A method for laser shock peening of a metal material edge structure

Abstract

This invention discloses a laser shock peening method for edge structures of metallic materials, comprising: S1, determining the type and size of the edge structure; S2, dividing two adjacent planes of the edge structure into a primary strengthening surface and a secondary strengthening surface, and calculating the orientation relationship between the two strengthening surfaces; S3, using the bisector of the angle between the normals of the two planes as the normal to the edge surface to determine its position; S4, determining the laser shock peening power density and shock spot radius; S5, optimizing the distance between the edge surface and the edge surface on the two curved surfaces at the edge structure; S6, applying an absorbing protective layer to the strengthening area of ​​the primary strengthening surface; S7, applying an absorbing protective layer to the strengthening area of ​​the secondary strengthening surface; S8, determining the size of the strengthening area at the edge position, applying an absorbing protective layer at the edge position, and performing laser shock peening on the edge position. This invention achieves deformation control and residual stress regulation of the edge structure by adjusting the shock spot arrangement at the edge structure, meeting the requirements for laser shock fatigue resistance modification of edge structures.

Description

Technical Field

[0001] This invention relates to the field of laser shock strengthening methods, and in particular to a laser shock strengthening method for edge structures of metallic materials. Background Technology

[0002] Laser shock peening is a surface strengthening technology that uses pulsed lasers to induce plasma on the material surface. The shock wave generated by the plasma explosion is then propagated toward the material through a confinement layer, causing extremely high-rate plastic deformation in the surface area of ​​the metal material. This results in residual compressive stress with a certain depth, which significantly improves the fatigue life of the workpiece. It is widely used in the aerospace field for fatigue life extension of major load-bearing structural components.

[0003] Stress concentration often occurs at the edges of variable cross-section structures in metallic materials, leading to fatigue cracking during service, such as at hole edges and the outer fillets / chamfers of aircraft panels. When using laser shock peening for fatigue extension, the lack of constraint at the edges and the reflection of the laser-induced shock wave can easily cause collapse / extrusion of the edge structure, reducing the residual compressive stress value and even generating residual tensile stress, which is detrimental to improving fatigue resistance. Therefore, providing a laser shock peening method for metallic edge structures is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] One objective of this invention is to propose a laser shock peening method for edge structures of metallic materials. This invention achieves deformation control and residual stress regulation of the edge structure by adjusting the arrangement of shock spots at the edge structure, thereby meeting the requirements for laser shock fatigue resistance modification of the edge structure.

[0005] A laser shock peening method for edge strengthening of metallic materials according to an embodiment of the present invention includes:

[0006] S1. Determine the type and size of the edge structure of the metal material. The type and size of the edge structure of the metal material include the in-plane normal direction of each position of the edge structure of the metal material and the size of the transition fillet or chamfer of the two curved surfaces.

[0007] S2. Based on the service status of the edge structure, divide the two adjacent planes of the edge structure into a primary strengthening surface and a secondary strengthening surface, and calculate the orientation relationship between the two strengthening surfaces.

[0008] S3. Based on the orientation relationship obtained in S2, take the bisector of the angle between the normals of the two planes as the normal of the edge face to determine the position of the edge face.

[0009] S4. Determine the laser shock strengthening power density based on the material properties of the edge structure. Determine the shock spot radius based on the laser energy range of the equipment and the size of the transition fillet or chamfer between the two curved surfaces. The shock spot radius must be ≥3 * the transition fillet or chamfer between the two curved surfaces.

[0010] S5. The distance between the edge of the impact spot and the edge surface on the two curved surfaces at the edge structure is optimized by numerical simulation method.

[0011] S6. Set the laser shock strengthening process parameters, attach an absorption protective layer to the strengthening area of ​​the main strengthening surface, and complete the laser shock strengthening process of the main strengthening surface.

[0012] S7. Determine the laser shock strengthening power density and distance of the secondary strengthening surface according to S6, and attach an absorption protective layer to the strengthening area of ​​the secondary strengthening surface to complete the laser shock strengthening process of the secondary strengthening surface.

[0013] S8. Determine the size of the reinforcement area at the edge position based on the distance between the main reinforcement surface and the secondary reinforcement surface, attach the absorption protective layer at the edge position, and perform laser shock reinforcement on the edge position according to S6 and S7.

