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Recent content by koopas

  1. koopas

    Shaving of Rivet Heads For Countersink Fasteners

    AEU, Microshaving of NAS1097 shear head rivets is prohibited by the SRM. Shaving a MS20426 rivet head is permitted. Refer to Chapter 51 of the SRM for dimension requirements before and after shaving to maintain rivet strength. Alex
  2. koopas

    Short ED and the substantiation thereof.

    HSThompson, Thanks for your feedback. You wrote: "If after calculating fsr shear, bearing, tear-out, and net tension the failure mode remains unchanged then your good. If not, then you have to make it up somewhere." Since a fastener joint is usually designed to be critical in bearing, you...
  3. koopas

    Metallic Joint Bearing Strength

    Hello Sparweb, Thanks for the smoking rivets link. The article mentions that a smoking rivet is a loose or working rivet. Working?? (Aircraft lingo baffles me sometimes.) Pardon my ignorance, but what do you mean by "The Delta-Fsu method and the Grumman data exchange places a few times."...
  4. koopas

    Metallic Joint Bearing Strength

    Sparweb, I calculated the AD4 allowable in 0.040" Clad 2024-T3 by multiplying the "E" rivet allowable by the ratio of Fsu's. I am coming up with the following: NAS1097E4 in 0.040" Clad 2024-T3: 437 pounds (Mil-Hndbk 5J) Fsu of "AD" rivet: 30 ksi (Mil-Hndbk 5J) Fsu of "E" rivet: 43 ksi...
  5. koopas

    Short ED and the substantiation thereof.

    Hola Jetmaker, I agree with you that the Douglas analysis must assume that a shorter ED does not reduce the bearing strength. Otherwise, the analysis makes no sense. I've emailed the instructor, and have communicated to him my concerns. Could you please re-explain what you meant in your...
  6. koopas

    Short ED and the substantiation thereof.

    G'day Jetmaker, The procedure I initially listed is the one followed in a Douglas training manual for sustantiating short ED conditions. In step (1), the bearing allowable that's either looked up or calculated, is based on a FULL 2D ED, even though the discrepant fastener only has 1.5D ED...
  7. 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...
  8. koopas

    Metallic Joint Bearing Strength

    Sparweb, You're right. Once again, I should think a little more before typing on the keyboard. Ratioing the Fbru's would only be applicable when you want to determine the bearing allowable of a joint for which no test data is available, by multiplying the known joint allowable of the...
  9. koopas

    Metallic Joint Bearing Strength

    Hello Sparweb, Welcome back! I presume you wanted to determine the bearing allowable of the NAS1097AD rivets in aluminum. Why did you scale the "E" rivet's bearing allowable to the Fsu's of the rivet materials instead of the Fbru's of the sheet metal materials? Wouldn't it make more sense...
  10. koopas

    How would you handle this repair disposition?

    Good morning Jetmaker, Thank you for correcting my terminology. I've thought about the other load paths where strength may be less than in the tee's vertical flange I've beat to death previously. Such an area, as you mentioned, could be where the horizontal flange of the "T" attaches with...
  11. koopas

    How would you handle this repair disposition?

    Good day Jetmaker, Thanks for your insight. I want to make sure that I fully understand the implications of your latest reply. Since you're stressing to use of the entire part's cross sectional area minus area of all fastener holes as the net area to calculate the net tension allowable, it...
  12. koopas

    How would you handle this repair disposition?

    Good morning Jetmaker, I appreciate your continued tutelage. Regarding A1, So you're saying that you would take into account the decrease in Fbru with a reduced ED? When you wrote "Not that most protruding head fastener bearing allowables are given for 1.7D edge margins." Did you mean to...
  13. koopas

    Metallic Joint Bearing Strength

    Good day Jetmaker, Do you mean that the ratioing deal is only valid for materials within their alloy group (i.e. within the 2000 aluminum group)? In other words, you couldn't use the ratioing principle to determine the unknown allowable in 7075 using a known allowable in 2024? I am not sure I...
  14. koopas

    How would you handle this repair disposition?

    Good day Jetmaker, You're right. I couldn't regain the bearing strength lost with 1st or 2nd O/S. Going to the next size fastener did the trick though, as I regained a positive MS in bearing for the overall two-hole joint configuration. Luck was on my side, also, since I still had 2D+ ED...
  15. koopas

    Metallic Joint Bearing Strength

    Hello Jetmaker, After doing a bit of reading tonight, I've clarified a few of my own confusions... IF 1. fastener is solid, not hollow or multi-piece 2. fastener has protruding head 3. fastener has tension protruding head for bolts 4. t/D > 0.18 (ref. Mil-hdbk 5J, 9.7.1, pp 9-142) then, and...
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