Cu-coated C core-shell particle material concentration gradient clutch friction plate and test method

Abstract

The invention discloses a Cu (at) C core-shell particle material concentration gradient clutch friction plate, a lining comprises a plurality of copper-based powder distributed in the annular direction, and the copper-based powder comprises (70-7x)% of copper powder, 7x% of Cu (at) C particles, 10% of iron powder, 5% of tin powder, 5% of nickel powder, 4% of silicon carbide, 2% of silicon dioxide, 2% of chromium powder and 2% of molybdenum powder. The invention further discloses a test method of the Cu-coated C core-shell particle material concentration gradient clutch friction plate. The test method comprises the following steps: S1, adopting the Cu-coated C core-shell particle material concentration gradient clutch friction plate as an experimental group; s2, carrying out a long-time sliding friction test, researching the radial temperature change condition of the friction pair, and researching the change of the friction torque of the friction pair; and S3, performing morphological analysis on the surface of the friction plate. The method has the advantages of local thermodynamic regulation and control, independent concentration regulation, construction of a dynamic heat balance mechanism, wide application range and the like.

Description

Technical Field

[0001] This invention belongs to the field of clutch friction plate technology, specifically relating to a Cu@C core-shell particle material concentration gradient clutch friction plate and its test method. Background Technology

[0002] During operation, friction plates are subjected to frequent high temperatures and high loads, making them prone to thermal warping. Thermal warping deformation is a geometric deformation phenomenon caused by uneven thermal stress distribution under high-temperature conditions. If the friction plates warp, the clutch may fail to engage or disengage properly, affecting the vehicle's power transmission and reducing driving comfort and safety. Furthermore, thermal warping can also cause abnormal contact between the friction plates and other components, increasing wear and consequently affecting the overall efficiency and lifespan of the clutch system.

[0003] The fundamental cause of thermal warping deformation lies in the temperature gradient within the friction pads. During braking, the relative motion between the friction pads and the mating disc converts mechanical energy into heat energy. Since the surface of the friction pads directly participates in the friction, its surface temperature rises rapidly, while the core layer, due to its limited thermal conductivity, experiences a relatively slow temperature rise. This temperature difference between the surface and core layers forms a temperature gradient along the thickness direction. Furthermore, a significant temperature gradient also forms in the radial direction (i.e., along the radius of the friction pads), with the outer diameter temperature significantly higher than the inner diameter, exhibiting a distribution characteristic that increases from the inside out.

[0004] Currently, the following methods are used to address the internal temperature gradient problem of friction pads: 1) By developing functionally graded materials (FGMs), spatial gradients of thermal expansion coefficients and thermal conductivity are achieved in the radial or thickness direction of the friction pad, thereby coordinating thermal deformation and reducing the temperature gradient. This requires full-domain material reconstruction and thermal matching through complex gradient changes, resulting in complex manufacturing processes, high costs, and difficulties in coordinating mechanical properties; 2) Introducing radial grooves, biomimetic pores, or segmented modular layouts in structural design increases the heat dissipation surface area and reduces overall warpage through local stress release mechanisms. However, this method is complex and costly; 3) Enhancing passive or active heat dissipation capabilities, such as using high-emissivity ceramic coatings to enhance infrared heat dissipation, using micro-nano structures to induce air turbulence to strengthen convective heat transfer, or integrating a liquid cooling circulation system within the brake caliper and designing centrifugal drive heat dissipation channels. This not only increases structural complexity and requires additional external equipment but also increases the risk of failure; 4) Using thermoforming and 3D printing technologies to prepare friction pads with complex gradient structures or embedded heat dissipation channels, but the mass production cost is too high. Summary of the Invention

[0005] This invention aims to provide a Cu@C core-shell particle material concentration gradient clutch friction plate and experimental method, which achieves local thermodynamic regulation by independent concentration adjustment, constructs a dynamic thermal equilibrium mechanism, and solves the problems of high cost in developing traditional functionally graded materials, complex structural design and heat dissipation manufacturing process, complex passive and active heat dissipation structures, and excessively high cost of hot pressing molding and 3D printing mass production.

