Arc additive control device and method based on dic full-field deformation measurement

Abstract

The application is an arc additive shape control device and method based on DIC full-field deformation measurement. It includes an arc additive DIC full-field deformation measurement system for real-time measurement of additive deformation, a computer workstation, a constant temperature preheating device, an infrared thermal imager device for real-time acquisition of the temperature of the additive workpiece, a local heat treatment system, a robot additive manufacturing platform; the computer workstation loads the arc additive simulation simulation module and the DIC system, uses the simulation simulation to simulate the deformation and mechanical behavior of the additive workpiece in the whole arc additive manufacturing temperature change process by taking the complete temperature field simulation result as the input condition; the constant temperature heating device is used for uniform preheating of the substrate; the local heat treatment system heats the deformed part of the workpiece, and the robot additive manufacturing platform is used for additive of the workpiece. The application solves the problems of residual stress distribution concentration and large deformation of the formed part in the process of arc additive manufacturing of meter-level metal workpieces.

Description

Technical Field

[0001] This invention belongs to the field of metal additive manufacturing, specifically relating to an arc additive manufacturing shape control device and method based on DIC full-field deformation measurement. Background Technology

[0002] Wafer Additive Manufacturing (WAAM) uses an electric arc as a heat source to melt and deposit metal wire, forming a solid part layer by layer. Among various additive manufacturing methods, WAAM stands out due to its advantages such as high additive efficiency, low manufacturing cost, wide range of wire selection, high utilization rate, and manufacturing process not limited by part size or equipment size, making it capable of handling meter-scale metal workpiece additive manufacturing tasks.

[0003] However, the temperature changes rapidly during arc additive manufacturing of meter-sized metal workpieces. The formed metal is subjected to unsteady, intense, periodic, and rapid heating and cooling thermal cycles for extended periods, resulting in complex thermal stresses. The rapid solidification of the molten pool under the strong constraints of the formed portion introduces complex condensation stresses within the workpiece, and external mechanical constraints also cause unpredictable mechanical stresses. Non-equilibrium solid-state phase transformations further generate non-equilibrium structural stresses. The combined effect of these stresses makes meter-sized metal workpieces more prone to deformation and cracking during additive manufacturing. Furthermore, the residual stresses and deformations from the metal additive manufacturing process easily lead to dimensional deviations between the formed part and the original model. These dimensional deviations accumulate during the additive manufacturing process, causing inconsistencies between process parameters and preset values ​​at certain locations in the deposition layer, such as the welding torch position. This, in turn, affects the additive manufacturing process, easily leading to defects such as slag inclusions, porosity, and cracks in the formed part, making continuous and stable additive manufacturing impossible. Thermal stress and deformation directly affect the shape and performance of metal additive manufacturing parts. Large deformations can lead to the interruption of additive manufacturing or even irreparable cracking, affecting the accuracy of machining and assembly.

[0004] Monitoring and controlling deformation during arc additive manufacturing has become crucial for improving the quality and stability of finished products. Deformation measurement includes coordinate measurement and displacement sensors. Coordinate measurement is mainly used to measure the deformation of parts after additive manufacturing, but it cannot be done in real time. Displacement sensors can only record deformation information at one or a few points, and cannot perform complete monitoring. Therefore, there is an urgent need for a method to monitor and control the deformation of large additively manufactured workpieces in real time, in order to solve the problems of concentrated residual stress distribution and large deformation of workpieces in the current process of arc additive manufacturing of meter-sized large workpieces.

[0005] CN114381627A discloses a method and apparatus for eliminating stress deformation during the arc additive manufacturing process of large components. It uses simulation to obtain stress-strain cloud maps of the additive components and performs ultrasonic stress measurement on the components, using vibration aging and other methods to control deformation. However, the ultrasonic stress measurement device suffers from drawbacks. Rough or uneven surfaces on the probe placement surface can lead to reflection and scattering of ultrasonic waves during propagation. Furthermore, the working principle, based on the acoustic properties of the material, changes with temperature during the additive manufacturing process, requiring correction to ensure the accuracy of the measurement results. For thicker materials, it can only provide stress information near the surface and cannot accurately measure the stress state at deeper levels. The propagation path of ultrasonic waves is limited by the geometry and structure of the material, allowing only local measurements and preventing a comprehensive assessment of the stress state of the entire material. This makes it unsuitable for real-time monitoring of meter-scale additive components with complex structures. Vibration aging, a control method, generates significant noise during application, making it unsuitable for high-pressure vessels, large-sized thin-walled works, and excessively rigid workpieces. It cannot replace heat treatment for purposes other than stress relief and is unsuitable for correcting existing deformation. The process effectiveness largely depends on the operator's theoretical knowledge and experience in vibration aging. Summary of the Invention

[0006] The purpose of this invention is to provide an arc additive manufacturing shape control device and method based on DIC full-field deformation measurement, so as to solve the problem that the non-uniform plastic deformation and microstructure changes during the thermal expansion and contraction process of current arc additive manufacturing of meter-scale metal workpieces cause large stress, resulting in large deformation of additive structural parts or even cracking.

