Pure bending moment testing device and testing method based on double vertical sliding rails

Abstract

The invention relates to a pure bending moment testing device and a pure bending moment testing method based on double vertical sliding rails. According to the invention, a double-vertical sliding track scheme is adopted, and non-bending force is released by driving the sample to bend and allowing the two ends of the sample to freely move, so that a pure bending test with a large rotation angle is carried out, and the accuracy of a test result is ensured. Compared with existing three-point bending and four-point bending testing devices, the device is not only suitable for linear bending moment testing material structures such as sheets, spring steel and rulers which can be subjected to bending tests in a conventional universal material testing machine, but also can be used for carrying out large-angle-range nonlinear pure bending moment tests on different types of materials such as ultrathin flexible structures; the test requirements of various materials and structures on mechanical properties under the condition of large deformation are met, and the universality of bending moment test is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of material and structural mechanics testing, in particular to a pure bending moment testing device and testing method based on double vertical sliding tracks, for studying the relationship between bending moment and rotation angle of materials or structures in pure bending state, especially suitable for pure bending moment mechanical property testing of nonlinear large deformation materials or structures. BACKGROUND

[0002] Bending test is a basic method for material or structure mechanical property test, which is used to determine the mechanical properties of materials under bending load. General bending test is carried out on a universal material testing machine, with three-point and four-point bending two loading modes, and the cross section of the sample is circular or rectangular. The span of the test is generally ten times the diameter, and the bending curve is measured with load as the vertical coordinate and sample deflection as the horizontal coordinate, representing the relationship between load and sample center line deviation from the original position. These methods are widely used to measure the bending stiffness and strength of rigid test samples with small deformation.

[0003] The bending test design of universal material testing machine is generally suitable for materials with relatively large rigidity, and the relationship between bending moment and deformation of such materials is often linear. However, the relationship between bending moment and deformation of ultra-thin flexible materials is often nonlinear. Taking thin shell structure as an example, which is a typical representative of ultra-thin flexible materials, thin shell structure has the characteristics of thin wall and light weight, and its thickness is much smaller than the other two dimensions (such as length and width), usually the ratio of thickness to other dimensions is less than 1 / 10. Under large deformation and stress, thin shell structure shows obvious bending or curved deformation, and mainly bears load through bending, shearing and stretching, unlike conventional beams or columns which mainly rely on axial stress. This kind of structure also involves problems such as stress concentration, buckling and stability. Especially in the case of large deformation or large rotation angle, the loading system and measuring device of the universal material testing machine are difficult to accurately control or read the asymmetric real deformation of the material, which affects the accuracy and repeatability of the test data. At the same time, some ultra-thin flexible samples may not be effectively clamped in the clamp of the universal material testing machine, which leads to uneven loading and affects the bending moment test results.

[0004] In existing universal material testing equipment, the test of such thin-walled structures often has certain limitations and cannot effectively simulate the nonlinear response in the large deformation process. Therefore, it is necessary to design and develop a pure bending moment testing device that meets the requirements. SUMMARY

[0005] In view of the above problems, a pure bending moment testing device and testing method based on double vertical sliding tracks are provided, which aims to study the relationship between bending moment and rotation angle of materials or structures in pure bending state, especially suitable for pure bending moment mechanical property testing of nonlinear large deformation materials or structures.

[0006] The specific technical solutions are as follows: The first aspect of the present application provides a pure bending moment testing device based on double vertical sliding rails, comprising: A first sliding rail, a first clamp is rotatably mounted on the first sliding rail, and the first clamp can reciprocally slide along the first sliding rail; and A second sliding rail, the second sliding rail is perpendicular to the first sliding rail, a second clamp is mounted on the second sliding rail, and the second clamp can reciprocally slide along the second sliding rail.

[0007] Further, the pure bending moment testing device further comprises a first sliding block, the first sliding block is mounted on the first sliding rail, the first sliding block can reciprocally slide along the first sliding rail, and the first clamp is rotatably mounted on the first sliding block.

[0008] Further, the pure bending moment testing device further comprises a driving motor, a base of the driving motor is mounted on the first sliding block, and the first clamp is mounted on a driving shaft of the driving motor.

