How to chose a type of step for FEA

[MarceloM]

Hello,

I'm doing a simulation is Abaqus standard for see the foot pressures on the foot when a vertical force corresponding to half of the body weight is applied at the ground support reference point, and i don't know if i use a Static\general step (Full Newton or Quasi-Newton) or a static riks step for the best representation of this simulation with convergence.
Contacts:
Interations between the bones and cartilages are frictionless.
Bones are tied to the soft tissues.
Materials:
All the materials were considered isotropic and linear-elastic except the soft tissues that are mechanically
characterized by a non-linear elastic behaviour (high deformation).

Thank you.

 

[Mustaine3]

If you don't have the knowledge and need to activate something specific, then stay with the defaults. In your case it would be a normal general static step with it's default settings. Just think about activating NLGEOM and choosing a good initial increment size (otherwise use 0.1).

 

[MarceloM]

I'm doing a normal static step of a force(100N) with a inicial: 0.01 Time: 1 minimum: 1e-12 and i am geting:
***NOTE: THE SOLUTION APPEARS TO BE DIVERGING. CONVERGENCE IS JUDGED UNLIKELY.
It's this normal?

 

[Dave442]

convergence issues are not unexpected for nonlinear analyses.

do you get any warning messages in the .dat file that might narrow down your problem?

you can also dig into the .msg file to see if your convergence problems relate to contact etc.

 

[MarceloM]

I have ***NOTE: THE SOLUTION APPEARS TO BE DIVERGING. CONVERGENCE IS JUDGED UNLIKELY and THE SYSTEM MATRIX HAS NEGATIVE EIGENVALUES.
EXPLANATIONS ARE SUGGESTED AFTER THE FIRST OCCURRENCE OF THIS MESSAGE.

Some part of message file:

"AVERAGE PR. FLUX 2.709E-07 TIME AVG. PR. FLUX 2.234E-07
LARGEST RESIDUAL PR. FLUX -2.575E-14 AT NODE 35176
INSTANCE: SUPORTEPE-35-1
LARGEST INCREMENT OF VOL. LM. -2.422E-03 AT NODE 6151
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO VOL. LM. 6.818E-05 AT NODE 4074
INSTANCE: SUPORTEPE-35-1
ESTIMATE OF VOL. LM. CORRECTION -9.407E-07
PR. FLUX EQUILIB. ACCEPTED BASED ON SMALL RESIDUAL AND ESTIMATED CORRECTION

COMPATIBILITY ERRORS:
TYPE NUMBER EXCEEDING TOLERANCE MAXIMUM ERROR IN ELEMENT
COUPLING DISPLACEMENT 0 -2.348E-12 3
INSTANCE: OKLINHAS-4-1
COUPLING ROTATION 0 4.087E-12 3
INSTANCE: OKLINHAS-4-1

NUMBER OF EQUATIONS = 349287 NUMBER OF FLOATING PT. OPERATIONS = 2.56E+12

USING THE DIRECT SOLVER WITH 8 PROCESSORS

CHECK POINT START OF SOLVER

CHECK POINT END OF SOLVER

ELAPSED USER TIME (SEC) = 206.10
ELAPSED SYSTEM TIME (SEC) = 0.70000
ELAPSED TOTAL CPU TIME (SEC) = 206.80
ELAPSED WALLCLOCK TIME (SEC) = 27


***WARNING: THE SYSTEM MATRIX HAS 57 NEGATIVE EIGENVALUES.
EXPLANATIONS ARE SUGGESTED AFTER THE FIRST OCCURRENCE OF THIS MESSAGE.

ASYNCHRONOUS TRACKING ELEMENT LOOP STARTED


CONVERGENCE CHECKS FOR EQUILIBRIUM ITERATION 3

MAX. PENETRATION ERROR -2.32103E-12 AT NODE SUPORTEPE-26-1.15 OF CONTACT
PAIR (ASSEMBLY_S_SURF-537,ASSEMBLY_M_SURF-712)
MAX. CONTACT FORCE ERROR -11.1690E-09 AT NODE SUPORTEPE-26-1.15 OF CONTACT
PAIR (ASSEMBLY_S_SURF-537,ASSEMBLY_M_SURF-712)
THE CONTACT CONSTRAINTS HAVE CONVERGED.

