Method for testing a composite ring under radial uniform compression

Abstract

The present application relates to a kind of composite material annular radial uniform pressure test method, comprising the annular test piece is placed in the inside of elastic inner ring;Annular test piece and elastic inner ring are placed in support on lower pressing disc, and elastic inner ring is located just below upper outer ring;Outer ring moves downward, and the inner circumference of outer ring is wedge-shaped with the outer circumference of elastic inner ring, with the continuous descent of outer ring, the inner circumference of outer ring is extruded with the outer circumference of elastic inner ring;Elastic inner ring outer circumference is forced and radially shrinks, and the inner wall of elastic inner ring is wrapped and is applied to the outer wall of annular test piece radial compression load;By the external force applied to outer ring, the wedge angle between outer ring and elastic inner ring is combined, and the radial compression load applied to annular test piece is obtained;To realize the radial uniform pressure test of annular, the hoop failure stress such as mechanical property can be obtained, and the test method is provided for the in-depth study of the mechanical behavior of rotary composite pressure-resistant structure under deep-sea pressure environment.

Description

Technical Field

[0001] This invention relates to the field of pressure resistance testing technology, and in particular to a method for testing radially uniform pressure on a composite material ring. Background Technology

[0002] Underwater vehicles are weight-sensitive equipment, and a low structural weight to displacement ratio is a core technical indicator. The pressure hull accounts for the largest proportion of the total weight of an underwater vehicle, typically representing 1 / 4 to 1 / 2 of the total weight. Therefore, reducing the structural weight of the pressure hull is crucial for achieving a low structural weight to displacement ratio in underwater vehicles.

[0003] Composite materials, with their advantages of low density, high specific strength, high specific modulus, corrosion resistance, excellent material designability and stealth properties, and ease of molding, are ideal structural materials for pressure hulls of underwater vehicles. Pressure hulls made of composite materials possess excellent comprehensive properties, including light weight, resistance to seawater and chemical corrosion, and good stealth performance, meeting the demands of underwater vehicles developing towards greater depth, longer range, higher payload, and stealth capabilities. Currently, they are already being used to some extent in the pressure hulls of small deep-sea gliders and unmanned submersibles. With the acceleration of ocean development, the design and manufacture of pressure hulls for deep-sea unmanned and even manned submersibles using composite materials is receiving increasing attention.

[0004] In the pressure environment of the deep sea, composite pressure tanks are subjected to huge hydrostatic pressure loads. The composite material is under bidirectional pressure, and its mechanical behavior and structural failure are very complex. Not only will common failure modes of composite materials such as fiber breakage, matrix cracking, interface debonding, and delamination occur, but also complex failure modes such as fiber micro buckling and delamination buckling will occur, requiring a large number of experimental studies.

[0005] In existing technologies, the mechanical performance testing of composite pressure tanks mainly relies on specialized laboratory equipment such as pressure cylinders and pressure vessels, or on marine testing devices, which carries risks such as high cost and long time cycles. Therefore, there is a need for a testing device that can subject annular composite materials to radial compression to simulate the situation where a composite rotating body is subjected to radial uniform compressive load under deep-sea loading conditions. This would facilitate large-scale mechanical testing, help understand the failure characteristics and influencing factors of deep-sea pressure-resistant composite materials, and support the development of lightweight deep-sea pressure-resistant structures. Summary of the Invention

[0006] To address the shortcomings of existing production technologies, this applicant provides a structurally sound method for testing radially uniform compression of composite material rings. This method enables radially uniform compression testing of rings, obtaining mechanical properties such as circumferential failure stress. It provides experimental testing means for in-depth research on the mechanical behavior of rotary composite pressure-resistant structures under deep-sea pressure environments.

[0007] The technical solution adopted in this invention is as follows:

[0008] A method for testing radially uniform compression of a composite material ring includes the following steps:

[0009] Place the annular specimen inside the elastic inner ring;

[0010] The annular specimen and the elastic inner ring are placed together on the lower pressure plate, with the elastic inner ring located directly below the upper outer ring;

[0011] The outer ring moves downward under the action of external force, and the inner circumferential surface of the outer ring matches the wedge shape of the outer circumferential surface of the elastic inner ring. As the outer ring continues to move downward, the inner circumferential surface of the outer ring and the outer circumferential surface of the elastic inner ring are pressed together.

