Problem with restart LS-DYNA & PolyUMod
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Hello,I am solving the problem of deformation of an energy-absorbing device for a railway car in two stages:1st stage - static compression and a long period of relaxation2nd stage - cargo dropfor the first stage, you need to use an implicit solverfor the second stage, you need to use an explicit solverI tried to use the LS-DYNA program (Revision: R13.0-365-gf8a97bda2a) and the external library of materials PolyUMod.This problem was solved only by using an implicit solver for the entire problem.But this method turned out to be unprofitable due to the long solution time.I tried to use a "full restart", but it turned out that when the model uses the external library of materials PolyUMod, LS-DYNA cannot use the results obtained at the first step for the second step (restart).LS-DYNA reads the solution results from the first step, but then they are "zeroed out".
*** I use EFG formulationMaybe someone could find a way to solve similar problems?*** I also tried to solve this problem using the material model 318, implemented in the LS-DYNA program (Revision: R14.1.1-4-gaf1eb871e8 | AnLicVer: 2024 R2 (20240501+dl-65-gb272478), but unfortunately I could not solve even the first stage of this problem.It is very likely that the implemented material model 318 has some "disadvantages"...Regards Valery
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I also tried to use IMFLAG in CONTROL IMPLICIT GENERAL to switch the solver in ls-dyna.
To my deep regret, I was not able to successfully use this way of solving the problem.
Below is the error message and the file for this problem
Maybe there are errors in this model
https://drive.google.com/file/d/1bZzXNf7NOmcYYPBtF5iGxSeKR2y_AcDY/view?usp=drive_link
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Dear Dennis,
I have allowed your request for google drive access.
Your suspicion about incorrect values of constants for the material model used is unlikely, since I have performed several test simulations using these constants and the results of the numerical simulations coincided well with the results of the natural experiments.
Thank you very much for your link to the video.
Additionally, I would like to ask another questions regarding the output of calculation results after the explicit solver has started to be used:
switching from implicit set this curve, from time 1 second
I set the curve for output 8
but in the process of solving it, I receive the following information:
Despite the messages about solving the problem using an explicit solver, the recording of calculation results after 1 second does not occur.
I cannot understand
- Why does the information output occur with an interval of (approximately) 0.0009 seconds,
if I ordered the output with a much smaller step – 1E-5 seconds – see curve 8Based on the recorded calculation results, it can be assumed that
at the stage of using the explicit solver, LS-DYNA records the results according to curve 8,
and after starting to use the explicit solver, LS-DYNA does not record the results according to curve 8 -
at the moment of switching solvers – 1 second, in my model the following occurs:
deactivation of the rigid body movement limitation
activation of the initial velocity of the rigid body
activation of one pair of contacts
in the published videos, the authors “balance/play” with combinations of specified time values 0.999999/1/1.000001
probably based on their own understanding of the algorithms used and personal understanding of each specific task.
I couldn't find a clear/obvious "answer" to this question in the documentation
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Valerym, I suspect the d3plot load curve issue is related to the value of IOOPT parameter of the database_binary_d3plot. In the k file you sent, it's set to default but maybe try setting it to 2 and see if it works as intended. Just a thought, I've not tested it.
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Good evening colleagues,
the situation with the output of results is becoming clearer.I had this set for outputting results
Time Fy 0.00E+00 0.00E+00 6.64E-02 0.00E+00 1.66E-01 0.00E+00 2.26E-01 0.00E+00 2.86E-01 0.00E+00 3.46E-01 0.00E+00 4.06E-01 0.00E+00 4.66E-01 0.00E+00 5.26E-01 0.00E+00 5.86E-01 0.00E+00 6.46E-01 0.00E+00 7.06E-01 0.00E+00 7.66E-01 0.00E+00 8.26E-01 0.00E+00 8.86E-01 0.00E+00 9.46E-01 0.00E+00 1.00E+00 0.00E+00 1.02E+00 1.57E+04 1.02E+00 1.47E+04 1.02E+00 1.52E+04 1.02E+00 1.48E+04 1.02E+00 1.52E+04 1.02E+00 1.56E+04 1.02E+00 1.55E+04 1.02E+00 1.49E+04 1.02E+00 1.61E+04 1.02E+00 1.57E+04 1.02E+00 1.54E+04 1.02E+00 1.55E+04 1.02E+00 1.54E+04 1.02E+00 1.52E+04 1.02E+00 1.53E+04 1.02E+00 1.56E+04 1.02E+00 1.51E+04 1.02E+00 1.54E+04 1.02E+00 1.55E+04 1.02E+00 1.60E+04 1.02E+00 1.68E+04 1.02E+00 5.26E+04 1.02E+00 1.62E+04 1.02E+00 1.79E+04 1.02E+00 1.73E+04 1.02E+00 1.75E+04 1.02E+00 1.75E+04 1.02E+00 1.70E+04 1.02E+00 1.70E+04 1.02E+00 1.74E+04 1.02E+00 1.72E+04 1.02E+00 1.75E+04 1.02E+00 1.75E+04 1.02E+00 1.76E+04 1.02E+00 1.75E+04 1.02E+00 1.77E+04 1.02E+00 1.76E+04 1.02E+00 1.79E+04 1.02E+00 1.84E+04 1.02E+00 1.81E+04 1.02E+00 2.17E+04 1.02E+00 1.93E+04 1.02E+00 1.94E+04 1.02E+00 1.84E+04 1.02E+00 1.94E+04 1.03E+00 1.86E+04 1.03E+00 1.96E+04 1.03E+00 1.90E+04 1.03E+00 1.93E+04 1.03E+00 1.89E+04 1.03E+00 1.89E+04 1.03E+00 1.89E+04 1.03E+00 1.90E+04 1.03E+00 1.91E+04 1.03E+00 5.72E+04 1.03E+00 1.89E+04 1.03E+00 1.97E+04 1.03E+00 1.99E+04 1.03E+00 2.03E+04 1.03E+00 1.96E+04 1.03E+00 1.97E+04 1.03E+00 1.97E+04 1.03E+00 1.98E+04 1.03E+00 1.96E+04 1.03E+00 1.97E+04 1.03E+00 1.97E+04 this is a record of results
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this is a link to this model
https://drive.google.com/file/d/1SNBO_8Yf2G7Ip2OvjYw4PcdYTsWCEqmA/view?usp=drive_link
this is a graph of the steps of recording the results from the time of the solution
see the first step from 1 to 1.2
it turns out that the step does not change instantly, but according to some law ???
I thought that by asking this:
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