May 8, 2023 at 7:34 am
Colin Zhang
Subscriber
Hello Ashish,
 
My model involves material plasticity and contact pairs. It failed at the 4th step. 
 
 
#The 2nd step involves many warnings like below.  Any actions needed?
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 *** WARNING ***                         CP =    1035.703   TIME= 12:46:21
 The current Level of Difficulty on the PCGOPT command may be inefficient for this model due to coupling equation(s) and/or constraint equation(s) present.  If this solution appears to be inefficient, you may find that switching to a Level of Difficulty equal to 1 [PCGOPT,1] more efficient for this model.      
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#The 3rd step involve warnings, notes, and errors like below.  Any actions needed ?
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 *** WARNING ***                         CP =   38533.234   TIME= 23:15:25
 The current Level of Difficulty on the PCGOPT command may be inefficient for this model due to coupling equation(s) and/or constraint equation(s) present.  If this solution appears to be inefficient, you may find that switching to a Level of Difficulty equal to 1 [PCGOPT,1] more efficient for this model.                 
                                                                         
     FORCE CONVERGENCE VALUE  =  0.5708E+05  CRITERION=   2632.    
     MOMENT CONVERGENCE VALUE =   28.08      CRITERION=  0.5102E-04
 
 *** NOTE ***                            CP =   38790.953   TIME= 23:19:43
 The preconditioned conjugate gradient solver failed to converge, and therefore no solution was obtained. The equation solver is now being automatically switched to the sparse solver (EQSLV,SPARSE) to allow this analysis to continue.                                              
     DISP CONVERGENCE VALUE   =  0.4709      CRITERION=  0.1124    
    EQUIL ITER   1 COMPLETED.  NEW TRIANG MATRIX.  MAX DOF INC= -0.4709    
     DISP CONVERGENCE VALUE   =  0.1518      CRITERION=  0.1147    
     LINE SEARCH PARAMETER =  0.3224     SCALED MAX DOF INC = -0.1518    
     FORCE CONVERGENCE VALUE  =  0.3857E+05  CRITERION=   171.9    
     MOMENT CONVERGENCE VALUE =   23.37      CRITERION=   248.1     <<< CONVERGED
    EQUIL ITER   2 COMPLETED.  NEW TRIANG MATRIX.  MAX DOF INC=  0.7681E-01
     DISP CONVERGENCE VALUE   =  0.7563E-01  CRITERION=  0.1171     <<< CONVERGED
     LINE SEARCH PARAMETER =  0.9847     SCALED MAX DOF INC =  0.7563E-01
     FORCE CONVERGENCE VALUE  =   1965.      CRITERION=   175.3    
     MOMENT CONVERGENCE VALUE =   2.255      CRITERION=   253.0     <<< CONVERGED
    EQUIL ITER   3 COMPLETED.  NEW TRIANG MATRIX.  MAX DOF INC=  0.9337E-02
     DISP CONVERGENCE VALUE   =  0.9337E-02  CRITERION=  0.1194     <<< CONVERGED
     LINE SEARCH PARAMETER =   1.000     SCALED MAX DOF INC =  0.9337E-02
     FORCE CONVERGENCE VALUE  =   401.8      CRITERION=   179.3    
     MOMENT CONVERGENCE VALUE =  0.5137E-01  CRITERION=   258.7     <<< CONVERGED
    EQUIL ITER   4 COMPLETED.  NEW TRIANG MATRIX.  MAX DOF INC=  0.6605E-02
     DISP CONVERGENCE VALUE   =  0.6605E-02  CRITERION=  0.1219     <<< CONVERGED
     LINE SEARCH PARAMETER =   1.000     SCALED MAX DOF INC =  0.6605E-02
     FORCE CONVERGENCE VALUE  =   198.5      CRITERION=   183.0    
     MOMENT CONVERGENCE VALUE =  0.5709E-01  CRITERION=   264.1     <<< CONVERGED
    EQUIL ITER   5 COMPLETED.  NEW TRIANG MATRIX.  MAX DOF INC= -0.6990E-02
     DISP CONVERGENCE VALUE   =  0.6990E-02  CRITERION=  0.1244     <<< CONVERGED
     LINE SEARCH PARAMETER =   1.000     SCALED MAX DOF INC = -0.6990E-02
     FORCE CONVERGENCE VALUE  =   210.0      CRITERION=   187.0    
     MOMENT CONVERGENCE VALUE =  0.3405E-01  CRITERION=   270.0     <<< CONVERGED
    EQUIL ITER   6 COMPLETED.  NEW TRIANG MATRIX.  MAX DOF INC= -0.7422E-02
     DISP CONVERGENCE VALUE   =  0.7422E-02  CRITERION=  0.1269     <<< CONVERGED
     LINE SEARCH PARAMETER =   1.000     SCALED MAX DOF INC = -0.7422E-02
     FORCE CONVERGENCE VALUE  =   142.2      CRITERION=   191.0     <<< CONVERGED
     MOMENT CONVERGENCE VALUE =  0.1315E-01  CRITERION=   275.6     <<< CONVERGED
    >>> SOLUTION CONVERGED AFTER EQUILIBRIUM ITERATION   6
 *** LOAD STEP     3   SUBSTEP     4  COMPLETED.    CUM ITER =    109
 *** TIME =   2.40000         TIME INC =  0.100000    
 *** MAX PLASTIC STRAIN STEP = 0.1679E-02   CRITERION = 0.1500    
 *** AUTO TIME STEP:  NEXT TIME INC = 0.15000      INCREASED (FACTOR = 1.5000)
 