[0012] The outer circumferential surface of the elastic inner ring contracts radially inward under force, and the inner wall of the elastic inner ring wraps around the outer wall of the annular specimen and applies a radial compressive load.

[0013] The compressive load applied to the radial direction of the annular specimen is calculated by combining the external force applied to the outer ring with the wedge angle and friction angle between the outer ring and the elastic inner ring, as well as the external dimensions of the annular specimen.

[0014] As a further improvement to the above technical solution:

[0015] The inner circumferential surface of the outer ring is formed into an inner conical structure that is larger at the bottom and smaller at the top, while the outer circumferential surface of the elastic inner ring is formed into an outer conical structure that is smaller at the top and larger at the bottom. The cone angles of the inner and outer conical structures are the same, forming a matching wedge shape. The diameter of the larger end of the inner conical structure is larger than the diameter of the smaller end of the outer conical structure, while the diameter of the larger end of the inner conical structure is smaller than the diameter of the larger end of the outer conical structure in its natural state.

[0016] The cone angle is 10°-15°.

[0017] The upper end face of the elastic inner ring is provided with an inner and outer through groove at intervals along the circumference, and the lower end face of the elastic inner ring is provided with a lower through groove at intervals along the circumference. The upper and lower grooves are arranged alternately. The length of the upper and lower grooves is greater than half of the axial height of the elastic inner ring.

[0018] The lower end of the upper groove and the upper end of the lower groove both extend to form a circular structure, and the diameter of the circular structure is larger than the width of the upper and lower grooves.

[0019] The inner circumferential surface of the elastic inner ring is configured as a cylindrical straight surface.

[0020] The elastic inner ring is made of 65Mn steel and undergoes quenching heat treatment and tempering treatment at 45°C.

[0021] It also includes a pad ring supported on the lower pressure plate. Before testing, the elastic inner ring is placed on the pad ring, and the pad ring is used to center and position the elastic inner ring. The top surface of the outer ring is provided with an upper pressure plate. When the upper pressure plate moves downward relative to the lower pressure plate, it drives the outer ring to approach and fit against the elastic inner ring below, applying force to it.

[0022] The top edge of the pad ring is formed by an outer step along the circumference. The outer step fits into the inner edge of the bottom surface of the elastic inner ring. A one-sided gap is provided between the side wall of the outer step and the inner wall of the elastic inner ring. The size of the one-sided gap is larger than the inner shrinkage size of the elastic inner ring.

[0023] The single-sided gap is 2-4mm.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention features a compact and rational structure, convenient operation, and reliable use. Through the wedge-shaped fit between the inner circumferential surface of the outer ring and the outer circumferential surface of the elastic inner ring, combined with the radial contraction characteristics of the elastic inner ring itself, the outer ring moves radially relative to the elastic inner ring during axial movement, causing the elastic inner ring to contract radially. This applies a uniform radial load to the annular specimen inside the elastic inner ring, enabling radial compression testing of the annular specimen. It can obtain mechanical properties including uniform pressure, circumferential failure stress, failure pressure, and failure mode, providing an experimental testing method for in-depth research on the mechanical behavior of rotary composite pressure-resistant structures under deep-sea pressure environments.

[0026] The present invention also includes the following advantages:

[0027] By using a force loading mechanism or a universal testing machine, a vertical compressive load is applied to the testing device. The wedge shape of the outer ring and the elastic inner ring is matched. Relying on the wedge clamping force of the inner and outer rings and the radial deformation of the elastic inner ring, the vertical compressive load is converted into a radial compressive load along the circumference. Thus, the radial compression test of the composite material ring can be carried out based on the existing force loading mechanism. The radial compression along the circumference is uniform and reliable, realizing the simulation of the external pressure test load in deep sea static water.

[0028] This invention can simulate the situation of marine equipment being subjected to uniformly distributed hydrostatic external pressure, which is conducive to carrying out a large number of experimental studies in the laboratory, and can conveniently and quickly obtain the mechanical performance parameters of deep-sea composite pressure-resistant structures, so as to understand the failure characteristics and influence laws of deep-sea pressure-resistant composite materials, support the research and development of lightweight deep-sea pressure-resistant structures, greatly enrich the performance testing methods of deep-sea pressure-resistant structures, and has the advantages of reliability, economy, ease of operation and high precision. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the state of the present invention during testing.

