Ultrasonic-assisted machining interface temperature measurement method and ultrasonic-assisted machining system

Abstract

The application discloses an ultrasonic auxiliary processing interface temperature measuring method, which is based on an ultrasonic frequency erodible artificial thermocouple, electromagnetic shielding protection measures are taken for an ultrasonic transducer, a workpiece, a thermocouple temperature measuring part and a thermocouple temperature signal transmission route, so that the transient temperature measurement interference of ultrasonic power and power frequency power on an ultrasonic vibration auxiliary processing interface is avoided when the ultrasonic power and the power frequency power are working; meanwhile, the installation direction of the thermocouple is adjusted, so that the temperature change of the ultrasonic vibration auxiliary processing interface in a single vibration cutting period can be directly measured, and data support and a theoretical basis are provided for further improvement of process parameters of ultrasonic vibration auxiliary processing. The application further provides an ultrasonic auxiliary processing system, which can directly measure the temperature change of the ultrasonic vibration auxiliary processing interface in a single vibration cutting period in the ultrasonic auxiliary processing process.

Description

Technical Field

[0001] This invention belongs to the field of machining and relates to a machining temperature measurement technology, particularly to an ultrasonic-assisted machining interface temperature measurement method and ultrasonic-assisted machining system. Background Technology

[0002] The machining interface temperature is the temperature at the interface between the tool and the workpiece during machining. Excessively high machining interface temperatures can lead to rapid tool wear, workpiece surface ablation, and surface damage such as microcracks, white layers, and residual tensile stress. Therefore, it is essential to avoid excessively high machining interface temperatures during the machining process.

[0003] Ultrasonic vibration-assisted machining (UAVAM) involves applying ultrasonic frequency vibrations to a cutting tool, causing the machining interface to open and close periodically at ultrasonic frequencies. The tool is typically mounted on an ultrasonic transducer and connected to an ultrasonic power source, enabling the tool to machine the workpiece via ultrasonic vibration. The machining process is divided into a cutting section and a separation section based on the opening and closing of the machining interface. In the separation section, the cooling medium more easily enters the high-temperature machining interface for cooling and lubrication, effectively reducing the interface temperature and improving tool life and workpiece surface quality. However, due to limitations in current temperature measurement technology, the specific temperature changes of the machining interface in the cutting and separation sections of UAVAM remain unknown, hindering further improvements to the process.

[0004] To better understand the cooling mechanism of ultrasonic vibration-assisted machining, it is necessary to analyze the temperature changes caused by the opening and closing of the machining interface within the microsecond-level vibration cycle. Currently, temperature measurement methods with microsecond-level response rates mainly include non-contact radiation thermometry and contact thin-film thermocouple thermometry. Radiation thermometry is difficult to obtain accurate real-time machining interface temperature due to the obstruction of chips and tools. Thin-film thermocouple thermometry utilizes the thin-film thermocouple to measure temperature by adhering to the tool surface during cutting. However, the hot junction of the thin-film thermocouple must operate within the insulating protective layer, making it impossible to directly measure the machining interface temperature. Furthermore, the bonding force between the thin-film thermocouple and the tool substrate is limited, and the impact of ultrasonic frequencies accelerates the detachment and failure of the thin-film thermocouple, making it less suitable for ultrasonic vibration-assisted machining.

[0005] Another type of ultrasonic frequency-erodible artificial thermocouple can achieve microsecond-level temperature measurement capabilities by machining micron-sized hot junctions on its temperature-sensing end face. This allows for direct measurement of transient temperature changes at the ultrasonic vibration-assisted machining interface between the cutting and separating sections. While this type of ultrasonic frequency-erodible artificial thermocouple has high sensitivity, it is susceptible to electromagnetic interference during use. Appropriate electromagnetic shielding protection measures are required for its application in ultrasonic-assisted machining interface temperature measurement where both ultrasonic and power frequency power supplies work together. However, currently, there are no feasible electromagnetic shielding protection measures, hindering the application of ultrasonic frequency-erodible artificial thermocouples in ultrasonic-assisted machining interface temperature measurement. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for measuring the interface temperature in ultrasonic-assisted machining, which can directly and accurately obtain the transient temperature of the cutting interface between the cutting section and the separation section within the ultrasonic vibration cycle, reveal the cooling mechanism of ultrasonic vibration-assisted cutting, and solve the problem that ultrasonically erodible artificial thermocouples are easily affected by electromagnetic interference and have poor temperature measurement accuracy when used in ultrasonic-assisted machining interface temperature measurement.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] (I) This invention provides a method for measuring the interface temperature in ultrasonic-assisted machining, comprising:

[0009] Electromagnetic shielding is applied to the ultrasonic transducer;

[0010] Electromagnetic shielding is applied to the workpiece;

[0011] Electromagnetic shielding is applied to the temperature measuring probe and temperature signal transmission line of the ultrasonically erodible artificial thermocouple.

[0012] The temperature probe is pre-embedded below the workpiece surface to be machined at a position less than the depth of cut, and the hot junction generation area on the end face of the temperature probe overlaps with the tool movement trajectory. The transient temperature change of the ultrasonic vibration assisted machining interface in the cutting section and the separation section is measured by the micron-level hot junction formed in the hot junction generation area during ultrasonic vibration assisted machining.

[0013] Optionally, the electromagnetic shielding of the ultrasonic transducer includes:

[0014] Insulating gaskets are installed between the piezoelectric ceramic stack and the rear cover plate, and between the piezoelectric ceramic stack and the amplitude transformer.

[0015] An insulating tape layer or insulating paint coating is provided on the outer surface of the bolts used to sequentially connect and pre-tighten the rear cover plate, the piezoelectric ceramic stack and the amplitude transformer.

[0016] The outer surface of the ultrasonic transducer is covered from the inside out with an inner insulating layer, a middle electromagnetic shielding layer, and an outer insulating layer.

