Method for testing mechanical properties of a brazed microstructure

Abstract

This invention discloses a method for testing the mechanical properties of brazed microstructures, relating to the field of material mechanical property testing. The method includes the following steps: designing and preparing tensile specimens and pull-out / bending plates; placing the pull-out / bending plate between upper and lower specimen plates, with the intermediate stiffener located in the opening; measuring the length and width of the weld using an optical measurement system; installing an extensometer on the tensile specimen to magnify the gauge length; using a COD gauge in conjunction with the extensometer for strain measurement; installing the upper specimen on the upper clamp of a testing machine, and installing the lower specimen and pull-out / bending plate on the lower clamp of the testing machine; performing a tensile test to obtain a stress-displacement curve, which is then converted into a stress-strain curve based on the gauge length. This method solves the problems of easy bending and thread pull-out due to the thinness of the base material, and the difficulty in strain measurement due to the small size.

Description

Technical Field

[0001] This invention relates to the field of material mechanical property testing, and in particular to a method for testing the mechanical properties of brazed microstructures. Background Technology

[0002] Brazed microstructures, due to their compact structure and small size, are widely used in many important structures in fields such as petrochemicals and aerospace. Brazed microstructures generally withstand high pressure and thermal loads, essentially bearing tensile stress or alternating thermal stress. Due to their small size, tensile performance testing of brazed microstructures is difficult, often relying on shear tests instead. However, this method cannot accurately determine the true tensile properties and load-bearing capacity of brazed microstructures, nor can it design and evaluate their lifespan under thermal fatigue conditions. This severely limits the application scope and service conditions of brazed microstructures.

[0003] Existing mechanical property tests for brazed microstructures mostly rely on shear tests to obtain shear strength. Tensile tests are only feasible for brazed structures with large dimensions (e.g., base metal thickness generally greater than 3 mm, brazed stiffener dimensions greater than 2 mm, and stiffener height exceeding 5 mm), and even then, they are uncommon. As the size of brazed structures decreases, tensile testing becomes extremely difficult. Thinning of the base metal causes bending, and the degradation of the base metal's properties during brazing leads to thread pull-out. The decreasing size makes measurement accuracy increasingly important, and strain measurement becomes very challenging. Summary of the Invention

[0004] To address the above technical problems, this invention provides a method for testing the mechanical properties of brazed microstructures, which solves the problems of easy bending and thread pull-out caused by the thinness of the base material, and the difficulty in strain measurement due to the small size.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] This invention provides a method for testing the mechanical properties of brazed microstructures, comprising the following steps:

[0007] Step 1: Design and prepare a tensile specimen. The tensile specimen includes an upper specimen plate, an intermediate stiffener plate, and a lower specimen plate. The upper specimen plate and the intermediate stiffener plate are an integral structure. The end of the intermediate stiffener plate away from the upper specimen plate is welded to the lower specimen plate, and a weld is formed between the intermediate stiffener plate and the lower specimen plate.

[0008] Step 2: Design and prepare a tensile-detachable and bending-resistant plate. The tensile-detachable and bending-resistant plate has an opening on one side. The tensile-detachable and bending-resistant plate is placed between the upper test plate and the lower test plate, with the intermediate stiffener plate located in the opening.

[0009] Step 3: Use an optical measurement system to determine the length and width of the weld.

[0010] Step 4: Install the extensometer on the tensile specimen. The extensometer is used to enlarge the gauge length of the tensile specimen. Use a COD gauge in conjunction with the extensometer to perform strain measurement.

[0011] Step 5: Install the upper test plate on the upper clamp of the testing machine, and install the lower test plate and the tensile-bending plate on the lower clamp of the testing machine. Perform a tensile test to obtain the stress-displacement curve, and convert it into a stress-strain curve based on the gauge length.