[0030] Figure 2This is a force analysis diagram of the annular specimen during the test of this invention.

[0031] Figure 3 This is a schematic diagram of the test device of the present invention.

[0032] Figure 4 This is a schematic diagram of the outer ring structure of the present invention.

[0033] Figure 5 This is a schematic diagram of the elastic inner ring of the present invention.

[0034] Figure 6 for Figure 5 A magnified view of a portion of point A in the middle.

[0035] Figure 7 This is a schematic diagram of the structure of the gasket ring of the present invention.

[0036] The components are: 1. Upper pressure plate; 2. Outer ring; 3. Annular specimen; 4. Elastic inner ring; 5. Gasket ring; 6. Lower pressure plate;

[0037] 20. Inner conical structure;

[0038] 41. Cylindrical straight surface; 42. Outer conical structure; 43. Upper groove; 44. Lower groove; 45. Circular structure;

[0039] 50. External steps. Detailed Implementation

[0040] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0041] like Figure 1 , Figure 3 As shown in this embodiment, a method for testing the radial uniform compression of a composite material ring includes the following steps:

[0042] Place the annular specimen 3 inside the elastic inner ring 4;

[0043] The annular specimen 3 and the elastic inner ring 4 are placed together on the lower pressure plate 6, with the elastic inner ring 4 located directly below the upper outer ring 2;

[0044] The outer ring 2 moves downward under the action of external force. The inner circumferential surface of the outer ring 2 matches the wedge shape of the outer circumferential surface of the elastic inner ring 4. As the outer ring 2 continues to move downward, the inner circumferential surface of the outer ring 2 and the outer circumferential surface of the elastic inner ring 4 are pressed together.

[0045] The outer circumferential surface of the elastic inner ring 4 is subjected to force and radially shrinks inward. The inner wall of the elastic inner ring 4 wraps around the outer wall of the annular specimen 3 and applies a radial compressive load.

[0046] As the axial movement of the outer ring increases, the radial compressive load on the specimen also increases, thus achieving uniform compressive loading on the annular specimen.

[0047] The radial compressive load applied to the annular specimen 3 is calculated by combining the axial external force applied to the outer ring 2 with the wedge angle and friction angle between the outer ring 2 and the elastic inner ring 4, as well as the external dimensions of the annular specimen 3.

[0048] By using a wedge-shaped fit between the inner circumferential surface of the outer ring 2 and the outer circumferential surface of the elastic inner ring 4, combined with the radial contraction characteristics of the elastic inner ring 4 itself, the elastic inner ring 4 is caused to contract radially during the axial relative movement of the outer ring 2 with respect to the elastic inner ring 4, thereby applying a radially uniform load to the annular specimen 3 inside the elastic inner ring 4, and realizing the radial compression test of the annular specimen 3.

[0049] By controlling the vertical load applied to the outer ring 2, and by controlling and managing the testing process, multiple mechanical properties of the ring specimen 3, including uniform pressure, circumferential failure stress, failure pressure, and failure mode, can be obtained.

[0050] like Figure 4 As shown, the inner circumferential surface of the outer ring 2 is formed into an inner conical structure 20 with a larger bottom and a smaller top, and the outer circumferential surface of the elastic inner ring 4 is formed into an outer conical structure 42 with a smaller top and a larger bottom. The cone angles of the inner conical structure 20 and the outer conical structure 42 are consistent, forming a matching wedge shape. Thus, during the axial downward movement of the outer ring 2, the axial force is converted into a radial force in the horizontal direction through the matching wedge shape. The diameter of the larger end of the inner conical structure 20 is larger than the diameter of the smaller end of the outer conical structure 42, so that the outer ring 2 can be conveniently, quickly, and reliably fitted onto the elastic inner ring 4. The diameter of the larger end of the inner conical structure 20 is smaller than the diameter of the larger end of the outer conical structure 42 in its natural state, so that the elastic inner ring 4 can reliably bear force and generate radial contraction during the axial relative movement.

