A method for analyzing plastic deformation of a metal material by laser shock

Abstract

This invention relates to a method for analyzing the plastic deformation law of laser-shocked metallic materials, comprising: marking first micro-indentations on the surface and back of the undeformed metallic material; measuring the first indentation distance between two adjacent first micro-indentations; performing overlapping laser shock on the surface of the metallic material; and measuring the second indentation distance between two adjacent second micro-indentations and two third micro-indentations on the surface and back of the plastically deformed metallic material, respectively. 、 The third indentation spacing and its corresponding curvature; based on the first, second, and third indentation spacings, the elongation and plastic strain of the surface and back of the metal material are obtained. The purpose of this analytical method for the plastic deformation law of laser-shocked metal materials is to solve the problem of how to effectively test and analyze the elongation, strain layer depth, and strain rate of laser-shocked metal materials.

Description

Technical Field

[0001] This invention relates to the field of materials plastic deformation technology, and specifically to an analytical method for the plastic deformation law of laser-shocked metallic materials. Background Technology

[0002] Laser shock peening (also known as laser shot peening) is a new technology that utilizes the mechanical effect of laser shock waves generated by the explosion of plasma induced by a strong laser beam radiating the surface of a target material to refine the grains and residual compressive stress on the surface of metal materials, thereby improving their resistance to fatigue, corrosion and fretting wear. By controlling the impact trajectory, precise shaping and plastic deformation can be achieved.

[0003] Laser shock strengthening process has the following advantages: (1) simple process equipment, no forming mold required; (2) precise control of pulse parameters and action area and repeatability; (3) high processing flexibility of forming plate; (4) high quality surface forming of medium and thick plates; (5) improved mechanical properties of plate. Therefore, it is widely used in aerospace and military fields and has become a new process for fatigue resistance, shaping and plastic deformation of key components.

[0004] Laser shock peening for plastic deformation of wing panels and fatigue life extension and shape correction of engine blades requires both aerodynamic shape and dimensional assembly, thus there are two key technical points: (1) obtaining the required curved surface shape of the parts; (2) controlling the elongation rate of the parts. Key point 1 is related to the depth of the strain layer and the elongation rate. The smaller the radius of curvature, the greater the elongation rate, and the better the plastic deformation. Key point 2 is related to the elongation rate. How to ensure that a suitable elongation rate is obtained is one of the key issues in laser shock peening for plastic deformation of metallic materials.

[0005] The patent [A Modeling and Discrimination Method for the Plastic Deformation Depth of Laser Shock-Strengthened Alloys, Application No.: 201610785814.X] calculates and derives the plastic deformation depth formed on the surface of laser-shocked alloys, obtaining an analytical expression for the plastic deformation depth of laser-shocked metal alloys. This yields the relationship between dynamic yield strength, peak shock pressure, viscosity coefficient, elastic modulus, and plastic deformation depth during the laser-shock strengthening process. BSYilbas et al. used numerical simulation to predict the plastic deformation depth of laser-shocked aluminum alloys and conducted a simple experimental verification [Lasershock processing of aluminum: model and experimental study. Journal of Physics D: Applied Physics, 2007, 40: 6740]. P. Peyre et al. obtained calculation formulas for the plastic deformation depth and residual stress of laser-shocked aluminum alloys, but did not consider the surface compression caused by laser shock on the aluminum alloy surface [Laser shock processing of aluminum alloys: Application to high cyclefatigue behaviour. Materials Science and Engineering A, 1996, 210:102]. However, it is impossible to test the elongation, strain layer depth, and strain rate of metallic materials.

[0006] Therefore, the inventors have provided an analytical method for the plastic deformation law of laser-impacted metallic materials. Summary of the Invention

[0007] (1) Technical problems to be solved

[0008] This invention provides an analytical method for the plastic deformation law of laser-shocked metallic materials, solving the technical problem of how to effectively test and analyze the elongation, strain layer depth, and strain rate of laser-shocked metallic materials.

