Nonlinear material input 1

[balu25]

Hello all,
I have a problem with defining nonlinearity to a material. first i have defined
MP, EX, 1, 206000e6
MP, PRXY, 1, 0.3
MP, DENS, 1, 7850
for steel, and then i input and
TB,KINH,1,1,8 ! Activate a data table
TBTEMP,
TBPT,,0.00 , 0.0 ! Strain = 0.00, Stress = 0.000
TBPT,,0.0029 , 320.7e6 ! Strain = 0.0029, Stress = 320.7
TBPT,,0.0092 , 350.6e6
TBPT,,0.0356 , 381.9e6
TBPT,,0.1006 , 411.9e6
TBPT,,0.2056 , 426.1e6
TBPT,,0.2518 , 420.2e6
TBPT,,0.2812 , 387.0e6
TBPT,,0.2975 , 331.6e6
when i start the solution it comes with this error:
*** ERROR *** CP = 23.516 TIME= 16:21:25
For material 1 at temperature 0, the initial slope of the stress-strain
curve based on the TB,KINH table ( 1.105862069E+11 ) is less than EX (
2.06E+11 ).

I tried not to define the EX, and the it says that EX is not defined...
If anyone have an idea how can i fix this i'll be very grateful.
Thanks

 

[ansysfreak]

Hi

For the first stress strain you need to add values that
Ex=Stress/Strain =206000e6

Ex=320,7e6/0.0029 = 110586e6 This can't be smaller then 20600e6
So change the stress/strain values.

Garry

 

[deveng100]

This depends on what is accurate
I mean if you think that Youngs Modulus is accurately measured
Keep E=206000e6
and modify your first yield point by
206000e6 x 0.0029 = 597.4 which is much more than the value you have fed..i.e 320.7
I have strong feeling your plastic data is wrong or say incompatible with youngs modulus
I feel that most likely the strain value is wrong ,
Or may be you have got plastic values for different material
PLease check your data once again ..for analysis sake
If data is right then see which is more accurate
If modulus is right you have to modify first yield value
If you have confidence on Plastic data modify the youngs modulus as stress/strain for first point i.e. 1.105862069E+11
Now can you let us know the material so we can judge the rough value of E
Bythe way ansys can not solve without value of E, any FE solver can not
Thanks,
Dev

 

[Struct71]

Balu,

Solution is very simple.
Your material table starts when material goes plastic.
So remove first line of table and replace with a value
ON your elastic line.

TBPT,,0.00 , 0.0 !< Remove this line
TBPT,,0.0014563 , 300 !< Replace with this


(note 0.0014563 = 300e6/206e9)

Regards,

 

[balu25]

Thanks eelco71,
I've done something like it but not exactly...when i define EX, I use the value of 320.7e/0.0029.
And its working now
But after some thinking, It looks like your decision is better...may be I'll do it
Thanks again!!!

 

[deveng100]

BY this you assume that
Your plastic data was incorrect