CN113933157A - Tension test method and device for cable insulation dumbbell test piece - Google Patents

Tension test method and device for cable insulation dumbbell test piece Download PDF

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Publication number
CN113933157A
CN113933157A CN202111188561.5A CN202111188561A CN113933157A CN 113933157 A CN113933157 A CN 113933157A CN 202111188561 A CN202111188561 A CN 202111188561A CN 113933157 A CN113933157 A CN 113933157A
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test
test piece
test pieces
cable insulation
dumbbell
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储昭杰
李成钢
张建国
刘伟
张量
陶加贵
戴建卓
赵恒�
宋思齐
朱凤维
王子宁
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Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/02—Details
    • G01N3/04—Chucks
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/02—Details
    • G01N3/06—Special adaptations of indicating or recording means
    • G01N3/068—Special adaptations of indicating or recording means with optical indicating or recording means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0001—Type of application of the stress
    • G01N2203/0003—Steady
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G01N2203/0017—Tensile
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/026—Specifications of the specimen
    • G01N2203/0262—Shape of the specimen
    • G01N2203/0278—Thin specimens
    • G01N2203/028—One dimensional, e.g. filaments, wires, ropes or cables
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/04—Chucks, fixtures, jaws, holders or anvils
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/06—Indicating or recording means; Sensing means
    • G01N2203/0641—Indicating or recording means; Sensing means using optical, X-ray, ultraviolet, infrared or similar detectors

Abstract

The invention discloses a tension test method and a tension test device for a cable insulation dumbbell test piece, which comprise the following steps: scribing: making upper marking lines at the upper ends of the prepared N test pieces, making lower marking lines at the lower ends of the prepared N test pieces, and setting the distance between the inner sides of the upper marking lines and the lower marking lines as a, wherein the lengths of the upper marking lines and the lower marking lines are both b; heating: placing the N marked test pieces in an experimental device, respectively connecting the upper ends of the test pieces with an upper tensile machine, respectively connecting the lower ends of the test pieces with automatic clamps, and arranging a camera outside the experimental device for shooting images of the test pieces at different time points in the experimental device; collecting an image; calculating the vertical deformation rate according to the M groups of image data; the lateral deformation ratio is calculated from the M sets of image data. The invention can accurately determine the position of the marking line and calculate the elongation, automatically find out unqualified test pieces and is convenient to detect.

Description

Tension test method and device for cable insulation dumbbell test piece
Technical Field
The invention relates to a cable insulation test, in particular to a tension test method and a tension test device for a cable insulation dumbbell test piece.
Background
Cables are generally made up of one or more mutually insulated conductors and an outer insulating sheath, belonging to the conductors that transmit electric power or information from one place to another.
The thermal extension test is a test method for checking the load deformation and permanent deformation of the cable insulation or sheath under the action of heat and load, if the cable insulation or sheath deforms under high-temperature load, the mechanical property is lost, even short circuit is caused, and the normal use of the cable is influenced. The test method commonly used at present is to make the cable insulation into the shape of dumbbell test piece, as the basic test piece of test, then fix the upper end of dumbbell test piece in experimental apparatus, a clip of its lower extreme centre gripping, weight is placed gradually on the clip, the percentage elongation of cable insulation is confirmed according to the weight of weight and experimental apparatus time, this kind of test method needs the frequent door of opening experimental apparatus to add the weight, lead to the interior temperature frequent change of experimental apparatus, the weight also can appear simultaneously and place the tensile force slope that the skew leads to, finally lead to final length measurement inaccurate, and the inaccuracy that the percentage elongation calculated.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides the tension testing method and the tension testing device for the cable insulation dumbbell test piece.
