A fixture for a small round bar tensile test specimen
By designing a fixture for small round bar tensile specimens, the problem of the chuck being unable to effectively hold small specimens was solved, enabling the smooth conduct of the test and the accuracy of the data, thus improving the test efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- CHONGQING GEARBOX
- Filing Date
- 2025-05-22
- Publication Date
- 2026-05-26
AI Technical Summary
When testing small round bar tensile specimens, the existing universal tensile testing machine cannot effectively clamp the specimens, causing them to slip and preventing normal tensile testing.
A fixture for a small round bar tensile test specimen was designed, including a clamping mechanism and a fastening unit. The specimen is clamped by the accommodating space of the clamping module and the arc-shaped protrusion structure, and is fixed by locking screws and torsion bars to ensure that the specimen does not slip during the tensile process.
It effectively prevents small tensile specimens from slipping during the tensile process, ensuring the accuracy of test data and overall test efficiency, and reducing the number of repeated tests.
Smart Images
Figure CN224286516U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of experimental tensile fixture technology, specifically to a fixture for a small round bar tensile specimen. Background Technology
[0002] Currently, the main testing equipment used for testing the tensile mechanical properties of specimens is the universal tensile testing machine. It is primarily used for tensile testing of conventional specimens. The specimen is dumbbell-shaped, with an arc-shaped transition section connecting the dumbbell heads on both sides to the long rod in the middle. Existing conventional specimens have a diameter d0 = 10-20 mm and an overall length of 150-250 mm. The clamps of the universal tensile testing machine primarily hold the specimen at the transition section (radius typically 7.5-15 mm), with the side walls of the dumbbell heads serving as auxiliary clamping points. When operating the universal tensile testing machine to directly fix small tensile specimens with a diameter d0 ≤ 5 mm and an overall length ≤ 50 mm for tensile testing, it was found that when the clamps tightened and tensioning began, the specimen slipped, causing the clamped end to detach from the clamps, resulting in tensile test failure. Repeated attempts failed, and the tensile test could not be performed normally. Analysis of the machine's clamps and the structure of the sample revealed that, due to the very small size of the sample itself, the radius of its transition section was only 3 mm. When the sample began to be stretched, this transition section deformed, and the arc-shaped transition section became flat after deformation, causing the clamps to slip and making normal testing impossible.
[0003] Therefore, in order to solve the above problems and overcome the shortcomings of the existing technology, there is an urgent need for a fixture for small round bar tensile specimens that can help to clamp small tensile specimens, prevent slippage, and ensure that the tensile test is carried out normally. Utility Model Content
[0004] The present invention aims to provide a fixture for a small round bar tensile test specimen. This fixture assists in specimen clamping and solves the problem of slippage during existing specimen clamping, which prevents tensile testing.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] A fixture for a small round bar tensile test specimen includes a clamping mechanism. The clamping mechanism includes a clamping module and a fastening unit for axially fixing the specimen. The clamping module includes a fixed plate and a column fixedly connected to the fixed plate. The column has a receiving space for accommodating the head of the specimen. The column has a pick-and-place opening on its side wall for picking up and placing the specimen. The pick-and-place opening communicates with the receiving space. The end of the receiving space away from the fixed plate has an arc-shaped protrusion structure for fitting a limiting transition section. The fastening unit is detachably connected to the centroid of the fixed plate.
[0007] The principles and advantages of this scheme are:
[0008] 1. Easy installation, effectively preventing slippage of small tensile specimens and ensuring smooth tensile testing. When the inventors discovered that the test could not proceed normally, they conducted an in-depth analysis of the structure of the small tensile specimen and the clamps of the universal tensile testing machine. They found that the root cause was the transition section of the small tensile specimen, which was arc-shaped. During the tensile process, due to the deformation of the specimen, the arc-shaped transition section became flat after deformation, causing slippage during clamping. The clamps could not effectively hold the small tensile specimen, causing it to detach and the tensile test to fail. Considering changing the force plane of the clamps, the inventors designed this device, which includes a clamping module that can accommodate the specimen head. The specimen head can be quickly installed in the accommodating space through the loading and unloading port. The arc-shaped protrusion structure fits snugly, ensuring uniform force distribution and guaranteeing the accuracy of the test data. Because the lower surface of the clamping module is flat, this indirectly changes the original force point of the clamps, changing the force point from an arc to a stable plane, effectively preventing slippage of the small tensile specimen and ensuring smooth tensile testing.
