Design method for high-bearing-capacity low-friction friction pair with self-repairing super-slippery surface

Abstract

Disclosed in the present invention is a design method for a high-bearing-capacity low-friction friction pair with a self-repairing super-slippery surface. The method comprises: S1, designing a dynamic pressure groove bottom of a friction pair to be a super-slippery surface; S2, designing micro-channels of the groove bottom; S3, designing outer-side lubricant supply and recovery channels; and S4, applying shear stress to the super-slippery surface and a fluid interface. The super-slip modification of the dynamic pressure groove bottom can increase the aggregation speed of a fluid in a groove to a groove root, improve the dynamic pressure of the fluid, and reduce the friction energy consumption. For a sliding block friction pair, it can be obtained through experiments that the bearing capacity of a liquid membrane can be increased by 252.66% and the viscous friction force is reduced by 19.98%.

Description

A design method for high-load, low-friction friction pairs with self-repairing super-slip surfaces Technical Field

[0001] The present invention belongs to the technical field of friction pair design, and in particular relates to a design method for a high-load, low-friction friction pair with a self-repairing super-slip surface. Background Art

[0002] Improving the load-bearing capacity of friction pairs and reducing shear friction losses have always been the direction of continuous efforts in the field of tribology. When studying the performance of friction pairs, people often assume that there is no slip at the fluid-solid interface in the micro-gap. However, boundary slip will occur between fluid molecules and solid surfaces due to the poor wettability of the surface. Generally, both hydrophobic and hydrophilic surfaces will produce boundary slip, and the amount of slip is generally at the micro-nano scale. For friction pairs, once the boundary slip changes, the load-bearing capacity, friction characteristics, and flow field flow characteristics will also change accordingly. Some data show that generating and increasing boundary slip is an important means to increase fluid flow rate and improve the efficiency of micro-nano fluid systems at the micro-nano scale. Therefore, many scholars have improved the load-bearing capacity or reduced friction losses by designing the sliding surface of the friction pair. The results show that the combination of slip and texture design can achieve better tribological performance. Regarding the preparation of large slip surfaces, some researchers believe that these can be achieved through hydrophobic design: first, making the surface extremely smooth, allowing water to generate slip lengths of 10nm-2μm; second, designing micro- and nano-textures on the surface. For example, using photolithography and chemical deposition techniques to create micro- and nano-textured superhydrophobic surfaces, the largest slip length to date (400μm) has been achieved. However, both methods struggle to achieve macroscopic slip. Therefore, Harvard University proposed injecting a low-surface-energy lubricant into the micro- and nano-scale voids of a roughened solid surface, replacing the gas layer. This method resulted in a superslippery surface with significant slip (Slippery Liquid-Infused Porous Surface, or SLIPS). This method is currently the mainstream approach for preparing liquid superslippery surfaces, but it suffers from the problem of severe loss of lubricant in the hydrophobic layer, leading to surface failure. Researchers have subsequently constructed solid superslippery surfaces, but the former is a liquid-liquid interface, while the latter is a solid-liquid interface, resulting in slower slip speeds. Furthermore, studies have shown that utilizing cavitation (the continuous generation of a gas layer between the solid and liquid) in the friction pair liquid film can increase boundary slip. Compared with the resident gas layer within the micro-nanostructure, this cavitation gas layer can exist for a long time during normal operation of the device and can also reduce the manufacturing cost of the liquid-repellent surface, which may be a promising direction; however, for now, how to extend the normal service life of SLIPS in various fields remains a cutting-edge hot issue. Technical issues

[0003] The purpose of the present invention is to design a high-load, low-friction friction pair design method with a self-repairing super-slip surface, which can also prevent the loss of liquid lubricant when achieving a super-slip state. Technical Solutions

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A method for designing a high-load, low-friction friction pair with a self-repairing super-slip surface, characterized in that: the method is as follows:

[0006] S1: The bottom of the dynamic pressure groove of the friction pair is designed to be a super-slip surface

[0007] The bottom of the dynamic pressure groove on the static surface of the friction pair is roughened. After the roughening, the solid surface has micro-nanoscale gaps. Low surface energy lubricant is injected into the gaps. After the static surface groove bottom undergoes the above-mentioned super-slip modification, the liquid medium molecules between the liquid film and the static surface can move freely along the static surface. That is, the slip speed approaches the speed of the dynamic surface, and the slip length approaches positive infinity, achieving a super-slip state.

