CN113624602B - Experimental device and construction method of the curve in the right area of the tube forming limit diagram - Google Patents

Abstract

The invention provides an experimental device and a construction method for the curve of the right area of the pipe forming limit diagram. It is spaced from the second positioning die, and further includes a strain path defining cylinder group, the strain path defining cylinder group includes a plurality of elliptical hole path defining barrels having elliptical holes of different sizes, any one of the plurality of elliptical hole path defining barrels can be replaced It is sleeved on the outer peripheral wall of the test tube between the first positioning mold and the second positioning mold. According to the present invention, the forming limit measurement of the test pipe under a wide range of double tensile strain state is realized, the linearity of the loading path can be ensured, and the test pipe under the double tensile strain state can be controlled by changing the position of the elliptical hole path limiting cylinder Deformation capacity analysis of local defect areas such as welds is carried out in a targeted manner.

Description

Experimental device and construction method of the curve in the right area of the tube forming limit diagram

technical field

The invention belongs to the technical field of metal pipe forming performance evaluation, and in particular relates to an experimental device and a construction method for a curve in the right area of a pipe forming limit diagram.

Background technique

Tube hydroforming technology is an advanced integral forming technology for tube parts. Its products can be applied to fields such as aerospace, nuclear energy engineering, and automotive engineering, making important contributions to lightweighting and manufacturing upgrades. The hydroforming process of the pipe is roughly as follows: first, the pipe blank is put into the mold, and a certain clamping force is applied to the mold to keep its internal cavity fixed, so that the interior of the pipe blank is filled with liquid, and then the internal pressure and axial feeding are reasonably controlled. Quantity to form parts with required complex shapes. The parts formed by this technology have the advantages of less welds, fewer parts, and high precision. However, with the needs of process upgrades, the shapes of parts are becoming more and more complex, and accurate tube forming limit diagrams are more and more important for part design and process development. important.

Different from sheet, it is difficult to obtain forming limit test results in the range of full strain ratio β due to the constraints of tube shape, and it is more difficult to achieve an ideal linear loading path. The main problem with the current forming limit construction method and device is that the strain ratio β range of the forming limit diagram obtained from the experiment is not complete enough, especially the obtained forming limit diagram is not the forming limit data under the ideal linear path. The influence of the strain path on the forming limit cannot be ignored, so the results obtained by the existing pipe forming limit construction methods have limitations in guiding the analysis of the actual pipe forming process.

SUMMARY OF THE INVENTION

Therefore, the present invention provides an experimental device and a construction method for the curve of the right area of the pipe forming limit diagram. A series of elliptical hole paths with different elliptical hole sizes are used to define the cylinder, so as to realize the double tensile strain state of the test pipe in a wide range. It is possible to measure the forming limit under the oval hole, and to ensure the linearity of its loading path. It can also control the rupture position of the test tube under the double tensile strain state by changing the position of the elliptical hole path limiting cylinder, and target the local defect areas such as welds. Deformation capability analysis.

In order to solve the above problems, the present invention provides an experimental device for the curve of the right area of the pipe forming limit diagram, including a first positioning mold and a second positioning mold for positioning the length ends of the test pipe respectively. The first positioning mold spaced from the second positioning die, and further comprising a strain path defining cylinder group comprising a plurality of elliptical hole path defining barrels having elliptical holes of different sizes, the plurality of elliptical hole paths Either of the confinement cylinders may alternatively be nested on the peripheral wall of the test tube between the first and second positioning dies.

Preferably, the long axes of the elliptical holes respectively provided on the plurality of the elliptical hole path-defining cylinders are equal, and the short axes thereof are not equal.

Preferably, the strain path limiting cylinder group further includes a circular hole path limiting cylinder with a circular hole, and the equal circular hole path limiting cylinder is alternatively sleeved between the first positioning die and the second positioning die on the outer peripheral wall of the test tube; and/or, the ratio between the major axis and the minor axis of the elliptical holes respectively provided on the plurality of elliptical hole path-defining cylinders is between 1:1 and 5:1.