[0009] Further, the pure bending moment testing device further comprises a second sliding block, the second sliding block is mounted on the second sliding rail, the second sliding block can reciprocally slide along the second sliding rail, and the second clamp is fixedly mounted on the second sliding block.

[0010] Further, the first clamp and the second clamp are the same in structure, and each comprises first clamping plates and second clamping plates which are arranged at intervals, the bottom of the first clamping plate is mounted on the driving shaft of the driving motor or the second sliding block, and the second clamping plate is fixedly mounted on the first clamping plate.

[0011] Further, the second clamping plate is fixedly mounted on the first clamping plate through a fastening bolt.

[0012] Further, a first torque sensor is mounted on the first clamp, and a second torque sensor is mounted on the second clamp.

[0013] Further, the pure bending moment testing device further comprises a testing rack, the first sliding rail and the second sliding rail are mounted on the testing rack, and a first scale and a second scale are respectively mounted on a side of the testing rack opposite to the first sliding rail and the second sliding rail.

[0014] The second aspect of the present application provides a pure bending moment testing method based on double vertical sliding rails, comprising: Adjusting the angle of the test sample on the second clamp to ensure that the initial bending angle of the test sample is 0°; Clamping both ends of the test sample on the first clamp and the second clamp; Recording the positions of the first clamp and the second clamp at the initial moment; Driving the first clamp, and stopping driving the first clamp when the test sample is twisted to a predetermined angle; A small disturbance is applied to the first slider and / or the second slider, so that the first torque sensor and the second torque sensor have the same reading, and the torque reading and the position of the first clamp and the second clamp at this time are recorded; The bending moment test is repeated until the torque test of all target bending angles is completed.

[0015] Further, the sample is a linear bending sheet material or a non-linear ultra-thin flexible material.

[0016] The beneficial effects of the above scheme are: The present application adopts a double vertical sliding rail scheme, releases the non-bending force by driving the sample to bend and allowing the free movement of the two ends of the sample, so as to perform a pure bending test of a large rotation angle, and ensures the accuracy of the test result. Compared with the existing three-point bending and four-point bending test device, the present application is not only suitable for linear bending test material structures such as plates, spring steels, rulers and the like which can be subjected to bending test in a conventional universal material testing machine, but also can perform a non-linear pure bending test of a large angle range on different types of materials such as ultra-thin flexible structures, so as to meet the test requirements of various materials and structures under large deformation conditions, and significantly improve the universality of the bending test. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a test schematic diagram of the three-point bending test in the prior art; Figure 2 It is a front view structural schematic diagram of the pure bending test device provided in the embodiment of the present application; Figure 3 It is a side view structural schematic diagram of the pure bending test device provided in the embodiment of the present application; Figure 4 It is a principle diagram of the sample in the present application before the pure bending test is performed; Figure 5 It is a principle diagram of the sample in the present application when the pure bending test is performed at a rotation angle of θ; Figure 6 It is a test schematic diagram of the pure bending test of the spring steel sample in the present application. In the drawings: 10, first sliding rail; 20, first clamp; 21, first clamping plate; 22, second clamping plate; 30, second sliding rail; 40, second clamp; 50, first slider; 60, driving motor; 70, second slider; 80, test frame; 90, sample. DETAILED DESCRIPTION

[0018] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0019] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0020] The present application will be further described below in combination with the drawings and specific embodiments, but not as a limitation of the present application.

[0021] As shown in the drawings, Figures 2 to 5 The pure bending test device provided in the embodiments of the present application includes a first slide rail 10 and a second slide rail 30. The first clamp 20 (as a driving end) is rotatably installed on the first slide rail 10 and can reciprocate along the first slide rail 10. The second slide rail 30 is perpendicular to the first slide rail 10, and the second clamp 40 (as a driven end) is installed on the second slide rail 30 and can reciprocate along the second slide rail 30.

