Medical metal material fatigue test fixture

Abstract

The utility model relates to medical metal testing equipment technical field discloses medical metal material fatigue test anchor clamps, including two anchor clamps and metal fatigue testing machine, the anchor clamps inside coaxial is provided with self -adaptation clamping mechanism, the upper and lower chuck of metal fatigue testing machine all are fixedly connected with the connecting seat for with anchor clamps detachable connection, the anchor clamps with the connecting seat between are provided with the centring mechanism for guaranteeing the coaxial degree of sample, the self -adaptation clamping mechanism includes 3~6 fixed blocks, the fixed block even fixedly connected along anchor clamps inner wall circumferential direction, the fixed block is connected with sliding block through the guide structure sliding, in the utility model, hydraulic device drive single annular pressure block, has guaranteed the clamping force on the transmission to multiple sliding blocks in size is completely equal, in time is completely synchronous, has overcome the problem of the uneven clamping force and sample eccentricity that traditional bolt is screwed tightly or multiple point independent drive mode is easy to produce.

Description

Technical Field

[0001] This utility model relates to the field of medical metal testing equipment technology, and in particular to a fixture for fatigue testing of medical metal materials. Background Technology

[0002] Medical-grade metallic materials, such as titanium alloys, cobalt-chromium alloys, and medical-grade stainless steel, are key materials for manufacturing medical devices that are implanted in the human body for extended periods, such as artificial joints, spinal implants, and bone plates. These implants will withstand complex alternating loads from walking and movement during their service life in the body; therefore, their fatigue resistance is a core indicator determining product safety and lifespan. To accurately assess and verify the fatigue limits of these materials, rigorous mechanical testing using fatigue testing machines is essential during the research and development and quality control stages.

[0003] In fatigue testing, the fixture, as a key component connecting the testing machine and the specimen, directly affects the accuracy and reliability of the test results. However, in terms of clamping methods, traditional fatigue testing fixtures often use mechanical bolts for tightening. During operation, it is difficult to ensure that the tightening force and sequence are absolutely consistent, easily leading to unequal clamping forces applied around the specimen. This introduces initial eccentricity and bending stress into the specimen before the test even begins. Furthermore, to ensure clamping stability, the jaws of these fixtures are usually made of hard metal. When in contact with the specimen, especially under high clamping forces, they can cause severe stress concentration on the specimen surface, even indentation. This stress concentration caused by improper clamping often leads to premature initiation of fatigue cracks at the clamping site, resulting in fracture. Consequently, the test results cannot accurately reflect the material's fatigue resistance within the effective gauge length, causing invalid test data and wasting valuable samples and testing time. Therefore, a fixture for fatigue testing of medical metal materials is proposed to address these problems. Utility Model Content