Preferably, the oval hole near the opening of the test tube is chamfered or rounded.

Preferably, the short axes respectively possessed by the plurality of elliptical holes and the radius of the circular holes form an increasing arithmetic progression; and/or, the long axes are located in the ring upward of the test tube, and the short axes in the axial direction of the test tube.

Preferably, the elliptical hole path defining cylinder includes a first non-porous portion and a first perforated portion that are fastened to each other to form a full circle, and the equi-circular hole path defining barrel includes a second non-porous portion that is fastened to each other to form a full circle and/or, further comprising a mold positioning structure for fixing the distance between the first positioning mold and the second positioning mold.

Preferably, the experimental device further includes a cylinder-defining support member, which is supported on the bottom of the strain-path-defining cylinder group; and/or the first positioning mold includes a first upper mold half and a first lower mold half, so The first upper mold half and the first lower mold half are fastened together by a first concave-convex structure; and/or the second positioning mold includes a second upper mold half and a second lower mold half, the second upper mold The mold half and the second lower mold half are fastened through the second concave-convex structure.

Preferably, the experimental device further comprises a first push rod corresponding to the opening of the first end of the test tube, the end of the first push rod has a first sealing head, and the first sealing head can extend into The first end opening pair forms a closure for the first end opening; and/or, further includes a second push rod corresponding to the second end opening of the test tube, and the end of the second push rod is There is a second sealing head that can extend into the second end opening pair to form a closure to the second end opening.

Preferably, the first sealing head is detachably connected to the end of the first push rod, and the second sealing head is detachably connected to the end of the second push rod; and/or, the first The axial sections of a sealing head and the second sealing head are isosceles trapezoids.

The present invention also provides a method for constructing a curve in the right area of the pipe forming limit diagram, which is carried out by using the above-mentioned experimental device for the curve in the right area of the pipe forming limit diagram, including the following steps:

The strain path defining step is to select a circular hole path limiting cylinder in the strain path limiting cylinder group to be sleeved on the test pipe, and adjust the circular hole of the circular hole path limiting cylinder to be in the target testing area of the test pipe ;

The positioning step is to fix the test tube between the first positioning mold and the second positioning mold;

The loading test step is to seal the openings at both ends of the test tube and inject pressure fluid into the test tube until the test tube is deformed and ruptured, during which the primary strain data and the secondary strain data of the target test area are tested and recorded;

Replacing the test step, replacing the test tube material, and sequentially selecting the elliptical hole path defining cylinder from the strain path defining cylinder group in the order of the short axes of the elliptical holes respectively possessed by the elliptical hole path defining cylinders from the longest to the shortest order before the replacement. The circular hole path limiting cylinder or the elliptical hole path limiting cylinder is sleeved on the replaced test tube, and the positioning step and the loading test step are repeated;

Steps for drawing the curve of the right area of the tube forming limit diagram, confirm the limit primary and secondary strain values under each strain path, and draw the right area curve of the tube forming limit diagram according to the limit primary and secondary strain values under each strain path.

The invention provides an experimental device and a construction method for the curve of the right area of the pipe forming limit diagram. A series of elliptical holes with different sizes of elliptical holes are used to define the path of the cylinder, so as to realize the forming of the test pipe under a wide range of double tensile strain states. The limit measurement can ensure the linearity of its loading path. It can also control the rupture position of the test tube under the double tensile strain state by changing the position of the elliptical hole path limiting cylinder, and analyze the deformation capacity of the local defect area such as the weld. , has the characteristics of simple shape, low implementation cost and good measurement effect.

