Skip to main content

ABAQUS unit conversion for nanometer length.

Submitted by wanbot on
research

Hi all,

I ran a pre-buckling analysis using ABAQUS.  I chose nanometer as my length unit. So for the Young's modulus, since my sample has 100 GPa for the Young's modulus, I put 0.0000001 as the value for the Young's modulus under the material property in the ABAQUS.

However, the resulted eigenvalue (~2 nN) was not as what I expected (~2uN). Based on the calculation based on the Euler buckling theory, the critical load should be around 2 uN. 

In the pre-buckling analysis using ABAQUS, I use 1 as my load value. This unity value for the force should make the resulted eigenvalue to have the same value as the critical load.

I plan to run a post-buckling analysis by using the IMPERFECTION command and RIKS analysis. But first, I need to get the correct eigenvalue from my pre-buckling analysis.

Please advise me where I did wrong. Thank you in advance for your kind attention.

Wanbot

 

 

 

tuhinsinha.25

Are you running it in Standard or Explicit? I think you need to check the units of density too, if it is a dynamic analysis !! Make sure the units of density and stress (modulus) are consistent!

Fri, 12/12/2008 - 21:47 Permalink
P M G B A

Same problem with me , but at micro level, and am unable to figure it out (may be it simple and I am not getting it :-) ) . I draw a circle with 10 units radius . (Since my cirlce is 10 microns radius). Then what will be the input values of the stress and Pressure to be applied, if problem values are given as Stress=400 Pascals and Pressure=900 Pascals.
Regards

P M G

Fri, 04/17/2015 - 11:30 Permalink
wanbot

I think I have solved the problem. The problem was indeed due to the unit inconsistency.

This time I choose micrometer as the unit length. Then, the units for force and Young's modulus are uN and MPa respectively. 

By using the above unit, the resulted eigenvalue is quite reasonable.

Am I correct? 

Thanks.

Wabot

 

Sat, 12/13/2008 - 18:30 Permalink