[0017] Optionally, the electromagnetic shielding of the workpiece includes:

[0018] Insulating gaskets or insulating coatings are provided between the contact surfaces of the workpiece and the tooling, and between the contact surfaces of the workpiece and the machine tool.

[0019] Optionally, the electromagnetic shielding of the temperature measuring probe of the ultrasonically erodible artificial thermocouple includes: wrapping the temperature measuring probe with a probe insulation layer.

[0020] The electromagnetic shielding of the temperature signal transmission line of the ultrasonically erodible artificial thermocouple includes: covering the outside of the temperature signal transmission line with a shielded cable to form a line armor layer.

[0021] Optionally, the part where the thermal junction generation area on the end face of the temperature probe overlaps with the tool movement trajectory includes:

[0022] The long side of the hot junction generation region is tangent to or coincides with the instantaneous main motion trajectory of the tool, and is parallel to the direction of the instantaneous main cutting speed of the tool;

[0023] Make the short side of the hot junction generation region parallel to the cutting feed direction of the tool.

[0024] (II) This invention also proposes an ultrasonic-assisted machining system, including a cutting tool and a machine tool, wherein the cutting tool is connected to an ultrasonic power supply via an ultrasonic transducer. The system is characterized by further including an ultrasonic frequency-abrasive artificial thermocouple and a signal acquisition system, wherein the ultrasonic power supply, the machine tool, and the ultrasonic frequency-abrasive artificial thermocouple are all communicatively connected to the signal acquisition system, wherein:

[0025] Insulating gaskets are provided between the piezoelectric ceramic stack and the rear cover plate of the ultrasonic transducer, and between the piezoelectric ceramic stack and the amplitude transformer; an insulating tape layer or insulating paint coating is provided on the outer surface of the bolts of the ultrasonic transducer used to sequentially connect and pre-tighten the rear cover plate, the piezoelectric ceramic stack and the amplitude transformer; the outer surface of the ultrasonic transducer is provided with an inner insulating layer, a middle electromagnetic shielding layer and an outer insulating layer from the inside to the outside.

[0026] Electromagnetic shielding structures are provided on the exterior of the temperature measuring probe of the ultrasonic frequency erodible artificial thermocouple, as well as on the exterior of the temperature signal transmission line between the ultrasonic frequency erodible artificial thermocouple and the signal acquisition system. A hot junction generation area is provided on the end face of the temperature measuring probe. The temperature measuring probe is pre-embedded below the workpiece surface to be processed at a position less than the depth of cut, so that the hot junction generation area can overlap with the tool movement trajectory during ultrasonic vibration assisted processing. The micron-level hot junction formed by the hot junction generation area is used to measure the transient temperature change of the ultrasonic vibration assisted processing interface in the cutting and separation sections.

[0027] Optionally, the electromagnetic shielding structure outside the temperature probe includes a probe insulation layer covering the outside of the temperature probe;

[0028] The electromagnetic shielding structure outside the temperature signal transmission line is a line armor layer formed by covering the outside of the temperature signal transmission line with a shielded cable.

[0029] Optionally, the hot junction generation area is a rectangular area, and the pre-embedded position of the temperature probe on the workpiece surface to be processed satisfies the following conditions:

[0030] The long side of the hot junction generation region is tangent to or coincides with the instantaneous main motion trajectory of the tool, and is parallel to the direction of the instantaneous main cutting speed of the tool;

[0031] The short side of the hot junction generation region is parallel to the cutting feed direction of the tool.

[0032] Optionally, the response frequency of the ultrasonically erodible artificial thermocouple and the sampling frequency of the signal acquisition system are both not less than twice the vibration frequency of the cutting tool.

[0033] Optionally, the machine tool is, but is not limited to, a lathe, a milling machine, or a drilling machine; the cutting tool is, but is not limited to, a lathe tool, a milling cutter, or a drill bit.

[0034] Optionally, a cooling mechanism may also be included, which is used to cool the ultrasonic vibration-assisted processing interface.

[0035] Optionally, the cooling mechanism may be one or more combinations of, but not limited to, gas cooling mechanism, casting cooling mechanism, high-pressure cooling mechanism, micro-lubrication cooling mechanism and nanofluid micro-lubrication cooling mechanism.

[0036] Optionally, the ultrasonic power source can provide ultrasonic vibration-assisted machining for the cutting tool in the form of one-dimensional ultrasonic vibration-assisted machining, two-dimensional elliptical ultrasonic vibration-assisted machining, two-dimensional normal ultrasonic vibration-assisted machining, and three-dimensional ultrasonic vibration-assisted machining.

[0037] Optionally, the cutting tool can generate ultrasonic vibrations with a frequency of 16kHz to 60kHz and a bilateral amplitude of 1μm to 50μm under the action of the ultrasonic power source.

[0038] Optionally, the vibration parameters controlled by the ultrasonic power supply include vibration frequency, bilateral amplitude of the cutting tool, and vibration phase.

[0039] Optionally, the machining parameters of the ultrasonic-assisted machining include tool angle, cutting speed, cutting depth, cutting width, and feed rate.

[0040] The present invention achieves the following technical effects compared to the prior art:

[0041] The ultrasonic-assisted machining interface temperature measurement method proposed in this invention, based on the use of a high-sensitivity ultrasonic frequency-abrasive artificial thermocouple, employs electromagnetic shielding protection measures for the workpiece, ultrasonic transducer, thermocouple temperature measurement section, and thermocouple temperature signal transmission path. This avoids interference from the ultrasonic power supply and power frequency power supply during operation on the transient temperature measurement of the ultrasonic vibration-assisted machining interface. Simultaneously, the installation orientation of the thermocouple has been adjusted, allowing direct measurement of the temperature changes of the cutting and separation sections of the ultrasonic vibration-assisted machining interface within a single vibration cutting cycle using the ultrasonic frequency-abrasive artificial thermocouple. The measurement temperature error is controlled within 2℃ to 3℃, enabling quantitative evaluation of the cutting heat generation process within the vibration cutting cycle and the cooling and lubrication effects of different cooling methods and media on the machining interface in the separation section. This reveals the cooling mechanism of the ultrasonic vibration-assisted machining process and provides data support and theoretical basis for further improving the process parameters of ultrasonic vibration-assisted machining.