Description of drawings

Fig. 1 is the structural schematic diagram (section) of the experimental device of the curve of the right area of the pipe forming limit diagram according to the embodiment of the present invention;

Fig. 2 is a specific example of the elliptical hole and the circular hole possessed by each limiting cylinder in the strain path limiting cylinder group;

3 is a schematic three-dimensional structural diagram of an experimental device of the curve of the right area of the pipe forming limit diagram according to the embodiment of the present invention;

Fig. 4 is the curve of the right area of the pipe forming limit diagram constructed by the construction method of the present invention, the main strain in the figure corresponds to the hoop strain at the target test area of the test pipe, and the secondary strain corresponds to the target of the test pipe Axial strain at the test area.

Reference numerals are indicated as:

1. The first positioning mold; 2. The second positioning mold; 31. The oval hole path limiting cylinder; 41, the oval hole; 62. Second sealing head; 7. Die positioning structure; 8. Limiting cylinder support; 100. Testing pipe.

Detailed ways

Referring to FIG. 1 to FIG. 4 , according to an embodiment of the present invention, an experimental device for the curve of the right area (also called the first quadrant) of the pipe forming limit diagram is provided, which includes forming the two ends of the length of the test pipe 100 respectively. The first positioning mold 1 and the second positioning mold 2 are positioned. Specifically, the first positioning mold 1 has a first positioning hole (not shown in the figure) that matches the test pipe 100. The second positioning mold 2 has a second positioning hole (not shown in the figure) matching the test tube 100, the first positioning mold 1 and the second positioning mold 2 are spaced apart and pass through the first positioning hole and the second positioning mold 2 respectively. The second positioning hole forms the positioning of the test tube 100, and further includes a strain path defining cylinder group, the strain path defining cylinder group includes a plurality of elliptical hole path defining cylinders 31 having elliptical holes 41 of different sizes, the plurality of Either one of the elliptical hole path-defining cylinders 31 can be alternatively sleeved on the outer peripheral wall of the test tube 100 between the first positioning die 1 and the second positioning die 2, each elliptical The hole path defining cylinder 31 can rotate along the circumferential direction (ie, the circumferential direction) of the test tube 100 to adjust the position of the elliptical hole 41 relative to the test tube 100 , for example, to avoid the position of the test tube 100 . position of the welding seam, and enable the elliptical hole 41 to face the position of the corresponding strain measuring device. In this technical solution, a series of elliptical holes with different sizes of elliptical holes are used to define the path of the cylinder, so as to realize the forming limit measurement of the test pipe under a wide range of double tensile strain states, and to ensure the linearity of its loading path. The position of the elliptical hole path defines the tube to control the rupture position of the test tube under the double tensile strain state, and the deformation capacity analysis of local defect areas such as welds is carried out in a targeted manner. It has the characteristics of simple shape, low implementation cost and good measurement effect. Specifically, by replacing and sheathing a plurality of elliptical hole path limiting cylinders with elliptical holes of different sizes on the outer circumference of the test pipe, the controllable limitation of the deformation path of the pipe is realized, and the control of measuring the deformation of different target positions of the pipe until the rupture is realized. , the strain path is more ideal and linear, and with the corresponding strain detection device, the forming limit data under different strain paths can be obtained, and then the curve of the right area of the pipe forming limit diagram can be constructed.

It should be noted that the experimental device is usually used in conjunction with a hydraulic bulging machine in the industry during use. Specifically, the hydraulic bulging machine has a working platform on which the entire experimental device is installed. , the first positioning mold 1 includes a first upper mold half and a first lower mold half, and the second positioning mold 2 includes a second upper mold half and a second lower mold half, wherein the first lower mold half and The second lower mold half can be fixedly connected to the working platform respectively, so as to achieve a reliable and stable distance between the two, and the first upper mold half and the second upper mold half are respectively fixed to the hydraulic bulge. The upper beam plate of the machine, thus, the hydraulic bulging machine can control (specifically, it is beneficial to the movement of the main cylinder of the hydraulic bulging machine) the clamping and The mold opening and the mold closing and mold opening of the second upper mold half and the second lower mold half, so as to realize the extraction and loading of different test tubes 100 .

