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The modulus of Diliavar is likely to be on the 195-200GPa range as it is basically an iron based alloy.
Iron has a nominal Modulus of 207GPa and a 25%Cr/20%Ni Alloy such as HK40 is 198GPa so alloy content has a limited influence on this property.
I believe Supertec studs are 17-4PH which is a precipitation hardening Martensitic Stainless Steel.
The coefficient of expansion will be around 10.5mm x 10^-6/m/degK.
This is virtually identical to a conventional steel stud.
Dilavar appears to be an Austenitic alloy as they are non-magnetic and if they are precipitation hardening in nature the Coefficient of expansion is likely to be around 18-19mm x 10^-6m/m/degK and could be higher than this.
I think it is reasonable to assume that the stresses developed will be directly proportional to the DeltaT and the Coefficient of Expansion. I don't think the length has much influence.
The expansion of the cases is constant so conventional steel studs and any martensitic steel studs will produce higher stresses in threads than Dilavar.
The main disadvantage of the Dilavar type of alloy is that they can be sensitive to Stress Corrosion Cracking particularly in the presence of chlorides hence the resin coating.
I am also not sure if there is much evidence of pulled threads in Aluminium cased engines.
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