In order to achieve the technical purpose, the invention adopts the following technical scheme: a tension test method for a cable insulation dumbbell test piece comprises the following steps:
scribing: making upper marking lines at the upper ends of the prepared N test pieces, making lower marking lines at the lower ends of the prepared N test pieces, and setting the distance between the inner sides of the upper marking lines and the lower marking lines as a, wherein the lengths of the upper marking lines and the lower marking lines are both b;
heating: placing the N marked test pieces in an experimental device, respectively connecting the upper ends of the test pieces with an upper tensile machine, respectively connecting the lower ends of the test pieces with automatic clamps, and arranging a camera outside the experimental device for shooting images of the test pieces at different time points in the experimental device;
collecting an image: shooting once every c milliseconds, obtaining M groups of data as image data of the time point, taking down the automatic clamp after obtaining the M group of data, and shooting an image in a final state after the test piece retracts for a certain time;
calculating the vertical deformation rate according to the M groups of image data;
the lateral deformation ratio is calculated from the M sets of image data.
Further, calculating the vertical deformation ratio from the M sets of image data includes the sub-steps of:
recording the image data shot by the M groups as M1, M2 and M3.. M according to the time sequence, wherein the total number of the M groups is N × M, recording the initial image as M0, and taking the final state after retraction as M is finished;
performing binarization operation on all image data, drawing an upper detection frame around an upper marking line of a binarized image, and drawing a lower detection frame around a lower marking line;
acquiring positions of all pixel points in the upper detection frame, taking an average value of all pixel points as a current upper marking line position, and recording the current upper marking line position as a position A;
acquiring the positions of all pixel points in a lower detection frame, taking the average value of all pixel points as the current lower mark line position, and recording as a position B;
acquiring distances AB1, AB2 and AB3.. ABM between the lower side of the position A and the upper side of the position B of each test piece as the current vertical lengths of M groups of N test pieces, and acquiring AB terminal in a final state;
according to the formula ABi-ABi-1Calculating the deformation amount in unit time, comparing the N deformation amounts at the same time point, and removing P test pieces corresponding to the deformation amount with larger error, wherein i is 1, 2 and 3Final (a Chinese character of 'gan')；
Taking the retracted final state image data of the eliminated N-P test pieces as a calculation object according to a formula
Figure BDA0003300291190000021
Calculating N-P elongation rates f1, f2, f3... fP corresponding to the final state, wherein P<N。
Further, ABi+1-ABi＜ABi-ABi-1。
Further, the method also comprises a grade judging step: if the elongation f is more than 175%, the test piece is judged as a failed test piece.
Further, the method also comprises the following substeps: by N × M ABi-ABi-1And drawing a deformation curve based on the deformation data.
Further, the method also comprises the following substeps: the elongation was plotted on the basis of f1, f2, f3..
Further, the calculating of the lateral deformation ratio from the M sets of image data comprises the sub-steps of:
image binarization: carrying out binarization operation on the last shot image to obtain a binarized image;
obtaining the final length: acquiring the leftmost pixel point position and the rightmost pixel point position of the upper marking line on the binary image, and calculating the distance d1 between the leftmost pixel point and the outer side of the rightmost pixel point; acquiring the leftmost pixel point position and the rightmost pixel point position of the lower marking line on the binary image, and calculating the distance d2 between the leftmost pixel point and the outer side of the rightmost pixel point;
calculating the transverse deformation rate: according to
Figure BDA0003300291190000022
The transverse deformation ratio e1 of the upper mark line of the last image data is calculated based on
Figure BDA0003300291190000023
The transverse deformation ratio e2 of the lower mark line of the last image data was calculated to obtain N pieces of e1 data and N pieces of e2 data, and the average values of e1 and e2 were taken, respectively.
Further, the method also comprises the following substeps: the deformation rate curves of the upper and lower marked lines of the N test pieces were plotted on the basis of the N pieces of e1 data and the N pieces of e2 data.
Further, images were taken every 2 minutes for the first 10 minutes of heating, 5 times in total, and the automatic clamp was removed from the 10 th minute and the specimen was retracted for 5 minutes.
A tension testing device for a cable insulation dumbbell test piece comprises an experiment device, wherein N tension machines are arranged in the experiment device, and N cameras are arranged outside the experiment device and used for shooting images of the N test pieces;
the tension testing device further comprises a display screen and a control host computer, wherein the control host computer is used for executing the tension testing method in any one of claims 1 to 9 and displaying the test on the display screen in real time.