[0042] The ultrasonic-assisted machining system proposed in this invention employs electromagnetic shielding protection measures for the workpiece, ultrasonic transducer, ultrasonic frequency erodible artificial thermocouple temperature measurement section, and thermocouple temperature signal transmission route. Simultaneously, the installation orientation of the ultrasonic frequency erodible artificial thermocouple is adjusted, thereby enabling direct measurement of the temperature changes of the cutting and separation sections of the ultrasonic vibration-assisted machining interface within a single vibration cutting cycle during ultrasonic-assisted machining. The measurement temperature error is controlled within 2℃ to 3℃. This allows for quantitative evaluation of the cutting heat generation process within the vibration cutting cycle, as well as the cooling and lubrication effects of different cooling methods and media at the separation section of the machining interface. It reveals the cooling mechanism of ultrasonic vibration-assisted machining, providing data support and a theoretical basis for further improving the process parameters of ultrasonic vibration-assisted machining. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the processing interface;

[0045] Figure 2 Schematic diagram illustrating the division of the cutting and separation sections within an ultrasonic vibration-assisted cutting cycle;

[0046] Figure 3A This is a schematic diagram of one-dimensional ultrasonic vibration-assisted machining.

[0047] Figure 3B This is a schematic diagram of ultrasonic vibration-assisted machining of a two-dimensional ellipse.

[0048] Figure 3C This is a schematic diagram of two-dimensional normal ultrasonic vibration-assisted machining;

[0049] Figure 3D This is a schematic diagram of three-dimensional ultrasonic vibration-assisted machining.

[0050] Figure 4A This is a schematic diagram of the structure of an ultrasonically erodible artificial thermocouple.

[0051] Figure 4B This is a schematic diagram of the assembly orientation for measuring the transient temperature of the machining interface using an ultrasonically abrasive artificial thermocouple as disclosed in an embodiment of the present invention.

[0052] Figure 5 This is a schematic diagram of the structure of the ultrasonic transducer disclosed in the embodiment of the present invention (with an electromagnetic shielding structure);

[0053] Figure 6A This is a schematic diagram of ultrasonic vibration-assisted end face turning disclosed in Embodiment 1 of the present invention;

[0054] Figure 6B This is a schematic diagram of ultrasonic vibration-assisted external cylindrical turning disclosed in Embodiment 1 of the present invention;

[0055] Figure 6C This is a schematic diagram of the principle of the ultrasonic vibration-assisted end-face turning interface transient temperature measurement method disclosed in Embodiment 1 of the present invention;

[0056] Figure 7A This is a schematic diagram of ultrasonic vibration-assisted end face milling disclosed in Embodiment 2 of the present invention;

[0057] Figure 7B This is a schematic diagram of ultrasonic vibration-assisted outer edge milling as disclosed in Embodiment 2 of the present invention;

[0058] Figure 7C This is a schematic diagram illustrating the principle of the ultrasonic vibration-assisted end-face milling interface transient temperature measurement method disclosed in Embodiment 2 of the present invention;

[0059] Figure 8A This is a schematic diagram of ultrasonic vibration-assisted drilling disclosed in Embodiment 3 of the present invention;

[0060] Figure 8B This is a schematic diagram illustrating the principle of the ultrasonic vibration-assisted external turning, external milling, and drilling interface transient temperature measurement method disclosed in this embodiment of the invention.

[0061] Figure 9 This is a schematic diagram illustrating the peak temperature variation at the interface during ultrasonic vibration-assisted end-face turning of stainless steel with variable cutting speed, as disclosed in an embodiment of the present invention.

[0062] Figure 10 This is a schematic diagram of the transient temperature change at the machining interface of ultrasonic-assisted end-face turning of titanium alloy Ti-6Al-4V, as disclosed in an embodiment of the present invention.

[0063] The attached figures are labeled as follows:

[0064] 1-Cutting tool, 11-Lathe tool, 12-End milling cutter, 13-Drill bit;

[0065] 2-Workpiece; 21. Tool-Workpiece Machining Interface;

[0066] 3-Chips;

[0067] 4-Ultrasonic frequency erodible artificial thermocouple; 41-Temperature probe; 411-Probe insulation layer; 412-Probe armor layer; 413-Probe insulation filling layer; 414-Thermoelectrode material A; 415-Thermoelectrode material B; 416-Insulation layer; 42-Thermojunction; 43-Temperature signal transmission line; 44-Connector; 45-Thermojunction generation area;

[0068] 5-Ultrasonic transducer, 51-Piezoelectric ceramic sheet, 52-Conductive copper sheet, 53-Insulating gasket, 54-Rear cover plate, 55-Bolt, 56-Amplitude rod, 57-Inner insulation layer, 58-Middle electromagnetic shielding layer, 59-Outer insulation layer. Detailed Implementation

[0069] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0070] One of the objectives of this invention is to provide a method for measuring the interface temperature in ultrasonic-assisted machining, in order to solve the problem that ultrasonically abrasive artificial thermocouples are easily affected by electromagnetic interference and have poor temperature measurement accuracy when used in ultrasonic-assisted machining interface temperature measurement. This method can directly and accurately obtain the transient temperature of the cutting interface between the cutting section and the separation section within the ultrasonic vibration cycle, and reveal the cooling mechanism of ultrasonic vibration-assisted cutting.

