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Helo every one i have a sheet me

Helo every one i have a sheet me

(OP)
Helo every one
i have a sheet metal plate meshed with shell elements.
When i solve with proper boundaty conditions ,
its getting solved and giving all the displacements and rotations zero.
can any one please tell what the problem is exactly.

RE: Helo every one i have a sheet me

You have an error in your model.

Thats the best I can do with the information you have given.

RE: Helo every one i have a sheet me

Hi
I can't find any constraints in the dat-file.

Thomas

RE: Helo every one i have a sheet me

you cannot run a static analysis (sol 101) without constraints (unless you use param,bailout,-1)

solution: constrain your model

RE: Helo every one i have a sheet me

(OP)
sorry ,
By mistake i have exported a wrong .dat file.
Suppose if there are no constraints the model should not start solving , the model setup check will give an error saying , there are n constraints in the model.
in my case i have given proper boundary conditions (fixed on one end ).
Still it is giving excessive pivot ratios error as in the .fo6 file.(please open and look in to .fo6 file)
At a single node , few degrees of freedom are more than 1e7 and few are negative .
Any one please help me in this.

RE: Helo every one i have a sheet me

can you export the correct .dat file and post here?

RE: Helo every one i have a sheet me

Hi
Try by running Normal Modes and see if there is any rigid body modes.

Thomas

RE: Helo every one i have a sheet me

(OP)
Hi
Thanks for the response
I have run normal modes analysis also.No extra rigid body motions found.
The problem is I am getting excessive pivot ratios at a particular node as follow.


GRID POINT ID DEGREE OF FREEDOM MATRIX/FACTOR DIAGONAL RATIO MATRIX DIAGONAL

378 T1 4.13818E+13 2.60162E+08
378 T2 3.84776E+14 1.08938E+08
378 T3 -3.53059E+14 3.08177E+08
378 R1 -6.08396E+11 6.87523E+08
378 R3 -1.79726E+11 6.07121E+08


If the excessive pivot ratios are all positive , I can get the solution by changing the MAXRATIO value in the parameters to the maximum value in the above list. In my case its a combination of positive and negative values what to do in this case.
And i want to know what may be the reasons behind getting this error( In my model neither rigid elements are there, nor dissimilar elements are sharing a node . ) please help me.

RE: Helo every one i have a sheet me

Why dont you share your input file?

Its almost impossible to determine why there is a problem from your current description.

RE: Helo every one i have a sheet me

What do you mean by "no extra rigid body motions", there should not be any rigid body motions.

In the file you shared there were no constraint defined. It also seems like you are running Nastran bundled with something else. Could that be the source for error?

Thomas

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