Time increment required is less than the minimum specified

[jonny17]

Hi,
I am making a model of a knee implant. I have applied a 8000N pressure load to the tibial surface. After a while the analysis aborts and I get the error message
Time increment required is less than the minimum specified
This is the last part of the message file
***NOTE: THE RATE OF CONVERGENCE IS VERY SLOW. CONVERGENCE IS JUDGED UNLIKELY.


***ERROR: TIME INCREMENT REQUIRED IS LESS THAN THE MINIMUM SPECIFIED



ANALYSIS SUMMARY:
TOTAL OF 17 INCREMENTS
13 CUTBACKS IN AUTOMATIC INCREMENTATION
198 ITERATIONS INCLUDING CONTACT ITERATIONS IF PRESENT
198 PASSES THROUGH THE EQUATION SOLVER OF WHICH
198 INVOLVE MATRIX DECOMPOSITION, INCLUDING
0 DECOMPOSITION(S) OF THE MASS MATRIX
1 REORDERING OF EQUATIONS TO MINIMIZE WAVEFRONT
0 ADDITIONAL RESIDUAL EVALUATIONS FOR LINE SEARCHES
0 ADDITIONAL OPERATOR EVALUATIONS FOR LINE SEARCHES
2 WARNING MESSAGES DURING USER INPUT PROCESSING
10 WARNING MESSAGES DURING ANALYSIS
0 ANALYSIS WARNINGS ARE NUMERICAL PROBLEM MESSAGES
3 ANALYSIS WARNINGS ARE NEGATIVE EIGENVALUE MESSAGES
1 ERROR MESSAGES



JOB TIME SUMMARY
USER TIME (SEC) = 5293.3
SYSTEM TIME (SEC) = 20.100
TOTAL CPU TIME (SEC) = 5313.4
WALLCLOCK TIME (SEC) = 5362



Please help

 

[IceBreakerSours]

That message is only a symptom of the problem(s) in the model. The more you tell us about the model (or even upload the CAE/INP), the more we can help.

http://www.eng-tips.com/faqs.cfm?fid=376

 

[jonny17]

here is the file

 

[IceBreakerSours]

Can you upload your INP? It seems the CAE is either corrupt or from an older version of ABAQUS.

http://www.eng-tips.com/faqs.cfm?fid=376

 

[jonny17]

here is the inp file

 

[IceBreakerSours]

Since your length units seem to be in millimeters, your pressure must be in MPa. I do not think 6240 MPa is a realistic load on one's knee. In fact, I think it should be more like 6.24 MPa and with that value your model converges in less than a minute. Given the simplicity of the problem, such a short time of convergence makes sense. Besides, contact pressure values in the knee literature also seem to be in this range.

http://www.eng-tips.com/faqs.cfm?fid=376

 

[jonny17]

ahh what a silly mistake. Thanks a lot!