Auxiliary clamping device for plate-shaped test specimen

Abstract

The application provides an auxiliary clamping device for a plate-shaped sample for a fatigue testing machine, which comprises a positioning support, a clamping structure of which one end is hinged to the positioning support and the other end can slide along the length direction of the positioning support; the clamping structure comprises two symmetrical clamping rods arranged on the two sides of the positioning support, and the two clamping rods are connected through an elastic tightening member; the clamping structure has at least two groups and is arranged in the height direction of the positioning support, and the centering and clamping of the sample are realized through the cooperation of the at least two groups of clamping rods. The device provided by the application is specially used for the rapid and accurate centering of small plate-shaped samples, has a simple overall structure and is convenient to clamp, and can effectively solve the problems of sample eccentricity, uneven stress, low clamping efficiency and easy damage to the sample in the traditional clamping mode.

Description

Technical Field

[0001] This invention relates to the field of material mechanical property testing technology, and more specifically, to an auxiliary clamping device for plate-shaped specimens. Background Technology

[0002] In the field of shipbuilding and marine engineering, there are many thin-walled structures with a thickness of less than 5 mm, such as aluminum superstructure panels and pipeline system substrate layers. The failure mode of such structures is mostly fatigue failure. In axial loading fatigue tests, the specimens need to be precisely installed between the clamping blocks of the testing machine to ensure that the central axis of the specimen coincides with the loading axis of the testing machine, that is, to achieve "centering" of the specimen clamping. Otherwise, additional bending stress will be introduced, leading to distortion of test data.

[0003] Currently, rod-shaped specimens can be automatically aligned using a "V"-shaped clamping groove. However, for small, lightweight, thin-walled plate-shaped specimens, operators still need to manually align them by visual inspection and touch, which presents several challenges: First, horizontal centering is difficult due to limited operating space, making it hard to quickly and accurately place the specimen in the center position; second, axial alignment is difficult, as the specimen's central axis is prone to offset, leading to initial bending; and third, the operation is inefficient and reliant on personal experience, with a time-consuming and labor-intensive installation process and poor repeatability. Patent application number 202520182712.3 discloses a buckling-resistant fixture for thin-plate metallic structures used in low-cycle fatigue testing. This fixture achieves rapid specimen assembly through a fixing component, reducing lateral buckling instability between the clamping part of the equipment and the fixture; its guiding component can prevent lateral buckling instability in the thickness direction when the specimen is subjected to tensile and compressive cyclic loads, thereby enhancing specimen stability. However, it still cannot achieve rapid alignment of plate-shaped specimens.

[0004] Therefore, there is an urgent need for an auxiliary clamping device that can achieve rapid and accurate centering, can be repeatedly installed, and is easy to operate for small plate-shaped specimens. Summary of the Invention

[0005] In view of this, the present invention aims to provide an auxiliary clamping device for plate-shaped specimens to solve the problem that the prior art cannot achieve rapid centering of small plate-shaped specimens.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] This invention provides an auxiliary clamping device for plate-shaped specimens used in a fatigue testing machine. The auxiliary clamping device for plate-shaped specimens includes a positioning bracket, which is provided with a clamping structure. One end of the clamping structure is hinged to the positioning bracket, and the other end of the clamping structure can slide along the length direction of the positioning bracket. The clamping structure includes two clamping rods, which are symmetrically arranged on both sides of the positioning bracket and connected by an elastic tightening member. The clamping structure has at least two sets and is arranged at intervals along the height direction of the positioning bracket. The centering and clamping of the specimen is achieved by the cooperation of at least two sets of clamping rods.

[0008] The present invention features a clamping structure that slides with the positioning bracket, along with symmetrically arranged clamping rods and elastic tightening components. This enables automatic centering and stable clamping of plate-shaped specimens, ensuring uniform stress on the specimens during fatigue testing and improving test accuracy and reliability.

[0009] Furthermore, the clamping rod is perpendicular to the positioning bracket and extends in the horizontal direction.

[0010] This setup ensures that the clamping force acts perpendicularly on the sample surface, avoiding lateral force components, reducing sample off-center loading and torsion, and further improving alignment accuracy and test stability.

[0011] Furthermore, the clamping structure also includes a first guide lug and a second guide lug, which are hinged together by the clamping rod. The end of the first guide lug away from the clamping rod is hinged to the positioning bracket, and the end of the second guide lug away from the clamping rod slides along the length direction of the positioning bracket.

[0012] This invention forms a stable linkage guiding mechanism through double guide lugs, ensuring smooth and synchronous opening and closing of the clamping rod, reliable clamping action, and resistance to jamming.

