Evaluation method for residual stress distribution of material microstructure

Abstract

The invention discloses a method for evaluating residual stress distribution of a material microstructure. The method comprises the following steps of: 1, acquiring a material back scattering picture; 2, converting the back scattering picture into an RGB (Red, Green and Blue) picture; 3, performing grid partitioning on the RGB image and establishing a finite element model; 4, acquiring mechanical property parameters of the material; and 5, calculating the microstructure residual stress of the material and drawing a residual stress distribution cloud picture. According to the method, the back scattering picture of the material is converted, the finite element model is established, the mechanical property parameters of the material are combined, the microstructure residual stress of the material is calculated, and the microstructure residual stress distribution cloud picture is obtained, so that the residual stress distribution of the microstructure of the material can be intuitively presented; later analysis of material fracture behaviors, exploration of stress concentration problems and regulation and control of material microstructures are facilitated; the microcosmic residual stress of the structure generated by the material in different test states can be efficiently and accurately obtained at low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of microstructure residual stress evaluation, and in particular relates to an evaluation method for material microstructure residual stress distribution. Background Art

[0002] At present, the detection of residual stress is generally divided into destructive testing methods (drilling method, indentation method, etc.) and non-destructive testing methods (X-ray diffraction method, neutron diffraction method, Raman method, etc.). These two types of detection methods either cause damage to the material or limit the grain size of the material organization. In particular, the latter method requires expensive equipment and testing fees, and both methods reflect the overall macroscopic residual stress distribution of the material, and it is difficult to analyze the interaction between the microstructures inside the material. Through the analysis of the residual stress of the microstructure, we can have a deeper understanding of the intrinsic relationship between the microstructure and performance of the material, which is crucial for evaluating the mechanical properties, fatigue life and overall stability of the material. In addition, by studying the distribution of residual stress in the microstructure, we can have a deeper understanding of the mechanism of stress corrosion cracking, and then optimize the distribution and phase composition of alloying elements, and finally improve the corrosion resistance of the material, providing a theoretical basis for preventing and controlling this type of corrosion failure. Therefore, based on the above analysis, there is an urgent need for an efficient, low-cost and accurate method for evaluating the residual stress distribution of the microstructure of the material. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for evaluating the residual stress distribution of a material microstructure in view of the deficiencies in the above-mentioned prior art. By converting the backscatter image of the material and establishing a finite element model, the residual stress of the material's microstructure is calculated and a cloud map of the residual stress distribution of the microstructure is obtained in combination with the mechanical property parameters of the material. The residual stress distribution of the material's microstructure can be intuitively presented, which is convenient for the subsequent analysis of the material's fracture behavior, the exploration of stress concentration problems, and the regulation of the material's microstructure. The method realizes the efficient, low-cost and accurate acquisition of the microscopic residual stress of the tissue generated by the material under different test conditions.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for evaluating the residual stress distribution of a material microstructure, characterized in that the method comprises the following steps: Step 1: Obtain material backscattering images; Step 2: Convert the backscatter image into an RGB image; Step 3: Mesh the RGB image and establish a finite element model; Step 4: Obtain the mechanical properties parameters of the material; Step 5: Calculate the microstructure residual stress of the material and draw a residual stress distribution cloud map.

[0005] The above-mentioned method for evaluating residual stress distribution of a material microstructure is characterized in that: in step 2, regional division is performed according to the distribution of different phases and tissues in the backscattered image, and the same phases and tissues are colored to obtain an RGB image.

[0006] The above-mentioned method for evaluating residual stress distribution of a material microstructure is characterized in that: in step three, the RGB image is grid-partitioned according to the colors in the RGB image.

[0007] The above-mentioned method for evaluating residual stress distribution of a material microstructure is characterized in that: in step four, the mechanical property parameters of the material include elastic modulus, thermal expansion coefficient, yield strength and Poisson's ratio.