[0007] The technical solution to achieve the purpose of this invention is: an arc additive manufacturing shape control device based on DIC full-field deformation measurement, including an arc additive DIC full-field deformation measurement system, a computer workstation, a constant temperature preheating device, an infrared thermal imager device, a local heat treatment system, and a robot additive manufacturing platform;

[0008] The electric arc additive manufacturing (AIC) full-field deformation measurement system is used for real-time measurement of the deformation of additive parts;

[0009] The computer workstation is equipped with an electric arc additive manufacturing simulation module and a DIC system. In the electric arc additive manufacturing simulation module, the temperature field simulation results are compared with the data recorded by the infrared thermal imager device to generate a thermal cycle curve to verify the effectiveness of the heat source model. The obtained complete temperature field simulation results are used as input conditions to simulate the deformation and mechanical behavior of the additive workpiece during the temperature change process of the overall electric arc additive manufacturing.

[0010] The constant temperature heating device is used to assist in the uniform preheating of the substrate, and the infrared thermal imager device is used to acquire the temperature of the additive workpiece in real time.

[0011] The local heat treatment system heats the deformed part of the workpiece based on the measurement results of the electric arc additive manufacturing (DIC) full-field deformation measurement system, and the robotic additive manufacturing platform is used for the additive manufacturing of the workpiece.

[0012] Furthermore, the arc additive manufacturing (AIC) full-field deformation measurement system includes two high-speed cameras and high-power blue LED lights, a matching DIC system, an air supply device, a baffle, a movable support, and a fixed support device.

[0013] Two high-speed cameras and a high-power blue LED light are mounted on a movable bracket via ball bearing slide rails. The high-speed cameras are connected to the computer of the matching DIC system. The movable bracket is embedded in the fixed bracket device. The air supply device is used to remove the dust generated during the additive manufacturing process.

[0014] The error of the full-field deformation measurement system of electric arc additive manufacturing (DIC) meets the following conditions: strain resolution: 3D≤0.002%; 2D≤0.001%; ​​strain measurement system noise 3D≤0.001%; ​​3D displacement resolution≤0.001 pixels; full-field displacement error ≤1σ in pixels.

[0015] Furthermore, the constant temperature preheating device has a built-in K-value temperature sensor that can operate normally within a range of 650℃.

[0016] The infrared thermal imager has a temperature measurement range of 0℃ to 1500℃.

[0017] The local heat treatment system is one or both of electromagnetic induction heating devices and flame heating devices.

[0018] Furthermore, the heating rate of the electromagnetic induction heating device is adjustable within the range of 0℃ / s to 400℃ / s, and the power is adjustable from 0 to 120kW. The output power can enable the additive workpiece within a depth of 8mm from the surface to reach 800 degrees Celsius in 3 to 5 seconds, and the maximum heating can reach 1200℃. The induction coil used in the electromagnetic induction heating device is selected and adjusted according to the specific shape of the additive workpiece.

[0019] The flame heating device includes a flamethrower and a combustible gas cylinder.

[0020] Furthermore, the robotic additive manufacturing platform includes: an additive power supply, an additive robot arm, a welding torch, a robot offline programming system, a wire feeder, a protective gas device, and a control system for controlling the additive motion trajectory of the additive robot arm.

[0021] An arc additive manufacturing shaping method based on the above-described device includes the following steps:

[0022] Step (1): Use simulation to obtain the deformation cloud map of the N-layer of the arc additive manufacturing process, and mark the areas with deformation exceeding 2mm as S. ii = 1, 2, ...;

[0023] Step (2): Arc additive manufacturing of N layers of workpiece and marking of area S i DIC monitoring was performed on areas with deformation exceeding 2mm. j Local heat treatment is performed for j=1, 2..., and the marked speckle region S in the DIC is observed simultaneously. j The deformation is varied until it is less than 0.25 mm, and then the next N layers of additive manufacturing are carried out.

[0024] Before the Nth layer of additive manufacturing is completed, maintain DIC for all speckle regions S. i and S j Real-time monitoring of deformation; when the deformation of the monitoring cloud map exceeds 2mm, additive manufacturing is stopped, and local heat treatment is used to eliminate the deformation of the new deformation of the original N layer and the speckle marking area of ​​the new deposition layer.

[0025] Repeat the above steps to complete the arc additive manufacturing process.

[0026] Furthermore, step (1) specifically includes the following steps:

[0027] Step (11): After modeling the multi-layer straight wall body, import it into the robot offline system, plan the additive path, generate the slice file, and import it into the additive control system to generate the additive program;

[0028] Step (12): After the substrate is polished, it is fixed to the base. The electric arc additive DIC full-field deformation measurement system is built. The infrared thermal imager device is fixed and the angle is adjusted for real-time temperature measurement during the additive process.

[0029] Step (13): Conduct an arc additive pre-test, start the infrared thermal imager device to measure the temperature of the additive component in real time, start the arc at one end of the welding torch, and add a straight wall body in a single layer on the substrate;

[0030] Step (14): Perform electric arc additive simulation on the straight wall body, compare the temperature field simulation results with the data recorded by the infrared thermal imager, plot the thermal cycle curve error diagram and modify the heat source model parameters until the verification error is less than 2%.

