Also, negative eigenvalue means that your stifness matrix lost its positive definiteness. This could be due to not only rigid motion as xerf said but could be to instability (material or numerical) or failure of your material
corus
But still I need to run two analyses
Corus : What do you mean boundary conditions that you think will apply
A clearer answer is highly appreciated
Clay1969
Corus
When you are establishing heat BCs through the ground. You have to have some info regarding the existing thermal gradient in that region. Every region has different thermal gradient (which represents the steady state condition at that region). So if you have no measured data within the...
For transient heat transfer analysis one should define the initial BCs first. Initial BCs are difficult to predict within the system. Hence it is advised that one first runs Steady state analysis (Boundary Value Problem) with assigning BC temperature at Measured points . THe STep of Steady State...
I have tried to run a simple problem (one element) specifying the correct initail time step for partial saturation seepage (Consolidation Step)and I start to face the same problem. I do not know why the convergence is very poor when simulating partial saturation seepage even after Changing the...