Shape-memory coupling

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Shape-memory coupling is a system for connecting pipes using shape-memory alloys. In its typical form the technique uses an internally ribbed sleeve of alloy such as Tinel that is slightly smaller in diameter than the pipes it is to connect. The sleeve is cooled in liquid nitrogen then, in this low-temperature state, mechanically expanded with a mandrel to fit easily over the two pipe ends to be joined. After fitting, it is allowed to rewarm, when the memory effect causes the sleeve to shrink back to its original smaller size, creating a tight joint.

A shape-memory alloy is an alloy that "remembers" its original shape and that when deformed returns to its pre-deformed shape when heated. This material is a lightweight, solid-state alternative to conventional actuators such as hydraulic, pneumatic, and motor-based systems. Shape-memory alloys have applications in robotics and automotive, aerospace and biomedical industries.

Liquid nitrogen

Liquid nitrogen is nitrogen in a liquid state at an extremely low temperature. It is a colorless liquid with a density of 0.807 g/ml at its boiling point (−195.79 °C (77 K; −320 °F)) and a dielectric constant of 1.43. Nitrogen was first liquefied at the Jagiellonian University on 15 April 1883 by Polish physicists, Zygmunt Wróblewski and Karol Olszewski. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is often referred to by the abbreviation, LN2 or "LIN" or "LN" and has the UN number 1977. Liquid nitrogen is a diatomic liquid, which means that the diatomic character of the covalent N bonding in N2 gas is retained after liquefaction.

Mandrel

A mandrel is one of the following:

It was first produced in the late 1960s or early 1970s by the Raychem Corporation under the trade name CryoFit. Manufacture of these couplings for aerospace hydraulic connections was later transferred to AMCI (Advanced Metal Components Inc.) and then later to Aerofit Products Inc. Additional products using the same shape-memory alloy technology are produced under Cryolive and CryoFlare trade names.

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