[0004] To overcome the above deficiencies, this utility model provides a fixture for fatigue testing of medical metal materials, aiming to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A fixture for fatigue testing of medical metal materials includes two fixture bodies and a metal fatigue testing machine. The fixture bodies are coaxially equipped with an adaptive clamping mechanism. The upper and lower chucks of the metal fatigue testing machine are fixedly connected to a connecting seat for detachable connection with the fixture bodies. An alignment mechanism is provided between the fixture bodies and the connecting seats to ensure the coaxiality of the sample. The adaptive clamping mechanism includes 3 to 6 fixed blocks, which are uniformly fixedly connected along the circumferential direction of the inner wall of the clamping body. The fixed blocks are slidably connected to sliding blocks through a guide structure. The top of the sliding blocks has an arc-shaped opening. A hydraulic device is fixedly installed on the top of the inner wall of the clamping body. An annular pressure block is fixedly connected to the output end of the hydraulic device. A T-shaped slider matching the number of sliding blocks is fixedly connected to the bottom end of the annular pressure block along the circumferential direction. The T-shaped slider is slidably connected inside the sliding blocks through a reset structure. A V-shaped groove is opened on the side of the sliding block near the center of the clamping body. A pad is installed on the inner wall of the V-shaped groove through a connecting structure. As a further description of the above technical solution: The guiding structure includes a guide groove formed inside the fixed block, and an inclined slider is fixedly connected to the side of the sliding block near the fixed block. The outer wall of the inclined slider is slidably connected to the inner wall of the guide groove. As a further description of the above technical solution: The bottom of the guide groove is fixedly connected to a limiting block for limiting the sliding stroke of the inclined slider, and the side of the inclined slider closer to the center of the clamping body contacts the side of the limiting block away from the fixed block. As a further description of the above technical solution: The bottom side of the annular pressure block slides in contact with the inner wall of the arc-shaped opening. The reset structure includes multiple reset springs. The side of the T-shaped slider near the fixed block abuts against the side of the reset spring near the T-shaped slider. The side of the reset spring away from the T-shaped slider abuts against the inner wall of the T-shaped groove. As a further description of the above technical solution: The top of the arc-shaped opening is provided with a T-shaped groove. The inner wall of the T-shaped groove is fixedly connected to a guide rod for guiding the sliding of the T-shaped slider. The outer wall of the T-shaped slider is slidably connected to the inner wall of the T-shaped groove. The inner wall of the T-shaped slider and the outer wall of the guide rod are in clearance fit. A return spring in a pre-compressed state is sleeved on the outside of the guide rod. As a further description of the above technical solution: The connection structure includes multiple threaded holes opened along the depth direction of the V-groove, and the sliding block is fixedly mounted with a gasket by multiple medical-grade fastening bolts, and the fastening bolts are threadedly engaged with the threaded holes. As a further description of the above technical solution: The centering mechanism includes a fixed rod coaxially arranged with the clamp body. One end of the fixed rod is vertically fixedly connected to the center of the end of the clamp body. A spherical block is fixedly connected to the side of the fixed rod away from the clamp body. A spherical groove that fits the spherical block is opened at the end of the connecting seat opposite to the clamp body. As a further description of the above technical solution: Multiple butterfly springs are uniformly fixedly connected to one end of the connecting seat relative to the clamping body along the circumferential direction. The butterfly springs are in a pre-compressed state and are used to provide a centering pre-tightening force. The side of the butterfly spring away from the connecting seat is in elastic contact with the end of the clamping body.

[0006] This utility model has the following beneficial effects: 1. In this utility model, a single annular pressure block is driven by a hydraulic device, ensuring that the clamping force transmitted to 3 to 6 sliding blocks is completely equal in magnitude and completely synchronized in time. This fundamentally overcomes the problems of uneven clamping force and sample eccentricity that are easily generated by traditional bolt tightening or multi-point independent driving methods. Furthermore, the V-shaped groove and replaceable flexible pad on the sliding block upgrade the traditional "point" or "line" contact to "surface" contact, which greatly disperses the clamping stress and effectively avoids the formation of indentations or stress concentration sources on the sample surface. This prevents the sample from prematurely fatigue-fractured at the clamping end, thereby ensuring that fatigue failure occurs within the effective gauge length of the sample and ensuring the authenticity and reliability of the test data.

[0007] 2. In this utility model, the ball joint formed by the spherical block and the spherical groove gives the clamp body the freedom of "omnidirectional floating" and the butterfly spring provides the preload that can be overcome. Unlike the traditional rigid connection method that relies on complicated and time-consuming manual adjustment, this structure can passively and automatically drive the clamp body to complete the precise angle adjustment at the moment of test loading by using the small bending moment generated by the misalignment of the sample itself until the sample axis is completely aligned with the force axis of the testing machine, thereby improving the efficiency and accuracy of fatigue life testing. Attached Figure Description

[0008] Figure 1 This is a perspective view of the medical metal material fatigue testing fixture proposed in this utility model; Figure 2 This is a schematic diagram of the connecting seat of the medical metal material fatigue testing fixture proposed in this utility model; Figure 3 This is a schematic diagram of the fixing block of the medical metal material fatigue testing fixture proposed in this utility model; Figure 4 This is a schematic diagram of the fixture body for the medical metal material fatigue testing fixture proposed in this utility model; Figure 5 for Figure 4 Enlarged view of point A in the middle; Figure 6 This is a schematic diagram of the sliding block of the medical metal material fatigue testing fixture proposed in this utility model.

