Heat input end gradient foam metal enhanced axial oscillation heat pipe grinding wheel and preparation method thereof

Abstract

The invention relates to a heat input end gradient foam metal enhanced axial oscillation heat pipe grinding wheel and a preparation method thereof. The grinding wheel mainly comprises a base body, a cover plate, a cutter bar, a working medium, an abrasive layer and gradient foam metal. The matrix is optimally designed and manufactured by combining a lattice structure and a 3D printing technology, and gradient foam metal is embedded in the position, corresponding to a heat input end, of an oscillating heat pipe runner. The aperture and porosity of the gradient foam metal are gradually increased from the flow channel wall face to the flow channel center direction, the hydrophilicity is gradually weakened, and a hollow horn-shaped structure with the material thickness gradually increased vertically downwards along the axis of the grinding wheel is formed. In the grinding process, due to the porous structure characteristic of the gradient foam metal in the grinding wheel, the vaporization core density in a flow channel is increased, meanwhile, bubble separation in the nucleate boiling process is accelerated, phase change heat transfer in a pipe is promoted, and the local dry-out phenomenon is effectively avoided. The grinding wheel structure can remarkably improve the heat dredging capacity and the working stability.

Description

Technical Field

[0001] The present invention relates to an axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end and a preparation method thereof. The grinding wheel is suitable for the field of grinding processing. By embedding gradient foam metal at the heat input end of the oscillating heat pipe flow channel in the grinding wheel, the phase change heat transfer of the working medium inside the grinding wheel during the grinding process is significantly enhanced, and the occurrence of local dry-out phenomenon is also effectively avoided. With the improvement of the heat transfer performance of the grinding wheel itself, more grinding heat energy is diverted to the grinding arc zone through the grinding wheel, thereby reducing the accumulation of heat in the grinding arc zone, effectively reducing the grinding temperature, and avoiding thermal damage to the workpiece surface. Background Art

[0002] When grinding difficult-to-process materials, a large amount of heat will be generated in the grinding arc area, and the heat is easily accumulated in the grinding arc area (the contact area between the workpiece and the grinding wheel), resulting in excessively high grinding temperature, affecting the processing quality and efficiency. As a component with a very high heat transfer coefficient, the oscillating heat pipe is combined with the grinding wheel matrix. The circulatory motion and phase change of the working fluid in the oscillating heat pipe can continuously and efficiently drain the heat from the grinding arc area, thereby enhancing heat transfer, avoiding grinding burns, and improving grinding efficiency.

[0003] Some studies have disclosed methods for making combined and integral axial heat pipe grinding wheels. For example, the invention patent with publication number CN109623675B discloses a combined axial rotating pulsating heat pipe grinding wheel and its preparation method, and the invention patent with publication number CN111283561B discloses an integral axial rotating oscillating heat pipe grinding wheel and its preparation method. Both patents provide specific steps for making axial oscillating heat pipe grinding wheels, and the structure is simple and reliable with low production cost. In these two invention patents, the oscillating heat pipe provides conditions for achieving efficient heat exchange of the grinding wheel with its self-excited bubble-liquid plug oscillating flow two-phase motion form and the heat transfer form dominated by sensible heat transfer. However, during the heat transfer process, the smooth surface of the flow channel wall reduces the number of bubble nucleation points, resulting in a prolonged start-up time of the oscillating heat pipe grinding wheel.

[0004] Related studies have provided methods for preparing gradient foam metals. In the paper "Experimental investigation on boiling heat transfer enhanced by gradient aperture porous copper" published in Applied Thermal Engineering, 191(2021):116877, Yahui Ma et al. prepared multilayer gradient aperture porous copper foam by using a pressing process, vacuum sintering process and cleaning process, and experimentally studied the pool boiling curves and corresponding bubble dynamics of these copper foam samples. The results show that the gradient aperture structure can meet the needs of steam escape and liquid replenishment, and can significantly enhance boiling heat transfer.

