Measuring device and testing method for testing Poisson ratio of honeycomb core material

Abstract

The invention discloses a measuring device and a testing method for testing the Poisson's ratio of a honeycomb core material. The Poisson's ratio testing device comprises a cylindrical fixture, and a sample for testing the Poisson's ratio is positioned on the top surface of the cylindrical fixture and is clamped by the fixture to form a saddle shape; the size measuring device comprises a horizontal testing assembly for testing the chord length of the saddle-shaped sample and a vertical testing assembly for testing the depth value from the chord length center point to the surface of the sample. According to the Poisson's ratio testing device and the testing method, mechanical size measurement is realized, personnel operation steps are reduced, one person can complete size measurement, the labor cost is reduced, the testing efficiency is improved, the accuracy and the consistency are improved, and further use and popularization of the standard ASTM D6790 are facilitated.

Description

Technical Field

[0001] The invention relates to the field of detection technology, and in particular to a measuring device and a testing method for testing the Poisson's ratio of a honeycomb core material. Background Art

[0002] In the aviation field, as the application scope of composite materials expands, the surface design of some parts continues to become more complex, and the performance requirements for honeycomb materials are becoming more diverse. At present, in order to meet the requirements of large curvature parts for the flexibility of honeycomb materials, the deformation performance of honeycomb core materials after being subjected to force, especially the test of Poisson's ratio, has gradually attracted attention in the industry.

[0003] Poisson's ratio refers to the ratio of the transverse strain to the axial strain when the material is strained by a uniaxial stress. For honeycomb core materials, since they are non-homogeneous and anisotropic materials, their cells will deform differently in the L and W directions after being subjected to stress. At present, the test of Poisson's ratio of honeycomb core materials usually adopts ASTM D6790 / D6790M-22 "Standard Test Method for Determining Poisson's Ratio of Honeycomb Core Materials". The process is to place a 300mm×300mm square honeycomb core material sample on a cylindrical device with a fixed radius Rc, and fix the midpoints of the two opposite sides of the sample on the cylinder so that the sample is completely fitted with the cylinder along these two points, and the other set of opposite sides is warped into a saddle shape. By measuring the chord length of the midpoints of the two warped sides and the depth from the center of the chord length to the surface of the sample, the radius Ra of the curved surface formed by the warped side of the sample is calculated, and the Poisson's ratio of the sample is expressed as Rc / Ra. This method is simple in principle, but there are problems such as large influence of human factors, low accuracy and poor efficiency in actual operation, as follows:

[0004] (1) In order to ensure that the arc between the midpoints of one set of opposite sides of the specimen is completely in contact with the cylinder, one person is required to press the specimen with his fingers during the test. Due to the different thickness and strength of fingers between different people, the relatively soft surface of the specimen is deformed to different degrees, thus forming different saddle-shaped specimens, which has a great influence on the results.

[0005] (2) Honeycomb core material samples are relatively soft. When using contact-type dimension measuring instruments such as steel rulers or calipers to measure their deformed dimensions, it is inevitable that pressure will be applied to the sample, causing the measured Ra to be too low, thus affecting the Poisson’s ratio value.

[0006] (3) The test operation requires the cooperation of multiple people, namely, one person presses the sample, one person measures the chord length between the warped edges of the sample, and one person measures the depth of the chord center point, which results in high labor costs and low efficiency. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a measuring device and a testing method for the Poisson's ratio test of honeycomb core materials. The Poisson's ratio testing device and the testing method realize mechanized dimensional measurement, reduce the number of operating steps, and one person can complete the dimensional measurement, thereby reducing labor costs, improving testing efficiency, and improving accuracy and consistency, which is conducive to the further use and promotion of standard ASTM D6790.

[0008] In one aspect, a measuring device for testing the Poisson's ratio of a honeycomb core material comprises:

[0009] A cylindrical fixture, wherein a specimen for Poisson's ratio test is positioned on the top surface of the cylindrical fixture and clamped by the fixture to form a saddle shape;

[0010] A dimension measuring device comprises a horizontal testing component for testing the chord length of a saddle-shaped specimen and a vertical testing component for testing the depth value from the center point of the chord length to the surface of the specimen.

