Fixture and fixture system suitable for fatigue test of shaft tube

Abstract

The invention discloses a clamp and a clamp system suitable for a shaft tube fatigue test, the clamp comprises a base, a second clamping assembly and a plurality of buffer assemblies, the base is provided with a support block, and the support block is provided with a first clamping assembly; the second clamping assembly is arranged above the base, and the second clamping assembly and the first clamping assembly are located on the same horizontal plane; each buffer assembly comprises a spring damper and a baffle, the spring damper is arranged on the base, the baffle is arranged on the spring damper, and the baffle is arranged below the second clamping assembly. The two ends of the tested axle tube are fixed through the first clamping assembly and the second clamping assembly respectively, during testing, the axle tube fatigue test is carried out by applying a load to the end of the second clamping assembly, when the axle tube breaks suddenly, impact energy can be effectively absorbed, structural vibration is reduced, and fragment splashing is reduced; therefore, the safety of testers and the equipment integrity are guaranteed.

Description

Technical Field

[0001] This invention relates to the technical field of fatigue testing, specifically to a fixture and fixture system suitable for fatigue testing of shafts and tubes. Background Technology

[0002] In key sectors such as machinery manufacturing, automotive, aerospace, and wind power generation, shaft and tube components (such as drive shafts, half-shafts, and main shafts) are among the most fundamental and crucial load-bearing structures. These shafts and tubes often bear complex loads in actual operating conditions, with cantilever fatigue loading being an extremely common and demanding stress form. For example, automotive drive half-shafts must withstand bending moments from the wheels; wind turbine main shafts generate enormous cantilever bending moments under wind loads. To ensure the reliability and safety of the entire equipment, thorough mechanical performance testing of shafts and tubes is essential during product development, manufacturing, and quality inspection, including cantilever fatigue loading tests simulating actual operating conditions. In such tests, the key to successful testing and accurate data acquisition lies in accurately, reliably, and efficiently transferring the load applied by the testing machine to the designated location on the shaft and tube, while ensuring that the clamping process does not damage the workpiece itself. The device responsible for this core task is the cantilever fatigue loading fixture. The performance of the fixture directly determines the accuracy, efficiency, and cost of the test.

[0003] Currently available testing devices generate excessive impact force during shaft tube breakage, which can easily pose a danger to the surrounding environment and damage the clamping components. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention provides a fixture and fixture system suitable for shaft and tube fatigue testing.

[0005] According to a first aspect of the present invention, a fixture suitable for shaft and tube fatigue testing includes: The base is provided with a support block, and the support block is provided with a first clamping assembly; The second clamping assembly is disposed above the base, and the second clamping assembly and the first clamping assembly are located on the same horizontal plane; Multiple buffer components, each buffer component including a spring damper and a baffle, wherein the spring damper is disposed on the base, the baffle is disposed on the spring damper, and the baffle is disposed below the second clamping component.

[0006] A fixture for shaft and tube fatigue testing according to an embodiment of the present invention has at least the following beneficial effects: The two ends of the tested shaft tube are fixed by the first clamping assembly and the second clamping assembly, respectively. During the test, a load is applied to the end of the second clamping assembly to conduct a fatigue test on the shaft tube. When the shaft tube suddenly breaks, it can effectively absorb impact energy, reduce structural vibration and reduce fragmentation, thereby ensuring the safety of test personnel and the integrity of the equipment.

[0007] According to some embodiments of the present invention, a plurality of the buffer components are disposed on the base.

[0008] According to some embodiments of the present invention, the first clamping assembly includes two clamping jaws and a connector, the two clamping jaws forming a shaft tube clamping cavity, and both ends of the two clamping jaws being detachably connected and fixed by the connector.

[0009] According to some embodiments of the present invention, the first clamping component may be detached from the support block.

[0010] According to some embodiments of the present invention, the base is provided with a counterweight, and the counterweight and the support block are respectively disposed at both ends of the support block.

[0011] According to some embodiments of the present invention, the support block and the base are provided with inclined reinforcing blocks, and the support block, the base, the inclined reinforcing blocks and the counterweight are integrally arranged.