[0013] Furthermore, there are two second guide lugs arranged symmetrically along the length of the positioning bracket. One of the second guide lugs is provided with a guide rod, and the other is provided with a guide cylinder. The guide rod can extend into the guide cylinder to form a guide mating pair. The guide mating pair can slide in a limited manner along the length of the positioning bracket and drive the two clamping rods in the same group to be symmetrically distributed about the central axis of the positioning bracket.

[0014] Furthermore, the positioning bracket includes a base plate and an upright plate. The upright plate is provided with a bracket mounting shaft and a bracket guide groove penetrating its upper and lower surfaces. The end of the first guide lug away from the clamping rod is hinged to the bracket mounting shaft, and the end of the second guide lug away from the clamping rod slides along the bracket guide groove for limitation.

[0015] This structure is simple and has good rigidity between the upright plate, guide groove, and mounting shaft, providing stable support and precise guidance for the clamping structure, facilitating processing and assembly, and improving the overall structural strength.

[0016] Furthermore, the fatigue testing machine is equipped with a testing machine clamping block, the base plate is fixedly connected to the testing machine clamping block and the axis of the base plate coincides with that of the testing machine clamping block, so as to realize the centering and clamping of the sample.

[0017] This invention enables the auxiliary clamping device to be coaxially positioned with the clamping block of the testing machine, ensuring that the sample and the loading center of the testing machine are consistent from the installation reference, thus avoiding eccentricity errors caused by clamping.

[0018] Furthermore, the base plate is machined with fixing holes, and the testing machine clamping block is fixed to the base plate through the fixing holes, so that the central axis of the positioning bracket coincides with the loading axis of the fatigue testing machine.

[0019] Furthermore, the base plate has a widened and reinforced structure in the middle, and the widened and reinforced structure is integrally formed with the base plate.

[0020] The one-piece molding enhances the load-bearing capacity of the middle part of the base plate, improves the overall rigidity and stability of the device, makes it less prone to deformation under repeated fatigue loading, and extends its service life.

[0021] Furthermore, the end of the clamping rod away from the sample is provided with a hanging tail section, and the hanging tail section has a slot. The elastic tightening member is engaged in the slot, and the tensile rebound force of the elastic tightening member provides a continuous opposing clamping force to the clamping rod.

[0022] The slot structure facilitates the installation and positioning of the elastic element, ensures stable and continuous clamping force, prevents the sample from loosening during the test, and improves clamping reliability.

[0023] Furthermore, a section of the clamping rod used to clamp the sample is covered with a flexible friction layer.

[0024] This invention features a flexible friction layer that increases friction between the sample and the sample, while preventing damage to the sample surface during clamping, thus protecting the sample's appearance and precision. It is suitable for thin-walled, brittle, or plate-shaped samples with high surface precision requirements.

[0025] Compared with the prior art, the auxiliary clamping device for plate-shaped samples described in this invention has the following advantages:

[0026] (1) The present invention adopts a symmetrical clamping structure, combined with a forced symmetrical guiding mechanism consisting of guide lugs, guide rods and guide cylinders, which can ensure that the clamping rods on both sides always move synchronously and symmetrically, thereby realizing automatic centering of the sample from the structure, making the center of the sample consistent with the loading axis of the testing machine, fundamentally eliminating eccentric load, and significantly improving the accuracy and repeatability of fatigue test data.

[0027] (2) The present invention can achieve automatic clamping by relying on the elastic tightening component, without complicated adjustment, and has high clamping and disassembly efficiency; the clamping action is stable, and the surface of the clamping rod is provided with a flexible friction layer, which can ensure sufficient clamping friction without damaging the sample surface, and is particularly suitable for thin-walled, brittle and plate-shaped samples with high surface precision requirements. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0029] Figure 1 This is a schematic diagram of the overall structure of the auxiliary clamping device for fatigue testing of plate specimens described in this invention, installed on the testing machine.

[0030] Figure 2 This is a magnified view of part A.

[0031] Figure 3 This is a schematic diagram of the plate-shaped specimen fatigue testing auxiliary clamping device of the present invention clamping the specimen;

[0032] Figure 4 This is an exploded view of the auxiliary clamping device for fatigue testing of plate-shaped specimens according to the present invention;

[0033] Figure 5 This is a schematic diagram of the second guide ear structure of the present invention;

[0034] Figure 6 A schematic diagram of the clamping rod and the first guide lug hinged to the clamping rod;

[0035] Figure 7 This is a schematic diagram of the positioning bracket structure.

