Pulling-out force test device and method for expanded connection simulation test piece

Abstract

The invention provides a pulling-out force test device and method for an expanded connection simulation test piece. The expanded connection simulation test piece comprises a heat exchange tube test piece and a tube plate test piece which are connected through expanded connection; the pulling-out force test device comprises a clamping tool and a stretching tool. Wherein the clamping tool comprises a support, a clamping jaw and a fastening bolt, and the support is fixed to the pulling-out force testing machine; the clamping jaws are fixedly connected to the bracket and are uniformly distributed along the periphery of the tube plate test piece; threaded holes are formed in the clamping jaws, and the fastening bolts penetrate through the threaded holes to abut against the tube plate test piece; the stretching tool comprises a clamping part and a plugging part, the diameter of the clamping part is smaller than the inner diameter of the heat exchange tube test piece, and the clamping part is configured to be inserted into the heat exchange tube test piece to apply pulling force when the pulling-out force test is executed; the diameter of the plugging part is larger than the inner diameter of the heat exchange tube test piece, and the plugging part is configured to prevent the stretching tool from being separated from the heat exchange tube test piece when the pulling-out force test is executed. The pulling-out force test device provided by the invention is suitable for executing pulling-out force tests on heat exchangers with different diameters.

Description

Technical Field

[0001] The present application relates to the technical field of pull-off force tests for expansion joint heat exchangers, and more specifically, the present application relates to a pull-off force test device and method for expansion joint simulation specimens. Background Art

[0002] The connection joint between the heat exchange tube and the tube sheet has always been the most prone to failure in heat exchangers. Currently, the commonly used connection techniques include welding, expansion jointing, and expansion welding combined. Among them, the expansion jointing techniques include mechanical expansion jointing, hydraulic expansion jointing, etc. Hydraulic expansion jointing is increasingly used because it has the advantages of no mechanical damage to materials, precise control of the expansion depth, short expansion jointing process time, and easy calculation.

[0003] The pull-off force test is a common mechanical test for evaluating the expansion jointing performance and determining the expansion jointing parameters. However, due to the different materials and sizes of the heat exchange tube and the tube sheet, and the reasons that the applicable range of the original clamping components of the conventional pull-off force testing machine is small and the applied clamping force is uneven, it is difficult for the conventional pull-off force testing machine to perform accurate and reliable pull-off force tests on heat exchange tubes and tube sheets of various sizes and materials. Summary of the Invention

[0004] In view of this, the present application provides a pull-off force test device and method for expansion joint simulation specimens. The pull-off force test device can adaptively clamp expansion joint simulation specimens of various sizes, and the pull-off force test device has a unique circumferential force structure, avoiding test errors caused by uneven force.

[0005] The present application provides a pull-off force test device for expansion joint simulation specimens. The expansion joint simulation specimen includes a heat exchange tube specimen and a tube sheet specimen connected by expansion jointing; the pull-off force test device includes a clamping tooling and a stretching tooling; wherein the clamping tooling includes a bracket, a claw, and a fastening bolt. The bracket is fixed to the pull-off force testing machine; the claw is fixedly connected to the bracket and is evenly arranged along the outer circumference of the tube sheet specimen; a threaded hole is provided on the claw, and the fastening bolt passes through the threaded hole and abuts against the tube sheet specimen; the stretching tooling includes a clamping part and a blocking part. The diameter of the clamping part is smaller than the inner diameter of the heat exchange tube specimen and is configured to be inserted into the heat exchange tube specimen to be applied with a pulling force during the pull-off force test; the diameter of the blocking part is larger than the inner diameter of the heat exchange tube specimen and is configured to prevent the stretching tooling from detaching from the heat exchange tube specimen during the pull-off force test.

[0006] Optionally, the end of the fastening bolt is coated with an anti-slip layer.

[0007] Optionally, the anti-slip layer is made of anti-slip rubber.

[0008] Optionally, the anti-slip layer is coated on the end of the fastening bolt in a detachable manner.

[0009] Optionally, the tube sheet specimen is provided with threaded holes corresponding to the fastening bolts for screwing in the fastening bolts.