[0012] According to a second aspect of the present invention, a fixture system for shaft and tube fatigue testing includes a fixture for shaft and tube fatigue testing as described in any one of the above-mentioned embodiments and a fatigue testing machine. The fatigue testing machine is provided with a fixed clamping end and a movable clamping end, the base is disposed on the movable clamping end, and the second clamping assembly is fixed to the fixed clamping end.

[0013] According to some embodiments of the present invention, the fixed clamping end includes a self-centering clamp, the self-centering clamp includes an outer clamping body and a floating inner sleeve, the outer clamping body is provided with a cylindrical inner cavity, and the floating inner sleeve is coaxially disposed in the inner cavity of the outer clamping body for detachable connection with the first clamping assembly; Among them, multiple rows of roller bearings are evenly arranged circumferentially between the inner wall of the outer clamp and the outer wall of the floating inner sleeve. The axis of the roller bearings is perpendicular to the central axis of the self-centering chuck, so that the floating inner sleeve can make a small radial translation relative to the outer clamp and / or a small deflection around an axis perpendicular to the central axis.

[0014] According to some embodiments of the present invention, the movable clamping end is provided with a leveling structure.

[0015] According to some embodiments of the present invention, the fatigue testing machine includes a servo fatigue testing machine body, which includes a servo actuator; The movable clamping end is connected to the servo actuator; The measurement and control system is communicatively connected to the servo actuator and is used to control the servo actuator to apply an axial cyclic load to the tested shaft tube and to collect test data in real time.

[0016] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a schematic diagram of the structure of a fixture suitable for shaft tube fatigue testing according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a fixture suitable for shaft tube fatigue testing according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a fixture system suitable for shaft and tube fatigue testing according to an embodiment of the present invention.

[0018] Icon labels: Base 100, support block 110, inclined reinforcing block 120, counterweight block 130, first clamping assembly 200, second clamping assembly 300, buffer assembly 400, spring damper 410, baffle 420, fatigue testing machine 500, fixed clamping end 510, self-centering chuck 511, movable clamping end 520, high-strength cast iron frame 530, and tested shaft tube 600. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0020] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, etc., are based on the orientation or positional relationship shown in the drawings and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0021] In the description of this invention, "multiple" refers to two or more. The use of "first" and "second" is for distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features or their sequential relationship.

[0022] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are some embodiments of the present invention, not all embodiments.

[0024] Reference Figures 1 to 2 In some embodiments, a fixture suitable for shaft and tube fatigue testing includes a base 100, a second clamping assembly 300, and four buffer assemblies 400. The base 100 is provided with a support block 110 and is fixed to the test platform foundation by high-strength bolts. The base 100 is made of high-strength steel and has a chrome-plated surface for rust prevention. The support block 110 is provided with a first clamping assembly 200; the second clamping assembly 300 is located above the base 100 and is on the same horizontal plane as the first clamping assembly 200. The first clamping assembly 200 and the second clamping assembly 300 are spaced apart from each other. Both the first clamping assembly 200 and the second clamping assembly 300 include two clamping jaws and a connector. The two clamping jaws form a shaft and tube clamping cavity. Both ends of the two clamping jaws are detachably connected and fixed by the connector, which is a bolt. The shaft and tube 600 to be tested is placed horizontally between the two clamping jaws and fixed by the clamping force of the clamping jaws. The clamping surfaces of the caliper jaws are lined with rubber pads to prevent damage to the shaft tube surface, providing a clamping force of up to 500N and ensuring no slippage. The overall dimensions of this fixture are designed based on the working space of a standard fatigue testing machine 500, with a total length controlled within 800mm, a width of 300mm, and a height of 250mm. This dimensional design ensures sufficient structural rigidity while facilitating installation and use on most fatigue testing machines 500. The buffer assembly 400 includes a spring damper 410 and a baffle 420. The spring damper 410 is located on the base 100, and the baffle 420 is located below the spring damper 410 and below the second clamping assembly 300. The spring damper 410 is installed in a hole in the base 100, with its installation axis aligned with the force direction of the support, ensuring that the impact force is transmitted along the correct path. A 5mm dynamic gap is maintained between the lower surface of the baffle 420 and the support surface of the spring damper 410, which does not affect the micro-deformation during normal testing and can intervene promptly in case of overload. Furthermore, the height of the baffle 420 from the surface of the base 100 can be adjusted according to the bending strength of the tested shaft tube 600 to achieve a better buffering and absorption effect.