[0006] Therefore, the technical solution adopted by the present invention is as follows: a Cu@C core-shell particle material concentration gradient clutch friction plate, comprising a substrate and a liner sintered and connected to the substrate, wherein the liner comprises several copper-based powders of different concentrations arranged circumferentially from the inside to the outside, and the composition of the copper-based powders by mass percentage is: (70-7x)% copper powder, 7x% Cu@C particles, 10% iron powder, 5% tin powder, 5% nickel powder, 4% silicon carbide, 2% silicon dioxide, 2% chromium powder, and 2% molybdenum powder.

[0007] As a preferred embodiment of the above scheme, the liner comprises three concentrations of copper-based powder with x values ​​of 0–2, 2–4, and 4–6, respectively.

[0008] More preferably, the inner diameter region of the liner is ~ The median diameter region of the liner is ~ The outer diameter region of the liner is ~ ;in, =85mm, =115mm~110mm, =120mm~115mm, =125mm, the size design is reasonable.

[0009] Further preferably, the three copper-based powders of different concentrations are arranged in a ring along the inner diameter region, middle diameter region, and outer diameter region of the liner in the order of relatively medium concentration, high concentration, and low concentration. Finally, the temperature distribution is relatively uniform, and the radial gradient distribution has better thermal uniformity, so that the heat is distributed more evenly inside the material. This can be used as experimental group one.

[0010] More preferably, the three copper-based powders of different concentrations are arranged in a ring along the inner diameter region, middle diameter region, and outer diameter region of the liner in the order of relatively high concentration, medium concentration, and low concentration. Finally, the temperature of the inner diameter region and the middle diameter region tends to be the same, and the temperature of the outer diameter region is the lowest. The friction coefficient of the low-concentration Cu@C friction material is significantly different from that of the medium-concentration and high-concentration friction materials, which can be used as experimental group two.

[0011] More preferably, the three copper-based powders of different concentrations are arranged in a ring along the inner diameter region, middle diameter region, and outer diameter region of the liner in the order of relatively low concentration, medium concentration, and high concentration. Finally, the temperature trend is that the middle diameter region is greater than the outer diameter region, which is greater than the inner diameter region. Since the friction coefficient of the middle diameter region is higher, it can lead to a higher temperature in the middle diameter region, thereby increasing the heat generation and heat conduction rate. This can be used as experimental group three.

[0012] A further preferred method involves adding Cu particles and 98% concentration dopamine hydrochloride to an ultrapure aqueous solution in a 5:1 ratio and stirring to oxidize the catechol portion of the dopamine to quinine, thereby polymerizing to form polydopamine PDA. After filtration, freezing, and drying, Cu@PDA particles are obtained. The Cu@PDA particles are then subjected to high-temperature heat treatment to obtain Cu@C particles.

[0013] Compared to current copper-based powder metallurgy materials for friction, which typically use graphite as a lubricant added to copper-based composites, where the carbon-copper interface can only be physically mixed and bonded, Cu@C core-shell particles are prepared using a chemical method. This allows for chemical bonding of the carbon-copper interface. Moreover, Cu@C core-shell particles have a higher density than graphite but a lower density than copper, thus solving the problem of unstable bonding caused by the large difference in material density during physical mixing of carbon and copper. This effectively enhances the interfacial bonding strength, improves product quality stability, and has high preparation efficiency.

[0014] The present invention also employs a technical solution that is, a test method for Cu@C core-shell particle material concentration gradient clutch friction plate, comprising the following steps: Step S1: The Cu@C shell core particle material concentration gradient clutch friction plate mentioned above is used as the experimental group, and a common copper-based friction plate with x=0 is set as control group one, and a friction plate containing only one concentration of copper-based powder is set as control group two. The friction plates are tested through a test bench consisting of a friction and wear tester and a temperature measurement system. Step S2: Conduct a long-term sliding friction test to study the radial temperature change of the friction pair under different speeds and pressures, and to study the change of friction torque of the friction pair under different speeds and pressures. Step S3: Before and after each long-term friction test, the surface morphology of the friction pads before and after the test is analyzed using a metallographic microscope (MMS) and a scanning electron microscope (SEM) to reveal the microstructure, wear trajectory direction and material transfer characteristics.