Preferably, the first upper mold half and the first lower mold half are fastened together by a first concave-convex structure, and the second upper mold half and the second lower mold half are fastened together by a second concave-convex structure. For example, the two matched mold halves are made into yin and yang types, so that the upper and lower mold halves remain relatively fixed in the horizontal direction after the molds are closed to avoid misalignment under the action of side thrust.

In some embodiments, the long axes of the elliptical holes 41 respectively provided on the plurality of the elliptical hole path defining cylinders 31 are equal, and the short axes are not equal, so as to ensure the linearity of the deformation path; The ratio between the major axis and the minor axis of the elliptical holes 41 on each of the elliptical hole path limiting cylinders 31 is between 1:1 and 5:1, so as to ensure that the equal double tensile strain state is covered. As shown in FIG. 4 , when the ratio between the long axis and the short axis of the elliptical hole 41 on the elliptical hole path definition cylinder 31 is 3:1 (that is, an ellipse with a short axis of 10 mm and a long axis of 30 mm) Hole) test to obtain the result that the strain ratio is 1, thus realizing the acquisition of equal double tensile strain state. In the conventional double tensile strain test experiment of pipe fittings, the two ends of the pipe are constrained to bulge the pipe, and the characteristic hoop strain of the pipe is significantly larger than the axial strain, so the strain ratio is far less than 1, and because the deformation area is The strain paths are all nonlinear. In this technical solution, the deformation of the tube is limited in a small area by the arrangement of the elliptical hole, thereby effectively improving the linearity of the strain path; by gradually reducing the length of the short axis of the elliptical hole, the axial strain of the tube is increased, and the axial strain of the tube is gradually increased. The strain ratio approaches 1.

In the experimental device of the present invention, the strain path limiting cylinder group further includes a circular hole path limiting cylinder (not shown in the figure, not indexed) having a circular hole 42, and the circular hole path limiting cylinder is replaced by a sleeve on the outer peripheral wall of the test tube 100 between the first positioning mold 1 and the second positioning mold 2 .

In some embodiments, the long axis of the elliptical hole 41 is equal to the diameter of the circular hole 42 ; further, the short axis of each of the elliptical holes 41 and the radius of the circular hole 42 increase in sequence. The arithmetic sequence of ; the long axis is in the annular direction of the test tube 100 , and the short axis is in the axial direction of the test tube 100 . Referring specifically to FIG. 2 , the elliptical hole path limiting cylinder 31 has a total of 4, each of which is respectively constructed with an elliptical hole, their long axes are all 30mm, but their short axes are 10mm, 15mm, 20mm respectively , 25mm, in the specific test and construction process, according to the sequence shown in Figure 2, the circular hole path limiting tube can be first fitted, and then the elliptical hole path limiting tube can be fitted in sequence, and the short axis of the elliptical hole 41 is replaced by the more Shorter (25mm to 10mm), until the test results in a strain ratio of 1, which can facilitate the construction of a forming limit diagram where the strain ratio β undergoes a linear strain path of 0-1.

Preferably, the opening of the elliptical hole 41 close to the test tube 100 is chamfered or rounded, and the circular hole 42 close to the opening of the test tube 100 is chamfered or rounded, which can effectively prevent the The stress concentration of the test tube 100 at the opening of the elliptical opening 41 or the circular hole 42 is prevented from being cut off during the deformation process and affecting the accuracy of the strain test result.

As a specific implementation of the elliptical hole path defining cylinder 31 or the equi-circular hole path defining cylinder, the elliptical hole path defining cylinder 31 includes a first non-hole portion (not indexed in the figure) that is fastened to each other to form a full circle. ), the first perforated portion (not indexed in the figure), and the equal-circular hole path limiting cylinder includes a second non-perforated portion (not indexed in the figure), a second perforated portion ( (not indexed in the figure), that is, the elliptical hole path limiting cylinder 31 or the equal circular hole path limiting cylinder are respectively detachable and assembled components, which can facilitate the replacement of each limiting cylinder during the entire test construction process and improve the test construction. efficiency.

