CN107036747B - Method for detecting residual stress of solidified spots - Google Patents
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Abstract
The application provides a solidification spot residual stress detection method, which comprises the following steps: providing a coagulated speck test specimen; manufacturing a dot matrix on a region to be measured of a solidification spot test sample; acquiring a first topography image of a region to be measured; removing materials around the area to be measured layer by layer, and acquiring a shape image of the area to be measured after removing each layer of material; obtaining displacement of each point in the dot matrix of the area to be measured after removing each layer of material according to the first topography image and the topography image of the area to be measured after removing each layer of material; and calculating the residual stress of the region to be measured after removing the material of each layer according to the displacement of each point in the lattice. The residual stress of the area to be measured after the peripheral material is removed is calculated, so that the residual stress of different depths in the solidification spot is detected, and the residual stress of the solidification spot is measured.
Description
Technical Field
The invention relates to the technical field of residual stress detection, in particular to a method for detecting residual stress of a solidified spot.
Background
The residual stress is an important influence factor influencing the performance of the plasma spraying coating, such as the bonding strength of the coating, the rolling contact fatigue life and the like, so that the residual stress of the coating needs to be effectively controlled and detected in the coating preparation process. Essentially, thermal spray coatings are formed by the rapid impact of a large number of droplets on a substrate, spread cooling, and layer-by-layer overlapping and stacking, so that a single solidification spot can be considered as the most fundamental unit of coating formation. The magnitude of the residual stress of a single solidification spot can largely determine the magnitude of the residual stress after the coating has been formed.
The appearance of the current solidification spots can be mainly divided into a regular disc shape, a petal shape with irregular and gentle edges, a radiation shape which is sprayed to the periphery along an impact position, a broken type which is scattered into a plurality of small areas and an air bubble shape with air holes in the inner part. No matter what morphology of the solidification spots is, the surface area is very small and the diameter can be generally between 20 and 200 μm, and the residual stress detection method in the prior art has difficulty in realizing accurate measurement of the residual stress of the solidification spots. Therefore, how to accurately detect the residual stress of the solidified spot becomes an urgent problem to be solved.
Disclosure of Invention
In view of the above, the present invention provides a method for detecting residual stress of a solidified spot, so as to solve the problem that the residual stress of the solidified spot cannot be detected in the prior art.
In order to achieve the purpose, the invention provides the following technical scheme:
a solidification spot residual stress detection method comprises the following steps:
providing a coagulated speck test specimen;
manufacturing a dot matrix on a region to be measured of the solidification spot test sample;
acquiring a first topography image of the area to be measured;
removing the materials around the area to be measured layer by layer, and acquiring a shape image of the area to be measured after removing each layer of material;
obtaining displacement of each point in the dot matrix of the area to be measured after removing each layer of material according to the first topography image and the topography image of the area to be measured after removing each layer of material;
and calculating the residual stress of the region to be measured after removing the material of each layer according to the displacement of each point in the lattice.
Preferably, the step of preparing a dot matrix on the region to be measured of the coagulated speckle test sample specifically comprises:
carrying out metal spraying treatment on the surface of the solidification spot test sample;
placing the solidified spot test sample under a field emission scanning electron microscope for observation;
selecting a region to be measured under the field emission scanning electron microscope;
depositing a platinum layer on the surface of the area to be measured;
and forming a plurality of pits on the surface of the platinum layer by adopting focused ion beams to form a dot matrix.
Preferably, the providing of the coagulated spot test specimen specifically comprises:
providing a coagulated speckle sample;
cutting the solidified spot sample into solidified spot sample blocks of 5mm multiplied by 3 mm;
and cleaning the solidified spot sample block to obtain the solidified spot test sample.
Preferably, the removing the material around the region to be measured layer by layer, and the acquiring the topographic image of the region to be measured after removing the material of each layer specifically includes:
removing the ith layer of the material around the area to be measured by using a focused ion beam;
obtaining an i +1 th topographic image of the area to be measured after the material is removed in a secondary electron shooting mode;
wherein i is a positive integer, and i is more than or equal to 1.
Preferably, the obtaining, according to the first topographic image and the topographic image of the area to be measured after removing the material of each layer, displacement amounts of each point in the dot matrix of the area to be measured after removing the material of each layer specifically includes:
calculating displacement of each pit on the second topographic image by using the first topographic image as a reference image and adopting a digital speckle correlation method;
and calculating the displacement of each pit on the (i +1) th morphology image by using the (i) th morphology image as a reference image and adopting a digital speckle correlation method, wherein i is a positive integer and is not less than 1.
