Integrated ultrasonic excitation type nanofluid modified heat pipe grinding head and method of using same

Abstract

The application discloses an integrated ultrasonic excitation type nanofluid modified heat pipe grinding head and a using method thereof, and belongs to the technical field of ultrasonic auxiliary grinding and heat management. The heat pipe grinding head is internally provided with a condensing section, an adiabatic section and an evaporating section in sequence along an axial direction, and is filled with a nanofluid working medium in an inner cavity; the inner wall of the heat pipe is subjected to microstructure construction and wettability modification treatment, so that the wetting and circulating flow performance of the nanofluid is improved; the condensing section is integrated with an ultrasonic tool shank amplitude rod, and the outer wall spiral groove has the functions of a heat dissipation fin and a longitudinal torsional mode conversion; the adiabatic section gradually changes in diameter to amplify the ultrasonic amplitude; the evaporating section serves as a carrier of an abrasive layer, and realizes cutting and efficient heat transfer. In the grinding process, ultrasonic intermittent cutting reduces the grinding force and temperature; ultrasonic cavitation and acoustic streaming disperse the nanofluid in real time, inhibit agglomeration and guarantee continuous heat exchange. The application realizes the double integration of internal ultrasonic heat exchange strengthening and external ultrasonic cutting assistance, and provides tool support for active control of heat load in a grinding area.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic-assisted grinding and thermal management technology, specifically to an integrated ultrasonic-excited nanofluid-modified heat pipe grinding head and its application method, which is suitable for efficient, low-damage precision grinding of difficult-to-machine materials. Background Technology

[0002] With the widespread application of hard and brittle materials, high-temperature alloys, ceramics, and composite materials in aerospace, precision manufacturing, biomedicine, and electronic packaging, the demand for efficient, low-damage, and high-precision machining technologies is constantly increasing. Grinding, as an important means of achieving high-precision surface forming and microstructure machining, has wide applications in the processing of these materials. However, during the grinding process, intense friction and plastic deformation occur between the abrasive grains and the workpiece, leading to rapid heat accumulation in the contact area. This results in problems such as excessively high local temperature rise, workpiece surface burning, microcrack propagation, increased residual stress, and accelerated tool wear. These problems not only affect the surface quality and dimensional accuracy of the workpiece but also shorten the service life of the grinding head, hindering further improvements in processing efficiency.

[0003] Ultrasonic-assisted grinding technology has gained increasing attention for improving grinding performance. By superimposing high-frequency micro-amplitude vibrations onto the grinding tool, instantaneous cutting resistance can be reduced, chip removal conditions improved, abrasive clogging lessened, grinding force reduced, and surface finish improved. While existing ultrasonic-assisted grinding devices have improved machining performance to some extent, their main function is focused on improving the mechanical processing, with limited ability to actively control grinding heat. When machining heat-sensitive materials or when machining parameters are large, grinding heat can still easily accumulate at the tool tip and on the workpiece surface, affecting machining stability and quality.

[0004] On the other hand, heat pipe technology, due to its advantages such as high-efficiency heat transfer, compact structure, and no need for additional power, is gradually being introduced into the heat dissipation design of cutting tools and grinding wheels. Heat pipes achieve rapid heat transfer through the evaporation and condensation of the working fluid within a sealed cavity, effectively improving the problem of excessive local temperature rise. Furthermore, using nanofluids instead of traditional single working fluids can improve the thermal conductivity and heat transfer capacity of the working fluid to a certain extent; therefore, nanofluid heat pipes have application potential in the field of enhanced heat transfer. However, during long-term operation, nanofluids are prone to particle sedimentation, agglomeration, and wall deposition, leading to decreased working fluid stability, reduced heat transfer performance, and even heat pipe failure. These problems are particularly pronounced under rotational, high-temperature, and alternating load conditions.

