Axial fatigue test fixture for a material mechanics testing machine

Abstract

The utility model relates to a kind of material mechanics testing machine axial fatigue test fixture, belong to material mechanics performance test technical field.The fixture includes upper fixture and lower fixture.The upper fixture includes upper connecting body, first spherical connecting disc, second spherical connecting disc, upper spherical fixing piece and matched bolt nut;Lower fixture includes third spherical connecting disc, fourth spherical connecting disc, lower spherical fixing piece and matched bolt nut.Cross-shaped groove is arranged in the upper connecting body, and first and second spherical connecting disc are realized horizontal free movement.Spherical fixing piece and spherical connecting disc form spherical hinge rotary pair, so that spherical fixing piece can rotate freely.When the fixture works, the following fixture center line is reference, and the horizontal position and angle difference of upper fixture center line can exist, and during fatigue test, it can be automatically adjusted position by the horizontal free movement of connecting disc and the free rotation of spherical fixing piece, so that test sample is always in the state of centering, avoid the test deviation problem caused by transverse force or bending moment.

Description

Technical Field

[0001] This invention relates to the field of material mechanical property testing equipment development, specifically to an axial fatigue testing fixture for a material mechanical testing machine. Background Technology

[0002] Currently, conventional fatigue testing fixtures used in materials mechanics testing machines ensure specimen clamping by hydraulically clamping wedge blocks. However, the alignment of the upper and lower clamps relies primarily on the machining accuracy of the testing machine and lacks automatic alignment functionality. Deviations in alignment can subject the specimen to additional bending moments, which, especially for small specimens, can severely affect the accuracy of test results. In recent years, there has been an increasing demand for small-sized specimens in certain applications, such as high-pressure hydrogen environment compatibility testing.

[0003] In high-pressure or extreme working conditions, small-sized specimens are often used due to internal space limitations or the need for prolonged immersion. Therefore, it is necessary to improve the accuracy of the corresponding axial fatigue testing fixtures to obtain accurate test results. The design of these fixtures needs to consider automatic centering during fatigue testing to prevent deviation from the centerline and resulting in unstable data. Existing literature has proposed some axial fatigue testing fixtures with centering functions, such as those provided in patent documents with publication numbers CN2220067Y and CN103712851B. Both use a double-arc structure to adjust the centering of the specimen. However, because the centers of the two arcs are not concentric, if one arc is used as a reference plane and rotated around its center, the other arc will be restricted by the matching arc structure, causing interference and hindering its rotation, thus failing to achieve centering during the test. Moreover, these two fixture structures cannot achieve centering when there is a horizontal difference between the centerlines of the upper and lower fixtures. Summary of the Invention

[0004] To address the problems existing in the prior art, an axial fatigue testing fixture for a materials mechanics testing machine is proposed.

[0005] To solve the technical problem, the technical solution adopted by the present invention is as follows: an axial fatigue testing fixture for a material mechanics testing machine includes an upper fixture and a lower fixture. The upper fixture includes an upper connecting body, a first spherical connecting plate, a second spherical connecting plate, an upper spherical fixing member, and matching bolts and nuts. A groove is provided inside the upper connecting body. A protrusion on the first spherical connecting plate is inserted into the groove of the upper connecting body. Two hemispherical grooves provided on the first and second spherical connecting plates are opposite each other to form an upper spherical cavity. The upper spherical cavity is used to place the upper spherical fixing member. A spherical hinge rotation pair is formed between the spherical surfaces to achieve free rotation function.

[0006] The lower clamp adopts the same structure as the upper clamp, or the lower clamp includes a third spherical connecting plate, a fourth spherical connecting plate, a lower spherical fixing component, and matching bolts and nuts. The two hemispherical grooves on the third and fourth spherical connecting plates form a lower spherical cavity, which is used to place the lower spherical fixing component. A spherical hinge swivel pair is formed between the spherical surfaces to achieve free rotation.

[0007] The second and third spherical connecting discs are respectively provided with through holes for connecting the sample.