The working steps of the whole automatic device for the thermal extension test are as follows:
1. powering on and starting up the industrial personal computer, and opening control software; when shooting continuously, the time for analyzing 4 pictures by an industrial personal computer is 120ms, and the real-time length is refreshed for 8 times in one second;
2. setting the temperature of the experimental device to 200 ℃, and starting heating;
3. manually clamping the dumbbell test piece with the measured thickness to a hanging rack;
4. inputting the thickness, the serial number and the report serial number of 4 dumbbell test pieces, wherein the serial number and the report serial number can be automatically numbered according to time;
5. the computer controls the page to input the thickness calculation load;
6. the sliding door of the experimental device is pulled open, and the hanging rack is placed on the sliding door of the experimental device;
7. pushing the sliding door into the experimental device;
8. the electric control clamp clamps the bottom of the dumbbell;
9. the tensile machine applies tensile force according to the calculated load;
10. the dumbbell marking lines are visually identified by the camera, and the space between the marking lines is automatically analyzed in real time;
11. displaying the distance on a control page in real time, and reporting an error prompt if the distance cannot be identified;
12. the test piece is prolonged, and the electric tensile machine always keeps the load unchanged;
after heating at 13.200 ℃ for 10 minutes, the main control page displays the final length, and calculates the final elongation rate as (length after extension-original length)/original length as 20 mm;
14. the automatic clamp below the test piece is loosened, and 4 test pieces are contracted for 5 minutes;
15. pulling the sliding door of the experimental device open, and taking out the hanging rack;
16. the first report can be suspended, the test of the next report is continued, and the steps are repeated;
17. cooling the first test piece for half an hour at room temperature;
18. manually measuring the length half an hour later, and filling the length into a computer control interface;
19. generating and printing a first electronic report;
and the background folder stores the real-time length excel file of each test piece.
In conclusion, the invention achieves the following technical effects:
1. the positions of the upper marking line and the lower marking line are determined by a binarization method, so that the determination precision of the marking lines is improved, and accurate guarantee is provided for the calculation of the subsequent length;
2. the invention judges whether the test piece for testing is qualified or not by using the extension length in unit time, and rejects the test piece data when the extension length in unit time is too large or too small, thereby ensuring the calculation precision;
3. the invention can accurately determine the position of the marking line and calculate the elongation, automatically find out unqualified test pieces and is convenient to detect.
Drawings
FIG. 1 is a schematic flow chart of a tension testing method of a cable insulation dumbbell test piece according to an embodiment of the invention;
FIG. 2 is a schematic diagram of a dumbbell test piece;
fig. 3 is 5 sets of image data obtained by shooting;
FIG. 4 is a graph of the data of FIG. 3;
FIG. 5 is a graph showing the change in the extension length per unit time corresponding to FIG. 3;
FIG. 6 is a graph showing the change in the extension length per unit time corresponding to FIG. 5;
FIG. 7 is the elongation at the last shot after culling;
FIG. 8 is a plot of the corresponding elongation of FIG. 7;
FIG. 9 is experimental data for another batch of test pieces;
FIG. 10 is a schematic diagram showing the positional relationship among the camera, the light source, and the test piece in the testing apparatus.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
Example (b):
as shown in fig. 1, a tensile test method of a cable insulation dumbbell test piece comprises the following steps: step S100-step S500:
step S100, scribing: making upper marking lines at the upper ends of the prepared N test pieces, making lower marking lines at the lower ends of the prepared N test pieces, and setting the distance between the inner sides of the upper marking lines and the lower marking lines as a, wherein the lengths of the upper marking lines and the lower marking lines are both b;
in step S100, as shown in fig. 2, a dumbbell test piece is first made, and the dumbbell cable is pressed out by a grinding tool to cut out the insulation, which mainly includes two types, black and white semi-transparent; it is necessary to draw 2 marking lines on the dumbbell specimen, the white specimen is drawn with a black mark stroke, the black specimen is drawn with a white mark stroke, and it is recommended to improve the contrast with a green mark stroke.
The inside distance between two marking lines, i.e. the distance between the lower side of the upper marking line and the upper side of the lower marking line, is initially measured, and when drawn, the nominal a is 20mm and the nominal b is 4 mm.