[0005] In existing technologies, ultrasonic-assisted grinding systems and heat pipe cooling structures are mostly designed separately, lacking an integrated coupling solution for the grinding head assembly. Furthermore, while some technologies involve nanofluid heat pipes to enhance heat transfer, effective solutions are still lacking for maintaining the long-term dispersion and stability of nanofluids in the grinding environment, preventing particle deposition, and thus continuously leveraging the heat pipe's cooling advantages. Therefore, there is an urgent need for a novel grinding head assembly that combines ultrasonic-assisted machining and stable enhanced heat dissipation. This assembly should not only improve grinding mechanical behavior but also suppress nanofluid particle sedimentation and agglomeration through ultrasonic vibration, enhancing heat pipe heat transfer stability and meeting the demand for efficient and low-damage machining of difficult-to-machine materials. Summary of the Invention

[0006] To address the problems in existing ultrasonic-assisted grinding devices, such as insufficient heat dissipation, easy sedimentation and agglomeration of the nanofluid working fluid in the heat pipe grinding head, decreased heat transfer performance with working time, and difficulty in effectively controlling the temperature in the grinding zone, this invention provides an integrated ultrasonically excited nanofluid-modified heat pipe grinding head and its application method. To achieve the above technical objectives, the technical solution adopted by this invention is as follows:

[0007] An integrated ultrasonically excited nanofluid-modified heat pipe grinding head includes:

[0008] Handle casing;

[0009] An ultrasonic transducer assembly is installed inside the tool holder housing;

[0010] The heat pipe grinding head base also functions as an amplitude transformer. It has a vacuum heat pipe cavity inside, which includes a condensation section, an insulation section and an evaporation section along the axial direction. The vacuum heat pipe cavity is filled with a nano-fluid working fluid.

[0011] The condensation section and the insulation section of the heat pipe grinding head base constitute an ultrasonic amplitude transformer, which is used to transmit ultrasonic vibration to the grinding arc area;

[0012] The ultrasonic vibrations generated by the ultrasonic transducer during operation are directly transmitted to the grinding arc zone through the heat pipe grinding head substrate, and simultaneously act on the nanofluid working medium in the vacuum heat pipe cavity to disperse the nanoparticles in the nanofluid working medium.

[0013] To optimize the above technical solution, the specific measures also include:

[0014] The ultrasonic transducer assembly includes a rear cover plate, a piezoelectric ceramic sheet, and the upper end of a heat pipe grinding head base. The rear cover plate is used to press the piezoelectric ceramic sheet and provide axial prestress. The piezoelectric ceramic sheet is an annular piezoelectric ceramic sheet, which is stacked along the axial direction. The upper end of the heat pipe grinding head base passes through the central hole of the piezoelectric ceramic sheet and forms a series pre-tightening structure with the rear cover plate and the lower part of the heat pipe grinding head base, so that the ultrasonic vibration generated by the piezoelectric ceramic sheet is directly transmitted to the heat pipe grinding head base.

[0015] The integrated ultrasonically excited nanofluid-modified heat pipe grinding head also includes a locking nut, a pull stud, an outer plug, and a connecting screw; the upper end of the heat pipe grinding head base is threadedly connected to the outer plug; the locking nut is used to connect the tool holder housing and the heat pipe grinding head base, and applies axial clamping force to the upper end of the heat pipe grinding head base; the connecting screw passes downward from the upper part of the heat pipe grinding head base, passes through the rear cover plate and the piezoelectric ceramic plate in sequence, and connects to the upper step on the inner side of the outer plug; an O-ring is provided between the connecting screw and the upper end of the heat pipe grinding head base.

[0016] The outer wall of the condensation section is provided with spiral grooves, which form heat dissipation fins and are also constructed to convert ultrasonic longitudinal vibration into longitudinal torsional vibration mode.

[0017] The diameter of the insulating section gradually decreases from the condensation section to the evaporation section along the axial direction, and its outer contour is conical or exponential to form the amplitude amplification structure of the ultrasonic amplitude transformer; the outer layer of the insulating section is coated with insulating material.

[0018] The outer wall of the evaporation section is provided with an abrasive layer as a grinding working surface; the inner wall of the evaporation section is provided with a raised micropillar structure to enhance capillary force, expand the heat exchange area and promote the nucleation boiling of nanofluids.