[0008] The two arc surfaces of the upper spherical fastener that contact the upper spherical cavity and the two arc surfaces of the lower spherical fastener that contact the lower spherical cavity are on the same center, but the arc surfaces may not be complete. The cutting ratio of the arc surfaces is in the range of 0~70%, which can be achieved by vertically circumferentially cutting the spherical fastener to reduce the contact area with the spherical connecting plate and thus reduce the friction.

[0009] The upper connector is provided with a cross-shaped groove, and the upper connector and the first spherical connecting plate are in clearance fit, which allows the first spherical connecting plate to move in space. It is connected to the first spherical connecting plate through a structure in which large and small pins pass through each other, so as to realize the horizontal movement of the first spherical connecting plate and the second spherical connecting plate.

[0010] The upper connecting body and the first spherical connecting plate can also be connected by a double-layer structure. The upper connecting body and the middle connecting body are respectively provided with a straight groove. The upper connecting body and the middle connecting body, and the middle connecting body and the first spherical connecting plate are in clearance fit and connected by a pin structure, so as to realize the horizontal movement of the first spherical connecting plate and the second spherical connecting plate, thereby realizing the left-right and forward-backward movement of the entire fixture.

[0011] The fatigue testing fixture is equipped with locking components on the test sample and all bolt components to ensure the continuity of mechanical test results.

[0012] Specifically, the locking component includes a first locking member and a second locking member that are fitted together by inclined surfaces with an angle of 1 to 5 degrees. The first locking member and the second locking member are provided with adjustment holes for adjusting the position of the locking component to eliminate the gap generated between the threaded fit after the testing machine applies tensile force.

[0013] This invention offers the following advantages: When the fixture is in operation, with the lower fixture's centerline as a reference, the upper fixture's centerline may exhibit differences in horizontal position and angle. During fatigue testing, the position can be automatically adjusted through the free horizontal movement of the connecting plate and the free rotation of the spherical fixing component. This ensures that the centerline of the specimen remains vertical under various misalignment conditions, achieving automatic centering and facilitating specimen installation and removal, thus improving the accuracy of test data. During the test, the bolt structure only needs to bear the tensile load. The locking component eliminates the gaps generated between the threaded connections after the testing machine applies tension, effectively preventing loosening of the threaded structure and ensuring a stable and effective test process. This fixture is suitable not only for axial fatigue testing but also for tensile testing. Attached Figure Description

[0014] Figure 1 This is a front view of an axial fatigue testing fixture for a materials mechanics testing machine.

[0015] Figure 2 This is a left view of an axial fatigue testing fixture for a materials mechanics testing machine.

[0016] Figure 3 yes Figure 1 Sectional view of AA.

[0017] Figure 4 This is the front view of the locking component.

[0018] Figure 5 This is the left view of the locking component.

[0019] Figure 6 This is a front view of another type of material mechanics testing machine axial fatigue testing fixture.

[0020] Figure 7 This is a left view of another type of material mechanics testing machine axial fatigue testing fixture.

[0021] In the figure, 1. Upper connecting body, 2. Small pin, 3. First spherical connecting plate, 4. Second spherical connecting plate, 5. Sample, 6. Third spherical connecting plate, 7. Fourth spherical connecting plate, 8. Lower spherical fastener, 9. Bolt, 10. Upper spherical fastener, 11. Large pin, 12. Locking component, 12a. First locking component, 12b. Second locking component, 12c. Small hole, 13. Transverse pin, 14. Intermediate connecting body, 15. Longitudinal pin. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0023] Example 1

