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Re: Thermal props of high tensile bolts

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>Does anyone know whether the thermal coefficient of expansion for a high
>tensile bolt (UTS=1050 MPa, yield stress = 945 MPa) is any different to that
>for mild steel?
No. Provided you're not including any austenitic steel or high nickel alloy high tensile bolts. And the temperature you specified wouldn't have any effect on yield strength either. 

>I have a problem where an argument has been raised regarding the loss of
>pre-tension in a torqued screw, where the screw is high tensile and the
>components are mild steel.  The claim is that after heating the assembly to
>130°C (266°F) for a couple of hours, the thermal differences in the two
>steels causes significant loss of prestress.
If the temperature were non-uniform you might lose preload. For example if your claimant didn't get the bolt hot so it didn't expand with the rest of the assembly, you might yield the screw and lose pre-load.

Christopher Wright P.E.    |"They couldn't hit an elephant from
chrisw(--nospam--at)        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)