Expanding device for shape memory alloy pipe joint

Abstract

The invention relates to an expanding technology for a shape memory alloy pipe joint, in particular to an expanding device for the shape memory alloy pipe joint. The expanding deice comprises an insulation barrel containing liquid nitrogen, a guide base, a reaming main push rod and a radial reaming casing pipe, wherein the radial reaming casing pipe is sheathed on the reaming main push rod, and the upper end part of the reaming main push rod is provided with a tapered boss; a plurality of left-opening through slots and right-opening through slots are respectively formed in the radial reaming casing pipe along the opening directions of two ends to divide the wall body of the radial reaming casing pipe into a plurality of elastic sheets. The expanding device for the shape memory alloy pipe joint, which is designed by the invention, can integrally expand the shape memory alloy pipe joint. Compared with the prior art, the expanding device has the advantages of large and uniform radial stretching amplitude, easiness in control over the expanding size and the like. Meanwhile, the pipe joint processed by the device has small residual stress and good axial symmetry, and the connecting intensity and overall performance are greatly increased. The expanding device can be used for expanding small-bore joints.

Description

technical field [0001] The invention relates to a diameter-expanding technology of a shape-memory alloy pipe joint, in particular to a diameter-expanding device for a shape-memory alloy pipe joint. Background technique [0002] Shape memory alloys are smart materials that can remember their original shape. The most typical application of the shape memory effect is the shape memory alloy pipe joint. [0003] Shape memory alloy pipe joints can realize the connection of two pipes, which is different from threaded mechanical connection and welding. The shape memory alloy pipe joint is a simple cylinder, which is machined in the parent phase state, its inner diameter is slightly smaller than the outer diameter of the connected piece, and the inner diameter is machined with ridges. During application, the shape memory alloy pipe joint is cooled to the martensitic state, and the diameter of the pipe joint is expanded by mechanical force, so that the inner diameter of the pipe joi...

AI Technical Summary

Problems solved by technology

However, at present, the diameter expansion of the shape memory alloy pipe joint is realized by passing the rigid tapered punch through the pipe. Since the tapered punch passes through the pipe joint, it is in partial contact with the inner wall of the pipe joint. Therefore, the overall deformation of the pipe joint does not occur during the diameter expansion process, so there will be a large residual stress inside the pipe joint produced by this process

These residual stresses will not only affect the dimensional accuracy of the pipe joint, but may even continue to exist during the shape recovery process after assembly, affecting the connection performance, and will reduce the stress corrosion resistance of the pipe joint, thus reducing its service life

In addition, when the tapered punch is used to mechanically expand the shape memory pipe joint, it often causes local plastic deformation or scratches on the inner surface of the pipe joint, which will affect the shape memory effect and fastening force of the shape memory alloy pipe joint.

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