[0031] Furthermore, step (2) specifically includes the following steps:

[0032] Step (21): After modeling the workpiece, import it into the robot offline programming system, plan the additive path, generate the corresponding slice file and import it into the additive control system to generate the additive program; embed a constant temperature heating device under the base, use a fixture to assemble and fix the substrate on the base, preheat the substrate evenly, and use a tooling fixture to clamp the baffle at the welding gun.

[0033] Step (22): Model an N-layer large workpiece structure, 1≤N≤50. Using the heat source calibrated in step (1), simulate the deformation and mechanical behavior of the N-layer metal arc additive manufacturing process. Mark the cloud map area where the workpiece deformation exceeds 2mm into blocks, and denote the regions as S. i i = 1, 2, 3...;

[0034] Step (23): The control system uses the additive manufacturing robot arm to drive the welding torch to start the arc and perform additive manufacturing according to the processing path set in the additive manufacturing control system.

[0035] Step (24): After adding N layers, S i Artificial speckle and camera calibration were performed, and real-time measurement of DIC deformation cloud map data of the entire field of view of the speckle area was conducted. Areas with deformation exceeding 2mm were marked as S. j j = 1, 2, 3...;

[0036] Step (25): Use a local heat treatment system to treat S j Local heat treatment is performed, and strain changes in all marked speckle areas in the DIC system are observed until the deformation in the above areas is less than 0.25 mm. Step (22) is repeated, and then N+N additive manufacturing is performed. Before the N+N layer additive manufacturing is completed, the DIC continues to monitor the deformation of all speckle areas in real time. When the workpiece deformation cloud map data exceeds 2 mm, the additive manufacturing process is stopped. At this time, the number of newly deposited layers is M, M≤N. Simulation is performed on the M layer, and the cloud map area with deformation exceeding 2 mm is marked as S. k k = 1, 2, 3...; S k After regional speckle pattern analysis, DIC deformation monitoring was performed, and areas with deformation exceeding 2 mm were marked as S in the cloud map. m m = 1, 2, 3...; a local heat treatment system is used to eliminate the deformation of the original N layer and the marked Sm region of the new deposition layer;

[0037] Step (26): Repeat steps (22)-(25) to complete the full-field deformation measurement and local heat treatment of the arc additive meter-level workpiece, and finally obtain the arc additive workpiece.

[0038] Furthermore, in step (21), when the substrate is stainless steel, the preheating temperature is between 150°C and 350°C; when the substrate is aluminum alloy, the preheating temperature is between 100°C and 200°C; and when the substrate is titanium alloy, the preheating temperature is between 250°C and 300°C.

[0039] In step (24) when creating artificial speckle patterns, the white paint sprayed should cover the specimen. The diameter of the speckle should be 5 to 10 pixels. The actual field of view in the X-axis direction (mm) / number of pixels in the X-axis direction = actual size of a single pixel (mm).

[0040] A meter-sized workpiece is prepared using the method described above.

[0041] Compared with the prior art, the significant advantages of this invention are:

[0042] (1) An arc additive manufacturing shape control device based on DIC full-field deformation measurement has a reasonable structural design, is simple and highly applicable; Digital image correlation method has been widely used in many engineering fields, but there is little research on stress and strain detection in the arc additive manufacturing process; This invention uses DIC imaging technology to carry out deformation monitoring research, and can obtain information such as global displacement, deformation and strain cloud map of additive materials in real time. Compared with other detection environments, DIC strain monitoring in the arc additive manufacturing process is more difficult. Sparks, arc light, high-temperature airflow and dust in the additive manufacturing process seriously affect its measurement accuracy. This invention adopts the following scheme: For the irregular surface of the "wall" of molten metal accumulation, a high-power blue light source is introduced into the system to provide sufficient brightness and uniform lighting conditions to ensure that the feature points on the surface of the target object are clearly visible and to avoid interference or reflection problems of arc light; For the high-intensity magnetic radiation and high temperature problems in the additive manufacturing process, the scheme places the fixed bracket at 1.5m on the base and uses a lens with an appropriate focal length to keep the test system and the test area at a safe distance for observation. To address the overexposure effects caused by sparks and arc light, the proposed solution involves adding baffles to reduce their intensity, or replacing the system light source with a laser source of a specific wavelength to weaken the intensity of sparks and arc light. Appropriate wavelength filters are also used to resolve overexposure issues. Regarding the smoke and dust generated during the additive manufacturing process, fans and other ventilation devices are used to promptly remove smoke and dust, preventing DIC measurement errors or data loss. The fans are positioned at a suitable location (0.6m from the base) to eliminate image distortion caused by air thermal disturbance without affecting the sample cooling process. Before conducting DIC experiments, a speckle quality assessment is used to provide operators with a basis for judgment and corresponding improvement measures. The accuracy of the DIC system is calibrated and evaluated until the entire test area passes the evaluation before proceeding to the next stage of the experiment.