[0071] Another objective of this invention is to provide an ultrasonic-assisted machining system that addresses the problem of poor temperature measurement accuracy caused by electromagnetic interference when using ultrasonically abrasive artificial thermocouples for interface temperature measurement in ultrasonic-assisted machining. This system can directly and accurately obtain the transient temperature of the cutting interface between the cutting section and the separation section within the ultrasonic vibration cycle, revealing the cooling mechanism of ultrasonic vibration-assisted cutting.

[0072] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0073] Example 1

[0074] This embodiment provides a method for measuring the interface temperature in ultrasonic-assisted machining. This method is based on a high-sensitivity ultrasonic-frequency erodible artificial thermocouple 4 and employs a series of shielding measures to avoid electromagnetic interference generated by the operation of the ultrasonic power supply and the power frequency power supply. Simultaneously, by adjusting the installation orientation of the ultrasonic-frequency erodible artificial thermocouple 4, the transient changes in the interface temperature during the cutting and separation stages of ultrasonic vibration-assisted machining can be directly measured. The aforementioned shielding measures mainly include full-path electromagnetic shielding of the temperature signal from generation and transmission to acquisition. Specifically, this includes electromagnetic shielding of the ultrasonic transducer 5 in the ultrasonic-assisted machining system, electromagnetic shielding of the workpiece 2, electromagnetic shielding of the temperature measuring part of the ultrasonic-frequency erodible artificial thermocouple 4 (i.e., the temperature measuring probe 41), and the use of shielded wire to form an armor layer along the entire temperature signal transmission path of the ultrasonic-frequency erodible artificial thermocouple 4, thereby achieving insulation shielding between the ultrasonic-frequency erodible artificial thermocouple 4 and the machine tool and workpiece 2. The ultrasonic power supply, machine tool, ultrasonic-frequency erodible artificial thermocouple 4, and signal acquisition system in the ultrasonic-assisted machining system are all connected and grounded. The aforementioned method for measuring the transient temperature of the interface in ultrasonic vibration-assisted machining can be applied to ultrasonic vibration-assisted turning of titanium alloys, such as... Figures 6A to 6C , Figure 8B As shown.

[0075] Specifically, in this embodiment, insulating shielding is applied both inside and outside the ultrasonic transducer 5. Internally, insulating gaskets 53 are placed between the piezoelectric ceramic stack and the amplitude transformer 56, and between the piezoelectric ceramic stack and the rear cover plate 54. An insulating layer is also applied to the surface of the bolts 55 that sequentially connect the amplitude transformer 56, the piezoelectric ceramic stack, and the rear cover plate 54, achieving the effect of internal insulating shielding of the ultrasonic transducer 5 to prevent the cutting tool 1 mounted on the ultrasonic transducer 5 from becoming electrified. Simultaneously, external insulating shielding is also applied to the ultrasonic transducer 5. This is achieved by sequentially applying an inner insulating layer 57, a middle electromagnetic shielding layer 58, and an outer insulating layer 59 from the inside out on the outside of the ultrasonic transducer 5. The middle electromagnetic shielding layer 58 is formed by covering the inner insulating layer 57 with electromagnetic shielding material, while the outer insulating layer 59 is formed by covering the middle electromagnetic shielding layer 58 with a high-hardness insulating material, facilitating mechanical clamping on a machine tool. In the aforementioned ultrasonic transducer 5, the piezoelectric ceramic stack is mainly composed of multiple layers of piezoelectric ceramic sheets 51 stacked together, and a conductive copper sheet 52 is provided between each two adjacent layers of piezoelectric ceramic sheets 51. This piezoelectric ceramic stack is an existing structure, and its specific structural configuration and working principle will not be described in detail here.

[0076] Specifically, in this embodiment, when the workpiece 2 is clamped onto the machine tool by the tooling, insulating pads or insulating coatings are provided on the contact surfaces between the workpiece 2 and the tooling, and between the workpiece 2 and the machine tool.

[0077] Specifically, in this embodiment, the power line of the ultrasonic transducer 5 and the temperature signal transmission line 43 of the ultrasonic frequency erodible artificial thermocouple 4 are both covered with shielded cables. The ultrasonic transducer 5, the ultrasonic frequency erodible artificial thermocouple 4 and the signal acquisition system are all connected to the machine tool and then grounded.

[0078] In this embodiment, the cutting system used in ultrasonic vibration assisted machining includes a machine tool and a cutting tool 1. The cutting tool 1 on the machine tool is connected to an ultrasonic power supply through the aforementioned ultrasonic transducer 5 to process the workpiece with ultrasonic vibration. By setting the processing parameters of the cutting tool 1 and the vibration parameters of the ultrasonic power supply, the processing interface between the cutting tool 1 and the workpiece 2 is periodically opened and closed at ultrasonic frequency. Taking ultrasonic vibration-assisted end-face turning on a lathe as an example, the tool 1 is the lathe tool 11, and the ultrasonic transducer 5 is clamped on the lathe spindle. After the ultrasonic power supply and machine tool are turned on, the lathe tool 11, mounted on the front end of the amplitude transformer 56 of the ultrasonic transducer 5, begins ultrasonic vibration-assisted turning. When the lathe tool 11 vibrates axially, the vibration direction is perpendicular to the surface where the main motion trajectory of the lathe tool 11 is located. When the lathe tool 11 vibrates radially, the vibration direction is perpendicular to the instantaneous main motion velocity direction of the lathe tool 11, and points to the axis of the workpiece 2 in external turning or to the center of the main motion trajectory of the lathe tool 11 in end-face turning. When the lathe tool 11 performs elliptical ultrasonic vibration, the vibration of the lathe tool 11 is the resultant motion of axial and radial vibration, and the plane of the vibration trajectory of the lathe tool 11 is perpendicular to the instantaneous main motion velocity direction of the lathe tool 11. When the lathe tool 11 performs three-dimensional ultrasonic vibration, the vibration of the lathe tool 11 is the resultant motion of the axial, radial and tangential vibrations of the instantaneous main motion trajectory of the tool. Under normal circumstances, after the ultrasonic power supply is turned on, the cutter 1 can obtain ultrasonic frequency vibration with a frequency of 16kHz to 60kHz and a bilateral amplitude of 1μm to 50μm.