[0009] (2) Technical solution

[0010] This invention provides a method for analyzing the plastic deformation law of laser-shocked metallic materials, comprising the following steps:

[0011] Step 1: Mark the first micro-indentation on the surface and back of the undeformed metal material;

[0012] Step 2: Measure the distance between the first indentations of two adjacent first micro-indentations;

[0013] Step 3: Apply overlapping laser impact to the surface of the metal material;

[0014] Step 4: Measure the distance between two adjacent second micro-indentations and two third micro-indentations on the surface and back of the plastically deformed metal material, as well as the distance between the third micro-indentations and their corresponding curvature.

[0015] Step 5: Based on the first indentation spacing, the second indentation spacing, and the third indentation spacing, obtain the elongation and plastic strain of the surface and back of the metal material.

[0016] Furthermore, marking the first micro-indentation on the surface and back of the undeformed metallic material specifically involves:

[0017] The metal material is subjected to wire cutting, grinding, and polishing, and the first micro-indentation is marked on the surface and back of the undeformed metal material using a marking method.

[0018] Further, the measurement of the first indentation distance between two adjacent first micro-indentations specifically involves:

[0019] The distance between two adjacent first micro-indentations on the surface and back of an undeformed metallic material was measured using a surface profilometer.

[0020] Furthermore, the laser impact cladding of the metal material surface specifically involves:

[0021] A high-energy laser beam is used to perform overlapping laser impact on the surface of the metal material.

[0022] Furthermore, the measurement of the second indentation spacing, the third indentation spacing, and the corresponding curvature between two adjacent second micro-indentations and two third micro-indentations on the surface and back of the plastically deformed metal material specifically includes:

[0023] The indentation profile length and the indentation profile angle between the first micro-indentation on the surface and back of the formed medium-thick metal material were measured using a surface profilometer.

[0024] Furthermore, after step 5, the following steps are also included:

[0025] Step 6: Remove the strain-affected layer from the interior of the plastically deformed metal material and measure the spacing between the fourth and fifth indentations between two adjacent fourth and fifth micro-indentations on the surface and back.

[0026] Step 7: Based on the first indentation spacing, the fourth indentation spacing, and the fifth indentation spacing, obtain the corresponding first nominal strain and second nominal strain;

[0027] Step 8: Based on the first indentation spacing, the second indentation spacing, and the third indentation spacing, obtain the corresponding first actual strain and second actual strain;

[0028] Step 9: Based on steps 6 to 8, measure and analyze the relationship between nominal strain and actual strain of metal materials of different thicknesses, and establish a process database of laser process parameters, nominal strain, and actual strain.

[0029] Step 10: Based on the process database, predict the plastic deformation shape of the laser-shocked metal material.

[0030] Furthermore, the measurement and analysis of the relationship between nominal strain and actual strain of metal materials of different thicknesses, and the establishment of a process database of laser process parameters, nominal strain, and actual strain, specifically involves:

[0031] Establish the relationship between laser power density and nominal and actual strain for metal materials of different thicknesses, and form the process database.

[0032] The relation is as follows: In the formula, I For laser power density, h For the thickness of the metal material, This refers to nominal strain or actual strain.

[0033] Furthermore, predicting the plastic deformation shape of laser-shocked metallic materials based on the process database specifically involves:

[0034] Based on the aforementioned process database, the plastic deformation of laser-shocked metal materials is predicted for metal materials of different thicknesses and with different laser power densities.

[0035] (3) Beneficial effects

[0036] In summary, the marking method of this invention features small marking size, does not affect surface measurement, and is easy to locate. The measurement and analysis methods are simple and fast to operate. In addition to testing the plastic deformation law in the depth direction, this analysis method also effectively tests the elongation of metallic materials in the length direction and predicts the macroscopic plastic deformation law of metallic materials, laying a theoretical foundation for applications in plastic forming engineering. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1This is a flowchart illustrating an analytical method for the plastic deformation law of laser-shocked metallic materials provided in an embodiment of the present invention.

[0039] Figures 2(a) to (c) are schematic diagrams of a laser-shocked metal material elongation test provided in an embodiment of the present invention;

[0040] Figures 3(a) to (b) are schematic diagrams of a laser shock strain test for metallic materials provided in an embodiment of the present invention;

[0041] Figures 4(a) to (b) are diagrams illustrating the bending deformation mechanism of a laser-shocked R-region sample provided in an embodiment of the present invention.