[0019] The inner wall of the condensation section is provided with a constriction-expansion flow channel and undergoes surface wettability modification treatment to promote droplet condensation and accelerate the shedding of condensate droplets to reduce thermal resistance.

[0020] A method for using an integrated ultrasonically excited nanofluid-modified heat pipe grinding head includes the following steps:

[0021] Step a: Evacuate the vacuum heat pipe cavity of the heat pipe grinding head substrate through the transverse and longitudinal liquid injection channels, and inject nanofluid working fluid into the vacuum heat pipe cavity;

[0022] Step b: Seal the transverse and longitudinal injection channels using the upper end of the heat pipe grinding head base, the outer plug, the connecting screws, and the O-rings;

[0023] Step c: Install the tool holder housing onto the machine tool spindle using a pull stud, and turn on the ultrasonic power supply to drive the heat pipe grinding head substrate to generate ultrasonic vibration using the piezoelectric ceramic plate.

[0024] Step d: Start the machine tool for grinding. The evaporation section absorbs the grinding heat. The nanofluid working medium evaporates after being heated and flows to the condensation section to release heat and condense. Then it flows back to the evaporation section to form a thermal cycle.

[0025] During the grinding process, ultrasonic vibration acts simultaneously on the nanofluid working medium in the grinding arc zone and the vacuum heat pipe cavity to reduce the agglomeration of nanoparticles. This, combined with the spiral grooves on the outer periphery of the condensation section, enhances heat transfer, thereby simultaneously improving grinding performance and heat pipe heat transfer performance.

[0026] The present invention has the following beneficial effects:

[0027] First, the present invention integrates the ultrasonic vibration structure with the heat pipe heat dissipation structure into one unit, so that the grinding head assembly has both ultrasonic-assisted processing and efficient heat dissipation functions. It has a compact structure, strong functional coupling, and is suitable for use under high speed and high heat flux density conditions.

[0028] Secondly, this invention utilizes ultrasonic vibration to continuously disturb the nanoparticles in the nanofluid working fluid, which can effectively suppress particle sedimentation, agglomeration and wall deposition, improve the dispersion stability of the nanofluid in the heat pipe cavity, and thus overcome the problem of heat transfer performance degradation of traditional nanofluid heat pipes during long-term operation.

[0029] Third, the present invention can rapidly transfer the heat generated in the grinding zone to the cold end and release it through the evaporation-condensation cycle of the nanofluid working medium in the heat pipe cavity, which significantly reduces the temperature of the grinding arc zone and reduces the thermal damage and grinding burn phenomenon on the workpiece surface.

[0030] Fourth, while reducing grinding temperature, this invention can also improve the overall balance between grinding force, tool wear and workpiece surface quality, which is beneficial to improving machining accuracy, machining stability and grinding head service life.

[0031] Fifth, this invention is applicable to the efficient precision grinding of hard and brittle materials, high-temperature alloys, ceramics and composite materials, and has strong applicability and promotion value. Attached Figure Description

[0032] Figure 1 This is a cross-sectional view of the overall structure of the present invention.

[0033] Figure 2 This is a schematic diagram of the heat pipe grinding head structure of the present invention.

[0034] Figure 3 This is a schematic diagram of the spiral groove structure of the condensing section of the heat pipe grinding head of the present invention. The spiral groove structure also serves to adjust the ultrasonic longitudinal torsional mode.

[0035] Figure 4 for Figure 2 Enlarged view at point A in the middle, showing the flow channels on both sides of the heat pipe injection.

[0036] Figure 5 for Figure 1 The enlarged view at point B shows the grinding surface of the heat pipe grinding head and the structure of the evaporation section.

[0037] Figure 6 This is a schematic diagram of the microstructure of the inner wall of the evaporation section of the heat pipe grinding head of the present invention.

[0038] Figure 7This is a schematic diagram of the expansion and contraction flow channel structure on the inner wall of the condensation section of the heat pipe grinding head according to the present invention.

