CN120801056A - Pure bending moment testing device and testing method based on double vertical sliding tracks - Google Patents

Abstract

The invention relates to a pure bending moment testing device and a testing method based on double vertical sliding tracks. According to the invention, a double vertical sliding track scheme is adopted, and the bending force is released by driving the sample to bend and allowing the free movement of the two ends of the sample, so that a pure bending test with a large rotation angle is performed, and the accuracy of a test result is ensured. Compared with the existing three-point bending and four-point bending testing device, the device is not only suitable for linear bending moment testing material structures such as plates, spring steel and straight rulers which can be subjected to bending tests in conventional universal material testing machines, but also can be used for nonlinear pure bending moment tests with a large angle range on different types of materials such as ultrathin flexible structures, meets the testing requirements of various materials and structures on mechanical properties under the condition of large deformation, and remarkably improves the universality of bending moment testing.

Description

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

Technical Field

The invention relates to the field of mechanical testing of materials and structures, in particular to a pure bending moment testing device and a testing method based on double vertical sliding tracks, which are used for researching the relation between bending moment and rotation angle of a material or a structure in a pure bending state, and are particularly suitable for testing the mechanical properties of nonlinear large-deformation materials or the pure bending moment of the structure.

Background

The bending test is a basic method of testing mechanical properties of a material or structure and is used for testing mechanical properties of a material when subjected to bending loads. The bending test is carried out on a universal material testing machine, the cross section of a sample is circular and rectangular in two loading modes of three-point bending and four-point bending, the span during the test is ten times of the diameter, the measured bending curve takes the load as an ordinate, the deflection of a sample as an abscissa, and the relation between the load and the center line of the sample deviating from the original position is shown. These methods are widely used to measure the bending stiffness and strength of rigid test samples where small deformations occur.

The bending test design of a universal material testing machine is generally suitable for materials with relatively high rigidity, and the relation between bending moment and deformation of the materials is often linear. However, the relationship between bending moment and deformation of the ultrathin flexible material tends to be nonlinear, and taking a thin-shell structure as an example, which is a typical representative of the ultrathin flexible material, the thin-shell structure has the characteristics of thin wall and light weight, and the thickness of the thin-shell structure is very small relative to other two dimensions (such as length and width), and the ratio of the thickness to the other dimensions is generally less than 1/10. At large deformations and forces, the thin shell structure exhibits significant bending or curved deformation and carries the load primarily by bending, shearing, stretching, etc., unlike conventional beams or columns which rely primarily on axial stress. Such structures also involve stress concentrations, buckling and stability issues. Particularly in the case of large deformations or large rotation angles, the loading system and the measuring device of the universal material testing machine have difficulty in precisely controlling or reading the asymmetrical true deformations of the material, with the result that the accuracy and repeatability of the test data are affected. Meanwhile, some ultrathin flexible samples may not be clamped effectively in the clamp of the universal material testing machine, so that uneven loading is caused, and bending moment testing results are affected.

In the existing universal material testing equipment, certain limitations exist for testing the thin-wall structure, and nonlinear response in the large deformation process cannot be effectively simulated. Therefore, it is necessary to design and develop a more satisfactory pure bending moment testing device.

Disclosure of Invention

Aiming at the problems, the pure bending moment testing device and the testing method based on the double vertical sliding tracks are provided, and aim to study the relation between the bending moment and the rotation angle of a material or a structure in a pure bending state, and are particularly suitable for testing the mechanical properties of nonlinear large-deformation materials or the pure bending moment of the structure.

The specific technical scheme is as follows:

a first aspect of the present invention provides a pure bending moment testing device based on a double vertical sliding rail, comprising:

a first slide rail on which a first clamp is rotatably mounted, the first clamp being reciprocally slidable along the first slide rail, and

The second slide rail is perpendicular to the first slide rail, a second clamp is arranged on the second slide rail, and the second clamp can slide back and forth along the second slide rail.

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 slide back and forth along the first sliding rail, and the first clamp is rotatably mounted on the first sliding block.

