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  1. Chris31

    Fuselage structure under pressure

    rb1957, I appreciate all your help. I didn't hold back information on purpose. The stringers do not see this compression for non -pressure cases, which is why I didn't think of this earlier. However, I did mention the high bending moments previously - I just didn't think (or understand) how...
  2. Chris31

    Fuselage structure under pressure

    Thank you ieaz123 - I believe you are exactly right. The fuselage sees area ruling at this location as well, which all contribute to very high bending moments. Thank you for your explanation.
  3. Chris31

    Fuselage structure under pressure

    Thank you all - I've created a simple model to determine what is going on. I created 2 beam elements surrounded by 4 quad (plate) elements. the left side of the beam and skin is fixed and I apply a shear to the right end in order to cause bending of skin/stringer combination. Interesting -...
  4. Chris31

    Fuselage structure under pressure

    rb1957, Please explain - how is the analogy off target. The pressure vessel is "sealed" so if you don't have the empenage there is no difference. The only difference is that the tail won't translate aft as the bulkhead expands aft. aft of the pressure vessel is unpressurized, so there is no...
  5. Chris31

    Fuselage structure under pressure

    could it be that the skin is seeing tension at the skin ML and the NA (where beam forces are reported due to offsets)is in compression due to the high bending moments? ie, the imaginary nodes at the NA move close together due to curvature effects of bending?
  6. Chris31

    Fuselage structure under pressure

    Thank you for the response btrueblook - The fuselage isn't an open tube though, the pressure bulkheads act as plugs - therefore poisson's effect doesn't hold does it? Aft of the pressure bulkhead should exhibit no loads (or minimal) due to pure pressure cases. If you tape a paper empenage to...
  7. Chris31

    Cbeam in tension and Cquad4 in compression?

    Quick question for anyone that has any insight. Fuselage stringer is modelled as a beam and the skin as a plate. The beams have offsets. When I run a pressure case only, the skin goes into tension and the beam goes into compression. Anyone have any ideas as to how this can happen? GPF...
  8. Chris31

    Fuselage structure under pressure

    rb1957, Thanks for the post - The bending freedoms are not released as I am getting high plane1 and 2 bending moments (E+03). I understand what you are saying about stringer bending but will this put the beam into compression? Dan320, Thanks to you as well. As far as the connections, the...
  9. Chris31

    Cbeam in tension and Cquad4 in compression?

    Quick question for anyone that has any insight. Fuselage stringer is modelled as a beam and the skin as a plate. The beams have offsets. When I run a pressure case only, the skin goes into tension and the beam goes into compression. Anyone have any ideas as to how this can happen? GPF...
  10. Chris31

    Fuselage structure under pressure

    Quick question for anyone that has any insight. Fuselage stringer is modelled as a beam and the skin as a plate. The beams have offsets. When I run a pressure case only, the skin goes into tension and the beam goes into compression. Anyone have any ideas as to how this can happen? GPF...
  11. Chris31

    Searching for and returning output from a Nastran .f06 file

    Hi all, Relatively new to matlab - I have a question for everyone and would like to hear other opinions on how to get what I am trying to do if you have better ideas. I would like to write a short script that would search a series of nastran output (f06) files, find a given subcase and...
  12. Chris31

    Using Matlab to extract data from FE output file

    Sorry, The output is NX Nastran Ouput and there are multiple subcases and element types. Thanks for all your help.
  13. Chris31

    Using Matlab to extract data from FE output file

    Can anyone offer suggestions on where to look for the following: I'm trying to write a script that will search through a Finite Element output file and print axial force values for specific element ID numbers. Any help is greatly appreciated. Thanks, Chris
  14. Chris31

    Help using the FIND function

    Sorry, The second to last line should read inx01 = find(X1==bt01); I copied from the wrong part of the script.
  15. Chris31

    Help using the FIND function

    X1=7.5:0.0001:70; Y1=interp1(x_1EF,yfit,X1); plot(X1,Y1,'r'); bt01=(Htotal-2*Rbulb-Tflange)/Ttee; inx01 = find(X0==bt01); Z01=Y0(inx01);
  16. Chris31

    Help using the FIND function

    X1=7.5:0.0001:70; bt01=(Htotal-2*Rbulb-Tflange)/Ttee; % which equals 8.8095 for this case Thanks, Chris
  17. Chris31

    Help using the FIND function

    Hi all, Quick question - I'm tryin to implement the following line of code: inx01=find(X1==bt01); and I get the error ??? Error using ==> find Second argument must be a positive scalar integer. If I replace bt01 with the value it works, but I need to leave this as bt01. Is there a way to...
  18. Chris31

    3d plot help

    Hi all, Most likely a simple problem but none the less...is there a way to plot vectors X and Y such that a grid plate is created and then Z vector is the vertical distribution of "forces" at these X,Y points depicted as cones or bars or something? X,Y and Z are of the same length. Thanks for...
  19. Chris31

    Patran Database - Unix to Windows transfer problems

    Hi all, I am trying to open a .db file in Windows Patran 2005r3 that was created in some older version on a Unix machine. When I try to open it, a message states that the file will need to be converted on the old system before moving it to Windows. I have tried using the p3convert utility and...

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