Learning Forum

[troy.baker]

I understand LS Dyna is "unitless" where everything is built off of relative scaling.  If my mesh sizing is in mm, mass units are input in grams, I should be working with pascals and uN.  What I was wondering, is how to scale the magnetic units to fit this.  As many magnetic units are based off of Amps, which don't necessarily have a relation to mm, grams, or seconds.  

From what I understand, EM keywords (or at least *EM_EXTERNAL_FIELD)  use B field in Tesla.  Which can be written as N/(Am).  To scale that for a mm/g/uN system, it means that a numerical value put in would be on the scale of mTesla, right?

*EM_PERMANENT_MAGNET specifically mentions Hc being written in A/m (pg 488 in the Em manual https://lsdyna.ansys.com/wp-content/uploads/2025/04/LS-DYNA_Manual_Vol_III_R16.pdf), for my unit system that should be scaled to A/mm. Or am I reading the manual wrong; where remark 1 is simply telling me how I should scale a given A/m value to B field values, and like the rest of the EM keywords, all values should be written as a B field in some scale of Tesla.

[Raman Babu]

Hello,

Please see the snapshot below for your reference.

Basically, the unit system for EM is fixed and based on the fundamental Henry/meter rather than Ampere, which means all values must be scaled accordingly (including current values) in this shifted reference frame.

Regards,

Raman Babu