Fractal texture, design methods and processing methods

Abstract

This invention discloses a fractal texture, its design method, and its processing method. The fractal texture includes grooves processed on the surface of a substrate material using laser technology, with raised edges retained at the groove edges. First, the fractal texture is designed based on the Hilbert curve in fractal theory. The shape of the texture is established using the L-systems algorithm in CAD software, determining the step size and variation rules for each iteration step. Optimization is then performed in the software to determine the optimal number of iterations and step size. This invention can significantly improve the tribological properties of the friction pair material surface, reduce design and development costs, and substantially shorten the development cycle.

Description

Technical Field

[0001] This invention belongs to the field of tribology and relates to a textured friction reduction technology, specifically a fractal texture, design method, and processing method for damper friction pair materials. Background Technology

[0002] Dampers, as energy-consuming and stiffness-free devices, are often installed within the main structure of buildings to share the loads of vibration and wind, effectively reducing the response and damage of the main structure under dynamic loads. During installation and service, dampers are subjected to various loads, as well as corrosion from moisture and / or oil and gas media, and damage from high-frequency vibrations. Therefore, improving the drag-reducing and friction-reducing properties of damper friction pair materials is of great significance. Currently, various surface engineering techniques, such as high-current pulsed ion beam surface modification, laser cladding, ion implantation, physical vapor deposition, and laser surface texturing, have been applied to improve the wear resistance of metal surfaces.

[0003] Among various surface engineering technologies, laser surface texturing has attracted widespread attention due to its advantages such as fast processing speed, high production efficiency, and good controllability. However, in terms of damper friction pair materials, current friction reduction methods involve complex fabrication processes, high costs, and are not easily industrialized. Achieving friction and drag reduction in damper friction pairs requires a new type of surface texturing that is simple to fabricate, programmable, economical, and easy to operate. Summary of the Invention

[0004] The purpose of this invention is based on the above-mentioned problems, and proposes a fractal texture for damper friction pair materials. It can be applied to the drag reduction structure of damper friction pair materials. Because the processing protrusions are retained during the processing, the hydrodynamic pressure effect in the liquid environment is improved. Based on the fractal theory, the texture shape design is carried out, making the texture shape design more reasonable. Compared with the blank sample, the friction coefficient is reduced by more than 25%.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] On the one hand, the present invention provides a fractal texture for a damper friction pair material, including grooves processed on the surface of a substrate material by laser processing. The distribution of the grooves on the surface of the substrate material exhibits self-similarity through fractal design. During the laser processing, the grooves and the protrusions formed by laser impact at their edges together constitute eddy current grooves.

[0007] Preferably, the fractal texture is iterated 2-10 times, and after the iteration is completed, the fractal texture occupies 10-40% of the total surface area of ​​the matrix material.

[0008] Preferably, in the fractal texture, the individual step length of the groove is 1-20 mm.

[0009] Preferably, in the fractal texture, the direction of the initial groove of the fractal texture is at 60-90° to the flow direction of the substrate material surface.

[0010] Preferably, the width of the groove is 0.5-3mm.

[0011] Preferably, the trench depth is 20-200 μm. The depth is determined based on the power and number of laser processing cycles.

[0012] On the other hand, the present invention provides a design method for fractal texture of damper friction pair material, comprising the following steps:

[0013] The groove width and fractal order are determined based on the density of the fractal texture, and the number of iterations and step size are determined based on the fractal order.

[0014] Determine the set of generation rules V and the set of generation directions S, and match the generation rules and generation directions with the syntax of L-systems;

[0015] Generate rule P by selecting and combining from the set of generation rules V and the set of generation directions S;

[0016] Determine the initial state ω;

[0017] Different fractal patterns can be created by changing the generation rule P;

[0018] By comparing and analyzing different regular patterns to obtain the frictional properties of fractal textures, the optimal fractal design parameters are determined, the texture fractal design is completed, and the texture path is obtained.

