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 SPECIFIED-ANALYSIS 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