[0012] Optionally, in step one, the upper test plate is provided with two first threaded hole groups, the two first threaded hole groups are symmetrically arranged with respect to the weld, and each first threaded hole group includes a plurality of first threaded holes arranged sequentially along the length direction of the weld; the lower test plate is provided with two second threaded hole groups, the two second threaded hole groups are symmetrically arranged with respect to the weld, and each second threaded hole group includes a plurality of second threaded holes arranged sequentially along the length direction of the weld.

[0013] Optionally, in step one, a first plate body with multiple spaced strips on one side is prepared. The strips are integral with the first plate body. The ends of each strip away from the first plate body are welded to the second plate body. The position of the weld is marked. According to the designed tensile test specimen, the first threaded hole is processed on the first plate body, and the second threaded hole is processed on the second plate body. Then, the upper test plate, the lower test plate, and the intermediate plate between the upper and lower test plates are cut by wire cutting. At this time, the two ends of the intermediate plate are flush with the two ends of the upper and lower test plates. Then, according to the length requirements of the weld, the two ends of the intermediate plate are wire cut to form the intermediate stiffener, thereby preparing the tensile test specimen.

[0014] Optionally, in step two, the anti-pull-out and anti-bending plate is provided with two third threaded hole groups, the two third threaded hole groups are symmetrically arranged with respect to the opening, and each third threaded hole group includes a plurality of third threaded holes arranged sequentially along the length direction of the opening, and the third threaded holes are arranged one-to-one with the second threaded holes.

[0015] Optionally, the first threaded hole group includes two first threaded holes, the second threaded hole group includes two second threaded holes, and the third threaded hole group includes two third threaded holes.

[0016] Optionally, in step four, the drawing device includes two symmetrically arranged drawing plates. Each drawing plate includes a first horizontal plate, a vertical plate, and a second horizontal plate. The first horizontal plate is connected to one side of the lower part of the vertical plate, and the second horizontal plate is connected to the other side of the upper part of the vertical plate. The end of the first horizontal plate of one drawing plate away from the vertical plate is attached to the side of the upper test plate near the lower test plate, and the end of the first horizontal plate of the other drawing plate away from the vertical plate is attached to the side of the lower test plate near the upper test plate. The COD gauge is inserted between the two second horizontal plates.

[0017] Optionally, in step five, the upper clamp includes a first connecting plate and a first stud disposed on one side of the first connecting plate. The first connecting plate is provided with first mounting holes corresponding one-to-one with the first threaded holes. Multiple first connecting bolts are used to connect the first connecting plate to the upper test plate, so that each first connecting bolt is installed from the first mounting hole into the first threaded hole. The lower clamp includes a second connecting plate and a second stud disposed on one side of the second connecting plate. The second connecting plate is provided with second mounting holes corresponding one-to-one with the second threaded holes. Multiple second connecting bolts are used to connect the second connecting plate, the lower test plate, and the tensile-detachable and bending-resistant plate, so that each second connecting bolt is installed from the second mounting hole into the second threaded hole and the third threaded hole, thereby completing the installation of the tensile specimen.

[0018] Optionally, the test also includes step six, which involves analyzing and measuring the elongation of the fractured tensile specimen to complete the mechanical property test.

[0019] The present invention achieves the following technical effects compared to the prior art:

[0020] The present invention discloses a method for testing the mechanical properties of brazed microstructures. An opening is provided on one side of a tensile-detachment and bending-resistant plate. The tensile-detachment and bending-resistant plate is placed between an upper test plate and a lower test plate, with the intermediate stiffener located within the opening. The upper test plate is mounted on the upper clamp of a testing machine, and the lower test plate and the tensile-detachment and bending-resistant plate are mounted on the lower clamp of the testing machine. A tensile test is performed to obtain a stress-displacement curve, which is then converted into a stress-strain curve based on the gauge length. In this invention, the lower test plate is the base material, which is relatively thin. By providing a tensile-detachment and bending-resistant plate on one side of the lower test plate and connecting both to the lower clamp, the problems of bending and thread pull-out caused by the thin base material are solved. The extensometer in this invention is used to enlarge the gauge length of the tensile specimen. A COD gauge is used in conjunction with the extensometer for strain measurement, thereby obtaining accurate strain and solving the problem of difficulty in strain measurement due to small dimensions. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram illustrating the working process of the mechanical property testing method for brazed microstructures provided by the present invention;

[0023] Figure 2 This is a schematic diagram of the working process of the drawing device in the mechanical property testing method for brazed microstructures provided by the present invention.

