Sheet material FLC curve test sample sheet set capable of easily acquiring DIC data and acquisition method

Abstract

The invention discloses a sheet material FLC curve test sample piece set easy to acquire DIC data and an acquisition method, the sheet material FLC curve test sample piece set comprises test sample pieces with a uniform arc radius, and the width of each test sample piece in the sheet material FLC curve test sample piece set is gradually reduced in an equal proportion. The deformation and fracture positions are concentrated between two arc fixed ends in the center of the test sample, the sample set for FLC curve test is formed by 9 groups of rectangular test samples, the length / width forming sizes of the test samples comprise 1-9 groups of test samples, the radiuses of arcs on two sides of the test samples are R127, and the radiuses of the arcs on two sides of the test samples are R127. The starting end of the arc radius starts from one end point of the test sample, and the tail end of the arc radius is located at the other end point of the test sample.

Description

Technical Field

[0001] The invention belongs to the technical field of metal forming testing, and in particular relates to a sample set for plate FLC curve testing for easy collection of DIC data and a collection method. Background Art

[0002] The determination of forming limit curves has been widely used in the evaluation of metal material forming, and is required by stamping and other forming processing manufacturers and material suppliers. The current national standard design of the sample shape is a circular sheet with arcs and horizontal lines on both sides, which is suitable for the use of forming test machine molds with draw ribs. The sample set required to form an FLC curve is a*b=180*180, 180*160, 180*140, 180*120, 160*100, 140*80, 120*60, 100*40, 80*20 (the above notches are arcs r=30 at both ends, the length of the middle horizontal line is 30mm, and b is the length of the minimum distance in the center of the sample), and it is not smooth and uniform, which will be difficult to affect when subjected to force. In the experiment described in the literature, it cannot guarantee the uniform transition of the stress state, so it cannot guarantee that the rupture position is ideally distributed at the top.

[0003] The upper and lower dies without draw ribs usually use rectangular samples. The sample set required to form an FLC curve is a*b=180*180, 180*160, 180*140, 180*120, 180*100, 180*80, 180*60, 180*40, 180*20. However, in the actual experiment, the rectangular steel plate is often affected by the lubrication effect when receiving the head pressure, and the rupture position is distributed at the edge of the steel plate sample, resulting in poor DIC data collection effect. Even if there is sufficient lubrication, when the steel plate size is large (above 180*60), the steel plate will be affected by anisotropy and weak thickness uniformity, and the rupture position will frequently be distributed at the edge, making it difficult to collect data.

[0004] In view of the above pain points, a sample set and a collection method for plate FLC curve testing that are easy to collect DIC data are provided, which has the advantage of easy collection of the fracture position. Summary of the invention

[0005] The object of the present invention is to provide a sample set and acquisition method for plate FLC curve testing that can easily acquire DIC data, so as to solve the problems raised in the above-mentioned background technology.

[0006] The objective of the present invention is achieved through the following technical scheme: a set of test pieces for FLC curve testing of plate materials that is easy to collect DIC data, the set of test pieces for FLC curve testing includes test pieces with a uniform arc radius, the width of each test piece in the set of test pieces for FLC curve testing decreases in proportion, and the deformation and rupture positions are concentrated between the two arc fixed ends in the center of the test piece.

[0007] Furthermore, the FLC curve test sample set is formed by 9 groups of rectangular test samples, and the length / width dimensions of the test samples include 1-9 groups of test samples, specifically including a*b=180*254, 180*234, 180*214, 180*194, 180*174, 180*154, 180*134, 180*114, 180*94.

[0008] Furthermore, the arc radius on both sides of the test sample is R127, the starting end of the arc radius starts from one end point of the test sample, and the end of the arc radius is located at the other end point of the test sample.

[0009] The width of each test sample in the FLC curve test sample set is reduced by 20 mm in a proportional decreasing manner.