Step S200, heating: placing the N marked test pieces in an experimental device, respectively connecting the upper ends of the test pieces with an upper tensile machine, respectively connecting the lower ends of the test pieces with automatic clamps, and arranging a camera outside the experimental device for shooting images of the test pieces at different time points in the experimental device;
in this step, the temperature of the experimental device is 200 ℃, the tension of the electric tensile machine is determined according to the thickness of the dumbbell specimen, and the tension is calculated as follows: thickness (mm) of the test piece 0.8N;
the camera and the interior of the experimental device are separated by 2 layers of glass for isolating the temperature of 200 ℃; the outer of the glass is provided with a lighting lamp, and the upper row and the lower row are arranged in parallel and used for shooting and lighting. 4 fixed cameras of 130 ten thousand low pixels continue shooting.
In addition, the clamps at the two ends of the dumbbell test piece are a small distance away from the marking line and can be elongated along with the temperature, and meanwhile, the drawing position of the marking line is manually controlled and is likely to float up and down, so that the precision range of the camera of 0.1mm is larger than 35 mm.
Step S300, image acquisition: taking the image once every c milliseconds, taking M times to obtain M groups of data as image data of the time point, taking down the automatic clamp after the M group of data is obtained, and taking the image in the final state after the test piece retracts for a certain time;
the camera shooting time is multiple times of continuous shooting per second, and in a plurality of shot images, the embodiment takes image data once every 2 minutes, and takes 5 times in total, so that 5 groups of data are obtained. In other tests, images may be taken on the order of milliseconds. The heating time was 15 minutes, image data was taken once at each of the 2 nd, 4 th, 6 th, 8 th and 10 th minutes, and after taking an image at the 10 th minute, an automatic clamp was signaled to open, the lower end of the specimen was released, and the specimen was allowed to naturally retract for 5 minutes, and at the 15 th minute, an image of the final state was taken.
In addition, N is 4 in the present embodiment, and 4 test pieces including N1, N2, N3 and N4 are provided, that is, 4 test pieces are set to be tested simultaneously.
S400, calculating a vertical deformation rate according to the M groups of image data;
in the present embodiment, calculating the vertical deformation ratio includes the following sub-steps:
h100, recording the M groups of shot image data as M1, M2 and M3.. M in time sequence, wherein the total of the M groups is N × M, recording the initial image as M0, and taking the final retracted state as M end;
as shown in fig. 3, n1-n4 in the figure represent data of 4 specimens, m0 lines represent images at the initial time, m1-m5 lines represent photograph data taken at 5 time points, and m6 represents final state data after retraction. The units are all mm.
H200, performing binarization operation on all image data, drawing an upper detection frame around an upper marking line of the binarized image, and drawing a lower detection frame around a lower marking line;
in the binarization processing of the image in this embodiment, the gray level of the points on the N × M images is 255, that is, the entire image is obviously black and white, and the color of the marking line is obviously distinguished from that of the test piece, so that the pixel points can be conveniently selected. And two detection frames are drawn to seal the marking lines, so that the influence of other pixel points is eliminated, and the accuracy of marking line selection is improved.
At high temperatures, the dumbbell specimen is elongated and the score lines are deformed slightly, thereby repositioning the score lines.
H300, acquiring the positions of all pixel points in the upper detection frame, taking the average value of all pixel points as the current upper marker line position, and recording as a position A;
h400, acquiring the positions of all pixel points in the lower detection frame, and taking the average value of all the pixel points as the current lower mark line position to be marked as a position B;
h500, acquiring distances AB1, AB2 and AB3.. ABM between the lower side of the position A and the upper side of the position B of each test piece, wherein the distances AB1, AB2 and AB3.. ABM serve as the current vertical lengths of M groups of N test pieces, and AB terminal in a final state is acquired;
in this embodiment, as shown in fig. 3, the data of N test pieces obtained by shooting at 5 time points are AB1, AB2, and AB3.. ABM, which are total N × M data.
