A method for micro-nano scale in-situ cutting observation and full-field deformation measurement

Abstract

The application discloses a method for micro-nano scale in-situ cutting observation and full-field deformation measurement, comprising the following steps: adjusting the relative position of a scanning electron microscope and an in-situ machining device, so that a machining platform in the in-situ machining device is located in the observation line-of-sight range of the scanning electron microscope; gradually cutting a workpiece by using a machining tool; after each cutting, the scanning electron microscope collects the micro-morphology image of the cutting area of the workpiece, so as to form a time sequence image sequence of the whole cutting process; the matrix decoupling type force sensor collects dynamic mechanical data of the whole cutting process in real time; according to the micro-morphology image, the morphology change and full-field deformation data in the cutting process are obtained, and are used for analyzing the micro and nano cutting mechanism. The application can establish the direct correlation of "microstructure-mechanical response", and effectively makes up for the problem that the existing simulation method is disconnected with the actual machining condition.

Description

Technical Field

[0001] This invention relates to the technical field of in-situ cutting analysis at the micro-nano scale, and in particular to a method for in-situ cutting observation and full-field deformation measurement at the micro-nano scale. Background Technology

[0002] Optical microscopes and high-speed photography systems are often used to observe macroscopic millimeter-scale cutting processes: Optical microscopes are limited by the diffraction limit, and the magnification is generally no more than 2000 times, which cannot distinguish key micro-nano-scale micro-features such as dislocations and subgrain boundaries inside the grains; although high-speed photography can capture the dynamic cutting process, it has the same problem of insufficient resolution as optical microscopes, and is not suitable for observing micro-nano-scale cutting processes, and cannot obtain micro-features such as the crystal structure of the sample.

[0003] Traditional observations based on physical images of cutting are insufficient to obtain the cutting deformation field and cannot deeply analyze the cutting deformation mechanism of materials, especially when the cutting depth enters the micrometer or even nanometer scale, where materials exhibit strong size effects—microstructures such as grain boundaries and grain orientation become key factors dominating deformation behavior. Traditional observation methods lack sufficient spatial resolution and quantitative analysis capabilities, failing to establish the intrinsic link between "microstructure evolution and macroscopic cutting response," severely restricting a deeper understanding of cutting mechanisms and precise process control.

[0004] Current research on in-situ cutting at the micro-nano scale mainly relies on two approaches: numerical simulation and experimental observation. However, both have significant bottlenecks, making it difficult to achieve closed-loop verification of "mechanism-phenomenon-law".

[0005] Currently, molecular methods for studying the micro / nano-scale cutting deformation process mainly rely on finite element method (FEM) simulation and molecular dynamics (MD). The FEM method can rapidly predict macroscopic parameters such as cutting forces and temperature fields by constructing material constitutive models and geometric boundary conditions, and is widely used in the optimization of conventional cutting processes. Molecular dynamics, on the other hand, can analyze microscopic mechanisms such as dislocation motion and grain boundary slip at the atomic level, revealing the essential process of material removal. However, both have significant limitations: the prediction accuracy of FEM simulation is highly dependent on the constitutive model, and existing models struggle to accurately describe the significant size effects, high strain rate strengthening, and grain boundary constraints in micro / nano cutting, leading to serious deviations between simulation results and experiments. While molecular dynamics possesses atomic-level resolution, its simulation scale is typically limited to tens of nanometers, far smaller than or equal to the micrometer-millimeter-scale feature sizes actually processed, and its computational cost increases exponentially with system scale, making it difficult to handle complex microstructures such as polycrystalline and heterogeneous materials, thus limiting its engineering applicability.

[0006] Digital image correlation (DIC) and particle image velocimetry (PIV) are mainstream image processing techniques for analyzing strain and strain rate fields during the actual deformation process of materials, and are currently widely used in conventional mechanical tests such as tensile and compressive stresses on various materials. In recent years, DIC has also been combined with high-speed photography to analyze the strain field during the cutting process, but this is limited to millimeter-scale cutting. For micro / nano-scale cutting, due to the resolution limitations of optical imaging, there are currently no studies using DIC and PIV to analyze the micro / nano-scale cutting deformation process to obtain strain and strain rate fields.

[0007] Scanning electron microscopy (SEM), with its nanometer-scale spatial resolution, wide field-of-view adjustment capability, and excellent environmental adaptability, has become an ideal platform for in-situ observation of micro- and nano-machining. Although several in-situ SEM fabrication devices have been developed in recent years, the overall field is still in its early stages, particularly in supporting quantitative full-field deformation measurements, where the following core shortcomings remain: 1) Weak cutting force measurement capability. Cutting force is a key physical quantity for analyzing the removal mechanism, but existing devices generally lack high-precision force measurement capabilities; they can usually only observe the ductile-brittle transition behavior of single-crystal silicon without integrating any force measurement module. Existing technologies also attempt to infer the cutting force through image displacement, but the accuracy heavily depends on the image matching algorithm, resulting in large errors and unreliability. If a spring-type stage is used for indirect force measurement, it is easily affected by elastic nonlinearity, vibration noise, and range limitations, making it difficult to meet the sub-micro Newton force resolution requirements of micro-nano cutting.

[0008] 2) Existing technologies such as scanning electron microscopy (SEM) have poor compatibility with DIC and PIV techniques, making quantitative deformation analysis difficult. Current machining platforms cannot realize two-dimensional plane strain cutting deformation processes (i.e., during cutting, the tool width is greater than the workpiece cutting width, and the cutting width is much greater than the cutting depth; in this case, the deformation in the cutting width direction can be considered uniform, and two-dimensional plane strain cutting deformation will not occur). Furthermore, DIC and PIV imaging requires patterning of the deformed sample surface, which is highly dependent on two-dimensional plane strain conditions. Currently, no research has been found on methods for combining DIC and PIV techniques with micro / nano-scale cutting to analyze the micro / nano-scale deformation field of materials. Although DIC and PIV techniques have been successfully combined with EBSD in SEM in-situ tensile experiments to achieve a correlation between crystallographic and mechanical responses, existing cutting devices generally suffer from the following problems: the speckle pattern on the sample surface is not optimized for SEM imaging characteristics, resulting in low image correlation and distorted strain calculations; and a lack of stable imaging field of view and synchronous triggering mechanism makes it difficult to guarantee the image sequence quality required for DIC analysis.