[0010] A data collection method for a plate FLC curve test sample set for easily collecting DIC data comprises the following steps:

[0011] The first step is to select the FLC curve test sample set test sample and material, and use the wire cutting machine to make the board into the test sample;

[0012] In the second step, the test specimen is placed in the fixture of the testing machine and the strain rate is applied;

[0013] Step 3: When the test specimen breaks or irreversible strain occurs under the strain rate state in Step 2, the test is stopped;

[0014] The fourth step is to record the fracture location and the strain at the time of fracture;

[0015] Step 5: Repeat the test several times to obtain the fracture position and strain at different strain rates;

[0016] Step 6: Draw the forming limit curve based on the test results.

[0017] Furthermore, in the first step, four tripods are set up, and the four tripods are symmetrically arranged. Cameras are installed on the tripods. The camera lenses are facing the test samples, and the cameras are facing the image areas that need to be captured on the test samples. When the image area that needs to be captured meets the preset image size and the preset image frame rate, the focal length and focal length of the camera are locked.

[0018] Furthermore, in the third step, when the distance between the test sample and the test machine fixture reaches a preset threshold, the camera collects image data of the image area of ​​the test sample that needs to be collected to determine the image data corresponding to the DIC experimental data, and determines the DIC experimental data based on the image data and the collection time corresponding to the image data to complete the collection of the DIC experimental data.

[0019] Furthermore, the camera is connected to an external computer, and the hydraulic cylinder of the material testing machine is started to punch and stretch the test sample until cracks appear at the fracture position and strain of the test sample at different strain rates. The camera captures the entire test sample process and transmits the entire image to the computer.

[0020] Furthermore, the computer has built-in DIC software, which is used to process the surface strain image of the sample during the entire deformation process and calculate the ultimate strain value of the sample;

[0021] Replace 1-9 groups of test specimens with different widths, and repeat steps 2-5 until the ultimate strain values ​​of all specimens in the group are obtained;

[0022] According to the strain change cloud diagram of samples of different widths calculated by computer software, each limit strain value point is connected into a line to draw the FLC curve of the test sample.

[0023] An electronic device for data acquisition of a sample set for plate FLC curve testing that can easily acquire DIC data comprises a central processing unit and a memory, wherein the central processing unit is used to call and run a computer program stored in the memory to execute the steps of the above method.

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

[0025] The present invention is suitable for the shape of FLC test specimens without draw ribs. The sample preparation is relatively simple and can be done by arc cutting with a uniform radius. The experiment conducted using the set can obtain data with the same strain range as that in the traditional method to form FLC. The deformation and rupture positions of the test specimens of the present invention are concentrated between the two arc fixed ends in the center of the steel plate, which has the advantage of easy collection of the rupture positions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of a sample set for FLC curve testing of the present invention;

[0027] Figure 2 It is a schematic diagram of the data acquisition framework of the present invention. DETAILED DESCRIPTION

[0028] The technical solutions 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 only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] In the description of the present invention, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention. Specific embodiment one:

[0032] like Figure 1 As shown, a set of test pieces for FLC curve testing of plate materials that is easy to collect DIC data, the set of test pieces for FLC curve testing includes test pieces with a uniform arc radius, the width of each test piece in the set of test pieces for FLC curve testing decreases in proportion, and the deformation and rupture positions are concentrated between the two arc fixed ends in the center of the test piece.

[0033] The FLC curve test sample set is formed by 9 groups of rectangular test samples, and the length / width dimensions of the test samples include 1-9 groups of test samples, specifically including a*b=180*254, 180*234, 180*214, 180*194, 180*174, 180*154, 180*134, 180*114, and 180*94.

[0034] The arc radius on both sides of the test sample is R127, the starting end of the arc radius starts from one end point of the test sample, and the end of the arc radius is located at the other end point of the test sample.

[0035] The width of each test sample in the FLC curve test sample set is reduced by 20 mm in a proportional decreasing manner.

[0036] The FLC curve test sample set used in the above embodiment can ensure a uniform transition of the stress state in the experiment, and can ensure that the rupture position is ideally distributed between the two arc fixed ends in the center of the trial sample during the test.

