Mu-DIC speckle preparation method based on oxide film corrosion perforation

Abstract

The invention discloses a mu-DIC speckle preparation method based on oxide film corrosion perforation, which comprises the following steps: polishing the surface of a metal sample to a mirror surface; the polished metal sample is exposed in the atmospheric environment, heat preservation treatment is conducted, and an oxidation film is generated on the surface of the metal sample; carrying out corrosion treatment on the metal sample by adopting chemical corrosion liquid, and forming a through hole in the oxidation film of the metal sample; the corrosion time is prolonged until the oxidation film is completely removed, and punctiform corrosion pits are left in the surface of the metal sample; and the surface of the metal sample is cleaned, and the speckle sample with the punctiform corrosion pits as marks is obtained. According to the method, the punctiform corrosion pits are directly formed in the surface of the metal sample in an oxidation film perforation mode, the punctiform corrosion pits can stably exist under the static load and dynamic load conditions, the punctiform corrosion pits are evenly distributed and small in size, and the method can be used for deformation detection of fine grains.

Description

Technical Field

[0001] This invention relates to the field of deformation detection technology, and more specifically to a method for preparing μ-DIC speckle patterns based on oxide film corrosion perforation. Background Technology

[0002] Digital image correlation (DIC) technology can detect displacement and strain distribution on the surface of an object by tracking the positional changes of speckle, and is widely used in the characterization of plastic deformation and the study of damage behavior of metallic materials. Micro-DIC (μ-DIC) technology usually uses optical microscopy or scanning electron microscopy to detect micro-strain at the micrometer scale, which places extremely high demands on speckle quality: the speckle size is small (submicrometer level) and uniformly distributed, with high contrast compared to the substrate.

[0003] Invention patent CN111610210B discloses a method for preparing speckle patterns using a silica suspension. The nanoparticles deposited on the substrate are uniformly distributed and have high contrast, exhibiting good strain identification efficiency under static tensile load. However, the speckle particles obtained by this method have insufficient adhesion and are prone to detachment under fatigue dynamic load, leading to the loss of displacement information. Invention patent CN101832759B discloses a method for preparing speckle patterns using focused ion beam etching. Although this solves the problem of speckle detachment, it damages the substrate surface structure, making it prone to inducing fatigue crack initiation under fatigue load. Invention patent CN118225593A uses a chemical etching solution to directly act on the material substrate to form corrosion pit speckle patterns. Although this solves the problems of speckle detachment and damage to the material surface structure, the prepared speckle diameter is relatively large (0.3μm≤φ≤2μm) and the size uniformity is insufficient, making it only suitable for deformation detection of coarse grains (approximately 50μm~100μm in size).

[0004] Therefore, developing a method for preparing μ-DIC speckle patterns that is not easily detached and can be used for detecting fine grain deformation is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing μ-DIC speckle based on oxide film corrosion perforation, which is not easy to detach and can be used for fine grain deformation detection.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing μ-DIC speckle patterns based on oxide film corrosion perforation, characterized by comprising the following steps:

[0008] S1, Polish the surface of the metal sample until it reaches a mirror finish;

[0009] S2, expose the polished metal sample to the atmosphere and perform heat preservation treatment to generate an oxide film on the surface of the metal sample;

[0010] S3, using a chemical etching solution to etch the metal sample and form perforations in the oxide film of the metal sample;

[0011] S4, extend the corrosion time until the oxide film is completely removed and pitted corrosion pits are left on the surface of the metal sample; clean the surface of the metal sample to obtain a speckled metal sample marked with pitted corrosion pits.

[0012] The beneficial effects of adopting the above technical solution are that, by perforating the oxide film, pitted corrosion pits are formed on the surface of the metal sample, which can remain stable and not fall off under both static and dynamic loads; and the pitted corrosion pits formed in this way are evenly distributed and have a small diameter, which can be used for deformation detection of fine grains.

[0013] Preferably, the surface roughness Ra of the metal sample after polishing in step S1 is ≤0.025μm.

[0014] Preferably, the temperature of the heat treatment in step S2 is controlled between 50℃ and 300℃, and is lower than the annealing temperature of the metal sample. The heat treatment temperature is lower than the annealing temperature of the metal sample to ensure that the initial microstructure of the metal sample will not change at this temperature. After the heat treatment, the surface of the metal sample still retains its metallic luster.

[0015] Preferably, the heat preservation treatment time in step S2 is 5h-30h.

[0016] Preferably, the chemical etching solution in step S3 is an acidic solution with a volume percentage of 1%-10%.

[0017] Preferably, the corrosion treatment in step S3 is carried out by applying corrosion droplets to the surface of the metal sample or immersing the metal sample in the corrosion solution.

