Material going foamy then disappearing

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

Hi,

 

so I've run Optistruct on a model of a clevis joint and it essentially doesn't do anything. It's done in iteration 0 and within that, it initially removes some random elements from the model, then makes it look 'foamy' then just does away with the design space alltogether. Any ideas and suggestions would be much appreciated!

 

Thanks!

Josh

 

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2015

    Hi Josh,

     

    Can you change the export options to ALL instead of custom in Analysis>> OptiStruct?

     

    If that doesn't work, please share the .out file.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2015
    Altair Forum User said:

    Hi Josh,

     

    Can you change the export options to ALL instead of custom in Analysis>> OptiStruct?

     

    If that doesn't work, please share the .out file.

    Hi,

     

    I tried, but am getting the same error. I've shared the file to your dropbox.

     

    Thanks for the help!

     

    Edit: The first file I sent you is from a 'messing about' model. I'll send you the .out file of the full model.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2015

    Hi Josh,

     

    can you check if there are free nodes in your model and also check the unit system.

       

    Also, check the element quality. If you are not bothered about element quality, please use Analysis page>> control cards>>PARAM>> CHECKEL>>NO

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2015

    Hi Prakash,

     

    I'll try your suggestions as soon as I can get back into Hypermesh from Hyperview. I've saved my session on a USB stick and now upon opneing it, I can't get back into Hypermesh, only Hyperview. Do you know what I can do to open the model in Hypermesh? I get the error message displayed in the following screenshot:

     

    <?xml version="1.0" encoding="UTF-8"?>post-38979-0-26436700-1439930163_thumb.p

     

    Cheers!

     

    Josh

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2015
    Altair Forum User said:

    Hi Josh,

     

    can you check if there are free nodes in your model and also check the unit system.

       

    Also, check the element quality. If you are not bothered about element quality, please use Analysis page>> control cards>>PARAM>> CHECKEL>>NO

     

    I still haven't managed to go back into hypermesh. : / If I save the file and reopen it, does that mean I can't go back into Hypermesh anymore?

     

    Josh

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2015

    Hi Josh,

     

    Have you tried to change the client selector to HyperMesh?

     

    Please try the below:

    Close HyperWorks application(s) and Please delete setting files on your machine and try again. Follow the link below on how to delete setting files:

     

    http://forum.altairh...iles/?hl=delete

     

    <?xml version="1.0" encoding="UTF-8"?>post-7616-0-23811200-1425890772_thumb.jp

     

    Also, delete .Altair folder in temporary directory. Go to Run and type

     

    in %Temp% and click OK.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2015

    Hi,

     

    I've been trying the client selector, but that's when I get the 'Hyperworks doesn't support multiple instances' error. It just won't load up in hypermesh. Not even after deleting the files you told me to. Although, there was a file I couldn't find. It was the 'hmsettings.td' file. Do you know whether it could be somewhere else?

     

    Thanks again!

     

    Josh

     

    Edit: I've managed to manually open the hm file realising that must stand for HyperMesh and it worked!

     

    So regarding the unit system, I've paid close attention to keeping it uniform all the way. I have also checked for free nodes via Tool>Check elems>1-D> and went through all of the options. 0 free nodes and 0 double dependents and 0 rigid loops. If by element quality you mean checking in 3-D, I have gone through all the options and the highest failure is in length with 36% second highest are 'tet collapse' and 'vol skew' with 1% each. I think it's a relatively good mesh, so I'm happy to proceed with it. 

    So then I've gone through control cards>>PARAM>> CHECKEL>>NO and run the analysis again.

     

    I still get the exact same results. It's as if the load isn't transfered into the design space. As if HyperWorks isn't simulating any loads going through the design space, hence why it simply removes all the material there. Can it be that the bolt holes - the non design space - somehow isn't connected to the design space and that's why the loads aren't transfered? Or that the non design space somehow has limited degrees of freedom and it just doesn't let any loads through to the design space? I'm absolutely baffled stil...

     

    Thanks a lot for your help! I'm really stranded, so it's much appreciated!

     

    Josh

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2015

    Hi Josh,

     

    is it possible to share the model file?

     

    If yes, please use the dropbox link in my signature below to share the model.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2015
    Altair Forum User said:

    Hi Josh,

     

    is it possible to share the model file?

     

    If yes, please use the dropbox link in my signature below to share the model.

     

    Hi,

     

    I've uploaded the files. Thanks for checking it out!

     

    Josh

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2015

    Hi Josh,

     

    I think the error is because of the constraints.

     

    For instance, DOF 3 is free and a force is acting in the same direction. That means the node keeps on displacement (zero stiffness)

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2015
    Altair Forum User said:

    Hi Josh,

     

    I think the error is because of the constraints.

     

    For instance, DOF 3 is free and a force is acting in the same direction. That means the node keeps on displacement (zero stiffness)

     

    Hi Prakash,

     

    Indeed, I had to put constraints on the rigids as well. I thought just disabling the DOFs when creating them is enough, but have now realised I have to add extra constraints to them for the simulation to run properly! Thank you for your help! It's been a tough problem, with a really simple solution, so I probably will be back with questions soon again.

     

    Josh

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2015

    No Problem, Josh. image/emoticons/default_smile.png' alt=':)' srcset='/emoticons/smile@2x.png 2x' width='20' height='20'>

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