[0009] Legend: 1. Clamp body; 2. Connecting seat; 3. Metal fatigue testing machine; 4. Fixing block; 5. Sliding block; 6. Arc-shaped opening; 7. Annular pressure block; 8. T-shaped slider; 9. Return spring; 10. Guide rod; 11. T-shaped slide groove; 12. Guide groove; 13. Inclined slider; 14. Limiting block; 15. Pad; 16. Fastening bolt; 17. Fixing rod; 18. Spherical block; 19. Butterfly spring. Detailed Implementation

[0010] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0011] Reference Figure 1 An embodiment of this utility model provides a medical metal material fatigue testing fixture, including two fixture bodies 1 and a metal fatigue testing machine 3. The fixture body 1 is coaxially provided with an adaptive clamping mechanism. The upper and lower clamps of the metal fatigue testing machine 3 are fixedly connected with connecting seats 2 for detachable connection with the fixture body 1. An alignment mechanism is provided between the fixture body 1 and the connecting seat 2 to ensure the coaxiality of the sample. Reference Figure 3 , Figure 4 and Figure 6 The adaptive clamping mechanism includes 3 to 6 fixed blocks 4, which are uniformly fixedly connected along the circumferential direction of the inner wall of the clamping body 1. The fixed blocks 4 are slidably connected to sliding blocks 5 through a guide structure. The top of the sliding blocks 5 is provided with an arc-shaped opening 6. A hydraulic device is fixedly installed on the top of the inner wall of the clamping body 1. In this embodiment, the hydraulic device can be an integrated micro hydraulic cylinder, which is connected to a manual or electric hydraulic pump through an external oil circuit interface. The structure is compact. The output end of the hydraulic device is fixedly connected to an annular pressure block 7. The annular pressure block 7 is a force transmission and distribution element as a whole, which ensures that the hydraulic pressure can be applied synchronously and equally to each sliding block 5. The bottom end of the annular pressure block 7 is fixedly connected with a T-shaped slider 8 that matches the number of sliding blocks 5 along the circumferential direction. The T-shaped slider 8 is slidably connected inside the sliding block 5 through a reset structure. A V-shaped groove is opened on the side of the sliding block 5 near the center of the clamping body 1. A pad 15 is installed on the inner wall of the V-shaped groove through a connecting structure. The design of the V-shaped groove is particularly suitable for rod-shaped or cylindrical samples. It can provide two-line contact during clamping and play an auxiliary role in automatic centering. The pad 15 is preferably an engineering plastic or soft metal with a hardness lower than that of the sample material. Its function is to increase the contact area, disperse the clamping stress, and protect the sample surface from being crushed or generating stress concentration sources as a vulnerable part. The guiding structure includes a guide groove 12 formed inside the fixed block 4. A slanted slider 13 is fixedly connected to the side of the sliding block 5 near the fixed block 4. The outer wall of the slanted slider 13 is slidably connected to the inner wall of the guide groove 12. The cooperation between the slanted slider 13 and the guide groove 12 ensures that the sliding block 5 can only perform pure radial reciprocating motion, avoiding deflection or tilting when subjected to force, and ensuring the stability of clamping. A limiting block 14 for limiting the sliding stroke of the slanted slider 13 is fixedly connected to the bottom of the guide groove 12. The side of the slanted slider 13 near the center of the clamping body 1 contacts the side of the limiting block 14 away from the fixed block 4. The limiting block 14 defines the limit position of the centrifugal reset of the sliding block 5, preventing it from coming out of the guide groove 12. Reference Figure 4 and Figure 5 The bottom side of the annular pressure block 7 slides in contact with the inner wall of the arc-shaped opening 6. The arc-shaped design allows the axial thrust of the annular pressure block 7 to be smoothly converted into the radial driving force on the sliding block 5. The reset structure includes multiple reset springs 9. The side of the T-shaped slider 8 near the fixed block 4 abuts against the side of the reset spring 9 near the T-shaped slider 8. The side of the reset spring 9 away from the T-shaped slider 8 abuts against the inner wall of the T-shaped groove 11. The top of the arc-shaped opening 6 is provided with a T-shaped groove 11. The inner wall of the T-shaped groove 11 is fixedly connected to a guide rod 10 for guiding the sliding of the T-shaped slider 8. The outer wall of the T-shaped slider 8 is slidably connected to the inner wall of the T-shaped groove 11. The inner wall of the T-shaped slider 8 and the outer wall of the guide rod 10 are in clearance fit. The reset spring 9 in the pre-compressed state is sleeved on the outside of the guide rod 10. The main function of the guide rod 10 is to provide support for the reset spring 9, prevent it from bending and becoming unstable during compression, and provide additional guidance for the linear movement of the T-shaped slider 8. Reference Figure 6 The connection structure includes multiple threaded holes along the depth direction of the V-groove. The sliding block 5 is fixedly mounted with a gasket 15 by multiple medical-grade fastening bolts 16. The fastening bolts 16 are threadedly engaged with the threaded holes. The fastening bolts 16 are medical-grade fastening bolts, which can ensure that the connection itself will not affect the test environment or fail due to rust during corrosion fatigue testing. The threaded connection method makes the replacement of the gasket 15 simple and quick, greatly improving the maintainability of the fixture and its adaptability to different samples.