[0042] Figure 5 This is a schematic diagram of the spacing between points 1 to 3 on the back side of a matrix material sample in the 90-degree R region, provided in an embodiment of the present invention.

[0043] Figure 6 This is a schematic diagram of the spacing between points 1 to 3 on the back side of a 90-degree R-zone sample subjected to a single laser shock, provided by an embodiment of the present invention.

[0044] Figure 7 This is a schematic diagram of the spacing between points 1 to 3 on the back side of a 90-degree R-zone sample subjected to four laser shocks, as provided in an embodiment of the present invention.

[0045] In the picture:

[0046] 1-Unformed medium-thick metal material; 2-Laser shock zone; 3-First micro-indentation; 4-First indentation spacing; 5-Indentation contour length of formed medium-thick metal material; 6-Laser beam; 7-Formed medium-thick metal material; 8-Indentation contour angle; 9-Deformation region; 10-First strain layer; 11-Indentation contour length of formed thin metal material; 12-Second strain layer; 13-Formed thin metal material. Detailed Implementation

[0047] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention by way of example, but should not be used to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments, and any modifications, substitutions and improvements to the parts, components and connection methods are covered without departing from the spirit of the present invention.

[0048] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0049] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0050] Figure 1 This is a flowchart illustrating a method for analyzing the plastic deformation law of laser-shocked metallic materials according to an embodiment of the present invention. The method may include the following steps:

[0051] S101. Mark the first micro-indentation on the surface and back of the undeformed metallic material;

[0052] S102. Measure the distance between the first indentations of two adjacent first micro-indentations;

[0053] S103. Apply laser impact to the surface of metallic materials;

[0054] S104. Measure the distance between two adjacent second micro-indentations and two third micro-indentations on the surface and back of the plastically deformed metal material, as well as their corresponding curvature.

[0055] S105. Based on the first indentation spacing, the second indentation spacing, and the third indentation spacing, obtain the elongation and plastic strain of the metallic material.

[0056] In the above embodiments, as shown in Figures 2(a) to 2(c), the difference between the first indentation spacing L and the second indentation spacing L1 on the surface and back of the metal material before and after laser shock forming is compared and analyzed to obtain the elongation of the metal material. By comparing and measuring the indentation spacing in different regions, the elongation rate and the corresponding included angle α1 of different regions were obtained.

[0057] This analytical method involves marking the reinforced areas of a metallic material, measuring and comparing the size and morphology of the marks before and after reinforcement, and obtaining the elongation and plastic strain of the material under plastic deformation. The marking method has advantages such as small mark size, no impact on surface measurement, and easy positioning. The measurement and analysis methods are simple and fast to operate.

[0058] As an optional implementation, in step S101, the first micro-indentation is marked on the surface and back of the undeformed metal material. Specifically, the metal material is wire-cut, ground, and polished, and the first micro-indentation is marked on the surface and back of the undeformed metal material using a marking method.

[0059] Specifically, the metal material 1 is processed by wire cutting, grinding and polishing, and the first micro-indentation 3 is marked on the surface and back of the unformed medium-thick metal material 1 using a microhardness tester.

[0060] As an optional implementation, in step S102, measuring the first indentation distance between two adjacent first micro-indentations specifically involves using a surface profilometer to measure the first indentation distance between two adjacent first micro-indentations on the surface and back of the undeformed metal material.

[0061] Specifically, as shown in Figures 2(a) to 2(c), the distance 4 between the first indentation 3 of adjacent first micro-indentations 3 on the surface and back of the unplastic-deformed medium-thick metal material 1 is measured to be L using a surface morphology instrument. The distance between two adjacent micro-indentations on the surface and back of the unplastic-deformed medium-thick metal material 1 is the same, while the distance between two adjacent micro-indentations on the surface and back of the formed medium-thick metal material is completely different.

[0062] As an optional implementation, in step S103, the surface of the metal material is subjected to overlapping laser shock, specifically by using a high-energy laser beam to perform overlapping laser shock on the surface of the metal material.

[0063] Specifically, as shown in Figures 2(a) to 2(c), a laser beam 6 with industrial application laser process parameters is used to perform plastic deformation treatment on the surface of the unformed medium-thick metal material 1 by overlapping laser impact zone 2.

