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    • Rahul Ponginan

      Please click here for a short but important announcement   03/26/17

      Dear Users Our Commercial and Academic users around the world can use these same forums here as before i.e. the Altair Support Forum , Commercial users from India with solver queries can go to the Solver Forum for India Commercial Users , Academic Users from India and AOC India Participants are requested to go to the Forum for India Academic Users and AOC India Participants , We will be tending to all queries in all the forums promptly as before, thank you for your understanding. 


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  1. Hi George, I managed to low the simulation time. The quasi-static test is working. Thanks a lot for your advice and help.
  2. And what if I use a higher velocity? will the results be substantially different from a low velocity compression test?
  3. Hi George, Where can I find those documents? And thanks again for the help.
  4. I spotted an error in the material model. Corrected it and radioss runs now, the problem is that with a time step of 1ms, the mass error is getting to 5e+6. With this time step the calculation requires 2000 seconds to run. If i use an even smaller time step will raise the time to many hours or even more than a day Using a time step of 0.1 ms and reducing the time of the test i could get the calculation process down to 6000s but the mass error is still 1e+4
  5. I have seen many times explained that the time step must be in the order of the time that a sound wave takes to cross an element. In explicit dynamic analysis that works because the crash tests takes about 100 ms to occur. A quasi static test with a speed of 2mm per second takes more than 1 minute so the same time step traduces on a computation time of 14 days. If I try to impose a minimum time step of around 0.1s it is ignored and a time step of 9e-4 is used by radioss. I don't know why. And even if i can impose it, will it be accurate? There's any way to make it implicit so we don't have to worry with the time step? or can radioss perform it as explicit with a high time step and still have accuracy? Adding a control card DT_ELTYPE_KEYWORD_IFLAG it runs for a bigger time step but the error is getting to -95% since the start
  6. Ok I sent via dropbox. Can you check it please?
  7. Yes, i did that but the command is ignored.
  8. the speed must be in the order of 1 or 2 mm per second so the time step must be closer to 0.1s
  9. Hi George, The quasi static analysis must consist in a simulation of a compression test of a structure so I will impose a velocity in the end nodes of the structure and crush it onto a rigid wall. I increased the time step to 0.1 s but since the beginning of the calculation, radioss is using a time step of 9e-4 what makes the expected time raise to close to 300 hours. How can I impose the time step? I am using DT1 and DTIX control cards to impose minimum maximum and initial time step
  10. Hello, I have completed a dynamic crash analysis on hypercrash and wanted to convert it to quasi-static. The dynamic analysis lasts no longer than 100 ms so I can use a low time-step. How should I proceed to be able to use radioss for a 2 minute simulation with a higher time step? Is is possible with explicit analysis in radioss or should I use another software? I changed the velocity to an imposed velocity and I am using no mass in order to make it quasi static. The minimum time step that I am introducing is being ignored when the calculation software starts. Any advice? Thanks in advance.
  11. The connectivity is ok and the rigid body too. I followed that tutorial and I am making a new simulation now but it takes 10 times more time than the old one to run. I am trying to use the exact same material and connections to see if the problem has another source. For that kind of steel and an element characteristic length of 5mm i am using an inicial timestep of 5 as they recommend. But in my calculations it should be closer to 1 if I am not mistaken. It will take an hour to run. I let you know if its working.
  12. Hello, I am making a setup of a simple bumper structure colliding with a rigid wall on HyperCrash. I am using the Johnson-Cook model for the material. The structure is made of a beam with 2 crash boxes attached with spot welds. In the beginning of the test the structure is already vibrating (Capture2) and seems that the boxes are colliding with the beam instead of being attached. Can anyone help me to solve this vibration problem? can it be from the type of connection that I am using? Should I use other? see the print screens and tell me what you think. There are stress concentration close to the spot welds because they are completely rigid elements (Capture3) Another big problem is that the material is not having the desirable behavior. It is aluminum and should bend on crash but is not bending, its fracturing (Capture4)
  13. I have been 3 days with this problem... Thanks a lot. RADIOSS is running. I let you know if I have good results
  14. I have seen other posts with this problem and I have tried to assign card image but I dont know how to do it in HyperCrash
  15. newtest2_0000.out