[0024] Figure 1 and Figure 2 A structural diagram of an axial fatigue testing fixture for a materials mechanics testing machine is shown. The fixture comprises an upper fixture and a lower fixture. The upper fixture includes an upper connecting body 1, a first spherical connecting plate 3 with hemispherical grooves at its ends, and a second spherical connecting plate 4 connected in sequence. The hemispherical grooves of the first spherical connecting plate 3 and the second spherical connecting plate 4 are connected by bolts, forming an upper spherical cavity for housing an upper spherical fixing member 10. The top of the upper connecting body 1 has bolt holes for connection to the fixed end on the upper side of the testing machine, and the lower part has a cross-shaped groove. A protrusion on the upper part of the first spherical connecting plate 3 is inserted into the cross-shaped groove of the upper connecting body 1. A large pin 11 passes through the cross-shaped groove of the upper connecting body 1 and through the protrusion on the upper part of the first spherical connecting plate 3. The protrusion on the upper part of the first spherical connecting plate 3 has a through hole with the same diameter as the large pin 11, allowing the large pin 11 to pass through. Two small pins 2 pass through through holes of the same diameter as the small pins 2 on the upper connecting body 1 and the large pin 11 in sequence; the upper spherical cavity formed by the first spherical connecting plate 3 and the second spherical connecting plate 4 cooperates with the upper spherical fixing member 10 to form a ball joint rotating pair. The bottom of the second spherical connecting plate 4 has a central through hole communicating with the hemispherical groove for installing the sample 5, which can also reduce the friction between the upper spherical fixing member 10 and the surface of the hemispherical groove; the bottom of the upper spherical fixing member 10 is machined with a threaded hole for installing the sample 5, and is vertically circumferentially cut with a cutting ratio of 10%.

[0025] The lower fixture includes a third spherical connecting plate 6, a fourth spherical connecting plate 7, and a lower spherical fixing member 8. The end of the fourth spherical connecting plate 7 also has bolt holes for connection to the fixed end on the lower side of the testing machine. The hemispherical grooves at the ends of the third and fourth spherical connecting plates 6 and 7 respectively form a lower spherical cavity for housing the lower spherical fixing member 8. The lower spherical cavity and the outer surface of the lower spherical fixing member 8 cooperate to form a spherical hinge rotation pair. The top of the third spherical connecting plate 6 has a central through hole communicating with the hemispherical groove for mounting the specimen 5, which also reduces the friction between the lower spherical fixing member 8 and the surface of the hemispherical groove. The top of the lower spherical fixing member 8 is machined with threaded holes for mounting the specimen 5, and undergoes circumferential cutting in the vertical direction at a cutting ratio of 10%. All bolts on this axial fatigue testing fixture are equipped with locking components or other structural parts with the same effect.

[0026] Specific operating steps for using this invention:

[0027] ① Connect the fourth spherical connecting plate 7 to the lower end of the testing machine using bolts. Install the locking component 12 at the lower end of the specimen 5, and pass the lower end of the specimen 5 through the central through hole of the third spherical connecting plate 6 to fully connect it with the lower spherical fixing member 8, thus completing the installation of the lower end of the specimen 5. Connect and fix the third spherical connecting plate 6 and the fourth spherical connecting plate 7 using bolts 9, so that the spherical outer surface of the lower spherical fixing member 8 and the spherical inner cavity formed by the third spherical connecting plate 6 and the fourth spherical connecting plate 7 cooperate to form a spherical hinge rotation pair, thus completing the installation of the lower clamp.

[0028] ② Using a similar method, a locking component 12 is installed on the upper end of the sample 5. The upper end of the sample 5 is then passed through the central through hole of the second spherical connecting plate 4 and fully connected to the upper spherical fixing member 10, thus completing the installation of the upper end of the sample 5. The second spherical connecting plate 4 and the first spherical connecting plate 3 are connected and fixed by bolts 9, so that the spherical outer surface of the upper spherical fixing member 10 and the spherical inner cavity formed by the second spherical connecting plate 4 and the first spherical connecting plate 3 cooperate to form a spherical hinge rotation pair.

[0029] ③ The upper connecting body 1 is connected to the upper end of the testing machine by bolts. By adjusting the position of the lower end of the testing machine, the large pin 11 is inserted into the groove of the upper connecting body 1 and the through hole on the first spherical connecting plate 3. The small pin 2 passes through the upper connecting body 1 and the through hole of the large pin 11 to connect the upper connecting body 1 and the first spherical connecting plate 3. The first spherical connecting plate 3 can move freely in the horizontal direction along the pin.

[0030] ④ Move the lower end of the testing machine downwards to apply a preload to the specimen 5. Under the action of tension, a gap will be generated between the threaded fit, causing the specimen 5 to move relative to the upper spherical fixing member 10. This creates a gap between the locking component 12 and the upper spherical fixing member 10. By tapping the small hole 12c of the locking component 12, it is displaced and the gap is filled. Similarly, by tapping the small hole 12c of the locking component 12 at the lower end of the specimen 5, the gap between the locking component 12 and the lower spherical fixing member 8 is filled. Similarly, the other bolt components of the fixture also achieve the locking function in this way. At this point, the initial installation of the specimen 5 and the entire fixture is completed.