[0015] As a preferred embodiment of the above scheme, in step S2, tests are conducted sequentially using operating parameters of 100 r / min, 200 r / min, and 300 r / min under the same pressure, and 100 N, 200 N, and 300 N under the same rotation speed. The operating parameters are designed reasonably and conform to the actual situation.

[0016] More preferably, in step S1, the temperature measuring system includes a steel sheet that matches the size of the friction plate and is in close contact to achieve sliding motion, and a temperature sensor that is radially inserted into the steel sheet. The steel sheet is provided with no less than three temperature measuring holes at circumferential intervals, and the temperature measuring holes are respectively inserted into the inner diameter region, middle diameter region and outer diameter region corresponding to the friction plate. The measured temperature data is accurate. The steel sheet with the temperature sensor is part of the temperature measuring system, which can realize rapid testing of the friction plate.

[0017] The beneficial effects of this invention are: (1) Compared with the current methods of developing traditional functional gradient materials, designing heat dissipation in structural design, adding passive and active heat dissipation, hot pressing and 3D printing to solve the impact of thermal warping deformation of friction pads, this solution adopts local thermodynamic control, which replaces the global material reconstruction required by traditional functional gradient materials (FGMs). By adjusting the independent concentration of each annular region from the inside to the outside, the thermal expansion coefficient and thermal conductivity are optimized in a stepwise manner. It can accurately compensate for the thermal load differences in different regions. At the same time, by utilizing the friction deformation and temperature rise characteristics of the material at different radii, a dynamic thermal balance mechanism is constructed. It also effectively avoids the molding problem of complex gradient materials, has higher compatibility with traditional manufacturing processes (such as injection molding and sintering), and reduces process costs.

[0018] (2) The endogenous thermal balance mechanism achieved by setting the concentration gradient of copper-based powder in this application replaces the external heat dissipation system, which reduces the system complexity, has a wide range of applications, and matches the thermo-mechanical characteristics of each annular region, so that the heat generated by friction forms a dynamic balance in different regions. At the same time, by utilizing the coupling effect of the radius position and the centrifugal force of rotation, a synergistic mechanism between the material concentration gradient and the direction of heat flow is established, thereby eliminating the bottleneck of heat conduction.

[0019] In summary, it has advantages such as local thermodynamic regulation, independent concentration adjustment, construction of dynamic thermal equilibrium mechanism, and wide applicability. Attached Figure Description

[0020] Figure 1 This is a schematic diagram showing the temperature change of various friction plates as the rotational speed increases at different speeds. Figure 1 (a), (b), (c), (d), and (e) are schematic diagrams showing the temperature changes in the inner diameter region, middle diameter region, and outer diameter region of Control Group 2, Experimental Group 1, Experimental Group 2, Experimental Group 3, and Control Group 1 at different rotational speeds, respectively, as the rotational speed increases.

[0021] Figure 2 The bar chart shows the final temperature of the four materials (Experimental Group 1, Experimental Group 2, Experimental Group 3, and Control Group 2) at different rotation speeds.

[0022] Figure 3The temperature variation with pressure in the inner diameter region, middle diameter region, and outer diameter region of the control group material 2 is shown. Figure 3 (a), (b), and (c) show the temperature changes of the control group material in the inner diameter region, middle diameter region, and outer diameter region with pressures of 100N, 200N, and 300N, respectively.

[0023] Figure 4 This is a schematic diagram showing the temperature as a function of pressure for the material in the inner diameter region, middle diameter region, and outer diameter region of the experimental group. Figure 4 (a), (b), and (c) show the temperature changes of the material in the inner diameter region, middle diameter region, and outer diameter region of the experimental group as a function of pressures of 100N, 200N, and 300N, respectively.

[0024] Figure 5 The bar chart shows the final temperature of the inner diameter region, middle diameter region, and outer diameter region of the two materials in control group 2 and experimental group 1 under different pressures.

