A pin-connected tensile test fixture suitable for dog-bone shaped test specimens

Abstract

The utility model discloses a kind of dog bone shape sample's bolted tensile test fixture suitable for, belong to material mechanics performance test equipment field.The fixture includes connecting rod, left clamping piece, right clamping piece, steel sheet and mounting bolt, and it is the way of the steel sheet one end and left clamping piece connection, the other end and right clamping piece connection compacts sample.The utility model is even dispersed in sample surface by clamping force, solved the problem that existing fixture is due to stress concentration and leads to sample clamping end early fracture, significantly improved the reliability of test data and test success rate, and with the advantages of simple structure, clamping force controllable, wide application range.

Description

Technical Field

[0001] This utility model relates to the technical field of material mechanical property testing equipment, and in particular to a bolted tensile test fixture suitable for dog bone shaped specimens. Background Technology

[0002] In the field of materials science and engineering, tensile testing is one of the most fundamental and important methods for evaluating the mechanical properties of materials. To ensure the accuracy of test results, specimens are usually machined into a "dog-bone" shape, wider at both ends and narrower in the middle, to guide fracture to occur within the effective measuring distance in the middle. Tensile testing requires a universal testing machine, and the two ends of the dog-bone shaped specimen are fixed to the machine using specialized testing fixtures.

[0003] Currently, common tensile testing fixtures, such as hydraulic clamps or wedge clamps, primarily operate by applying a strong clamping force directly to the surface of the specimen's clamping end, relying on friction to fix the specimen and transfer the tensile load. However, when testing certain composite materials, engineering plastics, or brittle metals, this highly concentrated clamping force can create severe stress concentration at the edges of the specimen's clamping area. This stress concentration can easily cause the specimen to fail prematurely at or near the stress-concentrated clamping end, rather than in the designed effective middle section, during tensile loading. This abnormal fracture mode leads to lower measured mechanical properties such as tensile strength, rendering the test results invalid. This not only wastes valuable specimens and testing time but also seriously affects the accuracy and reliability of material performance evaluation.

[0004] Therefore, this utility model proposes a bolted tensile test fixture suitable for dog bone-shaped specimens to overcome the shortcomings of the prior art. Utility Model Content

[0005] In view of the problem that the clamping force of the existing tensile test fixture is too concentrated when clamping dog bone-shaped specimens, which causes stress concentration at the clamping end of the specimen and is prone to abnormal fracture of the specimen, thus affecting the accuracy of the test results, the present invention aims to provide a bolted tensile test fixture for dog bone-shaped specimens with an improved structure that can effectively solve the above problems.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This utility model provides a bolted tensile test fixture suitable for dog bone shaped specimens, comprising: a connecting rod, a left clamp and a right clamp, a high-strength bolt and a nut; as well as steel plates and mounting bolts.

[0007] The connecting rod, left clamp, and right clamp are fixedly connected by the high-strength bolts and nuts.

[0008] Furthermore, one end of the steel sheet is connected to the left clamping plate via the mounting bolt, and the other end of the steel sheet is connected to the right clamping plate via the mounting bolt.

[0009] Preferably, the connecting rod, the left clamp, and the right clamp are provided with mutually aligned mounting holes, and the high-strength bolt passes through the mounting holes and is locked by the nut.

[0010] Preferably, the mounting bolt passes through the through hole provided on the steel plate and is screwed into the threaded hole provided on the left and right clamping plates.

[0011] Preferably, a clamping space for accommodating the sample is formed between the left clamp and the right clamp, and the steel sheet is disposed within the clamping space.

[0012] Preferably, there are two steel sheets arranged in parallel within the clamping space for contacting the sample surface from opposite sides.

[0013] Preferably, the left clamp and the right clamp together form a clamping body, and the connecting rod is fixed to the clamping body.

[0014] Preferably, the free end of the connecting rod is a rod-shaped structure for inserting into the universal testing machine clamp.

[0015] Preferably, the clamp includes an upper clamp for fixing the upper end of the sample and a lower clamp for fixing the lower end of the sample, and the upper clamp and the lower clamp have the same structure.

[0016] This utility model has the following beneficial effects: 1. This utility model, by setting a steel plate and using mounting bolts to connect one end of the steel plate to the left clamping plate and the other end to the right clamping plate, presses the steel plate tightly onto the surface of the dog-bone shaped specimen. This solves the problem of excessively concentrated clamping force in existing fixtures, which easily leads to premature specimen breakage at the clamping end and affects the accuracy of test data. It achieves the technical effect of evenly distributing the clamping force on the specimen clamping surface, effectively protecting the specimen, ensuring that the test fracture point occurs within the effective segment, and improving the success rate and data reliability of tensile tests.

[0017] 2. This utility model solves the problem of inaccurate force transmission caused by loose connections or structural deformation of the fixture by using high-strength bolts and nuts to fasten the connecting rod, left clamp, and right clamp into a rigid whole. It achieves the technical effect of stable and rigid fixture structure, which can accurately transmit the axial tensile force of the universal testing machine to the sample without loss, and ensures a stable and reliable test loading process.