[0036] Explanation of reference numerals in the attached figures:

[0037] 1. Positioning bracket; 1-1. Bracket mounting shaft; 1-2. Bracket guide groove; 1-3. Base plate; 1-4. Vertical plate; 1-5. Fixing hole; 2. Clamping rod; 2-1. Hanging tail section; 2-11. Slot; 3. Guide lug; 3-1. First guide lug; 3-2. Second guide lug; 3-21. Guide rod; 3-22. Guide cylinder; 4. Elastic tightening component; 5. Sample; 6. Testing machine clamping block; 7. Testing machine chuck; 8. Auxiliary clamping device for plate-shaped samples; 9. First clamping structure; 10. Second clamping structure. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments. First, it should be noted that the data in the following experimental examples were obtained by the inventors through numerous experiments. Due to space limitations, only a portion of these data is shown in the specification, and those skilled in the art can understand and implement the present invention based on this data. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various modifications or alterations to the invention, and these modifications or alterations also fall within the scope of protection of this application.

[0039] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0040] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0041] like Figures 1-2 As shown, this embodiment provides an auxiliary clamping device for plate-shaped specimens, used in a fatigue testing machine. The auxiliary clamping device 8 for plate-shaped specimens includes a positioning bracket 1. The positioning bracket 1 is provided with a clamping structure. One end of the clamping structure is hinged to the positioning bracket 1, and the other end of the clamping structure can slide along the length direction of the positioning bracket 1. The clamping structure includes clamping rods 2. There are two clamping rods 2 symmetrically arranged on both sides of the positioning bracket 1. The two clamping rods 2 are connected by an elastic tightening member 4. The clamping structure has at least two sets and is arranged at intervals along the height direction of the positioning bracket 1. The centering and clamping of the specimen 5 is achieved by the cooperation of at least two sets of clamping rods 2.

[0042] In a preferred embodiment of this invention, the thickness of the sample 5 is ≤5mm.

[0043] In this embodiment, the clamping rod 2 is perpendicular to the positioning bracket 1 and extends in the horizontal direction.

[0044] like Figure 2 As shown, in a preferred embodiment, the clamping structure consists of two sets, each set being a rhomboid structure that operates synchronously. Each set of clamping structures has clamping rods 2 on both sides of the positioning bracket 1. The sample 5 is positioned centrally by the synchronous clamping and symmetrical limiting of the upper and lower sets of clamping rods 2.

[0045] It should be noted that the lower clamping rod 2 clamps the lower part of the sample 5, and the upper clamping rod 2 clamps the upper part of the sample 5, thereby achieving the centering of the sample.

[0046] It should be explained that in this embodiment, the two clamping structures are rhomboid structures, but the amount of extension and retraction may be different.

[0047] In a preferred embodiment, the clamping structure includes a first clamping structure 9 and a second clamping structure 10. One end of the first clamping structure 9 and the second clamping structure 10 are hinged to the positioning bracket 1, and the other end can slide along the length direction of the positioning bracket 1.

[0048] like Figures 3-6 As shown, in this embodiment, the clamping structure further includes a first guide ear 3-1 and a second guide ear 3-2. The first guide ear 3-1 and the second guide ear 3-2 are hinged together by the clamping rod 2. The end of the first guide ear 3-1 away from the clamping rod 2 is hinged to the positioning bracket 1, and the end of the second guide ear 3-2 away from the clamping rod 2 is limited to slide along the length direction of the positioning bracket 1.

[0049] In this embodiment, there are two second guide lugs 3-2 arranged symmetrically along the length of the positioning bracket 1. One of the second guide lugs 3-2 is provided with a guide rod 3-21, and the other is provided with a guide cylinder 3-22. The guide rod 3-21 can extend into the guide cylinder 3-22 to form a guide mating pair. The guide mating pair can slide in a limited manner along the length of the positioning bracket 1 and drive the two clamping rods 2 in the same group to be symmetrically distributed about the central axis of the positioning bracket 1.

[0050] It should be noted that the first guide ear 3-1 and the second guide ear 3-2 are collectively referred to as guide ear 3, and guide ear 3 is the direct component for realizing the linkage of the clamping structure.

[0051] In a preferred embodiment, the guide rod 3-21 rotates freely within the guide cylinder 3-22, effectively eliminating the jamming force during the movement of the clamping structure.

[0052] In a preferred embodiment, each clamping structure has two first guide lugs 3-1 and two second guide lugs 3-2, which are symmetrically arranged along the length of the positioning bracket 1, and adjacent clamping structures are hinged together by the first guide lugs 3-1 and / or the bracket mounting shaft 1-1.

