Common Errors and Warnings in Convergence

Common Errors and Warnings in Convergence Problems-Abaqus ERROR: TOO MANY INCREMENTS NEEDED TO COMPLETE THE STEP 

Check the message file for any warning messages, such as numerical singularity or zero pivot warnings, that may be causing slow convergence  If there appear to be no convergence issues, then you may need to increase the limit to the number of increments for that step ERROR: TOO MANY ATTEMPTS MADE FOR THIS INCREMENT –ANALYSIS TERMINATED 

This is just an error message which gives reason for why Abaqus finally aborted  Do not modify the solver controls to increase the number of allowable attempts per increment  Check the message file for warning messages that could cause convergence difficulties  Check the model definition, and make sure that the model can actually withstand the applied loads ERROR: TIME INCREMENT REQUIRED IS LESS THAN MINIMUM SPECIFIEDANALYSIS ENDS 

Again, this is just an error message which gives reason for why Abaqus finally aborted-it is not a suggestion by Abaqus to reduce the minimum allowable increment size  Check the message file for warning messages that could cause convergence difficulties  Check the model definition, and make sure that the model can actually withstand the applied loads WARNING: THE STRAIN INCREMENT HAS EXCEEDED FIFTY TIMES THE STRAIN TO CAUSE FIRST YIELD AT 500 POINTS 

Indicates excessive plastic yielding in the given increment  Possible causes would be: · Excessive or unrealistic loading (inconsistent units, for example) · Incorrect or insufficient stress-strain plastic data · Insufficient mesh refinement · Unstable deformation, such as buckling NOTE: The factor ‘fifty’ mentioned in the warning message cannot be modified

WARNING: ELEMENT 441 IS DISTORTING SO MUCH THAT IT TURNS INSIDE OUT Possible causes would be: · Insufficient mesh refinement · Hourglassing in first-order reduced integration elements · Inconsistent units for material properties and/ or loads · Excessive or unrealistic loads · Adjusting slave nodes of severely overclosed surfaces for contact pairs or tie constraints (initial overclosures) WARNING: THE SYSTEM MATRIX HAS 9 NEGATIVE EIGENVALUES Possible causes would be: . Some form of loss of stiffness suggesting that the stiffness matrix is assembled about a non-equilibrium state: . Geometrical instability: buckling, compression . Material instability: inappropriate hyperelastic material models, onset of perfect plasticity . Numerically, the use of Lagrange multipliers in certain cases may also lead to these warning messages . Use of 3D second-order elements as contact (slave) surfaces  Typically, these warning messages do not appear in converged iterations . If they do, ensure that the solution is physically acceptable WARNING: SOLVER PROBLEM. NUMERICAL SIGULARITY WHEN PROCESSING NODE 1 D.O.F. 3 RATIO=3.141E+15  Typically suggests an unconstrained rigid body motion  Even if the analysis runs to completion with these warnings, the results may not be accurate WARNING: SOLVER PROBLEM. ZERO PIVOT WHEN PROCESSING NODE 1 D.O.F.1  Typically suggests an overconstraint  Even if the analysis runs to completion with these warnings, the results will not be accurate