[0012] Reference Figure 1 and Figure 2The centering mechanism includes a fixed rod 17 coaxially arranged with the clamp body 1. One end of the fixed rod 17 is vertically fixed to the center of the end of the clamp body 1. A spherical block 18 is fixedly connected to the side of the fixed rod 17 away from the clamp body 1. A spherical groove with clearance fit to the spherical block 18 is opened at one end of the connecting seat 2 opposite to the clamp body 1. The spherical block 18 and the spherical groove together form a ball joint, which is the core pivot for realizing universal floating adjustment. The gap between the spherical block 18 and the spherical groove can be filled with high-viscosity damping grease to increase the smoothness of the centering process and absorb high-frequency vibrations; the connecting seat 2... Multiple butterfly springs 19 are uniformly fixed to one end of the clamp body 1 along the circumferential direction. The butterfly springs 19 are in a pre-compressed state and are used to provide centering pre-tightening force. The side away from the connecting seat 2 is in elastic contact with the end of the clamp body 1. The butterfly springs 19 can not only stabilize the clamp body 1 in the initial center position when there is no load, but more importantly, the magnitude of the pre-tightening force they provide is precisely calculated and must be less than the eccentric torque caused by misalignment during the initial loading of the test, thereby ensuring that the automatic centering function can be reliably triggered and that the clamp body 1 automatically resets after the load is removed.

[0013] Working principle: During the clamping operation, the operator first places the medical metal material sample in the center of the upper and lower clamping bodies 1, and then activates the hydraulic device built into the top of the clamping body 1. The hydraulic device drives the annular pressure block 7 connected to its output end to produce axial displacement. During the downward movement of the bottom side of the annular pressure block 7, its surface will make sliding contact with the inner wall of the arc-shaped opening 6 at the top of all the sliding blocks 5. This contact decomposes the axial thrust of the annular pressure block 7 into a radial component force acting on each sliding block 5. Since the annular pressure block 7 is a whole, this component force is applied evenly and synchronously to 3 to 6 sliding blocks 5, driving them to slide smoothly towards the center in the guide structure of their respective fixed blocks 4. Finally, the pads 15 in the V-shaped grooves of the sliding blocks 5 clamp the sample with completely equal force from multiple directions. When it is necessary to release the sample, the hydraulic device is depressurized. Under the action of the pre-compressed return spring 9, the T-shaped slider 8 is pushed back to the initial position, thereby driving the annular pressure block 7 to reset, the clamping force disappears, and the release is completed. The clamp body 1 is connected to the connecting seat 2 fixed on the testing machine through an alignment mechanism. The core of this alignment mechanism is a ball joint consisting of a spherical block 18 at the end of the fixed rod 17 and a spherical groove on the connecting seat 2. It allows the clamp body 1 to make small, arbitrary angular deflections relative to the connecting seat 2. When the specimen is installed, even if there are small angular or positional deviations, the preload provided by the evenly distributed disc spring 19 will keep the clamp in an initial stable state. When the fatigue test begins and the testing machine applies an axial load, any misalignment will generate an additional bending moment on the specimen. This moment will instantly overcome the preload of the disc spring 19 and drive the clamp body 1 to passively deflect and adjust around the center of the spherical block 18 until the axis of the specimen itself is completely coincident with the force loading axis of the metal fatigue testing machine 3. At this time, the bending moment disappears, thus automatically and accurately ensuring the coaxiality of the specimen and ensuring the accuracy of the test results.