Preferably, the platinum layer is circular.
Preferably, the calculating the residual stress of the region to be measured after removing the material of each layer according to the displacement amount of each point in the lattice specifically includes:
and calculating the plane stress of each pit according to the strain distribution of the surface of the area to be measured:
wherein (H) is the strain at which the material is removed to a depth H,
displacement in x and y directions;
calculating to obtain the average residual stress of the region to be measured according to the change condition of the surface stress, wherein the strain relationship between the stresses at different depths and the surface of the material is as follows:
h is the total depth of material removal, H is a variable and represents any position from the surface of the material to the bottom of the circular ring pit, (H) is the strain of the surface when the material is removed to the depth of H, sigma (H) represents the stress when the depth of material removal is H, and A (H, H) reflects the influence degree of the residual stress at the depth H on the strain degree of the surface of the material when the total depth of material removal is H;
and drawing a curve of the residual stress of the area to be measured along with the depth.
Preferably, in the step-by-step removal of the material around the area to be measured, the thickness of the material removed in each step is the same.
According to the technical scheme, the method for detecting the residual stress of the solidified spot comprises the steps of providing a solidified spot test sample; manufacturing a dot matrix on a region to be measured of the solidification spot test sample; acquiring a first topography image of the area to be measured; removing the materials around the area to be measured layer by layer, and acquiring a shape image of the area to be measured after removing each layer of material; obtaining displacement of each point in the dot matrix of the area to be measured after removing each layer of material according to the first topography image and the topography image of the area to be measured after removing each layer of material; and calculating the residual stress of the region to be measured after removing the material of each layer according to the displacement of each point in the lattice. The residual stress of the area to be measured after the peripheral material is removed is calculated, so that the residual stress of different depths in the solidification spot is detected, and the residual stress of the solidification spot is measured.
In addition, the solidification spot residual stress detection method provided by the invention does not need to provide a stress-free sample for comparison, and simplifies the detection process of the residual stress; the method for detecting the residual stress of the solidified spot is not limited by a detected object, the preparation process of the test sample of the solidified spot is simple, the detection position and depth can be accurately controlled, and the residual stress testing precision is higher.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a schematic flow chart of a method for detecting residual stress of a coagulated spot according to an embodiment of the present invention;
FIG. 2 is a schematic flow chart of a manufacturing process of a coagulated speckle test specimen according to an embodiment of the present invention;
fig. 3 is a schematic flow chart illustrating a process of selecting an area to be measured and forming a dot matrix in the area to be measured according to an embodiment of the present invention;
FIG. 4A is a topographical image of a Pt layer formed on a solidified spot according to an embodiment of the present invention;
FIG. 4B is a schematic cross-sectional view of a Pt layer formed on a solidified spot according to an embodiment of the present invention;
fig. 4C is a topographical image of a lattice formed in a region to be measured according to an embodiment of the present invention;
FIG. 4D is a schematic view of a trench formed by removing material around the area to be measured according to an embodiment of the present invention;
fig. 4E is a schematic cross-sectional view illustrating a trench formed by removing material around a region to be measured according to an embodiment of the present invention;
FIG. 5 is a schematic flow chart of another method for detecting residual stress of a coagulated spot according to an embodiment of the present invention.
Detailed Description
In some residual stress detection methods in the prior art, for example, the depth of the residual stress of the material detected by the X-ray and neutron diffraction methods is far greater than 5 μm, and generally, the thickness of the solidified spot is less than 4 μm, so that the influence of the residual stress of the matrix cannot be avoided when the residual stress of the solidified spot is measured by the two methods. Measuring the stress of the solidified spot first requires finding the position to be measured, however, since the solidified spots are randomly distributed on the surface of the substrate, are spaced from each other, and have very small sizes, the process is usually performed under a high power microscope. The existing detection equipment related to the X-ray, neutron diffraction and curvature methods measures the stress on the surface of a homogeneous material, and the solidification spots are difficult to locate. The main testing principle of the curvature method is that the residual stress of the film is calculated by measuring the stress-induced deformation condition of the surface of the film, the solidification spots are usually deposited on a larger substrate, the generated deformation can be almost ignored, and the residual stress is difficult to calculate. Namely, the residual stress detection method in the prior art is not suitable for detecting the residual stress of the solidified spots.
