FEAP User Forum
FEAP => Input File Issues => Topic started by: crepes on September 18, 2018, 04:30:45 AM
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Dear all,
What is the trigger for changing the time increment in auto-time command? I have thought it is based on the amount of necessary Newton iterations per timestep. E.g. in
batch
pard
transient newmar
DT,,0.0000001
AUTO, DT, 0.000000001, 0.1
AUTO, TIME, 5, 9, 20
LOOP INFInite
time
loop,, 30
utang,,1
next
plot cont 1,,1
plot jpeg
NEXT
end
the change of time increment is expected to change if there are more than 9 Newton iterations, and it is also expected to to 20 attempts finding a new time increment, but it does not seem like there are actually 20 attempts, c.f.
SOLUTION SUMMARY
----------------
Load Total Solution Time Residual Norm Energy Norm CPU Time
Step Tang+Forms Time Incr. Initial Final Initial Final (Seconds)
--------------------------------------------------------------------------------------
--------------------------------- END OF MESH INPUTS ---------------------------------
1 2 0 1.000E-07 1.58E-07 6.78E-04 3.38E-12 6.90E-10 1.50E-26 0.28
2 2 0 2.585E-07 2.51E-07 1.35E-03 1.02E-11 4.33E-09 1.62E-25 0.52
3 3 0 5.097E-07 3.98E-07 1.34E-03 1.18E-15 6.65E-09 3.85E-33 0.82
[...]
158 4 0 1.297E+01 1.00E-01 1.38E-04 1.60E-13 8.36E-06 1.02E-25 56.90
159 4 0 1.307E+01 1.00E-01 1.39E-04 5.62E-13 8.42E-06 1.65E-24 57.40
160 4 0 1.317E+01 1.00E-01 1.39E-04 7.16E-12 8.51E-06 3.22E-22 57.89
161 5 0 1.327E+01 1.00E-01 1.40E-04 8.00E-16 8.65E-06 1.46E-30 58.44
162 6 0 1.337E+01 1.00E-01 1.42E-04 6.16E-16 8.88E-06 5.68E-31 59.10
163 76 0 1.340E+01 2.51E-02 1.44E-04 3.07E-14 2.39E-06 2.99E-26 62.61
164 37 0 1.341E+01 1.58E-02 1.47E-04 8.37E-16 1.70E-06 3.75E-29 64.36
[...]
When we have a look at load step 162, there is dt = 1.00E-01. Using 20 times the formula for the new time increment following the feap manual,
delta t_new = max( delta t_min, 10^[log(delta t_old) - 0.2 ]
would yield something way smaller than the actual used time increment in load step 163.
Additionally, my Newton-loop does not allow more than 30 iterations, but this seems to be ignored.
Did I maybe do wrong inputs? Or do i have a wrong assumption on how the "attempts for new time increment" work?
Kind regards,
crepes
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Two thoughts:
(1) Can you try changing loop,infinite to something like loop,,100000 (so just a big number)? I am wondering if loop infinite is causing a problem since it was implemented after AUTO was implemented
(2) You should look in the O file to see what AUTO is trying to do. AUTO prints diagnostic information to the output file (as do more of FEAP's commands). One should always look there if one experiences unexpected behavior.
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Thank you very much for your thoughts.
Just a short information on (1):
I tried using a big number and it did not change the behavior here. So loop infinite seems to be implemented correctly concerning this matter.
I will check the other suggestion later.
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Thank you very much for posting your problem. In my case i wrote:
BATCh
prop,,1
dt,,0.0001
AUTO DT 0.00001 0.001
AUTO TIME 5 9 5
loop,,10000
TIME
LOOP augment 10
AUGMent
LOOP newton 50
CONTact CHECk
TANG,,1
NEXT newton
NEXT augment
NEXT
END
The result is the same: The value of time steps is increasing until it reaches DTmax and stayes at that value.
Is there a apparent error in my code? Thank you very much for your help in advance.
With best regards
Andreas Lorenz
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What happens if you move the auto time statement to just before the loop,newton,50?
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Dear FEAP_Admin,
thank you very much for your fast reply. The outcome in O- and L-file is equal,no changes so far.
Andreas Lorenz
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Andreas,
if you use build-in multi field element (e.g. mixed thermo-mechanical in FEAP /IGAFEAP) in FEAP85, What would happen then?
Best,
Yaakov
Dear FEAP_Admin,
thank you very much for your fast reply. The outcome in O- and L-file is equal,no changes so far.
Andreas Lorenz
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In looking at the log file the total iterations is a combination of the augmented and the Newton iterations. The O file should be indicating the Newton loop is converging within the tolerances set??? But feap will still do the augmented loop too. It is unclear how the auto time stepping is working when combined with AUGMenting. Getting a summary of what is happening may help all understand what needs to be improved.