##### Principal Stress Calculator for Shell Elements in DYNAIN File

Recently, there was a request to ouput the principal stresses for each element at lower and upper surfaces of each shell element in DYNAIN file to use in some failure theories. I beleive this feature is a routine output in PamStamp simulations. To enable this, the attached ‘C’ code can be used that reads in a DYNAIN file (valid output from LS-DYNA) to use the stress-tensor and output the principal stresses for each element at lower and upper surfaces.

Principal Stress Calculator (Version 12)

• kevinzeng says:

should line 175 be ps[2] = -((s u)/2) – (b/3*a) – i*(s-u)*sqrt(3)*0.5; ?

• Suri Bala says:

KevnZeng,

Thanks for the correction. The new version (v12) now has the update you pointed out.

Suri Bala

• Nemo says:

Two lines also should Be:
Line 103 : avg_sig[5] = sig[5];
Line 141 : iv[1] = sig[0]*sig[1] sig[0]*sig[2] sig[2]*sig[1]-pow(sig[3],2)-pow(sig[4],2)-pow(sig[5],2);
??

Question1:
Can you comment to the principal result for following data:
1 1 2 0
-9.491E-01-3.809E 05-1.837E 05 2.445E 02 2.020E 04 1.484E 02-2.294E 04 1.732E-02

(Above program give out results:
eid s1 s2 s3
1 -188116.7969 -188120.2656 -188118.4375
1 135118.0469 135114.7344 135117.2344
)
But I doubt it whether I calculate correctly or not.

(My results are much different with yours using a similar method:
PStress= 1.0e 05 *
0.0163
-3.8430
-1.8168
)

Question2:
If there are much difference about Principal Stress between the 5 or 7 integration points, does that mean shell element is not suitable for this simulation, and Solid element is needed?

Thanks.