Based on the above, the invention provides a method for detecting residual stress of a solidified spot, which comprises the following steps:
providing a coagulated speck test specimen;
manufacturing a dot matrix on a region to be measured of the solidification spot test sample;
acquiring a first topography image of the area to be measured;
removing the materials around the area to be measured layer by layer, and acquiring a shape image of the area to be measured after removing each layer of material;
obtaining displacement of each point in the dot matrix of the area to be measured after removing each layer of material according to the first topography image and the topography image of the area to be measured after removing each layer of material;
and calculating the residual stress of the region to be measured after removing the material of each layer according to the displacement of each point in the lattice.
According to the solidification spot residual stress detection method provided by the invention, the materials around the area to be measured are removed layer by layer, the residual stress is released, and the residual stress of the area to be measured after the surrounding materials are removed is calculated, so that the detection of the residual stress at different depths in the solidification spot is realized, and the residual stress in the solidification spot is further measured.
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, a schematic flow chart of a method for detecting residual stress of a solidified spot according to an embodiment of the present invention is shown, where the method for detecting residual stress of a solidified spot includes the following steps:
s1: providing a coagulated speck test specimen;
in this embodiment, a specific process for solidifying a spot test sample is provided, as shown in the schematic flow chart shown in fig. 2, and includes:
s11: providing a coagulated speckle sample;
s12: cutting the solidified spot sample into solidified spot sample blocks of 5mm multiplied by 3 mm;
in the embodiment of the present invention, a cutting process for cutting the solidified spot sample is not limited, and optionally, in this embodiment, a linear cutting device is used to cut the solidified spot sample into a cube of 5mm × 5mm × 3mm, so as to form a solidified spot sample block. In order to ensure that the solidified spots are observed under a high power electron microscope, the thickness of the solidified spot sample block in this embodiment cannot be too large.
In the present embodiment, the size of the solidified spot sample block is not limited as long as it can be used for subsequent stress analysis, that is, subsequent observation and image capturing under a field emission scanning electron microscope, stress analysis, and the like. Optionally, in this embodiment, the size of the solidified spot sample block is defined as 5mm × 5mm × 3mm, and in other embodiments of the present invention, the size of the solidified spot sample block may also be other sizes, which is not limited in this embodiment.
S13: and cleaning the solidified spot sample block to obtain the solidified spot test sample.
In the embodiment of the present invention, a specific cleaning process is not limited, as long as the solidified spot sample block can be cleaned to prepare for a subsequent test, and optionally, in the embodiment, an ultrasonic device is used to clean the solidified spot sample block after the cutting and polishing is completed, the solidified spot sample block is cleaned 3 times, each time is 6-8 minutes, and the cleaning solvent is ethanol with a concentration of 97.5. It should be noted that, the number of times of cleaning and the cleaning time are not limited in this embodiment, and may be set according to the actual cleaning requirement and the cleanliness during the cleaning process.
In this embodiment, after the cleaning, the solidified spot sample block is dried quickly and stored in a sealed manner, so as to reduce the reaction between the solidified spot sample block and air, which may cause unnecessary stress release and affect the residual stress test accuracy. Therefore, in this embodiment, after the cleaning is completed, the solidified spot test block is dried by a blower with 2000kW power, and then the solidified spot test block is wrapped by dust-free paper to form a solidified spot test sample, and the solidified spot test sample is placed in a sample bag to be sealed and stored, and is stored in a drying dish to wait for subsequent use.
S2: manufacturing a dot matrix on a region to be measured of the solidification spot test sample;
in this embodiment, a specific process of selecting a region to be measured on the coagulated speckle test sample and fabricating a dot matrix on the region to be measured, as shown in the schematic flow chart shown in fig. 3, includes:
s21: carrying out metal spraying treatment on the surface of the solidification spot test sample;
based on the above described procedure of providing the solidified spot test specimen, the solidified spot test specimen was taken out from the drying dish, and the surface of the solidified spot test specimen was subjected to a metal spraying treatment for 3min to further increase the conductivity of the solidified spot test specimen.
S22: placing the solidified spot test sample under a field emission scanning electron microscope for observation;
in this embodiment, the solidified spot test sample is placed under a field emission scanning electron microscope to observe the coating morphology of the solidified spot test sample.