[0025] Figure 6 This is a schematic diagram showing the variation curves of frictional torque for control group 2 and experimental groups 1, 2, and 3 under different rotational speeds. Figure 6 (a), (b), and (c) are schematic diagrams showing the changes in friction torque of control group 2 and experimental groups 1, 2, and 3 at speeds of 100 r / min, 200 r / min, and 300 r / min, respectively.

[0026] Figure 7 The diagram shows the friction torque variation curves of control group 2 and experimental groups 1, 2, and 3 under different load conditions; Figure 7 (a), (b), and (c) are schematic diagrams showing the changes in frictional torque of control group 2 and experimental groups 1, 2, and 3 under conditions of 100N, 200N, and 300N, respectively.

[0027] Figure 8 This is an MMS image of a sintered gradient layer after a long-term rubbing test of some gradient materials.

[0028] Figure 9 This is a schematic diagram of the SEM and EDS analysis results of some gradient materials after a long-term friction test. Figure 9 (a1) and (b1) are schematic diagrams of SEM and EDS analysis results of copper-based powder gradient materials with concentrations of 3 and 5, respectively. Figure 9 (a2) and (b2) are schematic diagrams of the SEM and EDS analysis results of the concentration gradient copper-based powder materials when x is 1 and x is 3.

[0029] Figure 10 This is a partial structural diagram of a steel sheet with a temperature sensor installed.

[0030] Figure 11 This is a schematic diagram of the friction plate of a concentration gradient clutch made of Cu@C core-shell particles. Detailed Implementation

[0031] The present invention will be further described below with reference to the embodiments and accompanying drawings: Combination Figure 1 — Figure 11 As shown, a Cu@C core-shell particle material concentration gradient clutch friction plate is composed of a matrix and a liner sintered and connected to the matrix. The liner and the matrix are prepared by spark plasma sintering technology.

[0032] The material is sintered at a temperature of 800℃~950℃, with a sintering pressure of 10MPa~20MPa. The vacuum level inside the furnace is controlled at 10 during the sintering process. -1 Below Pa.

[0033] The liner is composed of several copper-based powders of different concentrations arranged in a circumferential pattern from the inside out.

[0034] The composition of the copper-based powder by mass percentage is as follows: (70-7x)% copper powder, 7x% Cu@C particles, 10% iron powder, 5% tin powder, 5% nickel powder, 4% silicon carbide, 2% silicon dioxide, 2% chromium powder, and 2% molybdenum powder.

[0035] Cu@C core-shell particles were prepared by adding Cu particles and 98% concentration dopamine hydrochloride into an ultrapure aqueous solution at a ratio of 5:1 and stirring. The catechol portion of dopamine was oxidized to quinine, thereby polymerizing to form polydopamine PDA. After filtration, freezing and drying, Cu@PDA particles were obtained. The Cu@PDA particles were then subjected to high-temperature heat treatment to obtain Cu@C particles.

[0036] The heat treatment temperature for Cu@PDA particles is 800℃~900℃.

[0037] Cu particles and dopamine hydrochloride are added to an ultrapure aqueous solution in a specific ratio and stirred for at least 72 hours.

[0038] The liner is composed of copper-based powder with three concentrations of x, namely 0-2, 2-4, and 4-6.

[0039] The inner diameter region IR of the liner is ~ The median diameter region MR of the liner is ~ The outer diameter region OR of the liner is ~ ;in, =85mm, =115mm~110mm, =120mm~115mm, =125mm.

[0040] Example 1 A test method for a concentration gradient clutch friction plate made of Cu@C core-shell particle material, the specific implementation steps of which are as follows: Step S1: The Cu@C shell-core particle material concentration gradient clutch friction plate mentioned above was used as the experimental group. The liner was composed of three concentrations of copper-based powder with x being 1, 3, and 5 respectively.

[0041] Three copper-based powders of different concentrations were arranged in a ring along the inner diameter region IR, the middle diameter region MR, and the outer diameter region OR of the substrate in the order of relatively medium concentration, high concentration, and low concentration, forming experimental group one.