[0018] 3. This utility model solves the problem of lateral tilting of the dog bone during tensile testing by using steel sheets, high-strength bolts and nuts to fix the dog bone sample in the left and right clamping plates. It achieves the technical effect of simple structure, easy operation and maintenance, controllable clamping force, wide applicability, and can meet the tensile testing needs of samples of different hardness and brittle materials. Attached Figure Description

[0019] Figure 1 This is a front view of a bolted tensile testing fixture for dog bone-shaped specimens proposed in this utility model; Figure 2 This is a three-dimensional structural schematic diagram of a bolted tensile testing fixture suitable for dog bone-shaped specimens proposed in this utility model. Figure 3 This is a side view of a bolted tensile testing fixture for dog bone-shaped specimens proposed in this utility model. Figure 4 This is a three-dimensional schematic diagram of the main components of a bolted tensile test fixture for dog bone-shaped specimens proposed in this utility model.

[0020] Legend: 1. Left clamping plate; 2. Right clamping plate; 3. Connecting rod; 4. High-strength bolt; 5. Nut; 6. Steel plate; 7. Mounting bolt. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions in the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0022] Please refer to Figures 1 to 4 This utility model provides a bolted tensile test fixture suitable for dog bone shaped specimens, which aims to solve the problem that existing fixtures are prone to stress concentration when clamping dog bone shaped specimens, leading to premature failure of the specimen clamping end and affecting the accuracy of tensile test results.

[0023] like Figure 1 , Figure 3 and Figure 4As shown, the bolted tensile testing fixture for dog-bone shaped specimens includes a left clamp 1, a right clamp 2, a connecting rod 3, a high-strength bolt 4, and a nut 5. The left clamp 1 and right clamp 2 together form a clamping body, and the connecting rod 3 is fixedly connected to this clamping body. Specifically, mounting holes are provided at corresponding positions on the connecting rod 3, the left clamp 1, and the right clamp 2. The high-strength bolt 4 passes through these aligned mounting holes in sequence, and its end is screwed and locked to the nut 5, thereby integrating the connecting rod 3, the left clamp 1, and the right clamp 2 into a rigid whole. The free end of the connecting rod 3 is a rod-shaped structure. The fixture includes an upper clamp and a lower clamp with identical structures.

[0024] Reference Figures 1 to 4 The bolted tensile test fixture for dog bone-shaped specimens also includes a steel plate 6 and mounting bolts 7. The left clamp 1 and the right clamp 2 are arranged opposite each other, forming a clamping space between them, in which the steel plate 6 and the dog bone-shaped specimen are accommodated.

[0025] Specifically, the steel sheet 6 has a plate-like structure with through holes for the mounting bolts 7 to pass through. In this embodiment, there are two steel sheets 6, which are arranged parallel to each other in the clamping space for contact with the surface of the dog-bone shaped sample from opposite sides. Both the left clamping plate 1 and the right clamping plate 2 have threaded holes for mating with the mounting bolts 7.

[0026] Mounting bolt 7 is an externally threaded fastener used to connect steel plate 6 to left clamp 1 and right clamp 2. During assembly, one end of one steel plate 6 is fixedly connected to left clamp 1 via a mounting bolt 7, which passes through a through hole in steel plate 6 and screws into the threaded hole in left clamp 1. The other end of the steel plate 6 is fixedly connected to right clamp 2 via another mounting bolt 7, which also passes through a through hole in steel plate 6 and screws into the threaded hole in right clamp 2. Another steel plate 6 is connected to left clamp 1 and right clamp 2 in the same manner. By tightening all mounting bolts 7, the two steel plates 6 fix and limit the dog-bone shaped sample, thus securing it firmly between left clamp 1 and right clamp 2.

[0027] In a preferred embodiment of this utility model, to ensure the overall rigidity and connection reliability of the clamp, the left clamping plate 1 and the right clamping plate 2 together constitute a clamping body, and the connecting rod 3 is fixedly connected to the clamping body by a high-strength bolt 4 and a nut 5. Specifically, the connecting rod 3, the left clamping plate 1, and the right clamping plate 2 are all provided with mutually aligned mounting holes. After the high-strength bolt 4 passes through these mounting holes, it is locked from the other end by the nut 5. This connection method forms a gapless rigid structure to ensure the effective transmission of the test tensile force from the connecting rod 3 to the clamping body.

[0028] In another preferred embodiment, to ensure reliable fixation of the sample, the mounting bolt 7 passes through a through hole in the steel plate 6 and is screwed into threaded holes in the left clamp 1 and right clamp 2. This threaded connection method is not only simple in structure, but also allows control of the pressure applied to the steel plate 6 by adjusting the tightening of the mounting bolt 7, thereby ensuring stable positioning of the steel plate 6 on the dog bone sample and preventing it from tilting during testing.