[0018] Preferably, the oxide film removal process in step S4 is achieved by visually observing the generation of bubbles. If bubbles are generated, it indicates that the metal sample substrate is in contact with the corrosive solution and the oxide film has been removed.

[0019] Preferably, the removal of the oxide film in step S4 is determined by observation using a scanning electron microscope.

[0020] Preferably, the reagents used to clean the metal sample in step S4 are deionized water and anhydrous ethanol.

[0021] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a method for preparing μ-DIC speckle patterns based on oxide film corrosion perforation, the beneficial effects of which are:

[0022] (1) Compared with methods such as spraying, particle deposition and other methods of adding foreign matter to prepare speckles, the present invention directly forms pitted corrosion pits on the surface of metal samples, which can exist stably under static and dynamic load conditions, effectively solving the problem of speckle detachment.

[0023] (2) Compared with the method of preparing speckle by laser or ion beam etching, the pitted corrosion pit will not damage the surface structure of the metal sample, thus avoiding stress concentration and crack initiation.

[0024] (3) The size of the pitted corrosion pits is submicron, which can be used for deformation detection of fine grains and will not cover the original microstructure characteristics of the material. It can simultaneously observe μ-DIC plastic deformation and microstructure changes.

[0025] (4) The method of the present invention can prepare μ-DIC speckle on plane and curved surfaces. It is simple to operate and low in cost. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the μ-DIC speckle preparation process in Example 1 of the present invention;

[0028] Figure 2 This is a diagram of the oxide film on the surface of the titanium alloy in Example 2 of the present invention;

[0029] Figure 3 The perforation diagram of the titanium alloy oxide film in Example 2 provided by the present invention;

[0030] Figure 4 The speckle quality diagram of the titanium alloy μ-DIC in Example 2 provided by the present invention;

[0031] Figure 5A The μ-DIC strain contour plot before fatigue loading in Example 2 of this invention;

[0032] Figure 5B The strain cloud diagram of μ-DIC after fatigue loading in Example 2 of the present invention.

[0033] In the figure,

[0034] 1-Metal sample; 2-Oxide film; 3-Perforation; 4-Corrosion pit. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1:

[0037] This invention discloses a method for preparing μ-DIC speckle patterns based on oxide film corrosion perforation, such as... Figure 1 As shown, it includes the following steps:

[0038] S1. Grind the surface of metal sample 1 with 200#-3000# SiC sandpaper, and then polish the surface of metal sample 1 to a mirror finish with diamond polishing paste or SiO2 suspension. After polishing, the surface roughness Ra of metal sample 1 is ≤0.025μm.

[0039] S2, place the metal sample 1 in a muffle furnace for heat treatment to generate an oxide film 2 on the surface of the metal sample 1. The heat treatment temperature is lower than the annealing temperature of the metal material. The heat treatment temperature is controlled within the range of 50℃ to 300℃ and the heat treatment time is controlled within the range of 5h to 30h.

[0040] S3, after taking out the metal sample 1 and air cooling it, prepare an acidic solution with a volume fraction of 1% to 10%, drip the corrosion solution onto the surface of the metal sample 1 or immerse the metal sample 1 in the corrosion solution for corrosion treatment, and form a perforation 3 on the oxide film 2.

[0041] S4, extend the corrosion time until the oxide film 2 is completely removed, leaving pitted corrosion pits 4 on the surface of the metal sample 1; clean the surface of the metal sample 1 with deionized water and anhydrous ethanol, dry it with a hair dryer, and examine the size and distribution of the pitted corrosion pits 4 under a scanning electron microscope to obtain μ-DIC speckled sample marked with pitted corrosion pits 4.

[0042] To further optimize the above technical solution, the removal process of oxide film 2 in step S4 is carried out by visually observing the generation of bubbles. If bubbles are generated, it indicates that the metal sample 1 is in contact with the corrosive liquid and the oxide film 2 is removed.

[0043] To further optimize the above technical solution, the removal status of oxide film 2 in step S4 is determined by scanning electron microscopy. If it is not completely removed, corrosion should continue for a period of time, and then the oxide film 2 should be observed again using scanning electron microscopy until it is completely removed.

[0044] To further optimize the above technical solution, after corrosion is completed, the pitted corrosion pits 4 on the surface of the metal sample 1 are evenly distributed and the diameter φ≤0.3μm.

[0045] Example 2:

[0046] The process of preparing μ-DIC speckle patterns on the surface of a titanium alloy specimen to be tested for fatigue is as follows:

[0047] S1, the surface of the titanium alloy sample was ground with SiC sandpaper of 200# to 3000# and then polished to a mirror finish with SiO2 suspension, with a surface roughness of Ra0.01μm.

