CN108469453B - Crack resolution detection method - Google Patents
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- 238000001514 detection method Methods 0.000 title claims abstract description 41
- 238000012360 testing method Methods 0.000 claims abstract description 47
- 230000008447 perception Effects 0.000 claims abstract description 3
- 238000000034 method Methods 0.000 claims description 24
- 238000012544 monitoring process Methods 0.000 claims description 14
- 239000000853 adhesive Substances 0.000 claims description 2
- 230000001070 adhesive effect Effects 0.000 claims description 2
- 239000003292 glue Substances 0.000 claims 1
- 230000035772 mutation Effects 0.000 claims 1
- 239000000463 material Substances 0.000 description 14
- 238000010586 diagram Methods 0.000 description 4
- 238000006073 displacement reaction Methods 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000009533 lab test Methods 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000009661 fatigue test Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/041—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body
Abstract
The invention provides a crack resolution detection method, which comprises the following steps: preparing a tested target sample comprising a prefabricated crack; fixing a sensing layer on the tested target sample along the direction crossed with the extending direction of the prefabricated crack, wherein the sensing layer is separated from the prefabricated crack by a preset distance; mounting a tested target sample on a test device; connecting two ends of the sensing layer to a sensing layer on-off detector; loading a tested target sample along a direction crossed with the extending direction of the prefabricated crack; when the sensing layer on-off detector detects the sudden change of the resistance, the loading speed is reduced to zero; determining a resolution of a perception layer; and (4) unloading the tested target sample from the test equipment.
Description
Technical Field
The invention relates to the field of detection, in particular to a crack resolution detection method.
Background
The invention patent application with publication number CN 106442637a relates to a flange crack monitoring device and method, in which a crack detection sheet is mounted on a detected surface, cracks are monitored by monitoring the on-off state of a resistor (i.e., on-off crack monitoring method), when the resistance of the crack detection sheet is small, the detected surface is considered to be complete and has no cracks, and when the resistance of the crack detection sheet is large, for example, a threshold value of 10 is set6When the resistance is high, it is considered that the surface to be inspected has cracks. However, the patent application does not mention how to determine the resolution of the crack, i.e. the minimum crack width that can be detected by on-off crack monitoring.
The resolution of the cracks is a key index of the on-off crack monitoring method, and the smaller the cracks can be distinguished by the on-off crack monitoring method, the higher the resolution is, the more the cracks can be found as soon as possible, so that the cracks can be treated in more sufficient time. On the contrary, if the cracks which can be distinguished by the on-off crack monitoring method are too large, the cracks cannot be early warned, and even cannot be early monitored. In addition, when determining the scheme of the on-off crack monitoring method, the material of the sensing layer, the fixing process of the sensing layer, the shape and size of the sensing layer, the working temperature of the sensing layer, and the like have great influence on the monitoring effect of the on-off crack monitoring method, and when evaluating the schemes of different on-off crack monitoring methods, the resolution of different monitoring schemes also needs to be compared so as to determine the optimal sensing layer material, the fixing process of the sensing layer, the shape and size of the sensing layer, the working temperature of the sensing layer, and the like. In the conventional method of determining the resolution of the scheme of the on-off crack monitoring method, the resolution is generally obtained by observing the condition of crack propagation in the field, and the method is inconvenient to test and has poor repeatability due to the fact that the complexity of field conditions causes data dispersion.
Disclosure of Invention
In order to solve the above problems, the present invention provides a crack resolution detection method to be able to quickly and efficiently detect resolutions of sensing layers of different parameters.
According to an aspect of the present invention, there is provided a crack resolution detection method, the method including: preparing a tested target sample comprising a prefabricated crack; fixing a sensing layer on the tested target sample along the direction crossed with the extending direction of the prefabricated crack, wherein the sensing layer is separated from the prefabricated crack by a preset distance; mounting a tested target sample on a test device; connecting two ends of the sensing layer to a sensing layer on-off detector; loading a tested target sample along a direction crossed with the extending direction of the prefabricated crack; when the sensing layer on-off detector detects the sudden change of the resistance, the loading speed is reduced to zero; determining a resolution of a perception layer; and (4) unloading the tested target sample from the test equipment.