[0005] There are related studies that apply traditional foam metals of the same pore size to single-layer super-hard abrasive grinding wheels. The invention patent with publication number CN109571292B discloses a new type of high thermal conductivity phase change heat storage super-hard abrasive grinding wheel and its preparation method, including a grinding wheel substrate with an annular tube cavity, the interior of the annular tube cavity is filled with traditional foam metal, and is filled with an appropriate amount of heat transfer medium. The grinding wheel is designed to accelerate the boiling of the medium and the transfer of the grinding heat introduced into the grinding wheel to the inner end of the substrate by taking advantage of the large specific surface area and good permeability of the foam metal. However, the above patent does not take into account that the high density of the foam metal affects the reflux of the medium, which can easily lead to drying up at the heated wall surface, thereby affecting the overall heat transfer performance of the grinding wheel and deteriorating it.

[0006] Based on the above problems, it can be found that the performance of the axial oscillation heat pipe grinding wheel still needs to be optimized to improve its heat conduction ability and working stability. Summary of the invention

[0007] Purpose of the invention: In view of the shortcomings of the prior art, the present invention provides an axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end and a preparation method thereof, the core idea of ​​which is to embed gradient foam metal at the heat input end of the oscillating heat pipe flow channel in the grinding wheel. The aperture and porosity of the gradient foam metal gradually increase from the flow channel wall to the flow channel center direction and the hydrophilicity gradually weakens, forming a hollow trumpet-shaped structure with a gradually increasing material thickness vertically downward along the grinding wheel axis. During the grinding process, the gradient foam metal in the grinding wheel increases the density of the vaporization core in the flow channel due to the porous structure characteristics, accelerates the separation of bubbles in the nucleate boiling process, promotes phase change heat transfer in the tube, and effectively avoids the occurrence of local drying. In addition, the grinding wheel matrix is ​​manufactured by combining a lattice structure with 3D printing technology to optimize the design, so the overall mechanical properties and thermal properties of the grinding wheel will become more excellent, and the overall lightweight of the grinding wheel can be achieved to reduce power consumption. The grinding wheel structure described in the present invention can significantly improve the heat conduction ability and working stability of the traditional oscillating heat pipe grinding wheel in efficient grinding processing, thereby broadening the working range of the axial oscillating heat pipe grinding wheel.

[0008] Technical solution: In order to achieve the above invention purpose, the present invention provides an axial oscillating heat pipe grinding wheel with gradient foam metal at the heat input end. The axial oscillating heat pipe grinding wheel with gradient foam metal at the heat input end comprises: a base, a cover plate, a tool rod, a working medium, an abrasive layer, a gradient foam metal, etc. Its grinding motion is a rotation motion around its own axis.

[0009] The patent describes an axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end. The base body is processed with multi-loop oscillating heat pipe channels, gradient foam metal is embedded at the heat input end of the channel, the multi-loop channels are sealed with a cover plate, and a single layer of superhard abrasive is electroplated or brazed on the working surface of the base body. The vacuum injection system is connected to the vacuum injection pipeline on the grinding wheel base body to complete the injection work, and then the pipeline is sealed to ensure that the grinding wheel as a whole has good air tightness. One end of the tool rod is assembled with the cover plate, and the other end is connected to the machine tool spindle to drive the grinding wheel to rotate around its own axis.

[0010] Based on the above, each part of the oscillating heat pipe grinding wheel is made of steel material with high thermal conductivity and good structural strength (for example: carbon steel, stainless steel, etc.);

[0011] Based on the above, the central area of ​​the grinding wheel matrix adopts a lattice structure optimization design, which not only achieves lightweight, but also significantly improves its mechanical properties and thermal properties;

[0012] Based on the above, the grinding wheel matrix with multi-circuit flow channels is processed by 3D printing technology, and the 3D printing technologies that can be used include: laser powder bed melting technology, laser directed energy deposition technology, etc.;