[0042] Three copper-based powders of different concentrations were arranged in a ring along the inner diameter region IR, the middle diameter region MR, and the outer diameter region OR of the substrate in the order of relatively high concentration, medium concentration, and low concentration, forming experimental group two.

[0043] Three copper-based powders of different concentrations were arranged in a ring along the inner diameter region IR, the middle diameter region MR, and the outer diameter region OR of the substrate in the order of relatively low concentration, medium concentration, and high concentration, forming experimental group three.

[0044] A standard copper-based friction pad with x = 0 was set as the control group 1.

[0045] A friction pad containing only copper-based powder at a concentration of x=3 was set as the control group 2.

[0046] Friction plates are tested using a test bench consisting of a friction and wear testing machine and a temperature measurement system.

[0047] In step S1, the temperature measuring system mainly consists of a steel sheet 1 that matches the size of the friction plate and is in close contact to achieve sliding motion, and a temperature sensor 2 that is radially inserted into the steel sheet 1.

[0048] The steel sheet 1 is provided with no less than three temperature measuring holes 11 at circumferential intervals, and the temperature measuring holes 11 are respectively inserted into the inner diameter region IR, the middle diameter region MR, and the outer diameter region OR corresponding to the friction sheet.

[0049] Step S2: Conduct a long-term sliding friction test to study the radial temperature change of the friction pair under different speeds and pressures, and to study the change of friction torque of the friction pair under different speeds and pressures. In step S2, tests were conducted sequentially using operating parameters of 100 r / min, 200 r / min, and 300 r / min under the same pressure, and 100 N, 200 N, and 300 N under the same rotation speed.

[0050] Figure 1 (a), (b), (c), (d), and (e) show schematic diagrams illustrating the changes in temperature in the inner diameter region (IR), middle diameter region (MR), and outer diameter region (OR) as the rotational speed increases for control group 2, experimental group 1, experimental group 2, experimental group 3, and control group 1, respectively.

[0051] Figure 2 The final temperatures of four materials (Experimental Group 1, Experimental Group 2, Experimental Group 3, and Control Group 2) at different rotational speeds are shown.

[0052] For control group two, according to Figure 2 It can be seen that when the rotational speed increases from 100 r / min to 300 r / min, the temperature difference between the inner and outer diameters of the homogeneous material changes from 2℃~6℃ to 3℃~7℃. This is because as the rotational speed increases, the relative speed between the friction pairs accelerates, leading to an increase in the frictional heat generated per unit time.

[0053] For experimental group two, according to Figure 1 (b) It can be seen that the IR and MR temperatures in the inner diameter region and the middle diameter region of experimental group two tend to be consistent, while the OR temperature in the outer diameter region is the lowest, showing IR≈MR>OR. From Figure 2 As can be seen, when the rotational speed increases from 100 r / min to 300 r / min, the temperature difference between the inner and outer diameters of experimental group 2 changes from -6℃ to -2℃ to -10℃ to 6℃. This is because the friction coefficient of copper-based powder containing 7% Cu@C differs significantly from that of copper-based powder containing 21% Cu@C and copper-based powder containing 35% Cu@C.

[0054] For experimental group one, according to Figure 1 (c) It can be seen that the temperatures in the middle diameter region MR, inner diameter region IR, and outer diameter region OR of experimental group 1 tend to be consistent, indicating that the radial temperature distribution is relatively uniform. Figure 2 The results show that when the rotational speed increases from 100 r / min to 300 r / min, the temperature difference between the inner and outer diameters of experimental group 1 changes from -1℃ to 3℃ to -2℃ to 2℃. This indicates that the radial gradient distribution exhibits better thermal uniformity, resulting in a more uniform distribution of heat within the material.

[0055] For experimental group three, according to Figure 1 (d) It can be seen that the overall temperature trend of experimental group 3 is that the MR in the middle diameter region is greater than that in the outer diameter region, OR is greater than that in the inner diameter region, IR. Figure 2The results showed that when the rotational speed increased from 100 r / min to 300 r / min, the temperature difference between the inner and outer diameters in experimental group three changed from 0℃~4℃ to 2℃~6℃. The higher MR temperature in the middle diameter region is due to the higher coefficient of friction in this region, which leads to increased heat generation and thermal conductivity.