[0022] In the present application, the first slide rail 10 and the second slide rail 30 which are perpendicular to each other but not intersected are introduced, and the first clamp 20 and the second clamp 40 are respectively installed on the first slide rail 10 and the second slide rail 30 to clamp both ends of the sample 90. During the test, the driving end first clamp 20 is controlled and twisted to apply a bending moment to the sample 90. Since both ends of the sample 90 are located on two perpendicular slide rails, the sample 90 is allowed to slide on the plane without interference and collision, effectively releasing its transverse and longitudinal motion freedom, thereby eliminating the reaction force interference in the plane. This design suppresses the additional force couple generated by external support, so that the sample 90 presents a pure bending moment action condition during the loading process. The bending deformation of the sample 90 is only caused by the bending moment, which provides the possibility for real-time measurement of the bending moment of the sample 90.

[0023] Further, as shown in the drawings, Figure 2 , Figure 3As shown, the first slide rail 10 is provided with a first sliding block 50, the first sliding block 50 can slide reciprocatingly along the first slide rail 10, and the first sliding block 50 is provided with a driving motor 60 (the driving motor 60 is provided with a driver and a programmable controller, and the controller is used to adjust the rotating speed and direction of the motor), and the first clamp 20 is mounted on the driving shaft of the driving motor 60; correspondingly, the second slide rail 30 is provided with a second sliding block 70, the second sliding block 70 can slide reciprocatingly along the second slide rail 30, and the second clamp 40 is fixedly mounted on the second sliding block 70; the above structure can ensure that each component such as the first clamp 20 and the second clamp 40 effectively moves.

[0024] Further, in order to effectively and quickly measure the bending moment, the first clamp 20 is provided with a first torque sensor (not shown in the figure), and the second clamp 40 is provided with a second torque sensor (not shown in the figure), the torque sensor transmits the output torque of the motor to the sample, and the reading of the digital display of the torque sensor also shows the bending moment applied to the sample 90 by the driving end.

[0025] Further, as shown in Figure 2 , Figure 3 in order to effectively record the position changes of the driving end and the driven end of the sample 90 during the bending process, the above device can be mounted on the test rack 80, the first slide rail 10 and the second slide rail 30 are mounted on the test rack 80, and the test rack 80 is provided with a first scale and a second scale (not shown in the figure) on the side opposite to the first slide rail 10 and the second slide rail 30, so that the position changes of the driving end and the driven end can be quickly recorded through the first scale and the second scale.

[0026] As shown in Figure 2 , Figure 3 the first clamp 20 and the second clamp 40 in the application have the same structure and each include first clamping plates 21 and second clamping plates 22 which are arranged in a spaced manner, the first clamping plates 21 and the second clamping plates 22 have a certain spacing therebetween and are used as mounting cavity structures for one end of the sample 90; the bottom of the first clamping plate 21 is detachably mounted on the driving shaft of the driving motor 60 or the second sliding block 70, and after one end of the sample 90 is inserted into the mounting cavity structure, the second clamping plate 22 is fixedly mounted on the first clamping plate 21 through a fastening bolt, so that the clamping of the sample 90 is completed. As shown in Figure 3 in order to facilitate the stable clamping and centering installation of the sample 90, the first clamp 20 and the second clamp 40 in the application face each other.

[0027] The test method of the above pure bending moment test device based on the double vertical sliding rails is as follows: adjust the angle of the sample 90 on the second clamp 40 to ensure that the initial bending angle of the sample 90 is 0°; clamp both ends of the sample 90 on the first clamp 20 and the second clamp 40; record the positions of the first clamp 20 and the second clamp 40 at the initial moment; drive the first clamp 20, and stop driving the first clamp 20 when the test sample 90 is twisted to a predetermined angle; a slight disturbance is applied to the first slider and / or the second slider, so that the first torque sensor and the second torque sensor have the same reading (which indicates that no additional lateral force or longitudinal force is generated at both ends, and only bending moments with equal size and opposite directions exist in the system, so that it can be determined that the test sample 90 is in a pure bending state), which indicates that the test sample 90 is in a pure bending state at this moment, and the torque reading and the positions of the first clamp 20 and the second clamp 40 at this moment are recorded; repeat the bending moment test until the torque test of all target bending angles is completed.