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

Further, the pure bending moment testing device further comprises a second sliding block, the second sliding block is arranged on the second sliding rail, the second sliding block can slide back and forth along the second sliding rail, and the second clamp is fixedly arranged on the second sliding block.

Further, the first clamp and the second clamp are identical in structure and comprise a first clamp plate and a second clamp plate which are arranged at intervals, the bottom of the first clamp plate is arranged on a driving shaft or a second sliding block of the driving motor, and the second clamp plate can be fixedly arranged on the first clamp plate.

Further, the second clamping plate is fixedly arranged on the first clamping plate through a fastening bolt.

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

Further, the pure bending moment testing device further comprises a testing machine frame, the first sliding rail and the second sliding rail are arranged on the testing machine frame, and a first graduated scale and a second graduated scale are respectively arranged on one side, opposite to the first sliding rail and the second sliding rail, of the testing machine frame.

A second aspect of the present invention provides a pure bending moment testing method based on a dual vertical sliding rail, comprising:

Adjusting the angle of the sample on the second clamp to ensure that the initial bending angle of the sample is 0 degrees;

Clamping two ends of a sample on a first clamp and a 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 sample is twisted to a predetermined angle;

applying a micro disturbance to the first slider and/or the second slider to enable the readings of the first torque sensor and the second torque sensor to be the same, and recording the torque readings and the positions of the first clamp and the second clamp at the moment;

And repeating the bending moment test until the moment test of all the target bending angles is completed.

Further, the sample is a linear bending sheet material or a nonlinear ultrathin flexible material.

The beneficial effect of above-mentioned scheme is:

According to the invention, a double vertical sliding track scheme is adopted, and the bending force is released by driving the sample to bend and allowing the free movement of the two ends of the sample, so that a pure bending test with a large rotation angle is performed, and the accuracy of a test result is ensured. Compared with the existing three-point bending and four-point bending testing device, the device is not only suitable for linear bending moment testing material structures such as plates, spring steel and straight rulers which can be subjected to bending tests in conventional universal material testing machines, but also can be used for nonlinear pure bending moment tests with a large angle range on different types of materials such as ultrathin flexible structures, meets the testing requirements of various materials and structures on mechanical properties under the condition of large deformation, and remarkably improves the universality of bending moment testing.

Drawings

FIG. 1 is a schematic illustration of a prior art three-point bend test;

FIG. 2 is a schematic diagram of a front view of a pure bending moment testing device according to an embodiment of the present invention;

FIG. 3 is a schematic side view of a pure bending moment testing device according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a sample of the present invention prior to performing a pure bending moment test;

FIG. 5 is a schematic diagram of the invention for performing a pure moment test when the sample is rotated by an angle θ;

FIG. 6 is a schematic illustration of a test of the spring steel sample of the present invention for pure bending moment testing.

In the drawing, 10 parts of a first sliding rail, 20 parts of a first clamp, 21 parts of a first clamping plate, 22 parts of a second clamping plate, 30 parts of a second sliding rail, 40 parts of a second clamping plate, 50 parts of a first sliding block, 60 parts of a driving motor, 70 parts of a second sliding block, 80 parts of a test stand, 90 parts of a test sample.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.

The invention is further described below with reference to the drawings and specific examples, which are not intended to be limiting.

As shown in fig. 2 to 5, the pure bending moment testing device provided in the embodiment of the invention comprises a first sliding rail 10 and a second sliding rail 30, wherein a first clamp 20 (the first clamp 20 is used as a driving end) is rotatably installed on the first sliding rail 10, the first clamp 20 can slide reciprocally along the first sliding rail 10, the second sliding rail 30 is perpendicular to the first sliding rail 10, a second clamp 40 (the second clamp 40 is used as a driven end) is installed on the second sliding rail 30, and the second clamp 40 can slide reciprocally along the second sliding rail 30.