[0009] In summary, existing systems mostly remain at the level of qualitative observation and cannot provide reliable quantitative data such as full-field strain and displacement. They cannot simultaneously achieve in-situ cutting observation integrating high-resolution imaging, high-precision force measurement, and full-field quantitative deformation, which seriously hinders the development and engineering application of fundamental theories of micro-nano cutting. Summary of the Invention

[0010] This invention aims to at least partially address one of the problems in related technologies. Therefore, one objective of this invention is to provide a method for in-situ cutting observation and full-field deformation measurement at the micro / nano scale. This method enables the simultaneous acquisition of SEM morphology, cutting force, and deformation field data, establishing a direct correlation between "microstructure and mechanical response." This provides reliable experimental evidence for revealing the cutting mechanism under scale effects, effectively overcoming the problem of existing simulation methods being disconnected from actual machining conditions.

[0011] A method for in-situ cutting observation and full-field deformation measurement at the micro / nano scale includes: The relative positions of the scanning electron microscope and the in-situ machining device are adjusted so that the machining platform in the in-situ machining device is within the observation line of the scanning electron microscope; the in-situ machining device includes a machining tool, a machining platform for clamping the workpiece, and a matrix decoupled force sensor for monitoring the force on the machining tool; The workpiece is cut step by step using a machining tool. After each cut, the scanning electron microscope acquires a microscopic morphology image of the workpiece's cutting area, thereby forming a time-series image sequence of the entire cutting process. The matrix decoupled force sensor acquires dynamic mechanical data of the entire cutting process in real time. Based on the microscopic morphology image, the strain field, strain rate field, and equivalent stress field are obtained through an image analysis model. The shear force F of the first shear band is then calculated based on the equivalent stress field. s1 Based on dynamic mechanical data, the shear force F of the first shear band is obtained. s1 The second shear force F at the corresponding moment s2 ; The shear force F of the first shear band s1 Second shear band shear force F s2 Cross-validation is performed. If the error between the two is less than or equal to the preset value, the strain field, strain rate field, and equivalent stress field after each cut are output. If the error between the two is greater than the preset value, the image analysis model is corrected to obtain the strain field, strain rate field, and equivalent stress field again.

[0012] Furthermore, the image analysis model includes a correction unit, an image analysis unit, and a material constitutive model, and the image analysis unit includes an image analysis algorithm; The strain field, strain rate field, and equivalent stress field are obtained through image analysis models; including: S1: The micro-morphology image is electronically drift-corrected by the correction unit to eliminate imaging deviation and form a corrected micro-morphology image; S2: The image analysis algorithm is used to analyze and calculate the corrected micro-morphology image to obtain the first velocity field, strain field, strain field component, strain rate field, and strain rate component. S3: Calculate the equivalent stress field based on the strain field, strain field components, strain rate field, and strain rate components, using the material constitutive model.

[0013] Furthermore, the image analysis unit includes at least one image analysis algorithm, and step S2 further includes: Cross-validation is performed on the first velocity field and the second velocity field to select image analysis algorithms with errors less than or equal to a preset value. Based on the selected image analysis algorithms, the first velocity field, strain field, strain field components, strain rate field, and strain rate components are obtained. The second velocity field is the cutting speed value set by the in-situ machining device.

[0014] Furthermore, the method for calculating the equivalent stress field in step S3 includes: ; ; ; in, A represents the equivalent stress field; B represents the yield stress under the reference condition; and C represents the strain hardening modulus. The expression represents the equivalent plastic strain, where n represents the strain hardening exponent, and C represents the strain rate sensitivity coefficient. Indicates the actual strain rate. The value represents the reference strain rate, m represents the thermal softening index, and T represents the actual temperature of the workpiece's cutting surface. Indicates the melting point of the workpiece material. This indicates room temperature.

[0015] Furthermore, the image analysis model is calibrated, including at least one of the following: Replace or correct the calibration method in the calibration unit; Replace or correct the image analysis algorithm in the image analysis unit; Replace or correct the material constitutive model.

[0016] Furthermore, the image analysis algorithm includes digital image correlation and particle image velocimetry.

[0017] Furthermore, the shear force F of the first shear band is calculated based on the equivalent stress field. s1 ,include: ;

[0018] Where b represents the cutting width and h represents the cutting thickness. Indicates equivalent stress. The shear angle refers to the angle between the direction of the cutting speed and the direction of chip shearing. Based on dynamic mechanical data, the shear force F of the first shear band is obtained. s1 The second shear force F at the corresponding moment s2 ,include: ; in, This represents the main cutting force, which is the force along the X-axis detected by the matrix decoupled force sensor. This represents the force detected by the matrix decoupled force sensor in the Z-axis direction. The shear angle refers to the angle between the direction of the cutting speed and the direction of chip shearing.

[0019] Furthermore, the processing platform includes a workpiece fixture and a nano-movement component. The nano-movement component includes an X-axis movement module, a Y-axis movement module, and a Z-axis movement module. The workpiece fixture is fixed in the X-axis movement module, the X-axis movement module is fixed in the Y-axis movement module, and the Y-axis movement module is fixed in the Z-axis movement module. When the machining tool gradually cuts the workpiece, the nano-moving component is set with several moving steps. After the nano-moving component moves one step each time, the machining tool stops cutting. The scanning electron microscope switches to slow scanning imaging mode to acquire microscopic morphology images of the cutting area.

[0020] Furthermore, the rake angle of the machining tool is 10°, the clearance angle of the machining tool is 2.5°, and the blunt radius of the cutting edge of the machining tool is 150nm.