[0037] The above embodiment is applicable to the shape of the FLC test specimen without drawbeads, and has the advantage that the rupture position can be easily collected. Specific embodiment 2:

[0039] like Figure 2 As shown, a data acquisition method for a sample set for plate FLC curve testing that is easy to acquire DIC data includes the following steps:

[0040] The first step is to select the FLC curve test sample set test sample and material, and use the wire cutting machine to make the board into the test sample;

[0041] Four tripods are set up symmetrically, and cameras are installed on the tripods. The camera lenses are facing the test samples, and the cameras are facing the image areas that need to be captured on the test samples. When the image area that needs to be captured meets the preset image size and the preset image frame rate, the focal length and focal length of the camera are locked.

[0042] By setting four groups of cameras to respectively aim at the image areas to be collected, when the image area to be collected meets the preset image size and the preset image frame rate, the focal length and focal length of the camera are locked so that the camera can collect a clear image with a suitable size.

[0043] Among them, when making the test sample, a set of speckle patterns are made on the surface of the test sample, cross-marked, or a stamp is used for quick and convenient random pattern sample marking;

[0044] In the second step, the test specimen is placed in the fixture of the testing machine and the strain rate is applied;

[0045] When the test sample is ready, during the loading process of the test sample testing machine, the camera (CCD binocular industrial camera) synchronously collects images and simultaneously records the force value simulation information of the testing machine;

[0046] Step 3: When the test specimen breaks or irreversible strain occurs under the strain rate state in Step 2, the test is stopped;

[0047] When the distance between the test sample and the test machine fixture reaches a preset threshold, the camera collects image data of the image area of ​​the test sample that needs to be collected, determines the image data corresponding to the DIC experimental data, and determines the DIC experimental data based on the image data and the collection time corresponding to the image data to complete the collection of the DIC experimental data.

[0048] In order to facilitate timely capturing of clear and appropriately sized images when in use, a camera control program preset in the computer device collects image data for the image area that needs to be collected on the test sample.

[0049] The four groups of cameras are respectively connected to an external computer to start the hydraulic cylinder of the material testing machine to punch and stretch the test sample until cracks appear at the fracture position and strain of the test sample at different strain rates. The camera captures the entire test sample process and transmits the entire image to the computer.

[0050] The fourth step is to record the fracture location and the strain at the time of fracture;

[0051] Step 5: Repeat the test several times to obtain the fracture position and strain at different strain rates;

[0052] Step 6: Draw the forming limit curve based on the test results.

[0053] The computer has built-in DIC software, which is used to process the surface strain image of the sample during the entire deformation process and calculate the ultimate strain value of the sample. 1-9 groups of test specimens with different widths are replaced, and steps 2-5 are repeated until the ultimate strain values ​​of all samples in the group are obtained. According to the strain change cloud diagram of samples with different widths calculated by the computer software, each ultimate strain value point is connected into a line, that is, the FLC curve of the test specimen is drawn.

[0054] like Figure 2 As shown, the computer is electrically connected to the four cameras via connecting wires, and the computer is connected to the testing machine via connecting wires. Specific embodiment three:

[0056] An electronic device for data acquisition of a plate FLC curve test sample set that can easily acquire DIC data comprises a central processing unit and a memory, wherein the central processing unit is used to call and run a computer program stored in the memory to execute a data acquisition method for the plate FLC curve test sample set for DIC data. Specific embodiment four:

[0058] A test monitoring device, the monitoring device comprising four groups of cameras, two of which are arranged in front of a test machine, and the other two groups of cameras are arranged behind the test machine, and the four groups of cameras use image information at different positions;

[0059] The monitoring device also includes an external computer connected to the four groups of cameras. The computer has a built-in processor. The processor performs three-dimensional reconstruction on the images collected by the four groups of cameras to obtain three-dimensional reconstruction parameter data.

[0060] The above-mentioned test monitoring device performs three-dimensional reconstruction on the collected sample data, and compares and analyzes it with the original untested samples. The external computer stores the original 1-9 groups of test sample three-dimensional images a*b=180*254, 180*234, 180*214, 180*194, 180*174, 180*154, 180*134, 180*114, 180*94.