[0043] (2) Taking into account factors such as chemical composition, rigidity of the additive structure, additive method, and ambient temperature, a suitable preheating temperature is set in the constant temperature heating device. Specifically, when the substrate is stainless steel, the preheating temperature is between 150℃ and 350℃; when the substrate is aluminum alloy, the preheating temperature is between 100℃ and 200℃; and when the substrate is titanium alloy, the preheating temperature is between 250℃ and 300℃. Preheating slows down the cooling rate after additive manufacturing, which is beneficial for the escape of diffusing hydrogen from the weld metal, preventing hydrogen-induced cracking and reducing the temperature gradient between the additive region and the welded workpiece. This reduces additive stress and, on the other hand, lowers the additive strain rate and the constraint of the additive structure, which helps avoid additive cracking.

[0044] (3) The residual stress distribution of large additive workpieces at various stages can be predicted by simulation. For meter-sized large metal additive workpieces, in order to reduce the workload of calculation and improve the efficiency of simulation, segmented additive simulation is adopted. That is, each time the arc additive N layers (N=1, 2, 3...) are simulated, and the area with deformation exceeding 2mm is marked. After each N layers are added, the speckle pattern of the marked area in the simulation result is calibrated. Then, the strain of the marked area is monitored in real time using DIC equipment, instead of the overall deformation measurement of the entire additive structure. This can greatly reduce the difficulty of DIC image related calculation, reduce unnecessary data, and significantly reduce the calculation time, so as to quickly calculate the strain cloud map of the speckle area. This is conducive to timely and effective induction heat treatment, avoiding the continuous accumulation of residual stress during the additive process, thereby effectively controlling the stress and deformation of the additive component.

[0045] (4) By using a local heat treatment system to control the shape of areas with large deformation cloud data, and by using the DIC software to observe the changes in the deformation cloud of the marked speckle area, it is possible to achieve overall real-time monitoring and precise control of deformation or even cracking caused by excessive stress in the electric arc additive meter-scale metal workpiece during the forming process, and to scientifically control the temperature field and stress field to ensure the forming of the workpiece. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the method flow of the present invention.

[0047] Figure 2 The simulation steps are for electric arc additive manufacturing.

[0048] Figure 3 This is the procedure for measuring DIC deformation.

[0049] Figure 4 This is a schematic diagram of the robot additive manufacturing platform of the present invention.

[0050] Figure 5 The present invention relates to an arc additive induction heat treatment shaping device.

[0051] Figure 6 The present invention relates to an arc additive manufacturing flame heating and shaping device.

[0052] Figure 7 This is a schematic diagram of the full-field deformation measurement of the electric arc additive manufacturing (DIC) of the present invention.

[0053] Figure 8 Temperature field contour plot of an N-layer box-shaped structure produced by arc additive manufacturing (before cooling to room temperature).

[0054] Figure 9Temperature field contour plot of an N-layer box-shaped structure produced by arc additive manufacturing (cooled to room temperature)

[0055] Figure 10 Equivalent stress distribution cloud map of an N-layer box-type structure produced by electric arc additive manufacturing.

[0056] Figure 11 Mark the location of the DIC strain contour plot and the eyy data curve.

[0057] Figure 12 This is the main contour plot of the out-of-plane displacement of an N-layer box-type structure (arrows indicate overall displacement).

[0058] Figure 13 For the forming of the box-shaped structure

[0059] Attached image annotations:

[0060] 1-Additive power supply, 2-Additive robot arm, 3-Welding torch, 4-Wire feeder, 5-Shielding gas device, 6-Control cabinet, 7-Teach pendant, 8-Additive workpiece, 9-Baseboard, 10-Base, 11-Constant temperature heating device, 12-Induction coil, 13-Electromagnetic induction heating power supply, 14-Tooling fixture, 15-Baffle, 16-High-speed camera, 17-High-power blue LED light, 19-Calibration plate, 18-Computer workstation, 20-Fan, 21-Movable bracket, 22-Fixed bracket, 23-Infrared thermal imager device, 24-Flame burner, 25-Combustible gas cylinder. Detailed Implementation

[0061] The present invention will now be described in further detail with reference to the accompanying drawings.

[0062] This invention relates to an arc additive manufacturing shape control device and method based on DIC full-field deformation measurement. For large additive workpieces, to reduce computational workload and improve simulation efficiency, segmented additive manufacturing simulation is adopted. Specifically, simulation is performed on N layers of arc additive manufacturing (1≤N≤50) at a time to obtain the deformation cloud map of each N-layer workpiece. Areas with deformation exceeding 2mm are marked with S. i i = 1, 2, 3...; Arc additive manufacturing of N-layer workpieces and simultaneous real-time DIC full-field deformation measurement of all marked areas, using a local heat treatment system for all areas S with large deformation cloud map data. jLocal heat treatment is performed on (i, j = 1, 2, 3...), while the strain changes of all marked speckle areas in the global field of view of the DIC software are observed. Heating is stopped until the strain in the above areas is less than 0.25 mm. Then, N+N additive manufacturing is performed. Before the N+N layer additive manufacturing is completed, in order to prevent the heat accumulation during the arc additive manufacturing process from causing large deformation of the previously deposited layers, DIC continues to monitor the deformation of all speckle areas in real time. Furthermore, when the workpiece deformation cloud map data exceeds 2 mm, the additive manufacturing process is stopped. At this time, the number of new deposited layers is M (M≤N). Simulation is performed on the M layers, and the cloud map areas with deformation exceeding 2 mm are marked as S. k k = 1, 2, 3...; S k After regional speckle pattern analysis, DIC deformation monitoring was performed, and areas with deformation exceeding 2 mm were marked as S in the cloud map. m m = 1, 2, 3...; the labeling S for the deformation of the original N layer and the new sedimentary layer. m A localized heat treatment system is used to eliminate deformation in the affected area. The above steps are repeated to complete the additive manufacturing for each N layers, along with overall deformation measurement and localized heat treatment, ultimately yielding a well-formed arc-additive workpiece. The aim is to achieve real-time monitoring and precise control of deformation and even cracking caused by excessive stress during the forming process of large arc-additive workpieces due to alternating heating and cooling, and to scientifically control the temperature and stress fields to ensure proper part forming.