According to the invention, two mutually perpendicular first slide rails 10 and second slide rails 30 which are not intersected are introduced, two ends of a sample 90 are clamped by a first clamp 20 and a second clamp 40 respectively positioned on the first slide rail 10 and the second slide rail 30, and the first clamp 20 at the driving end is controlled and twisted during test, so that a bending moment is applied to the sample 90, and as the two ends of the sample 90 are positioned on the two perpendicular slide rails, the sample 90 is allowed to slide on a plane without interference collision, the movement degrees of the sample 90 in the transverse direction and the longitudinal direction are effectively released, and the reactive force interference in the plane is eliminated. This design inhibits the additional couple created by the external support, allowing the specimen 90 to assume a purely moment acting condition during loading. So that bending deformation of the test specimen 90 is caused only by bending moment, and it is possible to measure the bending moment of the test specimen 90 in real time.

Further, as shown in fig. 2 and 3, in the present invention, the first slide rail 10 is mounted with a first slide block 50, the first slide block 50 can slide reciprocally along the first slide rail 10, the first slide block 50 is mounted with a driving motor 60 (the driving motor 60 is configured with a driver and a programmable controller, and the controller is used for adjusting the rotation speed and the rotation direction of the motor), the first clamp 20 is mounted on the driving shaft of the driving motor 60, the second slide rail 30 is correspondingly mounted with a second slide block 70, the second slide block 70 can slide reciprocally along the second slide rail 30, and the second clamp 40 is fixedly mounted on the second slide block 70, and the above structure can ensure the effective operation of the first clamp 20, the second clamp 40 and other components.

Further, in order to effectively and rapidly measure the magnitude of the bending moment, in the present invention, a first torque sensor (not shown) is mounted on the first clamp 20, a second torque sensor (not shown) is mounted on the second clamp 40, the torque sensor transmits the output torque of the motor to the sample, and the readings of the digital display meter also show the magnitude of the bending moment applied to the sample 90 by the driving end.

Further, as shown in fig. 2 and 3, to effectively record the position changes of the driving end and the driven end of the recording sample 90 in the bending process, the device may be installed on the test stand 80, the first slide rail 10 and the second slide rail 30 are installed on the test stand 80, and a first scale and a second scale (not shown) are respectively installed on one side of the test stand 80 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 are quickly recorded by the first scale and the second scale.

As shown in fig. 2 and 3, the first clamp 20 and the second clamp 40 of the present invention have the same structure and each include a first clamping plate 21 and a second clamping plate 22 arranged at intervals, a certain interval is provided between the first clamping plate 21 and the second clamping plate 22 for being used as a mounting cavity structure of one end of the sample 90, the bottom of the first clamping plate 21 is detachably mounted on a driving shaft of the driving motor 60 or the second sliding block 70, and when one end of the sample 90 extends into the mounting cavity structure, the second clamping plate 22 is fixedly mounted on the first clamping plate 21 through fastening bolts, thereby completing the clamping of the sample 90. As shown in fig. 3, to facilitate secure clamping and centering of the test specimen 90, the first clamp 20 and the second clamp 40 of the present invention are oppositely oriented.

The testing method using the pure bending moment testing device based on the double vertical sliding tracks comprises the following steps:

adjusting the angle of the sample 90 on the second clamp 40 to ensure that the initial bend angle of the sample 90 is 0 °;

clamping the two ends of the sample 90 on the first clamp 20 and the second clamp 40;

Recording the positions of the first clamp 20 and the second clamp 40 at the initial time;

driving the first clamp 20, and stopping driving the first clamp 20 when the specimen 90 is twisted to a predetermined angle;

Applying a small disturbance to the first slider and/or the second slider to cause the first torque sensor and the second torque sensor to read the same (indicating that no additional transverse force or longitudinal force is generated at both ends, and that only equal and opposite bending moments are present in the system, so that a pure bending state can be determined), indicating that the sample 90 is in a pure bending state, and recording the torque readings and the positions of the first clamp 20 and the second clamp 40 at that time;

And repeating the bending moment test until the moment test of all the target bending angles is completed.