[0008] The above-mentioned method for evaluating residual stress distribution in a material microstructure is characterized in that: in step 4, the mechanical property parameters of the material are obtained through experiments or first-principles calculations.

[0009] The above-mentioned method for evaluating the residual stress distribution of the microstructure of a material is characterized in that: in step five, the finite element model established by the partitioning in step three and the mechanical property parameters of the material obtained in step four are combined to calculate the microstructure residual stress value of the material, and a microstructure residual stress distribution cloud map is drawn based on the calculated microstructure residual stress value.

[0010] The beneficial effects of the present invention are that by converting the backscattered image of the material and establishing a finite element model, the microstructure residual stress of the material is calculated and a microstructure residual stress distribution cloud map is obtained in combination with the mechanical property parameters of the material, which can intuitively present the residual stress distribution of the material's microstructure, facilitate the subsequent analysis of the material's fracture behavior, explore the stress concentration problem, and regulate the material's microstructure; and achieve efficient, low-cost, and accurate acquisition of the microstructure residual stress of the material under different test conditions.

[0011] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The figure is a flowchart of the method of the present invention.

[0013] Figure 2 This is the backscattering image of the AgCu / Mo microstructure of the present invention.

[0014] Figure 3 It is the residual stress distribution cloud diagram corresponding to the AgCu / Mo microstructure of the present invention. DETAILED DESCRIPTION

[0015] like Figure 1 , Figure 2 and Figure 3 A method for evaluating residual stress distribution in a material microstructure is shown, and the method comprises the following steps. The specific process is as follows Figure 1 As shown: Step 1: Obtain material backscattering images; Step 2: Convert the backscatter image into an RGB image; Step 3: Mesh the RGB image and establish a finite element model; Step 4: Obtain the mechanical properties parameters of the material; Step 5: Calculate the microstructure residual stress of the material and draw a residual stress distribution cloud map.

[0016] The present invention converts the backscattered image of the material and establishes a finite element model. In combination with the mechanical property parameters of the material, the microstructure residual stress of the material is calculated and a microstructure residual stress distribution cloud map is obtained. The residual stress distribution of the material microstructure can be intuitively presented, which is convenient for the later analysis of the material fracture behavior, the exploration of stress concentration problems and the regulation of the material microstructure. The present invention realizes the efficient, low-cost and accurate acquisition of the microstructure residual stress of the material under different test conditions.

[0017] In actual use, the present invention is suitable for evaluating the residual stress distribution of the microstructure of metal materials or non-metal materials; wherein, in step 1, the selected material is observed for backscattering under a scanning electron microscope to obtain a backscattering image, and the selected image magnification should be able to clearly distinguish different phases and structures, and there is no limit on the magnification. In step two, the same phases and tissues are colored, and a machine learning algorithm is used to obtain an RGB image. This method can quickly divide different phases and tissues into regions by learning the characteristics of different phases and tissues in an image, and obtain a more accurate RGB image of material backscattering.

[0018] In step 4, the mechanical properties parameters of the microstructure are obtained by experimental methods. The Young's modulus and Poisson's ratio at different positions are obtained by continuous and equal spacing on the surface of the material using a nanoindentation tester. Then, the Young's modulus and Poisson's ratio parameters of different phases and tissues are obtained based on the indentation site combined with the nanoindentation data in the backscattering mode of the scanning electron microscope. For the thermal expansion coefficient parameters and yield strength parameters of different phases and tissues, the corresponding individual phases and tissues can be tested by a differential scanning calorimeter and a universal tensile testing machine to obtain their parameters.