[0031] During the fatigue test, the compressive load borne by the specimen 5 when compressed is transmitted to the upper connecting body 1 or the fourth spherical connecting plate 7 through the contact surfaces of the upper spherical fixing member 10 and the first spherical connecting plate 3, the first spherical connecting plate 3 and the large pin 11, the large pin 11 and the small pin 2, and the small pin 2 and the upper connecting body 1, or through the contact surface of the lower spherical fixing member 8 and the fourth spherical connecting plate 7. The bolts on the fixture do not need to bear the compressive load, thus avoiding loosening of the threads during the fatigue test and ensuring the continuity and accuracy of the fatigue test data. Since the spherical hinge has an automatic angle adjustment function, and the pins ensure that the fixture can be adjusted horizontally, the centerline of the specimen 5 remains vertical throughout the fatigue test. This effectively solves the misalignment problem caused by the difference in horizontal position and angle between the centerlines of the upper and lower fixtures, ensuring the reliability of the test data.

[0032] After the initial installation of the fixture, the upper connecting body 1, the fourth spherical connecting plate 7, and the large pin 11 do not need to be disassembled. When installing a new sample, simply remove the small pin 2 of the upper fixture to separate the upper connecting body 1 from the first spherical connecting plate 3. Lower the lower end of the testing machine to move the lower fixture away from the upper connecting body 1 to provide sufficient space for installing the sample 5. Remove the bolts 9 to separate the first spherical connecting plate 3 from the second spherical connecting plate 4 and the fourth spherical connecting plate 7 from the third spherical connecting plate 6. Pass both ends of the sample 5, with the locking component 12 installed, through the central through holes of the third spherical connecting plate 6 and the second spherical connecting plate 4, and tighten them with the lower spherical fixing component 8 and the upper spherical fixing component 10. Then, tighten the bolts 9 to fix the fourth spherical connecting plate 7 and the third spherical connecting plate 6, and the second spherical connecting plate 4 and the first spherical connecting plate 3 in sequence. At this point, raise and adjust the lower end of the testing machine to position the upper connecting body 1 and the first spherical connecting plate 3 in a suitable position and install the small pin 2 to complete the installation and replacement of the sample 5. The process is simple and convenient.

[0033] Example 2

[0034] Figure 6 and Figure 7A structural diagram of another axial fatigue testing fixture for a materials mechanics testing machine is shown. The axial fatigue testing fixture includes an upper fixture and a lower fixture. The upper fixture comprises an upper connecting body 1, an intermediate connecting body 14, a first spherical connecting plate 3 with hemispherical grooves at its ends, and a second spherical connecting plate 4 connected in sequence. The hemispherical grooves of the first spherical connecting plate 3 and the second spherical connecting plate 4 are connected by bolts to form an upper spherical cavity for placing an upper spherical fixing member 10. The top of the upper connecting body 1 has bolt holes for connecting to the fixed end on the upper side of the testing machine, and the lower part has a straight groove. The protrusion on the upper part of the intermediate connecting body 14 is inserted into the straight groove of the upper connecting body 1. A longitudinal pin 15 passes through through holes of the same diameter as the longitudinal pin 15 on the upper connecting body 1 and the intermediate connecting body 14 in sequence. A slotted groove is formed at the lower part of the intermediate connector 14. The protrusion on the upper part of the first spherical connecting plate 3 is inserted into the slotted groove of the intermediate connector 14. The transverse pin 13 passes through the intermediate connector 14 and the through holes on the first spherical connecting plate 3 with the same diameter as the transverse pin 13. The upper spherical cavity formed by the first spherical connecting plate 3 and the second spherical connecting plate 4 cooperates with the upper spherical fixing member 10 to form a ball joint. The bottom of the second spherical connecting plate 4 has a central through hole communicating with the hemispherical groove for installing the sample 5, which also reduces the friction between the upper spherical fixing member 10 and the surface of the hemispherical groove. The bottom of the upper spherical fixing member 10 is machined with a threaded hole for installing the sample 5, and is vertically circumferentially cut at a ratio of 10%.