AVERAGE FORCE 1.638E-02 TIME AVG. FORCE 1.013E-02
LARGEST RESIDUAL FORCE -6.839E-05 AT NODE 131 DOF 3
INSTANCE: SUPORTEPE-26-1
LARGEST INCREMENT OF DISP. 5.696E-06 AT NODE 11380 DOF 2
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO DISP. -2.871E-06 AT NODE 131 DOF 1
INSTANCE: SUPORTEPE-26-1
FORCE EQUILIBRIUM NOT ACHIEVED WITHIN TOLERANCE.

AVERAGE MOMENT 7.611E-10 TIME AVG. MOMENT 1.000E-02
LARGEST RESIDUAL MOMENT -1.277E-08 AT NODE 1 DOF 5
INSTANCE: OKLINHAS-4-1
LARGEST INCREMENT OF ROTATION -1.905E-04 AT NODE 1 DOF 6
INSTANCE: OKLINHAS-2-1
LARGEST CORRECTION TO ROTATION 6.154E-06 AT NODE 1 DOF 4
INSTANCE: OKLINHAS-4-1
THERE IS ZERO MOMENT EVERYWHERE


***WARNING: THERE IS ZERO MOMENT EVERYWHERE IN THE MODEL BASED ON THE DEFAULT
CRITERION. PLEASE CHECK THE VALUE OF THE AVERAGE MOMENT DURING THE
CURRENT ITERATION TO VERIFY THAT THE MOMENT IS SMALL ENOUGH TO BE
TREATED AS ZERO. IF NOT, PLEASE USE THE SOLUTION CONTROLS TO RESET
THE CRITERION FOR ZERO MOMENT.

AVERAGE PR. FLUX 2.709E-07 TIME AVG. PR. FLUX 2.234E-07
LARGEST RESIDUAL PR. FLUX -3.230E-14 AT NODE 4084
INSTANCE: SUPORTEPE-35-1
LARGEST INCREMENT OF VOL. LM. -2.418E-03 AT NODE 6151
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO VOL. LM. 8.060E-05 AT NODE 4074
INSTANCE: SUPORTEPE-35-1
VOL. LM. CORRECTION TOO LARGE COMPARED TO VOL. LM. INCREMENT

COMPATIBILITY ERRORS:
TYPE NUMBER EXCEEDING TOLERANCE MAXIMUM ERROR IN ELEMENT
COUPLING DISPLACEMENT 0 -4.447E-12 3
INSTANCE: OKLINHAS-4-1
COUPLING ROTATION 0 7.394E-12 3
INSTANCE: OKLINHAS-4-1

NUMBER OF EQUATIONS = 349287 NUMBER OF FLOATING PT. OPERATIONS = 2.56E+12

USING THE DIRECT SOLVER WITH 8 PROCESSORS

CHECK POINT START OF SOLVER

CHECK POINT END OF SOLVER

ELAPSED USER TIME (SEC) = 204.20
ELAPSED SYSTEM TIME (SEC) = 0.60000
ELAPSED TOTAL CPU TIME (SEC) = 204.80
ELAPSED WALLCLOCK TIME (SEC) = 26


***WARNING: THE SYSTEM MATRIX HAS 56 NEGATIVE EIGENVALUES.
EXPLANATIONS ARE SUGGESTED AFTER THE FIRST OCCURRENCE OF THIS MESSAGE.

ASYNCHRONOUS TRACKING ELEMENT LOOP STARTED


CONVERGENCE CHECKS FOR EQUILIBRIUM ITERATION 4

MAX. PENETRATION ERROR -7.36671E-12 AT NODE SUPORTEPE-26-1.15 OF CONTACT
PAIR (ASSEMBLY_S_SURF-537,ASSEMBLY_M_SURF-712)
MAX. CONTACT FORCE ERROR -35.4493E-09 AT NODE SUPORTEPE-26-1.15 OF CONTACT
PAIR (ASSEMBLY_S_SURF-537,ASSEMBLY_M_SURF-712)
THE CONTACT CONSTRAINTS HAVE CONVERGED.

AVERAGE FORCE 1.638E-02 TIME AVG. FORCE 1.013E-02
LARGEST RESIDUAL FORCE 1.034E-04 AT NODE 130 DOF 3
INSTANCE: SUPORTEPE-26-1
LARGEST INCREMENT OF DISP. 5.653E-06 AT NODE 11380 DOF 2
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO DISP. 4.602E-06 AT NODE 131 DOF 1
INSTANCE: SUPORTEPE-26-1
FORCE EQUILIBRIUM NOT ACHIEVED WITHIN TOLERANCE.