[0024] Figure 3 This is a schematic diagram of the tensile specimen used in the mechanical property testing method for brazed microstructures provided by the present invention.

[0025] Figure 4 This is a schematic diagram of the tensile-detachment and bending-resistant plate in the mechanical property testing method for brazed microstructures provided by the present invention.

[0026] Figure 5 A schematic diagram of the upper fixture in the mechanical property testing method for brazed microstructures provided by the present invention;

[0027] Figure 6 A schematic diagram of the lower fixture in the mechanical property testing method for brazed microstructures provided by the present invention;

[0028] Figure 7 The stress-strain curve is obtained using the mechanical property testing method for brazed microstructures provided by this invention.

[0029] Explanation of reference numerals in the attached drawings: 1. Tensile specimen; 11. Upper specimen plate; 12. Intermediate stiffener plate; 13. Lower specimen plate; 14. First threaded hole; 15. Second threaded hole; 2. Tension-resistant and bending-resistant plate; 3. Upper clamp; 31. First connecting plate; 32. First stud; 33. First mounting hole; 4. Lower clamp; 41. Second connecting plate; 42. Second stud; 43. Second mounting hole; 5. Extension plate; 51. First horizontal plate; 52. Vertical plate; 53. Second horizontal plate; 6. Opening; 7. Third threaded hole. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The purpose of this invention is to provide a method for testing the mechanical properties of brazed microstructures, which solves the problems of easy bending and thread pull-out caused by the thinness of the base material, and the difficulty of strain measurement due to the small size.

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] like Figures 1-6 As shown, this embodiment provides a method for testing the mechanical properties of brazed microstructures, including the following steps:

[0034] Step 1: Design and prepare tensile specimen 1. Tensile specimen 1 includes an upper specimen plate 11, an intermediate stiffener 12 and a lower specimen plate 13. The upper specimen plate 11 and the intermediate stiffener 12 are an integral structure. The intermediate stiffener 12 is perpendicular to the upper specimen plate 11. The end of the intermediate stiffener 12 away from the upper specimen plate 11 is welded to the lower specimen plate 13. A weld is formed between the intermediate stiffener 12 and the lower specimen plate 13. The intermediate stiffener 12 is perpendicular to the lower specimen plate 13.

[0035] Step 2: Design and prepare the tensile-detachable and bending-resistant plate 2. An opening 6 is provided on one side of the tensile-detachable and bending-resistant plate 2. Place the tensile-detachable and bending-resistant plate 2 between the upper test plate 11 and the lower test plate 13, and make the intermediate stiffener 12 located in the opening 6.

[0036] Step 3: The length and width of the weld are determined using an optical measurement system, thereby achieving high measurement accuracy;

[0037] Step 4: Install the extensometer on the tensile specimen 1. The extensometer is used to enlarge the gauge length of the tensile specimen 1. Use a COD gauge in conjunction with the extensometer to perform strain measurement.

[0038] Step 5: Install the upper test plate 11 on the upper clamp 3 of the testing machine, and install the lower test plate 13 and the tensile-bending plate 2 on the lower clamp 4 of the testing machine. Perform a tensile test to obtain the stress-displacement curve, and convert it into a stress-strain curve based on the gauge length.