[0039] List of reference numerals in the attached diagram: 1: Tool holder housing, 2: O-ring, 3: Locking nut, 4: Longitudinal liquid injection channel, 5: Spiral groove, 6: Heat pipe grinding head base, 6a: Condensation section, 6b: Insulation section, 6c: Evaporation section, 7: Pull stud, 8: Rear cover plate, 9: Connecting screw, 10: Piezoelectric ceramic plate, 11: Outer plug, 12: Upper end of heat pipe grinding head base, 13: Transverse liquid injection channel, 14: Grinding arc zone, 15: Nanofluid working fluid. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following embodiments. Any equivalent substitutions or modifications made by those skilled in the art based on the disclosure of the present invention without departing from the concept of the present invention should fall within the scope of protection of the present invention.

[0041] like Figure 1 As shown, the ultrasonic-assisted dispersion nanofluid heat pipe grinding head assembly in this embodiment includes a tool holder housing 1, an ultrasonic transducer assembly disposed within the tool holder housing 1, a locking nut 3, a heat pipe grinding head, and a pull stud 7. The ultrasonic transducer assembly, disposed inside the tool holder housing 1, mainly consists of a rear cover plate 8, a piezoelectric ceramic plate 10, and the upper end 12 of the heat pipe grinding head base that holds the piezoelectric ceramic plate in place. The piezoelectric ceramic plate 10 generates axial expansion and contraction vibration under high-frequency alternating electrical signal excitation. The vibration is transmitted through the rear cover plate 8 and the upper end 12 of the heat pipe grinding head base to the middle section of the heat pipe grinding head, which acts as an amplitude transformer, and then directly to the grinding arc zone 14. The locking nut 3 and pull stud 7 are used to axially pre-tighten the connecting components to ensure stable ultrasonic vibration transmission and improve the overall rigidity of the assembly.

[0042] like Figure 2 As shown, the heat pipe grinding head includes a grinding head housing, a heat pipe cavity 6 formed inside the grinding head housing, a nanofluid working fluid 15 encapsulated within the heat pipe cavity 6, and a grinding arc region 14 disposed on the outer surface of the grinding head housing. The heat pipe cavity 6 preferably extends axially along the heat pipe grinding head, with a section near the grinding arc region 14 constituting an evaporation section 6c and a section near the spiral groove 5 constituting a condensation section 6a. To facilitate droplet condensation of the gaseous working fluid, the constriction and expansion channels on the inner wall of the condensation section promote rapid droplet detachment; a hydrophilic / hydrophobic structure is provided at the location of the condensation section 6a in the heat pipe cavity 6. To promote nucleation boiling and improve boiling heat transfer efficiency, a micropillar structure is provided at the location of the evaporation section 6c in the heat pipe cavity 6.

[0043] In this example, the connecting screw 9 has threads at both ends, connects to the rear cover plate 8 at the top, connects to four piezoelectric ceramic plates 10 in series in the middle, and connects to the outer plug 11 at the bottom. The outer plug 11 has steps at both ends on its inner side. The upper step has threads to connect with the connecting screw, and the lower step has an O-ring 2 to seal the liquid injection. The outer plug 11 has steps on its outer side. The upper step has threads to connect with the upper end 12 of the heat pipe grinding head base, and the lower step has an O-ring 2 to seal the liquid injection. The outer plug 11 has a through transverse liquid injection channel 13, through which the nanofluid flows into the longitudinal liquid injection channel 4, and then into the heat pipe cavity 6.

[0044] In the example, the locking nut is threaded to the tool holder housing, and the locking nut then engages with the positioning groove on the heat pipe grinding head to achieve circumferential positioning of the heat pipe grinding head and the internal ultrasonic transducer assembly. The upper end 12 of the heat pipe grinding head base then presses against the tool holder housing to achieve axial positioning of the heat pipe grinding head and the internal ultrasonic transducer assembly.

[0045] In this embodiment, during assembly, the rear cover plate 8, piezoelectric ceramic sheet 10, connecting screw 9, outer plug 11, and heat pipe grinding head are assembled sequentially, and then the overall pre-tightening is completed using locking nuts 3 and pull studs 7. After assembly, the component is made to work in a resonant or near-resonant state by adjusting the size of the amplitude transformer or the system operating parameters to obtain a stable and effective ultrasonic vibration output.

