CN102423784A - Elastic medium-based expanding device and method for shape memory alloy pipe joint - Google Patents

Abstract

The invention aims to provide a shape memory alloy pipe joint expanding device and method based on an elastic medium. The device has simple structure and easy manufacture, and the shape memory alloy pipe joint produced by the invention has the advantages of integral deformation under static force, uniform deformation, high dimensional precision, small residual stress and better connection performance.

Description

Device and method for expanding diameter of shape memory alloy pipe joint based on elastic medium

technical field

The invention relates to a device and method for metal diameter expansion.

Background technique

Shape memory alloy (SMA) is a new type of functional material developed in the early 1960s, and has been widely used in aviation, aerospace and medical fields. This material has a shape memory effect, that is, after being plastically deformed at a low temperature, and then heated to a certain temperature, the material will return to the state before deformation. The shape memory alloy pipe joint is to use the shape memory effect of the alloy. First, the pipe joint whose inner diameter is slightly smaller than the outer diameter of the pipe to be connected is expanded and deformed at low temperature, so that the inner diameter is larger than the outer diameter of the pipe to be connected. The two parts are easily assembled together in this low temperature state, and then the assembled joint is heated to a certain temperature, so that the inner diameter of the shape memory alloy pipe joint returns to the size before deformation. Make the two parts tightly connected together. Pipe joints are one of the most mature applications of shape memory alloys, especially in aviation hydraulic piping systems. All kinds of pipe joints made of shape memory alloy have the advantages of high reliability, less leakage, simple structure, convenient installation and saving assembly space. According to reports, 1.5 million shape memory alloy pipe joints have been used in the oil pressure pipelines of various types of aircraft in the United States, and no oil leakage accident has occurred. The United States has stipulated that shape memory alloys must be used in all new aircraft hydraulic lines.

But 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, it is always in partial contact with the inner wall of the pipe. The overall deformation does not occur during the diameter expansion process, so there will be a lot of 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 restore the shape after assembly The process continues to exist, which will reduce the stress corrosion resistance of the pipe joint, thereby reducing its fatigue life. In addition, when the tapered punch is used to mechanically expand the shape memory pipe joint, it is easy to cause 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.

Contents of the invention

The object of the present invention is to provide a shape memory alloy pipe joint expansion device and method based on elastic media that can be used on ordinary presses and can efficiently form uniform deformation, small residual stress and high dimensional accuracy.

The purpose of the present invention is achieved like this:

The shape memory alloy pipe joint expansion device based on elastic medium in the present invention is characterized in that it includes a backing plate, a fixing plate, an upper pressing head, a lower pressing head, a spring, an elastic rod, an elastic ring, and a punch, and the upper pressing head is installed on the lower pressing head. On the indenter, one end of the elastic rod is installed in the lower indenter, the other end of the elastic rod is installed in the upper indenter, the elastic ring is set on the elastic rod, the fixed plate is connected with the backing plate, and the upper indenter is connected with the fixed plate and the backing plate by bolts A spring is installed on the bolt, one end of the spring is connected with the fixing plate, the other end of the spring is connected with the lower pressing head, one end of the punch is installed in the fixing plate, and the other end of the punch is installed in the lower pressing head and links to each other with the elastic rod.

The method for expanding the diameter of a shape memory alloy pipe joint based on an elastic medium in the present invention is characterized in that:

(1) The expansion device of the shape memory alloy pipe joint based on the elastic medium is adopted to expand the diameter, and the described expansion device of the shape memory alloy pipe joint based on the elastic medium comprises a backing plate, a fixing plate, an upper pressing head, a lower pressing head, Spring, elastic rod, elastic ring, punch, the upper pressing head is installed on the lower pressing head, one end of the elastic rod is installed in the lower pressing head, the other end of the elastic rod is installed in the upper pressing head, the elastic ring is set on the elastic rod, and the fixing plate Connected with the backing plate, the upper pressing head is connected to the fixing plate and the backing plate through bolts, a spring is installed on the bolt, one end of the spring is connected to the fixing plate, the other end of the spring is connected to the lower pressing head, one end of the punch is installed in the fixing plate, and the punch The other end of the lower pressure head is installed in the lower pressure head and connected with the elastic rod; firstly, the expansion device of the shape memory alloy pipe joint based on the elastic medium is placed on the working table of the press machine, and after the center is aligned, the pressure plate is used to press the protrusion of the lower pressure head Then fix the lower pressing head on the workbench, start the press to make the upper slider move down to contact with the backing plate, then use the pressure plate to press the flange of the backing plate, and fix the backing plate mold on the press On the slider, start the press to move the upper slider upward, and stop the upward movement of the slider when the open space of the upper and lower parts is enough to put the workpiece;

