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A new and improved rigid hybrid III dummy is available in beta version. If you are interested in beta testing of this dummy, please contact Sarba (sarba at lstc dot com) for more information. The dummy is provided at no charge if you already have an existing license of LS-DYNA.

  • ranjith says:

    May be after couple of weeks LSTC will release the dummies to public domain.
    Really looking forward to this release now 🙂

    cheers
    ranjith

  • amir says:

    Hi Suri,

    I took a look to the dummie, the *PART_INERTIA still inside the dummie and have to be updated when you set up a model with initial velocity different from 0. That means you have to change the VTX card in 15 positions everytime you change the pulse from frontcrash to rearcrash or what else and this is not easy due to the fact that a lot of people will forget to update it. Could you please talk to the developpers to setup this point as parameter so if you change the velocity you do it one time and put a comment on the first line of the deck to remember the people.

    Thanks a lot.
    Regards
    Amir

  • Suri Bala says:

    Amir,

    I am told that the PART_INERTIAS are defined using node id (for c.g) and the properties are defined using a local coordinate system that is defined using node ids. Both of these should be updated as its positions are updated.

    Can you elaborate how it needs to be updated ?

    Suri

  • ranjith says:

    hi amir,

    I have used the same model for forward and rearward impacts. Till now i have never felt the need for updating the dummy model for switching between the runs. Could you explain more on this? I need to know whether im ignoring something here.

    thanks
    ranjith

  • amir says:

    Hi Ranjith,

    Let say you have a frontcrash with 15m/s as initial velocity and than you decelerate over the pulse, in this case you have to put the value VTX at each part inertia to 15m/s.

    Now you want to use the same structure (seat) with the same dummy but for rearcrash and there you have -8m/s as initial velocity value, so you have to update the VTX again to -8m/s. Since if you take the previous one with 15m/s you have a relative displacement between seat and dummy.

    In addition as I´ve seen in the card of *INITIAL_VELOCITY you can overwrite the *PART_INERTIA velocity in different ways this is ok.
    In using *INITIAL_VELOCITY_GENERATION -I usually use- it is not possible to overwrite.

    More details in the next mail addressed to Suri.

    Regards
    Amir

  • amir says:

    Hi Suri,

    here an original card from the beta model:

    *PART_INERTIA
    $TITLE
    PSOLID : 1 CHEXA :HEAD_SKL
    $ PID SECID MID EOSID HGID GRAV ADOPT TMID
    10 10 10
    $ XC YC ZC TM IRCS NODEID
    118.90000 0.000 671.09998 4.402900 1 10101
    $ IXX IXY IXZ IYY IYZ IZZ
    19840.000 0.000 2973.0000 24030.000 0.000 18130.000
    $ VTX VTY VTZ VRX VRY VRZ
    0.000 0.000 0.000 0.000 0.000 0.000
    $ XL YL ZL XLIP YLIP ZLIP CID
    0.000 0.000 0.000 0.000 0.000 0.000 51

    When I have initial velocity of 64km/h –> 17777.77778mm/s in MPa [mm, s, t], I have to take ist as followed:

    *PART_INERTIA
    $TITLE
    PSOLID : 1 CHEXA :HEAD_SKL
    $ PID SECID MID EOSID HGID GRAV ADOPT TMID
    10 10 10
    $ XC YC ZC TM IRCS NODEID
    118.90000 0.000 671.09998 4.402900 1 10101
    $ IXX IXY IXZ IYY IYZ IZZ
    19840.000 0.000 2973.0000 24030.000 0.000 18130.000
    $ VTX VTY VTZ VRX VRY VRZ
    17777.7778 0.000 0.000 0.000 0.000 0.000
    $ XL YL ZL XLIP YLIP ZLIP CID
    0.000 0.000 0.000 0.000 0.000 0.000 51

    Am I right?

    There are 15 cards in total like the above one, and I have to update them all as well.

    The Idea is:

    $——————————————————————————-
    *Parameter
    r VTX0 17777.778
    $——————————————————————————-
    *PART_INERTIA
    $TITLE
    PSOLID : 1 CHEXA :HEAD_SKL
    $ PID SECID MID EOSID HGID GRAV ADOPT TMID
    10 10 10
    $ XC YC ZC TM IRCS NODEID
    118.90000 0.000 671.09998 4.402900 1 10101
    $ IXX IXY IXZ IYY IYZ IZZ
    19840.000 0.000 2973.0000 24030.000 0.000 18130.000
    $ VTX VTY VTZ VRX VRY VRZ
    &VTX0 0.000 0.000 0.000 0.000 0.000
    $ XL YL ZL XLIP YLIP ZLIP CID
    0.000 0.000 0.000 0.000 0.000 0.000 51
    $——————————————————————————-
    and the other 14 cards in the same manner.

    You only update one time.

    Sorry for the long text, I hope it is now clear.

    Regards
    Amir

  • Suri Bala says:

    Amir,

    Yes that seems to be the case to update the initial velocity for rigid bodies with PART_INERTIA defined. *PARAMETER seems like a nice option and also a node set of the dummy could be another to use INITIAL_VELOCITY along with IRIGID.

    I will pass this information to Sarba to see if we can do this.

    Suri

  • ranjith says:

    Hi amir,

    I understand the problem now. This is the case only when you are using an initial velocity for the model. Apologies for not reading your first blog well.
    Now when you are simulating a frontal crash the way sled tests are done (sled pulled backward using the same acceleration time history got from a full car crash) you dont need an initial velocity, you start from accelaration zero. Thats why i got confused.
    Correct me if im going wrong here.

    cheers
    ranjith

  • Amir says:

    Hi Ranjith,

    you are right. If you have a catapult all initial velocities of the system are 0.

    If a sledtest or a full car crash has to be done, than you need initial velocity to put kinetic energy in the system.

    Regards
    Amir

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