ABAQUS Error msg - Pls Guide..

[hiwiansys]

Hi All,

I am doing a simulation of Hip Bone Prosthesis.A brief introduction about this would be,I have a 3 D model of bone inside which a cavity is made(whose dimensions are in sink with implant which will be assembled inside it) and an implant has been assembled in abaqus.Now I need to run a simple static analysis on this.I have meshed both bone and implant using tetrahedron elements using free meshing technique since creating a mapped mesh for bone(irregular shape) will be difficult.I have created an interaction in initial step which generates contact between bone and implant,here I was not able to select complete cavity inside bone as it is not visible in view port.Boundary Conditions given in initial step and load in step 1.I got the below mentioned error msgs,after referring the documents in this forum I corrected certain details like,increasing steps,decreasing minimum/initial and maximum increment,still the below error persists,I need your help in this.I request you to give me some advice.



AUTOMATIC TIME CONTROL WITH -
A SUGGESTED INITIAL TIME INCREMENT OF 1.00
AND A TOTAL TIME PERIOD OF 1.00
THE MINIMUM TIME INCREMENT ALLOWED IS 1.000E-05
THE MAXIMUM TIME INCREMENT ALLOWED IS 1.00

LINEAR EQUATION SOLVER TYPE DIRECT SPARSE

CONVERGENCE TOLERANCE PARAMETERS FOR FORCE
CRITERION FOR RESIDUAL FORCE FOR A NONLINEAR PROBLEM 5.000E-03
CRITERION FOR DISP. CORRECTION IN A NONLINEAR PROBLEM 1.000E-02
INITIAL VALUE OF TIME AVERAGE FORCE 1.000E-02
AVERAGE FORCE IS TIME AVERAGE FORCE
ALTERNATE CRIT. FOR RESIDUAL FORCE FOR A NONLINEAR PROBLEM 2.000E-02
CRITERION FOR ZERO FORCE RELATIVE TO TIME AVRG. FORCE 1.000E-05
CRITERION FOR RESIDUAL FORCE WHEN THERE IS ZERO FLUX 1.000E-05
CRITERION FOR DISP. CORRECTION WHEN THERE IS ZERO FLUX 1.000E-03
CRITERION FOR RESIDUAL FORCE FOR A LINEAR INCREMENT 1.000E-08
FIELD CONVERSION RATIO 1.00
CRITERION FOR ZERO FORCE REL. TO TIME AVRG. MAX. FORCE 1.000E-05
CRITERION FOR ZERO DISP. RELATIVE TO CHARACTERISTIC LENGTH 1.000E-08

VOLUMETRIC STRAIN COMPATIBILITY TOLERANCE FOR HYBRID SOLIDS 1.000E-05
AXIAL STRAIN COMPATIBILITY TOLERANCE FOR HYBRID BEAMS 1.000E-05
TRANS. SHEAR STRAIN COMPATIBILITY TOLERANCE FOR HYBRID BEAMS 1.000E-05
SOFT CONTACT CONSTRAINT COMPATIBILITY TOLERANCE FOR P>P0 5.000E-03
SOFT CONTACT CONSTRAINT COMPATIBILITY TOLERANCE FOR P=0.0 0.100
DISPLACEMENT COMPATIBILITY TOLERANCE FOR DCOUP ELEMENTS 1.000E-05
ROTATION COMPATIBILITY TOLERANCE FOR DCOUP ELEMENTS 1.000E-05

TIME INCREMENTATION CONTROL PARAMETERS:
FIRST EQUILIBRIUM ITERATION FOR CONSECUTIVE DIVERGENCE CHECK 4
EQUILIBRIUM ITERATION AT WHICH LOG. CONVERGENCE RATE CHECK BEGINS 8
EQUILIBRIUM ITERATION AFTER WHICH ALTERNATE RESIDUAL IS USED 9
MAXIMUM EQUILIBRIUM ITERATIONS ALLOWED 16
EQUILIBRIUM ITERATION COUNT FOR CUT-BACK IN NEXT INCREMENT 10
MAXIMUM EQUILIB. ITERS IN TWO INCREMENTS FOR TIME INCREMENT INCREASE 4
MAXIMUM ITERATIONS FOR SEVERE DISCONTINUITIES 12
MAXIMUM CUT-BACKS ALLOWED IN AN INCREMENT 5
MAXIMUM DISCON. ITERS IN TWO INCREMENTS FOR TIME INCREMENT INCREASE 6
CUT-BACK FACTOR AFTER DIVERGENCE 0.2500
CUT-BACK FACTOR FOR TOO SLOW CONVERGENCE 0.5000
CUT-BACK FACTOR AFTER TOO MANY EQUILIBRIUM ITERATIONS 0.7500
CUT-BACK FACTOR AFTER TOO MANY SEVERE DISCONTINUITY ITERATIONS 0.2500
CUT-BACK FACTOR AFTER PROBLEMS IN ELEMENT ASSEMBLY 0.2500
INCREASE FACTOR AFTER TWO INCREMENTS THAT CONVERGE QUICKLY 1.500
MAX. TIME INCREMENT INCREASE FACTOR ALLOWED 1.500
MAX. TIME INCREMENT INCREASE FACTOR ALLOWED (DYNAMICS) 1.250
MAX. TIME INCREMENT INCREASE FACTOR ALLOWED (DIFFUSION) 2.000
MINIMUM TIME INCREMENT RATIO FOR EXTRAPOLATION TO OCCUR 0.1000
MAX. RATIO OF TIME INCREMENT TO STABILITY LIMIT 1.000
FRACTION OF STABILITY LIMIT FOR NEW TIME INCREMENT 0.9500
TIME INCREMENT INCREASE FACTOR BEFORE A TIME POINT 1.000

