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  • Users: stressebookllc
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  1. stressebookllc

    Need Opinion on Stress Analysis Procedure for Interior Monument Honeycomb Laminates

    You can learn more about how the sandwich panels are tested and allowables developed here: http://www.stressebook.com/sandwich-panel-long-beam-and-short-beam-tests/ How the flexure stress equation is derived here: http://www.stressebook.com/sandwich-panel-flexure-stress-equation-derivation/...
  2. stressebookllc

    Understanding Principal Stresses

    rickfischer51 hit the nail on the spot. Aerospace Stress Analysis and FEA Courses http://www.stressebook.com Stressing Stresslessly!
  3. stressebookllc

    Pull Away Load on L Bracket Top Leg - Hand Calculation

    Here is the deformed plot. Aerospace Stress Analysis and FEA Courses http://www.stressebook.com Stressing Stresslessly!
  4. stressebookllc

    Pull Away Load on L Bracket Top Leg - Hand Calculation

    I thank you all for your generosity in responding and taking the time, I am really thankful. I agree Greg, preload does make a difference. But the effective stiffness (Huth formulation) is usually employed for fastener shear flexibility of a joint. For tension any load should be fine, if...
  5. stressebookllc

    Pull Away Load on L Bracket Top Leg - Hand Calculation

    If only I had a nickel every time I heard "it has been done like this for years"... I am not disagreeing with all the years f experience here. Basically the conclusion is to ignore the heel toe (Px positve), and the fastener load would be lower than what the idealized FEM is showing. And that...
  6. stressebookllc

    Pull Away Load on L Bracket Top Leg - Hand Calculation

    I have verified the deformation behavior with both scenarios (there is not much to mess up in this model): 1) Rc was NOT constrained vertically (in this case the corner moves down from the undeformed shape), the bottom left edge was constrained vertically producing Rht reaction couple with the...
  7. stressebookllc

    Pull Away Load on L Bracket Top Leg - Hand Calculation

    Thanks Greg, Rx is not a problem. It may look banal but is good for demonstrating FBDs and hand calculations. Shear and tension clips are some of the most common parts used in planes. I guess I don't know yet how to solve this and verify the FEM results. Aerospace Stress Analysis and FEA...
  8. stressebookllc

    Pull Away Load on L Bracket Top Leg - Hand Calculation

    Dear Friends, I have a bracket, a simple L bracket, with a couple of fasteners holding it down at the bottom base leg, and a horizontal pull away load at the top leg. I am trying to figure out the reactions with hand calculations. Two other scenarios are fairly straight forward statically...
  9. stressebookllc

    Shear Stress in Dual Core Honeycomb

    It may be fair to say that the load would split up to the point where the 1z or 2z stiffnesses are the same between the cores, and beyond that point the weaker core would fail and then, the panel is not the same anymore. FE Model could be a good approach, but it would be an idealized bond...
  10. stressebookllc

    How do aerospace manufacturing companies certify their processes with the FAA?

    Thanks SparWeb. I think its starting to make sense now, I was researching this topic a bit and I came across that any reputable aerospace manufacturer would go through the AS9100 certification, which is the certification for quality of the products produced and therefore compliance with the...
  11. stressebookllc

    How do aerospace manufacturing companies certify their processes with the FAA?

    Great comments. From a structures stand point, we typically ensure there is a CPTC from materials allowables, testing and analysis standpoint ensuring compliance with Part 25 regulations. I know a little as a stress guy but not enough from a manufacturing engineering stand point or QA...
  12. stressebookllc

    How do aerospace manufacturing companies certify their processes with the FAA?

    As we all know, the FAA needs approved process specifications for mass produced parts used on multiple aircraft. I wrote a little bit I know about this. Process Specifications are critical for a product's consistent quality, and thus 14 CFR compliance and certification...
  13. stressebookllc

    Check potential energy of elements after FEA?

    In general, you need to do basic hand calculation checks for whether the response makes sense, also use the 'epsilon' value, the strain energy error measure. It needs to be a very small number (usually less than 1.0E-12) The way I like to think of this is that the difference in energy you...
  14. stressebookllc

    Best software to learn?

    It is quite common in many aerospace stress engineering jobs to ask for experience with PATRAN/Nastran for example, its a critical skill set. Aerospace Stress Analysis and FEA Courses http://www.stressebook.com Stressing Stresslessly!
  15. stressebookllc

    Best software to learn?

    I have seen jobs that require experience with certain FEA programs.. Aerospace Stress Analysis and FEA Courses http://www.stressebook.com Stressing Stresslessly!
  16. stressebookllc

    FEA - Theory vs Practice

    Theory is important, but what is your goal in terms of a job? If you want to work as a technical support engineer or an applications engineer at a company that makes FEA software, then absolutely you need to know how the elements are formulated, their important characteristics, solutions types...
  17. stressebookllc

    Fix rotation parts at the axis instead of edge?

    I personally suggest you use an RBE3. You can try to explore the 'UM' option while defining the RBE3, this way you can fix the 'dependent' node of the RBE3, and then chose to constrain 'sensible' independent nodes of the RBE3 along theta of a custom cylindrical coordinate system. You might...
  18. stressebookllc

    Nastran Post-Buckled Analysis of Thin Plates

    I believe there are dedicated diagonal tension elements in NEiNastran. Aerospace Stress Analysis and FEA Courses http://www.stressebook.com Stressing Stresslessly!
  19. stressebookllc

    Best software to learn?

    Personally, I believe you should get real good at modeling, meaning using the proper elements to capture the stiffness and response of the structure, how to interpret the loads along the load path etc. This really has nothing to do with a particular software, all reputable programs essentially...
  20. stressebookllc

    Landing gear attach point composite load

    Is more oxygen better than less oxygen? Yes in that sense I'd think more support points are better to distribute the load, obvious. But at what cost are you making that extra oxygen or spreading the load? That is what you really need to focus on in my humble opinion. Aerospace Stress Analysis...

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