According to an embodiment of the present invention, the crack resolution detection method may further include: and forming a crack stop hole in the tested target sample along the extending direction of the prefabricated crack, so that the sensing layer is positioned between the prefabricated crack and the crack stop hole.
According to the embodiment of the invention, the loading direction of the tested target sample can be perpendicular to the extending direction of the pre-crack.
According to an embodiment of the invention, the direction of extension of the pre-crack may be perpendicular to the fixing direction of the sensing layer.
According to the embodiment of the present invention, the target specimen may have a substantially rectangular parallelepiped shape, and the pre-crack may be formed along a width direction of the target specimen and penetrate one side edge of the target specimen.
According to an embodiment of the present invention, the length of the pre-crack may be 1/10 to 1/2 of the width of the target specimen to be measured.
According to embodiments of the present invention, the loading speed of the test apparatus may be between 0.01mm/min and 0.1 mm/min.
According to an embodiment of the present invention, the width of the pre-crack may be 0.5mm or less.
According to an embodiment of the invention, the diameter of the crack stop hole may be between 5mm and 10 mm.
According to embodiments of the present invention, the size of the target specimen to be tested may be determined by the testing apparatus.
According to an embodiment of the invention, the width of the sensing layer may be between 1mm and 5 mm.
According to embodiments of the invention, the sensing layer may have a thickness of between 0.1mm and 0.5 mm.
The crack resolution detection method according to the exemplary embodiment of the present invention has the following advantages: as a result of the laboratory experiments, the resolution of the sensing layer can be determined quickly (e.g., 10 minutes) by setting the appropriate loading load; because the test conditions of the laboratory can be accurately controlled, the test result has high precision, good reproducibility and high data reliability; because the test is carried out in a laboratory, the related test equipment and various preparations are easy to carry out, and the test is convenient; the resolution of the sensing layer can be compared quickly for different materials, different fixation processes, different shapes and different temperatures.
In addition, according to the crack resolution detection method of the exemplary embodiment of the invention, since the pre-fabricated crack and the crack arrest hole are arranged on the tested target sample, the resolutions of the sensing layers with different parameters can be determined quickly and effectively, so that the structures and processes of the sensing layer material, the process for fixing the sensing layer, the shape and the size of the sensing layer and the like can be optimized.
Drawings
FIG. 1 is a diagram of a target specimen under test prepared according to a crack resolution detection method of an exemplary embodiment of the present invention;
FIG. 2 is a schematic illustration of a crack resolution detection method according to an exemplary embodiment of the present invention with a sensing layer fixed on a target specimen under test;
FIG. 3 is a schematic illustration of the loading of a target test specimen under test according to a crack resolution detection method in an exemplary embodiment of the invention.
Detailed Description
Exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Like reference numerals refer to like elements throughout the specification.
Fig. 1 is a diagram of a test object specimen 1 prepared by a crack resolution detection method according to an exemplary embodiment of the present invention.
As shown in fig. 1, the shape of the target sample 1 to be tested prepared by the crack resolution detection method according to the exemplary embodiment of the present invention can be determined according to the shape and the loading condition of the target object to be tested, for example, when the target object to be tested is a pitch bearing, since the pitch bearing mainly bears circumferential force to generate cracks, only the stress condition per unit area of the cross section of the pitch bearing needs to be considered, that is, the thickness, the width and the radian of the pitch bearing have little influence on the detection result of the crack resolution, so the target sample 1 to be tested can be manufactured into a rectangular parallelepiped shape, and the target sample 1 to be tested is made of the same material as the pitch bearing. The tested target sample 1 comprises a prefabricated crack 2, and the prefabricated crack 2 refers to that a crack is prefabricated on the tested target sample 1. In general, the pre-crack 2 is obtained by wire-cutting the target sample 1, and the pre-crack 2 is formed along the width direction of the target sample 1 and penetrates one side edge of the target sample 1. The smaller the width of the pre-crack 2 is, the better, the width of the pre-crack 2 may be 0.5mm or less according to the current machining accuracy, the length of the pre-crack 2 may be 1/10 to 1/2 of the width of the target specimen 1 to be measured, and the purpose of the pre-crack 2 is to control the extending direction or the strike of the crack.