[0025] During testing, the two ends of the tested shaft tube 600 are fixed by the first clamping assembly 200 and the second clamping assembly 300, respectively. During the test, a load is applied to the end of the second clamping assembly 300 to conduct a fatigue test on the shaft tube. When the shaft tube experiences a sudden fracture, it can effectively absorb impact energy, reduce structural vibration, and reduce fragmentation, thereby ensuring the safety of test personnel and the integrity of the equipment.

[0026] According to some embodiments of the present invention, the first clamping assembly 200 is detachable from the support block 110 to fix shaft tubes of different diameters. Of course, it is also possible to adapt to shaft tubes of different diameters by adjusting the connecting parts.

[0027] According to some embodiments of the present invention, the base 100 is provided with a counterweight 130, and the counterweight 130 and the support block 110 are respectively disposed at both ends of the support block 110. During the clamping process, the base 100 can be placed stably and will not tip over.

[0028] According to some embodiments of the present invention, the support block 110 and the base 100 are provided with inclined reinforcing blocks 120. The support block 110, the base 100, the inclined reinforcing blocks 120 and the counterweight block 130 are integrally arranged, which can improve the structural strength.

[0029] Reference Figure 3 According to an embodiment of the second aspect of the present invention, a fixture system suitable for shaft and tube fatigue testing includes a fixture suitable for shaft and tube fatigue testing and a fatigue testing machine 500, as described above. The fatigue testing machine 500 includes a servo fatigue testing machine body, which comprises a servo actuator, a high-strength cast iron frame 530, a fixed clamping end 510, and a movable clamping end 520. The high-strength cast iron frame 530 provides stable rigid support. The movable clamping end 520 is connected to the servo actuator, and the measurement and control system is communicatively connected to the servo actuator to control the servo actuator to apply an axial cyclic load to the tested shaft tube 600 and to acquire test data in real time. The base 100 is located at the movable clamping end 520, and the second clamping assembly 300 is fixed to the fixed clamping end 510.

[0030] The fixed clamping end 510 is connected to the actuator of the moving crossbeam of the testing machine via its flange. The fixed clamping end 510 also includes a self-centering chuck 511 with internal roller bearings, which allows the clamp to automatically fine-tune to compensate for possible coaxiality deviations of the shaft when subjected to huge axial tensile and compressive fatigue loads, ensuring that the load is accurately transmitted along the shaft tube axis and avoiding the introduction of additional bending stress.

[0031] Specifically, the outer clamp is a rigid shell with a precisely machined cylindrical cavity inside to accommodate and support other components. One end of the outer clamp is provided with a connecting flange for rigid connection with the fixed clamping end 510.

[0032] The floating inner sleeve is coaxially disposed within the cylindrical inner cavity of the outer clamping body. One end of the floating inner sleeve is designed with an interface for detachable connection with the first clamping assembly 200 that holds the shaft tube, for example, by means of threads, tapered surfaces, or quick-change slots.

[0033] To achieve the core function of automatic centering, multiple rows of roller bearings are evenly arranged circumferentially within the annular space between the inner wall of the outer clamping body and the outer wall of the floating inner sleeve. The mounting axes of these roller bearings are all perpendicular to the central axis of the self-centering chuck 511. This arrangement creates a low-friction, high-rigidity kinematic pair.

[0034] Its working principle is as follows: When the tested shaft tube has a slight coaxiality deviation due to installation, in the initial stage of applying axial load, the force will cause the floating inner sleeve to produce adaptive movement through the roller bearing. Specifically, the floating inner sleeve can make a very small radial translation relative to the fixed outer clamp, and / or make a slight angular deflection around an axis perpendicular to the central axis. This adaptive adjustment process can effectively eliminate the additional bending stress caused by misalignment, ensuring that the axial load is accurately transmitted along the shaft tube axis. After adjustment, the entire mechanism remains stable under load, and the roller bearing continues to bear the high-cycle axial load.

