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  1. Lescombes

    FAR 23.572(a)(2) Fail Safe

    Hello everyone, Thanks for your inputs so far. And a nod to SAITAETGrad - the Dan Air 707 accident report is fascinating reading (actually something I only read a couple of months ago myself). I acknowledge it's hard to pick an MS out of the air without knowing the analysis method (FEM with a...
  2. Lescombes

    FAR 23.572(a)(2) Fail Safe

    Hello everyone, In consultation with our NAA, i'm currently undertaking an analysis to see whether a primary structural joint on an aircraft can be shown as fail-safe under FAR 23.572(a)(2). I'm using FAA AC 23-13A as guidance, specifically para 3-10(b): You may also use the analytical...
  3. Lescombes

    Fatigue of Obliquely Loaded Lugs

    Hello everyone, As the title suggests, i'm having a look at some lugs that aren't loaded purely axially. I've come across a reference "Fatigue Testing of Transversely Loaded Aluminium Lugs" by Larsson, N in 1977. It was written at the Aeronautical Research Inst. of Sweden, Stockholm. Structures...
  4. Lescombes

    Induction Bend and Subsequent HT

    Hi metengr, Thank you. From a review of (what I believe to be) an applicable phase diagram I thought that may have been the case. Cheers, Greg
  5. Lescombes

    Induction Bend and Subsequent HT

    Hello learned forum members, I've inherited a process for forming and heat treating some thick walled spring steel tube. The tube is 5160 steel with 0.55-0.65% C and 0.7-0.9% Cr. There is no record of how this process was developed, and it was long before my time at this company. The process...
  6. Lescombes

    Contact Analyses with Displacement Loading

    Hello everyone, I've been having some fun recently developing some test models of bolted lap joints that have included a solid bolt and contact between relevant surfaces; for the purposes of learning i'm leaving friction out of the equation for the time being. So far i've found a way to get the...
  7. Lescombes

    Improper Heat Treatment?

    Hi SparWeb and everyone, Unfortunately the part was statically substantiated by test 'back in the day' however has had a safe life fatigue analysis performed. I have been working on characterising the internal stress in response to various load cases, and whilst a gross overload failure is...
  8. Lescombes

    Variation in Mechanical Properties

    I've just been reviewing the report from our testing service in light of your question. As each sample was a slightly different shape, it appears that yes, unique cross sectional areas have been calculated.
  9. Lescombes

    Variation in Mechanical Properties

    Hello everyone, My company procures 92" lengths of 6061-T6 extruded aluminium. The extrusion is a hollow section with an average wall thickness of about 0.1", give or take. Recently we had cause to perform some mechanical testing on a sample of the part. We took six samples from the hollow...
  10. Lescombes

    Improper Heat Treatment?

    Thank you to everyone for their thoughts. tbuelna, rb1957, VE1BLL and wktaylor - I have been disappointed with the response from my QA/QC department regarding this issue, and I am considering exploring some of the more serious regulatory/legal options that everyone has described. This potential...
  11. Lescombes

    Improper Heat Treatment?

    Hello everyone, *For the purposes of anonymity I am going to be deliberately vague on some details, and I appreciate your understanding in advance.* I work for an aircraft manufacturer, and I have recently discovered that we may not, in my opinion (and I stress the in my opinion bit), have the...
  12. Lescombes

    Von Mises in Hand Calc?

    Thank you to everyone for their input. The VM yield criterion itself is not being questioned, nor how to calculate it - my interest is whether it regularly appears in the typical aircraft hand calcs that many of us are familiar with. My reaction upon first reading was not unlike these: which...
  13. Lescombes

    Von Mises in Hand Calc?

    Hello everyone, I'm contributing a small section to a colleague's report that is showing compliance with structural aspects of FAR 23 for a fixed wing aircraft's control system. The control system is fairly agricultural, i.e. cables, bellcranks, pushrods and the like. One component subject to...
  14. Lescombes

    Overwing Flex Tee

    I've just been reading FAA AD-2016-04-08 which refers to "overwing flex tees" on the B788 as being principal structural elements, the failure of which may reduce the wing's ability to sustain limit load. What's an overwing flex tee? Is it a common feature on BCA wings? Or is it something that's...
  15. Lescombes

    Limit to Point Based Fasteners?

    For those whom may be interested: problem solved. It appears ABAQUS is a little quirky when it comes to self-identifying which features to project the fastener points to. If you leave it to determine affected parts along a projection vector (IIRC the facet by facet method), some may miss out...
  16. Lescombes

    Limit to Point Based Fasteners?

    Hello all, I am creating an assembly in Abaqus V6.10 which consists of 5 3D deformable shell parts connected with point based fasteners. Fasteners are common to either 3, 4 or 5 of the parts and are based on points defined on the extreme part surface. When viewing the connectors created in the...
  17. Lescombes

    Limit of Validity of Structural Idealisation

    rb1957 and SW - thank you. I was hoping for some sort of rule of thumb like the h/6 or 1/3-ish web height provided. The penetration was 2" in diameter. SW and Burner - the penetration was afforded a ring doubler so my calculations assumed the doubler was partially effective for tensile stresses...
  18. Lescombes

    Limit of Validity of Structural Idealisation

    Hello all, I recently completed a modification that introduced a round penetration to the shear web of a folded sheet metal fuselage floor keel beam. The keel beam is 0.050" thick 2024, of channel cross section, about 8" deep and has 0.75" wide return flanges. The upper and lower flanges...
  19. Lescombes

    Inspecting Flat Patterns to Paper Instead of Mylar

    I can't add any real value to this thread (as others have) however I will say that the OP is not alone: I'm also at a gen aviation OEM and have had this and many similar arguments with those whom wish to inspect to paper drawings rather than a dimensionally stable material.
  20. Lescombes

    Shear Web Buckling - with holes

    Thank you to all for your input. I did feel that FE would be a common suggestion, and being inherently conservative I went along the lines of rb's suggestion and added some additional structure to the web. One motivating factor was that - in answer to rb's question - the shear in the web is not...

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