Bolt preloading vs. temperature

[danohl]

Hi,
Using a gasket in a bolt connection; does the thickness of the gasket influence the preload of the bolt when the temperature changes?

Since the thermal expansion is length/length/temperature the thickness does not influence, what am I missing here? My current assumption is this:
ΔF_bolt = ΔT(α_gasket*E_gasket*A_gasket - α_bolt*E_bolt*A_bolt)

What I have is a steel bolt connection with a gasket of a different material (i.e. stiffness and thermal expansion is different). The bolt is preloaded and the subject to a temperature increase.

Cheers,
Daniel

 

[Navin A S]

Yes, the thickness of the gasket can influence the preload of the bolt when the temperature changes. This is because the thermal expansion of the gasket material will be different than the thermal expansion of the bolt material. As the gasket expands at a different rate than the bolt, the gap between the two will change. This leads to an increase or decrease in preload, depending on the relative expansion of the two materials. Additionally, the stiffness of the gasket material will affect how much the gap changes with temperature. So yes, the thickness of the gasket can influence the preload of the bolt when the temperature changes.