AVERAGE MOMENT 7.685E-10 TIME AVG. MOMENT 1.000E-02
LARGEST RESIDUAL MOMENT -1.160E-08 AT NODE 2 DOF 4
INSTANCE: OKLINHAS-1-1
LARGEST INCREMENT OF ROTATION -1.893E-04 AT NODE 1 DOF 6
INSTANCE: OKLINHAS-2-1
LARGEST CORRECTION TO ROTATION -1.008E-05 AT NODE 1 DOF 4
INSTANCE: OKLINHAS-4-1
THERE IS ZERO MOMENT EVERYWHERE


***WARNING: THERE IS ZERO MOMENT EVERYWHERE IN THE MODEL BASED ON THE DEFAULT
CRITERION. PLEASE CHECK THE VALUE OF THE AVERAGE MOMENT DURING THE
CURRENT ITERATION TO VERIFY THAT THE MOMENT IS SMALL ENOUGH TO BE
TREATED AS ZERO. IF NOT, PLEASE USE THE SOLUTION CONTROLS TO RESET
THE CRITERION FOR ZERO MOMENT.

AVERAGE PR. FLUX 2.709E-07 TIME AVG. PR. FLUX 2.234E-07
LARGEST RESIDUAL PR. FLUX -6.732E-14 AT NODE 35176
INSTANCE: SUPORTEPE-35-1
LARGEST INCREMENT OF VOL. LM. -2.420E-03 AT NODE 6151
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO VOL. LM. -1.242E-04 AT NODE 4074
INSTANCE: SUPORTEPE-35-1
VOL. LM. CORRECTION TOO LARGE COMPARED TO VOL. LM. INCREMENT

COMPATIBILITY ERRORS:
TYPE NUMBER EXCEEDING TOLERANCE MAXIMUM ERROR IN ELEMENT
COUPLING DISPLACEMENT 0 -9.000E-12 3
INSTANCE: OKLINHAS-4-1
COUPLING ROTATION 0 1.543E-11 3
INSTANCE: OKLINHAS-4-1

NUMBER OF EQUATIONS = 349287 NUMBER OF FLOATING PT. OPERATIONS = 2.56E+12

USING THE DIRECT SOLVER WITH 8 PROCESSORS

CHECK POINT START OF SOLVER

CHECK POINT END OF SOLVER

ELAPSED USER TIME (SEC) = 204.40
ELAPSED SYSTEM TIME (SEC) = 0.70000
ELAPSED TOTAL CPU TIME (SEC) = 205.10
ELAPSED WALLCLOCK TIME (SEC) = 27


***WARNING: THE SYSTEM MATRIX HAS 57 NEGATIVE EIGENVALUES.
EXPLANATIONS ARE SUGGESTED AFTER THE FIRST OCCURRENCE OF THIS MESSAGE.

ASYNCHRONOUS TRACKING ELEMENT LOOP STARTED


CONVERGENCE CHECKS FOR EQUILIBRIUM ITERATION 5

MAX. PENETRATION ERROR -2.50944E-12 AT NODE SUPORTEPE-26-1.15 OF CONTACT
PAIR (ASSEMBLY_S_SURF-537,ASSEMBLY_M_SURF-712)
MAX. CONTACT FORCE ERROR -12.0756E-09 AT NODE SUPORTEPE-26-1.15 OF CONTACT
PAIR (ASSEMBLY_S_SURF-537,ASSEMBLY_M_SURF-712)
THE CONTACT CONSTRAINTS HAVE CONVERGED.

AVERAGE FORCE 1.638E-02 TIME AVG. FORCE 1.013E-02
LARGEST RESIDUAL FORCE -1.554E-04 AT NODE 131 DOF 3
INSTANCE: SUPORTEPE-26-1
LARGEST INCREMENT OF DISP. 5.674E-06 AT NODE 11380 DOF 2
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO DISP. -2.528E-06 AT NODE 131 DOF 1
INSTANCE: SUPORTEPE-26-1
FORCE EQUILIBRIUM NOT ACHIEVED WITHIN TOLERANCE.