[0011] As a preferred embodiment of the above technical solution, the cylindrical fixture includes a cylinder body, a magnetic limit block on the top surface of the cylinder body, the limit block is used to position the geometric center of the sample to be aligned with the center of the highest point of the cylinder body, and spring clips are installed on the front and rear sides of the cylinder body, the spring clips are arranged at the midpoint of the front and rear edges of the sample, and the spring clips are used to clamp the sample and bend the sample into a saddle shape through its clamping force.

[0012] As a preferred embodiment of the above technical solution, the cylinder body is a cylinder or an arc-shaped structure with a constant diameter.

[0013] As a preferred embodiment of the above technical solution, the horizontal test assembly includes a level ruler, the level ruler is provided with measuring claws for reading the scale of the level ruler, and both ends of the level ruler are positioned by guide columns and can be vertically adjusted up and down along the guide columns.

[0014] As a preferred embodiment of the above technical solution, the zero point of the level ruler is set exactly opposite to the center point of the chord length of the warped edge of the sample.

[0015] As a preferred embodiment of the above technical solution, a slider is provided on the guide column, and both ends of the level are fastened to the slider. The slider can move vertically up and down along the guide column and is locked to the guide column by a fastener.

[0016] As a preferred embodiment of the above technical solution, the vertical test assembly includes a height gauge, which is installed on the horizontal ruler. The height gauge is arranged opposite to the center point of the chord length of the warped edge of the specimen, and the height gauge can be adjusted vertically up and down.

[0017] As a preferred embodiment of the above technical solution, a sleeve is vertically installed on the level ruler, and the height ruler passes through the sleeve and is locked by a fastener.

[0018] On the other hand, a test method for a Poisson's ratio test device is provided, wherein the Poisson's ratio test is performed using the above test device, and the specific test process is as follows:

[0019] Step 1: According to the size of the sample, position the sample on the top of the cylinder fixture by magnetic positioning, ensure that the geometric center of the sample is aligned with the center of the highest point of the cylinder, and record the radius Rc of the cylinder fixture;

[0020] Step 2: Clamp the sample with a fixture to form the sample into a saddle shape.

[0021] Step 3: Adjust the positions of the horizontal test assembly and the vertical test assembly, and obtain the chord length between the warped edges of the specimen and the depth value from the chord center point to the specimen surface by reading the scale values ​​of the horizontal test assembly and the vertical test assembly;

[0022] Step 4, calculating the radius Ra of the curved surface formed by the warped edge of the specimen according to the chord length and depth values ​​in step 3;

[0023] Step 5: Calculate the Poisson's ratio of the sample based on the cylinder radius Rc in step 1 and the curved surface radius Ra in step 4.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The Poisson's ratio test device and test method have changed the manual measurement method, realized mechanized measurement, reduced the number of operation steps, and reduced human errors. By selecting the appropriate spring clip to stabilize the contact pressure and adjust the contact area, one person can complete the measurement, reducing labor costs, improving test efficiency, accuracy and consistency, and facilitating the further use and promotion of the standard ASTM D6790. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the present invention.

[0027] Figure 2 It is a schematic diagram of the structure of the cylinder clamp of the present invention.

[0028] The accompanying drawings are marked as follows: 1-cylinder fixture, 101-cylinder body, 102-limiting block, 103-spring clip, 2-dimension measuring device, 201-level ruler, 202-measuring claws, 203-guide column, 204-slider, 205-height gauge, 206-sleeve, 3-sample. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0031] On the one hand, if Figure 1 The present invention provides a measuring device for testing the Poisson's ratio of a honeycomb core material, comprising:

[0032] A cylindrical fixture 1, a sample 3 for Poisson's ratio test is positioned on the top surface of the cylindrical fixture 1 and clamped by a fixture to form a saddle shape;

[0033] The dimension measuring device 2 comprises a horizontal testing component for testing the chord length of the saddle-shaped specimen 3 and a vertical testing component for testing the depth value from the center point of the chord length to the surface of the specimen 3.