[0035] The lower fixture includes a third spherical connecting plate 6, a fourth spherical connecting plate 7, and a lower spherical fixing member 8. The end of the fourth spherical connecting plate 7 also has bolt holes for connection to the fixed end on the lower side of the testing machine. The hemispherical grooves at the ends of the third and fourth spherical connecting plates 6 and 7 respectively form a lower spherical cavity for housing the lower spherical fixing member 8. The lower spherical cavity and the outer surface of the lower spherical fixing member 8 cooperate to form a spherical hinge rotation pair. The top of the third spherical connecting plate 6 has a central through hole communicating with the hemispherical groove for mounting the specimen 5, which also reduces the friction between the lower spherical fixing member 8 and the surface of the hemispherical groove. The top of the lower spherical fixing member 8 is machined with threaded holes for mounting the specimen 5, and undergoes circumferential cutting in the vertical direction at a cutting ratio of 10%. All bolts on this axial fatigue testing fixture are equipped with locking components or other structural parts with the same effect.

[0036] Specific operating steps for using this invention:

[0037] ① Connect the fourth spherical connecting plate 7 to the lower end of the testing machine using bolts. Install the locking component 12 at the lower end of the specimen 5, and pass the lower end of the specimen 5 through the central through hole of the third spherical connecting plate 6 to fully connect it with the lower spherical fixing member 8, thus completing the installation of the lower end of the specimen 5. Connect and fix the third spherical connecting plate 6 and the fourth spherical connecting plate 7 using bolts 9, so that the spherical outer surface of the lower spherical fixing member 8 and the spherical inner cavity formed by the third spherical connecting plate 6 and the fourth spherical connecting plate 7 cooperate to form a spherical hinge rotation pair, thus completing the installation of the lower clamp.

[0038] ② Using a similar method, a locking component 12 is installed on the upper end of the sample 5. The upper end of the sample 5 is then passed through the central through hole of the second spherical connecting plate 4 and fully connected to the upper spherical fixing member 10, thus completing the installation of the upper end of the sample 5. The second spherical connecting plate 4 and the first spherical connecting plate 3 are connected and fixed by bolts 9, so that the spherical outer surface of the upper spherical fixing member 10 and the spherical inner cavity formed by the second spherical connecting plate 4 and the first spherical connecting plate 3 cooperate to form a spherical hinge rotation pair.

[0039] ③ The upper connecting body 1 is connected to the upper end of the testing machine by bolts. The longitudinal pin 15 passes through the through holes of the upper connecting body 1 and the intermediate connecting body 14 to connect the upper connecting body 1 and the intermediate connecting body 14. By adjusting the position of the lower end of the testing machine, the transverse pin 13 is inserted into the through holes of the intermediate connecting body 14 and the first spherical connecting plate 3 to connect the intermediate connecting body 14 and the first spherical connecting plate 3. The first spherical connecting plate 3 can move freely in the horizontal direction along the pin.

[0040] ④ Move the lower end of the testing machine downwards to apply a preload to the specimen 5. Under the action of tension, a gap will be generated between the threaded fit, causing the specimen 5 to move relative to the upper spherical fixing member 10. This creates a gap between the locking component 12 and the upper spherical fixing member 10. By tapping the small hole 12c of the locking component 12, it is displaced and the gap is filled. Similarly, by tapping the small hole 12c of the locking component 12 at the lower end of the specimen 5, the gap between the locking component 12 and the lower spherical fixing member 8 is filled. Similarly, the other bolt components of the fixture also achieve the locking function in this way. At this point, the initial installation of the specimen 5 and the entire fixture is completed.

