Metal single shear sample and clamp for pure shear stress experiment
By designing a metal single shear sample and fixture for pure shear stress experiments, and using the boss on the fixture to apply axial compression load to the sample, the problem of difficult to effectively test the mechanical properties of metal materials under pure shear stress in the prior art is solved, and the purpose of saving precious metal materials is achieved.
Patent Information
- Application Number
- CN202411290504.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-14
- Publication Date
- 2025-03-04
AI Technical Summary
The prior art is difficult to effectively test the mechanical properties of metal materials under pure shear stress while reducing waste of precious metal materials.
A metal single shear sample and fixture is designed. The sample is a cylindrical block-shaped integrated structure with two gaps symmetrically in the radial direction. The axial compression load is applied to the loading section through the boss on the fixture to form a pure shear stress state.
On the basis of reducing the use of precious metals, we have studied the elastic-plastic deformation and fracture behavior of metal materials under pure shear stress, while saving precious metal materials.
Smart Images
Figure CN119555518A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of material mechanical property research, and in particular relates to a metal single shearing specimen and a fixture for a pure shearing stress experiment. Background Art
[0002] With the development of science and technology, the demand for new materials is becoming more and more urgent. In the practical application of aerospace, chemical, machinery, shipbuilding, electronics, communications and other engineering and the research, development, demonstration and manufacturing of new materials, the mechanical properties of metal materials themselves, including but not limited to yield strength, tensile strength, elongation, elastic-plastic deformation, and fracture behavior, are the basic information that must be clarified first. In addition to dealing with simple static loading conditions, the dynamic mechanical properties of metal materials are also worthy of attention when serving under complex and extreme working conditions. In recent years, researchers have developed a variety of testing techniques to study the mechanical properties of metal materials under pure shear stress. However, new theories, as well as test costs and some structural characteristics of the materials themselves, make conventional standard shear specimens no longer applicable. For some expensive metal materials, when testing, it is often hoped that there will be no extra material waste outside the gauge section or test area. Therefore, research on how to conduct small-scale and less wasteful mechanical property tests on precious metal materials has become a development trend.
[0003] At present, in order to reduce the waste of precious metal materials, in addition to reducing the size of the test material and conducting tensile tests on small-sized specimens, the commonly used method is to replace the specimen clamping section with other cheap materials, and then use other relatively cheap materials as clamping sections to connect the two ends of the test section through welding, riveting or bolting, so as to reduce the waste of precious materials in the clamping section. However, welding will affect the material properties of the specimen test section, thereby affecting the test results, and the specimens that connect the clamping section and the test section by riveting or bolting are mainly used for tensile or compression tests. Summary of the invention
[0004] In view of this, the present invention provides a metal single shear specimen and a fixture for pure shear stress experiments. The specimen and the fixture can cooperate to study the elastic-plastic deformation and fracture behavior of the specimen test section under pure shear stress state while reducing the use of precious metals.
[0005] The metal single shear specimen for pure shear stress experiment provided by the present invention adopts the following technical scheme:
[0006] A metal single shear specimen for pure shear stress experiment, the specimen is a cylindrical block-shaped integral structure with two notches symmetrically arranged along the radial direction, including two loading sections, two transition sections and a test section;
[0007] The cross section of the loading section is arcuate, the two loading sections are arranged opposite to each other and symmetrical along the axial direction, and the two loading sections are symmetrically provided with first screw fastening holes along the axial direction;
[0008] The transition section is a radially protruding structure at the middle of the end surface opposite to the loading section;
[0009] The test section is in the shape of a square column, and two side surfaces of the test section are respectively connected to the two transition sections;
[0010] The cross-sectional area of the test section is smaller than the cross-sectional area of the transition section.
[0011] Furthermore, the thickness of the loading section is not less than the radius of the sample.
[0012] Further, the transition section and the loading section have the same height;
[0013] The test section has a height smaller than that of the sample and is located in the axial middle of the sample.
[0014] Furthermore, a rounded transition is adopted at the connection between the transition section and the loading section.
[0015] Furthermore, a rounded transition is adopted at the connection between the test section and the transition section.
[0016] Further, it comprises an upper clamp and a lower clamp of the same structure;
[0017] The upper clamp and the lower clamp both include a cylindrical block base and a boss arranged on an end surface of one end of the base, and are provided with a second screw fastening hole penetrating the base and the boss;
[0018] After the second screw fastening holes on the upper clamp and the lower clamp are respectively aligned with the first screw fastening holes at corresponding positions on the specimen and the screws are screwed in, the bosses of the upper clamp and the lower clamp are respectively fitted with the axial end faces of the two loading sections of the specimen.
