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  • Users: koopas
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  1. koopas

    Short ED and the substantiation thereof.

    Hello everyone, I have a question regarding short ED conditions and their substantiation. The following is the 3-step method generally accepted: 1. First, one either looks up or computes the bearing strength of the fastener/material combination using the SRM tables or the bearing formula...
  2. koopas

    How would you handle this repair disposition?

    Hello again, Here's the repair scenario involving a 2-inch long "T" section extrusion made from 7075-T6511, 0.100" thick. The horizontal flanges of the "T" are attached to the airplane belly skin with two Hi-Loks on each side of the vertical flange. So, all four Hi-Loks are loaded in...
  3. koopas

    Metallic Joint Bearing Strength

    Hello all, This question has been troubling me for a while... How would you calculate the joint bearing allowable of a single shear joint, IF the tested joint allowable for your particular configuration was not available from MIL-HDBK 5 or the SRM's? It's been beaten into me that using...
  4. koopas

    Load redistribution with missing fasteners

    Good day all, I have a fairly general question. Suppose you have a structural member (access panel, fairing, lap/butt joint, etc.) attached with fasteners. One or two fasteners are found to be missing, and assume that no replacements could be located. As the engineer, you have to make the...
  5. koopas

    Web repair design

    Hello all, It's been a while since I've posted on here. Hope everybody is doing well, and happily employed. I posted a question on webs a while ago and was essentially told to do some more reading on the subject before coming back. I started thinking about it today when I had to do a repair...
  6. koopas

    Webs and mode of failure

    Hello all and happy new year: I understand that a beam web is to take mostly shear loads while the tensile loads are carried by the caps. Here are my questions: 1. When cutting out a section of web and adding a doubler, why calculate the load transfer capability based on Ftu and not Fsu...
  7. koopas

    Eddy current and false positive & other burning questions

    Hi all, First of all, happy holidays everyone. I haven't posted here in a while...and neither have a lot of people from what I've noticed. A few general questions that have been bugging me: 1. A fuselage skin gouge is blended out. Inspection conducts a High Frequency Eddy Current check from...
  8. koopas

    Aloha 243 accident

    Hello all, I was reading about the Aloha 243 accident when I came across the website http://disastercity.com/ghost/ The author claims that the explosive decompression was due to the "fluid hammer effect" from the flight attendant being lodged in the flapped opening at STA 500...
  9. koopas

    Designing a fuselage repair to 15 ksi

    Hello all, Is designing a 767 rectangular [pressurized] fuselage cutout repair to carry 15 ksi in the hoop direction and half of that in the longitudinal direction acceptable, given the fuselage radius, local skin thickness, and pressurization level? Indeed, this is much less than designing...
  10. koopas

    Novice at FEA: needs advice

    Hi all, I did some limited FEA in FEMAP/NASTRAN back at the university a year ago. I now work at an airline and would like to model structural metallic joints using finite elements to get fastener loads, stresses, deflections, etc. Frankly, I don't recall much of FEA at all, but am willing to...
  11. koopas

    Single and double shear joint questions

    Good Monday all, I was thinking about single and double shear fastened joints and came up with a few questions: 1. Mil-Hdnbk 5 and the SRM give joint allowables for material/fastener combinations for single and double shear loading conditions. Essentially, the lower value of the fastener...
  12. koopas

    Reduced fatigue life due to end fastener loads

    Good morning all, I was reading the FAA paper by T. Swift entitled "Repairs to Damage Tolerant Aircraft" http://www1.faa.gov/certification/aircraft/FAA-AIR-90-01.pdf I've got a few questions regarding the highest rivet loads at the first row (end row) of fasteners (pages 3, 4, figs...
  13. koopas

    Mechanics of materials books

    Hi all, Could you recommend several good books for a refresher on mechanics of materials? So far, I've found "Mechanics of Materials" by Hibbeler and another book by the same title by Johnston and Beer having obtained favorable reviews. Any suggestions? Thanks, Alex
  14. koopas

    Repost: Induced bending moment in a thick shim

    This is a repost of my thread that was deleted yesterday. I was reading through an old Douglas structural repair training class manual and found an example on shimming. The problem involves DD6 rivets, each carrying a load of 1,000 lb (MS of 0.18), and the introduction of a 1/16-inch-thick...
  15. koopas

    Clamp-up versus preload

    Hi all, What's are the differences between "clamp-up" and "preload" pertaining to fastened joints? Clamp-up: essentially how "tight" the press is in a fastened joint. Ranges from low for a high shear rivet to high for a hi-lok. Seems to me that clamp-up is...
  16. koopas

    Short ED, again

    Hi all, I am still a relatively new and inexperienced airline structural engineer. I have a question about fastener short edge distance relative to a part's edge, again (I posted a similar message a few months ago, apologies if sections are redundant) I'd like to know if the following...
  17. koopas

    Fastener allowables and Shear-out formula

    Hello all, For those who work as airline/repair station structural engineers, how do you handle short edge distance (ED) problems? I am getting a little confused. The SRM or MIL-HDBK-5 join allowable tables gives you the strength of fastener/material combinations. From what I've read, the...
  18. koopas

    Liaison Engineer Referece Texts & Repair Question

    Hello all, Last week, I got a hold of both of Michael Niu's books on stress analysis and structural design. Someone suggested to me Jean Claude Flabel's Practical Stress Analysis for Engineers. Can you recommend this book? I've read fairly positive reviews. Another classic which I've only...
  19. koopas

    Update from the "new engineer in the field"

    Hey all, Whoa! Can't believe it's already been about five months since my original post entitled "New engineer in the field - needs advice". At the time, I was a little lost at my new job. Time does fly by fast. Just to give you an update, I went ahead and took the FSB part I...
  20. koopas

    New engineer in the field - needs advice

    Hello to all: I am new to the forum. I just started my job after obtaining my B.S. in aerospace engineering this past May. Working as a liaison/structural engineer for a small airline, I feel like I have lots to learn about aircraft repairs. By that, I mean that I am under the impression...

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