AVERAGE MOMENT 4.004E-10 TIME AVG. MOMENT 1.000E-02
LARGEST RESIDUAL MOMENT -9.076E-09 AT NODE 1 DOF 5
INSTANCE: OKLINHAS-4-1
LARGEST INCREMENT OF ROTATION -1.899E-04 AT NODE 1 DOF 6
INSTANCE: OKLINHAS-2-1
LARGEST CORRECTION TO ROTATION 5.786E-06 AT NODE 1 DOF 4
INSTANCE: OKLINHAS-4-1
THERE IS ZERO MOMENT EVERYWHERE


***WARNING: THERE IS ZERO MOMENT EVERYWHERE IN THE MODEL BASED ON THE DEFAULT
CRITERION. PLEASE CHECK THE VALUE OF THE AVERAGE MOMENT DURING THE
CURRENT ITERATION TO VERIFY THAT THE MOMENT IS SMALL ENOUGH TO BE
TREATED AS ZERO. IF NOT, PLEASE USE THE SOLUTION CONTROLS TO RESET
THE CRITERION FOR ZERO MOMENT.

AVERAGE PR. FLUX 2.709E-07 TIME AVG. PR. FLUX 2.234E-07
LARGEST RESIDUAL PR. FLUX -2.332E-14 AT NODE 35176
INSTANCE: SUPORTEPE-35-1
LARGEST INCREMENT OF VOL. LM. -2.420E-03 AT NODE 6151
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO VOL. LM. 6.663E-05 AT NODE 4074
INSTANCE: SUPORTEPE-35-1
VOL. LM. CORRECTION TOO LARGE COMPARED TO VOL. LM. INCREMENT

COMPATIBILITY ERRORS:
TYPE NUMBER EXCEEDING TOLERANCE MAXIMUM ERROR IN ELEMENT
COUPLING DISPLACEMENT 0 -2.324E-12 3
INSTANCE: OKLINHAS-4-1
COUPLING ROTATION 0 4.073E-12 3
INSTANCE: OKLINHAS-4-1


***NOTE: THE SOLUTION APPEARS TO BE DIVERGING. CONVERGENCE IS JUDGED UNLIKELY.


INCREMENT 27 STARTS. ATTEMPT NUMBER 3, TIME INCREMENT 6.020E-05

ASYNCHRONOUS TRACKING ELEMENT LOOP STARTED


NUMBER OF EQUATIONS = 349287 NUMBER OF FLOATING PT. OPERATIONS = 2.56E+12

USING THE DIRECT SOLVER WITH 8 PROCESSORS

CHECK POINT START OF SOLVER

CHECK POINT END OF SOLVER

ELAPSED USER TIME (SEC) = 207.80
ELAPSED SYSTEM TIME (SEC) = 0.80000
ELAPSED TOTAL CPU TIME (SEC) = 208.60
ELAPSED WALLCLOCK TIME (SEC) = 30


***WARNING: THE SYSTEM MATRIX HAS 54 NEGATIVE EIGENVALUES.
EXPLANATIONS ARE SUGGESTED AFTER THE FIRST OCCURRENCE OF THIS MESSAGE.

ASYNCHRONOUS TRACKING ELEMENT LOOP STARTED


CONVERGENCE CHECKS FOR EQUILIBRIUM ITERATION 1

MAX. PENETRATION ERROR -21.4291E-12 AT NODE SUPORTEPE-27-1.25 OF CONTACT
PAIR (ASSEMBLY_S_SURF-543,ASSEMBLY_M_SURF-543)
MAX. CONTACT FORCE ERROR -274.837E-09 AT NODE SUPORTEPE-27-1.95 OF CONTACT
PAIR (ASSEMBLY_S_SURF-543,ASSEMBLY_M_SURF-543)
THE CONTACT CONSTRAINTS HAVE CONVERGED.

AVERAGE FORCE 1.638E-02 TIME AVG. FORCE 1.013E-02
LARGEST RESIDUAL FORCE -2.486E-04 AT NODE 49 DOF 3
INSTANCE: SUPORTEPE-10-1
LARGEST INCREMENT OF DISP. 1.247E-06 AT NODE 11380 DOF 2
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO DISP. 1.247E-06 AT NODE 11380 DOF 2
INSTANCE: SUPORTEPE-35-1
FORCE EQUILIBRIUM NOT ACHIEVED WITHIN TOLERANCE.