[0014] Optionally, the type of metal material edge structure in S1 is rounded corners or chamfers, and the size of the metal material edge structure is the rounded corner radius or the chamfer width.

[0015] Optionally, in step S2, the orientation relationship between the primary strengthening surface and the secondary strengthening surface is calculated, with the primary strengthening surface as the first strengthening surface and the secondary strengthening surface as the second strengthening surface.

[0016] Optionally, the edge surface in S3 includes an edge fillet tangent or a chamfered plane.

[0017] Optionally, in S3, the angle bisector of the angle between the normals n1 and n2 of the two planes is used as the normal of the edge surface.

[0018] Optionally, in S5, the edge of the impact spot is a line where the edge structure intersects with the two side planes, and the distance between them is ≥1mm.

[0019] Optionally, the laser shock peening process parameters in S6 include laser energy, spot diameter, overlap ratio, constraint layer, and beam incident direction.

[0020] Optionally, the absorbent protective layer in S6 is black tape or aluminum foil.

[0021] Optionally, in step S8, an absorption protective layer is pasted at the edge position and it is confirmed that the absorption protective layer completely covers the reinforcement area at the edge position. The laser shock reinforcement direction of the edge transition rounded corner or chamfer area is n3, where n3 = n1 + n2.

[0022] The beneficial effects of this invention are:

[0023] (1) This invention achieves deformation control and residual stress regulation of the edge structure by adjusting the arrangement of impact spots at the edge structure, thereby meeting the requirements of laser shock fatigue resistance modification of the edge structure.

[0024] (2) The present invention obtains the optimal distance between the edge of the impact spot and the edge on the two curved surfaces of the edge structure through numerical simulation, reduces the adverse effect of the shock wave on the residual compressive stress level formed on the first strengthened surface during the propagation process of the strengthened surface shock wave, improves the collapse and extrusion of the edge structure caused by the lack of constraint at the edge and the reflection of the laser-induced shock wave, optimizes the laser shock strengthening stability of the overall structure, and improves the service life and service reliability of the structural components. Attached Figure Description

[0025] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0026] Figure 1 This is a flowchart of a laser shock strengthening method for the edge structure of metallic materials proposed in this invention;

[0027] Figure 2 This is a schematic diagram of the laser shock strengthening principle in the prior art under normal conditions of a laser shock strengthening method for edge structures of metallic materials proposed in this invention.

[0028] Figure 3 This is a schematic diagram of the laser shock strengthening method for adjusting the state of the edge structure of a metal material edge structure proposed in this invention.

[0029] Figure 4 This is a residual stress distribution diagram of the edge structure after laser shock strengthening, which is a laser shock strengthening method for edge structures of metallic materials proposed in this invention, under adjusted state. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0031] refer to Figure 1 A laser shock strengthening method for the edge structure of a metallic material, comprising:

[0032] S1. Determine the type and size of the edge structure of the metal material. The type and size of the edge structure of the metal material include the in-plane normal direction of each position of the edge structure of the metal material and the size of the transition fillet or chamfer of the two curved surfaces.

[0033] In this embodiment, the type of edge structure of the metal material in S1 is rounded corner or chamfer, and the size of the edge structure of the metal material is the rounded corner radius or chamfer width.

[0034] S2. Based on the service status of the edge structure, divide the two adjacent planes of the edge structure into a primary strengthening surface and a secondary strengthening surface, and calculate the orientation relationship between the two strengthening surfaces.

[0035] The service condition of a metallic material's edge structure refers to the various losses and wear phenomena it experiences during long-term use. This includes the effects of multiple factors such as chemical, physical, and mechanical changes within the material itself. These factors lead to a gradual decrease in the material's strength, hardness, toughness, corrosion resistance, and other properties, ultimately resulting in material failure.

[0036] In this embodiment, in S2, the primary strengthening surface is taken as the first strengthening surface and the secondary strengthening surface is taken as the second strengthening surface, and the orientation relationship between the first strengthening surface and the second strengthening surface is calculated.

[0037] S3. Based on the orientation relationship obtained in S2, take the bisector of the angle between the normals of the two planes as the normal of the edge face to determine the position of the edge face.

[0038] In this embodiment, the edge surface in S3 includes the edge fillet tangent or chamfer plane, and the angle bisector of the angle between the normals n1 and n2 of the two planes is taken as the normal of the edge surface.