[0039] In this embodiment, the lower test plate 13 is the base material, which is relatively thin. By setting an anti-pull-out and anti-bending plate 2 on one side of the lower test plate 13 and connecting the two together to the lower clamp 4, the problems of bending and thread pull-out caused by the thin base material are solved. The extrusion device in this embodiment is used to enlarge the gauge length of the tensile specimen 1. Strain measurement is performed using a COD gauge in conjunction with the extrusion device, thereby obtaining accurate strain and solving the problem of difficulty in strain measurement due to small size. Figure 7As shown, accurate stress-strain curves can be obtained. The method in this embodiment can also be used for performance testing of microstructures under other tensile and compressive loading modes.

[0040] Specifically, in step one, the upper test plate 11 is provided with two first threaded hole groups, which are symmetrically arranged with respect to the weld, and each first threaded hole group includes multiple first threaded holes 14 arranged sequentially along the length direction of the weld; the lower test plate 13 is provided with two second threaded hole groups, which are symmetrically arranged with respect to the weld, and each second threaded hole group includes multiple second threaded holes 15 arranged sequentially along the length direction of the weld.

[0041] In step one, a first plate body is prepared, which has multiple spaced strips on one side. The strips are integral with the first plate body and are perpendicular to it, with the strips parallel to each other. The ends of each strip away from the first plate body are welded to a second plate body, thus enabling the preparation of multiple tensile specimens 1 as needed. In this embodiment, both the first plate body and the strips are copper plates, and the second plate body is a stainless steel plate.

[0042] Specifically, after marking the weld position, the first threaded hole 14 is machined on the first plate according to the designed tensile specimen 1, so that two rows of first threaded holes 14 are symmetrically arranged on the first plate relative to the weld. Second threaded holes 15 are machined on the second plate, so that two rows of second threaded holes 15 are symmetrically arranged on the second plate relative to the weld. Then, the upper test plate 11, the lower test plate 13, and the intermediate plate between the upper and lower test plates 11 are cut using wire cutting, so that the upper test plate 11 has two sets of first threaded holes and the lower test plate 13 has two sets of second threaded holes. At this time, both ends of the intermediate plate are flush with the ends of the upper and lower test plates 11 and 13. Then, according to the weld length requirements, both ends of the intermediate plate are wire-cut, and the wire-cutting influence layer is ground away, thus forming the intermediate stiffening plate 12, thereby preparing the tensile specimen 1. In the processing of the tensile specimen 1, from the precise positioning of the brazing position to the integrated processing of the first threaded hole 14 and the second threaded hole 15, the high consistency of the tensile specimen 1 can be ensured, resulting in extremely high reliability.

[0043] It should be noted that in this embodiment, the processing of the first threaded hole 14 and the second threaded hole 15, as well as the subsequent processing of the tensile specimen 1, can also be carried out by laser processing methods.

[0044] In the design of tensile specimen 1, the basic form remains unchanged, but it can be for brazed joints or brazed welds. It can be without chamfers, have a rounded transition, or have a notch in the middle. The choice depends on the purpose of the tensile test.

[0045] In step two, the tensile-detachment and bending-resistant plate 2 is provided with two third threaded hole groups. The two third threaded hole groups are symmetrically arranged with respect to the opening 6, and each third threaded hole group includes multiple third threaded holes 7 arranged sequentially along the length direction of the opening 6. The third threaded holes 7 are arranged one-to-one with the second threaded holes 15, which facilitates the connection between the lower test plate 13 and the tensile-detachment and bending-resistant plate 2.

[0046] In this specific embodiment, the first threaded hole group includes two first threaded holes 14, the second threaded hole group includes two second threaded holes 15, and the third threaded hole group includes two third threaded holes 7.

[0047] In step four, the stretching device includes two symmetrically arranged stretching plates 5. Each stretching plate 5 includes a first horizontal plate 51, a vertical plate 52, and a second horizontal plate 53. The first horizontal plate 51 is connected to one side of the lower part of the vertical plate 52, and the second horizontal plate 53 is connected to the other side of the upper part of the vertical plate 52. The end of the first horizontal plate 51 of one stretching plate 5 away from the vertical plate 52 is attached to the side of the upper test plate 11 near the lower test plate 13. The end of the first horizontal plate 51 of the other stretching plate 5 away from the vertical plate 52 is attached to the side of the lower test plate 13 near the upper test plate 11. The COD gauge is inserted between the two second horizontal plates 53. In this embodiment, the length of the vertical plate 52 is known. The distance between the upper test plate 11 and the lower test plate 13 can be obtained by subtracting the length of the two vertical plates 52 from the distance between the two second horizontal plates 53 measured by the COD gauge. By setting up the stretching device, the gauge length of the tensile specimen 1 is enlarged.

