# ANSYS query...

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I'm 'playing' with ANSYS.

I'm a bit confused about units though.

Can I work in mm and apply loads in N or do I have to model in metres?

SS

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Yes, and the unit of stress will come out in MPa. Watch out for the displacement as you should "fudge" the units of the Young's modulus and input it them N/mm^2 to get displacements in mm. Same for density if you have inertia loading.

Enjoy!

Gill

s wrote:

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are you saying yes to modelling in metres or millimetres. I assume you mean metres.

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s wrote: >

All the units need to be consistent. If you use N and mm, then the material properties need to be in N/mm and so forth.

This is true for all (or most all) FEA software packages.

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I get it - everything is proportional. It doesnt matter if you use metric or imperial as long as you stay constant and remember that if you work in mm then the output displacement is in mm.

SS

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Be careful with density, for N-mm-s the mass must be input in metric tons, i.e. 1000kg. This leads to a density in [t/mm^3] eg.

Steel, density = 7.85E-9 [t/mm^3] = 7.85E-9 [ 1000kg / 1.E-9 m^3] = 7850 kg/m^3

Although N-mm-t-s is a very typical unit system used in the German automotive industry, it can be confusing if you perform any coupled analyses like thermo-mechanical or fluid structure.

In this case it's easier to scale the model to meters and use the SI (N-m-kg-s) system.

Rainer

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