Crushing under high strength bolt heads
Crushing under high strength bolt heads
(OP)
When using high strength fasteners, crushing under the head can occur, even if you use a steel washer. What's the criterion, in terms of tensile yield strength, for max compressive stress before permanent deformation occurs.





RE: Crushing under high strength bolt heads
Design Mechanical and Physical Properties of AISI 1025 Carbon Steel.
Ftu, ksi:. . . . . . . . . . . . . 55
Fty, ksi: . . . . . . . . . . . . 36
Fcy, ksi:. . . . . . . . . . . . . 36
Fsu, ksi . . . . . . . . . . . . . 35
Et, 103 ksi . . . . . . . 29.0
Ec, 103 ksi . . . . . . . 29.0
G, 103 ksi . . . . . . . 11.0
Physical Properties:
?, lb/in.3 . . . . . . . . . . . . . 0.284
From Table 2.2.1.0(b) in Metallic Materials Properties Development and Standardization (MMPDS) Handbook (Jan. 2003).
RE: Crushing under high strength bolt heads
For bolted joints, the analysis of interest is for the applied surface pressure, which is compared with the allowable surface pressure for the material. While there is a geometry effect, in general, the allowable surface pressure for ductile metals is approximately equal to the Ultimate Tensile Strength. This allowable surface pressure is higher than the compressive yield strength due to the restraining effect of the surrounding material of the clamped part. This is similar to indentation hardness testing. If you have a disc of material that is sufficiently thick and large in diameter, a localized pressure must be approximately 3 times the yield stress to cause indentation. For a bolted joint, you have a similar load case (but with a hole in the object).
There is a good description of allowable surface pressure analysis in VDI 2230 (see FAQ725-600 for a description of this reference).
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Crushing under high strength bolt heads
RE: Crushing under high strength bolt heads
RE: Crushing under high strength bolt heads
RE: Crushing under high strength bolt heads
RE: Crushing under high strength bolt heads
Ermittlung der Grenzflächenpressung unter einachsialer kontinuierlicher Beanspruchung bei Raumtemperatur, Konstruktion July/August 2002, pages 38-42, available at:
http://www.technikwissen.de/kon/article.php?data[article_id]=13389
and
Grenzflachenpressung von Eisenwerkstoffen und Leichtmetallen unter kontinuierlicher Beanspruchung, Materialwissenschaft und Werkstofftechnik 2006, 37, No. 10, pages 894-899, available at:
http://ww
Lastly, I can say that the Bearing Yield Stress values shown in MIL-HDBK-5 are essentially equivalent to the allowable surface pressure values in VDI 2230, and the handbook is free.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.