AVERAGE MOMENT 3.963E-08 TIME AVG. MOMENT 1.000E-02
LARGEST RESIDUAL MOMENT -3.203E-07 AT NODE 1 DOF 5
INSTANCE: OKLINHAS-2-1
LARGEST INCREMENT OF ROTATION -4.134E-05 AT NODE 1 DOF 6
INSTANCE: OKLINHAS-2-1
LARGEST CORRECTION TO ROTATION -4.134E-05 AT NODE 1 DOF 6
INSTANCE: OKLINHAS-2-1
THE MOMENT IS ZERO EVERYWHERE BUT THE MOMENT RESIDUAL OR
THE ROTATION CORRECTION IS NON-ZERO

AVERAGE PR. FLUX 2.708E-07 TIME AVG. PR. FLUX 2.234E-07
LARGEST RESIDUAL PR. FLUX -4.417E-12 AT NODE 1302
INSTANCE: SUPORTEPE-35-1
LARGEST INCREMENT OF VOL. LM. -6.036E-04 AT NODE 6151
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO VOL. LM. -6.036E-04 AT NODE 6151
INSTANCE: SUPORTEPE-35-1
VOL. LM. CORRECTION TOO LARGE COMPARED TO VOL. LM. INCREMENT

COMPATIBILITY ERRORS:
TYPE NUMBER EXCEEDING TOLERANCE MAXIMUM ERROR IN ELEMENT
COUPLING DISPLACEMENT 0 -3.277E-10 3
INSTANCE: OKLINHAS-2-1
COUPLING ROTATION 0 3.445E-10 3
INSTANCE: OKLINHAS-2-1

NUMBER OF EQUATIONS = 349287 NUMBER OF FLOATING PT. OPERATIONS = 2.56E+12

USING THE DIRECT SOLVER WITH 8 PROCESSORS

CHECK POINT START OF SOLVER

CHECK POINT END OF SOLVER

ELAPSED USER TIME (SEC) = 207.10
ELAPSED SYSTEM TIME (SEC) = 0.70000
ELAPSED TOTAL CPU TIME (SEC) = 207.80
ELAPSED WALLCLOCK TIME (SEC) = 32


***WARNING: THE SYSTEM MATRIX HAS 54 NEGATIVE EIGENVALUES.
EXPLANATIONS ARE SUGGESTED AFTER THE FIRST OCCURRENCE OF THIS MESSAGE.

ASYNCHRONOUS TRACKING ELEMENT LOOP STARTED


CONVERGENCE CHECKS FOR EQUILIBRIUM ITERATION 2

MAX. PENETRATION ERROR -249.483E-15 AT NODE SUPORTEPE-27-1.27 OF CONTACT
PAIR (ASSEMBLY_S_SURF-543,ASSEMBLY_M_SURF-543)
MAX. CONTACT FORCE ERROR -2.86611E-09 AT NODE SUPORTEPE-27-1.114 OF CONTACT
PAIR (ASSEMBLY_S_SURF-543,ASSEMBLY_M_SURF-543)
THE CONTACT CONSTRAINTS HAVE CONVERGED.

AVERAGE FORCE 1.638E-02 TIME AVG. FORCE 1.013E-02
LARGEST RESIDUAL FORCE 2.127E-05 AT NODE 483 DOF 1
INSTANCE: SUPORTEPE-14-1
LARGEST INCREMENT OF DISP. 1.389E-06 AT NODE 11380 DOF 2
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO DISP. 1.424E-07 AT NODE 11385 DOF 2
INSTANCE: SUPORTEPE-35-1
ESTIMATE OF DISP. CORRECTION -1.218E-08
FORCE EQUILIB. ACCEPTED BASED ON SMALL RESIDUAL AND ESTIMATED CORRECTION

AVERAGE MOMENT 1.644E-09 TIME AVG. MOMENT 1.000E-02
LARGEST RESIDUAL MOMENT -3.048E-08 AT NODE 1 DOF 5
INSTANCE: OKLINHAS-2-1
LARGEST INCREMENT OF ROTATION -4.644E-05 AT NODE 1 DOF 6
INSTANCE: OKLINHAS-2-1
LARGEST CORRECTION TO ROTATION 6.432E-06 AT NODE 1 DOF 4
INSTANCE: OKLINHAS-2-1
THERE IS ZERO MOMENT EVERYWHERE


***WARNING: THERE IS ZERO MOMENT EVERYWHERE IN THE MODEL BASED ON THE DEFAULT
CRITERION. PLEASE CHECK THE VALUE OF THE AVERAGE MOMENT DURING THE
CURRENT ITERATION TO VERIFY THAT THE MOMENT IS SMALL ENOUGH TO BE
TREATED AS ZERO. IF NOT, PLEASE USE THE SOLUTION CONTROLS TO RESET
THE CRITERION FOR ZERO MOMENT.