[0064] As an optional implementation, in step S104, the measurement of the second indentation spacing, the third indentation spacing, and their corresponding curvature between two adjacent second micro-indentations and two third micro-indentations on the surface and back of the plastically deformed metal material specifically includes:

[0065] The surface profilometer was used to measure the indentation profile length L1 (i.e., the second indentation spacing and the third indentation spacing between two adjacent first micro-indentations on the surface and the back) and the indentation profile angle α1 (i.e., the central angle corresponding to the arc formed by two adjacent first micro-indentations on the surface and the back) between the surface and the back of the formed medium-thick metal material 7, respectively. Since the plastic deformation of the surface and the back of the metal material is different, the second indentation spacing and the third indentation spacing are different) and the indentation profile angle α1 (i.e., the central angle corresponding to the arc formed by two adjacent first micro-indentations, of course, the angle between the surface and the back is different).

[0066] As an optional implementation, after step S105, the following step is also included:

[0067] S106. Remove the strain-affected layer from the interior of the plastically deformed metal material and measure the spacing between the third indentation and the fourth indentation between two adjacent fourth micro-indentations and two fifth micro-indentations on the surface and back.

[0068] S107. Based on the first indentation spacing, the fourth indentation spacing, and the fifth indentation spacing, obtain the corresponding first nominal strain and second nominal strain;

[0069] S108. Based on the first indentation spacing, the second indentation spacing, and the third indentation spacing, obtain the corresponding first actual strain and second actual strain;

[0070] S109. Based on steps S106 to S108, measure and analyze the relationship between nominal strain and actual strain of metal materials of different thicknesses, and establish a process database of laser power density, nominal strain and actual strain.

[0071] S110. Based on the process database, predict the shape of plastic deformation of laser-shocked metallic materials.

[0072] In the above embodiment, the first strain layer 10 or the second strain layer 12 is removed from the deformation region 9 inside the medium-thick metal material 7 or the thin metal material 13, and the corresponding indentation spacings L2 and L4 are measured, respectively. These are then compared with the first indentation spacing L on the surface of the medium-thick metal material 7 or the thin metal material 13 in its original state (i.e., before forming) to obtain the first nominal strain. Second nominal strain .

[0073] As shown in Figures 3(a) and 3(b), the actual strain is obtained by comparing the first micro-spacing 4 of the first micro-indentation 3 on the surface of the medium-thick metal material 7 or the thin metal material 13. and .

[0074] Through the relevant follow-up processing in steps S106 to S110 above, the forming performance of laser shock metal materials is predicted based on the process database between forming process parameters and the plastic deformation law of metal materials.

[0075] As an optional implementation method, the relationship between nominal strain and actual strain of metal materials of different thicknesses is measured and analyzed to establish a process database of laser process parameters, nominal strain, and actual strain. Specifically:

[0076] Establish the relationship between laser power density and nominal and actual strain for metal materials of different thicknesses, and form a process database;

[0077] The relation is: In the formula, IFor laser power density, h For the thickness of the metal material, This refers to nominal strain or actual strain.

[0078] As an optional implementation method, the plastic deformation shape of laser-shocked metallic materials is predicted based on a process database, specifically:

[0079] Based on the process database, the plastic deformation of laser-shocked metal materials with different thicknesses and different laser power densities is predicted.

[0080] Example 1

[0081] In this embodiment, the laser shock process parameters are: laser energy 30J, spot diameter 3mm, pulse width 15ns, overlap rate 50%, single laser shock, and the reinforced area is region R. The target material is a 7050 aluminum alloy sample in region R, with an elastic modulus of 74GPa, dynamic yield strength of 462MPa, an R-region angle of 90 degrees, and a radius of 6mm. The 90-degree R-region sample is machined using slow wire EDM, and the sample surface is ground and polished. Marks are made on the back of the substrate material sample to study the bending deformation of the sample back before and after laser shock. Figures 4(a) and 4(b) show the bending deformation mechanism of the laser-shocked R-region sample. The surface material of the laser-shocked R-region sample extends parallel to the R-region direction. Since the impact area is all above the centroid of the sample, the R-region sample undergoes positive bending deformation, which induces extrusive plastic deformation on the back of the R-region sample, thereby reducing the spacing of the marks on the back of the laser-shocked R-region sample.

