Hello, I would like to know if anyone can point me to any research or test data involving the failure of threaded fasteners due to thread laps. I have read several sources that claim the laps are potential causes of failure but I have not seen any actual test data to quanify or qualify those statements. Thanks in advance. Richard
Why don't you start by looking in the relevant handbooks? For an example of a failure from laps, look on pages 64 and 65 of Volume 12, Fractography in the (ASM) Metals Handbook, Ninth Edition, ASM International, Metals Park, Ohio 1987.
Then go look in the SAE handbook for Recommended Practice J123 (originally from 1973)titled "Surface Discontinuities on Bolts, Screws, and Studs in Fatigue Applications". Consensus standards don't get written unless there is a problem!
We don't believe what we write, and neither should you. Information furnished to you is for topical (external) use only. This information may not be worth any more than either a groundhog turd, or what you paid for it (nothing). The author may not even have been either sane or sober when he wrote it down. Don't worry, be happy.
Hi Pete, Thanks for your reply. I use SAE J123-94 and have read SAE J123C. They basically provide the acceptance criteria for thread laps and other types of discontinuities. They don't provide the technical rationale to support the criteria in the spec. I'm looking for the meat and potatoes, the actually test data that shows the failure effect from thread laps. So far the closest document I can find is posted here:
"Stress Intensity Factors Solutions for Cracks in Threaded Fasteners". I have seen a couple web pages that briefly discuss thread laps and I've seen them up close in the flesh but I have yet to see any engineering data describing their potential failure effects. Regards, Richard
You missed another paper that appeared in the same conference as the one by Oster and Mills that you cited. Go look in ASTM STP 1391, aka "Structural Integrity of Fasteners: Second Volume", ASTM 2000. The paper is titled "Thread Lap Behavior Determination Using Finite-Element Analysis and Fracture Mechanics Techniques", pages
120-132. You should be able to buy it from ASTM.
You also should go look up older SAE papers, and go look in Engineering Index. Get off the web and into an engineering library at your friendly local university. The web isn't an ocean of information - it's a tide pool about a foot deep.
Also, try posting your question on sci.engr.mech, since bolts are a relevant topic there too.
Hi Pete, Thanks again, I would not have know that ASTM paper existed had you not told me. I'm not an engineer or metallurgist but I do check for thread laps and I want to bone up on any technical information about them. Thanks! Richard