[0010] Optionally, the outer periphery of the clamping part of the tensile tooling is coated with an anti-slip layer.

[0011] Optionally, the clamping part of the tensile tooling is also coated with a force-expanding layer at a position corresponding to the fastening bolts.

[0012] Optionally, a pressure gauge is further provided between the fastening bolt and the tube sheet specimen.

[0013] The present application also provides a method for performing a pull-off force test using the above pull-off force test device. The method includes the following steps: preparing a simulated expansion specimen based on the minimum expansion pressure calculated theoretically, and performing a pull-off force test on the simulated expansion specimen; gradually increasing the expansion pressure and preparing multiple simulated expansion specimens, and performing pull-off force tests on the multiple simulated expansion specimens respectively; and determining the optimal expansion pressure based on the relationship between the expansion pressure and the results of the pull-off force test.

[0014] Compared with the prior art, the pull-off force test device and method provided by the present application have the following beneficial effects:

[0015] (1) The pull-off force test device provided by the present application includes a clamping tooling with an adjustable fastening range. The clamping tooling uses claws and fastening bolts uniformly arranged along the outer periphery of the tube sheet specimen to fix simulated expansion specimens of various diameters. It has a wide application range and can apply a uniform clamping force circumferentially, effectively avoiding the pull-off force test error caused by uneven stress on the specimen to be tested.

[0016] (2) The end of the fastening bolt can be coated with an anti-slip layer. The anti-slip layer not only prevents the possible slipping phenomenon during the pull-off force test, but also avoids damaging the outer surface of the tube sheet specimen of the simulated expansion specimen. Further, the anti-slip layer can be made of anti-slip rubber. The anti-slip rubber provides anti-slip performance and also provides a certain elasticity to disperse and buffer stress, avoiding excessive local stress after the bolt is fastened and damaging the simulated expansion specimen. At the same time, it has a certain compensating effect on the small defects or unevenness of the outer surface of the tube sheet specimen, ensuring uniform distribution of the clamping force and improving the test accuracy.

[0017] (3) The outer periphery of the clamping part of the tensile tooling can also be coated with an anti-slip layer, thereby reducing the test error caused by the small gap and displacement between the tensile tooling and the heat exchange tube specimen of the simulated expansion specimen. Description of the Drawings

[0018] To more clearly illustrate the technical solutions of the present application, the embodiments of the present application will be further described and described according to the following drawings. These drawings are only used to more conveniently and specifically describe the embodiments of the present application rather than limit the present application.

[0019] Figure 1 It is a schematic structural diagram of a pull-off force test device for an expansion joint simulation specimen provided according to an exemplary embodiment of the present application;

[0020] Figure 2 is as Figure 1 shown in the schematic structural diagram of the clamping tooling of the pull-off force test device;

[0021] Figure 3 is a schematic top view of the schematic arrangement of the fastening bolts provided according to an exemplary embodiment of the present application;

[0022] Figure 4 is a schematic structural diagram of a tensile tooling of a pull-off force test device for an expansion joint simulation specimen provided according to an exemplary embodiment of the present application; and

[0023] Figure 5 is as Figure 4 shown in the schematic connection structure diagram of the tensile tooling and the expansion joint simulation specimen.

[0024] In the figure: 1 is a heat exchange tube specimen, 2 is a tube sheet specimen, 3 is a bracket, 4 is a clamping jaw, 5 is a fastening bolt, and 6 is a tensile tooling. Specific Embodiments

[0025] The present application provides a pull-off force test device and method for an expansion joint simulation specimen. The pull-off force test device can adaptively clamp expansion joint simulation specimens of various sizes, and the pull-off force test device has a unique circumferential force-bearing structure, avoiding test errors caused by uneven force.