[0079] In practical operation, a cooling mechanism can be set up in the ultrasonic-assisted machining system for ultrasonic vibration-assisted end-face turning. The cooling mechanism is configured to control the machining cooling method (dry cooling) and the cooling medium (room temperature air). By combining cutting parameters (e.g., main motion cutting line speed of 100m / min, depth of cut of 10μm, feed rate of 20μm) and vibration parameters (e.g., axial vibration, vibration frequency of 18400Hz, bilateral amplitude of 15μm, phase difference of 180°), the separation degree of the tool-workpiece machining interface 21 and the interface cooling and lubrication mode are changed to achieve the effect of cooling the machining interface.

[0080] Furthermore, in this embodiment, after employing a series of shielding measures, the ultrasonically abrasive artificial thermocouple 4 can be positioned and installed in the workpiece's machining area, ensuring that the hot junction generation area 45 on the temperature-sensing end face of the ultrasonically abrasive artificial thermocouple 4 overlaps with the movement trajectory of the tool 1. This allows for the direct measurement of transient temperature changes at the machining interface using the micron-level hot junction 42 formed during ultrasonic vibration-assisted machining. Subsequently, the temperature signal is acquired by the signal acquisition system. To satisfy the Nyquist sampling theorem, both the response frequency of the ultrasonically abrasive artificial thermocouple 4 and the sampling frequency of the signal acquisition system should be at least twice the vibration frequency of the cutting tool 11.

[0081] Specifically, as a preferred option, such as Figure 4BAs shown, the temperature probe 41 is provided with a probe insulation layer 411, a probe armor layer 412, a probe insulation filling layer 413 and a thermoelectric material from the outside to the inside. The thermoelectric material includes thermoelectric material A414 and thermoelectric material B415, and an insulation layer 416 is provided between thermoelectric material A414 and thermoelectric material B415.

[0082] Specifically, as a preferred embodiment, the temperature sensing end face of the temperature sensing probe 41 of the ultrasonically erodible artificial thermocouple 4 is pre-embedded below the surface of the workpiece 2 to be processed at a position less than the depth of a single cut, and the two thermoelectrode materials within the ultrasonically erodible artificial thermocouple 4, namely... Figure 4B The thermal junction generation region 45 between the thermoelectric electrode material A414 and the thermoelectric electrode material B415 shown overlaps with the tool movement trajectory, with the overlap width B > feed amount f. Specifically, the long side of the rectangular or near-rectangular (close to rectangular) thermal junction generation region 45 is parallel to or overlaps with the instantaneous main motion velocity direction of the tool at the pre-embedded position, and the short side of the thermal junction generation region 45 is parallel to the tool feed direction. The temperature measuring end face of the temperature measuring probe 41 of the ultrasonic frequency erodible artificial thermocouple 4 is perpendicular to the tool vibration direction.

[0083] During the cutting process, the tool 1 will approach the hot junction generation region 45 of the ultrasonic erodible artificial thermocouple 4 with each feed. The closer the tool 1 is to the hot junction, the more accurate the measured temperature. Based on the temperature measuring radius of the hot junction, the blunt radius of the tool 1, and their geometric positional relationship, it can be calculated that the cutting interface temperature signal can be obtained in m feeds. Furthermore, based on the installation orientation and symmetrical structure of the ultrasonic erodible artificial thermocouple 4, the temperature measured is most accurate in approximately the m / 2th feed. The interface temperature within n cycles can be obtained in a single feed, which should satisfy the following two formulas:

[0084]

[0085]

[0086] Where r n is the blunt radius of tool 1, r is the temperature measurement radius of the hot junction, f is the cutting feed rate, l is the length of the area where the hot junction is generated on the temperature measurement end face of the temperature probe coincides with the tool trajectory, F is the ultrasonic vibration frequency of the tool, and V is the main cutting motion speed of the tool (i.e., the cutting speed of the tool without ultrasonic vibration).

[0087] In this embodiment, a micron-sized hot junction 42 can be generated on the temperature measuring end face of the temperature measuring probe 41 of the ultrasonic frequency erodible artificial thermocouple 4 during pre-grinding or ultrasonic vibration-assisted processing. The hot junction 42 can directly measure the temperature change of the processing interface during processing and generate the corresponding thermoelectric potential. The thermoelectric potential is acquired by the signal acquisition system, and the temperature measurement result can be displayed and stored by an oscilloscope.

[0088] like Figure 9 The figure shows the measured peak interface temperature of stainless steel during turning at cutting speeds of 100 m / min to 500 m / min, depth of cut of 15 μm, and feed rate of 20 μm. UVC-10 μm represents ultrasonic vibration cutting with air cooling and a tool amplitude of 10 μm on both sides, and UVC-20 μm represents ultrasonic vibration cutting with air cooling and a tool amplitude of 20 μm on both sides. Figure 9 It can be seen that the peak temperature of the cutting interface during the ultrasonic vibration-assisted machining cycle is lower than that of ordinary cutting. When the main cutting speed is ≤300m / min, the peak machining interface temperature with a tool amplitude of 10μm is lower than that with a tool amplitude of 20μm. This indicates that at low cutting speeds, the overall temperature of the machining interface is low (<50℃) because the temperature difference between the machining interface and the environment is small, and the difference in cooling heat transfer caused by different degrees of interface separation is not significant. However, due to the large difference in temperature rise caused by different tool amplitude impacts, the 20μm amplitude impact is obviously stronger and the temperature rise is greater. However, when the main cutting speed increases, the cutting heat generation increases significantly, and the overall temperature of the cutting interface rises accordingly. At this time, a greater degree of interface separation shows a better cooling effect. This result shows that in vibration cutting, a greater degree of interface separation does not necessarily mean a better cooling effect. The heat energy converted from the kinetic energy of the tool vibration impact, as well as the corresponding matching workpiece material, cooling method, and machining parameter settings should also be considered.