[0009] 2. Ensuring the accuracy of test data and improving overall test efficiency. The inventors conducted in-depth analysis on the design of the clamping module's accommodating space and set up a fastening unit to fix the small tensile specimens. During the tensile test, both ends of the specimen can be locked and fixed, ensuring the accuracy of the test data, reducing the number of repeated tests, and improving the overall test efficiency.
[0010] Preferably, as an improvement, the fastening unit includes a first locking screw and a first torsion bar for twisting the first locking screw. The first torsion bar is perpendicular to the first locking screw and fixed to the screw head of the first locking screw. The first locking screw is threaded to the centroid of the fixing plate, and one end of the first locking screw is located within the receiving space.
[0011] The first locking screw allows for quick and easy axial locking of the sample, while the first torsion bar eliminates the need for wrenches and other operating tools. The first torsion bar allows for quick and easy twisting of the first locking screw, greatly improving operational convenience.
[0012] Preferably, as an improvement, it also includes a limiting member for laterally limiting the sample. A groove is provided in the middle section of the outer side of the column. The limiting member includes a ring, a second locking screw and a second torsion bar. The second torsion bar is perpendicular to the second locking screw and fixed to the screw head of the second locking screw. The ring is slidably connected in the groove. The outer side of the ring is flush with the outer side of the column. The second locking screw is threadedly connected to the ring surface of the ring.
[0013] Although the axial locking limit of the first locking rod, coupled with the tension force after the sample begins to be stretched, puts the sample in a relatively balanced state, the possibility of it coming loose still exists due to limitations in the machining accuracy of the clamping module and the operator's installation skill. To ensure proper installation and stability during the test, a groove is provided in the middle of the outer side of the clamping module, allowing the locking ring to slide within this groove. The groove not only facilitates adjustment of the locking ring's position but also forms a smooth clamping surface with the locking ring, making the clamping more stable. The second locking screw can easily and quickly complete the circumferential fixing and limiting of the sample.
[0014] Preferably, as an improvement, the column is a cylinder, the cross-section of the accommodating space is a U-shaped groove, the bottom of the U-shaped groove is an arc structure, and the arc structure is coaxial with the cylinder.
[0015] The cylindrical shape allows for convenient control of the internal space. During machining, the coaxial position of the cylinder facilitates precise positioning. Furthermore, if the cylinder were prism-shaped, adjustments would be needed during clamping to ensure the flat portion is held; a cylindrical design eliminates this need, improving overall installation efficiency. Additionally, when the specimen axis is not aligned with the loading axis of the tensile testing machine, eccentric loading occurs, leading to additional bending stress during tensile testing. Eccentric loading can also cause the specimen to fracture at the clamping end or in the transition zone, resulting in the failure of measurements of plasticity parameters such as elongation and affecting test results. The coaxiality of the cylinder and the internal U-shaped groove ensures the entire specimen is under axial tension during testing, further ensuring the accuracy of experimental data, reducing the number of repeated tests, and improving overall experimental efficiency.
[0016] Preferably, as an improvement, the number of both the first torsion bar and the second torsion bar is at least two.
[0017] In actual operation, it was found that tightening the first and second locking screws with tools was rather troublesome. From the perspective of the convenience of the torsion operation, at least two first torsion bars are provided at equal intervals on the side of the screw head of the first locking screw, and at least two second torsion bars are provided at equal intervals on the side of the screw head of the second locking screw. The tightening operation can be completed quickly and easily through the first and second torsion bars, which is very convenient.
[0018] Preferably, as an improvement, the wall thickness of the U-shaped groove is greater than 10 mm.
[0019] To ensure the overall strength of the device, calculations show that when the thickness of the U-shaped groove wall is greater than 10mm, the clamping module remains intact after the sample is tensilely damaged, effectively guaranteeing the service life of the device. Attached Figure Description
[0020] Figure 1This is a schematic diagram of the overall structure of an embodiment of the present utility model.
[0021] Figure 2 This is a schematic diagram of the overall installation completed according to an embodiment of this utility model.
[0022] Figure 3 for Figure 2 AA sectional view.
[0023] Figure 4 for Figure 2 Side view.