(2) Put the shape memory alloy tube blank on the elastic ring, make the lower end of the shape memory alloy tube blank contact the surface of the lower pressure head, and then start the press to move the backing plate downward, when the upper pressure head and the lower pressure head After the shape memory alloy tube blank contacts, it stops moving due to the obstruction of the shape memory alloy tube blank. At this time, as the backing plate continues to descend, the upper pressing head will press the elastic ring and the shape memory alloy tube blank under the elastic force of the spring. The upper end is pressed, and as the punch moves down, the elastic rod will bulge locally in the radial direction at the part in contact with the elastic ring, thereby driving the elastic ring to bulge radially together with it, and this radial force will be transmitted Give the shape memory alloy tube blank that is set outside the elastic ring to make it expand in diameter and bulge as a whole;

(3) Open the backing plate and the lower pressure head to make it return to the position before loading. At this time, the elastic rod and elastic ring return to the state before deformation after the external force is removed, and the formed workpiece is taken out to complete the diameter expansion.

The present invention may also include:

1. There is a flange on the backing plate, and a flange on the lower pressure head.

2. There are four bolts, and four holes for installing bolts are arranged on the backing plate.

3. The contact surface between the upper indenter and the shape memory alloy used for processing is an inclined surface.

4. The vertical edge of the lower pressing head and the inner wall of the outer ring of the upper pressing head adopt a sliding fit.

The advantages of the present invention are:

1. No special experimental equipment is required, the single-action double-press function can be realized on the ordinary single-action press, and the diameter expansion forming of the shape memory alloy pipe joint can be completed.

2. The structure of the device is simple and easy to manufacture. Only one set of device is required to replace the polyurethane rubber ring to complete the expansion of the shape memory alloy pipe joints with different diameters, so it has strong versatility.

3. The device is easy to use, reliable, low in cost and high in work efficiency.

4. The shape-memory alloy pipe joint produced by this device deforms as a whole under static force, with uniform deformation, high dimensional accuracy, small residual stress and better connection performance.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the upper touch schematic diagram of the present invention;

Fig. 3 is a structural diagram of the elastic device of the present invention;

Fig. 4 is a structural diagram of the lower mold of the present invention.

Detailed ways

The present invention is described in more detail below in conjunction with accompanying drawing example:

With reference to Figures 1-4, the present invention consists of three parts, an upper mold, an elastic device and a lower mold, as shown in Figures 2-4 respectively.

The upper mold part (Fig. 2) is composed of a backing plate 1, a fixed plate 2, a spring 3, an upper pressing head 8, a punch 9, a stepped bolt 10 and a fixing bolt 11. There is a flange on the backing plate 1, which can be directly connected with the upper slider of the press, and there are four stepped holes on it, which are used for embedding of four stepped bolts 10 when the device is assembled. The stepped bolts 10 and the backing plate 1 A gap fit is adopted between them, so that the smooth part of the stepped bolts can freely pass through, and there are 4 threaded holes under the backing plate 1 for screwing in the 4 fixing bolts when assembling with the fixing plate 2 and the punch 9; The stepped hole in the center of the fixing plate is used for the embedding of the upper step of the punch 9 during assembly, the four surrounding stepped holes are used for embedding the fixing bolts 11, and the four peripheral through holes are used for passing through the four stepped bolts 10. These holes and the bolts are fitted with gaps, so that the stepped bolts 10 can slide freely in the middle; the smooth parts of the four stepped bolts 10 are respectively covered with 4 springs, and one end of the thread is connected with the upper pressure head 8; the upper pressure head There is also a through hole at the center of 8, which adopts a sliding fit with the punch 9. In addition, the contact surface between the upper indenter 8 and the shape memory alloy tube blank 7 should adopt an inclined surface, so that the contact with the workpiece can be a line contact, so that Reduce friction during diameter expansion. Such a structure can realize the function of single action and double pressure when the upper die is working.