[0041] During the fatigue test, the compressive load borne by the specimen 5 when compressed is transmitted to the upper connecting body 1 or the fourth spherical connecting plate 7 through the contact surfaces of the upper spherical fixing member 10 and the first spherical connecting plate 3, the first spherical connecting plate 3 and the transverse pin 13, the transverse pin 13 and the intermediate connecting body 14, the intermediate connecting body 14 and the longitudinal pin 15, and the longitudinal pin 15 and the upper connecting body 1, or through the contact surface of the lower spherical fixing member 8 and the fourth spherical connecting plate 7. The bolts on the fixture do not need to bear the compressive load, thus avoiding loosening of the threads during the fatigue test and ensuring the continuity and accuracy of the fatigue test data. Since the spherical hinge has an automatic angle adjustment function, and the pins ensure that the fixture can be adjusted horizontally, the centerline of the specimen 5 remains vertical throughout the fatigue test. This effectively solves the misalignment problem caused by the difference in horizontal position and angle between the centerlines of the upper and lower fixtures, ensuring the reliability of the test data.

[0042] After the initial installation of the fixture, the upper connecting body 1, the intermediate connecting body 14, the fourth spherical connecting plate 7, and the longitudinal pin 15 do not need to be disassembled. When installing a new sample, simply remove the transverse pin 13 of the upper fixture to separate the intermediate connecting body 14 from the first spherical connecting plate 3. Lower the lower end of the testing machine to move the lower fixture away from the intermediate connecting body 14 to provide sufficient space for installing the sample 5. Remove the bolts 9 to separate the first spherical connecting plate 3 from the second spherical connecting plate 4 and the fourth spherical connecting plate 7 from the third spherical connecting plate 6. Then, tighten the installation. The two ends of the sample 5 of component 12 pass through the central through holes of the third spherical connecting plate 6 and the second spherical connecting plate 4, respectively, and are tightened to the lower spherical fixing member 8 and the upper spherical fixing member 10. Then, by tightening the bolts 9, the fourth spherical connecting plate 7 and the third spherical connecting plate 6 are fixed in sequence, and the second spherical connecting plate 4 and the first spherical connecting plate 3 are fixed. At this time, by raising and adjusting the lower end of the testing machine to make the intermediate connecting body 14 and the first spherical connecting plate 3 in a suitable position, the transverse column pin 13 is installed, thus completing the installation and replacement of the sample 5. The process is simple and convenient.

[0043] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. For example, the present invention is not limited to any particular application and is applicable to various environmental conditions such as different media, pressures, and temperatures. Furthermore, the present invention is not limited to the shape of the spherical connecting disc; it can be a cuboid, a cylinder, or other structures, and the corresponding shapes of the upper connecting body and the pin are also not limited.

[0044] Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention shall be included within the scope of protection of this invention.

Claims

1. A material mechanics testing machine axial fatigue testing fixture, comprising an upper fixture and a lower fixture, the upper fixture including an upper connecting body, a first spherical connecting plate, a second spherical connecting plate, and an upper spherical fixing member, characterized in that, The upper connector is provided with a groove for connecting with the first spherical connecting plate; the two hemispherical grooves provided on the first spherical connecting plate and the second spherical connecting plate are opposite each other to form an upper spherical cavity, which is used to place the upper spherical fixing component; The lower clamp adopts the same structure as the upper clamp, or the lower clamp includes a third spherical connecting plate, a fourth spherical connecting plate, and a lower spherical fixing member. The two hemispherical grooves on the third and fourth spherical connecting plates form a lower spherical cavity, which is used to place the lower spherical fixing member. The second and third spherical connecting disks are respectively provided with through holes for connecting the sample; The upper connecting body is provided with a cross-shaped groove. The upper connecting body and the first spherical connecting plate are connected by a clearance fit and a structure in which large and small pins pass through each other, so as to realize the horizontal movement of the first spherical connecting plate and the second spherical connecting plate. The upper connecting body and the first spherical connecting plate can also be connected by a double-layer structure. The upper connecting body and the middle connecting body are respectively provided with a straight groove. The upper connecting body and the middle connecting body, and the middle connecting body and the first spherical connecting plate are in clearance fit and connected by a pin structure to realize the horizontal movement of the first spherical connecting plate and the second spherical connecting plate.

2. The axial fatigue testing fixture for a materials mechanics testing machine according to claim 1, characterized in that: The two arc surfaces of the upper spherical fastener that contact the upper spherical cavity and the two arc surfaces of the lower spherical fastener that contact the lower spherical cavity are on the same center, but the arc surfaces may not be complete, and the cutting ratio of the arc surfaces is in the range of 0~70%.

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