CN119164801A - A method for enhancing the contrast of fatigue microcracks in metal materials - Google Patents
A method for enhancing the contrast of fatigue microcracks in metal materials Download PDFInfo
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- CN119164801A CN119164801A CN202411220215.4A CN202411220215A CN119164801A CN 119164801 A CN119164801 A CN 119164801A CN 202411220215 A CN202411220215 A CN 202411220215A CN 119164801 A CN119164801 A CN 119164801A
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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
- G01N3/32—Investigating strength properties of solid materials by application of mechanical stress by applying repeated or pulsating forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/91—Investigating the presence of flaws or contamination using penetration of dyes, e.g. fluorescent ink
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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
- G01N3/02—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
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- 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
- G01N2203/0005—Repeated or cyclic
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- 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
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0073—Fatigue
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- 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
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- 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
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0682—Spatial dimension, e.g. length, area, angle
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- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
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- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
- Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
Abstract
本发明提供一种增强金属材料疲劳微裂纹显示对比度方法，该方法包括如下步骤：步骤1、试样准备；步骤2、表面处理；步骤3、疲劳试验。本发明针对疲劳裂纹扩展速率试验提出一种有效增强金属材料疲劳微裂纹显示对比度方法。在现有疲劳微裂纹的测量方法中，绝大多数采用高清显微镜/摄像机的技术方案，依靠目视观察从材料表面寻找裂纹，由于材料表面一般存在表面加工纹理或者划痕，受到上述影响易导致判断裂纹困难和费时费力的技术缺陷，甚至产生误判。The present invention provides a method for enhancing the contrast of fatigue microcracks in metal materials, and the method comprises the following steps: step 1, sample preparation; step 2, surface treatment; step 3, fatigue test. The present invention proposes a method for effectively enhancing the contrast of fatigue microcracks in metal materials for fatigue crack growth rate test. In the existing fatigue microcrack measurement methods, most of them adopt the technical solution of high-definition microscope/camera, and rely on visual observation to find cracks from the surface of the material. Since the surface of the material generally has surface processing textures or scratches, the above-mentioned influence can easily lead to technical defects such as difficulty in judging cracks and time-consuming and labor-intensive, and even misjudgment.
Description
Technical Field
The invention relates to the technical field of metal material fatigue performance detection, in particular to a method for enhancing the display contrast of fatigue microcracks of a metal material.
Background
The fatigue crack propagation rate test is a test mode for researching the fatigue fracture characteristics of a material by measuring the length of a fatigue crack generated by a sample under the set alternating load in real time. When the fatigue crack growth rate test is performed, in order to ensure the accuracy of the calculation result, it is necessary to precisely measure the crack length during the fatigue crack growth. In the indirect measurement method, the compliance method and the potential method are based on the variation of other physical parameters caused by crack growth, and the average size of crack growth, the range delta K of crack intensity factors and the crack growth rate are obtained through indirect calculation, but the two operation procedures are relatively complex, so that the method is suitable for high-temperature environment tests, and meanwhile, too many variables are introduced during measurement and are sensitive to the crack length and during calculation, so that larger deviation is generated between a calculated value and a true value. In the direct measurement method, a high-definition microscope/camera is adopted to directly read an image scale by visual inspection to obtain the crack propagation size, the operation procedure is simple and convenient, a large number of applications are obtained in room temperature environment test, but the surface of the metal material is generally provided with surface processing textures or scratches, at the moment, the crack morphology is similar to the textures and scratches, the technical defects of difficult crack identification, time and labor waste are often caused, and sometimes even misjudgment is generated. Therefore, there is a need for a method of enhancing fatigue microcrack display contrast to avoid the effects of surface texture or scratches and meet the needs of laboratory accurate measurements.
