • NSMAS2 /
    Lumped Mass
    Represents the portion of the non-structural mass, which is distributed on structural nodes.
    • In the LS-DYNA profile:
      • *ELEMENT_MASS
      • *ELEMENT_MASS_NODE_SET
      • *ELEMENT_INERTIA
      • *ELEMENT_SEATBELT_ACCELEROMETER
    • In the Radioss profile:
      • /ADMAS/0
      • /ADMAS/1
      • /ADMAS/2
      • /ADMAS/5
    Mass in Rigid Body
    Represents the mass of the nodal rigid body elements in the collector.
    • In the LS-DYNA profile:
      • *CONSTRAINED_NODAL_RIGID_BODY
    • In the Radioss profile:
      • /RBODY
    Transferred Mass
    Represents the nodal mass transferred to the nodal rigid body elements or rigid Parts.
    • In the LS-DYNA profile:
      • Nodal mass transferred to *CONSTRAINED_NODAL_RIGID_BODY
      • Nodal mass transferred to rigid *PART connected with CONSTRAINED_EXTRA_NODE or CONSTRAINED_RIGID_BODIES.
      • The lumped mass defined on nodes is also transferred to the rigids.
    • In the Radioss profile:
      • Nodal mass transferred to /RBODY
      • The lumped mass defined on nodes is also transferred to the rigids.
    Solver Mass
    Represents the mass as it is calculated by the solver.
    • In the LS-DYNA profile:
      • For deformable *PART, the Lumped Mass is not considered:

        Solver Mass = Structural Mass + Non-Structural Mass + Transferred Mass – Lumped Mass on non-rigid nodes

        This value can be compared to the total mass of part in mass properties of part written in the d3hsp file.

      • For rigid *PART, the lumped mass is considered:

        Solver Mass = Structural Mass + Non-Structural Mass + Transferred Mass

        This value can be compared to the mass of rigid body in mass properties of rigid body material written in the d3hsp file.

    • In the Radioss profile:
      • The Lumped Mass is not considered into the /PART mass.

        Solver Mass = Structural Mass + Non-Structural Mass + Transferred Mass – Lumped Mass on non-rigid nodes

    The relevant Total values are displayed at the bottom of the dialog.


    Figure 3.
    Total Mass
    Represents the total engineering mass of the model and is the sum of the values in the Total Mass column of the table.
    Total Structured Mass
    The sum of the values in the Structural Mass column of the table.
    Total Non-Structured Mass
    The sum of the values in the Non-Structural Mass column of the table.
    Total Rigid Body Mass
    The sum of the Mass in Rigid Body column and represents the total mass of the nodal rigid body elements in the model.
    Total Transferred Mass
    The sum of the Transferred Mass column of the table.
    Total Solver Mass
    The sum of the Solver Mass column of the table.
    Total Model Mass
    Represents the final total mass of the model as it is calculated by the solver:
    • Total Model Mass = Total Solver Mass + lumped mass on non-rigid nodes

      For LS-DYNA, this value can be compared to the total mass in summary of mass written in the d3hsp file.

      For Radioss, this value can be compared to the TOTAL MASS value written in the 0.out file.