Units assistance for loading of parts

AI Thread Summary
The discussion focuses on unit consistency in Abaqus modeling, specifically for parts built in millimeters. The user initially entered material data incorrectly by referring to density as mass and needed clarification on how to properly input a 5000N load. Responses emphasized using the correct units: density should be in tonne/mm^3, and applied force should be stated in Newtons, not as pressure. Additionally, strain was clarified as dimensionless, and proper formatting for unit notation was advised. Overall, the conversation highlighted the importance of maintaining unit consistency for accurate modeling results.
Corsan
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Hi all,

I am building a model in Abaqus and wondered if somone could assist with the units I need to enter.

I have built my parts using mm as the dimension, i.e. part is 10 units (mm) wide.

(To clarify this can also be entered as metres as in 10e-3, however I chose to be consistent with the mm approach).

Then for my material data I have entered my mass as 0.0025 (which was 2.5g/cc).
Youngs Modulus as 72000 and for the Plastic data I have entered my yield stress data as MPa (such as 425 with a plastic strain of 0.0090 (mm-3)).

As I wasn't consistent in using the SI measurements for mm (e-3) does this have a knock on effect for the above data?

Now for my loading of my parts can anyone clarify what I will need to enter for a 5000N load (pressure force)?

Thanks in advance
 
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Corsan: 2.5 g/cm^3 is called density, not mass. Enter your density in units of tonne/mm^3; i.e., 2.5e-9 tonne/mm^3, where 1 tonne = 1000 kg. Everything else you did currently sounds correct, except perhaps for strain. Applied force is called force, not pressure force. Pressure is in units of MPa. Enter your applied force in units of Newtons; i.e., 5000 N. In summary, use N, mm, MPa, tonne.

Strain is dimensionless. Therefore, strain does not change, regardless of the units. Therefore, I am not sure why you wrote mm^-3 after your strain value.

By the way, always leave a space between a numeric value and its following unit symbol. E.g., 5000 N, not 5000N. See the international standard for writing units[/color] (ISO 31-0[/color]). Or see any credible textbook.
 
Last edited:
nvn said:
Corsan: 2.5 g/cm^3 is called density, not mass. Enter your density in units of tonne/mm^3; i.e., 2.5e-9 tonne/mm^3, where 1 tonne = 1000 kg. Everything else you did currently sounds correct, except perhaps for strain. Applied force is called force, not pressure force. Pressure is in units of MPa. Enter your applied force in units of Newtons; i.e., 5000 N. In summary, use N, mm, MPa, tonne.

Strain is dimensionless. Therefore, strain does not change, regardless of the units. Therefore, I am not sure why you wrote mm^-3 after your strain value.

By the way, always leave a space between a numeric value and its following unit symbol. E.g., 5000 N, not 5000N. See the international standard for writing units[/color] (ISO 31-0[/color]). Or see any credible textbook.

Thank you for the response, that was exactly what I was looking for.
Appreciate the tip on units too :smile:
 
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