[0021] Furthermore, the strain field, strain rate field, and equivalent stress field are used to analyze the cutting mechanism at the micrometer and nanometer levels.

[0022] The technical solutions provided in this application have the following advantages compared with the prior art: This application employs a matrix-decoupled force sensor to acquire dynamic mechanical data of the entire cutting process in real time. This dynamic mechanical data reflects the actual force on the tool during the cutting process. Simultaneously, after each cut, a microscopic morphological image of the cutting area is acquired, forming a time-series image sequence of the entire cutting process according to the cutting time. Based on the microscopic morphological images, the strain field, strain rate field, and equivalent stress field are obtained through an image analysis model. The shear force F of the first shear band is calculated based on the equivalent stress field. s1Simultaneously, the dynamic mechanical data acquired by the matrix decoupled force sensor can also yield the corresponding second shear band shear force F. s2 The first shear band shear force F s1 Second shear band shear force F s2 Cross-validation is performed. If the error between the two methods is less than or equal to a preset value, it indicates that the strain field, strain rate field, and equivalent stress field obtained through the image analysis model are accurate and can be directly output as the theoretical basis for subsequent analysis. If the error is greater than the preset value, it indicates that the strain field, strain rate field, and equivalent stress field obtained by the image analysis model are not accurate enough and need to be corrected before re-analysis. This process continues until the shear force of the first shear band obtained from the image is determined. Fs1 The second shear band shear force under actual stress Fs2 The error is controlled within the preset value. In this application, the matrix decoupled force sensor can achieve high-precision measurement of deformation across the entire field, and the image analysis model can simultaneously acquire the strain field, strain rate field, and equivalent stress field during the cutting process. This realizes a true reflection of the cutting deformation field based on physical deformation images, providing a real, direct, and reliable experimental means for optimizing micro-nano fabrication processes and evaluating the mechanical properties of materials. Through cross-validation of the two, the simultaneous acquisition of SEM morphology, cutting force, and deformation field data is achieved, establishing a direct correlation between "microstructure and mechanical response." This provides a reliable experimental basis for revealing the cutting mechanism under scale effects, effectively compensating for the problem of existing simulation methods being disconnected from actual machining conditions. Furthermore, it provides accurate experimental support for tool design optimization, cutting parameter control, and the development of advanced manufacturing processes. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] In the attached image: Figure 1 This is a schematic diagram of the structure of the nanomobile component in the embodiments of this application; Figure 2 This is a flowchart illustrating the analysis method in an embodiment of this application; Figure 3 The microscopic morphology images output at different times in the embodiments of this application, along with their corresponding DIC and PIV analysis results; Figure 4This is a schematic diagram of the stress field, strain rate field, and stress field at different times in the final output of the embodiments of this application; Figure 5 This is a flowchart illustrating the cutting and analysis methods in the embodiments of this application.

[0026] Reference numerals: 1. Matrix decoupled force sensor; 2. Tool fixture; 3. First nut; 4. Second nut; 5. Machining tool; 6. Workpiece to be machined; 7. Third nut; 8. Workpiece fixture; 91. X-axis slider; 92. X-axis linear guide; 93. X-axis guide base; 94. Y-axis slider; 95. Y-axis linear guide; 96. Y-axis guide base; 97. Z-axis linear guide; 98. Z-axis slider; 99. Z-axis guide base; 14. Frame; 15. Y-axis movement module; 16. X-axis movement module; 17. Z-axis movement module. Detailed Implementation

[0027] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the orientations or positional relationships indicated by terms such as "front," "rear," "upper," "lower," "left," "right," "longitudinal," "horizontal," "vertical," "horizontal," "top," "bottom," "inner," "outer," "head," and "tail" are based on the orientations or positional relationships shown in the accompanying drawings, and are constructed and operated in a specific orientation. They are only for the convenience of describing this technical solution and do not indicate that the referred mechanism or element must have a specific orientation; therefore, they should not be construed as limitations on this invention.

[0028] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. When an component is referred to as being "on" or "below" another component, the component can be located "directly" or "indirectly" on the other component, or there may be one or more intermediary components. The terms "first," "second," "third," etc., are only for the convenience of describing this technical solution and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0029] In the following description, specific details such as particular system structures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, mechanisms, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0030] Example 1 This application provides a method for in-situ cutting observation and full-field deformation measurement at the micro-nano scale, including: S1: Adjust the relative positions of the scanning electron microscope and the in-situ machining device so that the machining platform in the in-situ machining device is within the observation line of the scanning electron microscope; the in-situ machining device includes a machining tool, a machining platform for clamping the workpiece, and a matrix decoupled force sensor for monitoring the force on the machining tool; S2: The workpiece is cut step by step using a machining tool. After each cut, the scanning electron microscope acquires the microscopic morphology image of the workpiece cutting area to form a time sequence of images of the entire cutting process. The matrix decoupled force sensor acquires the dynamic mechanical data of the entire cutting process in real time.

[0031] The machining platform includes a workpiece fixture and a nano-motion component. The nano-motion component comprises an X-axis movement module, a Y-axis movement module, and a Z-axis movement module. The workpiece fixture is fixed within the X-axis movement module, the X-axis movement module is fixed within the Y-axis movement module, and the Y-axis movement module is fixed within the Z-axis movement module. When the machining tool progressively cuts the workpiece, the nano-motion component is configured with several movement steps. After each step, the machining tool stops cutting. The scanning electron microscope switches to slow-scan imaging mode to acquire microscopic morphological images of the cutting area.

[0032] The rake angle of the machining tool is 10°, the clearance angle of the machining tool is 2.5°, and the blunt radius of the cutting edge of the machining tool is 150nm.

