A device and method for testing the cutting strain of laminated materials based on DIC technology

Abstract

The present application relates to the field of material cutting performance testing, and provides a laminated material cutting strain testing device and method based on DIC technology, which adopts a high-speed linear motor to drive the main movement of a cutting tool, can realize the equivalent conversion of complex three-dimensional cutting into two-dimensional plane cutting, sets parameters such as cutting depth in cooperation with a micro-motion platform, and realizes dynamic control of the cutting depth by using a piezoelectric ceramic driver. Meanwhile, a non-contact digital image correlation method is used for strain data collection and analysis, the linear adjustment of the frame rate of a high-speed camera is matched with the relative position of the laminated material, the synchronous triggering of the software and hardware is realized, the speckle image of the expected position is shot, and the strain information at the different material interfaces of the laminated material is calculated to study the strain law caused by the cutting of the cutting tool to different layers of the laminated material and different cutting angles. The present application has important significance for improving the processing quality of laminated materials.

Description

Technical Field

[0001] This invention belongs to the field of material machining performance testing, and relates to the cutting strain testing of material layers and interlayer interfaces of laminated composite materials. Specifically, it relates to a device and method for testing the cutting strain of laminated materials based on DIC technology. Background Technology

[0002] With the rapid development of modern manufacturing, unprecedented performance requirements have been placed on the materials and processing properties of parts. Laminated materials, formed by stacking materials such as titanium alloys, aluminum alloys, magnesium alloys, and high-entropy alloys, possess characteristics such as low density, high strength, high wear resistance, high temperature resistance, and corrosion resistance. However, during the processing of laminated alloy components, the performance differences between different material layers often lead to problems such as large tool wear and difficulty in controlling the surface roughness of the machined surface, which seriously restricts and limits the application and expansion of such laminated materials.

[0003] Typical laminated materials include metallic alloys such as titanium alloys, aluminum alloys, magnesium alloys, and high-entropy alloys, as well as composite materials such as carbon fibers. Different material layers have different metallic properties, resulting in significant differences in machinability. The matching of machining parameters with material cutting quality also varies considerably. Furthermore, the influence of interfaces between multiple material layers and machining defects at these interfaces severely impact the machinability and quality of such laminated materials. The cutting process, involving the interaction between the tool and the workpiece to form chips, involves a series of physical phenomena including cutting forces, heat, stress, and strain. Therefore, it is necessary to analyze the strain behavior of the base material, material interfaces, and material components of the laminated material, starting from the perspective of its layered cutting performance.

[0004] In the current field of machining, fundamental material tests can reveal macroscopic and microscopic properties such as mechanical properties and microscopic interfaces, enabling modeling and simulation of the machining process using constitutive models and finite element analysis. Existing material strain analysis and testing methods, including specialized testing techniques such as strain gauges and fiber optic gratings, characterize the material's strength, hardness, interface properties, and internal microstructure and stress distribution, allowing for material performance testing based on experimental samples. However, considering the machinability of the layers and interfaces in this laminated material, it remains impossible to differentiate the material properties of different layers and interfaces.

[0005] The strain gauge electrical method is an experimental stress analysis method that uses resistance strain gauges to measure the surface strain of a structure and then determines the surface stress state of the component based on the strain-stress relationship. During measurement, resistance strain gauges are attached to the surface of the part at the measurement point. When the part produces strain under load, the resistance strain gauge undergoes a corresponding change in resistance. This change is measured by the strain gauge, and the strain and stress at the measurement point can then be calculated.

[0006] Fiber Bragg grating (FBG) testing is a stress-strain measurement method that has developed rapidly over the past 20 years. Due to the ease of constructing distributed sensor networks, it is now widely used in fields such as construction, bridges, shipbuilding, and chemical engineering. By monitoring the wavelength of the reflected light from the FBG using a FBG demodulator and calculating, analyzing, and processing the test data through appropriate programs, the strain value at the FBG sensor can be obtained.

[0007] Digital Image Correlation (DIC) processes digital images using computer vision principles. It converts a series of speckle images of a measured object before and after deformation, recorded by a high-speed camera, into a corresponding digital speckle grayscale field. Then, it performs correlation operations on the digital speckle grayscale field (such as Gauss-Newton nonlinear iterative least squares method, mean shift algorithm, etc.) to find the extreme points of the correlation coefficient and obtain the corresponding displacement and strain information.

[0008] In summary, some shortcomings of existing technologies can be identified:

[0009] 1. Traditional strain testing methods often require processing materials into suitable sizes and shapes, and attaching strain gauges to the surface of the test piece or applying stress for measurement. However, the cutting process is a dynamic process, and different material layers vary greatly, making it impossible to perform local testing under conditions of tiny cutting edges.

[0010] 2. The fiber Bragg grating testing method requires a grating, and the grating ruler itself has a certain size. Furthermore, this method places high demands on the installation and adjustment of the grating. The machinability of laminated materials primarily studies the strain properties of the material layers and interfaces; the testing range of the fiber Bragg grating method does not match the testing requirements for laminated materials.

[0011] 3. Ordinary digital image correlation technology can realize strain analysis under cutting force load. However, due to the very short time that the cutting edge spends traversing different laminated materials during high-speed cutting, extremely high camera frame rates are required to capture the dynamic changes of the cutting edge action. At the same time, due to ordinary cutting test conditions, the camera cannot directly capture the cutting area and cannot directly reflect the strain in the area where the cutting edge is acting.