AVERAGE PR. FLUX 2.708E-07 TIME AVG. PR. FLUX 2.234E-07
LARGEST RESIDUAL PR. FLUX -6.599E-14 AT NODE 39660
INSTANCE: SUPORTEPE-35-1
LARGEST INCREMENT OF VOL. LM. -6.038E-04 AT NODE 6151
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO VOL. LM. 1.470E-05 AT NODE 4086
INSTANCE: SUPORTEPE-35-1
ESTIMATE OF VOL. LM. CORRECTION -8.156E-07
PR. FLUX EQUILIB. ACCEPTED BASED ON SMALL RESIDUAL AND ESTIMATED CORRECTION

COMPATIBILITY ERRORS:
TYPE NUMBER EXCEEDING TOLERANCE MAXIMUM ERROR IN ELEMENT
COUPLING DISPLACEMENT 0 -7.506E-12 3
INSTANCE: OKLINHAS-2-1
COUPLING ROTATION 0 1.139E-11 3
INSTANCE: OKLINHAS-2-1
TIME INCREMENT MAY NOW INCREASE TO 9.031E-05

ITERATION SUMMARY FOR THE INCREMENT: 2 TOTAL ITERATIONS, OF WHICH
0 ARE SEVERE DISCONTINUITY ITERATIONS AND 2 ARE EQUILIBRIUM ITERATIONS.

TIME INCREMENT COMPLETED 6.020E-05, FRACTION OF STEP COMPLETED 0.816
STEP TIME COMPLETED 0.816 , TOTAL TIME COMPLETED 1.82

ASYNCHRONOUS OUTPUT DATABASE FRAME FLUSH STARTED



INCREMENT 28 STARTS. ATTEMPT NUMBER 1, TIME INCREMENT 9.031E-05

ASYNCHRONOUS TRACKING ELEMENT LOOP STARTED


NUMBER OF EQUATIONS = 349287 NUMBER OF FLOATING PT. OPERATIONS = 2.56E+12

USING THE DIRECT SOLVER WITH 8 PROCESSORS

CHECK POINT START OF SOLVER

CHECK POINT END OF SOLVER

ELAPSED USER TIME (SEC) = 206.40
ELAPSED SYSTEM TIME (SEC) = 0.70000
ELAPSED TOTAL CPU TIME (SEC) = 207.10
ELAPSED WALLCLOCK TIME (SEC) = 28


***WARNING: THE SYSTEM MATRIX HAS 54 NEGATIVE EIGENVALUES.
EXPLANATIONS ARE SUGGESTED AFTER THE FIRST OCCURRENCE OF THIS MESSAGE.

ASYNCHRONOUS TRACKING ELEMENT LOOP STARTED


CONVERGENCE CHECKS FOR EQUILIBRIUM ITERATION 1

MAX. PENETRATION ERROR -1.07057E-12 AT NODE SUPORTEPE-26-1.15 OF CONTACT
PAIR (ASSEMBLY_S_SURF-537,ASSEMBLY_M_SURF-712)
MAX. CONTACT FORCE ERROR -5.15166E-09 AT NODE SUPORTEPE-26-1.15 OF CONTACT
PAIR (ASSEMBLY_S_SURF-537,ASSEMBLY_M_SURF-712)
THE CONTACT CONSTRAINTS HAVE CONVERGED.

AVERAGE FORCE 1.649E-02 TIME AVG. FORCE 1.035E-02
LARGEST RESIDUAL FORCE -2.572E-05 AT NODE 323 DOF 3
INSTANCE: SUPORTEPE-26-1
LARGEST INCREMENT OF DISP. 2.130E-06 AT NODE 11380 DOF 2
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO DISP. 1.699E-06 AT NODE 131 DOF 1
INSTANCE: SUPORTEPE-26-1
DISP. CORRECTION TOO LARGE COMPARED TO DISP. INCREMENT

AVERAGE MOMENT 3.310E-10 TIME AVG. MOMENT 1.000E-02
LARGEST RESIDUAL MOMENT -5.861E-09 AT NODE 1 DOF 5
INSTANCE: OKLINHAS-2-1
LARGEST INCREMENT OF ROTATION -7.140E-05 AT NODE 1 DOF 6
INSTANCE: OKLINHAS-2-1
LARGEST CORRECTION TO ROTATION -2.631E-06 AT NODE 1 DOF 4
INSTANCE: OKLINHAS-4-1
THERE IS ZERO MOMENT EVERYWHERE


***WARNING: THERE IS ZERO MOMENT EVERYWHERE IN THE MODEL BASED ON THE DEFAULT
CRITERION. PLEASE CHECK THE VALUE OF THE AVERAGE MOMENT DURING THE
CURRENT ITERATION TO VERIFY THAT THE MOMENT IS SMALL ENOUGH TO BE
TREATED AS ZERO. IF NOT, PLEASE USE THE SOLUTION CONTROLS TO RESET
THE CRITERION FOR ZERO MOMENT.