[0033] S3: Based on the microscopic morphology image, obtain the strain field, strain rate field, and equivalent stress field through image analysis model; obtain the shear force F of the first shear zone based on dynamic mechanical data. s1 The second shear force F at the corresponding moment s2 The image analysis model includes a correction unit, an image analysis unit, and a material constitutive model; the image analysis unit includes an image analysis algorithm. The strain field, strain rate field, and equivalent stress field are obtained through image analysis models; including: S1: The micro-morphology image is electronically drift-corrected by the correction unit to eliminate imaging deviation and form a corrected micro-morphology image; S2: The image analysis algorithm is used to analyze and calculate the corrected micro-morphology image to obtain the first velocity field, strain field, strain field component, strain rate field, and strain rate component. S3: Based on the strain field, strain field components, strain rate field, and strain rate components, calculate the equivalent stress field using the material constitutive model. Specifically, the image analysis model includes a correction unit, an image analysis unit, and a material constitutive model; the image analysis unit includes an image analysis algorithm. The strain field, strain rate field, and equivalent stress field are obtained through image analysis models; including: S31: The microscopic morphology image is electronically drift corrected by the correction unit to eliminate imaging deviation and form a corrected microscopic morphology image; S32: The corrected microscopic topography image is analyzed and calculated using an image analysis algorithm to obtain a first velocity field, strain field, strain field components, strain rate field, and strain rate components. The image analysis unit includes at least one image analysis algorithm, such as Digital Image Correlation (DIC) and Particle Image Velocimetry (PIV). The core principle of DIC is to track the displacement of image subsets through grayscale matching. This involves dividing the image before deformation into subsets and matching the corresponding subsets in the image after deformation using the ZNCC zero-normalized cross-correlation algorithm, thus converting it into a deformation field. PIV uses image speckle as tracer particles. Its core principle is to calculate particle displacement through cross-correlation, dividing consecutive frame images into query windows and converting them into a velocity field based on time intervals.

[0034] Cross-validation is performed on the first velocity field and the second velocity field to select image analysis algorithms with errors less than or equal to a preset value. Based on the selected image analysis algorithms, the first velocity field, strain field, strain field components, strain rate field, and strain rate components are obtained. The second velocity field is the cutting speed value set by the in-situ machining device.

[0035] S33: Calculate the equivalent stress field based on the strain field, strain field components, strain rate field, and strain rate components, using the material constitutive model.

[0036] This application utilizes the Vic-2D post-processing function to extract the equivalent strain field, strain field components (normal strain, shear strain, etc.), equivalent strain rate field, and strain rate field from DIC data. Finally, based on the material constitutive model and the aforementioned deformation parameters, the stress field during the cutting process is calculated, ultimately yielding the velocity field, strain field, strain rate field, and equivalent stress field. In calculating the equivalent stress field, since the temperature change is extremely small and close to room temperature, the effect of temperature is ignored. The calculation method for the equivalent stress field includes: ; ; ; in, A represents the equivalent stress field; B represents the yield stress under the reference condition; and C represents the strain hardening modulus. The expression represents the equivalent plastic strain, where n represents the strain hardening exponent, and C represents the strain rate sensitivity coefficient. Indicates the actual strain rate. The value represents the reference strain rate, m represents the thermal softening index, and T represents the actual temperature of the workpiece's cutting surface. Indicates the melting point of the workpiece material. This indicates room temperature.

[0037] Calculate the shear force F of the first shear band based on the equivalent stress field. s1 ,include: ;

[0038] Where b represents the cutting width and h represents the cutting thickness. Indicates equivalent stress. The shear angle refers to the angle between the direction of the cutting speed and the direction of chip shearing.

[0039] Based on dynamic mechanical data, the shear force F of the first shear band is obtained. s1 The second shear force F at the corresponding moment s2 ,include: ; in, This represents the main cutting force, which is the force along the X-axis detected by the matrix decoupled force sensor. This represents the force detected by the matrix decoupled force sensor in the Z-axis direction. The shear angle refers to the angle between the direction of the cutting speed and the direction of chip shearing.

[0040] S4: Apply the shear force F of the first shear band s1 Second shear band shear force F s2Cross-validation is performed. If the error between the two is less than or equal to a preset value, the strain field, strain rate field, and equivalent stress field after each cut are output. If the error is greater than the preset value, the image analysis model is corrected to re-obtain the strain field, strain rate field, and equivalent stress field. The correction of the image analysis model includes at least one of the following: Replace or correct the calibration method in the calibration unit; Replace or correct the image analysis algorithm in the image analysis unit; Replace or correct the material constitutive model.

[0041] This application employs a matrix-decoupled force sensor to acquire dynamic mechanical data of the entire cutting process in real time. This dynamic mechanical data reflects the actual force on the tool during the cutting process. Simultaneously, after each cut, a microscopic morphological image of the cutting area is acquired, forming a time-series image sequence of the entire cutting process according to the cutting time. Based on the microscopic morphological images, the strain field, strain rate field, and equivalent stress field are obtained through an image analysis model. The shear force F of the first shear band is calculated based on the equivalent stress field. s1 Simultaneously, the dynamic mechanical data acquired by the matrix decoupled force sensor can also yield the corresponding second shear band shear force F. s2 The first shear band shear force F s1 Second shear band shear force F s2 Cross-validation is performed. If the error between the two methods is less than or equal to a preset value, it indicates that the strain field, strain rate field, and equivalent stress field obtained through the image analysis model are accurate and can be directly output as the theoretical basis for subsequent analysis. If the error is greater than the preset value, it indicates that the strain field, strain rate field, and equivalent stress field obtained by the image analysis model are not accurate enough and need to be corrected before re-analysis. This process continues until the shear force of the first shear band obtained from the image is determined. Fs1 The second shear band shear force F under actual stress s2 The error is controlled within the preset value. In this application, the matrix decoupled force sensor can achieve high-precision measurement of deformation across the entire field, and the image analysis model can simultaneously acquire the strain field, strain rate field, and equivalent stress field during the cutting process. This realizes a true reflection of the cutting deformation field based on physical deformation images, providing a real, direct, and reliable experimental means for optimizing micro-nano fabrication processes and evaluating the mechanical properties of materials. Through cross-validation of the two, the simultaneous acquisition of SEM morphology, cutting force, and deformation field data is achieved, establishing a direct correlation between "microstructure and mechanical response." This provides a reliable experimental basis for revealing the cutting mechanism under scale effects, effectively compensating for the problem of existing simulation methods being disconnected from actual machining conditions. Furthermore, it provides accurate experimental support for tool design optimization, cutting parameter control, and the development of advanced manufacturing processes.