[0019] Furthermore, the boss is semi-disc-shaped, and its diameter is equal to the diameter of the sample.
[0020] Furthermore, the height of the boss is smaller than the height of the sample.
[0021] Furthermore, the diameter of the base is smaller than the diameter of the incident rod / transmission rod in the Hopkinson rod device, and the difference in diameter is less than 5 mm.
[0022] Furthermore, the second screw fastening hole is a countersunk hole.
[0023] Beneficial effects:
[0024] 1. The specimen is a cylindrical block-shaped integrated structure with two notches symmetrically arranged along the radial direction, including two loading sections, two transition sections and a test section; the cross section of the loading section is arch-shaped, the two loading sections are arranged opposite to each other and symmetrically along the axial direction, and the two loading sections are symmetrically arranged with first screw fastening holes along the axial direction; the transition section is a radial protrusion structure in the middle of the opposite end surface of the loading section; the test section is in the shape of a square column, and the two side surfaces of the test section are respectively connected to the two transition sections; the cross-sectional area of the test section is smaller than the cross-sectional area of the transition section;
[0025] The upper fixture and the lower fixture both include a cylindrical block base and a boss arranged on the end surface of the base, and are provided with a second screw fastening hole penetrating the base and the boss; after the second screw fastening holes on the upper fixture and the lower fixture are aligned with the first screw fastening holes on the specimen and the screws are screwed in, the bosses of the upper fixture and the lower fixture are respectively fitted with the axial end surfaces of the two loading sections of the specimen;
[0026] In this way, an axial compressive load can be applied to the axial end faces of the two loading sections through the bosses on the fixture, so that the test section can form a pure shear stress state in the shear area, thereby achieving the purpose of studying the elastic-plastic deformation and fracture behavior of metal materials under the pure shear stress state. Moreover, the fixture can use cheap materials different from the sample material, thereby saving precious metal materials.
[0027] 2. The thickness of the loading section is not less than the radius of the specimen. Making the specimen thicker can enhance the stiffness of the specimen. Making the specimen thicker has higher axial stability under compression load and is less likely to deflect in the axial direction.
[0028] 3. The height of the transition section and the loading section is the same. The height of the test section is less than the height of the specimen and is located in the axial middle of the specimen. This makes it easier to form a pure shear stress state in the shear area when the specimen is subjected to axial compression load.
[0029] 4. The connection between the transition section and the loading section adopts a rounded transition, and the connection between the test section and the loading section adopts a rounded transition, which can further make it easier to form a pure shear stress state in the shear area when the specimen is subjected to axial compression load.
[0030] 5. The boss is semi-disc-shaped, and its diameter is equal to that of the specimen. Thus, on the one hand, the boss increases the distance between the axial end face of the base and the axial end face of the specimen loading section, which can increase the measurement stroke, that is, the experiment can be carried out within a larger axial compression load range. On the other hand, the boss diameter is equal to the specimen diameter, that is, the cross-sectional area of the boss is slightly larger than the cross-sectional area of the specimen loading section (with the area of the specimen notch being more), so that a more uniform axial compression load can be applied to the specimen.
[0031] 6. The height of the boss is smaller than the height of the specimen, which can enhance the stability of the specimen when subjected to axial compression load.
[0032] 7. The diameter of the base is smaller than the diameter of the incident rod / transmission rod in the Hopkinson rod device, and the diameter difference is less than 5 mm, which can ensure good contact between the fixture and the Hopkinson rod loading device and reduce experimental errors. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Figure 1 is a schematic diagram of the three-dimensional structure of a sample provided in Example 1 of the present invention;
[0034] Figure 2 yes Figure 1 A top view of
[0035] Figure 3 is a schematic diagram of the three-dimensional structure of the upper clamp provided in the second embodiment of the present invention;
[0036] Figure 4 is a schematic diagram of the assembly of a sample and a fixture provided in the second embodiment of the present invention;
[0037] Figure 5 yes Figure 4 Explosion diagram of
[0038] Among them, 1-upper fastening screw, 101-loading section, 102-transition section, 103-test section, 104-first screw fastening hole, 2-upper fixture, 201-base, 202-boss, 203-second screw fastening hole, 3-specimen, 4-lower fixture, 5-lower fastening screw. DETAILED DESCRIPTION
[0039] The present invention is described in detail below with reference to the accompanying drawings and embodiments.