CONTACT CONTROLS APPLIED TO ALL CONTACT PAIRS:
AUTOMATIC TOLERANCES FOR OVERCLOSURE AND SEPARATION
PRESSURE ARE SUPPRESSED
GLOBAL STABILIZATION CONTROL IS NOT USED
FRICTION IS INCLUDED IN INCREMENT THAT THE CONTACT POINT CLOSES
RELATIVE PENETRATION TOLERANCE FOR AUGMENTED LAGRANGE CONTACT:
FINITE-SLIDING SURFACE-TO-SURFACE 5.000E-02
OTHERWISE 1.000E-03

PRINT OF INCREMENT NUMBER, TIME, ETC., EVERY 1 INCREMENTS

THE MAXIMUM NUMBER OF INCREMENTS IN THIS STEP IS 200

LARGE DISPLACEMENT THEORY WILL BE USED

LINEAR EXTRAPOLATION WILL BE USED

CHARACTERISTIC ELEMENT LENGTH 2.37

DETAILED OUTPUT OF DIAGNOSTICS TO DATABASE REQUESTED

PRINT OF INCREMENT NUMBER, TIME, ETC., TO THE MESSAGE FILE EVERY 1 INCREMENTS

EQUATIONS ARE BEING REORDERED TO MINIMIZE WAVEFRONT

NUMBER OF CONTACT ELEMENTS WITHOUT NORMAL LM= 13649


COLLECTING MODEL CONSTRAINT INFORMATION FOR OVERCONSTRAINT CHECKS

COLLECTING STEP CONSTRAINT INFORMATION FOR OVERCONSTRAINT CHECKS

***WARNING: EXCESSIVE DISTORTION AT A TOTAL OF 28 INTEGRATION POINTS IN SOLID
(CONTINUUM) ELEMENTS


***NOTE: ELEMENTS ARE DISTORTING EXCESSIVELY. CONVERGENCE IS JUDGED UNLIKELY.


***ERROR: TOO MANY ATTEMPTS MADE FOR THIS INCREMENT

ANALYSIS SUMMARY:
TOTAL OF 1 INCREMENTS
5 CUTBACKS IN AUTOMATIC INCREMENTATION
5 ITERATIONS INCLUDING CONTACT ITERATIONS IF PRESENT
5 PASSES THROUGH THE EQUATION SOLVER OF WHICH
5 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
4 WARNING MESSAGES DURING USER INPUT PROCESSING
5 WARNING MESSAGES DURING ANALYSIS
0 ANALYSIS WARNINGS ARE NUMERICAL PROBLEM MESSAGES
0 ANALYSIS WARNINGS ARE NEGATIVE EIGENVALUE MESSAGES
1 ERROR MESSAGES

***System matrix has so many negative eigenvalues values***

and abaqus aborts after these.

Pls guide....

 

[xerf]

- Check the boundary conditions to restrain rigid body motion

AUTOMATIC TIME CONTROL WITH -
A SUGGESTED INITIAL TIME INCREMENT OF 1.00
AND A TOTAL TIME PERIOD OF 1.00
THE MINIMUM TIME INCREMENT ALLOWED IS 1.000E-05
THE MAXIMUM TIME INCREMENT ALLOWED IS 1.00

The settings for automatic time incremetantion if you have contact should have smaller values:
you can try:
- initial time increment ~ 0.005
- mininimum ~1.e-15
- maximum ~0.1

To select the inner geometric entities you have to use the Selection "Options" Toolbar when you are prompted to select a region. Using Selection Options you can restrict the selection to the inner entities.

For details see:
ABAQUS/CAE User's Manual -> 6.3 Using the selection options

If you have multiple parts instances you can use :
CAE->Main menu->View->Assembly Display Options->Instance Tab , to show/hide part instances.