Based on the device and the method, the spring steel sample to be tested (formed by laser cutting and shaping of a commercially available spring steel sheet) with the thickness of 0.3mm, the width of 10mm and the length of 100mm is actually measured, the initial state of the nonlinear bistable hinge to be tested is in a straight state (namely, the initial state is not deformed, the included angle is 0 degrees, as shown in fig. 6 (a)), and the included angle reaches 30 degrees after the test is finished. In the testing process, the driving motor gradually rotates the sample at a step angle of 2 degrees to generate bending deformation, and the non-bending force generated in the rotating process is freely released along the double vertical sliding rails through the sliding blocks, so that the sample is ensured to only bear the pure bending moment effect. The driving motor accurately controls the rotation angle of the sample, and the first moment sensor and the second moment sensor acquire voltage signals in real time and calculate corresponding bending moment values. The torque readings of the driving end and the driven end are mutually calibrated, so that the accuracy of the test is further improved.

Experiments show that the error between the measured bending moment value and the theoretical calculated value (if the data are at hand, the error can be considered for all) is within 12%, and the device can effectively realize the pure bending moment response test and analysis of the nonlinear bistable hinge under the condition of large deformation.

The foregoing description is only illustrative of the preferred embodiments of the present invention and is not to be construed as limiting the scope of the invention, and it will be appreciated by those skilled in the art that equivalent substitutions and obvious variations may be made using the description and illustrations of the present invention, and are intended to be included within the scope of the present invention.

Claims (10)

1. A pure bending moment testing device based on double vertical sliding tracks is characterized by comprising

A first slide rail, a first clamp rotatably mounted on the first slide rail and capable of sliding reciprocally along the first slide rail, and

The second slide rail, the second slide rail with first slide rail mutually perpendicular, install the second anchor clamps on the second slide rail, the second anchor clamps can follow the reciprocal slip of second slide rail.

2. The dual vertical sliding rail based pure bending moment testing apparatus according to claim 1, further comprising a first slider mounted on the first slide rail, the first slider being reciprocally slidable along the first slide rail, the first clamp being rotatably mounted on the first slider.

3. The dual vertical sliding rail based pure bending moment testing apparatus according to claim 2, further comprising a drive motor, wherein a base of the drive motor is mounted on the first slider, and wherein the first clamp is mounted on a drive shaft of the drive motor.

4. The dual vertical sliding rail based pure bending moment testing apparatus according to claim 3, further comprising a second slider mounted on the second slide rail, the second slider being reciprocally slidable along the second slide rail, the second clamp being fixedly mounted on the second slider.

5. The dual vertical sliding rail based pure bending moment testing apparatus according to claim 4, wherein the first clamp and the second clamp have the same structure and each comprise a first clamping plate and a second clamping plate which are arranged at intervals, the bottom of the first clamping plate is correspondingly arranged on the driving shaft of the driving motor or the second sliding block, and the second clamping plate can be fixedly arranged on the first clamping plate.

6. The dual vertical sliding rail based pure moment testing apparatus of claim 5, wherein the second clamping plate is fixedly mounted to the first clamping plate by fastening bolts.

7. The dual vertical sliding rail based pure moment testing apparatus of claim 5 or 6, wherein the first clamp has a first moment sensor mounted thereon and the second clamp has a second moment sensor mounted thereon.

8. The pure bending moment testing device based on the double vertical sliding rails according to claim 7, further comprising a test rack, wherein the first sliding rail and the second sliding rail are mounted on the test rack, and a first graduated scale and a second graduated scale are mounted on one side of the test rack opposite to the first sliding rail and the second sliding rail respectively.

9. A pure bending moment testing method based on a double vertical sliding rail, characterized in that the pure bending moment testing device based on a double vertical sliding rail according to claim 7 or 8 is used, comprising:

Adjusting the angle of the sample on the second clamp to ensure that the initial bending angle of the sample is 0 degrees;

Clamping two ends of the sample on a first clamp and a 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 sample is twisted to a predetermined angle;

Applying a micro disturbance to the first slider and/or the second slider to make the readings of the first torque sensor and the second torque sensor the same, and recording the torque readings and the positions of the first clamp and the second clamp at the moment;

And repeating the bending moment test until the moment test of all the target bending angles is completed.

10. The method of claim 9, wherein the test specimen is a linear curved sheet material or a nonlinear ultrathin flexible material.