[0061] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0062] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A sample set for plate FLC curve testing that can easily collect DIC data, characterized by: The FLC curve test sample set includes test samples with a uniform arc radius. The width of each test sample in the FLC curve test sample set decreases in equal proportion, and the deformation and rupture positions are concentrated between the two arc fixed ends in the center of the test sample.

2. The plate FLC curve test sample set for easy acquisition of DIC data according to claim 1, characterized in that: The FLC curve test sample set is formed by 9 groups of rectangular test samples, and the length / width dimensions of the test samples include 1-9 groups of test samples, specifically including a*b=180*254, 180*234, 180*214, 180*194, 180*174, 180*154, 180*134, 180*114, and 180*94.

3. The plate FLC curve test sample set for easy acquisition of DIC data according to claim 1, characterized in that: The arc radius on both sides of the test sample is R127, the starting end of the arc radius starts from one end point of the test sample, and the end of the arc radius is located at the other end point of the test sample.

4. The plate FLC curve test sample set for easy acquisition of DIC data according to claim 1, characterized in that: The width of each test sample in the FLC curve test sample set is reduced by 20 mm in a proportional decreasing manner.

5. The data acquisition method for the plate FLC curve test sample set for easily acquiring DIC data according to any one of claims 1 to 4, characterized in that: The steps include: The first step is to select the FLC curve test sample set test sample and material, and use the wire cutting machine to make the board into the test sample; In the second step, the test specimen is placed in the fixture of the testing machine and the strain rate is applied; Step 3: When the test specimen breaks or irreversible strain occurs under the strain rate state in Step 2, the test is stopped; The fourth step is to record the fracture location and the strain at the time of fracture; Step 5: Repeat the test several times to obtain the fracture position and strain at different strain rates; Step 6: Draw the forming limit curve based on the test results.

6. The data acquisition method for the plate FLC curve test sample set for easily acquiring DIC data according to claim 5, characterized in that: In the first step, four tripods are set up, and the four tripods are symmetrically arranged. Cameras are installed on the tripods. The camera lenses are facing the test samples, and the cameras are facing the image areas that need to be captured on the test samples. When the image area that needs to be captured meets the preset image size and the preset image frame rate, the focal length and focal length of the camera are locked.

7. The data acquisition method for the plate FLC curve test sample set for easily acquiring DIC data according to claim 6, characterized in that: In the third step, when the distance between the test sample and the test machine fixture reaches a preset threshold, the camera collects image data of the image area of ​​the test sample that needs to be collected to determine the image data corresponding to the DIC experimental data, and determines the DIC experimental data based on the image data and the collection time corresponding to the image data to complete the collection of the DIC experimental data.

8. The data acquisition method for the plate FLC curve test sample set for easily acquiring DIC data according to claim 7, characterized in that: The camera is connected to an external computer, and the hydraulic cylinder of the material testing machine is started to punch and stretch the test sample until cracks appear at the fracture position and strain of the test sample at different strain rates. The camera captures the entire test sample process and transmits the entire image to the computer.

9. The data acquisition method for the plate FLC curve test sample set for easily acquiring DIC data according to claim 8, characterized in that: The computer has built-in DIC software, which is used to process the surface strain image of the sample during the entire deformation process and calculate the ultimate strain value of the sample; Replace 1-9 groups of test specimens with different widths, and repeat steps 2-5 until the ultimate strain values ​​of all specimens in the group are obtained; According to the strain change cloud diagram of samples of different widths calculated by computer software, each limit strain value point is connected into a line to draw the FLC curve of the test sample.

10. The electronic device for data acquisition of the plate FLC curve test sample set for easy acquisition of DIC data according to any one of claims 5 to 8 comprises a central processing unit and a memory, characterized in that , the central processing unit is used to call and run the computer program stored in the memory to execute the steps of the method as claimed in any one of claims 1 to 6.

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