[0063] like Figures 4-6 As shown, an arc additive induction heat treatment shape control device based on DIC full-field strain measurement includes a robotic additive manufacturing platform, a constant temperature heating device 11, a local heat treatment system, an arc additive DIC full-field deformation measurement system, a computer workstation 18, and an infrared thermal imager device 23.

[0064] The robotic additive manufacturing platform includes: 1. Additive power supply; 2. Additive robot arm; 3. Additive gun; 4. Wire feeder; 5. Protective gas device; 6. Control cabinet and teach pendant; 7. Additive workpiece; 8. Substrate; 9. Base; 10, etc. (see...) Figure 4 );

[0065] The control cabinet regulates the additive manufacturing robot's robotic arm 2, wire feeder 4, protective gas device 5, and additive gun 3, etc.

[0066] The teach pendant 7 is a remote control used to memorize and store the mechanical movement behavior of the additive manufacturing robot arm 2. It can realize human-machine interaction. The additive manufacturing robot arm performs additive manufacturing under the human control of the teach pendant. After the single-layer additive manufacturing is completed, the control cabinet 6 controls the additive manufacturing robot arm to move upward to a safe position above the additive workpiece 8. The robot offline programming software is built into the computer workstation 18. The complete 3D model of the additive structure is imported. The software can automatically plan the optimal additive manufacturing path and generate the corresponding slice file. The slice file is then imported into the additive manufacturing control system to generate the additive manufacturing program.

[0067] The constant temperature heating device 11 provides uniform heating and has a built-in K-value temperature sensor, which can provide more convenient temperature control. It can operate normally within the range of 650℃. This heating device is used to assist in the uniform preheating of the substrate 9.

[0068] Local heat treatment systems include electromagnetic induction heating devices, flame heating devices, etc.

[0069] The electromagnetic induction heating device includes: an induction heating power supply 12, an induction coil 13, and a tooling fixture 14; (see...) Figure 5 )

[0070] The heating rate of the electromagnetic induction heating device can be adjusted and controlled within the range of 0℃ / s to 400℃ / s, and the power is adjustable from 0 to 120kW. The output power is sufficient to enable the additive workpiece within 8mm of the surface to reach 800 degrees Celsius in 3 to 5 seconds, and the maximum heating can reach 1200℃. It can uniformly heat various metal workpieces. The induction coil used is selected and adjusted according to the specific shape of the additive workpiece.

[0071] The flame heating device includes: a flamethrower 24 and a combustible gas cylinder 25. (See...) Figure 6 )

[0072] The arc additive manufacturing (AIC) full-field deformation measurement system includes: a baffle 15, two high-speed cameras 16, a high-power blue LED light 17, supporting DIC software and calibration plate 19, a fan 20, a movable support 21, and a fixed support device 22 (see...). Figure 6 );

[0073] The baffle 15, placed between the welding torch and the DIC equipment by means of a tooling fixture, can effectively reduce or avoid the impact of overexposure caused by sparks and arc light on the accuracy of global strain measurement of DIC.

[0074] The high-speed camera 16 connects to a computer with accompanying DIC software via USB or other interfaces. Its camera resolution is 5328(H) x 4608(V), 17Hz full-frame, and the lens focal length is 50mm. The high-speed camera captures speckle features at the pixel level. To address overexposure caused by sparks and arcs, the system light source can be replaced with a specific wavelength laser light source to reduce the intensity of sparks and arcs. Appropriate wavelength filters can also be used to resolve overexposure issues.

[0075] The high-power blue LED light 17 addresses the problem of irregular surfaces on the "wall" of molten metal accumulation. The high-power blue light source provides sufficient brightness and uniform lighting conditions to ensure that the feature points on the surface of the target object are clearly visible, avoiding interference or reflection problems caused by electric arc light.

[0076] With the accompanying DIC software, the cross-correlation or normalized cross-correlation function, as well as 3D digital image correlation algorithms such as correlation peak location and frequency domain correlation analysis, are used to perform real-time measurement of strain cloud map data for the entire field of view of all speckle regions in two-dimensional and three-dimensional space.