[0029] In another preferred embodiment, two steel plates 6 are disposed within the clamping space formed between the left clamping plate 1 and the right clamping plate 2. These two steel plates 6 are placed parallel to each other and are used to fit the two opposite surfaces of the dog bone-shaped sample being clamped. This symmetrical arrangement helps to distribute the clamping force evenly on the sample surface and avoids uneven force on one side.

[0030] In specific testing applications, this clamp is usually used in pairs, consisting of an upper clamp and a lower clamp with identical structures, used to fix the two ends of the dog-bone shaped specimen, respectively. The end of the connecting rod 3 furthest from the clamping body is made into a rod-shaped structure, designed for easy gripping and fastening by the upper and lower chucks of the universal testing machine. The universal testing machine and its chucks are well-known conventional equipment in this field, and their specific structure will not be described in detail here.

[0031] Working principle: When the bolted tensile test fixture for the dog bone-shaped specimen is in operation, the fixture is first assembled. The mounting holes of the connecting rod 3, the left clamp 1 and the right clamp 2 are aligned, the high-strength bolt 4 is inserted and the nut 5 is tightened, so that the connecting rod 3, the left clamp 1 and the right clamp 2 form a rigid whole.

[0032] Next, install the fixtures. Insert the connecting rod 3 of the assembled upper fixture into the upper chuck of the universal testing machine, and insert the connecting rod 3 of the lower fixture into the lower chuck of the universal testing machine. Tighten them respectively to fix the fixtures and the testing machine into a unified force-bearing body.

[0033] Next, load the sample. First, connect one end of the steel plate 6 to the left clamp 1 of the upper fixture using the mounting bolt 7. After placing the dog-bone shaped sample in the fixture, connect the other end of the steel plate 6 to the right clamp 2 using the mounting bolt 7. Repeat this step on the lower fixture. Finally, tighten all the mounting bolts 7. The steel plate 6 effectively prevents the dog-bone sample from tilting laterally, thus firmly fixing the sample in both directions within the upper and lower fixtures.

[0034] Before loading, adjust the lifting and lowering of the universal testing machine beam to ensure that the specimen is in a natural hanging state without initial tension.

[0035] After the test begins, the universal testing machine outputs axial tensile force through its upper and lower clamps. This tensile force is sequentially transmitted through the machine clamps, connecting rod 3, the clamping body consisting of left clamp 1 and right clamp 2, and steel plate 6, and finally evenly transferred to the dog-bone shaped specimen, causing the specimen to bear a uniaxial tensile load. Throughout the loading process, the testing machine's data acquisition system synchronously records the load intensity. If it is necessary to determine the elongation of the material, an extensometer can be externally connected to the effective section of the specimen before loading. The extensometer will monitor the length change of the specimen in real time during the tensile process and provide the displacement signal to the data acquisition system, thereby completing the accurate measurement of the mechanical properties of the dog-bone shaped specimen.

Claims

1. A bolted tensile testing fixture suitable for dog bone-shaped specimens, comprising: Connecting rod (3); Left clip (1) and right clip (2); High-strength bolts (4) and nuts (5); The connecting rod (3), the left clamp (1) and the right clamp (2) are fixedly connected by the high-strength bolt (4) and the nut (5); Its characteristic is that it further includes a steel sheet (6) and mounting bolts (7); One end of the steel sheet (6) is connected to the left clamp (1) by the mounting bolt (7), and the other end of the steel sheet (6) is connected to the right clamp (2) by the mounting bolt (7).

2. The bolted tensile testing fixture for dog bone-shaped specimens according to claim 1, characterized in that, The connecting rod (3), the left clamp (1) and the right clamp (2) are provided with mutually aligned mounting holes, and the high-strength bolt (4) passes through the mounting holes and is locked by the nut (5).

3. A bolted tensile testing fixture for dog bone-shaped specimens according to claim 1, characterized in that, The mounting bolt (7) passes through the through hole provided on the steel plate (6) and is screwed into the threaded hole provided on the left clamp (1) and the right clamp (2).

4. A bolted tensile testing fixture for dog bone-shaped specimens according to claim 1, characterized in that, The left clamp (1) and the right clamp (2) form a clamping space for accommodating the sample, and the steel sheet (6) is disposed in the clamping space.

5. A bolted tensile testing fixture for dog bone-shaped specimens according to claim 4, characterized in that, The steel sheet (6) consists of two pieces, which are arranged in parallel within the clamping space for contacting the sample surface from opposite sides.

6. A bolted tensile testing fixture for dog bone-shaped specimens according to claim 1, characterized in that, The left clamp (1) and the right clamp (2) together form a clamping body, and the connecting rod (3) is fixed on the clamping body.

7. A bolted tensile testing fixture for dog bone-shaped specimens according to claim 1, characterized in that, The free end of the connecting rod (3) is a rod-shaped structure for inserting into the universal testing machine clamp.

8. A bolted tensile testing fixture for dog bone-shaped specimens according to claim 1, characterized in that, The fixture includes an upper fixture for fixing the upper end of the sample and a lower fixture for fixing the lower end of the sample, and the upper fixture and the lower fixture have the same structure.

Images