H600, according to formula ABi-ABi-1Calculating the deformation amount in unit time, comparing the N deformation amounts at the same time point, and removing P test pieces corresponding to the deformation amount with larger error, wherein i is 1, 2 and 3Final (a Chinese character of 'gan')；
As shown in fig. 5, the amount of deformation per unit time is calculated, in the first row, m2-m1 is the difference between the AB distance in the second shooting and the AB distance in the first shooting, the first row lists the difference between the second shooting and the first shooting of 4 specimens, and as can be seen from the data in the first row in the figure, the difference n1 is 4.2mm, the difference n2 is 4.9mm, the difference n3 is 0.2mm, and the difference n4 is 3.7mm, where the difference error n3 is greater than n1, n2, and n4, indicating that the specimen 3 has an error, and therefore, a third specimen is removed, that is, the data in the column n3 is removed. Three columns of n1, n2, n4 were used as the calculated data.
Further, ABi+1-ABi＜ABi-ABi-1It is indicated that the cable insulation becomes progressively smaller in length per unit time, which of course is only effective within 10 minutes before heating and is not limited by this formula within 5 minutes from the 10 th minute.
By N × M ABi-ABi-1And drawing a deformation curve based on the deformation data. As shown in fig. 6, which is a curve schematic of the deformation amount of fig. 5, it can be seen that the test piece is a test piece to be rejected as more obvious from the larger difference between the curve point values corresponding to n3 in fig. 6.
Referring to fig. 4, the graph of fig. 3 is shown, and in fig. 4, the n3 data corresponding to the time point m2 has a large variation, so that it can be seen that n3 is to be eliminated.
In the invention, unqualified products are removed by using the deformation in unit time, so that the unqualified products are prevented from influencing the test result.
H700, taking the retracted final state image data of the eliminated N-P test pieces as a calculation object according to a formula
Figure BDA0003300291190000071
Calculating N-P elongation rates f1, f2, f3... fP corresponding to the final state, wherein P<N；
As shown in fig. 7, n3 is removed, i.e. when P is 1, the initial length and final length of n1, n2 and n4 are left, and the elongation at this time is 71.5%, 68.5% and 63% calculated according to the above formula.
As shown in fig. 8, the elongation was plotted on the basis of f1, f2, f3..
The following rules are determined in advance: if the elongation f is larger than 175%, judging the test piece as an unqualified test piece, and if the elongation f exceeds 175%, changing 20mm into 55mm, namely, judging the test piece as unqualified, wherein the precision in the interval is +/-0.1 mm; if the elongation f is more than 150% and less than 175%, the test piece is judged as a qualified test piece, and if the elongation f is less than 150%, the test piece is judged as a good test piece. In the experiment, three test pieces n1, n2 and n4 all belong to the qualified grade, so that the three test pieces are judged to be qualified.
Over 175% to 250% of the data is still recorded, i.e. 20mm to between 55mm to 70mm, the accuracy can be relaxed appropriately, and over 250% of the data is not recorded.
When the insulation of the same batch of cables is tested, the mean elongation f of the batch can be calculated according to the respective elongations: h800, and f1, f2, f3... fP are averaged to obtain the vertical elongation f. In this example, the average value of the elongation percentage f of the lot obtained by averaging 71.5%, 68.5%, and 63% was 67.7%, and it was possible to roughly judge that the insulation of the cable of the lot was in a good state.
For another example, as shown in fig. 9, it is understood that the specimens n5 and n7 have an elongation of more than 175%, and are rejected specimens, and the specimens n6 have an elongation of more than 150% and less than 175%, and are accepted specimens.
And step S500, calculating the transverse deformation rate according to the M groups of image data. The method comprises the following substeps:
k100, image binarization: carrying out binarization operation on the last shot image to obtain a binarized image;
k200, obtaining the final length: acquiring the leftmost pixel point position and the rightmost pixel point position of the upper marking line on the binary image, and calculating the distance d1 between the leftmost pixel point and the outer side of the rightmost pixel point; acquiring the leftmost pixel point position and the rightmost pixel point position of the lower marking line on the binary image, and calculating the distance d2 between the leftmost pixel point and the outer side of the rightmost pixel point;
k300, calculating the transverse deformation rate: according to
Figure BDA0003300291190000081
The transverse deformation ratio e1 of the upper mark line of the last image data is calculated based on
Figure BDA0003300291190000082
Calculating the number of last imagesThe lateral deformation ratio of the lower marker line, e2, was found to be N data of e1 and N data of e2, which were averaged for e1 and e2, respectively.