[0019] Preferably, by changing the fractal design order and texture width, fractal patterns of different densities are designed and compared under different densities. The optimal fractal design parameters are obtained to obtain the frictional performance of the fractal texture, the optimal density, and the optimal fractal design parameters under that density.

[0020] Preferably, the generated direction set S includes moving forward one step, turning left 90 degrees, and turning right 90 degrees.

[0021] On the other hand, the present invention also provides a method for processing fractal textures for damper friction pair materials, comprising the following steps:

[0022] The texture path and groove width of the fractal texture are determined based on the above design method;

[0023] Based on the texture path and groove width, a laser marking machine is used to process the material to obtain a fractal texture.

[0024] This invention utilizes fractal theory to design fractal textures on the surface of a substrate material. The texture itself consists of grooves with specific regular paths. During laser processing of the grooves, protrusions are formed on both sides of the grooves due to melting. Retaining these protrusions creates eddy current grooves. In the design process, a pre-written program is used for pattern design to achieve standardization, while retaining the effective range of height of the processed protrusions. Under dry friction conditions, the processed protrusions increase the volume of wear debris stored in the texture and store the wear debris into a film between the textures, effectively reducing direct contact between friction pairs. Under liquid lubrication conditions, the processed protrusions enhance the flow of lubricating oil between the textures. There is a large pressure difference on both sides of the surface processed protrusions, forming a more obvious pressure gradient, thus making the friction coefficient exhibit good stability. In contrast, the fluid pressure difference on the polished surface is smaller, and the convergence range is smaller, proving that the processed protrusions can effectively enhance the hydrodynamic effect.

[0025] As can be seen from the above principles, the step size, number of iterations, groove depth, groove edge protrusion height, width-to-depth ratio, and liquid viscosity of fractal texture all have a significant impact on the drag reduction and friction reduction effect.

[0026] Compared with the prior art, the advantages of the present invention are as follows:

[0027] (1) The preparation method is simple and easy to implement. The experimental process only requires laser marking equipment and does not involve any organic reagents, which is in line with the green and environmentally friendly approach.

[0028] (2) The processing materials are wide-ranging and economical, and can be widely used in various material dampers.

[0029] (3) Implement modular shape design to reduce the time spent on shape modification.

[0030] (4) It achieves excellent drag reduction and friction reduction effect, with a friction coefficient reduction rate of up to 25% or more. Attached Figure Description

[0031] Figure 1 A schematic diagram of the overall path of the fractal texture in Embodiment 1 of the present invention.

[0032] Figure 2 A large schematic diagram of the cross-section of the fractal texture groove.

[0033] Figure 3 A schematic diagram of the direction of the flow and the starting segment direction of the fractal texture.

[0034] Figure 4 A comparison of friction coefficients under dry friction conditions for fractal textures in Example 1.

[0035] Figure 5 This is a comparison of friction coefficients under the condition of textured oil lubrication analyzed in Example 2.

[0036] Figure 6 This invention provides a simulation analysis of fluid velocity under liquid environment conditions using a fractal texture composed of raised grooves.

[0037] Figure 7 This invention provides a simulation analysis of fluid velocity under liquid environment conditions using a fractal texture composed of grooves without protrusions.

[0038] Figure 8 This invention provides a simulation of fluid pressure analysis using a fractal texture composed of raised grooves in a liquid environment.

[0039] Figure 9 This invention provides a simulation of fluid pressure analysis under liquid environment conditions using a fractal texture composed of grooves without protrusions.

[0040] 100 - Damper friction pair matrix material, 200 - Groove, 300 - Protrusion, 400 - Fractal texture, 410 - Starting section. Detailed Implementation

[0041] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0042] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0043] This invention provides a fractal texture for a damper friction pair material, comprising grooves laser-processed on the surface of a substrate material. The distribution of these grooves on the substrate material surface exhibits self-similarity through fractal design. During laser processing, the grooves and the protrusions formed at their edges due to laser impact collectively constitute vortex grooves. By forming vortex grooves, this invention enhances the hydrodynamic pressure effect in a liquid environment, resulting in a significant reduction in the coefficient of friction.

