Time Step
Altair Employeehi
i having problem in time step.
i checked the minimum time step in the model that comes around 1.934e-03.
when i run the model in radioss with out mass scaling it takes the DT= 0.1448E-02.
but usually the minimum time step * 0.9 will be taken in radioss as initial time step, when we calculate that 0.001934 * 0.9 = 0.0017406
what is reason behind this
Answers
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Hi,
check the starter runname_0000.out file for elemental and nodal timesteps. Whichever is higher is multiplied by 0.9 factor.
In your case, the higher is shell elemental timestep 1.6089472919703E-03.
For more details (relevant from 11:30)
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thanks ivan
i tried with time step DT/NODA/CST 0.144E-02 i am having mass error and energy error as follow
RESTART FILES: 2D_SHELL_0001_[0001-0001].rst WRITTEN
NC= 605000 T= 8.7604E+02 DT= 1.4481E-03 ERR=-60.0% DM/M= 3.2230E-02
ELAPSED TIME= 1579.40 s REMAINING TIME= 304910.89 s
NC= 605500 T= 8.7676E+02 DT= 1.4481E-03 ERR=-60.0% DM/M= 3.2230E-02
ELAPSED TIME= 1580.85 s REMAINING TIME= 304938.64 s
NC= 606000 T= 8.7749E+02 DT= 1.4481E-03 ERR=-60.2% DM/M= 3.2230E-02
ELAPSED TIME= 1582.20 s REMAINING TIME= 304945.54 s
NC= 606500 T= 8.7821E+02 DT= 1.4481E-03 ERR=-60.3% DM/M= 3.2230E-02
ELAPSED TIME= 1583.49 s REMAINING TIME= 304941.06 s
NC= 607000 T= 8.7894E+02 DT= 1.4481E-03 ERR=-60.4% DM/M= 3.2230E-02
ELAPSED TIME= 1584.80 s REMAINING TIME= 304941.00 s
NC= 607500 T= 8.7966E+02 DT= 1.4481E-03 ERR=-60.5% DM/M= 3.2230E-02
ELAPSED TIME= 1586.16 s REMAINING TIME= 304950.37 s
ANIMATION FILE: 2D_SHELLA045 WRITTEN
NC= 608000 T= 8.8038E+02 DT= 1.4481E-03 ERR=-60.6% DM/M= 3.2230E-02
ELAPSED TIME= 1587.61 s REMAINING TIME= 304976.63 s
NC= 608500 T= 8.8111E+02 DT= 1.4481E-03 ERR=-60.7% DM/M= 3.2230E-02
ELAPSED TIME= 1588.93 s REMAINING TIME= 304978.07 s
NC= 609000 T= 8.8183E+02 DT= 1.4481E-03 ERR=-60.8% DM/M= 3.2230E-02
ELAPSED TIME= 1590.30 s REMAINING TIME= 304988.53 s0 -
Can you share engine out and time history T01 files?
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please find the files
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It looks like there is some problem with contact after 500 time units. Can you share the h3d file?
As mentioned before, step loading functions are not recommended.
<?xml version="1.0" encoding="UTF-8"?>
<?xml version="1.0" encoding="UTF-8"?>
<?xml version="1.0" encoding="UTF-8"?>
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sorry simulation is not yet completed. i have shared the _0000.rad & _0001.rad file with you please verify with it
this is my loading curve, is this not appropriate
<?xml version="1.0" encoding="UTF-8"?>
<?xml version="1.0" encoding="UTF-8"?>
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Large contact energies relative to total energy can cause large negative Energy Errors because contact energy is not part of the Energy Error equation. If the simulation has friction and a lot of sliding contact, then the large contact energy and resulting energy error can be considered acceptable.
Your model without friction had reasonable energy error.
Step loading functions can cause divergence in implicit or dynamic effects in explicit.
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HI IVAN
thanks can u share me the modified model with ideal time step...
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The input deck is attached.
Note the AMS settings used (0.67 scale factor and 2e-3 timestep) are not ideal. First, run with DT/NODA mass scaling until you get reasonable negative energy without friction (15%) and mass error (2%) throughout the simulation. Then set up the AMS run trying to hit the energy error % of DT/NODA run (as well as stress and displacements).
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