[0026] In a preferred embodiment of the present application, a pull-off force test device for an expansion joint simulation specimen is provided. For example, refer to Figure 1 . As Figure 1 shown, the expansion joint simulation specimen includes a heat exchange tube specimen 1 and a tube sheet specimen 2 connected by expansion joint; the pull-off force test device includes a clamping tooling and a tensile tooling 6. Refer to Figure 1 and Figure 2, the clamping tooling includes a bracket 3, a jaw 4, and a fastening bolt 5. Among them, the bracket 3 is fixed to the pull-off force testing machine; specifically, the bracket 3 is fixed in the original clamping component of the conventional pull-off force testing machine, replacing the position where the expansion joint simulation specimen should be located. The diameter and preparation material of the bracket 3 can be selected according to the size and performance of the original clamping component of the conventional pull-off force testing machine, so as to be firmly clamped by the original clamping component. The jaw 4 is fixedly connected to the bracket 3 and is evenly arranged along the outer circumference of the tube sheet specimen 2; a threaded hole is provided on the jaw 4, and the fastening bolt 5 passes through the threaded hole and abuts against the tube sheet specimen 2, thereby firmly fastening the entire expansion joint simulation specimen to the conventional pull-off force testing machine for performing the pull-off force test. In a preferred embodiment of the present application, 4, 6, or 8 jaws 4 and the corresponding fastening bolts 5 can be evenly arranged on the outer circumference of the tube sheet specimen 2 to clamp the tube sheet specimen 2; in a specific embodiment, 4 jaws 4 and the corresponding fastening bolts 5 are evenly arranged on the outer circumference of the tube sheet specimen 2, as Figure 3 shown. For simplicity, Figure 3 other components are not shown in Figure 4 . Referring to Figure 5 , the tensile tooling 6 includes a clamping portion and a plugging portion, wherein the diameter of the clamping portion is smaller than the inner diameter of the heat exchange tube specimen 1, and the diameter of the plugging portion is larger than the inner diameter of the heat exchange tube specimen 1. Figure 5As shown, the clamping portion of the stretching tooling 6 is configured to be inserted into the heat exchange tube specimen 1 and subjected to a tensile force during the execution of the pull-off force test, and the sealing portion is configured to prevent the stretching tooling 6 from detaching from the heat exchange tube specimen 1 during the execution of the pull-off force test, so as to correctly measure the pull-off force of the heat exchange tube specimen 1 being pulled out from the tube sheet specimen 2. The clamping components of conventional pull-off force testing machines have limited application ranges and are difficult to clamp expansion joint simulation specimens with overly large or small diameters; moreover, the application directions and magnitudes of the clamping components of conventional pull-off force testing machines cannot be controlled, easily resulting in uneven stress on the expansion joint simulation specimens and affecting the results of the pull-off force test. In severe cases, the expansion joint simulation specimens may be damaged due to excessive applied force. However, by using the pull-off force test device provided in this application, various expansion joint simulation specimens with different diameters and materials can be applied to a conventional pull-off force testing machine for testing. The claws 4 and fastening bolts 5 evenly arranged along the outer periphery of the tube sheet specimen 2 can ensure that the clamping force is evenly distributed on the tube sheet specimen 2, ensuring that the expansion joint simulation specimen is firmly clamped during the test. This ensures that the tensile force applied by the pull-off force testing machine can also act evenly on the heat exchange tube specimen 1, thereby effectively avoiding test errors caused by uneven stress and providing richer and more accurate data support for subsequent data analysis. Those skilled in the art can understand that during the execution of the pull-off force test of the expansion joint heat exchanger, the expansion joint simulation specimen is a test specimen prepared by simulating the heat exchange tube and tube sheet of the heat exchanger to be tested, and its parameters such as size and material are the same as those of the heat exchanger to be tested. In order not to damage the heat exchanger to be tested and optimize the heat exchanger parameters, it is easy for those skilled in the art to understand to use the expansion joint simulation specimen to execute the pull-off force test. In another embodiment, it is also possible to directly use the heat exchanger to be tested to execute the pull-off force test.

