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Alice

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  1. Hi, Thank you for both your replies. I changed ICoG from 0 to 3 and I constrained only the master node (and not all the slaves nodes of the rigid body) and it works great now. Thank you a lot for the quick help ! Alice
  2. Hello all, I have a rigid body impacting a device. It is a frontal impact and the rigid body is not supposed to turn. However, as I input initial velocity (on master node only), the rigid body behaves on its own during simulation. So I constrained all rigid body nodes in X and Z directions (impact on Y direction). But I get a warning: WARNING ID : 312 ** INCOMPATIBLE KINEMATIC CONDITIONS IN MODEL DESCRIPTION : 2886 INCOMPATIBLE KINEMATIC CONDITIONS IN MODEL 1. I don't think my kinematic conditions are problematic. 2. My simulation works but the rigid body still turns on itself and does not respect the bcs condition input How can I solve this problem ? Thank you in advance, Alice
  3. Hi George, Thank you for this update ! I check it later and come back to you.
  4. Hi George, This enables to begin from zero indeed, thank you ! But still, I stop displacement at time 0.5 ms (see function in my post from april 28 above). Reaction forces should decrease but they keep increasing. How that ?
  5. Hi again, can you give me any support on my issue ? Thank you, Alice
  6. Hi George, I tried this and it works fine, thank you a lot ! What I did : X Y 0 0 1 1 2 1 However, I wonder about Time History Data : At time 0 displacement is zero but reaction forces, which I want to output, are non-zero. How can that be ? Plus, after t=1, reaction forces still increase though displacement stays constant. I don't understand what is going on... Find my request on the attached screenshot
  7. Hi George, Thank you for your reply. I do not see any problems in my imposed displacement input. I tried increasing timestep (from 0.001 to 0.1) but it didn't work either. Then I changed from /IMPL/LINEAR to /IMPL/QSTAT which makes it work though the h3d file shows nothing happening (no displacement). I sent you my starter and engine file through the secure dropbox link. Thank you.
  8. Hi all, I am working on an implicit case. First I applied a load on a group of nodes. Now I apply an imposed displacement. It worked fine for the first one but I get an error in the engine file for the imposed displacement : MESSAGE ID : 79 ** ERROR : RADIOSS IMPLICIT STOPPED DUE TO LOADING DATA ** ISTOP=0 ERROR TERMINATION Here my imposed displacement input: /IMPDISP/551 IMPOSED DISPLACEMENT ON TOP NODES # func_id dir skew_id sens_id grnod_id frame_id icoor 601 Y 803 # x_scale y_scale t_start t_stop 0 -3.000000e-02 0 I see tstop but what is ISTOP ? Thank you in advance, Alice
  9. okay I see, this is not a physical stress so. Thank you! I shared a simplified model in your dropbox. It is not the real component, but is a good representation of what I am working on. Thank you in advance for helping me out on this
  10. Okay thank you for this explanation. I already looked for it in the theory manual and literature but sgma_cut is not explicited there... So is it maximal stress or yield stress ? This is not clear to me.
  11. Hi again, Simulations are running. Meanwhile I was searching a bit more about silicone representation. I wonder about several things: 1. In the example you sent the screenshot of we have : mu1 = 0.002009 mu2 = 1.27E-6 alpha1 = 2 alpha2 = -2 However, in the comments section, it says, (mu1,alpha1) and (mu2,alpha2) should each be "greater than zero" (see picture). How should I understand that if (mu2,alpha2) does not seem greater than zero ? The values I input in my file (see above question) come from literature, tis is why both my alpha_i are positive. 2. what is sigma_cut ?
  12. Hi George, I will try several material parameters, including the example's ones. This was actually my model for creating OGDEN material law. One simulation is already running. I will update you on changes. Thank you, Alice
  13. Hi George, Hi gopal_rathore, Thank you for both of your replys. @George P Johnson : I tried not applying any material/prop card, but then I can't define a part. this was a problem for me when I tried defining the hammer surface for interface modeling. I tried /SURF/SEG but did not succeed. Thank you for your help though. @gopal_rathore : Thanks a lot for reminding me of the mass summary (and inertia) in the 000.out, that is indeed the best way to check, and I didn't think about it. I applied material and property as you said. However I momdeled my hammer with shell, though it is full. So mass is not right from material and geometry only. So what I did is to input a very low density in the material and add a mass in the rigid body, while leaving inertia inputs blank. This gives me the right mass, having already my center of gravity. Thank you a lot for both of your help, I understand rigid bodies a way lot now ! Alice
  14. Hi George, Thanks for your answer Please find attached a video of the simulation. It seems that everything is okay until t=0.75s. Then the hammer goes through without noticing the interface. I don't understand why I should increase thickness ? Shouldn't I decrease it ? My material is the following : /MAT/OGDEN/205 SILICONE # Init.dens 0.000923 # Poisson sigma_cut Bulk_func_ID Fscale M Iform 0.48 0 0 0 0 #N parameters: mu_i 0.0287 0.0286 #Blank Card #N parameters: alpha_i 2 2 #Blank Card It is the typical material used for rubbers. Thank you in advance for your help, Alice vonMises_silicone.avi
  15. Hi all, I model a hammer, impacting a component. To reduce computation time, and as I don't need any information about the hammer's stresses and strains, I want to model it as a Rigid Body. Though, I wonder about inertia and mass input in rigid bodies, as I get the following warning and error : WARNING ID : 542 ** WARNING RIGID BODY INERTIA ERROR ID : 274 ** ERROR IN RIGID BODY DEFINITION (INERTIA) And here my input: /RBODY/402 HAMMER # N_master I_sens I_skew I_spher MASS Grnod_id IKREM I_CoG Surf_id 39178 0 0 805 0 # Jxx Jyy Jzz 1.87779E+06 371038 -1.87779E+06 # Jxy Jyz Jxz 0 0 404038 # Ioptoff 0 If I delete inertia inputs, my computation works fine. However I need mass, because I work with initial velocity and mass is therefore important. So I wonder : - I input material (density) and mesh, so maybe I do not need inertia and mass input OR - maybe I should input MASS in rigid body OR - do what I did but something is still wrong ... Thank you, Alice
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