[0024] Figure 5 This is a schematic diagram of the entire embodiment of the present invention in a clamped and stretched state. Detailed Implementation
[0025] The following detailed description illustrates the specific implementation methods:
[0026] The reference numerals in the accompanying drawings include: clamping module 1, locking ring 2, sample 3, clamp 4, first locking screw 101, first torsion bar 102, sample groove 103, second locking screw 201, and second torsion bar 202.
[0027] The basic implementation examples are as follows: Figure 1-5 As shown:
[0028] As attached Figure 1 As shown, a small tensile specimen clamping fixture includes a pair of clamping mechanisms and lateral limiting members. The clamping mechanisms include two clamping modules 1 and two fastening units for axially fixing the specimen, as shown in the attached figure. Figure 2 As shown, clamping modules 1 are respectively installed to clamp both ends of the sample 3, and the fastening unit is threadedly connected to the axis of the clamping module. Since the two clamping mechanisms have the same structure, the left side is used as an example for explanation. Clamping module 1 is a cylinder, as shown in the attached figure. Figure 3 and attached Figure 4As shown, a coaxial receiving space for accommodating the head of the sample is provided inside the cylinder. This receiving space is the sample groove 103. The cross-section of the sample groove 103 is a U-shaped groove with a wall thickness greater than 10 mm. The bottom of the U-shaped groove is an arc structure, which is coaxial with the cylinder. The coaxiality of the cylinder and the arc structure of the U-shaped groove ensures that the entire sample 3 is in an axially stretched state during tension, further ensuring the accuracy of experimental data, reducing the number of repeated tests, and improving the overall experimental efficiency. Through calculation, when the wall thickness of the U-shaped groove is greater than 10 mm, the clamping module remains intact after the sample is tensilely damaged, effectively ensuring the service life of the device. A pick-and-place port for picking up and placing the sample 3 is provided on the side wall of the cylinder, which is connected to the sample groove 103. The right end of the sample groove 103 has an arc-shaped protrusion for fitting the transition section. The clamping module 1 is mainly used for axial clamping and limiting of the sample 3. The pick-up and drop-out port of the clamping module 1 can quickly and conveniently put the sample 3 into the sample groove 103. The sample groove 103 can effectively fit the head of the sample 3, so that the force is evenly distributed.
[0029] The fastening unit includes a first locking screw 101 and three first torsion bars 102. These three torsion bars 102 are perpendicular to the first locking screw 101 and are evenly spaced and fixed to the screw head of the first locking screw 101. The first locking screw 101 is threaded onto the axis of the clamping module, and its right end is located in the sample groove 103. The first torsion bars 102 eliminate the need for wrenches or other tools, facilitating quick and easy axial fixation of the sample 3 by engaging the first locking screw 101, thus improving overall installation convenience.
[0030] A groove is formed on the outer wall of clamping module 1, as shown in the attached figure. Figure 1 As shown, the locking ring 2 includes a ring body, a second locking screw 201, and a second torsion bar 202. The ring body of the locking ring 2 is coaxially sleeved in the groove of the clamping module 1. The outer diameter of the ring body is equal to the outer diameter of the non-grooved part of the clamping module 1. The groove allows for easy adjustment of the position of the locking ring 2. The outer diameter of the ring body is equal to the outer diameter of the non-grooved part of the clamping module 1, so that the two are on the same plane, forming a flat clamping surface. A threaded through hole that mates with the second locking screw 201 is provided on the side ring surface of the ring body. This threaded through hole is located above the sample groove 103, and the second locking screw 201 is connected to the ring body through this threaded through hole. There are three second torsion bars 202, which are fixed at equal intervals on the side wall of the screw head of the second locking screw 201.