[0012] 4. Direct machining testing using specialized instruments can test the changes in the cutting performance of different materials, but multiple cutting tests are required for different materials. Given the microscale range effects of material interfaces, this type of method is not easy to distinguish the differences in material properties between different layers and interfaces of laminated materials. Summary of the Invention

[0013] This invention is made to solve the above-mentioned problems, and aims to provide a device and method for testing the cutting strain of laminated materials based on DIC technology.

[0014] This invention provides a multilayer material cutting strain testing device based on DIC technology, characterized by the following features: a cutting mechanism including a high-speed linear motor, a Y-axis micro-motion platform, a tool assembly, and a piezoelectric ceramic actuator; the high-speed linear motor has a linear guide rail arranged along the X-axis direction; the Y-axis micro-motion platform is mounted on a slider of the linear guide rail for adjusting the position of the tool assembly in the Y-axis direction; the tool assembly is mounted along the Y-axis direction on the Y-axis micro-motion platform; and the piezoelectric ceramic actuator is mounted on the tool assembly for dynamically fine-tuning the cutting depth; at least two workpiece clamping mechanisms are spaced apart on one side of the linear guide rail along the X-axis direction, each workpiece clamping mechanism for clamping a multilayer material workpiece and adjusting the position of the clamped multilayer material workpiece; and an image acquisition mechanism, including... The system includes a high-speed camera, a synchronous trigger, a magnetic block, an accelerometer, and a signal processor. The high-speed camera is mounted on the other side of the linear guide rail and is used to capture images of the laminated material workpiece during the cutting process. The synchronous trigger is communicatively connected to the high-speed camera and is used to control the high-speed camera to capture images. The magnetic block is mounted on a piezoelectric ceramic driver and is used to trigger the synchronous trigger when it passes by the synchronous trigger under the drive of a high-speed linear motor. The accelerometer is mounted on the workpiece clamping mechanism and is used to generate a vibration acceleration signal when the tool just cuts the laminated material workpiece. The signal processor is connected between the high-speed camera and the accelerometer and is used to transmit the vibration acceleration signal to the high-speed camera. The system also includes a computer connected to the high-speed camera, which is used to store the images captured by the high-speed camera and process them to obtain a cutting strain diagram.

[0015] The laminated material cutting strain testing device based on DIC technology provided by the present invention may also have the following features: wherein the tool assembly includes a tool guide groove and a tool, the tool guide groove is mounted on the Y-axis micro-motion platform, the head end of the tool is the cutting end and extends from one end of the tool guide groove, and the tail end of the tool is located in the tool guide groove.

[0016] The piezoelectric ceramic actuator provided by the present invention for testing the cutting strain of laminated materials based on DIC technology may also have the following feature: the piezoelectric ceramic actuator is connected to the tail end of the tool and is mounted at the other end of the tool guide groove via a bearing.

[0017] The piezoelectric ceramic actuator provided by this invention can also have the following feature: the piezoelectric ceramic actuator adopts PID control.

[0018] The DIC-based cutting strain testing device for laminated materials provided by this invention may also have the following features: the Y-axis micro-motion platform includes a Y-axis slide and a Y-axis micrometer. The Y-axis slide is mounted on the slider of the linear guide rail, and the Y-axis micrometer is mounted on the side of the Y-axis slide and is used to adjust the position of the Y-axis slide on the Y-axis.

[0019] The laminated material cutting strain testing device based on DIC technology provided by the present invention may also have the following features: the workpiece clamping mechanism includes an L-shaped worktable and an XZ-axis micro-motion platform and a stepper motor disposed thereon. The XZ-axis micro-motion platform is used to adjust the position of the laminated material workpiece in the X-axis direction and the Z-axis direction. The output shaft of the stepper motor is connected to the L-shaped worktable along the Y-axis direction. The stepper motor is used to adjust the angle of the laminated material workpiece.

[0020] The DIC-based multilayer material cutting strain testing device provided by this invention may also have the following features: the XZ-axis micro-motion platform includes a Z-axis slide, a Z-axis micrometer, an X-axis slide, and an X-axis micrometer. The Z-axis slide is mounted on an L-shaped worktable, and the Z-axis micrometer is mounted on the side of the Z-axis slide and used to adjust the position of the Z-axis slide on the Z-axis. The X-axis slide is mounted on the Z-axis slide, and the X-axis micrometer is mounted on the side of the X-axis slide and used to adjust the position of the X-axis slide on the X-axis.

[0021] This invention also provides a method for testing the cutting strain of laminated materials based on DIC technology. The method, employing the aforementioned DIC-based laminated material cutting strain testing device, includes the following steps: S1. Preparing a corresponding number of laminated material workpieces according to the number of material types, and arranging a corresponding number of workpiece clamping mechanisms; S2. Installing each laminated material workpiece on its respective workpiece clamping mechanism, ensuring that all laminated material workpieces are on the same plane parallel to the linear guide rail; S3. Using a high-speed linear motor to drive the tool assembly to perform cutting motion on all laminated material workpieces. When the magnetic block triggers the synchronous trigger, the high-speed camera quickly responds and captures an image. The frame rate of the high-speed camera and the relative position between each laminated material workpiece are adjusted based on the image to ensure that the high-speed camera accurately captures the strain image of each laminated material workpiece during the cutting process; S4. Processing the images using a computer to obtain the cutting strain diagram of the laminated material.