The circumferential ductility of the test piece can be known by the transverse elongation e, the acceptable cable insulation should be shrunk in the circumference, i.e. in the transverse direction, and if the test data e is greater than 1 or much less than 1 at this time, the extension in the circumferential direction can be judged to be not acceptable. The transverse deformation rate e of the cable insulation material is different according to different cable insulation materials, different thickness weights and the like, so that the size of e can be obtained by initial experiments according to the performance of a test piece during actual tests.
Further comprising the sub-steps of: the deformation rate curves of the upper and lower marked lines of the N test pieces were plotted on the basis of the N pieces of e1 data and the N pieces of e2 data. The form of the curve is more convenient to see the degree of lateral deformation.
According to the invention, the vertical elongation is calculated, the horizontal elongation is also calculated, the qualified condition of the cable insulation test piece in production can be known by using the horizontal elongation, which test piece is unqualified can be seen through the vertical extension length in unit time, the horizontal elongation can be seen to see whether the batch of material is qualified or not in production, the cable insulation produced by the qualified material has small extension in the horizontal direction, if the horizontal elongation is found to be large in test, the unqualified produced material can be pushed back, the reason for the unqualified cable can be traced in time, and the unqualified cable insulation is prevented from being applied to the cable.
In another embodiment, the tension testing device for the cable insulation dumbbell test piece comprises an experimental device, wherein N tension machines are arranged in the experimental device;
arranging N cameras outside the experimental device and shooting images of the N test pieces; as shown in fig. 10, two strips of light are used for lighting, the position, height and illumination angle of the light source need to be finely adjusted on site, and the support is kept adjustable. And adjusting the picture to finally make the illumination of the imaging picture uniform. And (4) visually scanning the distance between the two marking lines according to the drawn marking lines, and transmitting the processed result to the PLC through the MODBUS-TCP.
The tension testing device further comprises a display screen and a control host, wherein the control host is used for executing the tension testing method and displaying the test on the display screen in real time.
The implementation case is as follows: the working steps of the whole automatic device for the thermal extension test are as follows:
1. powering on and starting up the industrial personal computer, and opening control software; when shooting continuously, the time for analyzing 4 pictures by an industrial personal computer is 120ms, and the real-time length is refreshed for 8 times in one second;
2. setting the temperature of the experimental device to 200 ℃, and starting heating; the experimental device can adopt an oven;
3. manually clamping the dumbbell test piece with the measured thickness to a hanging rack;
4. inputting the thickness, the serial number and the report serial number of 4 dumbbell test pieces, wherein the serial number and the report serial number can be automatically numbered according to time;
5. the computer controls the page to input the thickness calculation load;
6. the sliding door of the experimental device is pulled open, and the hanging rack is placed on the sliding door of the experimental device;
7. pushing the sliding door into the experimental device;
8. the electric control clamp clamps the bottom of the dumbbell;
9. the tensile machine applies tensile force according to the calculated load;
10. the dumbbell marking lines are visually identified by the camera, and the space between the marking lines is automatically analyzed in real time;
11. displaying the distance on a control page in real time, and reporting an error prompt if the distance cannot be identified;
12. the test piece is prolonged, and the electric tensile machine always keeps the load unchanged;
after heating at 13.200 ℃ for 10 minutes, the main control page displays the final length, and calculates the final elongation rate as (length after extension-original length)/original length as 20 mm;
14. the automatic clamp below the test piece is loosened, and 4 test pieces are contracted for 5 minutes;
15. pulling the sliding door of the experimental device open, and taking out the hanging rack;
16. the first report can be suspended, the test of the next report is continued, and the steps are repeated;
17. cooling the first test piece for half an hour at room temperature;
18. manually measuring the length half an hour later, and filling the length into a computer control interface;
19. generating and printing a first electronic report;
20. and the background folder stores the real-time length excel file of each test piece.