Alternatively, the target specimen 1 to be tested prepared according to the crack resolution detection method of the exemplary embodiment of the present invention may further include a crack stopper hole 3 formed in the target specimen 1 to be tested along the extending direction of the pre-crack 2. The crack stopper hole 3 is separated from one end (right end in fig. 1) of the pre-crack 2 by a predetermined distance, and the crack stopper hole 3 is formed to prevent the pre-crack 2 from being propagated too fast to measure the resolution of the sensing layer 4 (described in detail below). The diameter of the crack stopper 3 may be between 5mm and 10mm, but the diameter of the crack stopper 3 is not limited thereto as long as the size of the crack stopper can prevent the prefabricated crack 2 from expanding too fast to measure the resolution of the sensing layer 4 and not affect the strength of the tested target sample 1, the sensing layer 4 may be tinfoil or conductive paint, the material of the sensing layer 4 is not limited thereto, and the sensing layer 4 may be formed by other suitable materials.
Although fig. 1 shows that the target sample 1 is rectangular parallelepiped, the present invention is not limited to this, and the target sample 1 may have other suitable shapes. Although fig. 1 shows that the pre-crack 2 is formed along the width direction of the target specimen 1 and penetrates one side edge of the target specimen 1, the pre-crack 2 may not be formed along the width direction of the target specimen 1, and may not penetrate the edge of the target specimen 1 (that is, the pre-crack 2 may be formed in the middle of the target specimen 1 by another machining method).
The first step of the crack resolution detection method according to the exemplary embodiment of the present invention, i.e., the preparation of the target specimen under test 1 including the pre-fabricated crack 2, is described above, and the other steps of the crack resolution detection method according to the exemplary embodiment of the present invention are described below with reference to fig. 2 and 3. Fig. 2 is a schematic diagram of a crack resolution detection method according to an exemplary embodiment of the present invention, in which a sensing layer 4 is fixed on a target specimen 1 to be measured; fig. 3 is a schematic diagram of the loading of the test target specimen 1 according to the crack resolution detection method of the exemplary embodiment of the present invention.
As shown in fig. 2 and 3, the crack resolution detection method according to the exemplary embodiment of the present invention is performed according to the following steps:
and secondly, mounting a sensing layer 4 on the tested target sample 1.
Specifically, the sensing layer 4 is fixed on the test object specimen 1 in a direction crossing the extending direction of the pre-crack 2, and the sensing layer 4 is separated from the pre-crack 2 by a predetermined distance so that the sensing layer 4 is located between the pre-crack 2 and the crack stopper hole 3. Preferably, the sensing layer 4 is fixed on the target test specimen 1 along the length direction of the target test specimen 1, i.e., the extending direction of the pre-crack 2 is perpendicular to the fixing direction of the sensing layer 4. The schematic view of the sensing layer 4 fixed on the target sample 1 to be measured is shown in FIG. 2.
According to experiments performed in a laboratory, the main factors affecting the resolution of the sensing layer 4 are the material of the sensing layer 4, the fixing method of the sensing layer 4, the width of the sensing layer 4 and the thickness of the sensing layer 4. In general, the more brittle the material of the sensing layer 4, the higher the resolution (the finer the cracks that can be resolved); the better the fixing effect of the adhesive for fixing the sensing layer 4 on the test object sample 1, the higher the resolution. Alternatively, the width of the sensing layer 4 may be between 1mm and 5mm, the width of the sensing layer 4 is too narrow to be easily broken, and the width of the sensing layer 4 is too wide to be well resolved. Alternatively, the thickness of the sensing layer 4 may be between 0.1mm and 0.5mm, the thickness of the sensing layer 4 is too thick and the resolution is low, and the thickness of the sensing layer 4 is too thin and easily broken.