[0089] Therefore, the ultrasonic-assisted machining interface temperature measurement method using this technical solution has, for the first time, obtained the peak interface temperature within a cycle during ultrasonic vibration-assisted cutting, rather than the average temperature over multiple cycles at low frequencies. This temperature signal can more realistically reflect the heat generation mechanism of the cutting section and the cooling mechanism of the separation section during vibration machining, and evaluate the thermal shock experienced by the workpiece and the tool.

[0090] The number of interface temperature cycles, n, obtained in a single cutting feed depends on the overlap length between the thermal junction generation region 45 of the ultrasonic abrasive artificial thermocouple 4 and the tool path 1, as well as the cutting speed: the higher the cutting speed, the larger the vibration cutting wavelength of one cycle, and the fewer cycles are measured when the overlap length remains constant. To obtain the richest possible temperature signal, the ultrasonic abrasive artificial thermocouple 4 should be installed in the preferred orientation according to this technical solution.

[0091] Ultrasonic-assisted face turning of titanium alloy was performed under the following conditions: cutting speed of 100 m / min, depth of cut of 10 μm, feed rate of 0.02 mm, tool axial vibration with bilateral amplitude of 15 μm, and air cooling. The measured temperature of the machining interface under these conditions is as follows: Figure 10 As shown, Figure 10Figure (a) shows the temperature signal obtained from a single acquisition by the oscilloscope, with a total of 10,000 data points and a total recording time of 100ms, with each unit recording time being 10μs. Figure 10 In Figure (a), each temperature signal is the temperature signal measured after a single feed. During the feed process, the high-temperature tool 1 continuously approaches the ultrasonically erodible artificial thermocouple 4, so the temperature gradually rises until a peak value is reached. This peak value is shown in the figure. Figure 10 As shown in Figure (b). Figure 10 Figure (b) shows the transient temperature change of the vibration-assisted machining interface within one cycle. Based on the vibration frequency of 18400Hz, the duration of one vibration cycle is approximately 54μs. Based on the cutting depth and tool amplitude, the cutting segment duration is approximately 30μs, and the separation segment duration is approximately 24μs, which is consistent with the temperature signal characteristics obtained by the temperature measurement method of this technical solution.

[0092] Example 2

[0093] like Figures 7A to 7C , Figure 8B As shown, this embodiment applies the ultrasonic vibration-assisted machining interface transient temperature measurement method to the ultrasonic vibration-assisted milling process. The shielding measures used are exactly the same as those in Embodiment 1. The difference is that the machine tool in this embodiment is a milling machine, and the cutting tool 1 is a milling cutter 12. In the machining system, the ultrasonic transducer 5 is clamped on the milling machine spindle. After the ultrasonic power supply and milling machine are turned on, the milling cutter 12 mounted on the front end of the ultrasonic transducer 5's amplitude transformer 56 begins ultrasonic vibration-assisted milling. When the milling cutter 12 vibrates axially, the vibration direction is perpendicular to the surface where the main motion trajectory of the milling cutter 12 is located. When the milling cutter 12 vibrates radially, the vibration direction is perpendicular to the instantaneous main motion velocity direction of the milling cutter 12, and points to the axis of the workpiece 2 in outer edge milling or to the center of the main motion trajectory of the milling cutter 12 in end face milling. When the milling cutter 12 performs elliptical ultrasonic vibration, the vibration of the milling cutter 12 is the resultant motion of axial and radial vibration, and the plane of the tool vibration trajectory is perpendicular to the instantaneous main motion velocity direction of the milling cutter 12. When the milling cutter 12 performs three-dimensional ultrasonic vibration, the vibration of the milling cutter 12 is the resultant motion of the axial, radial, and tangential vibrations of the instantaneous main motion trajectory of the tool.

[0094] In practical operation, a cooling mechanism can be set up in the ultrasonic-assisted machining system for ultrasonic vibration-assisted milling. The cooling mechanism is configured to control the machining cooling method (dry cooling) and the cooling medium (room temperature air). By combining cutting parameters (e.g., main motion cutting line speed of 100m / min, depth of cut of 10μm, feed per tooth of 20μm) and vibration parameters (e.g., axial vibration, vibration frequency of 18400Hz, bilateral amplitude of 15μm, phase difference of 180°), the separation degree of the tool-workpiece machining interface 21 and the interface cooling and lubrication mode are changed to achieve the effect of cooling the machining interface.

[0095] Furthermore, in this embodiment, after employing a series of shielding measures, the ultrasonically abrasive artificial thermocouple 4 can be positioned and installed in the workpiece's machining area, ensuring that the hot junction generation area 45 on the temperature-sensing end face of the ultrasonically abrasive artificial thermocouple 4 overlaps with the movement trajectory of the cutting tool 1. This allows for the direct measurement of transient temperature changes at the machining interface using the micron-level hot junction 42 formed during ultrasonic vibration-assisted machining. Subsequently, the temperature signal is acquired by the signal acquisition system. To satisfy the Nyquist sampling theorem, both the response frequency of the ultrasonically abrasive artificial thermocouple 4 and the sampling frequency of the signal acquisition system should be at least twice the vibration frequency of the milling cutter 12.