[0031] This solution analyzes the overall structure of specimen 3 and the clamp 4 of the universal tensile testing machine. The root cause is that specimen 3 itself is small in size, and the arc-shaped structure of the transition section of specimen 3 deforms into a planar structure, which leads to clamping instability and slippage. To solve this problem, this solution is designed as a small tensile specimen 3 clamping fixture. A pair of clamping modules 1 and a pair of locking rings 2 are used to limit the specimen 3. During the tensile test, it is only necessary to restrict the translational degrees of freedom of specimen 3 in the x, y, and z directions, as well as the rotational degrees of freedom in the x and y directions (the rotational degree of freedom in the z direction has no effect on the tensile test results, and since specimen 3 will form a self-locking mechanism with clamping module 1 when it is in the tensile state, the rotational degree of freedom in the z direction is not considered). Clamping module 1 restricts the translational and rotational degrees of freedom in the x direction, the first locking screw 101 restricts the translational degree of freedom in the z direction, and the locking ring 2 restricts the translational and rotational degrees of freedom in the y direction. Once the first locking screw 101 and the second locking screw 201 have rotated into position, the sample 3 is effectively limited, and the entire sample 3 is in the axial position, ensuring the accuracy of the test.
[0032] The specific implementation method is as follows:
[0033] Slide the locking ring 2 to the leftmost and rightmost ends, then align the sample 3 with the pick-up and drop-off port of the clamping module 1, and then place it into the sample slot 103 through the sampling port. The two ends of the sample 3 should fit snugly in the sample slot 103. Adjust the sample 3 so that the arc-shaped transition section of the sample 3 fits snugly with the arc-shaped protrusion at the bottom of the sample slot 103. Then tighten the first locking screw 101. Next, slide the locking ring 2 to the middle of the head of the sample 3 and tighten the second locking screw 201. The structure after installation is shown in the attached figure. Figure 2 As shown, the two clamps 4 of the universal tensile testing machine are then clamped onto the two clamping modules 1 respectively, as shown in the attached diagram. Figure 5 As shown, after the overall installation is completed, a tensile test is performed. The lower part of the clamp 4 is clamped on the side of the two clamp modules 1 and the opposite side of the two clamp modules 1. The clamps on both sides of the clamp 4 serve as a fixed support. The side of the clamp 4 that is clamped on the opposite side of the two clamp modules 1 is the main tensile stress point. At this time, the stress point is a flat plane with a stable stress point, which effectively solves the problem that the original arc structure of the transition section could not provide effective support and slipped. The tensile test of small specimens can be carried out smoothly and normally. Moreover, due to the high overall stability and the fact that the axis is always vertical, the overall test results are more accurate.
[0034] The above descriptions are merely embodiments of this utility model. Commonly known technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solution of this utility model. These modifications and improvements should also be considered within the scope of protection of this utility model, and will not affect the effectiveness of the implementation of this utility model or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.
Claims
1. A fixture for a small round bar tensile test specimen, characterized in that: The device includes a clamping mechanism, which comprises a clamping module and a fastening unit for axially fixing the sample. The clamping module includes a fixed plate and a column fixedly connected to the fixed plate. The column has a receiving space for accommodating the head of the sample, and a receiving port for taking out and placing the sample is provided on the side wall of the column. The receiving port is connected to the receiving space. The end of the receiving space away from the fixed plate has an arc-shaped protrusion structure for fitting the transition section. The fastening unit is detachably connected to the centroid of the fixed plate.
2. The fixture for a small round bar tensile specimen according to claim 1, characterized in that: The fastening unit includes a first locking screw and a first torsion bar for twisting the first locking screw. The first torsion bar is perpendicular to the first locking screw and fixed to the screw head of the first locking screw. The first locking screw is threaded to the centroid of the fixing plate, and one end of the first locking screw is located within the receiving space.
3. The fixture for a small round bar tensile specimen according to claim 2, characterized in that: It also includes a limiting component for lateral positioning of the sample. The middle section of the outer side of the column is provided with a groove. The limiting component includes a ring, a second locking screw and a second torsion bar. The second torsion bar is perpendicular to the second locking screw and fixed to the screw head of the second locking screw. The ring is slidably connected in the groove. The outer side of the ring is flush with the outer side of the column. The second locking screw is threadedly connected to the ring surface of the ring.
4. The fixture for a small round bar tensile specimen according to claim 3, characterized in that: The column is a cylinder, and the cross-section of the space is a U-shaped groove. The bottom of the U-shaped groove is an arc structure, and the arc structure is coaxial with the cylinder.
5. The fixture for a small round bar tensile specimen according to claim 4, characterized in that: The number of the first torsion bar and the second torsion bar is at least two.
6. The fixture for a small round bar tensile specimen according to claim 5, characterized in that: The thickness of the wall of the U-shaped groove is greater than 10 mm.