[0044] After the grooves are machined, they are not ground, and the raised edges of the grooves are retained. Under liquid environment conditions, the textured raised edges can enhance the hydrodynamic pressure effect. Simulation experiments show the following results: Figures 6 to 9 As shown in the figure, the unpolished sample retains the machined protrusions, which enhances the flow of lubricating oil between the textures. There is a large pressure difference on both sides of the machined protrusions, forming a more obvious pressure gradient, which makes the friction coefficient exhibit good stability. In contrast, the fluid pressure difference on the polished surface is smaller, and the convergence range is smaller, proving that the machined protrusions can effectively enhance the hydrodynamic effect.

[0045] To further reduce the friction coefficient, this invention performs fractal design on the grooves to obtain better fractal design parameters. Specifically, this invention provides a fractal texture design method, using the L-systems algorithm to design the surface fractal texture. The core principle of the algorithm is repeated iterative rewriting, that is, first defining the initial shape structure, then rewriting the original shape structure according to existing rules, iterating a certain number of times to generate a shape structure that meets the expectations.

[0046] L-systems are generally defined as: G = (V, S, ω, P), where V is the set of generation rules, S is the set of generation directions, ω is the initial state, and P is the generation rules.

[0047] The design methodology includes the following steps:

[0048] S1. Determine the groove width and fractal order based on the density of the fractal texture, and determine the number of iterations and step size based on the fractal order;

[0049] First, the surface of the substrate material is divided into cells with an area of ​​1 x 1 mm. Based on the density of the fractal texture, the order of application is selected. Each order represents a certain range of density. For example, the area ratio of the first-order fractal texture is 1-5%, the area ratio of the second-order fractal texture is 5-20%, and so on. The initial step size is determined when selecting the order. Then, the cells are connected to the material surface to form a complete pattern. The density range of each order is determined by the groove width and can be finely adjusted within a certain range.

[0050] S2. Determine the set of generation rules V and the set of generation directions S, and match the generation rules and generation inverses with the syntax of L-systems; for example, the set of generation rules V includes two types, L and R, with the following specific meanings:

[0051] L represents: Draw a cup-shaped broken line with the opening facing upwards. The height of the cup is equal to the diameter of the bottom. The small dots and arrows on the broken line represent the starting point and direction of the line, respectively.

[0052] R represents: Draw a cup-shaped broken line with the opening facing downwards. The height of the cup is equal to the diameter of the bottom. The small dots and arrows on the broken line indicate the starting point and direction of the line, respectively.

[0053] For example, the generated direction set S includes three types: "F", "+", and "-". "F" means to move forward one step, "+" means to turn 90° to the right, and "-" means to turn 90° to the left.

[0054] S3. Select and combine from the set of generation rules V and the set of generation directions S to obtain generation rule P;

[0055] For example, the generation rule set V, L, can be expressed in the language of L-systems functions as: -RF+LFL+FR-;

[0056] The generation rule set V contains R expressed in the language of L-systems functions as: -LF+RFR+FL-.

[0057] S4. Determine the initial state ω; for example, ω = L;

[0058] S5. Create different fractal patterns by changing the generation rule P;

[0059] S6. By comparing and analyzing different regular patterns to obtain the frictional properties of fractal textures, determine the optimal fractal design parameters, complete the texture fractal design, and obtain the texture path.

[0060] For example, at least three fractal patterns can be combined to obtain the fractal texture with the closest frictional performance.

[0061] Based on the above design, the fractal design order can be changed, and the optimal fractal design parameters under different orders can be compared to obtain the frictional performance of the fractal texture, thus obtaining the optimal order and the optimal fractal design parameters under that order.