[0048] S2, place metal sample 1 in a muffle furnace, control the furnace temperature at 100℃~200℃, and hold for 5h~20h. After removal and air cooling, the morphology of oxide film 2 on the surface of metal sample 1 is as follows. Figure 2 As shown;

[0049] S3, prepare a chemical etching solution with the following composition and volume ratio: hydrofluoric acid: nitric acid: water = 1:2:100. Add the etching solution to the region of interest of metal sample 1. After etching for 5-15 seconds, perforation of the oxide film occurs, as shown in the image. Figure 3 As shown;

[0050] S4, extend the corrosion time to 20s-40s. At this time, bubbles are generated on the surface of the metal sample under visual inspection, and the oxide film 2 is completely removed as observed under a scanning electron microscope. Clean the surface of metal sample 1 with deionized water and anhydrous ethanol, dry it with a hair dryer, and then examine the morphology of the pitting corrosion pits 4 under a scanning electron microscope to obtain the following results: Figure 4 The μ-DIC speckle sample shown has a speckle diameter φ ≤ 0.3 μm and is uniform in size.

[0051] To verify the application effect of μ-DIC speckle with pitting corrosion, fatigue loads were applied to the above-mentioned titanium alloy specimens, and the micro-deformation was calculated using VIC-2D 7.0 data processing software. The specific process is as follows:

[0052] (1) Under a scanning electron microscope, record the initial microscopic image of the region of interest, 5A, at a magnification of 2000 times;

[0053] (2) The fatigue metal specimen is clamped on the fatigue testing machine, the fatigue load is set to 600MPa, the cycle is 100,000, and the fatigue metal specimen is removed after the fatigue loading is completed.

[0054] (3) Place the fatigued metal sample under a scanning electron microscope again to observe the same area at a magnification of 2000 times to obtain a microscopic image 5B after fatigue loading;

[0055] (4) Using VIC-2D 7.0 data processing software, microscopic images 5A and 5B were compared and analyzed to calculate the micro-strain distribution after fatigue loading; Appendix Figure 5A and 5B The comparison shows that the μ-DIC speckle of corrosion pits has good micro-strain identification ability.

[0056] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0057] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for speckle preparation for μ-DIC based on oxidation film corrosion perforation, characterized in that, The method comprises the following steps: S1, polishing the surface of the metal sample, and polishing to a mirror surface; S2, exposing the polished metal sample to an atmospheric environment and performing heat preservation treatment to form an oxide film on the surface of the metal sample; S3, performing etching treatment on the metal sample using a chemical etching solution to form perforations on the oxide film of the metal sample; S4, extending the etching time until the oxide film is completely removed and point-like etching pits are left on the surface of the metal sample; and cleaning the surface of the metal sample to obtain a speckle sample marked with point-like etching pits.

2. The method for speckle preparation of μ-DIC based on oxide film corrosion perforation according to claim 1, characterized in that, The surface roughness Ra of the metal sample after polishing in step S1 is less than or equal to 0.025 μm.

3. The method of claim 1, wherein the method is a method of preparing a μ-DIC speckle based on an oxide film corrosion perforation. The temperature of the heat preservation treatment in step S2 is controlled to be between 50°C and 300°C, and is lower than the annealing temperature of the metal sample.

4. The method of claim 3, wherein the method is a method of preparing a speckle for μ-DIC based on an oxide film corrosion perforation. The time of the heat preservation treatment in step S2 is 5h-30h.

5. The method of claim 1, wherein the method is a method of preparing a μ-DIC speckle based on an oxide film corrosion perforation. The chemical etching solution in step S3 is an acid solution with a volume ratio of 1%-10%.

6. The method of claim 5, wherein the method is a method of preparing a speckle for μ-DIC based on an oxide film corrosion perforation. The etching treatment in step S3 adopts an etching mode in which the etching solution is dropped on the surface of the metal sample or the metal sample is immersed in the etching solution.

7. The method of claim 1, wherein the method is a method of preparing a speckle for μ-DIC based on an oxide film corrosion perforation. In step S4, the removal of the oxide film is observed by visual observation of the generation of bubbles. If bubbles are generated, it indicates that the metal sample substrate is in contact with the etching solution, and the oxide film is removed.

8. The method of claim 7, wherein the method is a method of preparing a speckle for μ-DIC based on an oxide film corrosion perforation. The removal of the oxide film in step S4 is observed and determined by a scanning electron microscope.

9. The method of claim 1, wherein the method is a method of preparing a speckle for μ-DIC based on oxide film etching perforation. The reagent used for cleaning the metal sample in step S4 is deionized water and anhydrous ethanol.

Images