[0077] Calibration plate 19, the DIC calibration plate is a tool composed of black and white dots with highly precise dimensions and shapes. By placing the DIC calibration plate at the front and back positions of the additive workpiece and capturing images of the calibration plate using a high-speed camera, the DIC system can be calibrated to determine the pixel scale and distortion correction parameters of the DIC system. By measuring the pixel coordinates of feature points of known dimensions on the calibration plate in the image and combining this with the geometric information on the calibration plate, the camera's intrinsic parameters and distortion parameters can be established. In actual testing, the DIC system can use these calibration parameters to convert pixel coordinates into physical coordinates, thereby obtaining accurate displacement and deformation data;

[0078] Fan 20, placed at a suitable position 0.6m from the base, can remove smoke and dust in time, avoiding DIC measurement errors caused by changes in image resolution data and data loss caused by smoke and dust obstruction. At the same time, it can eliminate image distortion caused by air thermal disturbance and does not affect the cooling process of the sample.

[0079] The movable bracket 21 has steel balls embedded under the two high-speed cameras and high-power blue LED lights, which are mounted on the movable bracket via steel ball slide rails for easy position adjustment.

[0080] The fixed bracket 22 is placed 1.5m from the base and a lens with an appropriate focal length is used to keep the test system at a safe distance from the test area for observation, which can solve the problems of high-intensity magnetic radiation and high temperature in the additive manufacturing process.

[0081] The error of the DIC-based full-field strain measurement arc additive system meets the following conditions: strain resolution: 3D≤0.002%; 2D≤0.001%; ​​strain measurement system noise 3D≤0.001%; ​​3D displacement resolution≤0.001 pixels; full-field displacement error ≤1σ in pixels.

[0082] Computer workstation 18 is equipped with modules for modeling, mesh generation, and arc additive manufacturing simulation. The simulation uses the complete temperature field results as input to simulate the deformation and mechanical behavior of meter-scale metal additive workpieces during the overall arc additive manufacturing process.

[0083] The infrared thermal imager device 23 is fixed at a distance of 1.2m from the substrate, with a temperature measurement range of 0℃~1500℃. It is used to acquire the temperature of the additive workpiece in real time. At the same time, the temperature field simulation results obtained by the arc additive manufacturing simulation software are compared with the data recorded by the infrared thermal imager. The thermal cycle curve error is generated to verify the effectiveness of the heat source model. If the thermal cycle peak temperature error is less than 2%, it meets the test requirements. Otherwise, the heat source model parameters are modified until the verification is completed.

[0084] The technical solution to achieve the objective of this invention is as follows: a method for additive manufacturing using an arc additive manufacturing shape control device based on DIC full-field deformation measurement, comprising the following steps:

[0085] S1: Simulation of heat source model calibration

[0086] Step (11): After modeling the 50-layer straight wall body, import it into the robot offline programming software, plan the additive path, generate the corresponding slice file, and import it into the additive control system to generate the additive program;

[0087] Step (12): After the substrate is polished, it is fixed to the base. The electric arc additive DIC full-field deformation measurement system is built. The infrared thermal imager device is fixed and the angle is adjusted for real-time temperature measurement during the additive process.

[0088] Step (13): Conduct an arc additive pre-test, start the infrared thermal imager to measure the temperature of the additive component in real time, start the arc at one end of the welding torch, and add a straight wall body in a single layer on the substrate;

[0089] Step 1(4): Perform electric arc additive simulation on the straight wall body, compare the temperature field simulation results with the data recorded by the infrared thermal imager, plot the thermal cycle curve error diagram and modify the heat source model parameters until the verification error is less than 2%.

[0090] S2: Arc Additive Manufacturing and Deformation Control for Meter-Scale Workpieces

[0091] Step (21): After modeling the complete large workpiece, import it into the robot offline programming software, plan the additive path, generate the corresponding slice file, and import it into the additive control system to generate the additive program. A constant temperature heating device is embedded below the base. The new substrate is assembled and fixed on the base using a fixture, and the substrate is preheated evenly to a temperature of (200-400℃). A baffle is clamped at the welding gun using a tooling fixture.

[0092] Step (22): Model an N-layer large workpiece structure (1≤N≤50), use the heat source calibrated by S1 to simulate the deformation and mechanical behavior of the N-layer metal arc additive manufacturing process, and mark the cloud map area where the workpiece deformation exceeds 2mm into blocks, denoted as S. i i = 1, 2, 3...;

[0093] Step (23): The control system uses the additive manufacturing robot arm to drive the welding torch to start the arc and perform additive manufacturing according to the processing path set in the additive manufacturing control system.