[0053] In a preferred embodiment, each clamping structure has a through hole on the first guide ear 3-1 and the second guide ear 3-2, and the clamping rod 2 is hinged to the first guide ear 3-1 and the second guide ear 3-2 through the through hole.

[0054] like Figure 7As shown, in this embodiment, the positioning bracket 1 includes a base plate 1-3 and a vertical plate 1-4. The vertical plate 1-4 is provided with a bracket mounting shaft 1-1 and a bracket guide groove 1-2 that penetrates its upper and lower surfaces. The end of the first guide lug 3-1 away from the clamping rod 2 is hinged to the bracket mounting shaft 1-1, and the end of the second guide lug 3-2 away from the clamping rod 2 slides along the bracket guide groove 1-2 for limitation.

[0055] It should be noted that the guide mating pair slides along the bracket guide groove 1-2 of the positioning bracket 1, and the two ends of the bracket guide groove 1-2 are provided with limiting bosses to prevent the guide mating pair from slipping.

[0056] In a preferred embodiment, each clamping structure has through holes on both sides of the first guide lug 3-1, and the bracket mounting shaft 1-1 is hinged to the adjacent clamping structure through the through holes.

[0057] In this embodiment, the fatigue testing machine is provided with a testing machine clamping block 6, the base plate 1-3 is fixedly connected to the testing machine clamping block 6 and the central axis of the base plate 1-3 coincides with that of the testing machine clamping block 6, so as to realize the centering and clamping of the sample 5.

[0058] In a preferred embodiment, the fatigue testing machine further includes a testing machine chuck 7. The testing machine chuck 7 and the testing machine clamping block 6 are an integrated matching structure of the fatigue testing machine. The central axis of the two coincides with the loading axis of the fatigue testing machine. The testing machine chuck 7 is used to directly clamp the end of the specimen 5 after it has been centered by the auxiliary clamping device 8 for plate-shaped specimens, providing a stable clamping base for the specimen 5. At the same time, it serves as the load execution end of the fatigue testing machine, transmitting axial alternating fatigue load to the specimen 5 to ensure that the central axis of the specimen 5 is completely coincident with the loading axis of the fatigue testing machine.

[0059] In this embodiment, the base plate 1-3 is provided with fixing holes 1-5, and the testing machine clamping block 6 is fixed to the base plate 1-3 through the fixing holes 1-5, so that the central axis of the positioning bracket 1 coincides with the loading axis of the fatigue testing machine.

[0060] In a preferred embodiment, the testing machine clamping block 6 is provided with mounting holes, the mounting holes and fixing holes 1-5 have the same diameter and hole spacing, and the testing machine clamping block 6 is fixedly connected to the base plate 1-3 by screws.

[0061] In this embodiment, the middle part of the base plate 1-3 is provided with a widening and reinforcing structure, and the widening and reinforcing structure and the base plate 1-3 are integrally formed.

[0062] In this embodiment, the end of the clamping rod 2 away from the sample 5 is provided with a hanging tail section 2-1, and the hanging tail section 2-1 is provided with a slot 2-11. The elastic tightening member 4 is engaged in the slot 2-11, and the tensile rebound force of the elastic tightening member 4 provides a continuous opposing clamping force to the clamping rod 2.

[0063] It should be noted that the elastic tightening component can be an elastic component with continuous tensile rebound force, such as an elastic band or a spring rope.

[0064] In a preferred embodiment, the elastic tightening member 4 is an elastic rubber band and is snapped into the slot 2-11.

[0065] In this embodiment, a section of the outer surface of the clamping rod 2 used to clamp the sample 5 is covered with a flexible friction layer.

[0066] In a preferred embodiment, the flexible friction layer is made of rubber. The rubber material covers the working section of the clamping rod 2 that holds the sample 5, with a covering thickness of 0.5~2mm, to protect the sample 5 and provide friction to increase clamping force.

[0067] In a preferred embodiment, the hanging tail section 2-1 is provided with a step on the side near the guide ear 3, and the first guide ear 3-1 and the second guide ear 3-2 are fixed to the clamping rod 2 by the step.