[0013] Based on the above, the gradient foam metal can be made of foam copper, foam steel, foam nickel and other materials, with a pore size gradient varying between 30ppi-30000ppi, a porosity gradient varying between 75%-98%, and a through-porosity ≥90%;

[0014] Based on the above, two gradient foam metals are embedded in each loop channel, and the outer circumferential surface of the gradient foam metal is closely fitted with the wall surface of the flow channel;

[0015] Based on the above, the gradient foam metal has dual characteristics: first, the pore size increases from the submicron level to the submillimeter level from the oscillating heat pipe wall to the center, and the porosity also increases; second, the hydrophilicity is strong near the wall surface, and the hydrophobicity is strong in the central area. In addition, the foam metal is hollow trumpet-shaped, and the wall thickness gradually increases toward the bottom end of the grinding wheel; the gradient foam metal is embedded at the heat input end of the flow channel, which changes the contact environment between the working fluid and the flow channel wall. The micro-void structure and large specific surface area of ​​the foam metal provide a large number of vaporization cores for the nucleation boiling of the working fluid, and promote the occurrence of phase change heat transfer. Therefore, the new grinding wheel has significant advantages in enhancing heat exchange in the grinding arc zone;

[0016] Based on the above, the cover plate and the grinding wheel base can be connected by various welding methods, such as laser welding, argon arc welding, etc.

[0017] Based on the above, the working fluid can be water, methanol, acetone, etc., which can be determined according to the actual grinding conditions;

[0018] Based on the above, the super-hard abrasive can be diamond or CBN, and the arrangement of the abrasive on the working surface of the grinding wheel can be disordered or ordered;

[0019] The present invention relates to an axial oscillating heat pipe grinding wheel with a gradient foam metal reinforced at a heat input end, and the specific manufacturing steps are as follows:

[0020] Step 1: According to the actual grinding processing requirements, the lattice structure and 3D printing technology are used to optimize the design and process the oscillating heat pipe grinding wheel base; the grinding wheel base is a hollow cylinder with a honeycomb structure in the middle area. The grinding wheel base is provided with a multi-loop oscillating heat pipe flow channel, and the heat input end is provided with a vacuum injection pipeline, and the heat output end is provided with one or more heat dissipation fins;

[0021] Step 2: Process the gradient foam metal, which is hollow trumpet-shaped as a whole, with thicker walls towards the bottom. From the wall to the center of the oscillating heat pipe flow channel, the pore size gradually increases from submicron to submillimeter, and the porosity also gradually increases. Then, apply a layer of structural silver glue with high thermal conductivity on its outer surface, embed it into the multi-circuit flow channel at the heat input end of the oscillating heat pipe grinding wheel, and make its bottom level with the bottom of the direct flow channel. Then, heat and dry the grinding wheel matrix to ensure that the gradient foam metal fits tightly with the wall of the oscillating heat pipe flow channel.

[0022] Step 3: Weld the cover plate and the grinding wheel base to form an integrated structure. After welding, perform leak detection to ensure good air tightness. Then, use electroplating or brazing technology to plate or weld superhard abrasives with high thermal conductivity on the working surface of the grinding wheel base. Superhard abrasives include but are not limited to diamond or CBN.

[0023] Step 4: Build a vacuum injection system that matches the oscillating heat pipe flow channel in the grinding wheel matrix, connect the system to the vacuum injection pipeline on the matrix, first evacuate the multi-circuit pipeline to a low vacuum degree, and then inject the heat transfer medium suitable for the grinding working conditions into the flow channel. The injection amount of the medium also needs to be adapted. After the injection is completed, perform the tail sealing work;

[0024] Step 5: Connect one end of the tool bar to the cover plate with bolts, and the other end to the machine tool spindle, thereby driving the grinding wheel as a whole to rotate around its own axis.

[0025] Beneficial effects:

[0026] (1) The axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end proposed in the present invention not only significantly promotes phase change heat transfer in the pipe, but also effectively avoids the occurrence of local drying out, broadens the working range of the axial oscillating heat pipe grinding wheel, and improves its working stability by embedding gradient foam metal at the oscillating heat pipe flow channel position corresponding to the heat input end.