[0056] In summary, as the rotational speed increases, the temperature difference between the inner and outer diameters of all four materials is amplified. According to the formula... The frictional heat generated increases with increasing radius. Since the outer diameter region (OR) directly participates in friction, the heat generated in the outer diameter region (OR) is greater than that in the inner diameter region (IR), resulting in a faster temperature rise in the outer diameter region (OR). However, because the gradient material is designed with different friction coefficients in the radial direction, the temperature distribution pattern of the gradient material is significantly different from that of the homogeneous material, thus achieving a more uniform temperature distribution at different rotational speeds.

[0057] Especially in Experimental Group 1. The design mechanism of this gradient structure is as follows: the intermediate transition region, containing 35% Cu@C copper-based material, has a high thermal conductivity of 5.5 W / m·K, significantly better than other regions, which can efficiently transfer heat radially to adjacent regions, effectively avoiding local heat accumulation; at the same time, the outer diameter region OR, containing 7% Cu@C copper-based material, has a friction coefficient as low as 0.32, which can significantly reduce the heat generation rate caused by high-speed motion compared to other regions. This synergistic mechanism balances the radial temperature distribution through a dual effect: the high thermal conductivity region achieves directional heat conduction, while the low friction region suppresses the intensity of frictional heat generation.

[0058] The inner and outer diameters have the smallest temperature difference and the best temperature uniformity, therefore experimental group one has the best balanced radial temperature distribution effect.

[0059] Figure 3 The temperature variation with pressure at the inner diameter region IR, middle diameter region MR, and outer diameter region OR of the control group material is shown.

[0060] Figure 4 The temperature variation with pressure in the inner diameter region IR, middle diameter region MR, and outer diameter region OR of the material in Experiment Group 1 is shown.

[0061] Figure 5 The final temperatures of the inner diameter region IR, middle diameter region MR, and outer diameter region OR of the two materials in control group 2 and experimental group 1 under different pressures are shown.

[0062] from Figure 5It can be seen that when the pressure increases from 100 N to 300 N at 100 r / min, the temperature difference between the inner and outer diameters of the control group 2 changes from 2℃~6℃ to 0℃~4℃. For experimental group 1, the temperature difference changes from -1℃~3℃ to -3℃~1℃. At 200 r / min, the temperature difference between the inner and outer diameters of the homogeneous material in control group 2 changes from 2℃~6℃ to 9℃~13℃, while the temperature difference of the gradient material in experimental group 1 remains at -3℃~1℃. At 300 r / min, the temperature difference between the inner and outer diameters of the homogeneous material in control group 2 changes from 3℃~7℃ to 4℃~8℃. The temperature difference of the gradient material in experimental group 1 changes from -2℃~2℃ to -5℃~-1℃.

[0063] This is because the spatial variation in thermal conductivity of gradient materials allows them to more effectively regulate heat transfer. Homogeneous materials, with their uniform thermal conductivity, cannot adapt to non-uniform temperature distributions, resulting in lower heat transfer efficiency and larger temperature differences. In surface contact friction tests, heat is generated due to friction within the material. Gradient materials, due to their varying properties, can distribute frictional heat more evenly. Homogeneous materials, with their uniform properties, have uneven frictional heat distribution, easily leading to localized temperature increases and thus larger temperature differences. When pressure increases, the non-uniformity of gradient materials can better adapt to the changes in heat distribution caused by increased pressure and rotational speed, thereby resulting in a more uniform temperature distribution.

[0064] Figure 6 The graph shows the changes in friction torque for control group 2 and experimental groups 1, 2, and 3 under different rotational speeds. As can be seen from the graph, the friction torque of all four materials increases with increasing rotational speed. With increasing rotational speed, the relative rotational speed between the friction pairs accelerates, leading to the conversion of more mechanical energy into heat energy. This heat raises the temperature of the contact surfaces, causing the material surfaces to soften or partially melt, thereby increasing frictional resistance and consequently, the friction torque.