[0096] Specifically, as a preferred embodiment, the temperature sensing end face of the temperature sensing probe 41 of the ultrasonically erodible artificial thermocouple 4 is pre-embedded below the surface of the workpiece 2 to be processed at a position less than the depth of a single cut, and the two thermoelectrode materials within the ultrasonically erodible artificial thermocouple 4, namely... Figure 4B The thermal junction generation region 45 between the thermoelectric electrode material A414 and the thermoelectric electrode material B415 shown overlaps with the tool movement trajectory, with the overlap width B > feed amount f. Specifically, the long side of the rectangular or near-rectangular (close to rectangular) thermal junction generation region 45 is parallel to or overlaps with the instantaneous main motion velocity direction of the tool at the pre-embedded position, and the short side of the thermal junction generation region 45 is parallel to the tool feed direction. The temperature measuring end face of the temperature measuring probe 41 of the ultrasonic frequency erodible artificial thermocouple 4 is perpendicular to the tool vibration direction.

[0097] In this embodiment, a micron-sized hot junction 42 can be generated on the temperature measuring end face of the temperature measuring probe 41 of the ultrasonic frequency erodible artificial thermocouple 4 during pre-grinding or ultrasonic vibration-assisted processing. The hot junction 42 can directly measure the temperature change of the processing interface during processing and generate the corresponding thermoelectric potential. The thermoelectric potential is acquired by the signal acquisition system, and the temperature measurement result can be displayed and stored by an oscilloscope.

[0098] Example 3

[0099] like Figures 8A-8BAs shown, this embodiment applies the ultrasonic vibration-assisted machining interface transient temperature measurement method to the ultrasonic vibration-assisted drilling process. The shielding measures used are exactly the same as those in Embodiment 1. The difference is that the machine tool in this embodiment is a drilling machine, and the cutting tool 1 is a drill bit 13. In the machining system, the ultrasonic transducer 5 is clamped on the drill spindle. After the ultrasonic power supply and the drill are turned on, the drill bit 13, mounted on the front end of the amplitude transformer 56 of the ultrasonic transducer 5, begins ultrasonic vibration-assisted drilling. When the drill bit 13 vibrates axially, the vibration direction is perpendicular to the surface of the main motion trajectory of the drill bit 13 and parallel to the feed direction of the drill bit 13. When the drill bit 13 vibrates radially, the vibration direction is perpendicular to the feed direction of the drill bit 13 and points to the axis of the main motion trajectory of the drill bit 13. When the drill bit 13 performs elliptical ultrasonic vibration, the vibration of the drill bit 13 is the resultant motion of axial and radial vibration, and the plane of the tool vibration trajectory is perpendicular to the instantaneous main motion velocity direction of the drill bit 13. When the drill bit 13 performs three-dimensional ultrasonic vibration, the vibration of the drill bit 13 is the resultant motion of the axial, radial and tangential vibrations of the instantaneous main motion trajectory of the tool.

[0100] In practical operation, a cooling mechanism can be set up in the ultrasonic-assisted machining system for ultrasonic vibration-assisted milling. The cooling mechanism is configured to control the machining cooling method (dry cooling) and the cooling medium (room temperature air). By combining cutting parameters (e.g., main motion cutting line speed of 100m / min, depth of cut of 10μm, feed per revolution of 20μm) and vibration parameters (e.g., axial vibration, vibration frequency of 18400Hz, bilateral amplitude of 15μm, phase difference of 180°), the separation degree of the tool-workpiece machining interface 21 and the interface cooling and lubrication mode are changed to achieve the effect of cooling the machining interface.

[0101] Furthermore, in this embodiment, after employing a series of shielding measures, the ultrasonically abrasive artificial thermocouple 4 can be positioned and installed in the workpiece's processing area, ensuring that the hot junction generation area 45 on the temperature-sensing end face of the ultrasonically abrasive artificial thermocouple 4 overlaps with the movement trajectory of the tool 1. This allows for the direct measurement of transient temperature changes at the processing interface using the micron-level hot junction 42 formed during ultrasonic vibration-assisted processing. Subsequently, the temperature signal is acquired by the signal acquisition system. To satisfy the Nyquist sampling theorem, both the response frequency of the ultrasonically abrasive artificial thermocouple 4 and the sampling frequency of the signal acquisition system should be at least twice the vibration frequency of the drill bit 13.

[0102] Specifically, as a preferred embodiment, the temperature sensing end face of the temperature sensing probe 41 of the ultrasonically erodible artificial thermocouple 4 is pre-embedded below the surface of the workpiece 2 to be processed at a position less than the depth of a single cut, and the two thermoelectrode materials within the ultrasonically erodible artificial thermocouple 4, namely... Figure 4BThe thermal junction generation region 45 between the thermoelectric electrode material A414 and the thermoelectric electrode material B415 shown overlaps with the tool movement trajectory, with the overlap width B > feed amount f. Specifically, the long side of the rectangular or near-rectangular (close to rectangular) thermal junction generation region 45 is parallel to or overlaps with the instantaneous main motion velocity direction of the tool at the pre-embedded position, and the short side of the thermal junction generation region 45 is parallel to the tool feed direction. The temperature measuring end face of the temperature measuring probe 41 of the ultrasonic frequency erodible artificial thermocouple 4 is perpendicular to the tool vibration direction.

[0103] In this embodiment, a micron-sized hot junction 42 can be generated on the temperature measuring end face of the temperature measuring probe 41 of the ultrasonic frequency erodible artificial thermocouple 4 during pre-grinding or ultrasonic vibration-assisted processing. The hot junction 42 can directly measure the temperature change of the processing interface during processing and generate the corresponding thermoelectric potential. The thermoelectric potential is acquired by the signal acquisition system, and the temperature measurement result can be displayed and stored by an oscilloscope.