S23: selecting a region to be measured under the field emission scanning electron microscope;
selecting the magnification of the field emission scanning electron microscope to be 30000 times, and moving the area to be measured into the field of view;
s24: depositing a platinum layer on the surface of the area to be measured;
in this embodiment, a platinum (Pt) layer a is deposited on the surface of the region to be measured, as shown in fig. 4A and 4B, fig. 4A is a schematic top view of a circular Pt layer formed on a solidified spot, and fig. 4B is a schematic cross-sectional structure of the graph shown in fig. 4A. It should be noted that, in this embodiment, the shape of the Pt layer is not limited, and may be a regular shape, so that when the surrounding material is removed later, the Pt layer can be removed more conveniently. The size of the Pt layer is not limited in this embodiment, and optionally, the diameter of the Pt layer is 10 μm, and the thickness of the Pt layer is 50nm to 200nm, and optionally, the thickness of the Pt layer is 100nm in this embodiment, so as to provide a homogeneous stress-free standard contrast surface, and at the same time, protect the region to be measured from being damaged in the ion thinning process that occurs when the surrounding material is removed later.
S25: and forming a plurality of pits on the surface of the platinum layer by adopting focused ion beams to form a dot matrix.
Specifically, in this embodiment, a focused ion beam is used to prepare 6 × 6 circular pits B on the Pt surface, the pits B may be cylinders with a diameter and a height of 100nm, the pit pitch and arrangement are shown in fig. 4C, and when removing, the current of the focused ion beam is 20nA, and the voltage is 30 kV.
The dot matrix is formed in this embodiment, and is designed to facilitate comparison of displacement deformation amounts between pixel points between images with different morphologies when surface stress of a solidified spot is analyzed subsequently, and therefore, the number of pits in the dot matrix, the size of the pits, and the arrangement mode of the pits are not limited in this embodiment.
S3: acquiring a first topography image of the area to be measured;
in this embodiment, the formation of the dot matrix is performed by using a focused ion beam, and after the formation of the dot matrix, a scanning electron microscope image morphology photograph of the region to be measured after the formation of the dot matrix can be directly taken by using the focused ion beam, so as to form a first morphology image, which is denoted as a1 in this embodiment.
S4: removing the materials around the area to be measured layer by layer, and acquiring a shape image of the area to be measured after removing each layer of material;
the method specifically comprises the following steps:
adopting a focused ion beam to remove materials around the area to be measured for the first time;
as shown in FIG. 4D, a circular groove C having an outer diameter of 15 μm and an inner diameter of 10 μm was formed along the outer edge of the circular Pt layer A. When the material around the Pt layer is removed, the current of the focused ion beam is 100pA, the voltage is 30kV, and the time is 50ns, wherein the parameters of the focused ion beam are limited to mainly control the depth of the circular ring.
A second morphological image of the area to be measured after the material removal is obtained in the secondary electron photography mode.
A second topographic image of the area to be measured after removal of material is acquired in a secondary electron capture mode, denoted a 2.
Then repeating the steps, and adopting focused ion beams to carry out secondary removal on the materials around the area to be measured; a third relief image of the area to be measured after removal of material, which can be noted as a3 in this embodiment, is obtained in the secondary electron photography mode. Repeating the steps for multiple times, removing the material around the region to be measured layer by layer, and acquiring an i +1 th morphology image of the region to be measured after the material of the i-th layer is removed, and recording the i +1 th morphology image as A (i +1), wherein i is a positive integer and i > 1; in this embodiment, the number of layers of the removed material is not limited in this embodiment, and the more the number of layers is removed, the more the measurement data is, the more accurate the measurement value of the final residual stress is, and in this embodiment, optionally, 10 layers of the surrounding material are removed altogether. I.e. 10, 10 topographical images of the area to be measured are obtained after material removal. FIG. 4E shows a cross-sectional view of a solidified spot after removal of 10 layers of surrounding material, with a depth z.
It should be noted that, in this embodiment, the thickness of each layer of material to be removed is not limited, and the thickness of each layer of material to be removed may be the same or different.
Wherein, the pixels of the first topography image to the i +1 th topography image are 1024 multiplied by 884. It should be noted that, in order to ensure the measurement accuracy of the residual stress, in this embodiment, it is required to ensure that the brightness and the contrast of the image are kept consistent during the two image capturing processes.
