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Contact Force Output to RCFORC


The ASCII file “RCFORC” contains the incremental forces contributed by contact algorithms. Due to the nature of the contact-impact interactions, the raw output tends to be very noisy and is of little value. To eliminate the inherent noise in the contact force output, LS-DYNA averages the force magnitude over the preceing output interval which results in a smoother and useful time history of the contact forces. The averaging is performed for all values between two output states as shown in the following figure. For more information, please read Remark #5 under the *DATABASE keyword in the LS-DYNA Keyword User’s Manual.

(Click image to enlarge)
Contact Force Averaging

  • lakshya says:

    Dear Suri
    I am doing low velocity impact on C/epoxy composites. I am using Single_eroding surface and force transducer penalty. I am getting force-time history through RCFORCE data. As my units are in GPA, KN, MM , MSec, I am getting very low magnitude of force (.3e-3)where in experimentally I am getting 8 KN (max). Why i am getting very low contact force ? Reply awaited.

    Thanks
    Lakshya

  • Suri Bala says:

    Lakshya,

    It may be due to several reasons but one study you could do is to vary the failure values to see if you are getting closer to the real number. Additional checks could include the verification of the slave segments for the force transducer.

    Thanks,
    Suri

  • JEN says:

    I set up a surface to surface contact for a train track and each of the wheels. The track is sloped (1:150). The rcforc file gives me values about double the weight. Based on my calculations, though, the force should equal approximately the weight (since the slope angle is so small, or 0.382 degrees). What could cause this? How is rcforc calculating the force on the slope? Thanks!

    JEN

  • Apoorva L says:

    Hi Suri,

    Iam facing a problem in a quasi static simulation. Iam getting severe negative internal energy in a solid part ( ELFORM 2 fully integrated SR component).

    I have tried the method of combating negative internal energy in solids by adding damping part stiffness to the part but it didnt work.

    I want to add that i have been using 971 mpp solver version.

    what are the different approaches you would try to eliminate negative internal energy in solid parts.

  • suri bala says:

    Apoorva,

    IGNORE=1 would be my first recommendation.

    Suri

  • Jen says:

    Hi Suri,

    I set up a surface to surface contact for a train track and each of the wheels. The track is sloped (1:150). The rcforc file gives me values about double the weight. Based on my calculations, though, the force should equal approximately the weight (since the slope angle is so small, or 0.382 degrees). What could cause this? How is rcforc calculating the force on the slope? Thanks!

  • Abu says:

    hey Suri,
    I am doing a car crash simulation at low velocity.I am getting negative internal energy in one of my solid part.Could you please give me some idea how avoid getting negative internal energy

  • suman says:

    i am doing a ly-dyna simulation of rigid body impact. how to obtain contact force time history curve?

  • Mohamed says:

    to suman

    to get contact force time history curve you should use the card *database_rcforc to print these forces in the d3plot file, and then load the ASCII file (rcforc) from the LS-PREPOST

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