About units-In which version the default units was change?

yhr_123

my version is Hypermesh 2024.1. In preference I saw the default units was

MMKS (mm kg N s）. But when I create a material, in density the default value was 7.85e-09. It seems system still use tone/mm^3 for density. So which one is right? Should I change the value to 7.85e-06? By the way, I seem to remember old version use mm/ton/N/s. So which version it changed?

Gunter

Hello yhr_123,

This may be a bit confusing. But this Preferences entry only applies to sketching.
One can change this Preference to automatically scale the sketch.

The consistent unit system must be defined by the user, e.g. via the material density.
The values ​​of the material definition are crucial because they are passed on to the solver.

https://help.altair.com/hwsolvers/os/topics/solvers/os/unit_systems_run_optistruct_r.htm?zoom_highlight=units

https://help.altair.com/hwsolvers/os/topics/solvers/os/unit_systems_consistent_system_r.htm?zoom_highlight=unit+system

Best regards,
Gunter

yhr_123

https://community.altair.com/discussion/comment/190693#Comment_190693

I have just tried, no matter the density of the material is defined as 7.85 or 7.85e-09, other conditions are exactly the same, and the displacement value obtained by statics analysis is the same.But why？

Gunter

Hello yhr_123,

If there are no inertial forces or accelerations in the analysis, density does not matter.
For example, use a gravitational load in your model and you will see the difference.
In HyperMesh you can also measure density to see the difference.

Best regads,
Gunter

yhr_123

https://community.altair.com/discussion/comment/190695#Comment_190695

oh. I ignored this point. Now I understand, thanks.