[0034] In this embodiment, the cylinder fixture 1 includes a cylinder body 101, and a magnetic limit block 102 is attached to the top surface of the cylinder body 101. Specifically, the cylinder body 101 is an iron cylinder, and the limit block 102 is a magnet. The limit block 102 is used to position the geometric center of the sample 3 so that it is aligned with the center of the highest point of the cylinder body 101. Spring clips 103 are installed on the front and rear sides of the cylinder body 101. The spring clips 103 are arranged at the midpoint of the front and rear edges of the sample 3. The spring clips 103 are used to clamp the sample 3 and bend the sample 3 into a saddle shape through its clamping force.

[0035] In this embodiment, the cylinder body 101 is a cylinder or arc-shaped structure with a constant diameter. In this embodiment, the cylinder body 101 with a semicircular longitudinal section is taken as an example. Figure 2 shown.

[0036] In this embodiment, the horizontal test assembly includes a level ruler 201 , on which are provided claws 202 for reading the scale of the level ruler 201 . Both ends of the level ruler 201 are positioned by guide columns 203 and can be adjusted vertically up and down along the guide columns 203 .

[0037] In this embodiment, the zero point of the level ruler 201 is set exactly opposite to the center point of the chord length of the warped edge of the sample 3 .

[0038] In this embodiment, a slider 204 is provided on the guide column 203 , and both ends of the level 201 are fastened to the slider 204 . The slider 204 can move vertically up and down along the guide column 203 and is locked to the guide column 203 by fasteners.

[0039] In this embodiment, the vertical test assembly includes a height ruler 205, which is installed on the horizontal ruler 201. The height ruler 205 is arranged opposite to the center point of the chord length of the warped edge of the sample 3, and the height ruler 205 can be adjusted vertically up and down.

[0040] In this embodiment, a sleeve 206 is vertically mounted on the level ruler 201 , and the height ruler 205 passes through the sleeve 206 and is locked by a fastener.

[0041] It is necessary to supplement the description that, in the present embodiment, the guide column 203 can be directly fixed to the top of the cylinder body 101, or a bracket for installing the guide column 203 can be additionally provided as needed to meet the positions of the level ruler 201 and the height ruler 205; the fasteners can be any fastening method such as screws and bolts; in addition, the radius of the cylinder body 101 can be adjusted according to the size of the object to be measured, and the clamp can be a spring clip 103 with stable contact pressure selected as needed, and the limit block 102 has a magnetic suction function, and the position can be adjusted according to the size of the sample.

[0042] On the other hand, a test method for a Poisson's ratio test device is provided, wherein the Poisson's ratio test is performed using the above test device, and the specific test process is as follows:

[0043] Step 1: According to the size of the sample 3, position the sample 3 on the top of the cylinder fixture 1 by magnetic positioning, ensure that the geometric center of the sample 3 is aligned with the center of the highest point of the cylinder, and record the radius Rc of the cylinder fixture;

[0044] Step 2: clamp the sample by a fixture to form the sample 3 into a saddle shape.

[0045] Step 3: Adjust the positions of the horizontal test assembly and the vertical test assembly, and obtain the chord length between the warped edges of the sample 3 and the depth value from the chord center point to the surface of the sample 3 by reading the scale values ​​of the horizontal test assembly and the vertical test assembly;

[0046] Step 4, calculating the radius Ra of the curved surface formed by the warped edge of the sample 3 according to the chord length and depth value in step 3;

[0047] Step 5: Calculate the Poisson's ratio of the sample based on the cylinder radius Rc in step 1 and the curved surface radius Ra in step 4.

[0048] Specifically, during the sample installation process, the cylinder body 101 is used to bend the sample 3 into a specific shape, and the limit block 102 is used to limit the mounting position of the sample 3. According to different sample sizes, the position of the limit block 102 with a magnetic attraction function is adjusted to keep the geometric center of the sample 3 aligned with the center of the highest point of the cylinder body 101. In this process, the left and right length dimensions of the sample 3 are first measured. Since the center of the highest point of the cylinder body 101 has been measured, the distance between the limit block 102 and the center of the highest point of the cylinder body 101 is half of the left and right length dimensions of the sample 3. The position of the limit block 102 can be determined. After the limit block 102 is magnetically attracted to the cylinder body 101, one side of the sample 3 is placed against the limit block 102 to complete the positioning of the sample 3. After the sample 3 is in place, two spring clips 103 are used to align the sample 3 as a group. The midpoint of the edge is pressed on the cylinder body 101, and the positions of the two sliders 204 on the guide column 203 are adjusted respectively, so that the left and right lower edges of the level 201 are in contact with the left and right warped edges of the sample respectively, and the screws on the sliders 204 are tightened to fix the position of the level 201, and the position of the measuring claws 202 is adjusted to make it contact with the upper edge of the right warped edge of the sample 3, and the fixing screws of the measuring claws 202 are tightened. The position of the height gauge 205 is adjusted to make the lower surface of the height gauge 205 contact with the sample 3 (the spring clips 103 of the limit block 102 do not affect the measurement of the level gauge 201 and the height gauge 205), and the fixing screws on the height gauge 205 are tightened. The scales of the measuring claws 202 on the level gauge 201 and the height gauge 205 are read respectively, and the chord length between the warped edges of the sample 3 and the depth value from the center point of the chord to the surface of the sample 3 can be obtained.