[0040] Embodiment 1:
[0041] Reference Figure 1 and Figure 2, a metal single shear specimen 3 for pure shear stress test, the specimen 3 is a cylindrical block-shaped integrated structure with two notches symmetrically arranged along the radial direction, including two loading sections 101, two transition sections 102 and a test section 103; the cross section of the loading section 101 is an arch-shaped, the two loading sections 101 are arranged opposite to each other and symmetrically along the axial direction, and the two loading sections 101 are symmetrically arranged with first screw fastening holes 104 along the axial direction; the transition section 102 is a radial protrusion structure at the middle of the opposite end surface of the loading section 101; the test section 103 is a square column shape arranged between the two transition sections 102, and the two side surfaces of the test section 103 are respectively connected to the two loading sections 101; and the cross-sectional area of the test section 103 is smaller than the cross-sectional area of the transition section 102. The overall structure of the specimen 3 thus formed is a cylindrical block-shaped structure with two notches symmetrically arranged along the radial direction, and the notches have two different width sections.
[0042] Specifically, the thickness of the loading section 101 is not less than the radius of the sample 3, so that the axial dimension of the sample 3 is larger than the radial dimension, which can enhance the rigidity of the sample 3, so that the sample 3 has higher stability in the axial direction under the action of the compressive load, and is less likely to deflect in the axial direction. Moreover, the transition section 102 and the loading section 101 have the same height, and the height of the test section 103 is less than the height of the transition section 102, and is located in the axial middle of the sample 3. In this way, when the sample 3 is subjected to an axial compressive load, it is easier to form a pure shear stress state in the shear region. More specifically, a rounded transition is provided at the connection between the transition section 102 and the loading section 101, and a rounded transition is provided at the connection between the test section 103 and the transition section 102, which can further make it easier for the sample 3 to form a pure shear stress state in the shear region when it is subjected to an axial compressive load.
[0043] The sample 3 can be machined by turning, wire cutting, or other machining methods. After the shape of the sample 3 is cut from the metal bar, the complete structure of the sample 3 is further machined according to the drawing. In addition, the surface of the sample 3 is polished to make its surface roughness reach the Ra1.6 standard, and then cleaned with alcohol and dried for later use.
[0044] Embodiment 2:
[0045] On the basis of the first embodiment, this embodiment provides a fixture for pure shear stress experiment, which is used to clamp the sample 3 in the first embodiment and directly apply an axial compression load to the sample 3.
[0046] Reference Figure 3~Figure 5 The fixture comprises an upper fixture 2 and a lower fixture 4 of the same structure, each of which comprises a cylindrical block base 201 and a boss 202 disposed on an end surface of the base 201, and a second screw fastening hole penetrating the base 201 and the boss 202 is disposed; Figure 4As shown, after the second screw fastening holes 203 on the upper clamp 2 and the lower clamp 4 are respectively aligned with the first screw fastening holes 104 at the corresponding positions on the specimen 3 and the upper fastening screws 1 and the lower fastening screws 5 are screwed in, the bosses 202 of the upper clamp 2 and the lower clamp 4 are respectively fitted with the axial end surfaces of the two loading sections 101 of the specimen 3 (that is, the boss 202 of the upper clamp is respectively fitted with the upper end surface of one of the loading sections 101, and the boss 202 of the lower clamp 4 is fitted with the lower end surface of the other loading section 101).
[0047] It should be noted that, in order to obtain a pure shear stress state in the test section 103, the traditional metal shear specimen 3 directly applies an axial compressive load to the test section 103 through the structure of the specimen 3 itself. That is to say, if the design is carried out according to the structure of the traditional metal shear specimen 3, Figure 4 The sample 3 and the fixture are an integrated structure. In contrast, the present invention applies an axial compressive load to the axial end faces of the two loading sections 101 through the boss 202 on the fixture, so that the test section 103 can form a pure shear stress state in the shear region, thereby achieving the purpose of studying the elastic-plastic deformation and fracture behavior of metal materials under the pure shear stress state. Moreover, the fixture can use a cheap material different from the material of the sample 3, thereby achieving the effect of saving precious metal materials.