S5: obtaining displacement of each point in the dot matrix of the area to be measured after removing each layer of material according to the first topography image and the topography image of the area to be measured after removing each layer of material;
in this embodiment, the first topographic image and 11 topographic images obtained after the material is removed, including the second topographic image to the eleventh topographic image, are imported into Matlab software according to the shooting sequence.
The method for acquiring the displacement of each layer of the coating after the material of each layer is removed by adopting a digital speckle method specifically comprises the following steps:
the displacement amount of each pit in the a2 image after the first material removal was calculated with the a1 image as a standard image. According to the similarity of the image feature regions, the pits in the A2 image are respectively corresponding to the original pits in the A1 image, the feature region identification mode is expressed by a normalization coefficient C, and the formula is as follows:
wherein f (x)i,yi)、g(x′i,y′i) Respectively reference subsets (x)i,yi) Target subset (x'i,y′i) Gray value of (f)m、gmThe mean of the gray values of the reference subset and the target subset respectively,
respectively representing the displacement in the x and y directions, and n represents the number of pits in the reference subset.
Respectively taking An image as a reference image of An +1 images, calculating the displacement of each pit in the An +1 image, and recording asn(n＝1,2,3,……,10)。
S6: and calculating the residual stress of the region to be measured after removing the material of each layer according to the displacement of each point in the lattice.
The method specifically comprises the following steps:
1) and calculating the plane stress of each pit according to the strain distribution of the surface of the area to be measured:
wherein (H) is the strain at which the material is removed to a depth H,
the directions are displacement in the x and y directions respectively.
2) And calculating to obtain the average residual stress of the region to be measured according to the change condition of the surface stress, wherein after the material is removed for the nth time, the surface strain of the material for n-1 times is redistributed, namely the corresponding surface residual stress distribution state is changed. Therefore, in order to improve the precision of biaxial stress measurement, multiple tests are required, and finally an average value is taken as the average residual stress of the region to be measured, that is, the average residual stress of the material, and the strain relationship between the stresses at different depths and the surface of the material is as follows:
h is the total depth of material removal, H is a variable and represents any position from the surface of the material to the bottom of the circular ring pit, (H) is the surface strain when the material is removed to the depth of H, sigma (H) represents the stress when the material is removed to the depth of H, and A (H, H) reflects the influence degree of the residual stress at the depth of H on the surface strain degree of the material when the total depth of material removal is H;
3) plotting the residual stress of the region to be measured as a function of depth, i.e.
Curve (H ═ i × z, which represents the material depth, z being the single removal depth of material).
The invention provides a method for detecting residual stress of a solidified spot, which comprises the steps of providing a solidified spot test sample; manufacturing a dot matrix on a region to be measured of the solidification spot test sample; acquiring a first topography image of the area to be measured; removing the materials around the area to be measured layer by layer, and acquiring a shape image of the area to be measured after removing each layer of material; obtaining displacement of each point in the dot matrix of the area to be measured after removing each layer of material according to the first topography image and the topography image of the area to be measured after removing each layer of material; and calculating the residual stress of the region to be measured after removing the material of each layer according to the displacement of each point in the lattice. The residual stress of the area to be measured after the peripheral material is removed is calculated, so that the residual stress of different depths in the solidification spot is detected, and the residual stress of the solidification spot is measured.
In addition, the solidification spot residual stress detection method provided by the invention does not need to provide a stress-free sample for comparison, and simplifies the detection process of the residual stress; the solidification spot residual stress detection method provided by the invention is not limited by a detection object, and the sample preparation process is simple. The focused ion beams are adopted to remove the material in the area to be measured layer by layer, so that the depth can be accurately controlled; the appearance of the area to be measured is observed by adopting a field emission scanning electron microscope, so that the detection position can be accurately controlled; and removing the material layer by layer to obtain the residual stress at different depths, thereby improving the testing precision of the residual stress in the amorphous material.
The embodiment of the present invention further provides a method for detecting residual stress of a solidified spot, a flowchart of which is shown in fig. 5, and the method includes:
s501: providing a coagulated speck test specimen;
s502: manufacturing a dot matrix on a region to be measured of the solidification spot test sample;
s503: acquiring a first topography image of the area to be measured;
s504: presetting N layers for removing materials around the area to be measured;
where N is a positive integer greater than or equal to 2, and may preferably be 10.