 *** NOTE ***                            CP =   43066.172   TIME= 00:30:59
 The equation solver is automatically reverting from the sparse solver back to the preconditioned conjugate gradient solver.                   
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 *** ERROR ***                           CP =   46802.359   TIME= 01:33:17
 Element 73021 (type = 2, SOLID187) (and maybe other elements) has become highly distorted.  Excessive distortion of elements is usually a symptom indicating the need for corrective action elsewhere.  Try incrementing the load more slowly (increase the number of substeps or decrease the time step size).  You may need to improve your mesh to obtain elements with better aspect ratios.  Also consider the behavior of materials, contact pairs, and/or constraint equations.  Please rule out other root causes of this failure before attempting rezoning or nonlinear adaptive solutions.  If this message appears in the first iteration of first substep, be sure to perform element shape checking.  
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 *** NOTE ***                            CP =  201257.641   TIME= 20:30:35
 The incremental plastic strain 62.2106268% computed in this iteration is larger than the criterion of 15% leading to bisection.  You may try incrementing the load more slowly by increasing the number of substeps or use the CUTCONTROL command to re-specify this criterion.       
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#The solution stopped at load step 4, substep 16 with error as shown below. How can I correct the errors?
 
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   >>> SOLUTION CONVERGED AFTER EQUILIBRIUM ITERATION   7
 *** LOAD STEP     4   SUBSTEP    15  COMPLETED.    CUM ITER =    416
 *** TIME =   3.41150         TIME INC =  0.100000E-01
 *** MAX PLASTIC STRAIN STEP = 0.3756       CRITERION = 0.1500    
 *** AUTO STEP TIME:  NEXT TIME INC = 0.10000E-01  UNCHANGED
 
     FORCE CONVERGENCE VALUE  =   2963.      CRITERION=   277.2    
     MOMENT CONVERGENCE VALUE =  0.4922      CRITERION=  0.5102E-04
     DISP CONVERGENCE VALUE   =  0.5154E-01  CRITERION=  0.1124     <<< CONVERGED
    EQUIL ITER   1 COMPLETED.  NEW TRIANG MATRIX.  MAX DOF INC= -0.5154E-01
     DISP CONVERGENCE VALUE   =  0.2969E-01  CRITERION=  0.1147     <<< CONVERGED
     LINE SEARCH PARAMETER =  0.5760     SCALED MAX DOF INC = -0.2969E-01
     FORCE CONVERGENCE VALUE  =   1259.      CRITERION=   136.2    
     MOMENT CONVERGENCE VALUE =  0.2087      CRITERION=   196.5     <<< CONVERGED
    EQUIL ITER   2 COMPLETED.  NEW TRIANG MATRIX.  MAX DOF INC=  0.2179    
     DISP CONVERGENCE VALUE   =  0.1155E-01  CRITERION=  0.1171     <<< CONVERGED
     LINE SEARCH PARAMETER =  0.5303E-01 SCALED MAX DOF INC =  0.1155E-01
     FORCE CONVERGENCE VALUE  =   1190.      CRITERION=   138.9    
     MOMENT CONVERGENCE VALUE =  0.1977      CRITERION=   200.5     <<< CONVERGED
    EQUIL ITER   3 COMPLETED.  NEW TRIANG MATRIX.  MAX DOF INC=  0.1992    
     DISP CONVERGENCE VALUE   =  0.1992      CRITERION=  0.1194    
     LINE SEARCH PARAMETER =   1.000     SCALED MAX DOF INC =  0.1992    
     FORCE CONVERGENCE VALUE  =   7999.      CRITERION=   141.7    
     MOMENT CONVERGENCE VALUE =  0.8859E-02  CRITERION=   204.6     <<< CONVERGED
    EQUIL ITER   4 COMPLETED.  NEW TRIANG MATRIX.  MAX DOF INC= -0.3821E-01
     DISP CONVERGENCE VALUE   =  0.3821E-01  CRITERION=  0.1219     <<< CONVERGED
     LINE SEARCH PARAMETER =   1.000     SCALED MAX DOF INC = -0.3821E-01
     FORCE CONVERGENCE VALUE  =   4421.      CRITERION=   144.7    
     MOMENT CONVERGENCE VALUE =  0.9883E-02  CRITERION=   208.8     <<< CONVERGED
    EQUIL ITER   5 COMPLETED.  NEW TRIANG MATRIX.  MAX DOF INC= -0.1681    
     DISP CONVERGENCE VALUE   =  0.6666E-01  CRITERION=  0.1244     <<< CONVERGED
     LINE SEARCH PARAMETER =  0.3966     SCALED MAX DOF INC = -0.6666E-01
     FORCE CONVERGENCE VALUE  =   3094.      CRITERION=   147.6    
     MOMENT CONVERGENCE VALUE =  0.6133E-02  CRITERION=   213.1     <<< CONVERGED
    EQUIL ITER   6 COMPLETED.  NEW TRIANG MATRIX.  MAX DOF INC= -0.3314    
 
 *** ERROR ***                           CP =  248350.578   TIME= 09:35:44
 Element 1293421 (type = 5, SOLID187) (and maybe other elements) has become highly distorted.  Excessive distortion of elements is usually a symptom indicating the need for corrective action elsewhere.  Try incrementing the load more slowly (increase the number of substeps or decrease the time step size).  You may need to improve your mesh to obtain elements with better aspect ratios.  Also consider the behavior of materials, contact pairs, and/or constraint equations.  Please rule out other root causes of this failure before attempting rezoning or nonlinear adaptive solutions.  If this message appears in the first iteration of first substep, be sure to perform element shape checking.  
 
 *** WARNING ***                         CP =  248350.781   TIME= 09:35:45
 The unconverged solution (identified as time 4 substep 999999) is output for analysis debug purposes.  Results should not be used for any other purpose.                    
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Although the solution has many element distortions, they might not be the root cause. May increasing the Maximum substeps from 100 to 200 help solve the errors? 
 
Thank you,
Colin