Units assistance for loading of parts

  1. 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
  2. jcsd
  3. nvn

    nvn 2,124
    Science Advisor
    Homework Helper

    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 (ISO 31-0). Or see any credible text book.
    Last edited: Mar 30, 2012
  4. Thank you for the response, that was exactly what I was looking for.
    Appreciate the tip on units too :smile:
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