[0065] Specifically, as shown in Table 1, when the rotational speed increased from 100 r / min to 300 r / min, the frictional torque of the homogeneous material in control group 2 increased by 0.087 N·m. For the gradient material, the frictional torque of experimental group 2 increased by 0.040 N·m; experimental group 1 increased by 0.032 N·m; and experimental group 3 increased by 0.022 N·m.

[0066]

[0067] It can be seen that the gradient material exhibits high frictional stability and is not easily affected by rotational speed. This phenomenon can be explained from two aspects: the material's microstructure and the friction mechanism. First, the unique structure of the Cu@C gradient material allows it to better adapt to the deformation of the contact surface at different rotational speeds, thus maintaining a relatively stable friction system. Second, as the rotational speed increases, the heat generated at the friction interface increases, leading to an increase in the material surface temperature, which in turn affects its frictional performance.

[0068] Figure 7 The table shows the changes in frictional torque under different load conditions for control group 2 and experimental groups 1, 2, and 3. As can be seen from Table 2, when the load increases from 100 N to 300 N, the frictional torque of the homogeneous material in control group 2 increases by 1.08 N·m. For the gradient material in experimental group 2, the frictional torque increases by 0.43 N·m; for the gradient material in experimental group 1, the torque increases by 0.63 N·m; and for the gradient material in experimental group 3, the torque increases by 0.75 N·m. This indicates that the frictional torque of both homogeneous and gradient materials increases with increasing pressure.

[0069]

[0070] In gradient materials, the gradient distribution of Cu@C allows for better load dispersion under pressure, reducing load concentration at the friction interface and resulting in a smaller increase in frictional torque. Conversely, in homogeneous materials, the uniform distribution of Cu@C leads to more concentrated stress distribution, causing a larger increase in frictional torque with pressure. Furthermore, the lower coefficient of friction in gradient materials means a smaller frictional torque under the same pressure. This is attributed to the gradient structure reducing direct contact at the friction interface, thereby reducing energy loss during friction and lowering the coefficient of friction. The figure also shows that the increase in frictional torque is not entirely linear but exhibits a degree of nonlinearity. This nonlinearity arises because changes in material deformation and wear behavior affect the rate of increase in frictional torque when the pressure reaches a certain level.

[0071] In summary, compared to homogeneous materials, gradient materials exhibit significantly smaller variations in frictional torque, indicating that they maintain a more stable coefficient of friction under different conditions. By employing radial variation in the friction coefficient design, gradient materials effectively balance localized heating and heat conduction. In contrast, homogeneous materials, due to their uniform coefficient of friction and thermal conductivity, are prone to localized overheating and sudden fluctuations in frictional torque under high-speed or high-pressure conditions. Utilizing a synergistic effect, gradient materials, such as experimental group one, maintain the temperature difference between the inner and outer radii within -2℃ to 2℃ at 300 r / min, significantly better than the 3℃ to 7℃ range observed in homogeneous materials, thereby indirectly improving frictional stability. Ultimately, through gradient composition and structural design, gradient materials optimize the thermo-mechanical coupling behavior at the friction interface, achieving excellent frictional performance stability.

[0072] Step S3: Before and after each long-term friction test, the surface morphology of the friction pads before and after the test is analyzed using metallographic microscope (MMS) and scanning electron microscope (SEM) to reveal the microstructure, wear trajectory direction and material transfer characteristics.

[0073] Figure 8 The image shows an MMS image of a sintered gradient layer after a long-term rubbing test of some gradient materials.

[0074] Figure 9 This paper presents the SEM and EDS analysis results of some gradient materials after long-term friction tests. The analysis techniques or modules attached to a scanning electron microscope (SEM) can produce the energy spectrum. Figure 9 The distribution characteristics of Cu and C elements clearly show that the sample used is a gradient material.