[0008] S2: Design of micro-channels at the bottom of the groove

[0009] A number of micro-channels are evenly opened in the area with the same fluid film pressure, temperature and speed in the friction pair stationary part, which are connected to the bottom of the dynamic pressure groove. The external lubricant passes through the micro-channels, which can provide real-time quantitative lubricant replenishment to the super-slip surface.

[0010] S3: Design of external lubricant supply and recovery channels

[0011] The supply channel connects the micro-pores with the external oil storage tank, and the recovery channel connects the tank bottom with the micro-pores. Both the supply and recovery channels adopt Tesla valve structure.

[0012] S4: Shear stress applied to the interface between superslippery surface and fluid

[0013] By using temperature gradients, magnetic fields, electric fields, etc., shear stress is applied to the fluid to increase the carrying capacity, reduce friction, and maintain super-lubricity.

[0014] Furthermore, the super-slip surface design in S1 can also be achieved by preparing a porous surface, that is, plating a porous coating on the bottom of the original groove of the friction pair to increase the surface roughness.

[0015] Furthermore, the low surface energy lubricant is specifically a solution prepared by mixing lauric acid and silicone oil in a certain ratio. Of course, the low surface energy lubricant is not limited to the above method.

[0016] Furthermore, in S2, when the super-smooth surface lubricant decreases, the lubricant on the outside of the micro-channel moves toward the bottom of the groove under the action of force, and quickly spreads on the surface after reaching the bottom of the groove, thereby achieving rapid replenishment; if the super-smooth surface lubricant is excessively replenished due to external interference, the micro-channel will quickly recover the excess lubricant; if the distribution of the super-smooth surface lubricant does not change, the micro-channel is in a dormant state.

[0017] Furthermore, the supply channel in S3 is an external oil storage tank that enters the micro-pore through a Tesla valve structure in one direction, and the recovery channel is a micro-pore that enters the tank bottom in one direction through a Tesla valve structure. Beneficial effects

[0018] Based on the above invention method, the following beneficial effects can be obtained:

[0019] The super-slip modification of the hydrodynamic groove bottom accelerates the flow of fluid toward the groove root, increasing fluid dynamic pressure while reducing frictional energy consumption. Experiments on the slider friction pair have shown that the fluid film load-bearing capacity can be increased by 252.66% while reducing viscous friction by 19.98%.

[0020] Under the continuous "scouring" of the complex flow field, the liquid lubricant in the super-smooth layer at the bottom of the groove will be lost, resulting in problems such as the gradual deterioration of the super-smooth surface performance. Through the unique design of the micro-channel, the super-smooth surface lubricant is replenished in real time and quantitatively. That is, when the super-smooth surface lubricant decreases, the lubricant on the outside of the micro-channel moves to the bottom of the groove under the action of a certain design force, and quickly spreads on the surface after reaching the bottom surface of the groove, realizing rapid replenishment; if the super-smooth surface lubricant is excessively replenished due to external interference, the micro-channel will quickly recover the excess lubricant; if the distribution of the super-smooth surface lubricant does not change, the micro-channel is in a dormant state.

[0021] The Tesla valve's space-saving and one-way conduction features are used to actively regulate the process of lubricant being replenished from the storage tank to the bottom of the tank or flowing back from the bottom of the tank to the storage tank.

[0022] Apply shear stress τ at the interface between the super-sliding groove bottom and the liquid film in the opposite direction (-Y) of the moving surface 液 The bearing capacity can be further increased and the friction can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of different slip conditions at the friction pair interface.

[0024] Figure 2 is a structural diagram of a super-slippery surface.

[0025] Figure 3 is a flow chart of lubricant replenishment (C) and recovery (E).

[0026] Figure 4 shows the structure of a combined Tesla two-way valve.

[0027] FIG5 is a diagram showing the shear stress applied on the fluid surface at the bottom of the groove area in the opposite direction to the direction of motion of the dynamic surface.