[0019] The first-principles calculation method is used to obtain the mechanical properties parameters of the microstructure. First, the conventional primitive cell structure files of the phases and tissues are obtained, and then the conventional primitive cell structure files with different scaling factors are established and the conventional primitive cell structure files are optimized with high precision. Finally, the stress-strain method or the energy-strain method is used to obtain the Young's modulus and Poisson's ratio and other parameters of the calculated phases and tissues. For the thermal expansion coefficient parameters of different phases and tissues, first, the primitive cell structure files of the phases and tissues are obtained. Then, the primitive cell structure files with different scaling factors are established and the high-precision structural optimization is performed on them respectively. Subsequently, the primitive cells with different scaling factors are expanded, and the corresponding thermodynamic properties are obtained by the perturbation density functional method and the finite displacement method using the Phonopy software to obtain the thermal expansion coefficients of the phases and tissues.

[0020] In the present invention, the microstructure of AgCu / Mo is taken as an example: Step 1: Observe the backscattering of AgCu / Mo under a scanning electron microscope to obtain a backscattering image, such as Figure 2 As shown; Step 2: Divide the area according to the distribution of different phases and tissues in the AgCu / Mo backscattering image, and color the same phases and tissues to obtain an RGB image; Step 3: mesh the RGB image of AgCu / Mo, and use finite element software (abaqus, ansys) to mesh and model according to different regions; Step 4: Obtain relevant mechanical properties parameters of AgCu and Mo (such as Young's modulus, Poisson's ratio, yield strength and thermal expansion coefficient, etc.); Step 5: Import the meshed model into the finite element software and input the material mechanical properties parameters obtained in step 4 to calculate and solve the material microscopic residual stress distribution cloud map, such as Figure 3 shown.

[0021] It should be noted that if it is difficult to obtain the mechanical property parameters of the material by experiment, the mechanical property parameters are calculated by first principles. In particular, the evaluation method of the present invention can evaluate the residual stress distribution of the material structure even in the absence of certain material test data.

[0022] In this embodiment, in step 2, the regions are divided according to the distribution of different phases and tissues in the backscatter image, and the same phases and tissues are colored to obtain an RGB image.

[0023] In this embodiment, in step three, the RGB image is partitioned into grids according to the colors in the RGB image.

[0024] In this embodiment, in step 4, the mechanical property parameters of the material include elastic modulus, thermal expansion coefficient, yield strength and Poisson's ratio.

[0025] In this embodiment, in step 4, the mechanical property parameters of the material are obtained through experiments or first principles calculations.

[0026] In this embodiment, in step five, the finite element model established by partitioning in step three and the mechanical property parameters of the material obtained in step four are combined to calculate the microstructure residual stress value of the material, and a microstructure residual stress distribution cloud map is drawn based on the calculated microstructure residual stress value.

[0027] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for evaluating residual stress distribution in a material microstructure, characterized in that: The method comprises the following steps: Step 1: Obtain material backscattering images; Step 2: Convert the backscatter image into an RGB image; Step 3: Mesh the RGB image and establish a finite element model; Step 4: Obtain the mechanical properties parameters of the material; Step 5: Calculate the microstructure residual stress of the material and draw a residual stress distribution cloud map.

2. The method for evaluating residual stress distribution of a material microstructure according to claim 1, characterized in that: In step 2, the backscatter image is divided into regions according to the distribution of different phases and tissues, and the same phases and tissues are colored to obtain an RGB image.

3. The method for evaluating residual stress distribution of a material microstructure according to claim 1, characterized in that: In step three, the RGB image is grid-partitioned according to the colors in the RGB image.

4. The method for evaluating residual stress distribution of a material microstructure according to claim 1, characterized in that: In step 4, the mechanical property parameters of the material include elastic modulus, thermal expansion coefficient, yield strength and Poisson's ratio.

5. The method for evaluating residual stress distribution of a material microstructure according to claim 1, characterized in that: In step 4, the mechanical properties parameters of the material are obtained through experiments or first-principles calculations.

6. The method for evaluating residual stress distribution of a material microstructure according to claim 1, characterized in that: In step five, the microstructure residual stress value of the material is calculated by combining the finite element model established by partitioning in step three and the mechanical property parameters of the material obtained in step four, and a microstructure residual stress distribution cloud map is drawn based on the calculated microstructure residual stress value.

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