small equation solver pivot terms
small equation solver pivot terms
(OP)
I am analysing a 3-D model of pile foundation under lateral load. The soil is modelled as DP (Draucker-Prager) material model with contact element between pile and soil. The solution converges to the true results for small loads (approximately for 20 % of ultimate loads) but for larger loads does not. The warning message is “there are 7 small equation solver pivot terms”.
Please help me if you have any idea.
Please help me if you have any idea.





RE: small equation solver pivot terms
This is generally a warning because of large rotations, displacements, etc. being detected in your model. In your case it might mean that some bifurcation level has been reached or exceeded. I don't know for sure because you haven't provided enough information about your model/type of analysis/etc. What happens when the load goes above 20%, are your displacements to big, too small or what?
RE: small equation solver pivot terms
The type of analysis is static and the large deformation is possible (nlgeom, on).
The elements which I use are solid95 (for soil and pile) and conta174 and targe170 (for contact elements).
With increasing the load, the displacements will be big.
RE: small equation solver pivot terms
RE: small equation solver pivot terms
Thank you for your help. As you said, the reason of small equation solver pivot term was large deformation. I used DP material model and in this model weight of material is very important. I defined density for material but I forgot to define gravity (using Acel command).
Regards
Jili
RE: small equation solver pivot terms
I have similar problem like yours (3D mesh, DP model, 170/174 contact pair) and same problem that calculation did not converge (a few small equation solver pivot terms after about 10% of load). Did you solve your problem after turn Acel on?
Thanks.
Yan
RE: small equation solver pivot terms
At the moment I do not work on that project but I will start that again soon. For the same problem at the other project (but without contact elements), I have solved the problem using the finer mesh and changing the solution method. I have the better convergence with full Newton Raphson method (nropt, full).
Regards
Jili