Problem with hyperelastic material: Time increment required is less than the minimum specified

[jastafari]

Hi All,

Am running simulation on silicone tubing (hyperelastic), applying inner pressure to 120 mmHg (~0.016 N/mm2). Getting error:Time increment required is less than the minimum specified

Analysis:
ANALYSIS SUMMARY:
TOTAL OF 3 INCREMENTS
1 CUTBACKS IN AUTOMATIC INCREMENTATION
26 ITERATIONS INCLUDING CONTACT ITERATIONS IF PRESENT
26 PASSES THROUGH THE EQUATION SOLVER OF WHICH
26 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
3 WARNING MESSAGES DURING USER INPUT PROCESSING
7 WARNING MESSAGES DURING ANALYSIS
0 ANALYSIS WARNINGS ARE NUMERICAL PROBLEM MESSAGES
6 ANALYSIS WARNINGS ARE NEGATIVE EIGENVALUE MESSAGES
1 ERROR MESSAGES



JOB TIME SUMMARY
USER TIME (SEC) = 103.90
SYSTEM TIME (SEC) = 0.90000
TOTAL CPU TIME (SEC) = 104.80
WALLCLOCK TIME (SEC) = 106


Any help?

 

[ZIlyas]

Hi,

I would recommend the following steps.

[ul]
[li]First in Property Module->Material Manager->Evaluate, evaluate your hyperelastic material. There are possibilities instabilities in the material parameters/models used.[/li]
[li]Second in Mesh Module->Verify Mesh->Size Metrics try to look for the Stable time increment.[/li]
[li]Last(Not a very recommended idea) in the Step Module->Edit Step->Incrementation, try to reduce the Initial increment less the current Minimum value and observe first 2-3 increments. This will just make sure if your model is correct at the cost of time and computation.[/li]
[/ul]

 

[IceBreakerSours]

Too many increments is a symptom, not the cause of non-convergence. What do the .msg/.dat files say? What kind of analysis are you performing? What element type are you using? Are your units consistent?

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

http://www.eng-tips.com/faqs.cfm?fid=1083