[0027] In a preferred embodiment of the present application, the end of the fastening bolt 5 is coated with an anti-slip layer. This anti-slip layer not only prevents the possible slipping phenomenon between the fastening bolt 5 and the outer surface of the tube sheet specimen 2 of the expansion joint simulation specimen during the pull-off force test, but also can avoid the wear of the tube sheet specimen 2. In a more preferred implementation, the anti-slip layer can be made of anti-slip rubber with a high coefficient of friction. The anti-slip rubber provides anti-slip performance while also providing a certain amount of elasticity to disperse and buffer the stress between the fastening bolt 5 and the tube sheet specimen 2, avoiding excessive local stress after the fastening bolt 5 is tightened and damaging the tube sheet specimen 2. At the same time, it has a certain compensating effect on the minor defects or unevenness on the outer surface of the tube sheet specimen 2, ensuring that the clamping force is evenly distributed, thereby further improving the accuracy of the pull-off force test. In a preferred embodiment of the present application, the anti-slip layer can be coated on the end of the fastening bolt 5 in a detachable manner. For example, the anti-slip layer can be coated on the end of the fastening bolt 5 using a detachable adhesive as needed, so as to select and replace a suitable anti-slip layer material according to the material of the expansion joint simulation specimen and the required clamping force and coefficient of friction.

[0028] In another preferred embodiment of the present application, the tube sheet specimen 2 is provided with threaded holes for screwing in the fastening bolts 5 at positions corresponding to the fastening bolts 5. These threaded holes can be opened during the preparation of the expansion joint simulation specimen or during the execution of the pull-off force test. The connection between the threaded holes and the fastening bolts 5 is more stable, further avoiding the possibility of loosening between the fastening bolts 5 and the tube sheet specimen 2. However, care should be taken not to damage the tube sheet specimen 2 when preparing the threaded holes, and the size and depth of each threaded hole should be consistent to avoid stress deviation.

[0029] In a preferred embodiment of the present application, the outer periphery of the clamping portion of the tensile tooling 6 can also be coated with an anti-slip layer, which can be anti-slip powder, so as to reduce the test error caused by the small gaps and displacements between the tensile tooling 6 and the heat exchange tube specimen 1 of the expansion joint simulation specimen. In another preferred embodiment of the present application, the clamping portion of the tensile tooling 6 can also be coated with a force-receiving expansion layer (for example, a compression-expansion rubber layer) at a position corresponding to the fastening bolt 5, such that when the fastening bolt 5 abuts against the outer periphery of the tube sheet specimen 2 and applies a force, the force-receiving expansion layer expands and fills the small gap between the clamping portion and the heat exchange tube specimen 1, thereby avoiding the influence of loosening or displacement between the tensile tooling 6 and the heat exchange tube specimen 1 on the pull-off force test result.

[0030] In a preferred embodiment of the present application, a pressure gauge can be further provided between the fastening bolt 5 of the clamping tooling and the tube sheet specimen 2 of the expansion joint simulation specimen to measure whether the pressure between each fastening bolt 5 and the tube sheet specimen 2 is constant, thereby further ensuring that the tube sheet specimen 2 is clamped firmly and evenly in the circumferential direction.

[0031] In a preferred embodiment of the present application, a method for performing a pull-off force test using the above pull-off force test device is further provided. The method includes the following steps: preparing a simulated expansion joint specimen based on the minimum expansion joint pressure obtained by theoretical calculation, and performing a pull-off force test on the simulated expansion joint specimen; gradually increasing the expansion joint pressure and preparing multiple simulated expansion joint specimens, and performing pull-off force tests on the multiple simulated expansion joint specimens respectively; and determining the optimal expansion joint pressure based on the relationship between the expansion joint pressure and the results of the pull-off force test. Those skilled in the art can understand that the minimum expansion joint pressure can be easily obtained by theoretical calculation according to various parameters of the heat exchange tube and the tube sheet, and thus an initial simulated expansion joint specimen for performing the pull-off force test is prepared. When performing the pull-off force test, as the tensile load applied by the pull-off force testing machine continuously increases, the heat exchange tube specimen 1 will gradually be pulled out from the tube sheet specimen 2, thereby measuring the pull-off force. Gradually increase the expansion joint pressure and prepare multiple simulated expansion joint specimens, and perform pull-off force tests on the multiple simulated expansion joint specimens respectively. As the expansion joint pressure continuously increases, the pull-off force will also gradually increase. When the pull-off force no longer increases but decreases, it indicates that excessive expansion joint pressure will increase the wall thickness reduction amount and instead reduce the strength of the expansion joint. Compare the expansion joint pressure used in the above test and the measured pull-off force to obtain the optimal expansion joint pressure suitable for the expansion joint of the heat exchanger.