[0014] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A fixture for fatigue testing of medical metal materials, comprising two fixture bodies (1) and a metal fatigue testing machine (3), characterized in that: The clamping body (1) is coaxially provided with an adaptive clamping mechanism inside. The upper and lower clamps of the metal fatigue testing machine (3) are fixedly connected with a connecting seat (2) for detachable connection with the clamping body (1). A centering mechanism is provided between the clamping body (1) and the connecting seat (2) to ensure the coaxiality of the sample. The adaptive clamping mechanism includes 3 to 6 fixed blocks (4), which are uniformly fixedly connected along the circumferential direction of the inner wall of the clamping body (1). The fixed blocks (4) are slidably connected to sliding blocks (5) through a guide structure. The top of the sliding blocks (5) is provided with an arc-shaped opening (6). A hydraulic device is fixedly installed on the top of the inner wall of the clamping body (1). The output end of the hydraulic device is fixedly connected to an annular pressure block (7). The bottom end of the annular pressure block (7) is fixedly connected along the circumferential direction with a T-shaped slider (8) matching the number of sliding blocks (5). The T-shaped slider (8) is slidably connected inside the sliding block (5) through a reset structure. A V-shaped groove is provided on the side of the sliding block (5) near the center of the clamping body (1). A pad (15) is installed on the inner wall of the V-shaped groove through a connecting structure.

2. The fixture for fatigue testing of medical metal materials according to claim 1, characterized in that: The guide structure includes a guide groove (12) formed inside the fixed block (4), and a slanted slider (13) is fixedly connected to the side of the sliding block (5) near the fixed block (4). The outer wall of the slanted slider (13) is slidably connected to the inner wall of the guide groove (12).

3. The fixture for fatigue testing of medical metal materials according to claim 2, characterized in that: The bottom of the guide groove (12) is fixedly connected to a limiting block (14) for limiting the sliding stroke of the inclined slider (13). The side of the inclined slider (13) near the center of the clamping body (1) is in contact with the side of the limiting block (14) away from the fixed block (4).

4. The fixture for fatigue testing of medical metal materials according to claim 1, characterized in that: The bottom side of the annular pressure block (7) slides in contact with the inner wall of the arc-shaped opening (6). The reset structure includes multiple reset springs (9). The side of the T-shaped slider (8) near the fixed block (4) abuts against the side of the reset spring (9) near the T-shaped slider (8). The side of the reset spring (9) away from the T-shaped slider (8) abuts against the inner wall of the T-shaped groove (11).

5. The fixture for fatigue testing of medical metal materials according to claim 4, characterized in that: The top of the arc-shaped opening (6) is provided with a T-shaped groove (11). The inner wall of the T-shaped groove (11) is fixedly connected with a guide rod (10) for guiding the sliding of the T-shaped slider (8). The outer wall of the T-shaped slider (8) is slidably connected to the inner wall of the T-shaped groove (11). The inner wall of the T-shaped slider (8) is clearance-fitted with the outer wall of the guide rod (10). The reset spring (9) in the pre-compressed state is sleeved on the outside of the guide rod (10).

6. The fixture for fatigue testing of medical metal materials according to claim 1, characterized in that: The connection structure includes multiple threaded holes opened along the depth direction of the V-groove. The sliding block (5) is fixedly installed with a gasket (15) by multiple medical-grade fastening bolts (16). The fastening bolts (16) are threadedly engaged with the threaded holes.

7. The fixture for fatigue testing of medical metal materials according to claim 1, characterized in that: The centering mechanism includes a fixed rod (17) coaxially arranged with the clamp body (1). One end of the fixed rod (17) is vertically fixedly connected to the center of the end of the clamp body (1). A spherical block (18) is fixedly connected to the side of the fixed rod (17) away from the clamp body (1). The connecting seat (2) has a spherical groove that is clearance-fitted with the spherical block (18) at one end opposite to the clamp body (1).

8. The fixture for fatigue testing of medical metal materials according to claim 7, characterized in that: The connecting seat (2) is uniformly fixedly connected with a plurality of butterfly springs (19) along the circumferential direction at one end of the clamping body (1). The butterfly springs (19) are in a pre-compressed state and are used to provide a centering pre-tightening force. The side of the butterfly springs (19) away from the connecting seat (2) is in elastic contact with the end of the clamping body (1).

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