[0062] Example 1

[0063] A fractal texture for a damper friction pair material includes a damper friction pair matrix material and an array of grooves processed on the surface of the damper matrix material. The groove density is 30% (groove area as a percentage of the surface area of ​​the damper matrix material) and the groove width is 0.5 mm.

[0064] like Figure 1 As shown, the fractal groove is a self-similar broken line. Due to the burning impact of laser processing, protrusions (about 0.1 mm in height) are formed on both sides of the groove, so that the cross-section of the groove presents a shape with protrusions at both ends and concave in the middle.

[0065] Through the above fractal design, the single step size of the texture is 1mm, the number of iterations is three, each iteration process has 10 steps and each step has a 90° rotation; the fractal texture is selected to be distributed in an array on the surface of the substrate material, the array method is a row and column array; the array density is 30%; finally, the groove width and texture path are obtained.

[0066] The tip direction (edge ​​direction of the fan-shaped column) of the initial section of the trench forms a 90° angle with the flow direction of the substrate material surface. For example... Figure 3 As shown, the arrows indicate the direction of fluid flow relative to the surface of the substrate material.

[0067] The texture path and groove width obtained above are defined on the surface of the damper using CAD, imported into the laser processing equipment, and laser processing is performed on the material surface, with two processing times.

[0068] It should be noted that, Figure 1 The base material of the damper is planar, but in practice, the base material is selected based on the actual shape. Figure 1 This diagram is only intended to illustrate the distribution of grooves in the substrate material and does not imply that they can only be placed on the surface of planar structures.

[0069] (1) Preparation of fractal texture

[0070] The laser marking machine is used to process the fractal path. The processing parameters are: linear speed 500mm / s, processing power 4J, laser frequency 30kHz, and processing times 2.

[0071] (2) Friction Reduction Measurement Method

[0072] A pin-plate rotational friction test was conducted on the Rtec friction and wear testing machine: a PTFE (polytetrafluoroethylene) pin with a diameter of 6.35 mm and a length of 19 mm was subjected to reciprocating friction with a 316L stainless steel disc with a length of 30 mm, a width of 10 mm, and a thickness of 5 mm.

[0073] Test conditions: Load 40N, frequency 4Hz, time 30min

[0074] (3) Comparative analysis of friction reduction results

[0075] Compared with the unwoven 316L stainless steel sample, the coefficient of friction was reduced by 23.14%.

[0076] Its coefficient of friction is, for example Figure 4 As shown.

[0077] Example 2

[0078] A fractal texture for a damper friction pair material includes a damper friction pair matrix material and an array of grooves processed on the surface of the damper matrix material. The groove density is 20% (as a percentage of the surface area of ​​the damper matrix material) and the groove width is 0.5 mm.

[0079] like Figure 4 As shown, the groove is a self-similar polygonal line, and its cross-section shows a shape with convex ends and a concave middle.

[0080] Through the above fractal design, the single step size is 3mm, the number of iterations is two, each iteration process has 10 steps and each step involves a 90° rotation; the fractal texture is selected to be distributed in an array on the surface of the substrate material, and the array method is a row and column array; the array density is 20%.

[0081] The tip of the initial section of the trench forms a 90° angle with the flow direction on the substrate material surface. For example... Figure 3 As shown, the arrows indicate the direction of fluid flow relative to the surface of the substrate material.

[0082] The texture path and groove width obtained above are defined on the surface of the damper using CAD, imported into the laser processing equipment, and laser processing is performed on the material surface, with two processing times.

[0083] (1) Preparation of drag-reducing and friction-reducing biomimetic textures

[0084] The laser marking machine was used for processing, with the following parameters: linear speed 500mm / s, processing power 4J, laser frequency 30kHz, and processing times 2.

