if I use cm for length, what should I use for density?

[abaqusforum]

I don't have lots of experience in dynamic analysis. if I use cm for length in dynamic analysis, what should I use for density? Youngs modulus is kgf/(cm^2)?
Thanks!

 

[GBor]

I recommend scaling your model to meters.

 

[rb1957]

density ... gm/cm^3 ?

E ... convert N/m^2 ... N = 1000 gm*g (weight of 1 gm)
but g = 9810 cm/sec^2
so N = 1000*100 gm*cm/sec^2
and m = 100 cm

so that looks like 1 N/m^2 = 10 (gm*cm/sec^2)/cm^2

 

[abaqusforum]

seems it is not g/cm^3. I have a model generated by somebody else in cm. those density of steel is 10^(-5). I want to convert to meters.

 

[rb1957]

if we knew what "somebody else" did, then we would be smart !

btw ... forget the jibberish about N = 1000gm*g ... of course 1N = 1000g*1m/sec^2 = 1000g*100cm/sec^2 ... g is only relevent in your model if you have inertial forces.

steel is 0.3 lbf/in^3 (weight density) = 0.009 lbm/in^3 = 0.004 kg/in^3 = 0.00026 kg/cm^3

whatever, i think converting your model to meters is the way to go

 

[johnhors]

Density of Steel is about 7850 kg/m^3 = 0.00785 kg/cm^3

 

[Denial]

As I said in the other forum where you posted this question: Whatever units you use, make sure that the formula F=ma applies.

 

[FeX32]

Firstly, don't post in multiple forums. Forums are subject specific.
Secondly, if you can't convert from centimeter to meter then.....well I guess I could just say: 1m=100cm.
TTFN


Fe

 

[jhardy1]

As others have said - you can use ANY consistent set of units that you like. If you are not sure whether your units are fully consistent, I would strongly recommend using base SI units (kg, m, s, N, etc).

One set of units using cm is the CGS system as follows:

Length: cm
Mass: g
Time: s
Force: dyne (symbol: dyn) = g.cm/s^2 = 10^(-5) N

Other units:

Density: g/cm^3
Modulus / Stress: barye (symbol: Ba)= dyn/cm^2 = 0.1 Pa
Work / Energy: erg = 10^(-7) J
Velocity: cm/s
Acceleration: cm/s^2
Gravity: 1 g = 980.7 cm/s^2

http://en.wikipedia.org/wiki/Centimeter_gram_second_system_of_units

Hope this helps!

 

[abaqusforum]

Thanks for all the help! the problem has been solved.