In some embodiments, the experimental device further includes a mold positioning structure 7 for fixing the distance between the first positioning mold 1 and the second positioning mold 2, which may be, for example, some with locking The pressing plate, pressing strip, etc. of the hole can be fixedly connected with the working platform through bolts.

In some embodiments, the experimental device further includes a cylinder-defining support 8, which is supported on the bottom of the strain-path-defining cylinder group. The shape of the outer wall of the cylinder that defines the cylinder is matched. For example, when the outer wall of the cylinder is circular, a semi-circular cavity is constructed on the supporting member 8 of the limiting cylinder to ensure that the elliptical hole path is limited during the pressurization deformation process. The barrel or iso-circular hole path defines the positional stability of the barrel. Preferably, two sets of the limiting cylinder supports 8 are provided, corresponding to the positions of the first positioning mold 1 and the second positioning mold 2, respectively, so as to form the elliptical hole path limiting cylinder 31 and the circular hole path limiting cylinder. Balanced supports at both ends of the shaft.

In some embodiments, the experimental device further includes a first push rod 51 corresponding to the opening of the first end of the test tube 100, the end of the first push rod 51 has a first sealing head 52, the The first sealing head 52 can extend into the first end opening to form a closure for the first end opening, and further includes a second push rod 61 corresponding to the second end opening of the test tube 100 . The end of the second push rod 61 has a second sealing head 62 , the second sealing head 62 can extend into the second end opening to form a closure to the second end opening, so that the test tube 100 is closed to the second end opening. The inner cavity forms a sealed cavity, which is convenient for pressurization after being filled with external pressure fluid (such as water or hydraulic oil, etc.). Preferably, the first sealing head 52 is detachably connected to the end of the first push rod 51, and the second sealing head 62 is detachably connected to the end of the second push rod 61, so as to facilitate The first sealing head 52 or the second sealing head 62 can be replaced with corresponding force-applying components under some tension-compression conditions, so as to further enrich the effect of the experimental device of the present invention. In some embodiments, the axial cross-sections of the first sealing head 52 and the second sealing head 62 are isosceles trapezoids, that is, the first sealing head 52 and the second sealing head 62 have a truncated cone structure , this structure can form a reliable seal with the inner hole wall of the test tube 100 by its own formation. Both the first push rod 51 and the second push rod 61 can approach or move away from the test pipe 100 along the axial direction of the test pipe 100 under the control of the hydraulic bulging machine.

According to an embodiment of the present invention, there is also provided a method for constructing the curve of the right area of the pipe forming limit diagram, which is carried out by using the above-mentioned experimental device of the curve of the right area of the pipe forming limit diagram, including the following steps:

The preparation step is to determine the length Ld of the deformation zone of the pipe, adjust the distance between the first positioning mold 1 and the second positioning mold 2 according to Ld and fix the distance, sample the test pipe 100 and print speckles or grids on the outer surface of the test pipe 100 ;

In the step of defining the strain path, the circular hole path limiting cylinder in the strain path limiting cylinder group is selected to be sleeved on the test tube 100 , and the circular hole 42 of the circular hole path limiting cylinder is adjusted to be in the position of the test tube 100 . target test area;

In the positioning step, the test tube 100 is fixed between the first positioning mold 1 and the second positioning mold 2;

In the loading test step, the two ends of the test tube 100 are sealed and the pressure fluid is injected into the test tube 100 until the test tube 100 is deformed and ruptured, during which the primary strain data and secondary strain data of the target test area are tested and recorded. strain data;

Replacing the test step, replacing the test tube 100, and selecting the elliptical hole path limiting cylinder from the strain path limiting cylinder group in order of the short axes of the elliptical holes 41 respectively possessed by the elliptical hole path limiting cylinders 31 31. The circular hole path limiting cylinder or the elliptical hole path limiting cylinder 31 before the replacement is sleeved on the replaced test tube 100, and the positioning step and the loading test step are repeated;

Steps for drawing the curve of the right area of the tube forming limit diagram, confirm the limit primary and secondary strain values under each strain path, and draw the right area curve of the tube forming limit diagram according to the limit primary and secondary strain values under each strain path.

