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  1. vorwald

    Is Propeller Spiraling Slipstream a myth or provable fact?

    Sir There is a section in Helicopter Theory, Johnson, pp 40, that deals with the equations to calculate the swirl in the wake behind a rotor. I believe with minor adjustments, it would apply to a propeller. Most of the swirl is due to lift induced torque, the drag induced torque appears to be...
  2. vorwald

    Simulating Landing Accelerations in NASTRAN for Fatigue

    I'll try to restate the procedure above. You can solve the basic m xddt + c xdt k x = F*dirac(t-t0), for a set of modes, like five or 7. Here, x, is the modal dof. So, for each increment in time, try to guess the frequency from looking at the landing data, which appears to consist of several...
  3. vorwald

    Simulating Landing Accelerations in NASTRAN for Fatigue

    I have carrier landing acceleation data of a pod, and have created a NASTRAN model of the pod. I would like to a) represent the landing accel data in NASTRAN for fatigue analysis b) evaluate the landing accel data vs airspeed to identify trends for extending to other landing speeds. So...
  4. vorwald

    S99 Properties

    Can someone provide me with S99 (C 0.36/0.44 Si 0.10/0.35 Mn 0.45/0.70 Cr 0.50/0.80 Mo 0.45/0.65 Ni 2.30/2.80) fatigue properties, preferable S-N.
  5. vorwald

    newbie: Exterior / cross sect drgs frm assbly

    OK, I took a week of CATIA V training a while back (maybe six years). And I know I have a workbook somewhere, but .... I need to generate dimensioned drawings of assemblies built up from v4.2 models. I need both exterior and cross section views. Can someone give me enough detailed steps so I...
  6. vorwald

    Von Mises Vs Max Principle

    From memory, I believe Tsi-Wu indicates failure prior to max strain, see NASTRAN theory regarding margin of safety. So that is part of the issue. And, of course, we are talking about limina strains, not laminate strains. The main problem I have is lack of coupon data for the allowable off...
  7. vorwald

    Matrix problem in Matlab

    Rows or columns of a matrix can be deleted by setting the elements equal to the empty matrix i.e. % Make a simple matrix a=rand(3,5) % Copy matrix and then display and remove the second row b = a; b(2,:) b(2,:) = [] % Copy matrix and then remove the display and third and fourth columns c =...
  8. vorwald

    Von Mises Vs Max Principle

    From memory, I believe that in the NASTRAN theory manual there is a discussion of failure criteria (or margin of safety) that illustrates the different criteria on a stress plot. I'm too lazy to walk upstairs to check the manuals right now. Similar informat can be found with a google search...
  9. vorwald

    Evaluation Copy of CATIA v5

    How can I obtain an evaluation copy of CATIA v5 for viewing / creating dimensioned drawings of v4.2 parts / assemblies
  10. vorwald

    CATIA v4.2 to IGES Conversion

    The software WiseVIEW sucessfully reads my CATIA models and outputs an IGES model.
  11. vorwald

    CATIA v4.2 to IGES Conversion

    Either CGR, IGES, or STEP will work. Since CGR is not an option in v4, then IGES or STEP will have to do. I have someone starting to utilize the translation utility in CATIA version 4 to do the conversion. I'm waiting for results from him. In the mean time, I'm trying to find another...
  12. vorwald

    CATIA v4.2 to IGES Conversion

    Either CGR, IGES, or STEP will work. Since CGR is not an option in v4, then IGES or STEP will have to do. I have someone starting to utilize the translation utility in CATIA version 4 to do the conversion. I'm waiting for results from him. In the mean time, I'm trying to find another...
  13. vorwald

    CATIA v4.2 to IGES Conversion

    I'm using v4. Is there a method in v4?
  14. vorwald

    CATIA v4.2 to IGES Conversion

    Can you explian the steps to output cgr format in more detail. I only have a novice understanding of using CATIA v 4. How do I turn the CACHE on, or check if it is on. When it is on, where does the cgr output go?
  15. vorwald

    CATIA v4.2 to IGES Conversion

    Is there a proceedure for converting CATIA v4.2 to IGES or cgr formats? Are there any issues to be careful with?
  16. vorwald

    Limit or Ultimate Load

    Some random thoughts as I skimmed the above material Ultimate stress is when the material fails, not necessarily equal to 1.5 * limit (yield) stress. Limit stress is the end of the linear range, when the material exhibits more than 2% permanent deformation. There are material allowables...
  17. vorwald

    NASTRAN Composite Modeling Test Data

    I don't have a link to the paper. I'd like to accumulate a collection of papers on measured displacements, stress, buckling, and vibration modes of composite structures. The stresses in Baek's paper are the far field, azimuthal and radial stresses around a hole in a laminate. I used the...
  18. vorwald

    NASTRAN Composite Modeling Test Data

    In order to develop confidence in a modeling approach to composites, it is useful to have experimental data available. Particularly if the experimental setup can be simulated in NASTRAN, and the measured results predicted. One experiment that I've used to demonstrate NASTRAN's ability to...
  19. vorwald

    Honey comb modeling

    Non planar surfaces are approximated as small planes. The important thing is to make sure the material direction is correct. In FEMAP, read the help section for "Modify, Update Elements, Material Angle." You can view the material angle using view/options; labels, entities and colors; element...
  20. vorwald

    assembly

    In FEMAP, there is automatic generation of "tie" elements (rigid or beam) under mesh/connection. I've used closest link with some success, but you have to review the connected nodes.

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