[0042] Example 2 This application provides a method for in-situ cutting observation and full-field deformation measurement at the micro-nano scale. It employs an in-situ machining device integrated within a scanning electron microscope (SEM) to observe the workpiece and its full-field deformation. This embodiment uses a Hitachi SU5000 field emission scanning electron microscope (SEM) with a cold field emission electron gun, supporting high vacuum (≤1×10⁻⁴ Pa) and low vacuum (1-270 Pa) modes, with a maximum magnification of 180k. It is equipped with an SE detector, a BSE detector, and an EDS spectrometer.

[0043] The electron microscope's operating parameters cover accelerating voltage from 0.5 to 30 kV, beam current from 1 pA to 200 nA, and stage Z-axis travel from 0 to 55 mm. It is rigidly connected to in-situ cutting equipment via a dedicated interface for data communication, exhibiting high stability and a wide parameter range to meet the needs of in-situ cutting experiments at the micro-nano scale.

[0044] To obtain high signal-to-noise ratio and high-resolution images that meet the requirements of full-field deformation measurements using Digital Image Correlation (DIC) and Particle Image Velocimetry (PIV), this study systematically investigated the influence of accelerating voltage, beam intensity, and working distance on image quality using a single-factor variable method on the Hitachi SU5000 scanning electron microscope. Experimental results show that when the accelerating voltage is between 3 and 7 kV, the beam intensity is between 25 and 35 kV, and the working distance is controlled within the range of 14–16 mm, the electron microscope imaging can meet the requirements of DIC measurements for speckle feature recognition and image texture clarity. Through a comprehensive evaluation of imaging resolution, speckle contrast, and signal stability, the optimal imaging parameter combination for the SU5000 electron microscope was determined to be: accelerating voltage 5 kV, beam intensity 30 kV, and working distance 14.5 mm. Under these parameter conditions, observation images with both high resolution and high contrast can be obtained.

[0045] The in-situ machining device used in this embodiment includes a machining tool, a machining platform for clamping the workpiece, and a matrix decoupled force sensor for monitoring the force on the machining tool. The machining platform includes a workpiece fixture and a nano-motion component. The nano-motion component includes an X-axis motion module, a Y-axis motion module, and a Z-axis motion module. The workpiece fixture is fixed in the X-axis motion module, the X-axis motion module is fixed in the Y-axis motion module, and the Y-axis motion module is fixed in the Z-axis motion module.

[0046] Specifically, such as Figure 1As shown, the matrix decoupled force sensor 1 is fixed in the frame 14, and the tool holder 2 is fixed above the matrix decoupled force sensor 1 by the first nut 3, and the axes of the two are coaxial; the machining tool 5 is fixed in the side of the tool holder 2 by the second nut 4; a nano-movement component is provided on the other side directly opposite the machining tool 5, the nano-movement component includes an X-axis moving module 16, a Y-axis moving module 15 and a Z-axis moving module 17; the Z-axis moving module 17 includes: two Z-axis linear guides 97, a Z-axis slider 98 and a Z-axis guide base 99; the Y-axis moving module 15 includes: a Y-axis linear guide 95, a Y-axis slider 94 and a Y-axis guide base 96; the X-axis moving module 16 includes: an X-axis linear guide 92, an X-axis slider 91 and an X-axis guide base 93. The Z-axis guide rail base 99 is fixed in the frame 14. Two Z-axis linear guides 97 are set at a certain angle. The Z-axis slider 98 is embedded between the two Z-axis linear guides 97, and both ends of the Z-axis slider 98 can slide along the two Z-axis linear guides 97 respectively. The rear end of the Y-axis guide rail base 96 is fixed in the Z-axis slider 98. The front end of the Y-axis guide rail base 96 is provided with a Y-axis linear guide 95, and the Y-axis slider 94 is slidably disposed in the Y-axis linear guide 95. The rear end of the X-axis guide rail base 93 is fixed in the Y-axis slider 94. The front end of the X-axis guide rail base 93 is provided with an X-axis linear guide 92, and the X-axis slider 91 is slidably disposed in the X-axis linear guide 92. The X-axis linear guide 92 and the Y-axis linear guide 95 extend perpendicularly, and one of the Z-axis linear guides 97 is perpendicular to both the X-axis linear guide 92 and the Y-axis linear guide 95. The workpiece fixture 8 is fixed in the X-axis slider 91, and the workpiece 6 to be processed is fixed in the workpiece fixture 8 by the third nut 7. The nano-movement component can drive the workpiece to be processed to move towards or away from the processing tool 5.

[0047] The nano-motion component is driven by PZT piezoelectric ceramic. Under the influence of an external electric field, the internal lattice structure of the piezoelectric ceramic material undergoes polarization rearrangement, producing minute mechanical deformations aligned with the electric field direction. Changes in the voltage signal are directly converted into expansion and contraction deformations of the ceramic element, thereby driving linear motion in the X-axis motion module 16, Y-axis motion module 15, and Z-axis motion module 17. The device parameters of the nano-motion component and the matrix decoupled force sensor 1 are as follows: X / Y Axis: The X-axis and Y-axis motion modules use the same model, with dimensions of 30mm×30mm×9.5mm, an operating voltage range of 0-60V, and the following motion parameters: stroke ±20mm, minimum step size 50nm, maximum drive speed 4.5mm / s, maximum load 90N, and absolute motion accuracy <0.01% of the stroke; Z-axis: Z-axis moving module dimensions 31mm×30mm×31.5mm, operating voltage 0-60V, stroke ±5mm, maximum drive speed 2mm / s, maximum load 8N, motion repeatability <50nm, absolute motion accuracy <0.01% of stroke, minimum vacuum degree for operation in vacuum is 10-4mbar, and operating ambient temperature is 273K-328K.

