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

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Roy Duan

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  1. Thank you George. From my test, I got the same acceleration results by using /TH/ACCEL and /TH/NODE. I'm looking forward for your good news about this topic.
  2. Hi George, 1. I have tried with /th/accel to get node acceleration. From the results comparison, the same results were gotten by using /th/accel and /th/node. Check the model and figure below. Test_T02.zip 2. From the radioss theory reference manual, it seems that the displacement is the first solution variable, and then velocity and acceleration are to be derived. This is a little bit different from what you said (you mentioned we calculate the acceleration using acceleration= nodal force / nodal mass and then integrate to get the velocity and the displacement). Which procedure is used in radioss? could you show some validation documents? 3. I don't think I have understood your opinion about the not matching results. how to understand the meaning of "aliasing"? Roy
  3. Hi George, I have tried your idea, however three different results were still gotten by using three different method I mentioned before even though I have output T01 file with very small increment value (1e-9). I think the node information was output every time step since 1e-9 was used for T01 output. I have uploaded my model. So I think the reason about output increment may be not the reason. what's the reason about this question? Test_T01.zip
  4. quasi static test

    Hi George, Is it possible for you to share the PPT documents which showed in the video you mentioned? Or is it possible to download the video? https://altairuniversity.com/learning-library/considerations-about-time-step/ Roy
  5. plot of force for tensile test simulaion

    Hi Pavan, How did you do the tensile test simulation, explicit or implicit method in radioss? How did you do with the long duration solution time? Roy
  6. quasi static test

    Hi George, Could you help me with foam compression test simulation with implicit algorithm in Radioss. I have uploaded my model to the attachment. Thank you. Roy CompressionTest.zip
  7. quasi static test

    I think may be the solution time is a problem. Since the velocity of a quasi static tensile test may be 10mm/min, the total test time may be several minutes. But for a explicit analysis, the time step is very small. How to deal this in the simulation?
  8. Hi all, Based on a drop test simulation, I think we can get one node acceleration by using three ways. First, get acceleration result directly by using Build Plot about Acceleration. Second, get velocity result directly by using Build Plot about Velocity, and then do one derivative to get acceleration. Third, get displacement result directly by using Build Plot about Displacement, and then do double derivative to get acceleration. From my simple test example, I found the acceleration results with the same node by using the above three methods were very different (the z direction acceleration result of node 7085 listed below method 1: -66~56, method 2: -27~27, method 3: -16~19). The result was figured below. So my doubt is why so different acceleration results were gotten by using these three methods? Which method result is correct and can be compared with experiment testing acceleration result by using accelerator in experiment? Roy SimpleDropValidation5_0000.rad SimpleDropValidation5_0001.rad
  9. How to output the correct nodal acceleration in Radioss

    Hi George, It's a very useful example. May be we can do filter by post-processing. By using /ACCEL directly, the software can only do low pass filter I think. Roy
  10. How to output the correct nodal acceleration in Radioss

    Hi George, From the help of Accelerometer /accel, the filter is Butterworth. That is to say the filter is a low pass filter. However, in many data acquisition device, there is high pass filter. How can we do this? Roy
  11. How to output the correct nodal acceleration in Radioss

    Hi George, I have compared the two acceleration results by using Accelerometer sensor (/accel and /th/accel) and node history (/th/node) for the same node. And the result shown that the two results were the same. I have uploaded my model file. Is there any parameters that influence rigidwall force mostly? How to do filter in HyperGraph? TestSensor.zip Roy
  12. How to output the correct nodal acceleration in Radioss

    Hi George, My unit system is kg-mm-ms-GPa. The block of my model is made up of ABS material. Density=1080kg/m3, E=2GPa, u=0.35, yield stress=45MPa, tangent modules=0.02GPa. I think there is no problem in the unit system. For accelerations, is there any difference between the method you mentioned and the method I used in the first post? What's more, how to define the node accelerometer in HyperMesh? Thank you Roy
  13. Hi all, I want to compare the acceleration result of my simulation with that of experiment. So I extract the nodal acceleration from animation result by using Build Plots tool in HyperView (show in the below figure). However, the acceleration is very big comparing to the experiment result. I suspect if this simulation acceleration result could be directly compared with testing acceleration or not. Should I have to do some filtering with the acceleration simulation result? My model is an ABS block drop test. Please see the attachment model file. The model unit system is kg/mm/ms/GPa. The drop height is 50mm and corresponding initial velocity is 0.99m/s. The total mass of the ABS block is about 850 gram. Could you help me how could I get the top center nodal acceleration which can compare with the experiment? Thank you. Roy SimpleDropValidation2_0000.rad SimpleDropValidation2_0001.rad
  14. Hi George, Is there any example about quasi-static implicit example? Thank you. Roy
  15. How to continue analysis when the light goes?

    Hi George, From my test, it seems that the second step you mentioned may be not necessary. That is to say, we can copy the engine file and modify the file extension from _0001.rad to _0002.rad, and then submitte the new engine file _0002.rad. I don't know if this doing correct or not. Roy