[0104] Because ultrasonically erodible artificial thermocouples are highly sensitive but also highly susceptible to electromagnetic interference, this technical solution employs a series of electromagnetic shielding protection measures to avoid interference from the ultrasonic power supply and power frequency power supply during operation on the transient temperature measurement of the ultrasonic vibration-assisted machining interface. This technical solution not only directly measures the temperature changes of the cutting and separation sections of the ultrasonic vibration-assisted machining interface within a single vibration cutting cycle for the first time, but also performs transient temperature measurements on the ultrasonic vibration-assisted machining interface at the micrometer scale and microsecond response rate, controlling the measurement temperature error within 2℃~3℃. This allows for quantitative evaluation of the cutting heat generation process within the vibration cutting cycle, as well as the cooling effect of the machining interface in the separation section combined with different cooling methods and media. It reveals the cooling mechanism of the ultrasonic vibration-assisted machining process, providing data support and a theoretical basis for further improving the process parameters of ultrasonic vibration-assisted machining.

[0105] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0106] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for measuring interface temperature in ultrasonic-assisted machining, characterized in that, include: Electromagnetic shielding is implemented for the ultrasonic transducer; the electromagnetic shielding implementation for the ultrasonic transducer includes: placing insulating gaskets between the piezoelectric ceramic stack and the rear cover plate, and between the piezoelectric ceramic stack and the amplitude transformer; providing an insulating tape layer or insulating paint coating on the outer surface of the bolts used to sequentially connect and pre-tighten the rear cover plate, the piezoelectric ceramic stack, and the amplitude transformer; and sequentially covering the outer surface of the ultrasonic transducer with an inner insulating layer, a middle electromagnetic shielding layer, and an outer insulating layer from the inside out. Electromagnetic shielding is applied to the workpiece; the electromagnetic shielding of the workpiece includes: providing insulating pads or insulating coatings between the contact surfaces of the workpiece and the tooling, and between the contact surfaces of the workpiece and the machine tool. Electromagnetic shielding is applied to the temperature measuring probe and temperature signal transmission line of the ultrasonically erodible artificial thermocouple. The temperature probe is pre-embedded below the workpiece surface to be machined at a position less than the depth of cut, and the thermal junction generation area on the end face of the temperature probe coincides with the tool movement trajectory. The transient temperature change of the ultrasonic vibration-assisted machining interface during the cutting and separation sections is measured using the micron-level thermal junctions formed in the thermal junction generation area. The overlap between the thermal junction generation area on the end face of the temperature probe and the tool movement trajectory includes: the long side of the thermal junction generation area being tangent to or coincident with the instantaneous main motion trajectory of the tool and parallel to the instantaneous main cutting speed direction of the tool; and the short side of the thermal junction generation area being parallel to the tool cutting feed direction.

2. The method for measuring interface temperature in ultrasonic-assisted machining according to claim 1, characterized in that, The electromagnetic shielding of the temperature measuring probe of the ultrasonically erodible artificial thermocouple includes: An insulating layer is wrapped around the outside of the temperature probe; The electromagnetic shielding of the temperature signal transmission line of the ultrasonically erodible artificial thermocouple includes: covering the outside of the temperature signal transmission line with a shielded cable to form a line armor layer.

3. An ultrasonic-assisted machining system, comprising a cutting tool and a machine tool, wherein the cutting tool is connected to an ultrasonic power supply via an ultrasonic transducer, characterized in that, It also includes an ultrasonic frequency-erodible artificial thermocouple thermal and signal acquisition system, wherein the ultrasonic power supply, the machine tool, and the ultrasonic frequency-erodible artificial thermocouple are all communicatively connected to the signal acquisition system, wherein: Insulating gaskets are provided between the piezoelectric ceramic stack and the rear cover plate of the ultrasonic transducer, and between the piezoelectric ceramic stack and the amplitude transformer; an insulating tape layer or insulating paint coating is provided on the outer surface of the bolts of the ultrasonic transducer used to sequentially connect and pre-tighten the rear cover plate, the piezoelectric ceramic stack and the amplitude transformer; the outer surface of the ultrasonic transducer is provided with an inner insulating layer, a middle electromagnetic shielding layer and an outer insulating layer from the inside to the outside. Electromagnetic shielding structures are provided on the exterior of the temperature measuring probe of the ultrasonic frequency erodible artificial thermocouple, as well as on the exterior of the temperature signal transmission line between the ultrasonic frequency erodible artificial thermocouple and the signal acquisition system. A hot junction generation area is provided on the end face of the temperature measuring probe. The temperature measuring probe is pre-embedded below the workpiece surface to be processed at a position less than the depth of cut, so that the hot junction generation area can overlap with the tool movement trajectory during ultrasonic vibration assisted processing. The micron-level hot junction formed by the hot junction generation area is used to measure the transient temperature change of the ultrasonic vibration assisted processing interface in the cutting and separation sections.

4. The ultrasonic-assisted machining system according to claim 3, characterized in that, The electromagnetic shielding structure outside the temperature probe includes a probe insulation layer covering the outside of the temperature probe; The electromagnetic shielding structure outside the temperature signal transmission line is a line armor layer formed by covering the outside of the temperature signal transmission line with a shielded cable.

5. The ultrasonic-assisted machining system according to claim 3, characterized in that, The hot spot generation area is a rectangular area, and the pre-embedded position of the temperature probe on the workpiece surface to be processed meets the following conditions: The long side of the hot junction generation region is tangent to or coincides with the instantaneous main motion trajectory of the tool, and is parallel to the direction of the instantaneous main cutting speed of the tool; The short side of the hot junction generation region is parallel to the cutting feed direction of the tool.

6. The ultrasonic-assisted machining system according to claim 3, characterized in that, The response frequency of the ultrasonically erodible artificial thermocouple and the sampling frequency of the signal acquisition system are both no less than twice the vibration frequency of the cutting tool.

7. The ultrasonic-assisted machining system according to any one of claims 3 to 6, characterized in that, It also includes a cooling mechanism for cooling the ultrasonic vibration-assisted processing interface.

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