[0027] (2) The grinding wheel matrix is ​​designed and manufactured by combining a lattice structure with 3D printing technology, so the overall mechanical and thermal properties of the grinding wheel will become better, and it can also be lightweight and reduce energy consumption.

[0028] (3) The gradient foam metal embedded in the oscillating heat pipe flow channel has an increasing pore size and porosity from the flow channel wall to the flow channel center, and a gradually decreasing hydrophilicity, forming a hollow trumpet-shaped structure with a gradually increasing material thickness vertically downward along the grinding wheel axis. The high density of the foam metal in the annular tube cavity hinders the reflux of the gas working fluid after liquefaction, while the hollow trumpet-shaped structure does not have to worry about the reflux problem at all. In addition, the closer to the wall, the stronger the hydrophilicity of the foam metal, which can further enhance the boiling heat transfer, and the closer to the center of the flow channel, the stronger its hydrophobicity, which can further promote the flow of bubbles, so that the grinding wheel can still maintain good heat transfer performance under high centrifugal acceleration, increasing working stability.

[0029] (4) The pore size of the filled foam metal has a gradient change structure. The foam metal with a gradient change structure can promote the accelerated bubbles to smoothly escape from it, which effectively prevents the accumulation of bubbles and avoids the increase of thermal resistance and the occurrence of local burning.

[0030] In summary, the present invention embeds gradient foam metal at the heat input end of the oscillating heat pipe flow channel in the grinding wheel, which not only significantly enhances the phase change heat transfer of the working fluid inside the grinding wheel during the grinding process, but also effectively avoids the occurrence of local burning-out, broadens the working range of the axial oscillating heat pipe grinding wheel, and improves its working stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural explosion diagram of the axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end of the present invention;

[0032] Figure 2 This is a schematic diagram of the upper structure of the 3D-printed base of the axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end of the present invention;

[0033] Figure 3 This is a schematic diagram of the lower structure of the 3D-printed base of the axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end of the present invention;

[0034] Figure 4 It is a schematic diagram of the connection between the six-circuit flow channel and the gradient foam metal of the axial oscillating heat pipe grinding wheel reinforced with the gradient foam metal at the heat input end of the present invention;

[0035] Figure 5 A schematic diagram of the gradient foam metal of the axial oscillating heat pipe grinding wheel reinforced with the gradient foam metal at the heat input end of the present invention;

[0036] Figure 6 A schematic cross-sectional view and a partially enlarged schematic view of the gradient foam metal of the axial oscillating heat pipe grinding wheel reinforced with the gradient foam metal at the heat input end of the present invention;

[0037] Figure 7 A schematic diagram of the hydrophilicity and hydrophobicity of the gradient foam metal of the axial oscillating heat pipe grinding wheel reinforced with the gradient foam metal at the heat input end of the present invention from the outside to the inside;

[0038] Figure 8 A schematic diagram of a cover plate of an axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end of the present invention;

[0039] Fig. 9 It is a schematic diagram of the welding of the cover plate and the base of the axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end of the present invention and a schematic diagram of the electroplating orderly arranged abrasives;

[0040] Fig.10 A schematic diagram of a cutter bar of an axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end of the present invention;

[0041] Fig.11 It is a schematic diagram of the simulation of the heat exchange effect of the axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end and the non-axial oscillating heat pipe grinding wheel on the workpiece according to the present invention.

[0042] Description of the main reference numerals in the figures:

[0043] 1 substrate, 1-1 six-loop oscillating heat pipe flow channel, 1-1-1 direct current flow channel, 1-1-2 connecting flow channel, 1-2 heat dissipation fins, 1-3 vacuum injection pipeline, 1-4 honeycomb structure formed by lattice structure optimization.

[0044] 2 Gradient metal foam.