[0048] Specifically, in this embodiment, the boss 202 is semi-disc-shaped, and its diameter is equal to the diameter of the sample 3. Thus, on the one hand, the boss 202 increases the distance between the axial end face of the base 201 and the axial end face of the loading section 101 of the sample 3, and can increase the measurement stroke, that is, the experiment can be carried out within a larger axial compression load range. On the other hand, the diameter of the boss 202 is equal to the diameter of the sample 3, that is, the cross-sectional area of the boss 202 is slightly larger than the cross-sectional area of the loading section 101 of the sample 3 (exceeding the area of the notch portion of the sample 3), so that a more uniform axial compression load can be applied to the sample 3.
[0049] More specifically, the height of the boss 202 is smaller than the height of the sample 3 , which can enhance the stability of the sample 3 when subjected to an axial compression load and avoid deflection.
[0050] In addition, in this embodiment, the second screw fastening hole 203 is a countersunk hole, which can keep the axial end surface of the fixture flat and easy to load. Moreover, the diameter of the base 201 is smaller than the diameter of the incident rod / transmission rod in the Hopkinson bar device, and the diameter difference is less than 5 mm, which can ensure good contact between the fixture and the Hopkinson bar loading device and reduce experimental errors. It should be noted that the loading device can also be a universal testing machine.
[0051] The fixture can be machined by turning, milling and other machining methods. After cutting the shape of the fixture from the raw material bar with a diameter of 40mm, the fixture is further fine-machined according to the drawing. In addition, the surface of the fixture is polished to make its surface roughness reach the Ra1.6 standard, and then cleaned with alcohol and dried for use.
[0052] During the experiment, according to Figure 4 The fixture and sample 3 are assembled, and the assembled whole is installed in the clamping position of the loading device. When the Hopkinson bar device is used as the loading device, strain gauges are pasted on the incident bar and the transmission bar to measure the incident wave, transmission wave and reflection wave curves, and finally summarized in the computer system for recording and processing.
[0053] After observing the sample 3 after the experiment, the present invention found that the shear fracture area occurred in the designed test section 103 area, indicating that the shear sample 3 and the fixture designed by the present invention can realize the pure shear stress experiment.
[0054] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. A metal single shear specimen for pure shear stress experiment, characterized in that: The sample is a cylindrical block-shaped integral structure with two notches symmetrically arranged along the radial direction, including two loading sections, two transition sections and a test section; The cross section of the loading section is arcuate, the two loading sections are arranged opposite to each other and symmetrical along the axial direction, and the first screw fastening holes are symmetrically arranged on the two loading sections along the axial direction; The transition section is a radially protruding structure at the middle of the end surface opposite to the loading section; The test section is in the shape of a square column, and two side surfaces of the test section are respectively connected to the two transition sections; The cross-sectional area of the test section is smaller than the cross-sectional area of the transition section.
2. A metal single shear specimen for pure shear stress experiment according to claim 1, characterized in that: The thickness of the loading section is not less than the radius of the sample.
3. A metal single shear specimen for pure shear stress experiment according to claim 1 or 2, characterized in that: The transition section and the loading section have the same height; The test section has a height smaller than that of the sample and is located in the axial middle of the sample.
4. A metal single shear specimen for pure shear stress experiment according to claim 3, characterized in that: A rounded transition is used at the connection between the transition section and the loading section.
5. A metal single shear specimen for pure shear stress experiment according to claim 3, characterized in that: A rounded transition is used at the connection between the test section and the transition section.
6. A fixture for pure shear stress experiment, used for clamping the sample according to any one of claims 1 to 5, characterized in that: It includes an upper clamp and a lower clamp of the same structure; The upper clamp and the lower clamp both include a cylindrical block base and a boss arranged on an end surface of one end of the base, and are provided with a second screw fastening hole penetrating the base and the boss; After the second screw fastening holes on the upper clamp and the lower clamp are respectively aligned with the first screw fastening holes at corresponding positions on the specimen and the screws are screwed in, the bosses of the upper clamp and the lower clamp are respectively fitted with the axial end faces of the two loading sections of the specimen.
7. A fixture for pure shear stress experiment according to claim 6, characterized in that: The boss is in a semi-disc shape, and its diameter is equal to that of the sample.
8. A fixture for pure shear stress experiment according to claim 6 or 7, characterized in that: The height of the boss is smaller than the height of the sample.
9. A fixture for pure shear stress experiment according to claim 6 or 7, characterized in that: The diameter of the base is smaller than the diameter of the incident rod / transmission rod in the Hopkinson rod device, and the difference in diameter is less than 5 mm.
10. A fixture for pure shear stress experiment according to claim 6 or 7, characterized in that: The second screw fastening hole is a countersunk hole.