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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. 

Roy Duan

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  1. Hi @Q.Nguyen-Dai, Does the face shell elements have the same nodes with solid elements? The material of the shell elements is the same as solid, right? Since solid and shell element has different D.O.F, how to understand the collection? Roy
  2. Hi @tinh and @Prakash Pagadala, I defined the pressure load by selecting all shell elements. At first, I have verified the shell normal before and it is in the +Z direction. What's more, no matter the pressure value is set to 0.2 or -0.2, the deformation is the same (all to the positive direction). The attachment is my model file. You can check it. If you find something wrong, please inform me. Thank you. Roy Shell_Model.hm
  3. Hi @tinh, I'd like to thank you for the HyperView help path and discussion about shell model problem. I have checked my shell normal before. The normal is in the positive +Z direction. So I suspect the result. You can check it from the attachment model file. I have tried with HW13 and HW14. Both give wrong result. According to @Prakash Pagadala, he got reasonable result by using HW2017.2 If you find something wrong with my model, please let me know. Thank you. Roy Shell_Model.hm
  4. Hi @Prakash Pagadala, I try to convert the elements to 2nd order. But the results is similar to the first order, and it also differ from Ansys. How to modify integration points? I cannot find the place to define it in hypermesh. Roy
  5. Hi @Prakash Pagadala, I checked the .fem file output by hypermesh. No matter positive or negative pressure value was defined in hypermesh, the pressure is positive in the output .fem file. I think this mistake results in the strange error result. Best Wishes Roy
  6. Hi @Prakash Pagadala I have try my model with HW13 and HW14, the same similar error result were gotten. I found the main reason was that the fem file only support positive value no matter a positive or a negative value was defined in hypermesh. I suspect this may be a neglected mistake in hypermesh. Could you try with other versions to solve the problem to see if similar results will get? Thank you. Best Wishes Roy
  7. Hi @Prakash Pagadala, I think Ansys use SOLID186 element with full integration (SOLID186 is a second order element). How can I do this in OptiStruct?
  8. Hi @Prakash Pagadala Do you get negative Z direction deformation by solving my model without anything modified? Is there any mistake about my defining method?
  9. Hi all, Besides the different results by solving solid model with OptiStruct or Ansys, I also find another problem about shell model in optistruct. The pressure direction was in the negative Z direction, however I found the deformation of the shell model was in the positive direction. Anything wrong? I have uploaded my shell model. Shell_Model.hm
  10. Hi Q.Nguyen-Dai, What do you mean "HEXA20 + Skin"? From the h3d file you uploaded, it seem that only shell elements existed. Best Wishes Roy
  11. Hi tinh, Z1, Z2 and Mid in the layer options means Top, Bottom and Middle surface? I can not find the help document about this hyperview postprocess graphics. Could you show me how to get it? Best Wishes Roy
  12. Hi Prakash, Maybe we can output APDL input file from workbench by using Tools--Write input file. I have output from my model, and please check it in the attachment. From the dat file, the element in workbench solid model is SOLID186 and full integration is used. I think this element type is a very common second order solid elements. Does OptiStruct have this type elements? How to define it? Best Wishes Roy Test.dat
  13. Hi tinh and Prakash, What's the meaning of "Use Corner Data"? If the Global output request is default, which stress output, element stress in the integration points or node stress or average stress? I also have doubts about stress output meaning in HyperView. For shell model, I think maybe top or bottom stress can be output, however it seems this can not be done in the HyperView. Is there any help manual about the meaning of this results options? Best Wishes Roy
  14. Hi Q.Nguyen-Dai, Yes I agree. We are in "approximate word" with FEA. My simple example have theory solutions. You can look for the result in any book or paper about theory of plate. The following link also give the theory solution. (the theory max stress is 154MPa) http://www.roymech.co.uk/Useful_Tables/Mechanics/Plates.html So what's your understanding of the following questions: Why we get so different result from Ansys and OptiStruct with the same model? And why is the saying “At least three elements must be used when simulating thin plate with solid elements”? Thank you Roy
  15. Hi tinh, How do you understand my doubts in the following attachment? Best Wishes Roy Shell Solid Compare results summary.pdf