[0045] 3 cover plate, 3-1 cover plate threaded holes.

[0046] 4 Abrasive layers.

[0047] 5 shank, 5-1 shank countersunk hole.

[0048] 6M3×6 bolts. DETAILED DESCRIPTION

[0049] In order to enable those skilled in the art to better understand the technical solutions in the patent application of the present invention, the technical solutions in the present application are clearly and completely described below in conjunction with the drawings in the present application. Obviously, the described implementation methods are only part of the implementation methods of the present application, not all implementation methods. Based on the implementation methods in the present application, all other implementation methods obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application.

[0050] Figure 1 This is an exploded view of the structure of the axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end of the present invention. Figure 1The present invention provides an axial oscillating heat pipe grinding wheel with a gradient foam metal reinforced at the heat input end, which mainly includes a base 1 made of 45 steel, a gradient foam metal 2, a cover plate 3, a tool rod 5 and other related accessories and structures.

[0051] Figure 2 This is a schematic diagram of the upper structure of the 3D printed base of the axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end of the present invention. Figure 3 This is a schematic diagram of the lower structure of the 3D printed base of the axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end of the present invention. Figure 2 , 3 As shown, the 45 steel substrate is optimized and manufactured using a lattice structure and 3D printing technology. The substrate (excluding the heat sink fins 1-2) is 59 mm high and 50 mm in diameter. There are six loops of oscillating heat pipe channels 1-1 inside the substrate. The channels include direct current channels 1-1-1 (12) and connecting channels 1-1-2 (12). The diameter of the direct current channel is 3 mm, and the width and depth of the connecting channel are both 3 mm. There are 6 heat sink fins 1-2 located at the heat output end (the heat input end of the grinding wheel is located in the contact area between the grinding wheel and the workpiece), of which the top fin is 2 mm thick, and the thickness of the other fins is 1 mm. The diameter of the fins is 60 mm, and the spacing between the two fins is 1 mm. There is a groove with a diameter of 50 mm and a thickness of 1 mm between the heat sink fins and the substrate. The grinding wheel base adopts a hollow cylindrical style with a wall thickness of 4mm. The middle area has a honeycomb structure 1-4 designed using a lattice structure to enhance the overall mechanical and thermal properties of the grinding wheel, and also achieve lightweight and reduce energy consumption. The honeycomb structure is designed with a hexagonal lattice with a diameter of 42mm and a height of 55mm, and the bottom surface is flush with the bottom of the base.

[0052] The gradient foam metal 2 is placed in the direct current flow channel 1-1-1, such as Figure 4 As shown. The gradient metal foam 2 is hollow trumpet-shaped as a whole, and the wall thickness increases toward the bottom. In this example, the gradient metal foam has a height of 17.5 mm, an outer diameter of 3 mm, and a minimum inner diameter of 1 mm. It has dual characteristics: on the one hand, from the wall surface to the center of the oscillating heat pipe flow channel, the pore size gradually increases from the submicron level to the submillimeter level, and the porosity also gradually increases, such as Figure 6 On the other hand, the closer to the wall, the stronger the hydrophilicity of the foam metal, and the closer to the center of the flow channel, the stronger its hydrophobicity, as shown in Figure 7As shown. The material of the gradient foam metal is foam copper (made by pressing process, vacuum sintering process and cleaning process, reference "Experimental investigation on boiling heat transfer enhanced by gradient aperture porous copper" "Applied Thermal Engineering", 191 (2021): 116877), the aperture gradually increases from 30000ppi to 30ppi, the porosity gradually increases from 90% to 98%, and the through-porosity is 98%. After the 12 gradient foam metals are processed, a layer of conductive silver glue with high thermal conductivity (Henkel Loctite 84-1LMISR4 conductive silver glue) is evenly applied on the outer surface, and manually embedded into 12 DC channels, and the bottom of the gradient foam metal is level with the bottom of the DC channel. Finally, the grinding wheel substrate is placed in an oven for heating at a temperature of 175°C for 60 minutes to heat and solidify the silver glue, ensuring that the gradient foam metal and the flow channel wall fit closely to reduce the heat transfer thermal resistance;