[0049] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A measuring device for testing the Poisson's ratio of honeycomb core material, characterized in that: include: A cylindrical fixture, wherein a specimen for Poisson's ratio test is positioned on the top surface of the cylindrical fixture and clamped by the fixture to form a saddle shape; A dimension measuring device comprises a horizontal testing component for testing the chord length of a saddle-shaped specimen and a vertical testing component for testing the depth value from the center point of the chord length to the surface of the specimen.

2. The measuring device for testing the Poisson's ratio of honeycomb core material according to claim 1, characterized in that: The cylindrical fixture comprises a cylinder body, a magnetic limit block on the top surface of the cylinder body, the limit block is used to position the geometric center of the sample to align with the center of the highest point of the cylinder body, and spring clips are installed on the front and rear sides of the cylinder body, the spring clips are arranged at the midpoints of the front and rear edges of the sample, and the spring clips are used to clamp the sample and bend the sample into a saddle shape through its clamping force.

3. The measuring device for testing the Poisson's ratio of honeycomb core material according to claim 2, characterized in that: The cylinder body is a cylinder or an arc-shaped structure with a constant diameter.

4. The measuring device for testing the Poisson's ratio of honeycomb core material according to claim 1, characterized in that: The level test assembly comprises a level ruler, on which are provided measuring claws for reading the scale of the level ruler, and both ends of the level ruler are positioned by guide columns and can be adjusted vertically up and down along the guide columns.

5. The measuring device for testing the Poisson's ratio of honeycomb core material according to claim 4, characterized in that: The zero point of the level ruler is set exactly opposite to the center point of the chord length of the warped side of the sample.

6. The measuring device for testing the Poisson's ratio of honeycomb core material according to claim 4, characterized in that: The guide column is provided with a slider, and both ends of the level are fastened to the slider. The slider can move vertically up and down along the guide column and is locked to the guide column by a fastener.

7. The measuring device for testing the Poisson's ratio of honeycomb core material according to claim 4, characterized in that: The vertical test assembly comprises a height gauge, which is mounted on the horizontal ruler. The height gauge is arranged opposite to the center point of the chord length of the warped edge of the sample, and the height gauge can be adjusted vertically up and down.

8. The measuring device for testing the Poisson's ratio of honeycomb core material according to claim 7, characterized in that: A sleeve is vertically mounted on the level ruler, and the height ruler passes through the sleeve and is locked by a fastener.

9. A testing method for a Poisson's ratio testing device, characterized in that: The Poisson's ratio test is performed using the test device described in any one of claims 1 to 8, and the specific test process is as follows: Step 1: According to the size of the sample, position the sample on the top of the cylinder fixture by magnetic positioning, ensure that the geometric center of the sample is aligned with the center of the highest point of the cylinder, and record the radius Rc of the cylinder fixture; Step 2: Clamp the sample with a fixture to form the sample into a saddle shape. Step 3: Adjust the positions of the horizontal test assembly and the vertical test assembly, and obtain the chord length between the warped edges of the specimen and the depth value from the chord center point to the specimen surface by reading the scale values ​​of the horizontal test assembly and the vertical test assembly; Step 4, calculating the radius Ra of the curved surface formed by the warped edge of the specimen according to the chord length and depth values ​​in step 3; Step 5: Calculate the Poisson's ratio of the sample based on the cylinder radius Rc in step 1 and the curved surface radius Ra in step 4.

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