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Expansion pressure from disimilar metals
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Posted by: dansensel

05/26/2005, 10:00:34

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I have a small problem for all of you materials people:

If I wrap a steel bandclamp around an aluminum rod (1" diameter) and then heat this assembly to 1100F, what type of tension can be expected as a result of the thermal stresses. Only the thermal stresses are needed.

Thanks.







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Re: Expansion pressure from disimilar metals
Re: Expansion pressure from disimilar metals -- dansensel Post Reply Top of thread Forum
Posted by: zekeman

05/27/2005, 15:02:06

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Coefficient of thermal expansion of aluminum is about
13 microinches/inch per deg F
For steel depending on its composition has a range of :
6 to 10 microinches /inch per deg F
Therefore, taking the worst case of 6 for steel,
over 1130 degree temp rise assuming start temp at 70 deg F, the difference in strain between the steel and Al is
(13-6)*1130*10^-6=7.91*10^-3
In order to accommodate this expansion the band is stretched under tension and the aluminum rod is compressed by the same total force on the band. The usual and conservative assumption (a good one) is that the differntial strain is manifested in the band only. Since the modulus of elasticity of steel is
30,000,000, the resultant stress in the steel band is
30*10^6*7.91*10^-3= 237,300 psi which is a problem.
At the other end of the range for steel the tensile stress is
30*10^6*(13-10)*1130*10^-3= 101,700 psi
which is still a problem at elevated temps.






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Re: Expansion pressure from disimilar metals Smile
Re: Re: Expansion pressure from disimilar metals -- zekeman Post Reply Top of thread Forum
Posted by: dansensel

05/27/2005, 15:36:22

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Thank you very much kind sir.






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