[0048] The matrix decoupling force sensor has six signal channels, capable of simultaneously measuring force and torque along the X, Y, and Z axes. The X and Y axis force measurement range is 0-50N, the Z axis force measurement range is 0-100N, and the X, Y, and Z torque measurement range is 0-0.5N·m. It features linearity ≤1%FS, an operating temperature range of 233K-373K, and a signal sampling frequency range of 10-2000Hz. The force measurement principle is as follows: It employs a multi-dimensional force-sensitive element array layout, using built-in high-precision strain gauges to sense the micro-strain generated by the tool under load during cutting. The force signal is converted into an electrical signal, and a matrix decoupling algorithm is used to eliminate signal cross-interference between forces in different directions (such as cutting force and feed force), achieving precise separation and independent measurement of force components in each dimension, ultimately outputting high-precision dynamic mechanical data.

[0049] The frame is made of titanium alloy, and the matrix decoupled force sensor and nano-motion component are fixed to the two ends of the frame with titanium alloy screws; and the machining tool is directly opposite the fixture. This embodiment uses a single-crystal copper workpiece as an example. The single-crystal copper material used in the experiment was purchased from Hefei Single Crystal Materials Technology Co., Ltd., with an initial specification of 10mm×5mm×0.5mm. To meet the sample thickness requirements of the in-situ cutting experiment, the workpiece needs to be thinned and surface-finished: First, gradient-grit diamond sandpaper (1000#→3000#→5000#→7000#) is used for wet polishing in sequence to reduce the sample thickness from 500μm to 150μm; then, short-pile polishing cloth is used with 0.02μm silica polishing liquid for chemical mechanical polishing to remove scratches and processing-induced deterioration layers remaining from sandpaper polishing; finally, argon ion polishing is used for 1 hour to further eliminate surface micro-defects and obtain a smooth workpiece with extremely low surface roughness. After surface treatment, a high-contrast, uniformly distributed speckle pattern is prepared on the workpiece observation surface according to the method disclosed in CN201910692609, providing feature markers for subsequent full-field deformation measurement using digital image correlation (DIC).

[0050] The machining tools used in the experiment were made of cemented carbide, model F10, with a rake angle of 10° and a clearance angle of 2.5°. Tool preparation consisted of two stages: roughing and finishing. First, the cemented carbide blank was machined to the pre-designed tool shape. Then, a precision finishing machine (model: EM TXP) was used for edge finishing. This machine integrates a high-magnification microscope, offering high positioning accuracy and a minimum feed step of 0.5 μm. The finishing process flow is as follows: Clamping and tool setting: The rough-machined tool blank is clamped in the equipment fixture, and the tool posture is adjusted by observation under a microscope to ensure that the tool face to be polished is strictly parallel to the surface of the 0.5μm U-shaped diamond polishing sheet; Step-by-step polishing: First, polish the side of the machining tool by setting a single feed step of 0.5μm and continuing to polish until the surface has a mirror effect; quickly rinse the polished surface with anhydrous ethanol, gently wipe it with a lint-free cotton ball, and then place it in an ultrasonic cleaner for 15 minutes to thoroughly remove polishing residue; follow the same process and parameters to complete the fine polishing of the rake face and flank face of the machining tool in sequence; Quality inspection: The cemented carbide cutting tools prepared by the above process, when observed with a scanning electron microscope, have a minimum cutting edge radius of 150 nm, which meets the accuracy requirements of in-situ cutting experiments at the micro-nano scale.

[0051] After the above pretreatment of the cutting tool and the workpiece, the relative positions of the scanning electron microscope and the in-situ machining device are adjusted so that the machining platform in the in-situ machining device is within the observation line of the scanning electron microscope. First, both are positioned and calibrated: The machining tool is mounted on a tool holder, and the workpiece is clamped on a workpiece holder. Before entering the SEM chamber, the distance between the machining tool and the workpiece is adjusted to L≤2mm under visual conditions. After entering the SEM chamber, the secondary electron (SE) low-magnification dynamic scanning mode of the SU5000 scanning electron microscope is used to identify the target area for machining. The machining tool and workpiece are precisely moved to the designated machining position. According to the process parameters, the parameters of the nano-motion component and the capture frequency of the matrix decoupled force sensor are adjusted. In order to better capture the second deformation zone of the cutting process, the height difference between the tool and the workpiece needs to be minimized as much as possible. In the secondary electron mode, the workpiece will leave a shadow on the cutting edge of the tool. The range of the height difference between the workpiece and the tool is judged by the shadow, and the height difference is further controlled to reduce it so that the second deformation zone can be clearly observed.

[0052] Preliminary experiments were conducted, with the nano-mobile platform voltage set to 45V and 300Hz. The machining process and the force measurement of the matrix-decoupled force sensor were observed. The voltage and frequency were gradually reduced until the cutting morphology could be clearly observed and the mechanical signal could be stably measured. High contrast between the image speckle and the matrix was particularly important to meet the requirements of image analysis technology. Based on this, a frame-by-frame intermittent slow-scan imaging method was used to acquire cutting images. That is, after the cutting system performed a single feed action, it paused, and the electron microscope switched to slow-scan imaging mode to acquire microscopic morphology images of the cutting area. This "cutting-stopping-imaging" cycle was repeated to form a time-series image sequence of the entire cutting process. Simultaneously, dynamic mechanical data of each cutting stage were acquired synchronously through the matrix-decoupled force sensor. Figure 5 The diagram shown is a flowchart illustrating the cutting and analysis process of this application.