The elastic device ( FIG. 3 ) consists of a polyurethane rubber rod 4 and a polyurethane rubber ring 5 . When the device is working, the punch 9 can directly press the end of the rubber rod 4 to cause local bulging, and the generated radial force is transmitted to the rubber ring 5, thereby causing the overall radial bulging, and then the rubber The ring 5 transmits uniform radial force to the shape memory alloy tube blank 7 to produce uniform overall bulging.

The lower mold part (Fig. 4) has only the lower pressing head 6. The lower part of the lower pressing head 6 has a flange, which can be directly fixed on the workbench of the press, and has a blind hole in its center for the positioning of the elastic device. The protruding vertical edge on it adopts sliding fit with the inner wall of the outer ring of the upper pressing head 8 in the upper die to act as a guide, so that the whole set of devices will not affect the dimensional accuracy of the parts due to eccentricity during work.

The implementation of the method of the present invention is divided into three stages, that is, the preparation stage, the diameter expansion stage and the unloading stage.

Preparation stage: first put the whole set of devices together on the workbench of the press, press the flange of the lower mold with a pressure plate after aligning the center, and then fix the lower mold on the workbench with bolts. Start the press to make the upper slider move down to contact with the backing plate of the upper mold, then press the flange of the upper mold with the pressure plate, and fix the upper mold on the upper slider of the press with bolts. Start the press to move the upper slider up, so that the upper and lower molds will be opened, and when the open space of the upper and lower molds is enough to put the workpiece, stop the slider from moving up.

Diameter expansion stage: set the shape memory alloy tube blank 7 on the elastic device embedded in the lower mold, make the lower end of the shape memory alloy tube blank 7 contact with the taper surface of the lower mold, and then start the press to move the upper mold downward . After the upper pressing head 8 contacts the shape memory alloy tube blank 7, it stops moving due to the obstruction of the shape memory alloy tube blank 7. At this time, as the upper die continues to move downward, the upper pressing head 8 will be in the position of the four springs 3. Under the action of elastic force, the rubber ring 5 and the upper end of the shape memory alloy tube blank 7 are pressed to prevent them from being deformed in the axial direction, and at the same time, the tube blank will not be pressed too hard to hinder the diameter expansion. In this way, as the punch moves down, the rubber rod 4 will only partially bulge in the radial direction at the part in contact with the rubber ring 5, thereby driving the rubber ring 5 to undergo radial bulging together with it. The force will be transmitted to the shape memory alloy tube blank 7 sleeved on the outside of the rubber ring 5 to make it expand in diameter and bulge as a whole. The specific diameter expansion size can be controlled by adjusting the stroke of the slide block of the press.

Unloading stage: After the diameter expansion is completed, open the upper and lower molds to make them return to the position before loading. At this time, the elastic device will return to the state before the deformation due to the elastic recovery after the external force is removed. At this time, it can be Take out the formed workpiece smoothly.

In this way, the diameter expansion process of a shape memory alloy pipe joint is completed.

Claims (10)

