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Elvis

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Posts posted by Elvis


  1. 4 minutes ago, Prakash Pagadala said:

    Hi Elvis,

     

    I think the way SPCF is calculated is dependent on stiffness and enforced value and SPCF is directly proportional to both. This is why you are seeing such a change in results,

     

    Anyways, I am going to dig a bit deeper into theory to confirm this and I will also check with expect before I come back to you with a proper explanation. 

     

    Hi Prakash,

     

    ok thanks. I am looking forward to your information.


  2. I did a simulation with a displacement of 100m also and compared the graphs in one plot. As you can see, the graph history is almost the same, but with different values. Why is the SPC-Force dependent to the total displacement? Does that make sense? 

     

     

     

    compare.jpg.e6605a62312489eeeff4f44efe093b01.jpg


  3. Hey,

     

    I try to simulate a large displacement movement and have a problem. I got two simulations and want to evaluate the SPC-Forces, which are completely different, although the model is the same. The constraint is placed in the middle of the green component and connected to it, with rigids (see Figure). In the first simulation, the total displacement of the green component is 350mm (due to constraint) in x-direction. In the second simulation the total displacement is 50mm. When I evaluate the force-displacement plots and compare them, the results are completely different, which makes no sense. For example, in the first model the force at 50mm displacement is 6,7e+05 N. But for the second model, the force at 50mm is only 8,19e+04 N. But they should be totally the same to my opinion.

     

    Somebody any hints?

     

     

    disp_350mm.thumb.JPG.76e2c9b3937833843a3dd188e76d20e1.JPG

     

    disp_50mm.JPG

     

    Greets

    Elvis


  4. On 31.8.2017 at 9:34 AM, Prakash Pagadala said:

    Hi Elvis,

     

    Is it possible to share the model file and data from the supplier?

     

    You can use the file transfer link in my signature below.

     

    Hey Prakash,

     

    I sent you the model file and the data sheets a few days ago. Did you check it already?


  5. Hallo,

     

    for the validation of my model I tried to simulate a four-point bending test with a sandwich panel. The layers are modeled with MAT1-Material and the core with MAT9ORT. Somehow, the results are not matching to the one on the testing machine of the sandwich part, which I got from a data sheet. The displacement should be about 1,5mm, but I got 18mm. 

     

    I attached my matieral card and a screenshot of the model. The engineering constants were provided from the supplier. They should be right because he sent me screenshots of his simulation, where he has a displacement of about 1mm.

     

     

    Unbenannt.jpg

    a.jpg


  6. 33 minutes ago, Prakash Pagadala said:

    Hi,

     

    Yes when therer are incremental results, it is better to use transient animation. But without NLOUT you did not see right behavior which is strange. 

     

    I am going to put this forward to developers. 

     

    Ok thanks Prakash.

    Another issue. I want to determine the reaction forces at the constraint which is performing the displacement, but it somehow don't show me any results. I activated the GPFORCE button and then tried to show the reaction forces in Hyperview with the option "derived results", that's how I did it in previous tasks. But I do not get any result with this. The model which you sent me ("PinLug.fem") has the same problem. Any hints?


  7. 1 minute ago, Prakash Pagadala said:

    Hi Elvis,

     

    This is strange. Did you see convergence issues with NLOUT?

     

    What about with NLOUT, did you change anything in NLPARM?

     

    No I did not change anything. There were no convergence issues. When I change the animation button to "transient animation" I get the right deformation as well.


  8. 22 hours ago, Prakash Pagadala said:

    Hi Elvis,

     

    Everything looks fine with contacts

    Are there any shell elements in your model?

     

    Please share the model file using the dropbox link. 

     

    Prakash,

     

    I found the mistake. I did not use NLOUT, and when I started the animation I saw this result which I sent you above. Using NLOUT and then switching from Load factor to Load factor in Hyperview is showing me the right deformation, without seperating of the components. This result is satisfying, but I don't understand it. Why is the result dependent of the animation option?

     

     

    aa.JPG


  9. 4 hours ago, Prakash Pagadala said:

    Elvis,

     

    I think the basic formulation used is wrong. We are working on a large strain problem with small strain formulation which is wrong. Using Large displacement method I am able to see results. I can share the h3d file to you through mail.  Since I used NLOUT the run took almost 24hrs :| 

     

    Hey Prakash,

     

    thanks, you really helped me a lot. I didn't know that the function LGDisp is existing. I am working on a updated model which is not so stiff and where the calculation is executed much faster. I used the same settings like you, but i got some strange deformations here. As you can see, the contact is working very well at the beginning, but in the middle of the motion the components are seperating, which should not happen. Do you know what could be wrong?

     

     

    Unbenannt.JPG

    Unbenannt1.JPG

    Unbenannt2.JPG

    Unbenannt3.JPG

    Unbenannt4.JPG


  10. 3 hours ago, Prakash Pagadala said:

    Hi Elvis,

     

    Large displacement worked but did not converge after 99.98% load. So you need to reduce the load by a little bit (say 2-3%) and try again with LGDISP.=1. You can use NLOUT for intermediate timestep results in h3d 

     

    Thank you Prakash, you helped me a lot. But what is the problem with the above mentioned model? The contact is failing here at the beginning already. The deformation is totally unrealistic.


  11. 3 hours ago, Prakash Pagadala said:

    Hi Elvis,

     

    Its been almost 18hrs and the analysis is stil running,.. :wacko:

     

    I used LGDISP this time to check the behavior but the analysis is still ON...

     

    Hey Prakash,

     

    yes I know, I have the same problem too. I updated the model, because I thought it was to stiff maybe, but the contact is working incorrect from the beginning now. I tried to change the SRCHDIS and CLEARANCE Parameters, but don't get good results either. I just want to understand the contact behaviour in Optistruct, but it's totally confusing to me now. Maybe you know what the problem with this model is? I attached the .hm and the .h3d files for you.

    pin_lug_update.hm

    pin_lug_update.h3d


  12. On 25.7.2017 at 10:02 AM, Prakash Pagadala said:

    Even with finite sliding, I see the same result. I am running a large displacement analysis now. Once the results, I will share the same with you. 

     

    Hey Prakash,

     

    any results already? I tried a few things too, but unfortunately unsuccessful.


  13. Hello,

     

    i am simulating a contact (slide) between a pin and a lug. At the beginning of the motion everything is fine, but at the end the pin is penetrating the lug. The pins displacement is implemented with a constraint. I already tried to change master and slave, but it didn't work. I have no idea what to do next, do someone have some hints maybe? I attached a screenshot of my card settings and the movement of the pin.

    card.jpg

    penetration.jpg

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