[0053] Based on the microscopic morphology image, the strain field, strain rate field, and equivalent stress field are obtained through an image analysis model. The image analysis model includes a correction unit, an image analysis unit, and a material constitutive model. The image analysis unit includes an image analysis algorithm. Specifically, it includes: like Figure 2 As shown, for the sequence of images acquired during in-situ SEM processing, the OpenCV computer vision library is first used to perform electronic drift correction based on feature region matching, eliminating imaging bias to ensure spatial consistency in subsequent analysis. After correction, image analysis algorithms are used for analysis and calculation. This embodiment uses two image analysis techniques: Digital Image Correlation (DIC) and Particle Image Velocimetry (PIV). The core principle of DIC is to track the displacement of image subsets through grayscale matching. That is, the image before deformation is divided into subsets, and the corresponding subsets are matched in the image after deformation using the ZNCC zero-normalized cross-correlation algorithm, which is then converted into a deformation field. This embodiment uses Vic-2D software for analysis, determining the subset size based on the speckle noise level before analysis. PIV uses image speckle as tracer particles. The core is to calculate particle displacement through cross-correlation, that is, to divide continuous frame images into query windows and convert them into a velocity field by combining time intervals. The study used the MATLAB-PIVlab toolbox to perform the analysis. The query window size was determined based on speckle noise, and the cross-correlation operation was performed using the FFT (Fast Fourier Transform) algorithm.

[0054] After DIC and PIV analysis, the obtained first and second velocity fields are cross-validated. Data comparison is used to control the relative error within 10%, ensuring the reliability of the results. The velocity field obtained after DIC and PIV analysis is the first velocity field, and the cutting speed set by the in-situ machining device is the second velocity field. If the cross-validation error between the first and second velocity fields after DIC and PIV analysis is less than or equal to 10%, the Vic-2D post-processing function is used to extract the equivalent strain field, strain field components (normal strain, shear strain, etc.), equivalent strain rate field, and strain rate field from the DIC data. Finally, based on the material constitutive model and the above deformation parameters, the equivalent stress field of the cutting process is calculated, ultimately obtaining the velocity field, strain field, strain rate field, and equivalent stress field. Figure 3 As shown, this embodiment outputs microscopic morphology images at different times, along with their corresponding DIC and PIV analysis results.

[0055] Material constitutive models include, but are not limited to, the Johnson-Cook constitutive model. After verification, the average relative error of the first and second velocity fields obtained by cross-validation using DIC and PIV in this application is 6.51%, compared to a preset value of 10%.

[0056] In calculating the equivalent stress field, since the temperature change is extremely small and close to room temperature, the effect of temperature is ignored. The formula for calculating the equivalent stress field is as follows: ; ; ; in, Represents the equivalent force field; is the target value for the image analysis model.

[0057] A represents the yield stress under reference conditions, and represents the initial yield strength of the workpiece material at the reference strain rate and reference temperature.

[0058] B represents the strain hardening modulus, which, together with the parameter n, determines the degree of strain hardening of the material.

[0059] It represents the equivalent plastic strain, a measure of irreversible deformation of a material.

[0060] n represents the strain hardening index, which determines the shape of the hardening curve.

[0061] C represents the strain rate sensitivity coefficient, which characterizes the strengthening effect of a material on strain rate.

[0062] This represents the dimensionless strain rate.

[0063] This represents the actual strain rate.

[0064] This represents the reference strain rate.

[0065] m represents the thermal softening index, which characterizes the degree to which a material softens as temperature increases.

[0066] This represents dimensionless temperature.

[0067] T represents the actual temperature of the workpiece's cutting surface. Indicates the melting point of the workpiece material. This indicates room temperature.

[0068] Calculate the shear force F of the first shear band based on the equivalent stress field. s1 ,include: ;

[0069] Where b represents the cutting width and h represents the cutting thickness. Indicates equivalent stress. The shear angle refers to the angle between the direction of the cutting speed and the direction of chip shearing.

[0070] Based on dynamic mechanical data, the shear force F of the first shear band is obtained. s1 The second shear force F at the corresponding moment s2 ,include: ; in, This represents the main cutting force, which is the force along the X-axis detected by the matrix decoupled force sensor. This represents the force detected by the matrix decoupled force sensor in the Z-axis direction. The shear angle refers to the angle between the cutting speed direction and the chip shear direction. In this embodiment, the first shear band shear force F obtained through cross-validation of DIC and PIV has been verified. s1 Second shear band shear force F s2 The average relative error is 9.86%; the preset value is 10%. This indicates that the image analysis model in this application, which includes a correction unit, an image analysis unit, and a material constitutive model, can accurately preset the strain field, strain rate field, and stress field on the cutting surface. Figure 4 The diagram shows the stress field, strain rate field, and stress field at different times in the final output of the method of this application.

[0071] This application utilizes SEM to acquire a sequence of images of the cutting process in real time; it employs digital image correlation (DIC) and particle image velocimetry (PIV) techniques to process the sequence of images, obtaining the full-field displacement and strain distribution on the workpiece surface; combining the measurement results of DIC and PIV, it achieves quantitative characterization of the full-field deformation behavior of the workpiece during micro- and nano-cutting. This application can realize in-situ micro- and nano-cutting within SEM, and simultaneously link SEM imaging with DIC and PIV algorithms to acquire morphological changes and full-field deformation data (velocity field, strain rate field, strain field, and stress field) during the cutting process, for analysis of micro- and nano-cutting mechanisms.

[0072] This application is equipped with a nanometer-scale moving component (minimum step size 50nm) and a matrix-decoupled force sensor (sub-micro Newton resolution), enabling direct force measurement with micro-nano level precision. This eliminates cross-interference of force signals, significantly improving measurement accuracy. It has been successfully used to acquire high-precision cutting force data in experiments with materials such as single-crystal copper and vermicular graphite cast iron. The cutting process is stable, meeting the requirements of DIC for plane strain. Combined with speckle optimization technology, it achieves unified qualitative observation and quantitative deformation analysis of the cutting process, overcoming the bottleneck of existing equipment's inability to perform quantitative measurements. This application is compatible with various materials, including metals and semiconductors, and has broad adaptability to different working conditions. The integrated function of this application simultaneously acquires SEM morphology, cutting force, and DIC deformation field data, establishing a direct correlation between "microstructure and mechanical response," providing accurate experimental support for the calibration of the crystal plastic finite element model (CPFEM) and tool optimization.