S505: removing the materials around the area to be measured layer by layer, and acquiring a shape image of the area to be measured after removing each layer of material;
s506: judging whether the number of the removed layers reaches N;
if yes, the next step is carried out, and if not, the step S505 is returned to;
s507: obtaining displacement of each point in the dot matrix of the area to be measured after removing each layer of material according to the first topography image and the topography image of the area to be measured after removing each layer of material;
s508: and calculating the residual stress of the region to be measured after removing the material of each layer according to the displacement of each point in the lattice.
It should be noted that, the detailed contents of each step in this embodiment are similar to those in the previous embodiment, and the detailed steps may refer to the previous embodiment, which is not described in this embodiment.
It should be noted that, in the present specification, the embodiments are all described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended 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 (6)
1. A solidification spot residual stress detection method is characterized by comprising the following steps:
providing a coagulated speck test specimen;
manufacturing a dot matrix on a region to be measured of the solidification spot test sample;
acquiring a first topography image of the area to be measured;
removing the materials around the area to be measured layer by layer, and acquiring a shape image of the area to be measured after removing each layer of material;
obtaining displacement of each point in the dot matrix of the area to be measured after removing each layer of material according to the first topography image and the topography image of the area to be measured after removing each layer of material;
calculating the residual stress of the region to be measured after removing the material of each layer according to the displacement of each point in the lattice;
wherein, the manufacturing of the dot matrix on the region to be measured of the solidified spot test sample specifically comprises:
carrying out metal spraying treatment on the surface of the solidification spot test sample;
placing the solidified spot test sample under a field emission scanning electron microscope for observation;
selecting a region to be measured under the field emission scanning electron microscope;
depositing a platinum layer on the surface of the area to be measured;
forming a plurality of pits on the surface of the platinum layer by adopting focused ion beams to form a dot matrix;
the obtaining, according to the first topographic image and the topographic image of the area to be measured after removing the layer material of each layer, displacement amounts of each point in the dot matrix of the area to be measured after removing the layer material of each layer specifically includes:
calculating displacement of each pit on the second topographic image by using the first topographic image as a reference image and adopting a digital speckle correlation method;
and calculating the displacement of each pit on the (i +1) th morphology image by using the ith morphology image as a reference image and adopting a digital speckle correlation method, wherein i is a positive integer and is not less than 1.
2. The method for detecting the residual stress of the coagulated spot according to claim 1, wherein the step of providing the test sample of the coagulated spot specifically comprises:
providing a coagulated speckle sample;
cutting the solidified spot sample into solidified spot sample blocks of 5mm multiplied by 3 mm;
and cleaning the solidified spot sample block to obtain the solidified spot test sample.
3. The method for detecting the residual stress of the solidified spots according to claim 1, wherein the removing the material around the region to be measured layer by layer and the obtaining the topographic image of the region to be measured after removing the material of each layer specifically comprises:
removing the ith layer of the material around the area to be measured by using a focused ion beam;
obtaining an i +1 th topographic image of the area to be measured after the material is removed in a secondary electron shooting mode;
wherein i is a positive integer, and i is more than or equal to 1.
4. The method for detecting the residual stress of the solidified spot according to claim 1, wherein the platinum layer is circular.
5. The method for detecting the residual stress of a coagulated spot according to claim 4,
the calculating the residual stress of the region to be measured after removing the material of each layer according to the displacement of each point in the lattice specifically includes:
and calculating the plane stress of each pit according to the strain distribution of the surface of the area to be measured:
wherein (H) is the strain at which the material is removed to a depth H,
displacement in x and y directions;
calculating to obtain the average residual stress of the region to be measured according to the change condition of the surface stress, wherein the strain relationship between the stresses at different depths and the surface of the material is as follows:
h is the total depth of material removal, H is a variable and represents any position from the surface of the material to the bottom of the circular ring pit, (H) is the strain of the surface when the material is removed to the depth of H, sigma (H) represents the stress when the depth of material removal is H, and A (H, H) reflects the influence degree of the residual stress at the depth H on the strain degree of the surface of the material when the total depth of material removal is H;
and drawing a curve of the residual stress of the area to be measured along with the depth.
6. The method for detecting the residual stress of the solidified spot according to claim 5, wherein in the step of removing the material around the region to be measured layer by layer, the thickness of the material removed in each layer is the same.
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