And thirdly, mounting the tested target sample 1 on the test equipment.
The upper and lower ends of the test object sample 1 are mounted on upper and lower jigs of a test apparatus such as a fatigue tester, an electronic universal tester, or the like.
And fourthly, connecting two ends of the sensing layer 4 to a sensing layer on-off detector 5.
Specifically, as shown in fig. 3, sensing layer on-off detectors 5 are connected to both ends of the sensing layer 4 to connect a portion of the sensing layer 4 where cracks may occur in a circuit, and the sensing layer on-off detectors 5 may be a high-performance multimeter or the like as long as the device can sensitively monitor the resistance of the sensing layer 4.
And fifthly, loading the tested target sample 1.
Specifically, after the target sample 1 is mounted, the target sample 1 is slowly elongated by applying a load to the target sample 1 at a predetermined speed in a direction intersecting the extending direction of the pre-crack 2 with the displacement of, for example, an electronic universal tester set to zero. Preferably, the direction of loading of the test object specimen 1 is perpendicular to the direction of propagation of the pre-crack 2. The loading speed of the electronic universal testing machine can be estimated according to the property and the loading condition of the material of the tested target object, such as a pitch bearing, and can be between 0.01mm/min and 0.1mm/min, and preferably, the loading speed can be 0.05 mm/min.
And sixthly, monitoring the fracture of the sensing layer 4.
With the slow elongation of the tested target sample 1, the preformed crack 2 will expand and penetrate the sensing layer 4, and when the crack width penetrating the sensing layer 4 expands to a certain extent and breaks, the sensing layer on-off detector 5 can detect the sudden change of the resistance (for example, the set threshold is 10)6Ohm), i.e. a sharp rise, at which point it is necessary to immediately stop the loading (stretching), reduce the loading (stretching) speed to zero, and keep the load constant.
Seventh step, determining resolution
Specifically, the displacement recorded by the electronic universal tester when the sensing layer 4 is monitored for fracture is recorded, i.e. the resolution of the sensing layer 4. A microscope and a scale may be used to further determine resolution if necessary. Alternatively, the resolution of the sensing layer 4 may be sensed by a sensor.
Eighth step: unloading
After the resolution detection of the sensing layer 4 is completed, the displacement of the electronic universal testing machine is reset to zero, then the tested target sample 1 is taken down from the electronic universal testing machine, and the fracture condition is further observed.
The size of the target specimen 1 to be tested prepared by the crack resolution detection method according to the exemplary embodiment of the present invention is determined by the test apparatus, that is, the size of the target specimen 1 to be tested is determined according to the maximum and minimum distances between the clamps of the electronic universal tester.
Two examples of the resolution of the sensing layer (i.e., the material and shape of the target sample to be measured to which the sensing layer is fixed are the same; the material, size, and operating temperature of the sensing layer are also the same; and only the fixing manner of the sensing layer is different) under different test conditions detected by the crack resolution detection method according to the embodiment of the invention are described below.
The method comprises the steps of adopting a tested target sample 1 shown in the figure 3, installing a sensing layer between a prefabricated crack 2 and a crack stopping hole 3, adopting a high-precision resistance instrument to monitor the connection and disconnection of the sensing layer, adopting an Instron 8802 fatigue testing machine to stretch the tested target sample 1 at the speed of 0.05mm/min, calculating the width of the crack by using stretching displacement or recording the width of the crack by using microscope observation when the sensing layer is monitored to be broken by the high-precision resistance instrument, and obtaining the test results shown in the table 1.
TABLE 1
| Test of | Resolution of test one | Resolution of test two |
| Sample No. 1 | 0.041mm | 0.053mm |
| Sample No. 2 | 0.042mm | 0.051mm |
| Sample No. 3 | 0.042mm | 0.052mm |
| Mean value | 0.042mm | 0.052mm |
From the above table 1, it can be known that the resolutions of the sensing layers obtained by the crack resolution detection method according to the embodiment of the present invention are different under different test conditions, and the result precision, the reproducibility and the data reliability are high when the test conditions are optimal.