[0053] like Fig. 9 As shown, a cover plate 3 is used to seal the oscillating heat pipe flow channel embedded in the gradient foam metal. The cover plate is a stepped shaft style, with an upper cylindrical diameter of 50 mm and a thickness of 1 mm, a lower cylindrical diameter of 42 mm and a thickness of 4 mm, and 4 evenly distributed M3×0.5 threaded holes 3-1, as shown in FIG. Figure 8 As shown in the figure, after the cover plate covers the base, the upper surface is flush with the upper surface of the base. The two are welded into an integrated structure using laser welding, with a welding power of 1200W and a welding speed of 2500mm / min. The welded base is then leak-checked to ensure good air tightness. If there is any leakage, repair welding is required.

[0054] On the working surface of the oscillating heat pipe grinding wheel, CBN abrasive grains with a particle size of 80 / 100# are plated using an electroplating process. The abrasives are arranged in an orderly manner to form an abrasive layer 4, such as Fig. 9 As shown in the figure, the orderly arrangement of abrasives not only helps to reduce grinding heat, but also provides sufficient chip space, effectively reducing the occurrence of grinding wheel clogging;

[0055] In the six-loop flow channel of the oscillating heat pipe, acetone working fluid is injected through the vacuum injection system and the vacuum injection pipes 1-3, and the filling rate (the ratio of the injected working fluid volume to the internal volume of the oscillating heat pipe) is 60%. Acetone is selected as the heat transfer working fluid due to its low boiling point, small surface tension and dynamic viscosity. These characteristics greatly reduce the resistance that acetone needs to overcome during the bubble-liquid plug oscillation flow process, making it easier to achieve the circulation flow of the working fluid, thereby significantly improving the heat exchange performance. After the injection work is completed, the vacuum injection pipe is compressed using an ultrasonic welding sealing machine to seal it.

[0056] The shank 5 is formed by connecting two cylinders with different diameters, and the whole is in the form of a stepped shaft. Fig.10 As shown, the lower cylinder has a diameter of 42 mm and a height of 5 mm, and the upper cylinder has a diameter of 25 mm and a height of 50 mm. In addition, there are 4 countersunk holes 5-1 on the lower cylinder, the countersunk diameter is 6 mm and the thickness is 3 mm, the through hole diameter is 3 mm and the thickness is 2 mm, and each edge is rounded with a fillet radius of 0.5 mm.

[0057] The base 1 and the tool bar 5 are assembled with the help of the countersunk hole and the M3×6 bolt 6, and the runout and coaxiality meet the requirements, thus forming an axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end that can be used for grinding. When the workpiece is ground using the axial rotating oscillating heat pipe grinding wheel and the non-axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end, the heat flux density is 1×10 8 W / mm 2 The schematic diagram of the simulation of the heat transfer effect of the two grinding wheels on the workpiece is shown in Figure 2. Fig.11 As shown. It can be found that the maximum temperature of the grinding arc zone of the non-oscillating heat pipe grinding wheel reaches 1367℃, and the axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end controls the maximum temperature of the grinding arc zone at 659℃, which is 52% lower. Therefore, the new grinding wheel has excellent heat transfer performance and can drain more heat from the grinding arc zone compared with the non-axial oscillating heat pipe grinding wheel, resulting in a lower grinding temperature, thereby avoiding thermal damage to the workpiece surface.

[0058] It can be seen from the technical solution provided by the present invention that the present invention has the following beneficial effects:

[0059] (1) The axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end proposed in the present invention not only significantly promotes phase change heat transfer in the pipe, but also effectively avoids the occurrence of local drying out, broadens the working range of the axial oscillating heat pipe grinding wheel, and improves its working stability by embedding gradient foam metal at the oscillating heat pipe flow channel position corresponding to the heat input end.