[0028] Figure 6 is a structural diagram of the three-dimensional model. Best Mode for Carrying Out the Invention

[0029] The present invention will be further described below with reference to the accompanying drawings:

[0030] As shown in FIG1-6 , a method for designing a high-load, low-friction friction pair with a self-repairing super-slip surface is characterized by:

[0031] S1: The bottom of the dynamic pressure groove of the friction pair is designed to be a super-slip surface

[0032] The bottom of the dynamic pressure groove on the static surface of the friction pair is roughened. After the roughening, the solid surface has micro-nanoscale gaps. Low surface energy lubricant is injected into the gaps. After the static surface groove bottom undergoes the above-mentioned super-slip modification, the liquid medium molecules between the liquid film and the static surface can move freely along the static surface. That is, the slip speed approaches the speed of the dynamic surface, and the slip length approaches positive infinity, achieving a super-slip state.

[0033] The above-mentioned super-slip surface design can also be formed by a porous surface method, that is, a porous coating is plated on the bottom of the original groove of the friction pair to increase the surface roughness;

[0034] The low surface energy lubricant is specifically a solution prepared by mixing lauric acid and silicone oil in a certain ratio.

[0035] S2: Design of micro-channels at the bottom of the groove

[0036] A number of micro-channels are evenly opened in the area with the same fluid film pressure, temperature and speed in the friction pair stationary part, which are connected to the bottom of the dynamic pressure groove. The external lubricant passes through the micro-channels, which can provide real-time quantitative lubricant replenishment to the super-slip surface.

[0037] When the lubricant on the super-smooth surface decreases, the lubricant on the outside of the micro-channel moves toward the bottom of the groove under the action of force, and quickly spreads on the surface after reaching the bottom of the groove, achieving rapid replenishment; if the super-smooth surface lubricant is excessively replenished due to external interference, the micro-channel will quickly recover the excess lubricant; if the distribution of lubricant on the super-smooth surface does not change, the micro-channel is in a dormant state.

[0038] S3: Design of external lubricant supply and recovery channels

[0039] The supply channel connects the micro-pores with the external oil storage tank, and the recovery channel connects the bottom of the tank with the micro-pores. Both the supply and recovery channels adopt Tesla valve structures; the supply channel is the external oil storage tank entering the micro-pores in one direction through the Tesla valve structure, and the recovery channel is the micro-pores entering the bottom of the tank in one direction through the Tesla valve structure.

[0040] S4: Shear stress applied to the interface between superslippery surface and fluid

[0041] By using temperature gradients, magnetic fields, electric fields, etc., shear stress is applied to the fluid to increase the carrying capacity, reduce friction, and maintain super-lubricity.

[0042] The inventors further explain the relevance and effects of each step in the above method:

[0043] The ultra-slip surface in the present invention is located at the bottom of the dynamic pressure groove of the friction pair (micro-electromechanical system, dynamic pressure bearing, liquid film seal, etc.) (the dynamic pressure groove is opened on the static surface, the groove can be an open groove or a closed groove, and the groove shape is not limited). It can lock the low surface energy liquid-repellent layer well and completely avoid the wear of the functional surface, thereby reducing manufacturing costs and extending service life.

[0044] As shown in FIG2 , the method for preparing a super-slippery surface (but not limited to) is: injecting a low surface energy lubricant (e.g., a solution prepared by mixing lauric acid and silicone oil in a certain ratio) into the micro-nanoscale voids of a roughened solid surface;

[0045] The preparation methods of porous surfaces include (but are not limited to): ① plating a porous coating (such as SiO2, etc.) on the bottom of the original groove of the friction pair; ② increasing the surface roughness through advanced manufacturing technology (such as physical and chemical deposition, laser processing, etc.).

[0046] Both of the above-mentioned super-slippery surfaces must have strong adsorption properties for lubricants, that is, the supplementary lubricant can expand extremely quickly in the porous material layer and be firmly adsorbed in the micro-nanoscale gaps of the super-slippery surface.