[0073] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for in-situ cutting observation and full-field deformation measurement at the micro / nano scale, characterized in that, include: The relative positions of the scanning electron microscope and the in-situ machining device are adjusted so that the machining platform in the in-situ machining device is within the observation line of the scanning electron microscope; the in-situ machining device includes a machining tool, a machining platform for clamping the workpiece, and a matrix decoupled force sensor for monitoring the force on the machining tool; The workpiece is cut step by step using a machining tool. After each cut, the scanning electron microscope acquires a microscopic morphology image of the workpiece's cutting area, thereby forming a time-series image sequence of the entire cutting process. The matrix decoupled force sensor acquires dynamic mechanical data of the entire cutting process in real time. Based on the microscopic morphology image, the strain field, strain rate field, and equivalent stress field are obtained through an image analysis model. The shear force F of the first shear band is then calculated based on the equivalent stress field. s1 Based on dynamic mechanical data, the shear force F of the first shear band is obtained. s1 The second shear force F at the corresponding moment s2 ; The shear force F of the first shear band s1 Second shear band shear force F s2 Cross-validation is performed. If the error between the two is less than or equal to the preset value, the strain field, strain rate field, and equivalent stress field after each cut are output. If the error between the two is greater than the preset value, the image analysis model is corrected to obtain the strain field, strain rate field, and equivalent stress field again.

2. The method for in-situ cutting observation and full-field deformation measurement at the micro / nano scale according to claim 1, characterized in that, The image analysis model includes a correction unit, an image analysis unit, and a material constitutive model; the image analysis unit includes an image analysis algorithm. The strain field, strain rate field, and equivalent stress field are obtained through image analysis models; including: S1: The micro-morphology image is electronically drift-corrected by the correction unit to eliminate imaging deviation and form a corrected micro-morphology image; S2: The image analysis algorithm is used to analyze and calculate the corrected micro-morphology image to obtain the first velocity field, strain field, strain field component, strain rate field, and strain rate component. S3: Calculate the equivalent stress field based on the strain field, strain field components, strain rate field, and strain rate components, using the material constitutive model.

3. The method for in-situ cutting observation and full-field deformation measurement at the micro / nano scale according to claim 2, characterized in that, The image analysis unit includes at least one image analysis algorithm, and step S2 further includes: Cross-validation is performed on the first velocity field and the second velocity field to select image analysis algorithms with errors less than or equal to a preset value. Based on the selected image analysis algorithms, the first velocity field, strain field, strain field components, strain rate field, and strain rate components are obtained. The second velocity field is the cutting speed value set by the in-situ machining device.

4. The method for in-situ cutting observation and full-field deformation measurement at the micro / nano scale according to claim 2, characterized in that, The calculation method for the equivalent stress field described in step S3 includes: ； ； ； in, A represents the equivalent stress field; B represents the yield stress under the reference condition; and C represents the strain hardening modulus. The expression represents the equivalent plastic strain, where n represents the strain hardening exponent, and C represents the strain rate sensitivity coefficient. This represents the dimensionless strain rate. Indicates the actual strain rate. The value represents the reference strain rate, m represents the thermal softening index, and T represents the actual temperature of the workpiece's cutting surface. Represents dimensionless temperature. Indicates the melting point of the workpiece material. This indicates room temperature.

5. The method for in-situ cutting observation and full-field deformation measurement at the micro / nano scale according to claim 2, characterized in that, The image analysis model is calibrated, including at least one of the following: Replace or correct the calibration method in the calibration unit; Replace or correct the image analysis algorithm in the image analysis unit; Replace or correct the material constitutive model.

6. The method for in-situ cutting observation and full-field deformation measurement at the micro / nano scale according to claim 2, characterized in that, The image analysis algorithms include digital image correlation and particle image velocimetry.

7. The method for in-situ cutting observation and full-field deformation measurement at the micro / nano scale according to claim 1, characterized in that, Calculate the shear force F of the first shear band based on the equivalent stress field. s1 ,include: ； Where b represents the cutting width and h represents the cutting thickness. Indicates equivalent stress. The shear angle refers to the angle between the direction of the cutting speed and the direction of chip shearing. Based on dynamic mechanical data, the shear force F of the first shear band is obtained. s1 The second shear force F at the corresponding moment s2 ,include: ； in, This represents the main cutting force, which is the force along the X-axis detected by the matrix decoupled force sensor. This represents the force detected by the matrix decoupled force sensor in the Z-axis direction. The shear angle refers to the angle between the direction of the cutting speed and the direction of chip shearing.

8. The method for in-situ cutting observation and full-field deformation measurement at the micro / nano scale according to claim 1, characterized in that, The processing platform includes a workpiece fixture and a nano-movement component. The nano-movement component includes an X-axis movement module, a Y-axis movement module, and a Z-axis movement module. The workpiece fixture is fixed in the X-axis movement module, the X-axis movement module is fixed in the Y-axis movement module, and the Y-axis movement module is fixed in the Z-axis movement module. When the machining tool gradually cuts the workpiece, the nano-moving component is set with several moving steps. After the nano-moving component moves one step each time, the machining tool stops cutting. The scanning electron microscope switches to slow scanning imaging mode to acquire microscopic morphology images of the cutting area.

9. A method for in-situ cutting observation and full-field deformation measurement at the micro / nano scale according to claim 8, characterized in that, The rake angle of the machining tool is 10°, the clearance angle of the machining tool is 2.5°, and the blunt radius of the cutting edge of the machining tool is 150nm.

10. The method for in-situ cutting observation and full-field deformation measurement at the micro / nano scale according to claim 1, characterized in that, The strain field, strain rate field, and equivalent force field are used to analyze the cutting mechanism at the micrometer and nanometer levels.

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