Claims

1. A Cu@C core-shell particle material concentration gradient clutch friction plate, comprising a substrate and a liner sintered and connected to the substrate, characterized in that: The liner comprises several copper-based powders of different concentrations arranged circumferentially from the inside out. The composition of the copper-based powders by mass percentage is: (70-7x)% copper powder, 7x% Cu@C particles, 10% iron powder, 5% tin powder, 5% nickel powder, 4% silicon carbide, 2% silicon dioxide, 2% chromium powder, and 2% molybdenum powder.

2. The Cu@C core-shell particle material concentration gradient clutch friction plate according to claim 1, characterized in that: The liner comprises copper-based powder with three concentrations of x: 0–2, 2–4, and 4–6.

3. The Cu@C core-shell particle material concentration gradient clutch friction plate according to claim 2, characterized in that: The inner diameter region of the liner is ~ The median diameter region of the liner is ~ The outer diameter region of the liner is ~ ;in, =85mm, =115mm~110mm, =120mm~115mm, =125mm.

4. The Cu@C core-shell particle material concentration gradient clutch friction plate according to claim 3, characterized in that: The three different concentrations of copper-based powder are arranged in a ring along the inner diameter region, middle diameter region, and outer diameter region of the liner in the order of relatively medium concentration, high concentration, and low concentration.

5. The Cu@C core-shell particle material concentration gradient clutch friction plate according to claim 3, characterized in that: The three different concentrations of copper-based powder are arranged in a ring along the inner diameter region, middle diameter region, and outer diameter region of the liner in the order of relatively high concentration, medium concentration, and low concentration.

6. The Cu@C core-shell particle material concentration gradient clutch friction plate according to claim 3, characterized in that: The three different concentrations of copper-based powder are arranged in a ring along the inner diameter region, middle diameter region, and outer diameter region of the liner in the order of relatively low concentration, medium concentration, and high concentration.

7. The Cu@C core-shell particle material concentration gradient clutch friction plate according to claim 1, characterized in that, The preparation method of Cu@C particles is as follows: Cu particles and 98% concentration of dopamine hydrochloride are added to an ultrapure aqueous solution at a ratio of 5:1 and stirred to oxidize the catechol portion of dopamine to quinine, thereby polymerizing to form polydopamine PDA. After filtration, freezing and drying, Cu@PDA particles are obtained. Then, Cu@PDA particles are subjected to high-temperature heat treatment to obtain Cu@C particles.

8. A test method for a Cu@C core-shell particle material concentration gradient clutch friction plate, characterized in that, Includes the following steps: Step S1: The Cu@C shell-core particle material concentration gradient clutch friction plate described in any one of claims 1-7 is used as the experimental group, and a common copper-based friction plate with x=0 is set as control group one, and a friction plate containing only one concentration of copper-based powder is set as control group two. The friction plates are tested by a test bench consisting of a friction and wear tester and a temperature measurement system. Step S2: Conduct a long-term sliding friction test to study the radial temperature change of the friction pair under different speeds and pressures, and to study the change of friction torque of the friction pair under different speeds and pressures. Step S3: Before and after each long-term friction test, the surface morphology of the friction pads before and after the test is analyzed using a metallographic microscope (MMS) and a scanning electron microscope (SEM) to reveal the microstructure, wear trajectory direction and material transfer characteristics.

9. The test method for Cu@C core-shell particle material concentration gradient clutch friction plate according to claim 8, characterized in that: In step S2, tests are conducted sequentially using operating parameters of 100 r / min, 200 r / min, and 300 r / min under the same pressure, and 100 N, 200 N, and 300 N under the same rotation speed.

10. The test method for Cu@C core-shell particle material concentration gradient clutch friction plate according to claim 8, characterized in that: In step S1, the temperature measuring system includes a steel sheet (1) that matches the size of the friction plate and is in close contact to achieve sliding motion, and a temperature sensor (2) that is radially inserted into the steel sheet (1). The steel sheet (1) is provided with no less than three temperature measuring holes (11) at circumferential intervals, and the temperature measuring holes (11) are respectively inserted into the inner diameter region, middle diameter region and outer diameter region corresponding to the friction plate.

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