[0048] It should be noted that a non-contact deformation measurement system can also be used to replace the extensometer and COD gauge, which slightly reduces the measurement accuracy.

[0049] In step five, a suitable testing machine is selected based on the dimensions of the tensile specimen 1. A connecting fixture corresponding to the tensile specimen 1 is designed based on the type of testing machine. The loading displacement is calculated according to the tensile test standard. After installing the tensile specimen 1, the tensile test is performed. In this embodiment, the testing machine needs to meet the requirement that the maximum load is more than 50% of the maximum load of the testing machine, and the accuracy of the testing machine is 0.5 grade.

[0050] Specifically, the upper clamp 3 includes a first connecting plate 31 and a first stud 32 disposed on one side of the first connecting plate 31. The first connecting plate 31 is provided with first mounting holes 33 corresponding to the first threaded holes 14. In this embodiment, the first mounting holes 33 are first threaded mounting holes. Multiple first connecting bolts are used to connect the first connecting plate 31 to the upper test plate 11, so that each first connecting bolt is installed from the first mounting hole 33 into the first threaded hole 14. The lower clamp 4 includes a second connecting plate 41 and a second stud 42 disposed on one side of the second connecting plate 41. The second connecting plate 41 is provided with second mounting holes 43 corresponding to the second threaded holes 15. In this embodiment, the second mounting holes 43 are second threaded mounting holes. Multiple second connecting bolts are used to connect the second connecting plate 41, the lower test plate 13, and the tensile-bending plate 2, so that each second connecting bolt is installed from the second mounting hole 43 into the second threaded hole 15 and the third threaded hole 7, thereby completing the installation of the tensile specimen 1.

[0051] In step five, to increase the bending resistance of the anti-pull-out and anti-bending plate 2, metal adhesive can be used to connect the lower test plate 13 and the anti-pull-out and anti-bending plate 2 while simultaneously connecting them with bolts. Alternatively, metal adhesive can be applied between the lower test plate 13 and the second connecting plate 41, and between the upper test plate 11 and the first connecting plate 31.

[0052] This embodiment also includes step six, which involves analyzing and measuring the elongation of the fractured tensile specimen 1 to complete the mechanical property test.

[0053] In this embodiment, a set of brazed microstructure tensile specimen preparation process and testing method was established through the rational design of the brazed microstructure tensile specimen, the optimization of the tensile specimen preparation process, the anti-pull-out bending design of the tensile specimen, the strain measurement design of the tensile specimen, and the design of the connecting fixture. This enabled the tensile performance testing of the brazed microstructure, obtained accurate stress-strain curves of the brazed microstructure engineering, promoted the reliability design of the brazed microstructure, improved the accuracy and reliability of finite element analysis, and provided a reference for the testing of other mechanical properties of brazed microstructures, especially fatigue performance testing.

