Units Confusion

[Yoman228]

I am having some unexpected results, Can someone check my units please as I always have confusion in them.

Units: N,mm
Length = mm
Force = N
Mass = Tonne (1.0E3kg)
Time = second
stress = MPa (N/mm^2)
Energy = J (J)
Density = Tonne/mm^3
Conductivity = J/(s.mm.C)
Specific Heat = J/(Tonne.C)

and the following numbers have been put in ABAQUS.
E of steel = 207000 (MPa)
Yield = 450 (MPa)
gav = 9807 (mm/s^2)
density of steel = 7.85 (ton/mm^3)

Is there a mistake there?

 

[Yoman228]

Silly me. the gravity should be 9.807E-3

 

[Yoman228]

Lol. To correct my last post, I think the gravity was correct as 9807 (mm^3).

However the density should be
7850 kg/m^3 = 7.85e-9 (ton/mm^3)

Is that correct?

 

[brep]

Yes. Correct now.

 

[Newuser2006]

actually every time i read any post about the units iam doubful again.so you stated above that used units:N,mm
should you define this at beginning or you are saying this comprehensively.can you further explain.
if a line for example is 10mm should i dimension the line as 10 or 0.01 the same also for pressure,1Mpa is simply one then or is it 10^6 in the pressure load.please reply soon

 

[Yoman228]

I normally define the unit as a comment under the heading. So the user can read from the input file that what unit I am using.

This is what the input in ABAQUS I used

Units: N,mm
Length = mm value= 1m ABAQUS value= 1000
Force = N value= 1N ABAQUS value= 1
Mass = Tonne (1.0E3kg) value= 7850 kg/m^3 = 7.85e-9
stress = MPa (N/mm^2) value= 1Mpa ABAQUS value = 1

Moreover, the ABAQUS stress results has the unit above. Hence, the plot show 100 in misses plot will mean 100MPa.

 

[Yoman228]

"Mass = Tonne (1.0E3kg) value= 7850 kg/m^3 = 7.85e-9 "

Should be

Density = ton/mm^3 value= 7850kg/m^3
ABAQUS value= 7.85e-9

 

[Newuser2006]

thanks very much,so the same for presure if it is 10Mpa abaqus values will be also 10.really good explanied from you