[0068] It should be explained that this device first establishes a centering reference by rigidly connecting the positioning bracket to the clamping block of the testing machine, making the central axis of the bracket coincide with the loading axis of the testing machine. Then, by using two sets of upper and lower rhomboid hinged linkage clamping structures, combined with the forced symmetrical constraint of the guide rod-guide cylinder and the opposing pre-tightening force of the elastic tightening component, the upper and lower parts of the specimen are automatically aligned to the reference axis to achieve horizontal centering. The geometric constraint of two-point alignment ensures that the central axis of the specimen is vertically collinear with the loading axis. At the same time, the rubber flexible friction layer of the clamping rod and the adaptive pre-tightening force of the elastic component eliminate additional clamping stress, thereby avoiding additional bending stress caused by eccentric load from the root, achieving precise centering of thin-walled plate specimens and pure axial load transfer in fatigue testing.

[0069] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. An auxiliary clamping device for plate-shaped specimens, used in a fatigue testing machine, characterized in that, The auxiliary clamping device (8) for the plate-shaped sample includes a positioning bracket (1), which is provided with a clamping structure. One end of the clamping structure is hinged to the positioning bracket (1), and the other end of the clamping structure can slide along the length direction of the positioning bracket (1). The clamping structure includes clamping rods (2), and there are two clamping rods (2) symmetrically arranged on both sides of the positioning bracket (1). The two clamping rods (2) are connected by an elastic tightening member (4). The clamping structure has at least two sets and is arranged at intervals along the height direction of the positioning bracket (1). The centering and clamping of the sample (5) is achieved by the cooperation of at least two sets of clamping rods (2).

2. The auxiliary clamping device for plate-shaped specimens according to claim 1, characterized in that, The clamping rod (2) is perpendicular to the positioning bracket (1) and extends in the horizontal direction.

3. The auxiliary clamping device for plate-shaped specimens according to claim 1, characterized in that, The clamping structure further includes a first guide ear (3-1) and a second guide ear (3-2). The first guide ear (3-1) and the second guide ear (3-2) are hinged together by the clamping rod (2). The end of the first guide ear (3-1) away from the clamping rod (2) is hinged to the positioning bracket (1). The end of the second guide ear (3-2) away from the clamping rod (2) is limited to slide along the length direction of the positioning bracket (1).

4. The auxiliary clamping device for plate-shaped specimens according to claim 3, characterized in that, The second guide lug (3-2) consists of two pieces and is symmetrically arranged along the length of the positioning bracket (1). One of the second guide lugs (3-2) is provided with a guide rod (3-21), and the other is provided with a guide cylinder (3-22). The guide rod (3-21) can extend into the guide cylinder (3-22) to form a guide mating pair. The guide mating pair can slide along the length of the positioning bracket (1) and drive the two clamping rods (2) in the same group to be symmetrically distributed about the central axis of the positioning bracket (1).

5. The auxiliary clamping device for plate-shaped specimens according to claim 3, characterized in that, The positioning bracket (1) includes a base plate (1-3) and a vertical plate (1-4). The vertical plate (1-4) is provided with a bracket mounting shaft (1-1) and a bracket guide groove (1-2) that runs through its upper and lower surfaces. The end of the first guide lug (3-1) away from the clamping rod (2) is hinged to the bracket mounting shaft (1-1). The end of the second guide lug (3-2) away from the clamping rod (2) slides along the bracket guide groove (1-2) for a limited position.

6. The auxiliary clamping device for plate-shaped specimens according to claim 5, characterized in that, The fatigue testing machine is equipped with a testing machine clamping block (6). The base plate (1-3) is fixedly connected to the testing machine clamping block (6), and the central axis of the base plate (1-3) coincides with that of the testing machine clamping block (6), so as to realize the centering and clamping of the sample (5).

7. The auxiliary clamping device for plate-shaped specimens according to claim 6, characterized in that, The base plate (1-3) is machined with fixing holes (1-5), and the testing machine clamping block (6) is fixed to the base plate (1-3) through the fixing holes (1-5), so that the central axis of the positioning bracket (1) coincides with the loading axis of the fatigue testing machine.

8. The auxiliary clamping device for plate-shaped specimens according to claim 5, characterized in that, The base plate (1-3) is provided with a widening and reinforcing structure in the middle, and the widening and reinforcing structure and the base plate (1-3) are integrally formed.

9. The auxiliary clamping device for plate-shaped specimens according to claim 1, characterized in that, The clamping rod (2) has a hanging tail section (2-1) at one end away from the sample (5). The hanging tail section (2-1) has a slot (2-11). The elastic tightening member (4) is engaged in the slot (2-11). The elastic tightening member (4) provides a continuous opposing clamping force to the clamping rod (2) through the tensile rebound force of the elastic tightening member (4).

10. The auxiliary clamping device for plate-shaped specimens according to claim 9, characterized in that, The clamping rod (2) is used to clamp the outer surface of a section of the sample (5) and is covered with a flexible friction layer.

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