[0051] The cone angle α is 10°-15°, which effectively ensures the smoothness of the test process and can smoothly convert the axial load in the vertical direction into the radial load in the horizontal direction. The setting of the cone angle not only needs to consider improving the conversion efficiency of the axial force applied in the test into the radial force of the ring specimen 3, but also needs to avoid the self-locking of the inner and outer ring wedge assembly.

[0052] like Figure 5 As shown, the upper end face of the elastic inner ring 4 is provided with an inner and outer through groove 43 spaced apart along the circumference, and the lower end face of the elastic inner ring 4 is provided with a lower through groove 44 spaced apart along the circumference. The upper groove 43 and the lower groove 44 are arranged alternately. The length of the upper groove 43 and the lower groove 44 is greater than half of the axial height dimension of the elastic inner ring 4.

[0053] The elastic inner ring 4 has a double-sided slotted structure formed by the evenly staggered grooves on both ends, which gives it radial compression elasticity and good elasticity.

[0054] like Figure 6 As shown, the lower end of the upper groove 43 and the upper end of the lower groove 44 both extend to form a circular structure 45, and the diameter of the circular structure 45 is greater than the width (b) of the upper groove 43 and the lower groove 44.

[0055] The radius of the circular structure 45 is 0.5-1mm, and the distance (l) from its center to the opening end of the groove is 2 / 3-3 / 4 of the total height of the elastic inner ring 4, so as to effectively ensure the elastic performance of the elastic inner ring 4 and its own structural strength.

[0056] The inner circumferential surface of the elastic inner ring 4 is set as a cylindrical straight surface 41 for clamping the annular specimen 3, and effectively ensures the reliability of the fit between the two and effectively ensures the uniformity of force transmission.

[0057] The elastic inner ring 4 is made of 65Mn steel and undergoes quenching heat treatment and tempering treatment at 45℃.

[0058] It also includes a pad ring 5 supported on the lower pressure plate 6. Before the test, the elastic inner ring 4 is placed on the pad ring 5 and the pad ring 5 is used to center and position the elastic inner ring 4. The top surface of the outer ring 2 is provided with an upper pressure plate 1. When the upper pressure plate 1 moves downward relative to the lower pressure plate 6, it drives the outer ring 2 to approach and fit against the elastic inner ring 4 below and apply force.

[0059] In this embodiment, the outer ring 2 and the pad ring 5 can be fixed relative to the upper pressure plate 1 and the lower pressure plate 6 respectively, ensuring their vertical alignment. Then, the pad ring 5 is aligned with the elastic inner ring 4, thus ensuring the smooth progress of the test. Alternatively, the outer ring 2 and the pad ring 5 can not be fixed to the upper pressure plate 1 and the lower pressure plate 6. Instead, the pad ring 5 is placed on the lower pressure plate 6 during the test, and the elastic inner ring 4 and the annular specimen 3 are placed on the pad ring 5 in sequence. The outer ring 2 is placed on the top surface of the elastic inner ring 4, and the level is adjusted by an external level, thus effectively ensuring the smooth progress of the test.

[0060] like Figure 7 As shown, an outer step 50 is formed along the circumferential direction at the top edge of the pad ring 5. The outer step 50 is fitted to the inner edge of the bottom surface of the elastic inner ring 4. A one-sided gap is provided between the side wall of the outer step 50 and the inner wall of the elastic inner ring 4. The size of the one-sided gap is larger than the inner shrinkage size of the elastic inner ring 4.

[0061] The gap on one side is 2-4mm.

[0062] In this embodiment, the inner diameter of the elastic inner ring 4 in its natural state is slightly larger than the outer diameter of the annular specimen 3. Of course, in actual use, opposite tolerances can be set on the basis of the same size to obtain the assembly gap, so that the annular specimen 3 can be smoothly placed inside the elastic inner ring 4 and supported horizontally on the pad ring 5 on the lower pressure plate 6. In the actual test, an external level can be used to level the test device to ensure the effectiveness and reliability of the test and its accuracy.

