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interface pressure and possible torque - LamT's equations

interface pressure and possible torque - LamT's equations

interface pressure and possible torque - LamT's equations

(OP)
I've found the formulas (see attached pdf-file) in thread 1090698.

However could someone confirm those, or can provide a source?
I've checked Roark's but it isn't mentiond (the section "thermal stresses" is rather limited).
Machinist's handbook also doesn't give the formule for two different materials.

Problem is that it differs 10^6 even with being consistent in N and mm and mm², and that the found value seems rather high (even when divided by 10^6).

Am I using the correct formula? all opinions are much appreciated...

The application is a brass knob (22-40 dia) which needs to be heated and fitted to a steel shaft (14-22 mm dia) with a total interference of about 0.03 mm (tolerance is 22R8 on the knob).

Thanks.

RE: interface pressure and possible torque - LamT's equations

(OP)
Also, what would an appropriate COF be for brass (CuZn40) hub and steel shaft, both machined to standard Rm ?

I found sources for 0.05-0.10 and other says around 0.35.
This is less critical, as even with 0.05 the torque would suffice for this application - I'm just being curious.

RE: interface pressure and possible torque - LamT's equations

(OP)
My mistake about the 10^6 difference, I made a mistake in my Young's modulus.

Any comments on the correctness of the formula (although now I seem to have rather correct values)
and about the COF ?

RE: interface pressure and possible torque - LamT's equations

Thick walled cylinder theory.

COF (steel-brass): 0.35 (dry clean surfaces) - 0.19 (lubricated)

RE: interface pressure and possible torque - LamT's equations

(OP)
The formula I found here gives other results than the one in this pdf (page 14)
http://www.faculty.fairfield.edu/wdornfeld/ME311/PressCylinderHam.pdf

That formula gives the exact same results as the tribology calculator
http://www.tribology-abc.com/calculators/e3_8.htm
so I believe it to be correct.

So I believe either I misinterpreted something, or the formula given in that thread contains an error (in the denominator, there are two "[" but only "]" ???
That formula can be found here:
http://www.eng-tips.com/viewthread.cfm?qid=109069&page=204


 

RE: interface pressure and possible torque - LamT's equations

The formula in the original thread is correct and it's the same as that reported in the link concerning thick walled cylinder. The formula in your OP is not correct: you've definitely misinterpreted it

RE: interface pressure and possible torque - LamT's equations

These equations in the original thread are from Thick Wall Pressure Vessel Theory and are the classical ones for contact pressure.  These are correct, as Icone has pointed out.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

RE: interface pressure and possible torque - LamT's equations

(OP)
The intention of the formula was correct, however if you check my last attached file (march 22 - 9:57) you'll see that there is a sign (plus/minus) and an index Vo/Vi) incorrect, as well as two brackets.

Hence my question, as there was a 20+ % difference with the on-line calculator (tribology website) I referred to above.

 

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