[0094] Step (24): After adding N layers, S i Artificial speckle and camera calibration were performed, and real-time measurement of DIC deformation cloud map data of the entire field of view of the speckle area was conducted. Areas with deformation exceeding 2mm were marked as S. j j = 1, 2, 3...;

[0095] Step (25): Use a local heat treatment system to treat S j Local heat treatment is performed, and the strain changes of all marked speckle areas in the DIC software are observed until the deformation of the above areas is less than 0.25 mm. Step (22) is repeated, and then N+N additive manufacturing is performed. Before the N+N layer additive manufacturing is completed, in order to prevent the heat accumulation during the arc additive manufacturing process from causing large deformation of the previously deposited layer, the DIC continues to monitor the deformation of all speckle areas in real time. Furthermore, when the workpiece deformation cloud map data exceeds 2 mm, the additive manufacturing process is stopped. At this time, the number of new deposited layers is M (M≤N). The M layer is simulated, and the cloud map area with deformation exceeding 2 mm is marked as S. k k = 1, 2, 3...; S k After regional speckle pattern analysis, DIC deformation monitoring was performed, and areas with deformation exceeding 2 mm were marked as S in the cloud map. m m = 1, 2, 3...; a local heat treatment system is used to eliminate deformation in the deformed areas of the original N layer and the marked Sm areas of the new deposition layer.

[0096] Step (26): Repeat steps (22), (23), (24), and (25) in S2 to complete the full-field deformation measurement and electromagnetic induction heat treatment of the arc additive meter-scale workpiece, and finally obtain a well-formed arc additive workpiece.

[0097] During arc additive manufacturing, rapid temperature changes cause non-uniform plastic deformation and microstructural changes in the workpiece material due to thermal expansion and contraction, resulting in significant stress. When these deformations and stresses accumulate to a certain level, they may lead to defects such as delamination and cracks in the workpiece. Therefore, monitoring and controlling deformation during arc additive manufacturing has become crucial for improving the quality and stability of finished products.

[0098] DIC (Discrete Injection) is an optical measurement technique that creates a speckle pattern on the surface of the object being measured. A camera captures the movement of the speckle features, and 3D digital image correlation algorithms, such as cross-correlation or normalized cross-correlation functions, correlation peak localization, and frequency domain correlation analysis, are used to calculate data on morphology, displacement, and strain from all perspectives in two-dimensional and three-dimensional space. In arc additive manufacturing, precise control requires real-time monitoring and control of material deformation during the additive process. High-precision displacement and deformation measurements at each stage of the additive process allow for real-time understanding of material deformation, enabling better control of the additive process and ensuring that the additively produced product meets design requirements.

[0099] Compared to other environments, DIC strain monitoring during arc additive manufacturing faces greater challenges. This is because factors such as sparks, arc light, high-temperature airflow, and dust during the additive manufacturing process can severely affect the measurement accuracy of DIC. This invention proposes the following solutions to address these measurement accuracy issues:

[0100] ① To address the issue of irregular surfaces where molten metal accumulates, we employed a high-power blue light source to provide sufficient brightness and uniform illumination. This ensures that feature points on the target object's surface are clearly visible, avoiding interference or reflection issues caused by electric arc light.

[0101] ② To address the issues of high-intensity magnetic radiation and high temperature during the additive manufacturing process, we placed the fixed bracket on a base 1.5 meters away from the test area and used a lens with an appropriate focal length to observe the test system and maintain a safe distance from the test area.

[0102] ③ To address the overexposure caused by sparks and arc light, we added damping baffles or replaced the system light source with a laser light source of a specific wavelength to reduce the intensity of sparks and arc light. We also equipped the system with filters of the corresponding wavelengths to resolve overexposure issues.

[0103] ④ To address the issue of smoke and dust generated during the additive manufacturing process, we use fans and other air supply devices to promptly remove the smoke and dust, avoiding DIC measurement errors caused by smoke and dust, as well as data loss due to smoke and dust obstruction. Simultaneously, we chose to place the fan at a suitable location 0.6 meters away from the base, which eliminates image distortion caused by air thermal disturbances without affecting the sample cooling process.

[0104] ⑤ Before conducting the DIC experiment, use speckle quality assessment to provide operators with a basis for judgment and take corresponding improvement measures. The accuracy of the DIC system should be calibrated and evaluated until the entire test area passes the evaluation before proceeding to the next step of the experiment.

[0105] The above solutions can solve the measurement accuracy problem faced by DIC deformation monitoring in the electric arc additive manufacturing process, thereby improving the accuracy and reliability of the experiment.

[0106] Simulation can be used to predict the residual stress distribution at various stages of additive manufacturing of large workpieces. For meter-scale large additive workpieces, to reduce computational workload and improve simulation efficiency, this invention uses segmented additive manufacturing simulation to obtain deformation cloud maps for each N layers of the workpiece, and marks areas exceeding 2mm. Then, while manufacturing each N layers of the workpiece, DIC technology is used to perform real-time full-field deformation measurement of all marked areas, rather than a global measurement of the entire additive structure. This greatly reduces the computational difficulty of DIC images, reduces unnecessary data, and significantly shortens computation time, enabling rapid calculation of strain cloud maps in speckle areas. This facilitates timely and effective local heat treatment, preventing the continuous accumulation of residual stress during additive manufacturing, and thus effectively controlling the stress and deformation of the additive component.