[0046] When using this grinding head assembly for grinding, the assembly is first installed on the machine tool spindle, and the ultrasonic transducer assembly is connected to the ultrasonic power supply. The ultrasonic power supply outputs an alternating electrical signal of a certain frequency and power, causing the piezoelectric ceramic sheet 10 to vibrate at high frequency. Subsequently, the heat pipe grinding head grinds the workpiece under the coupled action of rotation and ultrasonic vibration. During the grinding process, a large amount of heat is generated in the contact area between the grinding arc zone 14 and the workpiece. The heat is first transferred to the evaporation section at the front end of the heat pipe grinding head, causing the nanofluid working medium 15 near the heat source area in the heat pipe cavity 6 to be heated and vaporized. The vapor migrates along the cavity to the condensation section, and the heat is conducted out through the heat dissipation fins formed by the spiral grooves outside the condensation section, exchanging heat with the external environment. The condensate then returns to the evaporation section under the capillary force generated by the capillary structure, thereby realizing cyclic heat transfer.

[0047] Unlike conventional heat pipe grinding heads, the ultrasonic vibration in this invention acts not only on the grinding arc zone 14 but also simultaneously on the nanofluid working medium 15 within the heat pipe cavity 6. Because the vibration generates periodic disturbances to the fluid and particles, the aggregation tendency of nanoparticles in the fluid is weakened, the particle settling velocity decreases, and the probability of particles adhering to the inner wall of the cavity and the surface of the microstructure is correspondingly reduced. Therefore, the dispersion stability and thermal conductivity of the nanofluid working medium 15 can be maintained for a longer period. Consequently, the heat pipe grinding head not only exhibits superior heat dissipation capacity in the initial stages of processing but also maintains relatively stable heat transfer efficiency during long-term continuous processing.

[0048] It should be noted that the types of nanofluid working fluids, microstructure forms, abrasive layer types, connection methods, frequency ranges, and filling rates in the above embodiments are merely preferred embodiments and are not intended to limit the scope of protection of this invention. Any technical solution that, based on the technical concept of this invention, introduces nanofluid working fluids into the interior of a heat pipe grinding head and utilizes ultrasonic vibration to enhance its dispersion stability, thereby improving grinding heat dissipation and processing performance, falls within the scope of protection of this invention.

Claims

1. An integrated ultrasonically excited nanofluid-modified heat pipe grinding head, characterized in that, include: Handle housing (1); An ultrasonic transducer assembly is disposed within the outer shell (1) of the tool holder; The heat pipe grinding head base (6) also functions as an amplitude transformer and has a vacuum heat pipe cavity inside. The vacuum heat pipe cavity includes a condensation section (6a), an insulation section (6b), and an evaporation section (6c) in sequence along the axial direction. The vacuum heat pipe cavity is filled with a nanofluid working fluid (15). The condensing section (6a) and the insulating section (6b) of the heat pipe grinding head base (6) constitute an ultrasonic amplitude transformer, which is used to transmit ultrasonic vibration to the grinding arc area (14). The ultrasonic vibration generated by the ultrasonic transducer during operation is directly transmitted to the grinding arc zone (14) through the heat pipe grinding head substrate (6), and simultaneously acts on the nanofluid working medium (15) in the vacuum heat pipe cavity to disperse the nanoparticles in the nanofluid working medium (15).

2. The integrated ultrasonically excited nanofluid-modified heat pipe grinding head according to claim 1, characterized in that, The ultrasonic transducer assembly includes a rear cover plate (8), a piezoelectric ceramic sheet (10), and an upper end (12) of a heat pipe grinding head base. The rear cover plate (8) is used to press the piezoelectric ceramic sheet (10) and provide axial prestress. The piezoelectric ceramic sheet (10) is an annular piezoelectric ceramic sheet stacked along the axial direction. The upper end (12) of the heat pipe grinding head base passes through the central hole of the piezoelectric ceramic sheet (10) and forms a series pre-tightening structure with the rear cover plate (8) and the lower part of the heat pipe grinding head base (6) so that the ultrasonic vibration generated by the piezoelectric ceramic sheet (10) is directly transmitted to the heat pipe grinding head base (6).