[0082] Depend on Figures 5-7 It can be seen that laser shock to the 7050 aluminum alloy R-zone specimen produces positive bending deformation and extrusion plastic deformation on the back side, as shown in Table 1. Table 1 shows that compared with the matrix material, the edge length, reinforced region width, R-zone thickness, and spacing between points 1 and 2 on the back side, as well as between points 2 and 3 on the back side, increase by 0.2%, 0.7%, -0.5%, -2.2%, and -0.7% respectively after a single laser shock. After four laser shocks, the edge length, reinforced region width, R-zone thickness, and spacing between points 1 and 2 on the back side, as well as between points 2 and 3 on the back side, increase by 0.6%, 2.3%, -1.8%, -2.6%, and -1.2% respectively. The results indicate that specimen marking can effectively detect the amount of plastic deformation in the specimen; therefore, the specimen marking method is an effective analytical testing method.

[0083] Table 1. Bending deformation of laser-shocked specimens in the 90° R region.

[0084]

[0085] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0086] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art without departing from the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A method of analyzing a rule of plastic deformation of a metal material by laser shock, characterized by, The method comprises the following steps: Step 1, marking first micro-indents on the surface and back of the metal material without plastic deformation; Step 2, measuring the first indentation distance between two adjacent first micro-indents; Step 3, performing lap laser impact plastic deformation on the surface of the metal material; Step 4, measuring the second indentation distance between two adjacent second micro-indents, the third indentation distance between two adjacent third micro-indents, and the corresponding arc on the surface and back of the metal material after plastic deformation, respectively; Step 5, obtaining the elongation and plastic strain of the surface and back of the metal material according to the first indentation distance, the second indentation distance, and the third indentation distance; Step 6, taking the strain affected layer from the inside of the metal material after plastic deformation, and measuring the fourth indentation distance between two adjacent fourth micro-indents and the fifth indentation distance between two adjacent fifth micro-indents on the surface and back; Step 7, obtaining the corresponding first nominal strain and second nominal strain according to the first indentation distance and the fourth indentation distance and the fifth indentation distance; Step 8, obtaining the corresponding first actual strain and second actual strain according to the first indentation distance and the second indentation distance and the third indentation distance; Step 9, measuring and analyzing the relationship between the nominal strain and the actual strain of the metal material with different thicknesses according to steps 6-8, and establishing a process database of laser process parameters and nominal strain and actual strain; Step 10, predicting the plastic deformation shape of the metal material impacted by the laser according to the process database; The measuring and analyzing the relationship between the nominal strain and the actual strain of the metal material with different thicknesses, and establishing a process database of laser process parameters and nominal strain and actual strain, specifically comprises: Establishing a relationship between the laser power density and the nominal strain and the actual strain of the metal material with different thicknesses, and forming the process database; wherein the relationship is: ; wherein, I is the laser power density, h is the thickness of the metal material, is the nominal or actual strain; The predicting the plastic deformation shape of the metal material impacted by the laser according to the process database, specifically comprises: Predicting the plastic deformation of the metal material impacted by the laser according to the process database, different thicknesses of the metal material, and different laser power densities.

2. The method according to claim 1, wherein The marking first micro-indents on the surface and back of the metal material without plastic deformation, specifically comprises: Performing wire cutting processing, grinding, and polishing on the metal material, and marking the first micro-indents on the surface and back of the unformed metal material by using a marking method.

3. The method according to claim 1, wherein The measuring the first indentation distance between two adjacent first micro-indents, specifically comprises: Measuring the first indentation distance between two adjacent first micro-indents on the surface and back of the metal material without plastic deformation by using a surface topography instrument.

4. The method according to claim 1, wherein The performing lap laser impact on the surface of the metal material, specifically comprises: Performing lap laser impact on the surface of the metal material by using a high-energy laser beam.

5. The method according to claim 1, wherein The measuring the second indentation distance between two adjacent second micro-indents, the third indentation distance between two adjacent third micro-indents, and the corresponding arc on the surface and back of the metal material after plastic deformation, specifically comprises: The surface and back surface of the formed medium-thick metal material are measured by a surface profiler to measure the length of the indentation profile and the angle of the indentation profile between the first micro-indentations.

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