RUN TERMINATED DUE TO EXCESSIVE PIVOT RATIOS IN MATRIX KLL 4

[042681]

hi all,
i am relatively new to nastran, I use patran to generate the nastran input file.i keep getting this error message

USER FATAL MESSAGE 9050 (SEKRRS)
^^^ RUN TERMINATED DUE TO EXCESSIVE PIVOT RATIOS IN MATRIX KLL.
^^^ USER ACTION: CONSTRAIN MECHANISMS WITH SPCI OR SUPORTI ENTRIES OR SPECIFY PARAM,BAILOUT,-1 TO
CONTINUE THE RUN WITH MECHANISMS


my FEA problem is as follows. its a 2d problem where there are 2 rectangular plates one top of another whose ends are constrained at the extreme ends as a "displacement constraint". 2 forces eual and opposite in direction are applied at the centre of the 2 plates in Y direction.


both plates were meshed using quad 4 "paver" as they were not perfect retangular plates.

a part my bulk data file looks as follows:

BEGIN BULK
PARAM POST 0
PARAM AUTOSPC YES
PARAM COUPMASS 1
PARAM PRTMAXIM YES

$ Loads for Load Case : Default
SPCADD 2 1
LOAD 2 1. 1. 1 1. 3
$ Displacement Constraints of Load Set : disp
SPC1 1 123456 1 2 3 4 5 28
29 30 31 32 55 56 57 58
59 82 83 84 85 86 131 132
133 134 135 158 159 160 161 162
185 186 187 188 189 212 213 214
215 216 217 219 220 221 222 255
SPC1 1 123456 281 THRU 292
SPC1 1 123456 349 350 351 352 353 354
SPC1 1 123456 365 THRU 371
SPC1 1 123456 396 397 398 447 448 449
474 475 476
$ Nodal Forces of Load Set : force_upper
FORCE 1 499 0 15000. 0. -1. 0.
FORCE 1 502 0 15000. 0. -1. 0.
$ Nodal Forces of Load Set : force_lower
FORCE 3 250 0 15000. 0. 1. 0.
FORCE 3 253 0 15000. 0. 1. 0.
$ Referenced Coordinate Frames




if any one could help me with this, thanks in advance

Ashish

 

[caemaniac]

Hello
I think its due to under constraints( i.e u need to provide more constraints).Go for a shell element .
You could get over this problem

 

[caemaniac]

Hello

Go for "bending element" i thnk that could help.

regards

 

[racecareng]

Use the PARAM, BAILOUT, -1 Option to avoid the termination of the solution.With the result you can probably detect, what is wrong with your model, e.g. a lack of constraints.

 

[TakiM]

If your matrix/diagonal ratio is around the order of E+08 or E+09 then you can set that as a maximum which will allow your model to run and still get good results. NASTRAN has a smaller default ratio which wont allow it to run. Right now, your model is "soft" as we here like to call it... Add this line...

PARAM,MAXRATIO,1.0E+09

If that doesnt work, increase the 1.0E+09 to something higher. Hope this helps...

 

[TakiM]

Before you do the above, make SURE you equivalence your model in PATRAN. (Elements...equivalence..) This should solve your problem or reduce the number of failed ratios.