[0054] This specification uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for testing the mechanical properties of brazed microstructures, characterized in that, Includes the following steps: Step 1: Design and prepare a tensile specimen. The tensile specimen includes an upper specimen plate, an intermediate stiffener plate, and a lower specimen plate. The upper specimen plate and the intermediate stiffener plate are an integral structure. The end of the intermediate stiffener plate away from the upper specimen plate is welded to the lower specimen plate, and a weld is formed between the intermediate stiffener plate and the lower specimen plate. The upper test plate is provided with two first threaded hole groups, which are symmetrically arranged with respect to the weld, and each first threaded hole group includes a plurality of first threaded holes arranged sequentially along the length direction of the weld; the lower test plate is provided with two second threaded hole groups, which are symmetrically arranged with respect to the weld, and each second threaded hole group includes a plurality of second threaded holes arranged sequentially along the length direction of the weld. Prepare a first plate with multiple spaced strips on one side, the strips being an integral part of the first plate. Weld the ends of each strip away from the first plate to a second plate. Mark the position of the weld. According to the designed tensile specimen, process the first threaded hole on the first plate and the second threaded hole on the second plate. Then, use wire cutting to cut out the upper test plate, the lower test plate, and the intermediate plate between the upper and lower test plates. At this time, the two ends of the intermediate plate are flush with the two ends of the upper and lower test plates. Then, according to the length requirements of the weld, wire cut the two ends of the intermediate plate to form the intermediate stiffener, thereby preparing the tensile specimen. Step 2: Design and prepare a tensile-detachable and bending-resistant plate. The tensile-detachable and bending-resistant plate has an opening on one side. The tensile-detachable and bending-resistant plate is placed between the upper test plate and the lower test plate, with the intermediate stiffener plate located in the opening. The anti-pull-out and anti-bending plate is provided with two third threaded hole groups. The two third threaded hole groups are symmetrically arranged with respect to the opening, and each third threaded hole group includes multiple third threaded holes arranged sequentially along the length direction of the opening. The third threaded holes correspond one-to-one with the second threaded holes. Step 3: Use an optical measurement system to determine the length and width of the weld. Step 4: Install the extensometer on the tensile specimen. The extensometer is used to enlarge the gauge length of the tensile specimen. Use a COD gauge in conjunction with the extensometer to perform strain measurement. Step 5: Install the upper test plate on the upper clamp of the testing machine, and install the lower test plate and the tensile-bending plate on the lower clamp of the testing machine. Perform a tensile test to obtain the stress-displacement curve, and convert it into a stress-strain curve based on the gauge length.

2. The method for testing the mechanical properties of brazed microstructures according to claim 1, characterized in that, The first threaded hole group includes two first threaded holes, the second threaded hole group includes two second threaded holes, and the third threaded hole group includes two third threaded holes.

3. The method for testing the mechanical properties of brazed microstructures according to claim 1, characterized in that, In step four, the drawing device includes two symmetrically arranged drawing plates. Each drawing plate includes a first horizontal plate, a vertical plate, and a second horizontal plate. The first horizontal plate is connected to one side of the lower part of the vertical plate, and the second horizontal plate is connected to the other side of the upper part of the vertical plate. The end of the first horizontal plate of one drawing plate away from the vertical plate is attached to the side of the upper test plate near the lower test plate, and the end of the first horizontal plate of the other drawing plate away from the vertical plate is attached to the side of the lower test plate near the upper test plate. The COD gauge is inserted between the two second horizontal plates.

4. The method for testing the mechanical properties of brazed microstructures according to claim 1, characterized in that, In step five, the upper clamp includes a first connecting plate and a first stud disposed on one side of the first connecting plate. The first connecting plate is provided with first mounting holes corresponding one-to-one with the first threaded holes. Multiple first connecting bolts are used to connect the first connecting plate to the upper test plate, so that each first connecting bolt is installed from the first mounting hole into the first threaded hole. The lower clamp includes a second connecting plate and a second stud disposed on one side of the second connecting plate. The second connecting plate is provided with second mounting holes corresponding one-to-one with the second threaded holes. Multiple second connecting bolts are used to connect the second connecting plate, the lower test plate, and the tensile-detachable and bending-resistant plate, so that each second connecting bolt is installed from the second mounting hole into the second threaded hole and the third threaded hole, thereby completing the installation of the tensile specimen.

5. The method for testing the mechanical properties of brazed microstructures according to claim 1, characterized in that, It also includes step six, which involves analyzing and measuring the elongation of the fractured tensile specimen to complete the mechanical property test.

Images