[0022] The method for testing the cutting strain of laminated materials based on DIC technology provided by this invention may also have the following features: In step S2, installing each laminated material workpiece on each workpiece clamping mechanism includes the following steps: installing one laminated material workpiece on a workpiece clamping mechanism, and determining the positions of the remaining laminated material workpieces in sequence by calculating the speed of the high-speed linear motor, the thickness of the laminated material workpiece, and the frame rate of the high-speed camera according to the position of the laminated material workpiece, and completing the installation.

[0023] The method for testing the cutting strain of laminated materials based on DIC technology provided by this invention may also have the following features: In step S3, adjusting the frame rate of the high-speed camera and the relative position between each laminated material workpiece includes the following steps: linearly adjusting the frame rate of the high-speed camera to correspond to the time node when the tool cuts one interlayer interface of a laminated material workpiece, and sequentially adjusting the position of the remaining laminated material workpieces based on the image overlay method so that the time node when the tool cuts different interlayer interfaces of the remaining laminated material workpieces also corresponds to the frame rate of the high-speed camera.

[0024] The role and effect of invention

[0025] The advantages of the cutting strain testing device and method for laminated materials based on DIC technology according to the present invention, compared with the prior art, are mainly reflected in the following aspects:

[0026] 1) Due to the alternating arrangement of multiple layers in laminated materials, traditional contact measurement methods cannot simultaneously obtain displacement and strain information for each layer. However, non-contact measurement methods based on DIC technology can achieve strain measurement for each layer, thereby more accurately analyzing and evaluating the performance of laminated materials. The device and method used in this invention are suitable for strain measurement of laminated materials and can effectively solve the difficulties and limitations of traditional methods in the measurement of laminated materials.

[0027] 2) Compared with traditional computer vision methods, this device and method are based on DIC technology, which can quickly perform large-scale data processing and ensure high-quality measurement results. At the same time, in practical applications, the frame rate requirements under different conditions can be met by flexibly adjusting the parameters, which has a wide range of applicability.

[0028] 3) In traditional milling tests, the rotation of the spindle generates centrifugal and inertial forces, which can cause vibration and deformation of the specimen, thus affecting the accuracy and reliability of the test results. However, the cutting mechanism in this invention uses a high-speed linear motor to replace the rotation of the machine tool spindle to realize the main motion of the tool. That is, the complex three-dimensional cutting is equivalently transformed into cutting on a two-dimensional plane. This can effectively reduce the vibration and deformation of the specimen, ensure the accuracy and repeatability of the test results, and make it easier to observe and record the cutting process under the same experimental conditions. Furthermore, the characteristics of three-dimensional milling can be obtained through simulation. With theoretical support, the experimental process can be simplified, the experimental efficiency can be improved, and the cost and time can be reduced. At the same time, during the shooting process, it is difficult to capture the surface of the specimen from all angles and positions in ordinary milling, while the two-dimensional cutting test can be carried out on a plane, making it easier to observe and record the changes and deformations that occur during the test.

[0029] 4) Based on the Y-axis micro-motion platform for depth of cut adjustment, the cutting mechanism adds a cutting extension and retraction micro-adjustment function based on piezoelectric ceramic micro-actuation, which can realize the dynamic change of the tool depth of cut during the cutting process, and can complete the chip thickness test without deformation, so as to truly reflect the chip path during the milling process.

[0030] 5) The workpiece clamping mechanism adopts an XZ axis micro-motion platform and a stepper motor, which can adjust the X and Z axis position coordinates and rotation angle of the laminated material to achieve cutting to different material layer combinations, different material thicknesses, and different cutting angles, meeting the interlayer testing requirements of laminated materials. At the same time, the stepper motor adopts micro-angle closed-loop control adjustment, which can realize the cutting test of specific laminated materials.

[0031] 6) When performing cutting strain testing, the frame rate of the high-speed camera is calculated by utilizing the positional relationship between the stacked material workpieces on each workpiece clamping mechanism. With the help of the magnetic attraction synchronous trigger, the instantaneous workpiece strain state during the cutting process at high cutting speed can be captured. Combined with the acceleration sensor signal triggering function, the DIC shooting triggering conditions are met to ensure the accuracy and authenticity of the strain image.

[0032] 7) In order to accurately capture strain images of the interlayers and interfaces of the laminated material, based on the hardware and software triggering device, a corresponding number of laminated material workpieces are prepared according to the number of material types of the laminated material, and a corresponding number of workpiece clamping mechanisms are arranged. Each laminated material workpiece is installed on its respective workpiece clamping mechanism, and each laminated material workpiece is used by a high-speed camera to accurately capture cutting images of different interfaces. At the same time, the cutting experiment can be verified from any position. Thus, this device and method can accurately analyze the strain information of the laminated material at any position. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the laminated material cutting strain testing device in Embodiment 1 of the present invention;

[0034] Figure 2 This is a schematic diagram of the installation structure of the tool assembly and piezoelectric ceramic actuator in Embodiment 1 of the present invention, wherein (a) is a perspective view and (b) is a cross-sectional view;

[0035] Figure 3 This is a schematic diagram of the thickness of the undeformed chip in Embodiment 1 of the present invention, wherein (a) is a schematic diagram of the trajectory of the tool simulated by MATLAB when the previous cutting edge cuts into the workpiece to the maximum depth and starts to rotate 180° and feed at the same time, and (b) is a schematic diagram of the curve of the change of the thickness of the undeformed chip with angle (time).