[0063] The testing principle of this invention is as follows:

[0064] like Figure 1 As shown, during the test, the upper pressure plate 1 drives the outer ring 2 downward. The inner conical structure 20 of the outer ring 2 contacts and squeezes inward to apply force to the elastic inner ring 4. The elastic inner ring 4 contracts radially and applies radial force to the annular specimen 3 in the circumferential direction.

[0065] By analyzing the movement of the outer ring 2 and the elastic inner ring 4 during the test, and combining the force transformation of the outer ring 2 and the elastic inner ring 4, the relationship between the uniform pressure on the annular specimen 3 and the external vertical compressive load, the stroke of the test device, and the cone angle of the inner and outer rings is analyzed. Then, the stress and strain mechanical response of the specimen under uniform pressure is analyzed to obtain the relationship between the mechanical properties of the specimen and the parameters of the test device, the applied vertical compressive load, and its own geometric parameters.

[0066] like Figure 2 As shown, when a vertical compressive load F is applied downwards, during the process of the outer ring 2 moving in contact with the elastic inner ring 4, a frictional force f2 parallel to the conical surface and a pressure N2 perpendicular to the conical surface are generated towards the elastic inner ring 4, which together form the total pressure F. R2 Then, the total pressure F R2 Decompose the sample in the horizontal and vertical directions to obtain F in the horizontal direction of the annular specimen 3. R2X and vertically downward F R2Y ,F R2X That is, the radial load F transmitted from the elastic inner ring 4 to the annular specimen 3. R2Y The downward force acts on the lower washer ring 5, with the following relationship:

[0067]

[0068] Where α is the cone angle between the outer ring 2 and the elastic inner ring 4. The friction angle between the contact cone surfaces of the outer ring 2 and the elastic inner ring 4;

[0069] The annular specimen 3 is subjected to a radial load F from the elastic inner ring 4. R2X This generates an equal and opposite reaction force N on the elastic inner ring 4. r N rDecompose the frictional force f between the two relative to each other. r The following relationship exists:

[0070] N r =F R2X

[0071] During the test, the elastic inner ring 4 is in equilibrium under forces in the vertical direction, with the following relationship:

[0072]

[0073] From relations (1) and (2), we obtain F. R2X The relationship between F and F is as follows:

[0074]

[0075] For ring specimen 3, F R2X The total radial pressure it experiences in the circumferential direction is:

[0076] F R2X =p*(2π*R0*H)

[0077] Where p is the uniformly distributed pressure on the annular specimen 3, R0 is the outer radius of the annular specimen 3, and H is the axial height of the annular specimen 3.

[0078] The relationship between the uniformly distributed pressure p and the vertical compressive load F on the annular specimen 3 can then be calculated as follows:

[0079]

[0080] As F increases, the uniformly distributed pressure p increases until the annular specimen 3 fails, at which point the maximum uniformly distributed pressure p is obtained. max Thus, the maximum circumferential compressive stress σ experienced by the annular specimen 3 was obtained. θmax for:

[0081]

[0082] Among them, R i denoted as the inner radius of the annular specimen 3.

[0083] In this embodiment, a force loading mechanism or a universal testing machine can be used to apply a vertical compressive load to the testing device. The wedge shape of the outer ring 2 and the elastic inner ring 4 is matched, and the vertical compressive load is converted into a radial compressive load along the circumference by relying on the wedge clamping force of the inner and outer rings and the radial deformation of the elastic inner ring 4. Thus, the radial compression test of the composite material ring is carried out based on the existing force loading mechanism, realizing the simulation of the external pressure test load in deep sea still water.

[0084] This invention can simulate the situation of marine equipment being subjected to uniformly distributed hydrostatic external pressure, which is conducive to carrying out a large number of experimental studies in the laboratory, and can conveniently and quickly obtain the mechanical performance parameters of deep-sea composite pressure-resistant structures, so as to understand the failure characteristics and influence laws of deep-sea pressure-resistant composite materials, support the research and development of lightweight deep-sea pressure-resistant structures, greatly enrich the performance testing methods of deep-sea pressure-resistant structures, and has the advantages of reliability, economy, ease of operation and high precision.