In addition, the requirements for the test device are designed as follows:
the ventilation heating system is positioned at the rear lower part of the box body, the ventilation volume is adjustable, and the control system is positioned on the right side surface of the test box. The box body has the advantages that the box body has good heat insulation performance;
the air duct interlayer at the left end and the right end of the working chamber is internally provided with a heater, a fan blade and other devices, the test box is a single-door, and the box body is designed for energy conservation and heat preservation and does not drift after long-term operation. PID controls the temperature, a 304 stainless steel armor is adopted as a laboratory heater, a high-quality nichrome heating wire type heater is adopted, the heating speed is high and uniform, and the standby time is reduced;
the shell is made by assembling high-quality cold steel plates and is welded and formed; the whole body is subjected to electrostatic spraying treatment, so that the appearance is attractive and tidy; the inner container material: high-quality stainless steel;
the indirect control of the circulating air exchange rate in the control box is realized through the setting of the instrument, and the stepless regulation air exchange assembly is composed of a variable-frequency forced centrifugal blower, a speed regulation frequency converter, a circulating air duct and the like;
the silicon rubber sealing strip is adopted, so that the high-temperature and low-temperature resistance, the ageing resistance and the good sealing performance are achieved;
and thickened high-temperature-resistant rock wool is adopted in the interlayer for heat preservation and insulation. The thickness of the heat preservation layer is 150 mm;
a constant temperature control system: cold and hot balance circulation is carried out in a natural heat dissipation convection mode to achieve the purpose of constant temperature control; heating control is carried out by adopting an SSR contactless solid-state relay in a PWM high-frequency pulse output mode; the heater is armored by 304 stainless steel and is a high-quality nichrome heating wire type heater, the heating temperature is fast, and the service life is long; PID operation regulation is adopted to command the execution of the non-contact solid-state relay; the PT100 sensor armored by 304 stainless steel is adopted for temperature monitoring, corrosion resistance is realized, and the service life is long; the chip adopts imported German Heley A-level thin film resistor.
The test system comprises: the temperature controller adopts a space electric AI518 series temperature control instrument and a Kunlun touch screen to detect and control the temperature required in the box, the control precision is high, and the operation is simple and convenient; the operating method of humanized design is easy to learn and use, and the instrument operations of different functional grades are mutually considered; the input adopts a digital correction system, the measurement is accurate and stable, and the temperature compensation function is realized, so that the actual temperature deviation can be corrected conveniently; the intelligent alarm system has the functions of position type regulation and AI artificial intelligence PID regulation and multiple alarm modes; the data recording mode has data recording and storing functions, supports the utilization of a USB memory, and can replace a recorder.
In order to eliminate the damage of a camera, a black screen of an industrial personal computer, the damage of a serial port and a network port of the industrial personal computer, the damage of a system of the industrial personal computer and the like caused by electromagnetic interference, the following requirements are particularly provided for the installation of the camera and the industrial personal computer: 1; the ground wire and the equipment of the power supply inlet wire are reliably grounded in a direct grounding mode, so that the camera, the industrial personal computer and the display screen are connected to the same power supply. 2; the industrial personal computer power line and the camera power line cannot be connected to the same power line with the driver. A filter or an isolation transformer is added at the power supply inlet wire to avoid current surge interference caused by unstable power supply voltage and sudden action. 3; if the camera and the industrial personal computer are not close to the high-power driver or the motor, a separation plate is added in the middle to reduce electromagnetic interference. 4; the camera network cable, the trigger signal wire, the industrial personal computer display screen wire and the like are separately wired with the power wire, and if the distance is too close, a shielding layer is added to shield interference. 5; when the camera and the PLC are connected by a signal line, the camera and the PLC should be grounded.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not intended to limit the present invention in any way, and all simple modifications, equivalent variations and modifications made to the above embodiments according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.