In the aspect of fatigue crack tracking and monitoring, a part of patents have adopted related technical means to achieve the above-mentioned aim. Patent CN104181225 describes a fatigue crack tracking and monitoring device and monitoring method for steel bridge deck slab, the method sprays contrast enhancer and black water magnetic suspension on the monitored steel bridge deck slab, the magnetic powder flaw detection method is adopted to display the shape and position of the fatigue crack, patent 108760546 describes a fatigue crack propagation rate measuring method based on infrared thermal imaging technology, the method sprays black matt paint on a sample meeting the required geometric dimension and surface roughness, the purpose is to improve the emissivity of the sample surface, the method is suitable for the infrared thermal imaging method to record the temperature field evolution process of the fatigue crack tip area in real time and automatically identify the crack tip position, patent CN110295340 describes a crack monitoring sensor based on plasma spraying, the preparation and monitoring method thereof, the method adopts plasma spraying to integrate an insulating substrate layer, a damage sensor and a packaging protection layer on the surface of a target monitoring structure, the crack length of the detection structure is determined by measuring the potential difference of the two ends of the crack surface of the monitoring structure, and patent CN110926972 describes a micro fatigue surface detecting method and system, the method adopts binary silicon rubber to mutually contact the contact part and the crack contact part is determined by observing the contact part of the film. In summary, the above patent uses related technical means and a matched detection method to improve the crack display contrast, so as to accurately measure the crack size.
Disclosure of Invention
The invention aims to provide a method for enhancing the fatigue microcrack display contrast of a metal material so as to solve the technical problems.
The technical scheme of the invention is as follows:
a method for enhancing fatigue microcrack display contrast of a metal material is provided, which comprises the following steps:
Step 1, sample preparation
Machining the plate-shaped sample to form a crack, and determining that the tip of the crack meets the test requirement
Polishing and burnishing the surface of the plate-shaped sample to ensure that the surface roughness meets the fatigue crack growth rate test requirement;
Step 2, surface treatment
And spraying black light-absorbing paint on the surface of the sample to be tested to form a uniform black light-absorbing coating so as to absorb visible light emitted by the light source and realize a strong light-absorbing effect.
Step 3, fatigue test
Mounting a sample on a fatigue testing machine by adopting a clamp matched with the sample, adjusting a light source to a corresponding position, and adjusting the focal length of a lens of a high-definition camera until the crack tip outline is clearly observed;
and 4, performing fatigue crack growth rate test on the sample.
Further, the light absorbing coating is a strong light absorbing coating.
Further, the machined crack is located in the middle of the plate-like specimen.
Further, the lapping and polishing is oriented in a direction perpendicular to the crack propagation path.
Further, the thickness of the black light absorption coating is 10-20 mu m. When the crack is not expanded, the strong light absorption coating absorbs visible light or ultraviolet rays emitted by a strong light source, and the image shows a black background.
Further, the light absorbing coating is provided with a fluorescent agent, and the light source is ultraviolet light
When the crack propagates, the strong light absorption coating tears along with the crack, and visible light generates diffuse reflection at the crack and is captured by the high-definition camera, so that a bright line which is strongly contrasted with the background and is overlapped with the crack is formed.
Further, the light source is a strong light source.
Further, the light source is a direct or oblique light sample surface.
The method has the advantage that the method is used for effectively enhancing the fatigue microcrack display contrast of the metal material aiming at the fatigue crack propagation rate test. In the existing fatigue microcrack measuring method, most of the technical schemes of a high-definition microscope/camera are adopted, the cracks are found from the surface of the material by means of visual observation, and as the surface of the material is generally provided with surface processing textures or scratches, the technical defects of difficult crack judgment, time and labor waste and even misjudgment are caused due to the influence. The method adopts a method of spraying a thin and uniform black strong light absorption coating or a fluorescent agent coating and the black strong light absorption coating on the surface of a material, when a crack is expanded, the coating tears along with the crack, a bright line which is strongly contrasted with the background and overlapped with the crack position is generated through a strong light source, the crack position and the crack size are judged according to the bright line, and the measurement precision is improved to accurately obtain the crack expansion rate data.
Detailed Description
Indeed, many different examples may be described and should not be construed as limited to the examples set forth herein. Rather, these examples are described so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
A method for enhancing fatigue microcrack display contrast of a metal material is provided, which comprises the following steps:
Step 1, sample preparation
Machining the plate-shaped sample to form a crack, and determining that the tip of the crack meets the test requirement
Polishing and burnishing the surface of the plate-shaped sample to ensure that the surface roughness meets the fatigue crack growth rate test requirement;
Step 2, surface treatment
And spraying black light-absorbing paint on the surface of the sample to be tested to form a uniform black light-absorbing coating so as to absorb visible light emitted by the light source and realize a strong light-absorbing effect.