[0036] Figure 4 This is a schematic diagram of the layout of the laminated material workpiece in Embodiment 1 of the present invention;

[0037] Figure 5 This is a schematic diagram of the XZ axis micro-motion platform in Embodiment 1 of the present invention;

[0038] Figure 6 This is a schematic diagram of the layout of the laminated material workpiece in Embodiment 2 of the present invention.

[0039] Explanation of reference numerals in the attached figures:

[0040] 1-Layered material workpiece; 10-Cutting mechanism; 11-Linear guide rail; 12-Y-axis micro-motion platform; 13-Tool assembly; 131-Tool guide groove; 132-Tool; 14-Piezoelectric ceramic actuator; 15-Ball bearing; 20-Workpiece clamping mechanism; 21-L-shaped worktable; 22-XZ-axis micro-motion platform; 221-Z-axis slide; 222-Z-axis micrometer; 223-X-axis slide; 224-X-axis micrometer; 23-Stepper motor; 30-Image acquisition mechanism; 31-High-speed camera; 32-Synchronous trigger; 33-Magnetic block; 34-Acceleration sensor; 35-Signal processor; 40-Computer. Detailed Implementation

[0041] To make the technical means, creative features, objectives and effects of this invention easier to understand, the following embodiments are described in detail with reference to the accompanying drawings.

[0042] Example 1

[0043] Figure 1 This is a schematic diagram of the structure of a multilayer material cutting strain testing device.

[0044] like Figure 1 As shown, this embodiment provides a cutting strain testing device for laminated materials based on DIC technology, including a cutting mechanism 10, two workpiece clamping mechanisms 20, an image acquisition mechanism 30, and a computer 40. The details of each part are described below.

[0045] The cutting mechanism 10 is used to perform cutting motion on the laminated material workpiece, and includes a high-speed linear motor, a Y-axis micro-motion platform 12, a tool assembly 13, and a piezoelectric ceramic actuator 14.

[0046] The high-speed linear motor has a linear guide 11 arranged along the X-axis, which consists of a slide rail and a slider mounted on the slide rail. Using a high-speed linear motor to replace the machine tool spindle rotation for the main tool motion avoids the centrifugal and inertial forces generated by spindle rotation in traditional milling tests. These forces can cause vibration and deformation of the specimen, thus affecting the accuracy and reliability of the test results. Using a high-speed linear motor for the main tool motion effectively reduces specimen vibration and deformation, ensuring the accuracy and repeatability of the test results.

[0047] The Y-axis micro-motion platform 12 is mounted on the slider of the linear guide 11. The Y-axis micro-motion platform 12 includes a Y-axis slide and a Y-axis micrometer. The Y-axis slide is mounted on the slider of the linear guide 11, and the Y-axis micrometer is mounted on the side of the Y-axis slide and is used to adjust the position of the Y-axis slide on the Y-axis.

[0048] Figure 2 This is a schematic diagram of the mounting structure of the tool assembly 13 and the piezoelectric ceramic actuator 14.

[0049] The tool assembly 13 is mounted on the Y-axis micro-motion platform 12. For example... Figure 2 As shown, the tool assembly 13 includes a tool guide groove 131 with a square cross-section and arranged along the Y-axis direction, and a tool 132 disposed in the tool guide groove 131. The tool guide groove 131 is mounted on the Y-axis micro-motion platform 12. The head end of the tool 132 is the cutting end and extends from one end of the tool guide groove 131, and the tail end of the tool 132 is located in the tool guide groove 131.

[0050] The piezoelectric ceramic actuator 14 is connected to the tail end of the tool 132 and is mounted at the other end of the tool guide groove 131 via a ball bearing 15. Since the thickness of the undeformed chip has a significant impact on the milling force and milling temperature during the milling process, a piezoelectric ceramic actuator 14 with micro-feed function is provided at the tail end of the tool 132.

[0051] The piezoelectric ceramic actuator 14 can be used to perform cutting tests based on the undeformed chip thickness. Specifically, by adding the undeformed chip thickness calculated by MATLAB to the piezoelectric ceramic actuator, the depth direction of the cutting tool 132 can be adjusted. With the high resolution and high dynamic response PID control, the cutting depth can be dynamically fine-tuned during the cutting process, thereby simulating the undeformed chip thickness in the real milling process.

[0052] The process and principle of MATLAB for calculating the thickness of undeformed chips are as follows: Figure 3 As shown in (a), two sets of parametric equations for long-amplitude cycloids are generated using MATLAB to simulate the process where tool 132 rotates 180° and feeds simultaneously when the previous cutting edge penetrates the workpiece to its maximum depth (1.5π < θ < 2.5π). O′ to O″ is the trajectory of the center point during this process, with the starting point being (1.5π*s, 0), where s is the feed rate. O is the center of tool 132 at a certain angle, and the straight line OA2 is the line connecting the next cutting edge point to the center of tool 132. The straight line intersects the original edge line of the workpiece at point A0 and the trajectory line of the previous cutting edge point of the workpiece (i.e., the machined surface of the workpiece) at point A1.

[0053] Clearly, the distance |OA2| is the radius of tool 132, which is a constant value r. Therefore, there are four cases for calculating |OA0| and |OA1|:

[0054] 1. max(|OA0|,|OA1|)≥r, at this time the tip of the tool does not touch the surface of the machined workpiece.

[0055] 2. max(|OA0|, |OA1|) < r, and |OA0| < r. o When |=|OA1|, the tip of the back cutter is at the critical position, and the thickness of the undeformed chip is the largest.

