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Crashphys

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  1. Hi Rahul, Can you please clarify? Each structural element I have has its own property. I have 7 properties I am optimizing for, each with their own stress constraints. The thing is, for 5 of them my stress constraint is equal to some multiple of their thickness, so their stress constraint changes with the design variables. Is it possible to relate a design variable to the stress cosntraints?
  2. Hi, I am doing a size optimization of a sandwich composite for thickness. The thing is, every time you change the thickness the stress constraints change with the design variables. Is there any way to address this issue in the software? For example, my stress constraint in a ply might be 423 MPa, but that stress constraint may drop if the thickness is changed to 300 MPa, so the stress constraint cannot be fixed. Edit2: Also, if possible, how can you adjust stress constraints based on element size/area? Thanks in advance!
  3. Hyperman, The help is greatly appreciated thank you. If my plan is to convert the model back to RADIOSS, which of the two options is recommended? Considering connectors are a HM feature, will they be compatible in both solvers? Also, don't mean to be a pain but if it isn't too much to ask: can you upload a 2017 version of your file? Thanks again
  4. Hi, When running composite optimization, I get a total ply thickness of 3.6 mm, however when I import the FSTOSZ for individual ply size optimization, I get the same exact size as what I started with, with a total of 6 mm laminates. Is there something I am missing in my analysis? CompositeOptimization2.hm
  5. Hi, Please see attached. I want to attach all the beams to the shell elements without equivalence. Thanks TopologyReconstruction.hm
  6. Hi, If you imagine a square plate with beams running through at various directions, you will note not all beams nodes may overlap the nodes of the square shell elements. I am wondering if there is a way to quickly connect all the beam elements to shell elements without having to create an RBE3 for each node. Perhaps an MPC for two components? Thanks in advance.
  7. 1.0e-8g is really, really small and likely what is causing issues though. Realistically, a particle of dust weight about 7.5e-7 g, so whatever your SPH particle is, it is a tenth of the mass of a dust particle. Consider whether you need this dense of an SPH mesh.
  8. Update: recent simulations show it was - as usual - likely my gapmin value. Still concerned about the contact forces being too concentrated in one location. Shouldn't they be distributed? Hi, I ran the simulations over the course of the weekend. I cannot upload them in full, however it didn't seem to go well. I'm not really sure why, however the movement of the particles is a little too "Brownian," and for some reason affecting a lot the roof of the car with minimal contact. I double checked to make sure the particles are not accelerating upwards by accident, and they are not. More concerning, however, is that the contact forces are only registering on certain points along the structure (third .gif). Any suggestions as to what may be wrong? I set up and am in the process of running a new simulation with much less SPH elements, as I tried your suggestion on my coarser model and it is working just fine and relatively accurate. I am not sure what the problem is... Thanks in advance. I realize I've asked for a lot so far and really appreciate the help. Refined_AMS_0002.rad Refined_AMS_0000.out Refined_AMS_0001.out Refined_AMS_0002.out Refined_AMS_0001.rad Refined_AMS_0000.rad
  9. Hi, Thank you for the interesting suggestion - I'm testing it out as we speak. I wanted to try running it for the simple case of ditching from the demos. I split it into two engine files, with the first running for 1 ms and the second running for the remaining 39 seconds. What happens is I get an increase in energy error by 1% when the second run begins. Is there a reason that this happens? I have not applied /KEREL nor /AMS I followed this tutorial: Also, for running with KEREL in one part and AMS in the other, there is /AMS in the starter file. Do I need to make two different starter files for each engine? SPH_MonoDomain_0000.rad SPH_MonoDomain_0001.out SPH_MonoDomain_0001.rad SPH_MonoDomain_0002.out SPH_MonoDomain_0002.rad
  10. Hyperman, Isn't the load calculated as: With a function value of 9.81 and an FSCALE of -1, I should get an acceleration of -9.81 m/s2 down, and similarily I should get 5 m/s2 lateral, no? I was not aware that the settling was necessary however it does make sense that it should. The peak response occurs at 0.175 sec because the gravity initially drops the SPH particles onto the hopper, which I have not been able to fix as of yet. The dropping creates the high load you see at 0.175 seconds, which is not of interest as this is a software limitation and not a realistic load. The main interest is the lateral load on the walls. If the particles do not settle until 0.5 seconds, I must run it for at least that. Regardless, I have found some more computing power I can use and am getting results soon. I will share here once I get them for the sake of learning for other people.
  11. Hi, I ran the solver with the rigid applied, however I found that the time step is rapidly degenerating. My time step is 3.7366041328229E-05 for the SPH according to the output file, and the model begins with a time step of approx 1e-4, which is definitely not consistent. The time step keeps reducing lower and lower, and by the 5th cycle is triple the initial starting time. I realise I drastically increased the number of elements, however this degeneration seems to happen regardless of element size. Anyone have any suggestions? Thanks in advance. Rigid_0000.rad Rigid_0001.rad CoarseRigid_0000.rad CoarseRigid_0001.rad
  12. HI, I'm trying to find anything I can that can reduce simulation time further. DT/NODA/CST is effective, however AMS has proven to be incredibly unstable, and the multi domain technique does not work for my application. Is there any way to perform any other model order reduction?
  13. I ran the attached demo from taken straight from the directory and got the following error: ERROR ID : 629 ** ERROR WITH EIGENPROBLEM DEFINITION AND SPMD CALCULATIONS DESCRIPTION : -- EIG ID : 1 -- EIG TITLE : Eig 1 NUMBER OF NODES FOR EIGENPROBLEMS MUST BE EQUAL TO THE TOTAL NUMBER OF NODES NUMBER OF NODES FOR EIGENPROBLEM 14354 : 24731 TOTAL NUMBER OF NODES : 0 Can someone explain what is wrong? TRUCK_EIG_0000.out TRUCK_EIG_0000.rad TRUCK_EIG_0001.rad
  14. Hi, Thank you very much for your help with this. I'm looking at following this advice as it would be a good way to reduce computation time, but wouldn't making the walls rigid result in highly inaccurate forces? Doesn't the stiffness play a role in determining the forces? Edit: I found that in OptiStruct, you can model as a flexible body as well as a rigid using the Craig Bampton method. Is this possible in RADIOSS as well?
  15. Hi, I found that the best solution might be to extract interface forces and import them to OptiStruct to do either explicit dynamic or a linear static. I have an output request for the contact forces, however I was wondering how I can get the raw data rather than a graph? Edit: I was also wondering if you could specify: is your recommendation to get the interface loads and run OptiStruct EXPDYN? I thought EXPDYN runs already with the ESLMO method? Thanks
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