3. The integrated ultrasonically excited nanofluid-modified heat pipe grinding head according to claim 2, characterized in that, It also includes a locking nut (3), a pull stud (7), an outer plug (11), and a connecting screw (9); the upper end (12) of the heat pipe grinding head base is threadedly connected to the outer plug (11); the locking nut (3) is used to connect the tool holder housing (1) and the heat pipe grinding head base (6), and to apply axial clamping force to the upper end (12) of the heat pipe grinding head base; the connecting screw (9) passes downward from the upper part of the heat pipe grinding head base (6), passes through the rear cover plate (8) and the piezoelectric ceramic plate (10) in sequence, and is connected to the upper step inside the outer plug (11); an O-ring (2) is provided between the connecting screw (9) and the upper end (12) of the heat pipe grinding head base.

4. The integrated ultrasonically excited nanofluid-modified heat pipe grinding head according to claim 1, characterized in that, The outer wall of the condensation section (6a) is provided with a spiral groove (5), which forms a heat dissipation fin and is also constructed to convert ultrasonic longitudinal vibration into longitudinal torsional vibration mode.

5. The integrated ultrasonically excited nanofluid-modified heat pipe grinding head according to claim 1, characterized in that, The diameter of the insulating section (6b) gradually decreases along the axial direction from the condensing section (6a) to the evaporating section (6c), and its outer contour is conical or exponential to form the amplitude amplification structure of the ultrasonic amplitude transformer; the outer layer of the insulating section (6b) is coated with insulating material.

6. The integrated ultrasonically excited nanofluid-modified heat pipe grinding head according to claim 1, characterized in that, The outer wall of the evaporation section (6c) is provided with an abrasive layer as a grinding working surface; the inner wall of the evaporation section (6c) is provided with a raised micropillar structure to enhance capillary force, expand the heat exchange area and promote uniform wetting and reflux of nanofluid.

7. The integrated ultrasonically excited nanofluid-modified heat pipe grinding head according to claim 1, characterized in that, The inner wall of the condensation section (6a) is provided with a hydrophilic-hydrophobic composite structure to accelerate the shedding of condensate droplets and reduce thermal resistance.

8. A method of using the integrated ultrasonically excited nanofluid-modified heat pipe grinding head according to any one of claims 1 to 7, characterized in that, Includes the following steps: Step a: Vacuum the vacuum heat pipe cavity of the heat pipe grinding head substrate (6) through the transverse injection channel (13) and the longitudinal injection channel (4), and inject nanofluid working fluid (15) into the vacuum heat pipe cavity. Step b: Seal the transverse injection channel (13) and the longitudinal injection channel (4) through the upper end (12) of the heat pipe grinding head base, the outer plug (11), the connecting screw (9) and the O-ring (2); Step c: Install the tool holder housing (1) onto the machine tool spindle using the pull stud (7), turn on the ultrasonic power supply, and drive the heat pipe grinding head substrate (6) to generate ultrasonic vibration using the piezoelectric ceramic sheet (10); Step d: Start the machine tool to perform grinding, so that the evaporation section (6c) absorbs the grinding heat. The nanofluid working medium (15) is heated and evaporated, then flows to the condensation section (6a) to release heat and condense, and then flows back to the evaporation section (6c) to form a thermal cycle.

9. The method of using the integrated ultrasonically excited nanofluid-modified heat pipe grinding head according to claim 8, characterized in that, During the grinding process, the ultrasonic vibration acts simultaneously on the grinding arc zone (14) and the nanofluid working medium (15) in the vacuum heat pipe cavity to reduce the agglomeration of nanoparticles, and in conjunction with the spiral groove (5) on the outer periphery of the condensation section (6a) to enhance heat transfer, thereby simultaneously improving the grinding performance and the heat transfer performance of the heat pipe.

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