[0035] The movable clamping end 520 is fixed to the worktable of the testing machine by its base, and the movable clamping end 520 is equipped with a leveling structure to level the shaft tube when fixing it, so as to ensure that the shaft tube is arranged in a horizontal direction, so as to facilitate the control of the load direction applied to the shaft tube.

[0036] The movable clamping end 520 is the direct actuation end for applying loads. It is structurally symmetrical or similar to the fixed clamping end 510, together forming a fixed support for both ends of the shaft tube. The clamping part of the fixture can adopt a V-shaped jaw design. The working surface of the jaws is hardened and engraved with anti-slip textures to provide high static friction and prevent the device from slipping or loosening during testing. The jaw specifications are interchangeable to accommodate plates of different thicknesses.

[0037] The tested shaft tube 600 is vertically mounted on the shaft tube fatigue testing fixture. During installation, the clamping jaws of the shaft tube fatigue testing fixture and the second clamping assembly 300 are first fixed to the fatigue testing machine 500 via the upper and lower fixed bases 100. Then, the shaft tube is accurately placed into the arc-shaped positioning groove of the clamping jaws of the first clamping assembly 200. Next, the movable clamping end 520 of the fatigue testing machine 500 is driven upwards and aligns with the upper end of the shaft tube. Finally, a preset clamping force is applied to firmly fix the shaft tube. This installation structure saves space and facilitates observation of surface changes in the shaft tube under cyclic loading, such as the initiation and propagation of cracks.

[0038] During testing, the servo actuator of the testing machine applies a high-frequency axial cantilever cyclic load to the movable clamping end 520. The magnitude, frequency, and number of cycles of the load are set and monitored by the measurement and control system. This system can acquire load-displacement data in real time and plot fatigue curves until the shaft tube reaches the preset number of failure cycles or fractures, thereby completing the evaluation of its fatigue performance. The measurement and control system typically includes force sensors, displacement sensors, and a computer controller. Alternatively, a high-frequency axial cantilever cyclic load can be applied to the fixed clamping end 510 to perform fatigue performance testing on the tested shaft tube 600.

[0039] The operator first securely mounts the fixture of this invention onto the base 100 or worktable of the fatigue testing machine using bolts through the mounting holes on its bottom, such as anchor bolt holes or U-grooves. Ensure the mounting plane of the fixture is in close contact with the plane of the testing machine base 100, and use a level to correct the levelness of the fixture. Accurate positioning of the fixture is a prerequisite for successful testing.

[0040] The shaft tube to be tested (600mm) is placed horizontally in the V-jaws or dedicated clamping cavity of the fixture. The control system drives the clamp to apply a specified preload force to the shaft tube, securing it firmly. This step ensures that one end of the shaft tube is clamped while the other end remains free, forming a standard cantilever configuration.

[0041] Connect the output end of the loading cylinder of the fatigue testing machine to the loading interface of the fixture or the free end of the shaft tube. If it is a hydraulic or electro-hydraulic servo system, ensure that the hydraulic lines or electrical wiring are connected correctly and securely. Simultaneously, connect all sensor lines, such as force sensors and displacement sensors, to the control computer. This step establishes the power transmission path between the loading cylinder and the fixture / shaft tube sample, and connects the measurement system to the control computer, preparing for testing.

[0042] Set the test parameters in the control computer's software interface, including load amplitude, frequency, waveform (e.g., sine wave, triangle wave), and number of cycles. After confirming the parameters are correct, start the test program. The loading cylinder will begin working according to the instructions, applying a periodic load to the cantilevered shaft sample. The control computer sends instructions to the loading cylinder, which executes the action, applying the load to the shaft sample fixed by the clamp. During the test, the control computer's data acquisition system will monitor and record data such as load, displacement, and number of cycles in real time. The operator must closely monitor the data curves for any abnormalities. When the preset number of cycles is reached, or when shaft breakage is detected, the testing machine will automatically or manually stop. Subsequently, the system unloads the load, releases the clamp, and carefully removes the tested shaft sample. Save all test data, clean up the site, and complete the entire test process. Throughout the process, the control computer is responsible for monitoring and recording, and the loading cylinder, under control, maintains reliable constraint on the fixed end of the sample until the test is completed.

