Spring analysis

[GMarsh]

Hi,

I am trying to do a simple static analysis with 4 springs connected between two blocks. The stiffness of each spring is 1e5 N/m. The bottom block is fixed and top block is pulled with 10 kN. So using simple F=KX,I am suppose to get 25mm of displacement for top block. But I am getting 25.31mm. For such a simple analysis what could be the possible error ? I don't think mesh convergence might be an issue (?) as spring is single element. I am applying 10kN as a uniform pressure on top surface of top block. Element is Spring2, with fixed direction as axis.

Also for a perfectly vertical pull, I am noticing a rotation of top block. I am attaching the picture here. Can someone kindly suggest where I might be doing wrong.

Thanks in advance.

Regards
Pat

 

[PamCrash]

Are these blocks perfectly rigid ?

 

[GMarsh]

Thank you PamCrash. Yes, when compared to spring stiffness blocks are rigid. I defined them as 3D deformable bodies with steel properties - E = 200GPa. I made some quick calculation to check what can be elongation in both blocks due to applied 10kN load. It works out to be 0.3 and 1.6 micron in small and big block respectively. When compared to error of 0.3mm, these are very small. So there is something else which is causing this error and also the rotation of top block as it is being pulled up(as shown in diagram in earlier post). I think springs definition may not be correct, though I can't find any error in that. You may see the way I defined springs in the attached figure.

Many thanks for your help.