In certain applications, it is necessary to combine a high mechanical stability, also called buckling strength, with a high thermal and/or electric isolation power. This is especially true for mechanical supports for “cryogenic” systems. Such supports comprise two bearing surfaces, one of these surfaces being in contact with an object to be maintained at cryogenic temperatures, and the other surface being in contact with an environment capable of being at another temperature. In the case of superconducting magnets, for example, such supports may be submitted to very high stress, capable of reaching several thousands of kilonewtons (kN), exerted via one of the bearing surfaces by the supported objects, which may weight several tons. Given that the two bearing surfaces are at different temperatures, there exists in the support a thermal flow from hot areas to cold areas.
To limit the power necessary to cool the supported object, it is accordingly necessary to guarantee the thermal isolation of the support in order to decrease this thermal flow. Current cryogenic supports are often formed of a supporting cylinder called shell. Such mechanical are commonly made of stainless steel, which provides a good mechanical resistance, at a low cost. However, stainless steel is a good heat conductor, which requires using cooling systems, which are more bulky and thus not very convenient to use, and above all more expensive, to maintain the supported object at a fixed temperature.
It is possible to select materials having better thermal isolation properties than stainless steel to manufacture such shells, for example, composite materials, which are known to have a low heat conduction. However, the composite shells have a low mechanical reliability.
Another possible solution to manufacture shells of high mechanical resistance comprises using a titanium alloy (for example, TA6V). The structure thus obtained is four times more mechanically resistant than a stainless steel shell, but although it is twice more isolating than stainless steel, it has the disadvantage of being a good heat conductor, like stainless steel, while being five times more expensive to manufacture than a stainless steel shell.
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