[0039] S4. Determine the laser shock strengthening power density based on the material properties of the edge structure. Determine the shock spot radius based on the laser energy range of the equipment and the size of the transition fillet or chamfer between the two curved surfaces. The shock spot radius must be ≥3 * the transition fillet or chamfer between the two curved surfaces.

[0040] S5. The distance between the edge of the impact spot and the edge surface on the two curved surfaces at the edge structure is optimized by numerical simulation method.

[0041] In this embodiment, the edge of the impact spot in S5 is a line where the edge structure intersects with the two side planes, and the distance between them is ≥1mm.

[0042] S6. Set the laser shock strengthening process parameters, attach the absorption protective layer to the strengthening area of ​​the main strengthening surface, and confirm that the absorption protective layer completely covers the edge of the edge structure to complete the laser shock strengthening process of the main strengthening surface.

[0043] In this embodiment, the laser shock strengthening process parameters in S6 include laser energy, spot diameter, overlap rate, constraint layer, and beam incident direction, and the absorption protective layer is black tape or aluminum foil.

[0044] S7. Determine the laser shock strengthening power density and distance of the secondary strengthening surface according to S6, attach an absorption protective layer to the strengthening area of ​​the secondary strengthening surface, and confirm that the absorption protective layer completely covers the edge of the edge structure to complete the laser shock strengthening process of the secondary strengthening surface.

[0045] S8. Determine the size of the reinforcement area at the edge position based on the distance between the main reinforcement surface and the secondary reinforcement surface. Attach an absorption protective layer to the edge position and confirm that the absorption protective layer completely covers the reinforcement area at the edge position. Perform laser shock reinforcement on the edge position according to S6 and S7.

[0046] In this embodiment, in step S8, an absorption protective layer is pasted at the edge position and it is confirmed that the absorption protective layer completely covers the reinforcement area at the edge position. The laser shock reinforcement direction of the edge transition rounded corner or chamfer area is n3, where n3 = n1 + n2.

[0047] Example 1:

[0048] refer to Figures 2-3 In this embodiment, since titanium alloy is one of the main materials for manufacturing structural components in the aerospace field, the edge structure of TC4 titanium alloy material is used as the laser shock strengthening object. The edge structure is a rounded corner structure with an R0.5mm radius. The rounded corner side surface is the first strengthening surface P1, and the upper surface is the second strengthening surface P2.

[0049] The angle between surfaces P1 and P2 is a right angle. The bisector of the angle between the normals of the two surfaces is taken as the normal to the edge surface P3. Surface P3 is tangent to the cylindrical surface of the rounded structure and has an angle of 45 degrees with both surfaces P1 and P2.

[0050] The fillet size is r = 0.5 mm, and its circumference is 0.785 mm. A 3 mm spot diameter can completely cover the circumference of the fillet. Using the angle between surfaces P3 and P1, the 3 mm spot diameter is calculated to project onto the P1 surface along the normal direction of surface P3, resulting in an ellipse with its major axis exceeding the edge of the fillet structure by 1.62 mm. Based on the preferred distance range, the preferred distance between the reinforcement region on surface P1 and the edge of the fillet is calculated to be 1 mm, thus determining the location of the laser shock reinforcement region.

[0051] Based on the mechanical properties of TC4 titanium alloy, the laser shock peening process parameters are designed as follows: laser energy 6J, water as the constraint layer, 50% overlap, one shock, and the laser beam incident direction along the normal to the P1 surface. Black tape is used as the absorption protective layer; this layer is adhered to the strengthened area of ​​the P1 surface, ensuring complete coverage of the rounded corner edge, thus completing the laser shock peening of the P1 surface.

[0052] The laser shock strengthening process and optimal distance for the P2 surface are the same as those for the P1 surface, thus completing the laser shock strengthening process for the P2 surface.

[0053] After laser shock strengthening of surface P2, an absorption protective layer is attached to the cylindrical surface at the rounded corner. It is confirmed that the absorption protective layer completely covers the strengthened area of ​​the rounded corner cylindrical surface. The laser shock strengthening process parameters are the same as those of surfaces P1 and P2. The projection of the 3mm spot diameter onto the rounded corner cylindrical surface on surface P3 can completely cover the R0.5mm rounded corner. Therefore, with the normal direction of surface P3 as the incident direction of the laser beam, laser shock strengthening is performed on the rounded corner cylindrical surface to complete the laser shock strengthening process of the edge structure.