[0047] Figure 1 shows the schematic diagrams of three boundaries: no-slip diagram 1 (a), general slip diagram 1 (b) and super slip diagram 1 (c), where V is the velocity of the moving surface, h0 is the film thickness in the non-groove area, and h g is the groove depth, L s is the slip length, v s For the present invention, the specific method is to keep the friction pair moving surface and the liquid film tightly adhered to each other, and there is no slip at the fluid-solid interface, that is, v s =0,L s = 0, the static surface groove bottom is super-slip modified, and the liquid medium molecules between the liquid film and the static surface can move freely along the static surface, that is, v s →V,L s →+∞, temporarily called super slip, under this design, the liquid film can maintain its integrity Figure 1 (c).

[0048] Based on these design improvements, numerical calculations have demonstrated that the super-slip modification of the dynamic pressure groove bottom accelerates the convergence of fluid within the groove toward the groove root, increasing fluid dynamic pressure while simultaneously reducing frictional energy consumption. For the slider friction pair, it was found that within the studied range, the fluid film bearing capacity could be increased by 252.66%, while simultaneously reducing viscous friction by 19.98% (referenced to Utility Patent 202121515071.7 and Invention Patent 202210664850.6).

[0049] Due to the existence of the dynamic pressure groove and the vibration of the system, the velocity and pressure distribution in the micro-gap flow field will be uneven, and the friction of the friction pair and the high viscosity of the medium will cause the flow field temperature to rise. Under the continuous "scouring" of the complex flow field, the liquid lubricant in the super-slip layer at the bottom of the groove will be lost, resulting in the gradual deterioration of the super-slip surface performance or even failure. In light of this, and taking into account the varying amounts of lubricant lost in different areas, the present invention incorporates several microchannels, spaced apart from each other and located in regions with uniform pressure, temperature, and velocity, on the stationary component of the friction pair. These microchannels connect to the bottom of the dynamic pressure groove. Lubricant from the outside of the microchannels flows through these microchannels, enabling real-time, quantitative replenishment of lubricant to the superslippery surface. Specifically, when lubricant on the superslippery surface decreases, lubricant from the outside of the microchannels, under the action of a designed force, moves toward the groove bottom. Once there, it rapidly spreads across the groove bottom surface (the groove bottom surface is designed to be superwettable for lubricant, with a contact angle as close to zero as possible), achieving rapid replenishment. If excessive lubricant is supplied to the superslippery surface due to external interference, the microchannels quickly recover the excess lubricant. If the lubricant distribution on the superslippery surface remains unchanged, the microchannels enter a dormant state. Pressure, temperature, electricity, magnetism, and other forces can be used to enhance lubricant supply or recovery through the microchannels. In practical applications, precise calculations based on the selected operating mechanism can be performed to determine the design parameters of each structure. Taking the super-slip surface of roughness + lubricant as an example, the lubricant supply and recovery process is as follows (as shown in Figure 3):

[0050] ① Normally operating super-slippery surface (A in Figure 3) → Super-slippery surface after lubricant loss (B in Figure 3) → Micro-channel quickly replenishes lubricant (Figure 3C, where I and G are the connection points between the combined Tesla two-way valve and the lubricant storage tank, and the structure is shown in Figure 4).

[0051] ② Normally operating super-slip surface (A in Figure 3) → External interference, excessive lubricant supply (D in Figure 3) → Micro-channel quickly recovers excess lubricant (E in Figure 3, where I and G are the connection points between the combined Tesla two-way valve and the lubricant storage tank, and the structure is shown in Figure 4).

[0052] Taking advantage of the Tesla valve's space-saving and one-way conduction features, the present invention proposes a combined Tesla two-way valve structure (Figure 4) for actively regulating the process of lubricant replenishment from the storage tank to the tank bottom or backflow from the tank bottom to the storage tank. Its specific working principle is as follows:

[0053] ① Lubricant replenishment process: When the lubricant loss on the super-slip surface is large, the lubricant in the storage pool is replenished smoothly along the J→I channel, while the H→G channel is blocked.

[0054] ② Lubricant recovery process: When the lubricant is excessive, the lubricant at the bottom of the groove flows back smoothly along the G→H channel, while the I→J channel is blocked.