[0056] 3. max(|OA0|,|OA1|)<r,and |OA0|<|OA1|,after the tool tip is in the critical position, the thickness of the undeformed chip gradually increases (see the marked m region).

[0057] 4. max(|OA0|,|OA1|)<r,and |OA0|>|OA1|,At this time, after the back tip is in the critical position, the thickness of the undeformed chip gradually decreases (see the marked n region).

[0058] Based on the above analysis, the curves showing the variation of undeformed chip thickness with angle (time) were obtained using MATLAB, as shown below. Figure 3 As shown in (b), the instantaneous undeformed chip thickness can then be obtained.

[0059] The piezoelectric ceramic actuator 14 can also be used to complete vibration-assisted machining tests. Specifically, vibration parameters are applied to the piezoelectric ceramic actuator to generate a certain vibration frequency and amplitude, and the connected tool 132 also vibrates to a certain extent. By measuring the cutting force with a force measuring instrument, the cutting test with external vibration assistance of the tool 132 can be realized.

[0060] like Figure 1 As shown, each workpiece clamping mechanism 20 is used to clamp a stacked material workpiece 1 and adjust the position of the clamped stacked material workpiece 1. Each workpiece clamping mechanism 20 includes an L-shaped worktable 21 and an XZ axis micro-motion platform 22 and a stepper motor 23 mounted thereon.

[0061] In this embodiment, there are two workpiece clamping mechanisms 20, which are spaced apart along the X-axis on one side of the corresponding cutting end of the tool 132 on the linear guide 11. Figure 4 As shown in the schematic diagram of the layout of the laminated material workpiece, in this embodiment, two laminated materials (each layer thickness is in the millimeter range and varies) prepared from material A and material B are used as workpieces. They are respectively clamped on two workpiece clamping mechanisms 20. One is used by the image acquisition mechanism 30 to capture the cutting image of interface 1, and the other is used by the image acquisition mechanism 30 to capture the cutting image of interface 2.

[0062] Figure 5 This is a schematic diagram of the XZ axis micro-motion platform 22.

[0063] The XZ-axis micro-motion platform 22 is mounted on the vertical part of the L-shaped worktable 21 facing the high-speed linear motor. The XZ-axis micro-motion platform 22 is used to adjust the coordinates of the laminated material workpiece 1 on the X and Z axes. Figure 5 As shown, the XZ-axis micro-motion platform 22 includes a Z-axis slide 221, a Z-axis micrometer 222, an X-axis slide 223, and an X-axis micrometer 224. The Z-axis slide 221 is mounted on the vertical portion of the L-shaped worktable 21. The Z-axis micrometer 222 is mounted on the side of the Z-axis slide 221 and is used to adjust the position of the Z-axis slide 221 on the Z-axis. The X-axis slide 223 is mounted on the Z-axis slide 221, and the X-axis micrometer 224 is mounted on the side of the X-axis slide 223 and is used to adjust the position of the X-axis slide 223 on the X-axis.

[0064] The stepper motor 23 is fixed by a support base (not shown in the figure). The output shaft of the stepper motor 23 is set along the Y-axis and connected to the vertical part of the L-shaped worktable 21. The stepper motor 23 is connected to a microcontroller and adopts micro-angle closed-loop control, which can perform micro-angle adjustment on the whole composed of the L-shaped worktable 21 and the XZ-axis micro-motion platform 22 to realize the function of workpiece cutting angle adjustment.

[0065] The XZ axis micro-motion platform 22 and stepper motor 23 can adjust the coordinates of the laminated material. Together with the Y axis micro-motion platform 12 of the cutting mechanism 10, cutting tests of different material layer combinations, different material thicknesses, and different cutting angles of the laminated material can be realized.

[0066] like Figure 1 As shown, the image acquisition mechanism 30 is used to capture images of the laminated material workpiece 1, and includes a high-speed camera 31, a synchronous trigger 32, a magnetic block 33, an accelerometer 34, and a signal processor 35.

[0067] The high-speed camera 31 is supported by a tripod and is located on the other side of the linear guide rail 11 of the high-speed linear motor. The lens of the high-speed camera 31 is focused on the L-shaped worktable 21 of the workpiece clamping mechanism 20 to select an appropriate image resolution and imaging area. The frame rate of the high-speed camera 31 is calculated by quantizing the layer thickness of the laminated material and the speed of the high-speed linear motor.

[0068] The synchronous trigger 32 is communicatively connected to the high-speed camera 31. The synchronous trigger 32 is mounted on the linear guide rail 11 and at the same height as the piezoelectric ceramic actuator 14. A magnetic block 33 is mounted at the tail end of the piezoelectric ceramic actuator 14. The contact signal between the synchronous trigger 32 and the magnetic block 33 is a hard trigger signal that triggers the high-speed camera 31 to capture images. When the magnet passes the position of the synchronous trigger 32 driven by the high-speed linear motor, the synchronous trigger 32 is triggered to generate a contact signal. The high-speed camera 31 responds quickly based on the contact signal, accurately capturing a digital image at a specific time and location.

[0069] An accelerometer 34 is mounted on the L-shaped worktable 21. The accelerometer 34 is used to generate a vibration acceleration signal when the tool 132 just cuts into the laminated material workpiece. This vibration acceleration signal is a soft trigger signal that triggers the high-speed camera 31 to capture images. When the tool 132 contacts the laminated material workpiece 1, a rising edge of the vibration acceleration signal is generated, thereby triggering the high-speed camera 31 to capture images, and simultaneously monitoring the stability during the cutting process in real time.

