2013

Mass properties for solids
DescriptionMass property
The mass moments of inertia, which is used when computing the force
required to rotate an object about a given axis, such as a wheel rotating
about an axle. The formula for mass moments of inertia is
Moments of iner-
tia
mass_moments_of_inertia = object_mass * radius
axis
2
Mass moments of inertia unit is mass (grams or slugs) times the dis-
tance squared.
Property used to determine the forces causing the motion of an object.
It is always calculated with respect to two orthogonal planes. The for-
mula for product of inertia for the YZ plane and XZ plane is
Products of iner-
tia
product_of_inertia
YZ,XZ
= mass * dist
centroid_to_YZ
* dist
centroid_to_XZ
This XY value is expressed in mass units times the length squared.
Another way of indicating the moments of inertia of a solid. The for-
mula for the radii of gyration is
Radii of gyration
gyration_radii = (moments_of_inertia/body_mass)
1/2
Radii of gyration are expressed in distance units.
Calculations that are derived from the products of inertia and that
have the same unit values. The moment of inertia is highest through
Principal mo-
ments and
a certain axis at the centroid of an object. The moment of inertia isX,Y,Z directions
about centroid lowest through the second axis that is normal to the first axis and that
also passes through the centroid. A third value included in the results
is somewhere between the high and low values.
Calculations Based on the Current UCS
The following table shows the parameters that control the units in which
mass properties are calculated.
Parameters that control MASSPROP units
Used to calculateParameter
Mass of solidsDENSITY
Volume of solidsLENGTH
M Commands | 603