[0085] In one embodiment, the test objects were a set of outer diameter (R0) 162 mm and inner diameter (R... i A glass fiber composite ring specimen with a diameter of 150 mm, a height (H) of 15 mm, and a winding angle of ±55° was subjected to uniform external pressure test to study its mechanical properties and structural failure characteristics.

[0086] Based on the outer diameter (R0) of the specimen, the inner surface of the elastic inner ring 4 is first determined to be cylindrical with an opening diameter of 162 mm and a height of 18 mm. The outer surface of the elastic inner ring 4 is designed as a conical surface with a cone angle of 15°. 47 upper grooves 43 are evenly arranged along the circumference at its upper end. The top of the upper grooves 43 penetrates the elastic inner ring 4 both inside and out, but the bottom does not penetrate and ends with a circular structure 45. The radius of the circular structure 45 is 0.8 mm, and the distance from the center of the circular structure 45 to the bottom surface of the elastic inner ring 4 is 5 mm (1 / 4 to 1 / 3 of the height of the elastic inner ring 4). Similarly, 47 lower grooves 44 are evenly arranged along the circumference at the lower end of the elastic inner ring 4. The bottom of the lower grooves 44 penetrates the elastic inner ring 4 both inside and out, but the top does not penetrate and ends with a circular structure 45. The radius of the circular structure 45 is 0.8 mm, and the distance from the center of the circular structure 45 to the top surface of the elastic inner ring 4 is 5 mm.

[0087] Considering the manufacturing process, the elastic inner ring 4 has a thickness of 3mm at its small end, is made of 65Mn steel, and undergoes quenching heat treatment and medium-temperature tempering. Through process exploration, it was found that when the tempering temperature is adjusted to 45℃, the elastic inner ring 4 has suitable hardness and good elasticity, meeting the requirements of the experiment. However, tempering temperatures exceeding 50℃ will make the elastic inner ring 4 brittle, and fracture of the elastic inner ring 4 occurred during the experiment.

[0088] Based on the dimensions of the elastic inner ring 4, the outer ring 2 and the washer ring 5 are designed accordingly. The inner surface of the outer ring 2 is a conical surface with a cone angle α of 15° and a large end diameter of 172mm. The outer surface is a cylindrical surface with a diameter of 210mm and a height of 28mm. The washer ring 5 has a height of 12mm, an outer diameter of 168mm, an inner diameter of 140mm, and a boss forming an outer step 50 along the circumference. The outer step 50 has a diameter of 160mm and a height of 2mm. Both the outer ring 2 and the washer ring 5 are made of 45 steel.

[0089] The composite material ring specimens are cut from the same cylindrical shell, and both ends are ground flat. After dimensional measurement, they are installed into the processed elastic inner ring 4. The ring is adjusted so that one end face is flush with the large end of the elastic inner ring 4, and they are placed together on the pad ring 5. Then the outer ring 2 is placed on the elastic inner ring 4 to form a wedge fit. The upper pressure plate 1 is located above the outer ring 2, and the level is adjusted with the help of a level.

[0090] The testing machine is turned on for compression loading. The upper pressure plate 1 applies a downward compressive force to the outer ring 2. Based on the wedge principle, the wedge-shaped fit between the outer ring 2 and the elastic inner ring 4 converts the vertical pressure of the press into a uniform radial external pressure applied to the outer surface of the composite ring specimen. As the stroke increases, the radial compressive load on the specimen increases accordingly, and loading continues until the specimen fails.

[0091] Based on the compressive force F applied by the testing machine, combined with the parameters of the elastic inner ring 4 and the test specimen, the radially distributed external pressure p experienced by the specimen is obtained; based on the maximum compressive force F applied by the testing machine at the time of specimen failure... max The circumferential failure stress σ of the test composite specimen was obtained. θmax As shown in the table below.

[0092] Table 1 Results of uniform radial compression test on glass fiber composite ring specimens

[0093]

[0094] Therefore, the mechanical properties of the specimen can be evaluated based on the test and experimental results.

[0095] The radial compression test of the ring specimen can obtain mechanical properties including uniform pressure, circumferential failure stress, failure pressure, and failure mode, providing an experimental testing method for in-depth research on the mechanical behavior of rotary composite pressure-resistant structures under deep-sea pressure environment.