AVERAGE PR. FLUX 2.709E-07 TIME AVG. PR. FLUX 2.255E-07
LARGEST RESIDUAL PR. FLUX 2.502E-14 AT NODE 1838
INSTANCE: SUPORTEPE-35-1
LARGEST INCREMENT OF VOL. LM. -9.083E-04 AT NODE 6151
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO VOL. LM. -3.983E-05 AT NODE 4074
INSTANCE: SUPORTEPE-35-1
ESTIMATE OF VOL. LM. CORRECTION 5.560E-08
PR. FLUX EQUILIB. ACCEPTED BASED ON SMALL RESIDUAL AND ESTIMATED CORRECTION

COMPATIBILITY ERRORS:
TYPE NUMBER EXCEEDING TOLERANCE MAXIMUM ERROR IN ELEMENT
COUPLING DISPLACEMENT 0 -7.923E-13 3
INSTANCE: OKLINHAS-2-1
COUPLING ROTATION 0 1.271E-12 3
INSTANCE: OKLINHAS-2-1

NUMBER OF EQUATIONS = 349287 NUMBER OF FLOATING PT. OPERATIONS = 2.56E+12

USING THE DIRECT SOLVER WITH 8 PROCESSORS

CHECK POINT START OF SOLVER

CHECK POINT END OF SOLVER

ELAPSED USER TIME (SEC) = 206.70
ELAPSED SYSTEM TIME (SEC) = 0.60000
ELAPSED TOTAL CPU TIME (SEC) = 207.30
ELAPSED WALLCLOCK TIME (SEC) = 28


***WARNING: THE SYSTEM MATRIX HAS 55 NEGATIVE EIGENVALUES.
EXPLANATIONS ARE SUGGESTED AFTER THE FIRST OCCURRENCE OF THIS MESSAGE.

ASYNCHRONOUS TRACKING ELEMENT LOOP STARTED


CONVERGENCE CHECKS FOR EQUILIBRIUM ITERATION 2

MAX. PENETRATION ERROR -1.92119E-12 AT NODE SUPORTEPE-26-1.15 OF CONTACT
PAIR (ASSEMBLY_S_SURF-537,ASSEMBLY_M_SURF-712)
MAX. CONTACT FORCE ERROR -9.24492E-09 AT NODE SUPORTEPE-26-1.15 OF CONTACT
PAIR (ASSEMBLY_S_SURF-537,ASSEMBLY_M_SURF-712)
THE CONTACT CONSTRAINTS HAVE CONVERGED.

AVERAGE FORCE 1.649E-02 TIME AVG. FORCE 1.035E-02
LARGEST RESIDUAL FORCE -7.110E-05 AT NODE 131 DOF 3
INSTANCE: SUPORTEPE-26-1
LARGEST INCREMENT OF DISP. 2.160E-06 AT NODE 11380 DOF 2
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO DISP. -2.302E-06 AT NODE 131 DOF 1
INSTANCE: SUPORTEPE-26-1
FORCE EQUILIBRIUM NOT ACHIEVED WITHIN TOLERANCE.

AVERAGE MOMENT 4.682E-10 TIME AVG. MOMENT 1.000E-02
LARGEST RESIDUAL MOMENT -9.437E-09 AT NODE 1 DOF 5
INSTANCE: OKLINHAS-4-1
LARGEST INCREMENT OF ROTATION -7.233E-05 AT NODE 1 DOF 6
INSTANCE: OKLINHAS-2-1
LARGEST CORRECTION TO ROTATION 5.484E-06 AT NODE 1 DOF 4
INSTANCE: OKLINHAS-4-1
THERE IS ZERO MOMENT EVERYWHERE


***WARNING: THERE IS ZERO MOMENT EVERYWHERE IN THE MODEL BASED ON THE DEFAULT
CRITERION. PLEASE CHECK THE VALUE OF THE AVERAGE MOMENT DURING THE
CURRENT ITERATION TO VERIFY THAT THE MOMENT IS SMALL ENOUGH TO BE
TREATED AS ZERO. IF NOT, PLEASE USE THE SOLUTION CONTROLS TO RESET
THE CRITERION FOR ZERO MOMENT.