[0070] The signal processor 35 is connected between the high-speed camera 31 and the accelerometer 34 via a signal line. The signal processor 35 is used to quickly transmit the vibration acceleration signal from the accelerometer 34 to the high-speed camera 31, so that the high-speed camera 31 can respond quickly and accurately capture digital images at specific times and locations.

[0071] Computer 40 is connected to high-speed camera 31 via signal lines. Computer 40 is used to store images captured by high-speed camera 31 and to calculate the cutting strain diagram of the laminated material using existing DIC algorithms (such as Gauss-Newton nonlinear iterative least squares method, mean shift algorithm, etc.).

[0072] The following is a detailed explanation of the process and method for performing cutting strain tests on laminated materials using this laminated material cutting strain testing device.

[0073] S1. Prepare a corresponding number of laminated material workpieces 1 according to the number of material types of the laminated material, and arrange a corresponding number of workpiece clamping mechanisms 20. In this embodiment, there are two laminated material workpieces 1, and two workpiece clamping mechanisms 20 are arranged according to... Figure 1 The arrangement shown is shown in the figure.

[0074] S2. Install the two laminated material workpieces 1 onto the two workpiece clamping mechanisms 20 respectively. Specifically, install the two laminated material workpieces 1 onto the XZ-axis micro-motion platforms 22 of the two workpiece clamping mechanisms 20 respectively. First, adjust one XZ-axis micro-motion platform 22 to determine the position of the laminated material workpiece 1 on it. Then, further determine the position of the other laminated material workpiece 1 by calculating the speed of the high-speed linear motor, the thickness of the laminated material workpiece 1, and the frame rate of the high-speed camera 31. The angle of each laminated material workpiece 1 can be flexibly adjusted by the micro-angle control of the corresponding stepper motor 23, which can meet the needs of experimenting on laminated material workpieces 1 with specific shapes (such as wedges). Before the cutting experiment begins, install a dial indicator on the linear guide rail 11 of the high-speed linear motor to traverse the surface of the two laminated material workpieces 1 to ensure that the two laminated material workpieces 1 are on the same plane parallel to the linear guide rail 11.

[0075] The frame rate of the high-speed camera 31 is calculated using the speed of the high-speed linear motor and the thickness of the laminated material workpiece 1. Specifically, two-dimensional cutting is used to simulate three-dimensional high-speed milling. Taking a linear motor speed of up to 8 m / s as an example, combined with the thickness of each material layer of the laminated material workpiece 1 at the millimeter level, the cutting time of the tool 132 on the laminated material workpiece 1 can be calculated, and thus the basic frame rate of the high-speed camera 31 can be calculated to be approximately 3000-4000 f / s.

[0076] S3. A cutting experiment is conducted on two laminated material workpieces 1. During the experiment, the frame rate of the high-speed camera 31 and the relative position of the two laminated material workpieces 1 are adjusted to ensure that the strain images of the two laminated material workpieces 1 during the cutting process can be accurately captured.

[0077] Specifically, the high-speed linear motor drives the tool 132 to perform cutting motion. When the tool 132 passes the synchronous trigger 32, i.e., trigger point N, the magnetic block 33 triggers the synchronous trigger 32, and the high-speed camera 31 quickly responds and captures an image.

[0078] The process of linearly adjusting the frame rate of the high-speed camera 31 and adjusting the relative position of the two laminated material workpieces 1 based on the captured images is as follows: 1. First, ensure that the high-speed camera 31 accurately captures the speckle image of the interface 1. For example... Figure 4 As shown, H is the overall thickness of a single laminated material workpiece, h1 is the thickness of single-layer material A, h2 is the thickness of single-layer material B, D1 is the distance from trigger point N to the adjacent laminated material workpiece, D2 is the distance between two laminated material workpieces, and the distance from trigger point N to interface 1 is D1 + h1. To ensure that the high-speed camera 31 can accurately capture the image of the tool 132 cutting into interface 1, the frame rate f of the high-speed camera 31 must be adjusted to correspond to the time node t1 when the tool 132 cuts into interface 1. The formula used in this process is as follows:

[0079]

[0080]

[0081]

[0082] Where v is the cutting speed of the milling cutter, which is replaced by the speed of tool 132, D is the diameter of the milling cutter, and n is the rotational speed of the machine tool spindle.

[0083] 2. Ensure that the high-speed camera 31 accurately captures the speckle image of interface 2. Specifically, because the thicknesses of the two material layers of the laminated material workpiece 1 are inconsistent, even if the distance D1 from the fixed trigger point N to the adjacent laminated material is fixed, ensuring that the high-speed camera 31 can capture the cutting image of interface 1, it is not guaranteed that the high-speed camera 31 can continuously capture an integer number of cutting images at the position and distance scale marked h2. To ensure that the high-speed camera 31 can accurately capture the image of interface 2, another laminated material workpiece is arranged as shown in the figure. The XZ axis micro-motion platform 22 is adjusted to move the other laminated material by a distance D2. The adjustment of D2 can be regarded as aligning a certain position of the continuously captured image of the high-speed camera 31 with the position of interface 2, that is, obtaining D2 = x - D1 - H, so that the time node when the tool 132 passes through interface 2 corresponds to the frame rate of the high-speed camera 31, thereby achieving the requirement.

[0084] S4. After the images at interfaces 1 and 2 are accurately captured by the high-speed camera 31, the images are processed by the computer 40 using the DIC algorithm to obtain the cutting strain diagram of the laminated material.

