UNITS

[leo81]

Hi guys,

excuse me a stupid but important question about units:

if I want express all in N-Kg-mm

how have I to set the density value of 1g/(cm)^3?

Is it correct?:

F = 10 (10 N)
E = 0.010 (10 kPa)
density= 1E-6 (1 g/(cm)^3 = 1E-6 Kg/(mm)^3)

thanks,

Leo

 

[vumat721]

yes

 

[Nileo2005]

I don't believe so. If you have Simuila's online support system, search for Answer ID 2579; there is a really nifty table which I found very convient to print out. Says if you want to use N and MPa units, you need to use tonnes instead of kilograms, so 1g/cm^3 would be 1e-9 tonnes/mm^3.

 

[vumat721]

That Abaqus answer is in kg, meter, sec, so it's not really helpful because leo81 wants kg, millimeters, sec.

BUT, upon further inspection, I was only checking his density number, cause the question wasn't clear. But force should be in mN

Force = kg*mm/s^2 = 1 mN
Stress = kg/mm*s^2 = 1 kPa
Density = kg/mm^3

Therefore a density of 1 g/cm^3 = 1e-6 kg/mm^3, so you'd input 1e-6 into Abaqus.

If you instead used Mg (= 1e3 kg) as the mass, then you get a really nice system of units

Mass = Mg
Length = mm
Time = s
Force = Mg*mm/s^2 = 1 N
Stress = Mg/mm*s^2 = 1 MPa
Density = Mg/mm^3 = 1e12 kg/m^3

So a density of 1 g/cm^3 = 1e-9 Mg/mm^3, so you'd input 1e-9 into Abaqus