[0055] Applying shear stress on the interface between the super-slippery surface and the fluid, that is, applying shear stress on the fluid, the interface still remains super-slip, which can be achieved by means of temperature gradient, magnetic field, electric field, etc. Previous numerical calculations have shown that applying shear stress τ on the interface between the super-slippery groove bottom and the liquid film in the opposite direction (-Y) of the moving surface 液 (Figure 5) can further increase the load-bearing capacity and reduce friction.

[0056] Finally, based on the above method, a high-load, low-friction friction pair model of a self-repairing super-slip surface was obtained (as shown in Figure 6). The middle cylinder is the rotating shaft, and the outside of the rotating shaft is covered with an annular static ring. The dynamic pressure groove of the sealing end face of the static ring is roughened, and the solid surface after roughening has micro-nanoscale gaps. Low surface energy lubricant is injected into the gaps, and several micro-channels are evenly opened in the area with the same liquid film pressure, temperature, and velocity at the bottom of the dynamic pressure groove of the static ring end face. The outer oil reservoir is connected to the micro-channel through the Tesla two-way valve structure, and the liquid storage ring groove 1 is connected to the liquid storage ring groove 2 at the same time, which is used to actively adjust the process of lubricant replenishment from the oil reservoir to the bottom of the groove or backflow from the bottom of the groove back to the oil reservoir.

[0057] The above are all preferred embodiments of the present invention. For ordinary technicians in this technical field, without departing from the principle of the present invention, various equivalent modifications to the present invention are within the scope of protection of the claims attached to this application.

Claims

1. A method for designing a high-load, low-friction friction pair with a self-repairing super-slip surface, characterized in that: The method is as follows: S1: The bottom of the dynamic pressure groove of the friction pair is designed to be a super-slip surface The bottom of the dynamic pressure groove of the static surface of the friction pair is roughened, and there are micro-nanoscale gaps on the solid surface after roughening. Low surface energy lubricant is injected into the gaps. After the bottom of the static surface groove is modified by the above-mentioned super-slip, the liquid medium molecules between the liquid film and the static surface can move freely along the static surface, that is, the slip speed approaches the moving speed of the dynamic surface, and the slip length approaches positive infinity, reaching a super-slip state; S2: Design of micro-channels at the bottom of the groove A number of micro-channels are evenly opened in the area with the same liquid film pressure, temperature and speed of the friction pair stationary parts, which are connected to the bottom of the dynamic pressure groove. The outer lubricant passes through the micro-channels, and the super-slip surface lubricant can be quantitatively replenished in real time. S3: Design of external lubricant supply and recovery channel The supply channel connects the micro-pores with the external oil storage tank, and the recovery channel connects the bottom of the tank with the micro-pores. Both the supply and recovery channels adopt Tesla valve structures. S4: Shear stress applied to the interface between superslippery surface and fluid By using temperature gradient, magnetic field and electric field, shear stress is applied to the fluid to increase the carrying capacity, reduce friction and maintain super lubricity.

2. A method for designing a high-load, low-friction friction pair with a self-repairing super-slip surface according to claim 1, characterized in that: The super-slip surface design in S1 can also be achieved by preparing a porous surface, that is, plating a porous coating on the bottom of the original groove of the friction pair to increase the surface roughness.

3. A method for designing a high-load, low-friction friction pair with a self-repairing super-slip surface according to claim 1 or 2, characterized in that: The low surface energy lubricant is specifically a solution prepared by mixing lauric acid and silicone oil in a certain ratio.

4. The method for designing a high-load, low-friction friction pair with a self-repairing super-slip surface according to claim 1, characterized in that: In S2, when the lubricant on the superslip surface is reduced, the lubricant on the outer side of the microchannel moves toward the bottom of the groove under the action of the force, and quickly spreads on the surface after reaching the bottom of the groove, thereby achieving rapid replenishment; If the super-smooth surface lubricant is oversupplied due to external interference, the microchannel will quickly recover the excess lubricant; if the super-smooth surface lubricant distribution does not change, the microchannel is in a dormant state.

5. The method for designing a high-load, low-friction friction pair with a self-repairing super-slip surface according to claim 1, characterized in that: The supply channel in S3 is an external oil storage tank that enters the micro-pores in one direction through the Tesla valve structure, and the recovery channel is a micro-pore that enters the bottom of the tank in one direction through the Tesla valve structure.

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