[0085] It should be noted that this DIC-based laminated material cutting strain testing device can start cutting experiments from any position, such as cutting from material A to material B, or cutting from material B to material A, or for laminated materials with more material combinations, thereby accurately analyzing the information of arbitrary displacement strain of the laminated material.

[0086] Example 2

[0087] This embodiment provides a multilayer material cutting strain testing device based on DIC technology. The difference from Embodiment 1 is that the number of workpiece clamping mechanisms is three. The three workpiece clamping mechanisms are arranged in a row at intervals and are set parallel to the linear guide rail of the high-speed linear motor.

[0088] like Figure 6The layout diagram of the laminated material workpiece is shown. In this embodiment, a laminated material (each layer thickness is in the millimeter range and varies) made of material A, material B and material C is used as the workpiece. There are three workpieces, which are respectively clamped on three workpiece clamping mechanisms 20, so that the image acquisition mechanism 30 can capture the cutting images of interface 1, interface 2 and interface 3 respectively. In the figure, D3 is the distance between the second laminated material workpiece and the third laminated material workpiece. The other parameters are the same as in embodiment 1.

[0089] The process and method for testing the cutting strain of laminated materials using this laminated material cutting strain testing device differ from that in Example 1 in that the process of adjusting the frame rate of the high-speed camera 31 during the experiment is as follows: 1. First, ensure that the high-speed camera 31 accurately captures the speckle image of interface 1. The specific process is the same as in Example 1 and will not be repeated here; 2. Ensure that the high-speed camera 31 accurately captures the speckle image of interface 2. The specific process is the same as in Example 1 and will not be repeated here; 3. Ensure that the high-speed camera 31 accurately captures the speckle image of interface 3. Arrange the third laminated material workpiece as shown in the figure, adjust the XZ axis micro-motion platform 22, and move the third laminated material by one D3. The adjustment of D3 can be regarded as aligning a certain position of the continuously captured image of the high-speed camera 31 with the position of interface 3, that is, obtaining D3 = x - D1 - 2H - D2, so that the time node when the tool 132 passes through interface 3 also corresponds to the frame rate of the high-speed camera 31, thereby achieving the requirements.

[0090] According to the above embodiments, for those skilled in the art, the cutting strain testing device and cutting strain testing method for laminated materials based on DIC technology of this application can be used for laminated materials composed of two or more material layers and the thickness of each material layer may be different.

[0091] The role and effect of the embodiments

[0092] According to the DIC-based multilayer material cutting strain testing device and method described in the above embodiments, by quantifying the cutting speed of the tool and the thickness of each layer of the multilayer material, and in conjunction with the frame rate adjustment of the high-speed camera, the path traveled by the tool and the strain image obtained at the end correspond one-to-one, and the strain at the interface between the layers of the multilayer material can be accurately calculated.

[0093] Using a high-speed linear motor as the main motion of the cutting tool, and in conjunction with the static and dynamic depth of cut micro-adjustment of the piezoelectric ceramic at the rear end of the tool, the cutting performance of the laminated material layers and interlayer interfaces was tested, compared and analyzed under two-dimensional cutting test conditions, to realistically simulate the change in undeformed chip thickness during the milling process.

[0094] In this method, a high-speed linear motor replaces the machine tool spindle rotation to achieve the main motion of the cutting tool, avoiding the centrifugal and inertial forces generated by the spindle rotation in traditional milling tests. These forces can cause vibration and deformation of the specimen, thus affecting the accuracy and reliability of the test results. Using a high-speed linear motor for the main tool motion can effectively reduce the vibration and deformation of the specimen, ensuring the accuracy and repeatability of the test results.

[0095] The clamping of laminated materials can achieve XZ micro-motion, enabling cutting tests of different material layer combinations and thicknesses. At the same time, cutting tests can be started from any position to verify the results, thereby accurately analyzing arbitrary displacement and strain information.

[0096] The stepper motor uses micro-angle closed-loop control adjustment, which can adjust the rotation angle of the laminated material, thereby adjusting the cutting angle during the cutting experiment. If the number of laminated materials is increased, the number of stepper motors can also be increased accordingly to ensure that the cutting angle can be adjusted simultaneously.

[0097] By utilizing the shooting trigger principle, the test can accurately capture images of the layers and interfaces of the stacked materials. This can reduce the requirements of high-speed camera frame rate and experimental environment conditions for high-speed continuous shooting, reduce the number of images, and improve the efficiency of DIC strain testing.

[0098] By utilizing the magnetically attached synchronous trigger and the acceleration sensor signal trigger, the high-speed camera can quickly and accurately acquire images of the cutting strain zone, thereby obtaining a speckle pattern of cutting strain switching under high-speed cutting and rapid response conditions. At the same time, the acceleration sensor ensures stability during the cutting process.