[0032] A large number of specific examples are provided in the embodiments provided herein. It should be understood that these examples are only for elaborating the embodiments of the present application in detail and not for limiting the present application. The embodiments of the present application can be practiced without these specific examples. In some embodiments, the methods, structures, and / or technologies well known to those skilled in the art are not shown in detail so as not to obscure the understanding of the present application.

[0033] Although the preferred embodiments of the present application have been shown and described herein, it is readily understood by those skilled in the art that these embodiments are provided by way of example only. Those skilled in the art will now think of various variations, changes, and substitutions without departing from the present application. It should be understood that the various alternative embodiments described herein are optionally used to implement the present application. It is intended to define the scope of the present application by the claims and thereby cover the methods, structures, and their equivalents within the scope of these claims.

Claims

1. A pull-off force test device for expansion joint simulation specimens, characterized in that: The expansion simulation specimen comprises a heat exchange tube specimen (1) and a tube sheet specimen (2) connected by expansion; The pull-off force testing device comprises a clamping tool and a stretching tool (6); The clamping tool comprises a bracket (3), a clamping claw (4) and a fastening bolt (5). The bracket (3) is fixed to a pull-off force testing machine; The clamping claws (4) are fixedly connected to the bracket (3) and are evenly arranged along the outer circumference of the tube sheet specimen (2); The clamping claw (4) is provided with a threaded hole, and the fastening bolt (5) passes through the threaded hole and abuts against the tube sheet test piece (2); The stretching tool (6) comprises a clamping portion and a blocking portion, The diameter of the clamping portion is smaller than the inner diameter of the heat exchange tube specimen (1) and is configured to be inserted into the heat exchange tube specimen (1) and subjected to a tensile force when performing a pull-off force test; The diameter of the sealing portion is greater than the inner diameter of the heat exchange tube specimen (1) and is configured to prevent the tensile fixture (6) from detaching from the heat exchange tube specimen (1) when performing a pull-off force test.

2. The pull-off force testing device according to claim 1, characterized in that: The end of the fastening bolt (5) is coated with an anti-slip layer.

3. The pull-off force testing device according to claim 2, characterized in that: The anti-skid layer is made of anti-skid rubber.

4. The pull-off force testing device according to claim 2, characterized in that: The anti-slip layer is coated on the end of the fastening bolt (5) in a detachable manner.

5. The pull-off force testing device according to claim 1, characterized in that: The tube sheet test piece (2) is provided with a threaded hole for screwing the fastening bolt (5) at a position corresponding to the fastening bolt (5).

6. The pull-off force testing device according to claim 1, characterized in that: The outer periphery of the clamping portion of the stretching tool (6) is coated with an anti-slip layer.

7. The pull-off force testing device according to claim 1, characterized in that: The clamping portion of the stretching tool (6) is also coated with a stress expansion layer at a position corresponding to the fastening bolt (5).

8. The pull-off force testing device according to claim 1, characterized in that: A pressure gauge is further provided between the fastening bolt (5) and the tube sheet test piece (2).

9. A method for performing a pull-off force test using the pull-off force test device according to any one of claims 1 to 8, characterized in that: The following steps are involved: preparing the expansion joint simulation specimen based on the theoretically calculated minimum expansion joint pressure, and performing a pull-off force test on the expansion joint simulation specimen; gradually increasing the expansion pressure and preparing a plurality of the expansion simulation specimens, and performing the pull-off force test on the plurality of the expansion simulation specimens respectively; as well as Based on the relationship between the expansion pressure and the results of the pull-off force test, an optimum expansion pressure is determined.

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