[0060] (2) The grinding wheel matrix is ​​designed and manufactured by combining a lattice structure with 3D printing technology, so the overall mechanical and thermal properties of the grinding wheel will become better, and it can also be lightweight and reduce energy consumption.

[0061] (3) The gradient foam metal embedded in the oscillating heat pipe flow channel has an increasing pore size and porosity from the flow channel wall to the flow channel center, and a gradually decreasing hydrophilicity, forming a hollow trumpet-shaped structure with a gradually increasing material thickness vertically downward along the grinding wheel axis. The high density of the foam metal in the annular tube cavity hinders the reflux of the gas working fluid after liquefaction, while the hollow trumpet-shaped structure does not have to worry about the reflux problem at all. In addition, the closer to the wall, the stronger the hydrophilicity of the foam metal, which can further enhance the boiling heat transfer, and the closer to the center of the flow channel, the stronger its hydrophobicity, which can further promote the flow of bubbles, so that the grinding wheel can still maintain good heat transfer performance under high centrifugal acceleration, increasing working stability.

[0062] (4) The pore size of the filled foam metal has a gradient change structure. The foam metal with a gradient change structure can promote the accelerated bubbles to smoothly escape from it, which effectively prevents the accumulation of bubbles and avoids the increase of thermal resistance and the occurrence of local burning.

[0063] In summary, the present invention embeds gradient foam metal at the heat input end of the oscillating heat pipe flow channel in the grinding wheel, which not only significantly enhances the phase change heat transfer of the working fluid inside the grinding wheel during the grinding process, but also effectively avoids the occurrence of local burning-out, broadens the working range of the axial oscillating heat pipe grinding wheel, and improves its working stability.

[0064] The above description of various embodiments of the present application is provided to those skilled in the art for the purpose of description. It is not intended to be exhaustive or to limit the present invention to a single disclosed embodiment. As mentioned above, various substitutions or changes of the present application will be apparent to those skilled in the art to which the above-mentioned technology belongs. Therefore, although some alternative embodiments have been specifically discussed, other embodiments will be apparent, or those skilled in the art will be relatively easy to derive. The present application is intended to include all substitutions, modifications, and changes of the present invention discussed herein, as well as other embodiments falling within the spirit and scope of the above-mentioned application.

[0065] Although the present application has been described through embodiments, those skilled in the art will appreciate that there are many modifications and variations to the present application without departing from the spirit of the present application, and it is intended that the appended claims include these modifications and variations without departing from the spirit of the present application.

Claims

1. An axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end, characterized in that: The grinding wheel comprises: a base, a cover plate, a tool bar, a working medium, an abrasive layer, and a gradient foam metal; The grinding wheel base is a hollow cylinder with a honeycomb structure (1-4) in the middle area; a heat dissipation fin (1-2) is provided at the heat output end of the base, and an abrasive layer (4) with abrasives arranged in an orderly manner is electroplated or brazed on the working surface of the grinding wheel; a cover plate (3) is provided on the top of the grinding wheel base to seal the base, one end of the tool rod (5) is connected to the cover plate in an assembled manner, and the other end is connected to the main shaft of the machine tool to drive the grinding wheel to rotate around its own axis; A grinding wheel base body has a multi-loop oscillating heat pipe flow channel (1-1) inside, and a working medium is injected into the oscillating heat pipe flow channel; the flow channel includes a direct flow channel (1-1-1) and a connecting flow channel (1-1-2), and a gradient foam metal (2) is placed in the direct flow channel, and the outer cylindrical surface of the gradient foam metal is tightly fitted with the wall surface of the flow channel; during the grinding process, the gradient foam metal in the grinding wheel increases the density of the vaporization core in the flow channel due to its porous structure characteristics, accelerates the separation of bubbles in the nucleate boiling process, promotes phase change heat transfer in the tube, and effectively avoids the occurrence of local drying.