[0099] The above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. A DIC technique-based lamination material cutting strain test device, characterized by, The cutting mechanism comprises a high-speed linear motor, a Y-axis micro-motion platform, a tool assembly, and a piezoelectric ceramic driver, The high-speed linear motor has a linear guide rail arranged along the X-axis direction, The Y-axis micro-motion platform is mounted on the slider of the linear guide rail and used to adjust the position of the tool assembly along the Y-axis direction, The tool assembly is mounted on the Y-axis micro-motion platform along the Y-axis direction, The piezoelectric ceramic driver is mounted on the tool assembly and used to dynamically adjust the cutting depth of the tool, At least two workpiece clamping mechanisms are arranged at intervals along the X-axis direction on one side of the linear guide rail, and each workpiece clamping mechanism is used to clamp a laminated material workpiece and adjust the position of the clamped laminated material workpiece, The image acquisition mechanism comprises a high-speed camera, a synchronous trigger, a magnetic block, an acceleration sensor, and a signal processor, The high-speed camera is arranged on the other side of the linear guide rail and used to capture images of the laminated material workpiece during the cutting process, The synchronous trigger is in communication connection with the high-speed camera and used to control the high-speed camera to capture images, The magnetic block is mounted on the piezoelectric ceramic driver and used to trigger the synchronous trigger when the high-speed linear motor drives the magnetic block to pass the synchronous trigger, The acceleration sensor is mounted on the workpiece clamping mechanism and used to generate a vibration acceleration signal when the tool just cuts the laminated material workpiece, The signal processor is connected between the high-speed camera and the acceleration sensor and used to transmit the vibration acceleration signal to the high-speed camera, and A computer is connected with the high-speed camera and used to store the images captured by the high-speed camera and process the images to obtain a cutting strain map.

2. The DIC technology-based laminated material cutting strain testing device according to claim 1, wherein: The tool assembly comprises a tool guide groove and a tool, The tool guide groove is mounted on the Y-axis micro-motion platform, wherein The head end of the tool is a cutting end and extends from one end of the tool guide groove, and the tail end of the tool is located in the tool guide groove.

3. The DIC technology-based laminated material cutting strain testing device according to claim 2, wherein: The piezoelectric ceramic driver is connected with the tail end of the tool and mounted at the other end of the tool guide groove through a bearing.

4. The DIC technology-based laminated material cutting strain testing device according to claim 1, wherein: wherein The piezoelectric ceramic driver adopts PID control.

5. The DIC technology-based laminated material cutting strain testing device according to claim 1, wherein: wherein The Y-axis micro-motion platform comprises a Y-axis sliding table and a Y-axis screw micrometer, The Y-axis sliding table is mounted on the slider of the linear guide rail, wherein, The Y-axis screw micrometer is mounted on the side surface of the Y-axis sliding table and used to adjust the position of the Y-axis sliding table along the Y-axis.

6. The DIC technology-based laminated material cutting strain testing device according to claim 1, wherein: The workpiece clamping mechanism comprises an L-shaped workbench, an XZ-axis micro-motion platform arranged on the L-shaped workbench, and a stepping motor, ​ wherein ​ The XZ-axis micro-motion platform is used to adjust the position of the laminated material workpiece in the X-axis direction and the Z-axis direction, The output shaft of the stepping motor is arranged along the Y-axis direction and connected with the L-shaped workbench, and the stepping motor is used to adjust the angle of the laminated material workpiece.

7. The DIC technology-based laminated material cutting strain testing device according to claim 6, characterized in that: wherein The XZ-axis micro-motion platform comprises a Z-axis sliding table, a Z-axis screw micrometer, an X-axis sliding table and an X-axis screw micrometer, The Z-axis sliding table is mounted on the L-shaped workbench, The Z-axis screw micrometer is mounted on the side of the Z-axis sliding table and used to adjust the position of the Z-axis sliding table in the Z-axis direction, The X-axis sliding table is mounted on the Z-axis sliding table, The X-axis screw micrometer is mounted on the side of the X-axis sliding table and used to adjust the position of the X-axis sliding table in the X-axis direction.

8. A method of testing the cutting strain of a laminated material based on the DIC technique, characterized by, The DIC technology-based laminated material cutting strain testing device according to any one of claims 1 to 7 comprises the following steps: S1. Preparing a corresponding number of laminated material workpieces according to the number of materials of the laminated material, and arranging a corresponding number of workpiece clamping mechanisms; S2. Mounting each laminated material workpiece on each workpiece clamping mechanism and ensuring that all the laminated material workpieces are in the same plane parallel to the linear guide rail; S3. Letting the high-speed linear motor drive the cutter assembly to perform cutting movement on all the laminated material workpieces, and when the magnetic block triggers the synchronous trigger, the high-speed camera quickly responds to capture images, the frame rate of the high-speed camera and the relative positions between each laminated material workpiece are adjusted according to the images, and the high-speed camera accurately captures the strain images of each laminated material workpiece in the cutting process; S4. Processing the images using a computer to obtain the cutting strain map of the laminated material.

9. The DIC technology-based laminated material cutting strain testing method according to claim 8, characterized in that: wherein In step S2, mounting each laminated material workpiece on each workpiece clamping mechanism comprises the following steps: Mounting one laminated material workpiece on one workpiece clamping mechanism, and sequentially determining the positions of the remaining laminated material workpieces by calculating the speed of the high-speed linear motor, the thickness of the laminated material workpiece and the frame rate of the high-speed camera according to the position of the laminated material workpiece, and completing the installation.

10. The DIC technology-based lamination material cutting strain test method according to claim 8, characterized in that: wherein, In step S3, adjusting the frame rate of the high-speed camera and the relative positions between each laminated material workpiece comprises the following steps: linearly adjusting the frame rate of the high-speed camera to correspond to the time node when the cutter cuts one interlayer interface of one laminated material workpiece, sequentially adjusting the positions of the remaining laminated material workpieces based on the image superposition method, so that the time nodes when the cutter cuts different interlayer interfaces of the remaining laminated material workpieces also correspond to the frame rate of the high-speed camera.

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