The crack resolution detection method according to the exemplary embodiment of the present invention has the following advantages: as a result of the laboratory experiments, the resolution of the sensing layer can be determined quickly (e.g., 10 minutes) by setting the appropriate loading load; because the test conditions of the laboratory can be accurately controlled, the test result has high precision, good reproducibility and high data reliability; because the test is carried out in a laboratory, the related test equipment and various preparations are easy to carry out, and the test is convenient; the resolution of the sensing layer can be compared quickly for different materials, different fixation processes, different shapes and different temperatures.
In addition, according to the crack resolution detection method of the exemplary embodiment of the invention, since the pre-fabricated crack and the crack arrest hole are arranged on the tested target sample, the crack trend and the crack propagation time can be controlled, and the dynamic propagation of the crack is promoted by adopting tensile loading, the resolution of the sensing layer with different parameters can be determined quickly and effectively, so that the structure and the process of the sensing layer material, the process of fixing the sensing layer, the shape and the size of the sensing layer and the like can be optimized.
Although exemplary embodiments of the present invention have been described above in detail, it will be understood by those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the principles and spirit of the invention. It will be understood that modifications and variations such as would occur to those skilled in the art are intended to be included within the scope of the invention as defined in the following claims.
Claims (11)
1. A crack resolution detection method for a pitch bearing, the method comprising:
preparing a tested target sample (1) comprising a prefabricated crack (2);
forming a crack arrest hole (3) in the tested target sample (1) along the extension direction of the pre-crack (2);
fixing a sensing layer (4) on the tested target specimen (1) through adhesive glue along a direction crossing the extending direction of the prefabricated crack (2) so that the sensing layer (4) is positioned between the prefabricated crack (2) and the crack arrest hole (3) and is separated from the prefabricated crack (2) by a preset distance; mounting the target specimen (1) to be tested on a test device;
connecting two ends of the sensing layer (4) to a sensing layer on-off detector (5);
loading the tested target sample (1) along a direction crossed with the extending direction of the pre-crack (2);
when the sensing layer on-off detector (5) monitors the resistance mutation, the loading speed is reduced to zero;
determining a resolution of the perception layer (4);
detaching the target sample (1) from the test device,
wherein the crack resolution is a minimum crack width detectable by on-off crack monitoring.
2. The crack resolution detection method for the pitch bearing according to claim 1, characterized in that the loading direction of the tested target specimen (1) is perpendicular to the extending direction of the pre-crack (2).
3. The crack resolution detection method for a pitch bearing according to claim 2, characterized in that the pre-fabricated crack (2) extends in a direction perpendicular to the fixed direction of the sensing layer (4).
4. The crack resolution detection method for the pitch bearing according to claim 3, wherein the tested target sample (1) is approximately rectangular parallelepiped, and the pre-crack (2) is formed along the width direction of the tested target sample (1) and penetrates through one side edge of the tested target sample (1).
5. The crack resolution detection method for the pitch bearing according to claim 4, characterized in that the length of the pre-crack (2) is 1/10-1/2 of the width of the tested target specimen (1).
6. The method for detecting the crack resolution of the pitch bearing according to claim 1, wherein the loading speed of the test equipment is between 0.01mm/min and 0.1 mm/min.
7. The crack resolution detection method for the pitch bearing according to claim 1, characterized in that the width of the pre-fabricated crack (2) is less than or equal to 0.5 mm.
8. The crack resolution detection method for the pitch bearing according to claim 1, characterized in that the diameter of the crack arrest hole (3) is between 5mm and 10 mm.
9. The crack resolution detection method for the pitch bearing according to claim 1, characterized in that the size of the target specimen (1) to be tested is determined by the testing equipment.
10. The crack resolution detection method for a pitch bearing according to claim 8, characterized in that the width of the sensing layer (4) is between 1mm and 5 mm.
11. The crack resolution detection method for a pitch bearing according to claim 10, characterized in that the thickness of the sensing layer (4) is between 0.1mm and 0.5 mm.
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