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Hello
I am having issues with the mass analysis tool in CREO parametric 4.0 giving me rubbish in the moment of inertia calculation. To test the software I drew a simple rod with a diameter of 50mm, a length of 100mm and a density of 7.8270820e-06 kg / mm^3 (steel).
A simple (and exact) hand calculation for the moment of inertia is:
I=(1/12)*mass*length^2
around the centre of gravity and:
I=(1/3)*mass*length^2 around one end.
My hand calculation gives:
Mass = 1.54kg
I around CoG=1.28e3 kg/mm^2
I around one end = 5.12e3 kg/mm^2
The figures produced by the mass analysis tool are given as:
mass=1.54kg
I around CoG=1.52e3 kg/mm^2
I around one end = 5.36e3 kg/mm^2
As the inertia around one end should be exactly 4x the inertia around the CoG this is clearly wrong as it is not even self consistent.
Where am I going wrong as I need to trust this tool to correctly calculate the inertia of large, complex assemblies.
All the best
Does this information help at all?
I think Creo is using the moment of inertia of a cylinder, not a rod. Compare these online calculators:
http://www.amesweb.info/SectionalPropertiesTabs/Mass-Moment-Inertia-Rod.aspx
http://www.amesweb.info/SectionalPropertiesTabs/Mass-Moment-of-Inertia-Cylinder.aspx
Hi TomU
You are right: thanks for that.
All the best