The above method of the present invention is further described below with reference to a specific example.

The experimental object test pipe material is SAPH400, the wall thickness is 2.0mm, the pipe diameter is Φ65mm, and the pipe is straight seam welded pipe.

Step 1: Referring to the diameter of the pipe, select the length Ld of the deformation zone to be 60mm. As shown in FIG. 1 , after assembling the molds (that is, the aforementioned first positioning mold 1 and second positioning mold 2 ), connect them to the hydroforming equipment (for example, the aforementioned hydraulic bulging machine), and adjust the first positioning mold 1 The distance with the second positioning mold is 60mm, and the two molds are fixed with the mold positioning structure 7;

Step 2: According to the length Ld of the deformation zone, cut off a tube with a length of 300 mm (that is, the aforementioned test tube 100), and print speckles on the surface of the tube;

Step 3: Put the pipe into the circular hole path limiting cylinder, adjust the position of the pipe weld to avoid the area of the circular hole 42, and then place it on the lower half molds of the first positioning mold 1 and the second positioning mold 2 respectively, It is supported and fixed by the limiting cylinder support 8, and the position of the elliptical hole is adjusted to face the strain measuring device;

Step 4: Control the main cylinder of the hydraulic bulging machine to move down so that the upper mold half of the first positioning mold 1 and the second positioning mold 2 are respectively clamped with the lower mold half, and then control the first push rod 51 and the second mold at the same time. The push rod 61 seals the axial ends of the pipe;

Step 5: inject liquid into the pipe, control the pressure of the liquid, deform the pipe until it breaks, and measure the primary and secondary strain data of the deformation process in the elliptical hole area with a strain measuring device;

Step 6: As shown in Figure 2, replace the elliptical hole path limiting cylinder 31 with different hole sizes (first replace the elliptical hole path limiting cylinder with a short axis of 25mm, and then iteratively replace it with 20mm, 15mm, and 10mm), and repeat the above process to achieve The strain state under different strain paths, and the primary and secondary strain data of the deformation process in the elliptical hole region were measured respectively;

Step 7: Analyze each set of data measured above, confirm the strain path and limit primary and secondary strain values, and finally draw the limit primary and secondary strain values under each strain path into the figure to obtain the right side of the pipe forming limit diagram. The side area curve is shown in Figure 4.

The above-mentioned embodiment not only overcomes the difficulty of realizing a linear strain path in the double tensile strain zone, but also expands the strain ratio β range to 1, which realizes the double tensile strain state of the pipe and so on. Real-time monitoring of strain paths.

It can be easily understood by those skilled in the art that, on the premise of no conflict, the above advantageous manners can be freely combined and superimposed.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention. Inside. The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be It is regarded as the protection scope of the present invention.

Claims (8)