[0028] Based on the above device and method, the present application measures a test spring steel sample (which is formed by laser cutting a commercially available spring steel sheet) with a thickness of 0.3 mm, a width of 10 mm, and a length of 100 mm. The initial state of the test nonlinear bistable hinge is a flat state (i.e., no deformation, and the included angle is 0°, as shown in (a) of Figure 6 During the test, the driving motor rotates the sample to produce bending deformation at a step angle of 2°, and the non-bending force generated during the rotation is released along the double-vertical slide rails through the sliders, so that the sample only bears pure bending moment. The driving motor accurately controls the rotation angle of the sample, and the first torque sensor and the second torque sensor collect voltage signals in real time and calculate the corresponding bending moment values. By mutually calibrating the torque readings of the driving end and the driven end, the accuracy of the test is further improved.

[0029] The test shows that the error between the measured bending moment value and the theoretically calculated value (which can also be considered to be given to the full if the data is available) is within 12%, which indicates that the device can effectively realize the pure bending moment response test and analysis of the nonlinear bistable hinge under large deformation conditions.

[0030] The above description is only the preferred embodiments of the present application, and does not limit the implementation and protection scope of the present application. Those skilled in the art should be able to realize that any equivalent replacement and obvious changes made according to the content of the present application should be included in the protection scope of the present application.

Claims

1. A pure bending moment test device based on dual vertical sliding tracks, characterized in that: include a first slide rail, on which a first clamp is rotatably mounted, and the first clamp can slide back and forth along the first slide rail; as well as The second slide rail is perpendicular to the first slide rail, and a second clamp is installed on the second slide rail, and the second clamp can slide back and forth along the second slide rail.

2. The pure bending moment test device based on dual vertical sliding tracks according to claim 1 is characterized in that: The pure bending moment testing device further includes a first slider, which is mounted on the first slide rail. The first slider can slide back and forth along the first slide rail, and the first fixture can be rotatably mounted on the first slider.

3. The pure bending moment test device based on dual vertical sliding tracks according to claim 2 is characterized in that: The pure bending moment testing device further includes a driving motor, a base of the driving motor is mounted on the first slider, and the first fixture is mounted on a driving shaft of the driving motor.

4. The pure bending moment test device based on dual vertical sliding tracks according to claim 3 is characterized in that: The pure bending moment testing device further includes a second slider, which is mounted on the second slide rail. The second slider can slide back and forth along the second slide rail, and the second fixture is fixedly mounted on the second slider.

5. The pure bending moment testing device based on double vertical sliding tracks according to claim 4 is characterized in that: The first clamp and the second clamp have the same structure and both include a first clamp and a second clamp that are spaced apart. The bottom of the first clamp is correspondingly mounted on the drive shaft of the drive motor or the second slider, and the second clamp can be fixedly mounted on the first clamp.

6. The pure bending moment testing device based on double vertical sliding tracks according to claim 5 is characterized in that: The second clamping plate is fixedly mounted on the first clamping plate by fastening bolts.

7. The pure bending moment testing device based on dual vertical sliding tracks according to claim 5 or 6, characterized in that: A first torque sensor is installed on the first fixture, and a second torque sensor is installed on the second fixture.

8. The pure bending moment testing device based on dual vertical sliding tracks according to claim 7, characterized in that: The pure bending moment test device further includes a test frame, the first slide rail and the second slide rail are mounted on the test frame, and a first scale and a second scale are respectively mounted on one side of the test frame opposite to the first slide rail and the second slide rail.

9. A pure bending moment test method based on dual vertical sliding tracks, characterized in that: The pure bending moment testing device based on dual vertical sliding tracks according to claim 7 or 8 comprises: Adjust the angle of the sample on the second fixture to ensure that the initial bending angle of the sample is 0°; Clamping the two ends of the sample on the first clamp and the second clamp; Recording the positions of the first clamp and the second clamp at an initial moment; driving the first clamp, and stopping driving the first clamp when the sample is twisted to a predetermined angle; Applying a small disturbance to the first slider and / or the second slider so that the readings of the first torque sensor and the second torque sensor are the same, and recording the torque readings and the positions of the first clamp and the second clamp at this time; Repeat the bending moment test until the moment tests for all target bending angles are completed.

10. The pure bending moment test method based on dual vertical sliding tracks according to claim 9, characterized in that: The sample is a linear curved sheet material or a nonlinear ultra-thin flexible material.

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