Step 3, fatigue test
Mounting a sample on a fatigue testing machine by adopting a clamp matched with the sample, adjusting a light source to a corresponding position, and adjusting the focal length of a lens of a high-definition camera until the crack tip outline is clearly observed;
and 4, performing fatigue crack growth rate test on the sample.
The light absorbing coating is a strong light absorbing coating.
The machined crack is located in the middle of the plate-like specimen.
The lapping and polishing is oriented in a direction perpendicular to the crack propagation path.
The thickness of the black light absorption coating is 10-20 mu m. When the crack is not expanded, the strong light absorption coating absorbs visible light or ultraviolet rays emitted by a strong light source, and the image shows a black background.
The light absorbing coating is provided with a fluorescent agent, and the light source is ultraviolet light
When the crack propagates, the strong light absorption coating tears along with the crack, and visible light generates diffuse reflection at the crack and is captured by the high-definition camera, so that a bright line which is strongly contrasted with the background and is overlapped with the crack is formed.
The light source is a strong light source.
The light source is directly or obliquely irradiated to the surface of the sample.
The following parameters of embodiment one may also be preferred:
Before the fatigue crack growth rate test was conducted by the method of this example, 7075 aluminum alloy was processed according to ASTM647 into a plate-like specimen having a length of 300.04mm, a width of 100.06mm, and a thickness of 4.76mm, and an artificial crack having a kerf radius of 3.06mm was processed at the center of the specimen.
The surface roughness Ra of the sample is less than 1.6 mu m;
and (3) mounting the test sample on the fatigue testing machine by adopting a proper clamp, adjusting a strong light source to a proper position, and adjusting the focal length of a lens of the high-definition camera until the tip outline of the artificial crack is clearly observed in the acquired image, wherein the rest background except the artificial crack is black.
The fatigue loading adopts stress ratio R=0.1, the pre-cracking process adopts a load-reducing mode, the pre-cracking process is ended when the pre-cracking size is set to be 3mm, when the cyclic loading crack is expanded, the strong light absorption coating can be torn along with the expansion of the crack tip, at the moment, the visible light generated by the strong light source generates diffuse reflection at the crack and is captured by the high-definition camera, a bright line which is strong in contrast with the background and overlapped with the crack is formed, and the crack expansion size is monitored and measured in real time after the image is acquired by the high-definition camera. And after prefabricating the crack, adopting a banner load loading mode, adopting the same method to monitor and measure the crack expansion size, and calculating the crack expansion rate in real time.
The parameters of the second embodiment can also be optimized
Before the fatigue crack growth rate test was conducted by the method of this example, a TC4 titanium alloy was processed according to ASTM647 into a plate-like specimen having a length of 300.14mm, a width of 100.16mm, and a thickness of 4.74mm, and an artificial crack having a kerf radius of 3.02mm was machined in the center of the specimen.
The surface roughness Ra of the sample is less than 1.6 mu m;
and (3) mounting the test sample on the fatigue testing machine by adopting a proper clamp, adjusting a strong light source to a proper position, and adjusting the focal length of a lens of the high-definition camera until the tip outline of the artificial crack is clearly observed in the acquired image, wherein the rest background except the artificial crack is black.
The fatigue loading adopts stress ratio R=0.1, the pre-cracking process is finished when the pre-cracking size is set to be 3mm in a load-reducing mode, when the cyclic loading crack is expanded, the fluorescent agent coating and the strong light absorption coating are torn along with the expansion of the crack tip, ultraviolet rays generated by a strong light source generate fluorescence at the crack to form a bright line which is strongly contrasted with the background and overlapped with the crack, and the crack expansion size is monitored and measured in real time after the image is acquired by a high-definition camera. And after prefabricating the crack, adopting a banner load loading mode, adopting the same method to monitor and measure the crack expansion size, and calculating the crack expansion rate in real time.
The description of the different advantageous arrangements has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the examples in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Additionally, the different advantageous examples may describe different advantages compared to other advantageous examples. The example or examples selected are chosen and described in order to best explain the principles of the examples, the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various examples with various modifications as are suited to the particular use contemplated.
Claims (8)
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN120747058A (en) * | 2025-08-26 | 2025-10-03 | 陕西东昊电力工程有限公司 | Real-time monitoring method for substation equipment state |
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Cited By (1)
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| CN120747058A (en) * | 2025-08-26 | 2025-10-03 | 陕西东昊电力工程有限公司 | Real-time monitoring method for substation equipment state |
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