AVERAGE PR. FLUX 2.709E-07 TIME AVG. PR. FLUX 2.255E-07
LARGEST RESIDUAL PR. FLUX -1.920E-14 AT NODE 35176
INSTANCE: SUPORTEPE-35-1
LARGEST INCREMENT OF VOL. LM. -9.078E-04 AT NODE 6151
INSTANCE: SUPORTEPE-35-1
LARGEST CORRECTION TO VOL. LM. 6.301E-05 AT NODE 4074
INSTANCE: SUPORTEPE-35-1
VOL. LM. CORRECTION TOO LARGE COMPARED TO VOL. LM. INCREMENT

COMPATIBILITY ERRORS:
TYPE NUMBER EXCEEDING TOLERANCE MAXIMUM ERROR IN ELEMENT
COUPLING DISPLACEMENT 0 -2.785E-12 3
INSTANCE: OKLINHAS-4-1
COUPLING ROTATION 0 4.672E-12 3
INSTANCE: OKLINHAS-4-1
"

 

[MarceloM]

See picture pls.

Thanks for the help.

 

[Dave442]

At a glance I would consider the following:

THE SYSTEM MATRIX HAS 55 NEGATIVE EIGENVALUES.

THE CONTACT CONSTRAINTS HAVE CONVERGED.

FORCE EQUILIBRIUM NOT ACHIEVED WITHIN TOLERANCE.
LARGEST RESIDUAL FORCE -7.110E-05 AT NODE 131 DOF 3
INSTANCE: SUPORTEPE-26-1

THERE IS ZERO MOMENT EVERYWHERE

VOL. LM. CORRECTION TOO LARGE COMPARED TO VOL. LM. INCREMENT
LARGEST CORRECTION TO VOL. LM. 6.301E-05 AT NODE 4074
INSTANCE: SUPORTEPE-35-1

Step 2 seems to run well until ~80% of the total load is applied.
What happens at that point?

 

[MarceloM]

SUPORTEPE-35-1 it's the soft tissues.
SUPORTEPE-26-1 it's a front cartilage tha is falling apart (see picture).
The contact between the bones and cartilage its Tangencial Behavior:Frictionless and Normal behavior: "Hard COntact" (i try with Allow separation on and off and the same happens.

 

[Dave442]

how do you connect bone to cartilage?

It looks like these regions have completely separated in your image.

 

[MarceloM]

Interanction: face-to-face : adjust only to remove overclosure

 

[Dave442]

the cartilage is held in place through contact with the neighboring bones? is that realistic?

when the bones move such that this contact is interrupted the cartilage will be totally unsupported?

this is probably the reason why your analysis crashes.

i think cartilage and bone should be tied to each other using a representation of the anatomy (tendons/ligaments)

 

[MarceloM]

I will tied them and see what happens.
Shold i tie only the problematic cartilages or all of them?

Than you.

 

[Dave442]

are they tied together in reality??? is that any more realistic?

you have to have a clear understanding of the native anatomy.

what connects all the bones, cartilage etc together in reality?

when you understand the anatomy, then you can figure out how to model it accurately.

 

[MarceloM]

From literature the cartilages are frictionless but as you can see they are falling apart.

 

[Dave442]

you're describing an interaction property.

it's used to specify how frictional forces develop between two parts when they slide in contact.

it doesn't describe how individual parts are attached to each other, or to other regions of a model.

in reality you have a complex series of muscles/tendons/tissue that hold everything in place in the foot.

you neglected all that in your model and it looks like everything just falls apart under loading (as you would expect).

maybe im missing something here??

 

[IceBreakerSours]

Please seek expert guidance. A free online public forum isn't ideal for learning the basics; it works best when you have a specific question and you have some idea of what you are dealing with.

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[MarceloM]

I have done all the ligaments and attach them to the geometry by coupling (continuum distributing) but now the problem is diverging with only the ***NOTE: THE SOLUTION APPEARS TO BE DIVERGING. CONVERGENCE IS JUDGED UNLIKELY. Pls see the picture.

 

[Dave442]

there isn't really any information in the picture to help figure out your problem.

do you get any warning messages in the .dat file?

can you look through the .msg file to try narrow down the problem (don't post it)?

 

[MarceloM]

I just needed a small increment, now it works fine.

Thanks for all!