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Recent content by franc11HD

  1. franc11HD

    Aircraft Ground Flotation Analysis (CBR) S-77-1

    Agreed. ASD only shows the curve. S-77-1 (as easily easy to find!) gives you an equation saying that you can use the curve or the equation to calculate CBR/P for different thicknesses.
  2. franc11HD

    Aircraft Ground Flotation Analysis (CBR) S-77-1

    I understand that. What I meant with the question is that the given equation does not match the given curve which it tries to approxiamte (sorry if it was not clear at the start). So I used the given equation for multiples values of CBR/P from 0.001 to 1.0 (on a log scale) and calculated the...
  3. franc11HD

    Aircraft Ground Flotation Analysis (CBR) S-77-1

    I don't think this particular curve is aircraft specific. I find the same curve in S-77-1 or ASD-TR-70-43 which respectively gives an example for KC-135 and C-131E. So whatever the CBR/P ratio is, T/squareroot (Ac) should be the same whatever the aircraft. But for the sake of the example, we...
  4. franc11HD

    Aircraft Ground Flotation Analysis (CBR) S-77-1

    Hi Everyone. I was wondering if there were anybody familiar with the document S-77-1 Procedures for Development of CBR Design Curves. My question revolve around Figure 19 and equation 47 about the thickness / squareroot of footprint area vs CBR/ Equivalent Pressure. They give the equation 47...
  5. franc11HD

    Catia Analysis and simulation

    Hi, The easiest way I see is to go in shape generative module, extract the the whole surface to create a matching 2d surface. Then with planes, lines or whatever you need to, modified that 2D surface to get the exact surface you want ton apply the load on. Then, go back to Mechanical Design -...
  6. franc11HD

    SOL600 Results

    In the load cases parameter, you can change the incremental time step of marc. For example, if you ask for increments of 10%, Marc should make 10 times steps from 0 to 1 with each time 10% of the load. This is the way of MARC to divide the problem. When there is non-linear behavior, after each...
  7. franc11HD

    Contact analysis with TET10

    What is your Nastran version? Contact on sol 101 is only available with Nastran 2012 of MD Nastran. You need the appropriate Patran as well to be able to write the card properly.
  8. franc11HD

    Edge contact between surfaces

    Contact tolerance is one issue, contact bias could be another one, side of contact (1st vs 2nd, 2nd vs 1st, automatic) could be another one. For 2D contacts, MSC Support told me to use discrete contact and not analytical contact. You can turn on also the segement to segement contact instead of...
  9. franc11HD

    Edge contact between surfaces

    To solve this problem with linear contacts, you first need at least MD Nastran or Nastran 2012 (maybe 2011, I am not sure.) with the equivalent Patran wich has the linear contact enabled. Contact problems are case by cases they do not work all the same way. But basically, Loads/BC's, create...
  10. franc11HD

    CATIA FEM- Error

    A CatPart may be built as multiple part bodies (green gear symbol). If that is the case, GPS always tries to mesh the first part body. If your structure is not in that first partbody, then you need to change it or to assemble all the part bodies into one. Also, by definition, GPS is a 3D...
  11. franc11HD

    CATIA FEM

    A smooth virtual part and a rigid virtual part is respectively like a Nastran RBE3 and RBE2. It is a rigid spider or smooth spider that will link for example the centroid of the surface you selected with all the nodes on that surface. For a rigid connection, it means that the centroid is the...
  12. franc11HD

    Beginner in MSC NASTRAN v4.5

    For your point no2, yes, you do need to assign material properties to your elements. If you haven't done that, I am surprise no error such as elements without properties was displayed. Anyhow, in the same folder where you have you model file (.bdf) you should also have a results file (.f06) and...
  13. franc11HD

    Bolt, rivet modeling with CELAS2 or CELAS1 element??

    Yes, you can use more than one CELAS for the same bolted joint. One per degree of freedom. Or you can use CBUSH elements which allow to define stiffness in all six direction with a simple element.
  14. franc11HD

    Free node

    Arminiusii, I don't know if there is a better way, but This solution works for me though it is not straigth forward: Create a group with all the elements of your model (don't select the nodes, only the elements). In this group go to utilities - Group - Reorganize and check Nodes/FEM. This...
  15. franc11HD

    Issues with 3-2-1 Constraint Method

    Jieve, AS far as the issue with 3-2-1 constraints giving you localized reactions, have you checked the reacting moments? It is usually the moments that creates those localized reactions. Maybe there is one bending moment that is not constraint correctly. As far as your concern about...
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