Claims (10)

1. A tension test method of a cable insulation dumbbell test piece is characterized by comprising the following steps: the method comprises the following steps:
scribing: making upper marking lines at the upper ends of the prepared N test pieces, making lower marking lines at the lower ends of the prepared N test pieces, and setting the distance between the inner sides of the upper marking lines and the lower marking lines as a, wherein the lengths of the upper marking lines and the lower marking lines are both b;
heating: placing the N marked test pieces in an experimental device, respectively connecting the upper ends of the test pieces with an upper tensile machine, respectively connecting the lower ends of the test pieces with automatic clamps, and arranging a camera outside the experimental device for shooting images of the test pieces at different time points in the experimental device;
collecting an image: taking the image once every c milliseconds, taking M times to obtain M groups of data as image data of the time point, taking down the automatic clamp after the M group of data is obtained, and taking the image in the final state after the test piece retracts for a certain time;
and calculating the vertical deformation rate according to the M groups of image data.
2. The tension test method of the cable insulation dumbbell test piece according to claim 1, characterized in that: calculating the vertical deformation ratio from the M sets of image data includes the sub-steps of:
recording the image data shot by the M groups as M1, M2 and M3.. M according to the time sequence, wherein the total number of the M groups is N × M, recording the initial image as M0, and taking the final state after retraction as M is finished;
performing binarization operation on all image data, drawing an upper detection frame around an upper marking line of a binarized image, and drawing a lower detection frame around a lower marking line;
acquiring positions of all pixel points in the upper detection frame, taking an average value of all pixel points as a current upper marking line position, and recording the current upper marking line position as a position A;
acquiring the positions of all pixel points in a lower detection frame, taking the average value of all pixel points as the current lower mark line position, and recording as a position B;
acquiring distances AB1, AB2 and AB3.. ABM between the lower side of the position A and the upper side of the position B of each test piece as the current vertical lengths of M groups of N test pieces, and acquiring AB terminal in a final state;
according to the formula ABi-ABi-1Calculating the deformation amount in unit time, comparing the N deformation amounts at the same time point, and removing P test pieces corresponding to the deformation amount with larger error, wherein i is 1, 2 and 3Final (a Chinese character of 'gan')；
Taking the retracted final state image data of the eliminated N-P test pieces as a calculation object according to a formula
Figure FDA0003300291180000011
Calculating N-P elongation rates f1, f2, f3... fP corresponding to the final state, wherein P<N。
3. The tension test method of the cable insulation dumbbell test piece according to claim 2, characterized in that: ABi+1-ABi＜ABi-ABi-1。
4. The tension test method of the cable insulation dumbbell test piece according to claim 3, characterized in that: further comprises a grade judging step: if the elongation f is more than 175%, the test piece is judged as a failed test piece.
5. The tension test method of the cable insulation dumbbell test piece according to claim 4, characterized in that: further comprising the substeps of: by N × M ABi-ABi-1And drawing a deformation curve based on the deformation data.
6. The tension test method of the cable insulation dumbbell test piece according to claim 5, characterized in that: further comprising the substeps of: the elongation was plotted on the basis of f1, f2, f3..
7. The tension test method of the cable insulation dumbbell test piece according to claim 1, characterized in that: further comprising: the lateral deformation ratio is calculated from the M sets of image data.
8. The tension test method of the cable insulation dumbbell test piece according to claim 7, characterized in that: further comprising the sub-steps of: and drawing the deformation rate curves of the upper marked lines and the lower marked lines of the N test pieces on the basis of the transverse deformation rate.
9. The tension test method of a cable insulation dumbbell test piece according to any one of claims 1 to 8, characterized in that: images were taken every 2 minutes for the first 10 minutes of heating, 5 times in total, and the automated clamp was removed from the 10 th minute and the specimen retracted for 5 minutes.
10. The utility model provides a tensile test device of cable insulation dumbbell test piece which characterized in that: the device comprises an experimental device, wherein N tensile machines are arranged in the experimental device, and N cameras are arranged outside the experimental device and used for shooting images of N test pieces;
the tension testing device further comprises a display screen and a control host computer, wherein the control host computer is used for executing the tension testing method in any one of claims 1 to 9 and displaying the test on the display screen in real time.
CN202111188561.5A 2021-10-12 2021-10-12 Tension test method and device for cable insulation dumbbell test piece Pending CN113933157A (en)

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