[0085] (2) Friction Reduction Measurement Method

[0086] A pin-plate rotational friction test was conducted on the Rtec friction and wear testing machine: a PTFE (polytetrafluoroethylene) pin with a diameter of 6.35 mm and a length of 19 mm was subjected to reciprocating friction with a 316L stainless steel disc with a length of 30 mm, a width of 10 mm, and a thickness of 5 mm.

[0087] Test conditions: Load 40N, frequency 4Hz, time 30min, PAO8 oil lubrication.

[0088] (3) Comparative analysis of friction reduction results

[0089] Compared with the unwoven 316L stainless steel sample, the coefficient of friction was reduced by 26.49%.

[0090] Its coefficient of friction is, for example Figure 5 As shown.

[0091] In summary, this invention proposes a fractal texture for damper friction pair materials. Based on fractal theory, a drag-reducing and friction-reducing fractal texture is laser-processed on the material surface. The area of ​​the fractal texture accounts for 10-40%. This invention uses an LS system for fractal texture design. The preparation method of the drag-reducing and friction-reducing fractal texture involves setting the required density, number of iterations, step size of a single iteration, and rotation angle in CAD, and retaining processing protrusions during processing to enhance the hydrodynamic pressure effect of the textured surface in a liquid environment. Compared with a blank sample, the friction coefficient is reduced by more than 25%. This biomimetic texture preparation method is simple and easy to implement. The experimental process only requires laser processing equipment and does not involve any organic reagents, conforming to the green and environmentally friendly approach, and can be widely used in damper fractal textures.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A design method for fractal texture of friction pair material in dampers, characterized in that, The fractal texture includes grooves processed on the surface of a substrate material by laser processing. The distribution of the grooves on the substrate material surface exhibits self-similarity through fractal design. During the laser processing, the grooves and the protrusions formed at their edges by laser impact together constitute vortex grooves. The fractal texture design method is characterized by the following steps: The groove width and fractal order are determined based on the density of the fractal texture, and the number of iterations and step size are determined based on the fractal order. Determine the set of generation rules V and the set of generation directions S, and match the generation rules and generation directions with the syntax of L-systems; Generate rule P by selecting and combining from the set of generation rules V and the set of generation directions S; Determine the initial state ω ; Different fractal patterns can be created by changing the generation rule P; By comparing and analyzing different regular patterns to obtain the frictional properties of fractal textures, the optimal fractal design parameters are determined, the texture fractal design is completed, and the texture path is obtained.

2. The design method for fractal texture of damper friction pair material according to claim 1, characterized in that, The fractal texture grooves are iterated 2-10 times. After the iteration is completed, the fractal texture occupies 10-40% of the total surface area of ​​the matrix material.

3. The design method for fractal texture of damper friction pair material according to claim 1, characterized in that, In the fractal texture, the individual step length of the groove is 1-20 mm.

4. The design method for fractal texture of damper friction pair material according to claim 1, characterized in that, In the fractal texture, the direction of the initial groove of the fractal texture is at 60-90° to the flow direction of the substrate material surface.

5. The design method for fractal texture of damper friction pair material according to claim 1, characterized in that, The width of the groove is 0.5-3mm.

6. The design method for fractal texture of damper friction pair material according to claim 1, characterized in that, By changing the fractal design order and comparing the optimal fractal design parameters at different orders, the frictional properties of the fractal texture can be obtained, as well as the optimal order and the optimal fractal design parameters at that order. The density of the fractal texture is redefined based on the optimal order and the groove width.

7. The design method for fractal texture of damper friction pair material according to claim 1, characterized in that, The generated direction set S includes moving forward one step, turning left 90 degrees, and turning right 90 degrees.

8. A method for processing fractal textures for damper friction pair materials, characterized in that, Includes the following steps: The design method according to any one of claims 1-7 determines the texture path and groove width of the fractal texture; Based on the texture path and groove width, a laser marking machine is used to process the material to obtain a fractal texture.

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