Bearing area

[dengmech]

I have a spacer being clamped between a nut and bolt. The length is quite short so buckling isn't a concern. The ID id fixed at .79" how thick (pick the OD and area) do I need to make it to withstand the preload about 24,000 lb and an external compressive load of 8,500 lb. I don't think just using the yield strength is adequate since it is really conservative.

 

[rb1957]

so you want a sleeve, id = 0.79", od = ?, to carry 24000+8500 lbs ? i'd use fcy

Quando Omni Flunkus Moritati

 

[dhengr]

Less than Fy, Conservative? What are you talking about, if it yields, you’ve lost your preload. In fact as it is loaded elastically your preload starts to change, or at least this must be taken into account. They used to call these flat washers.

 

[rb1957]

this is compression, no? so the joint is in compression from the preload, and supporting the external compression load as well (the bolt is going along for the ride, no?)

Quando Omni Flunkus Moritati

 

[TVP]

The limiting surface pressure (term used in the standard VDI2230 to define this condition) for steels is ~ 0.9 * UTS. This value is also about the same as the bearing yield strength reported in MIL-HDBK-5 and its successors. Here is a previous thread that discusses some of this:

thread404-179453

 

[Cockroach]

Using mild steel (43 ksi) typical of off the shelf tubing, I get an OD of 1 3/16 inches. This assumes your 24 kip pre-load with 8.5 kip external compressive load will give you a factor of safety of 1.25. As noted, you want to resist collapse in which case the pre-load would be lost.

Incidently, you won't get an answer in this forum, more questions yes, but never an answer. Go with 1.188 inches as an OD.

Regards,
Cockroach

 

[Cockroach]

Pardon me...OD is 1.352 inches or about 1 23/64 inches. Forgot the factor of safety to be 1.25 inches.

Regards,
Cockroach