1. The expansion device of shape memory alloy pipe joint based on elastic medium is characterized in that it includes a backing plate, a fixed plate, an upper pressure head, a lower pressure head, a spring, an elastic rod, an elastic ring, and a punch, and the upper pressure head is installed on the lower On the indenter, one end of the elastic rod is installed in the lower indenter, the other end of the elastic rod is installed in the upper indenter, the elastic ring is set on the elastic rod, the fixed plate is connected with the backing plate, and the upper indenter is connected with the fixed plate and the backing plate by bolts A spring is installed on the bolt, one end of the spring is connected with the fixing plate, the other end of the spring is connected with the lower pressing head, one end of the punch is installed in the fixing plate, and the other end of the punch is installed in the lower pressing head and links to each other with the elastic rod. 2. The expansion device for shape memory alloy pipe joints based on elastic media according to claim 1, characterized in that: the backing plate has a flange, and the lower pressing head has a flange. 3. The expansion device for shape memory alloy pipe joints based on elastic media according to claim 1 or 2, characterized in that: there are four bolts, and four holes for installing bolts are provided on the backing plate. 4. The expanding device for shape memory alloy pipe joints based on elastic medium according to claim 1 or 2, characterized in that: the contact surface between the upper indenter and the shape memory alloy used for processing is an inclined surface. 5. The expanding device for shape memory alloy pipe joints based on elastic medium according to claim 3, characterized in that: the contact surface between the upper indenter and the shape memory alloy used for processing is an inclined surface. 6. The expanding device for shape memory alloy pipe joints based on elastic media according to claim 1 or 2, characterized in that: the vertical edge of the lower pressing head and the inner wall of the outer ring of the upper pressing head adopt a sliding fit. 7 . The expanding device for shape memory alloy pipe joints based on elastic media according to claim 3 , wherein the vertical edge of the lower pressing head is in sliding fit with the inner wall of the outer ring of the upper pressing head. 8 . 8 . The expanding device for shape memory alloy pipe joints based on elastic media according to claim 4 , wherein the vertical edge of the lower pressing head is in sliding fit with the inner wall of the outer ring of the upper pressing head. 9 . 9. The expanding device for shape memory alloy pipe joints based on elastic media according to claim 5, characterized in that: the vertical edge of the lower pressing head and the inner wall of the outer ring of the upper pressing head adopt a sliding fit. 10. A method for expanding the diameter of a shape memory alloy pipe joint based on an elastic medium, characterized in that: (1) The expansion device of the shape memory alloy pipe joint based on the elastic medium is adopted to expand the diameter, and the described expansion device of the shape memory alloy pipe joint based on the elastic medium comprises a backing plate, a fixing plate, an upper pressing head, a lower pressing head, Spring, elastic rod, elastic ring, punch, the upper pressing head is installed on the lower pressing head, one end of the elastic rod is installed in the lower pressing head, the other end of the elastic rod is installed in the upper pressing head, the elastic ring is set on the elastic rod, and the fixing plate Connected with the backing plate, the upper pressing head is connected to the fixing plate and the backing plate through bolts, a spring is installed on the bolt, one end of the spring is connected to the fixing plate, the other end of the spring is connected to the lower pressing head, one end of the punch is installed in the fixing plate, and the punch The other end of the lower pressure head is installed in the lower pressure head and connected with the elastic rod; firstly, the expansion device of the shape memory alloy pipe joint based on the elastic medium is placed on the working table of the press machine, and after the center is aligned, the pressure plate is used to press the protrusion of the lower pressure head Then fix the lower pressing head on the workbench, start the press to make the upper slider move down to contact with the backing plate, then use the pressure plate to press the flange of the backing plate, and fix the backing plate mold on the press On the slider, start the press to move the upper slider upward, and stop the upward movement of the slider when the open space of the upper and lower parts is enough to put the workpiece; (2) Put the shape memory alloy tube blank on the elastic ring, make the lower end of the shape memory alloy tube blank contact the surface of the lower pressure head, and then start the press to move the backing plate downward, when the upper pressure head and the lower pressure head After the shape memory alloy tube blank contacts, it stops moving due to the obstruction of the shape memory alloy tube blank. At this time, as the backing plate continues to descend, the upper pressing head will press the elastic ring and the shape memory alloy tube blank under the elastic force of the spring. The upper end is pressed, and as the punch moves down, the elastic rod will bulge locally in the radial direction at the part in contact with the elastic ring, thereby driving the elastic ring to bulge radially together with it, and this radial force will be transmitted Give the shape memory alloy tube blank that is set outside the elastic ring to make it expand in diameter and bulge as a whole; (3) Open the backing plate and the lower pressure head to make it return to the position before loading. At this time, the elastic rod and elastic ring return to the state before deformation after the external force is removed, and the formed workpiece is taken out to complete the diameter expansion.

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