[0054] refer to Figure 4 The residual stress distribution on both sides of the edge surface after laser shock strengthening of TC4 titanium alloy was obtained by simulation software using ABAQUS. The residual stress levels on both sides of the edge surface after strengthening using the method of the present invention are basically the same. The laser shock strengthening process of the later strengthened surface has no significant impact on the strengthening effect of the first strengthened surface, indicating that the laser shock strengthening method of edge structure proposed in this invention is effective.

[0055] This invention achieves deformation control and residual stress regulation of the edge structure by adjusting the arrangement of impact spots at the edge structure, thereby meeting the requirements for laser shock fatigue resistance modification of the edge structure.

[0056] This invention obtains the optimal distance between the edge of the impact spot and the edge on the two curved surfaces of the edge structure through numerical simulation, thereby reducing the adverse effects of the shock wave on the residual compressive stress level formed on the pre-strengthened surface during the propagation of the strengthened surface. It also improves the collapse and extrusion of the edge structure caused by the lack of constraint at the edge and the reflection of the laser-induced shock wave, optimizes the stability of the laser shock strengthening of the overall structure, and improves the service life and reliability of the structural components.

[0057] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A laser shock peening method for edge strengthening of metallic materials, characterized in that, include: S1. Determine the type and size of the edge structure of the metal material. The type and size of the edge structure of the metal material include the dimensions of the in-plane normal direction and the transition fillet or chamfer of the two curved surfaces at each position of the edge structure of the metal material. The dimensions of the edge structure of the metal material are the fillet radius or chamfer width. S2. Based on the service status of the edge structure, divide the two adjacent planes of the edge structure into a primary strengthening surface and a secondary strengthening surface, and calculate the orientation relationship between the two strengthening surfaces. S3. Based on the orientation relationship obtained in S2, take the angle bisector of the angle between the normals n1 and n2 of the two planes as the normal of the edge face to determine the position of the edge face. S4. Determine the laser shock enhancement power density based on the material properties of the edge structure, and determine the shock spot radius based on the laser energy range of the equipment and the radius of the transition fillet between the two curved surfaces or the width of the transition chamfer between the two curved surfaces; when the edge structure is a fillet, the shock spot radius is greater than or equal to three times the radius of the transition fillet between the two curved surfaces, and when the edge structure is a chamfer, the shock spot radius is greater than or equal to three times the width of the chamfer. S5. The distance between the edge of the impact spot and the edge surface on the two curved surfaces at the edge structure is optimized by numerical simulation method. S6. Set the laser shock strengthening process parameters, attach an absorption protective layer to the strengthening area of ​​the main strengthening surface, and complete the laser shock strengthening process of the main strengthening surface. S7. Determine the laser shock strengthening power density and distance of the secondary strengthening surface according to S6, and attach an absorption protective layer to the strengthening area of ​​the secondary strengthening surface to complete the laser shock strengthening process of the secondary strengthening surface. S8. Determine the size of the reinforcement area at the edge position based on the distance between the main reinforcement surface and the secondary reinforcement surface. Apply an absorption protective layer to the edge position and confirm that the absorption protective layer completely covers the reinforcement area at the edge position. The laser shock reinforcement direction of the edge transition rounded corner or chamfer area is n3, where n3 = n1 + n2. Perform laser shock reinforcement on the edge position according to S6 and S7.

2. The laser shock peening method for edge strengthening of metallic materials according to claim 1, characterized in that, In S2, the primary strengthening surface is taken as the first strengthening surface and the secondary strengthening surface is taken as the second strengthening surface, and the orientation relationship between the first strengthening surface and the second strengthening surface is calculated.

3. The laser shock peening method for edge strengthening of metallic materials according to claim 1, characterized in that, The edge surface in S3 includes the edge fillet tangent or chamfer plane.

4. The laser shock peening method for edge strengthening of metallic materials according to claim 1, characterized in that, In S5, the edge of the impact spot is a ridge structure that intersects with the two side planes, and the distance between them is ≥1mm.

5. The laser shock peening method for edge strengthening of metallic materials according to claim 1, characterized in that, The laser shock peening process parameters in S6 include laser energy, spot diameter, overlap ratio, constraint layer, and beam incident direction.

6. The laser shock peening method for edge strengthening of metallic materials according to claim 1, characterized in that, The absorbent protective layer in S6 is black tape or aluminum foil.

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