1. An experimental device for a curve on the right side of a pipe forming limit diagram, characterized in that it comprises a first positioning die (1) and a second positioning die (2) that position the length ends of the test pipe (100) respectively. , the first positioning mold (1) and the second positioning mold (2) are arranged at intervals, and further comprises a strain path limiting cylinder group, the strain path limiting cylinder group comprising a plurality of elliptical holes (41) with different sizes The elliptical hole path defining cylinder (31), any one of the plurality of the elliptical hole path defining cylinders (31) can be alternatively sleeved in the first positioning mold (1) and the second positioning mold ( 2) on the outer peripheral wall of the test tube (100) between; the long axes of the elliptical holes (41) respectively provided on the plurality of the elliptical hole path defining cylinders (31) are equal and the short axes are not equal; The long axis is in the annular direction of the test tube (100), and the short axis is in the axial direction of the test tube (100); a plurality of the elliptical hole paths define elliptical holes respectively provided on the cylinder (31) The ratio between the long axis and the short axis of (41) is between 3:1 and 5:1, so as to ensure that the equal double tensile strain state is covered; The radius of the circular hole (42) is successively formed into an increasing arithmetic progression. 2 . The experimental device according to claim 1 , wherein the strain path limiting cylinder group further comprises a circular hole path limiting cylinder having a circular hole ( 42 ), and the circular hole path limiting cylinder is sleeved in replacement. 3 . on the outer peripheral wall of the test pipe (100) between the first positioning mold (1) and the second positioning mold (2). 3. The experimental device according to claim 2, wherein the long axis of the oval hole (41) is equal to the diameter of the circular hole (42); and/or the oval hole (41) is close to The opening of the test tube (100) is chamfered or rounded, and the circular hole (42) close to the opening of the test tube (100) has a chamfer or rounding. 4 . The experimental device according to claim 2 , wherein the elliptical hole path limiting cylinder ( 31 ) comprises a first non-hole portion and a first hole portion that are mutually engaged in a full circle, and the circular hole The path-defining cylinder includes a second non-porous part and a second perforated part that are fastened together to form a full circle; and/or, further includes a mold positioning structure (7) for fixing the first positioning mold (1) and the first positioning mold (1) and the first positioning mold (1). 2. The spacing of the positioning die (2). 5. The experimental device according to claim 2, characterized in that it further comprises a limiting cylinder support (8), which is supported on the bottom of the strain path limiting cylinder group; and/or, the first positioning mold (1) ) comprises a first upper mold half and a first lower mold half, the first upper mold half and the first lower mold half are fastened together by a first concave-convex structure; and/or, the second positioning mold (2) It includes a second upper mold half and a second lower mold half, and the second upper mold half and the second lower mold half are fastened through a second concave-convex structure. 6. The experimental device according to claim 2, further comprising a first push rod (51) corresponding to the opening of the first end of the test tube (100), the first push rod (51) ) has a first sealing head (52) at its end, and the first sealing head (52) can extend into the first end opening to form a closure for the first end opening; and/or, it also includes a A second push rod (61) corresponding to the opening of the second end of the test tube (100), the end of the second push rod (61) has a second sealing head (62), the second sealing head (62) ) can extend into the second end opening to form a closure to the second end opening. 7. The experimental device according to claim 6, wherein the first sealing head (52) is detachably connected to the end of the first push rod (51), and the second sealing head (62) ) is detachably connected to the end of the second push rod (61); and/or, the axial sections of the first sealing head (52) and the second sealing head (62) are isosceles trapezoids. 8. A method for constructing the curve of the right region of the pipe forming limit diagram, characterized in that, the experiment device of the curve of the right region of the pipe forming limit diagram according to any one of claims 2 to 7 is used to carry out, comprising the steps of: The strain path defining step is to select a circular hole path limiting cylinder in the strain path limiting cylinder group to be sleeved on the test tube (100), and adjust the circular hole (42) of the circular hole path limiting cylinder to be in the the target test area of the test tube (100); In the positioning step, the test tube (100) is fixed between the first positioning mold (1) and the second positioning mold (2); In the loading test step, the two ends of the test tube (100) are sealed and the pressure fluid is injected into the test tube (100) until the test tube (100) is deformed and ruptured, during which the target test area is tested and recorded primary strain data and secondary strain data; Replacing the test step, replacing the test tube (100), and sequentially from the strain path defining cylinder group in the order of the short axes of the elliptical holes (41) respectively possessed by the elliptical hole path limiting cylinders (31) from the longest to the shortest Select the elliptical hole path limiting cylinder (31) to replace the round hole path limiting cylinder or the elliptical hole path limiting cylinder (31) to be sleeved on the replaced test tube (100), and repeat the positioning step and the loading test step ; Steps for drawing the curve of the right area of the tube forming limit diagram, confirm the limit primary and secondary strain values under each strain path, and draw the right area curve of the tube forming limit diagram according to the limit primary and secondary strain values under each strain path.

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