How to use 'Gravity card'

allen_21155

I have confused the definition of "gravity vector scale factor"(G) which is a parameter in the GRAV card. It's that mean the gravitational acceleration in kg/s^2 or the weight in Newton?  Here is a Screenshot. Does anyone have an idea? 

Adriano_Koga

gravity is just gravity acceleration (m/s2 or mm/s2 or whatever units you're using).

 

This is a vector, so it has the magnitude and its components (X, Y and Z multipliers) defining its direction.

 

So, if G = 9810mm/s2, and you want to make it work in -Z direction, your vector will be N1=0, N2=0 and N3=-1.0

if you want to apply a 4G load in Y+ direction, G=9180mm/s2 and N1=0, N2=4.0 and N3=0.

 

Vladimir_Gantovnik

Adriano A. Koga_21884 said:

gravity is just gravity acceleration (m/s2 or mm/s2 or whatever units you're using).

 

This is a vector, so it has the magnitude and its components (X, Y and Z multipliers) defining its direction.

 

So, if G = 9810mm/s2, and you want to make it work in -Z direction, your vector will be N1=0, N2=0 and N3=-1.0

if you want to apply a 4G load in Y+ direction, G=9180mm/s2 and N1=0, N2=4.0 and N3=0.

 

Adriano, so if the model is in inches (US system), G=386.0885 in/s^2, then for 75G in x+ direction I should use this card:

GRAV     3       1      386.0885   75.       0.      0.  

Is it correct?

p.s. For US units (if the density is in lb/in^3) we also add (Nastran type parameter):

PARAM, WTMASS, 0.00259

Thank you!

Vladimir