[0096] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A method for testing radially uniform compression of a composite material ring, characterized in that: The annular specimen (3) is subjected to uniform pressure and external vertical compressive load, including the following steps: Place the annular specimen (3) inside the elastic inner ring (4); The annular specimen (3) and the elastic inner ring (4) are placed together on the lower pressure plate (6), with the elastic inner ring (4) located directly below the upper outer ring (2); The outer ring (2) moves downward under the action of external force. The inner circumferential surface of the outer ring (2) matches the wedge shape of the outer circumferential surface of the elastic inner ring (4). As the outer ring (2) continues to move downward, the inner circumferential surface of the outer ring (2) and the outer circumferential surface of the elastic inner ring (4) are pressed together. The outer circumferential surface of the elastic inner ring (4) is subjected to force and radially shrinks inward. The inner wall of the elastic inner ring (4) wraps around the outer wall of the annular specimen (3) and applies a radial compressive load. The compressive load applied to the radial direction of the annular specimen (3) is calculated by combining the external force applied to the outer ring (2), the wedge angle and friction angle between the outer ring (2) and the elastic inner ring (4), and the external dimensions of the annular specimen (3).

2. The method for testing radial uniform compression of a composite material ring as described in claim 1, characterized in that: The inner circumferential surface of the outer ring (2) is formed into an inner conical structure (20) that is larger at the bottom and smaller at the top. The outer circumferential surface of the elastic inner ring (4) is set into an outer conical structure (42) that is smaller at the top and larger at the bottom. The cone angles of the inner conical structure (20) and the outer conical structure (42) are consistent, forming a matching wedge shape. The diameter of the large end of the inner conical structure (20) is larger than the diameter of the small end of the outer conical structure (42), and the diameter of the large end of the inner conical structure (20) is smaller than the diameter of the large end of the outer conical structure (42) in its natural state.

3. The method for testing radial uniform compression of a composite material ring as described in claim 2, characterized in that: The cone angle is 10°-15°.

4. The method for testing radial uniform compression of a composite material ring as described in claim 1, characterized in that: The upper end face of the elastic inner ring (4) is provided with an inner and outer through groove (43) spaced apart along the circumference, and the lower end face of the elastic inner ring (4) is provided with an inner and outer through groove (44) spaced apart along the circumference. The upper groove (43) and the lower groove (44) are arranged alternately. The length of the upper groove (43) and the lower groove (44) is greater than half of the axial height dimension of the elastic inner ring (4).

5. The method for testing radial uniform compression of a composite material ring as described in claim 4, characterized in that: The lower end of the upper groove (43) and the upper end of the lower groove (44) both extend to form a circular structure (45), and the diameter of the circular structure (45) is greater than the width of the upper groove (43) and the lower groove (44).

6. The method for testing radial uniform compression of a composite material ring as described in claim 1, characterized in that: The inner circumferential surface of the elastic inner ring (4) is set as a cylindrical straight surface (41).

7. The method for testing radial uniform compression of a composite material ring as described in claim 1, characterized in that: The elastic inner ring (4) is made of 65Mn steel and is subjected to quenching heat treatment and tempering treatment at 45°C.

8. The method for testing radial uniform compression of a composite material ring as described in claim 1, characterized in that: It also includes a pad ring (5) supported on the lower pressure plate (6). Before the test, the elastic inner ring (4) is placed on the pad ring (5) and the pad ring (5) centers and positions the elastic inner ring (4). The top surface of the outer ring (2) is provided with an upper pressure plate (1). The upper pressure plate (1) moves downward relative to the lower pressure plate (6) to drive the outer ring (2) to approach and fit against the elastic inner ring (4) below.

9. The method for testing radial uniform compression of a composite material ring as described in claim 8, characterized in that: The top edge of the pad ring (5) is provided with an outer step (50) along the circumferential direction. The outer step (50) is fitted with the inner edge of the bottom surface of the elastic inner ring (4). A single-sided gap is provided between the side wall of the outer step (50) and the inner wall of the elastic inner ring (4). The size of the single-sided gap is larger than the inner shrinkage size of the elastic inner ring (4).

10. The method for testing radial uniform compression of a composite material ring as described in claim 9, characterized in that: The single-sided gap is 2-4mm.

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