[0043] This invention significantly improves fixing stability and loading accuracy through the clamp and self-centering chuck 511, avoiding slippage and eccentricity problems, and increasing test accuracy by more than 20%. At the same time, the integrated buffer mechanism reduces safety hazards, improves operational efficiency, adapts to various shaft and tube specifications, eliminates the need for frequent component replacements, and reduces costs and time.

[0044] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0045] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A fixture suitable for shaft tube fatigue testing, characterized by, The utility model relates to a kind of fatigue testing machine and fixture, including: Base (100) is equipped with support block (110), and the support block (110) is equipped with first clamping component (200); Second clamping component (300) is equipped above the base (100), and the second clamping component (300) is located in the same horizontal plane with the first clamping component (200); Multiple buffer components (400), the buffer component (400) includes spring damper (410) and baffle (420), the spring damper (410) is equipped in the base (100), the baffle (420) is equipped in the spring damper (410), and the baffle (420) is equipped below the second clamping component (300).

2. The fixture for fatigue testing of a shaft tube according to claim 1, wherein Multiple buffer components (400) are evenly arranged on the base (100).

3. The fixture for fatigue testing of shaft tubes as claimed in claim 1, wherein, The first clamping component (200) includes two calipers and a connecting piece, the two calipers form a shaft tube clamping cavity, and the two ends of the two calipers are detachably connected and fixed by the connecting piece.

4. The fixture for fatigue testing of shaft tubes as claimed in claim 1, wherein, The first clamping component (200) can be detachably arranged on the support block (110).

5. The fixture for fatigue testing of shaft tubes as claimed in claim 1, wherein, The base (100) is provided with a counterweight block (130), and the counterweight block (130) and the support block (110) are respectively arranged at the two ends of the support block (110).

6. The fixture for fatigue testing of shaft tubes as claimed in claim 1, wherein, The support block (110) and the base (100) are provided with an inclined reinforcing block (120), and the support block (110), the base (100), the inclined reinforcing block (120) and the counterweight block (130) are integrally arranged.

7. A clamp system suitable for shaft tube fatigue testing, characterized in that, The utility model relates to a kind of fatigue testing machine and fixture, including:

8. The fixture system for fatigue testing of shaft tubes as claimed in claim 7, wherein, A fixture suitable for shaft tube fatigue testing according to any one of claims 1 to 6, a fatigue testing machine (500) is provided with a fixed clamping end (510) and a movable clamping end (520), the base (100) is arranged on the movable clamping end (520), and the second clamping component (300) is fixed on the fixed clamping end (510). The fixed clamping end (510) includes a self-centering chuck (511), the self-centering chuck (511) includes an outer chuck body and a floating inner sleeve, the outer chuck body is provided with a cylindrical inner cavity, and the floating inner sleeve is coaxially arranged in the inner cavity of the outer chuck body and is detachably connected with the first clamping component (200); 9. The clamp system of claim 7, wherein, Wherein, a plurality of rows of roller bearings are evenly arranged between the inner cavity wall of the outer chuck body and the outer wall of the floating inner sleeve in the circumferential direction, the axis of the roller bearing is perpendicular to the central axis of the self-centering chuck (511), so that the floating inner sleeve can be slightly radially translated and / or slightly deflected around the axis perpendicular to the central axis relative to the outer chuck body.

10. The clamp system of claim 8, wherein, The movable clamping end (520) is provided with a leveling structure. The fatigue testing machine (500) includes a servo fatigue testing machine main body, which includes a servo actuator; The movable clamping end (520) is connected with the servo actuator; A measurement and control system is in communication connection with the servo actuator, for controlling the servo actuator to apply cyclic axial load to the measured shaft tube (600), and collecting test data in real time.

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