2. The axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end according to claim 1, characterized in that: The number of loops of the oscillating heat pipe flow channel is six; the number of direct-flow channels and connecting flow channels is 12; the working fluid includes but is not limited to water, methanol, and acetone.

3. The axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end according to claim 1, characterized in that: The honeycomb structure (1-4) is a hexagonal lattice, the bottom surface is flush with the bottom of the substrate, and is obtained by combining lattice structure optimization design with 3D printing technology. The 3D printing technology includes but is not limited to laser powder bed melting technology and laser directed energy deposition technology.

4. The axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end according to claim 1, characterized in that: The gradient foam metal (2) is in a hollow trumpet shape as a whole, with the wall thickness increasing towards the bottom, and the bottom being flush with the bottom of the direct current flow channel; From the wall to the center of the oscillating heat pipe flow channel, the pore size gradually increases from submicron level to submillimeter level, and the porosity also gradually increases; a layer of structural silver glue with high thermal conductivity is evenly applied on the outer cylindrical surface of the gradient foam metal.

5. The axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end according to claim 4, characterized in that: The materials of gradient foam metal include but are not limited to foam copper, foam steel or foam nickel; from the wall to the center of the oscillating heat pipe flow channel, the pore size changes gradually between 30ppi-30000ppi, the porosity changes gradually between 75%-98%, and the through-porosity is ≥90%.

6. The axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end according to claim 4, characterized in that: The material of the gradient foam metal is foam copper; from the wall to the center of the oscillating heat pipe flow channel, the pore size gradually increases from 30000ppi to 30ppi, the porosity gradually increases from 90% to 98%, and the through-porosity is 98%.

7. The axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end according to claim 1, characterized in that: There are 6 heat dissipation fins (1-2) in total, wherein the thickness of the top fin is greater than that of the other fins, the distance between the two fins is in a non-contact state, and there is a groove between the heat dissipation fin and the base.

8. The method for preparing an axial oscillating heat pipe grinding wheel reinforced with gradient foam metal at the heat input end according to claim 1, characterized in that: Here are the steps: Step 1: According to the actual grinding processing requirements, the lattice structure and 3D printing technology are used to optimize the design and process the oscillating heat pipe grinding wheel base; the grinding wheel base is a hollow cylinder with a honeycomb structure in the middle area. The grinding wheel base is provided with a multi-loop oscillating heat pipe flow channel, and the heat input end is provided with a vacuum injection pipeline, and the heat output end is provided with one or more heat dissipation fins; Step 2: Process the gradient foam metal, which is hollow trumpet-shaped as a whole, with thicker walls towards the bottom. From the wall to the center of the oscillating heat pipe flow channel, the pore size gradually increases from submicron to submillimeter, and the porosity also gradually increases. Then, apply a layer of structural silver glue with high thermal conductivity on its outer surface, embed it into the multi-circuit flow channel at the heat input end of the oscillating heat pipe grinding wheel, and make its bottom level with the bottom of the direct flow channel. Then, heat and dry the grinding wheel matrix to ensure that the gradient foam metal fits tightly with the wall of the oscillating heat pipe flow channel. Step 3: Weld the cover plate and the grinding wheel base to form an integrated structure. After welding, perform leak detection to ensure good air tightness. Then, use electroplating or brazing technology to plate or weld superhard abrasives with high thermal conductivity on the working surface of the grinding wheel base. Superhard abrasives include but are not limited to diamond or cubic boron nitride (CBN). Step 4: Build a vacuum injection system that matches the oscillating heat pipe flow channel in the grinding wheel matrix, connect the system to the vacuum injection pipeline on the matrix, first evacuate the multi-circuit pipeline to a low vacuum degree, and then inject the heat transfer medium suitable for the grinding working conditions into the flow channel. The injection amount of the medium also needs to be adapted. After the injection is completed, perform the tail sealing work; Step 5: Connect one end of the tool bar to the cover plate with bolts, and the other end to the machine tool spindle, thereby driving the grinding wheel as a whole to rotate around its own axis.

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