[0107] For areas with large deformation cloud map data, a local heat treatment system is used for shape control. Simultaneously, the deformation changes of all marked speckle areas within the global field of view in the DIC software are observed. Heating is stopped when the strain change in these areas stops below 0.25 mm. After completing additive manufacturing for every N layers and full-field deformation measurement and electromagnetic induction heat treatment, the deformation of all speckle areas continues to be monitored in real time using the DIC equipment. If the workpiece's deformation cloud map data exceeds 2 mm, i.e., exceeds the preset threshold, the additive manufacturing process is stopped, and a local heat treatment system is used to control the deformation. By repeating the above steps, a well-formed arc additive workpiece can finally be obtained. This method aims to achieve overall real-time monitoring and precise control of deformation and even cracking caused by excessive stress during the forming process of meter-scale metal workpieces produced by arc additive manufacturing. It scientifically controls the temperature and stress fields, eliminates metallurgical defects, improves microstructure, and ensures part forming.

[0108] To further verify the effect, multiple sets of comparative experiments were conducted, with parameters remaining consistent in each experimental case. The following example illustrates this: The specific steps of the implementation plan are as follows:

[0109] Step (1): Using CMT arc additive manufacturing technology, 50 layers of high-nitrogen steel straight-walled workpieces and box-type structures are additively manufactured on a 316L stainless steel substrate with a geometric size of 400mm*400mm*10mm using HNS6T high-nitrogen steel wire with a diameter of 1.2mm. The geometric model of the additive workpiece is divided into sections, layers, and slices, and imported into the robot offline programming software to generate the corresponding additive path and program. The shielding gas is a ternary mixture of 93.5%Ar+5%N2+1.5%O2, with a gas flow rate of 20L / min, a wire feed speed of 6.7m / min, an arc travel speed of 4mm / s, and a voltage of 15mm from the contact tip to the substrate. The wire extension is 12mm, the arc length correction and pulse correction are 0, the arc starting current accounts for 80%, the arc starting current time is 0.3s, the arc starting transition time is 0.4s, the arc extinguishing current accounts for 60%, the arc extinguishing current time is 1.2s, and the arc extinguishing transition time is 0.6s.

[0110] Step (2): Grind the substrate surface to remove the oxide film and clean the substrate surface with acetone; use a fixture to assemble and fix the substrate on the workbench; fix the infrared thermal imager device 1.2m away from the substrate and adjust its position for real-time temperature measurement during the additive manufacturing process. A movable bracket is embedded in the fixed bracket device and placed 1.5m from the base. Two high-speed cameras and a high-power blue LED light are installed and fixed on the movable bracket. The high-speed cameras are connected to the matching DIC software computer via USB or other interfaces. Air supply devices such as fans are placed 0.6m away from the base.

[0111] Step (3): After starting and calibrating the infrared thermal imager, the welding torch starts to ignite the arc from one end and adds 50 layers of metal on the 316L stainless steel substrate using a single-layer reciprocating additive arc. The infrared thermal imager records the temperature changes during the additive process in real time.

[0112] Step (4): Simulate the 50-layer metal additive manufacturing process using electric arc additive manufacturing. Compare the temperature field simulation results with the data recorded by the infrared thermal imager. Create a thermal cycling curve error diagram to verify the double ellipsoidal heat source model. When the error exceeds 1.8%, the heat source model parameters are as follows: a is 8.72mm, b is 6.34mm, C f It is 4.36mm, C r It is 17.44 mm long, with a thermal input parameter η of 0.75, and F... f =0.6, F r =1.4, voltage U is 16.8V, current I is 160A, v is the additive speed;

[0113] The power density distribution in the first half of the ellipsoid is as follows:

[0114]

[0115] The power density distribution in the latter half of the ellipsoid is as follows:

[0116]

[0117] Step (5): Embed a constant temperature heating device under the substrate. Use a fixture on the worktable to reassemble and fix the new substrate, control the heating device to preheat the substrate evenly to 250°C, and use a tooling fixture to clamp a baffle at the welding gun;

[0118] Step (6): Model a 30-layer box-shaped workpiece structure in SolidWorks; then use HyperMesh to mesh the workpiece, define material properties, set boundary conditions, and use Simufact Welding simulation software to simulate the deformation and mechanical behavior of the additive workpiece during the temperature change process of N-layer metal integral arc additive manufacturing (simulation temperature field results and equivalent stress are available in...). Figure 8 , Figure 9 , Figure 10 For areas in the cloud map where the workpiece deformation exceeds 2mm during the arc additive manufacturing process, the areas are divided and marked as S. i i = 1, 2, 3...;

[0119] Step (7): Call the program and control system to use the additive manufacturing robot arm to drive the welding gun to start the arc and perform additive manufacturing according to the pre-set processing path of the box-shaped workpiece;

[0120] Step (8): After adding material to N layers, N = 1, 2, 3...; use the speckle tool to create artificial speckles in the areas of workpiece deformation cloud map data marked in the simulation software results that exceed 2mm, and use a calibration plate to calibrate the camera. After calibration, the DIC deformation measurement system error is: strain resolution: 3D is 0.0012%; 2D is 0.0006%; strain measurement system noise 3D is 0.0006%; 3D displacement resolution is 0.0004 pixels; the full-field displacement error is 0.5σ in pixels. The DIC equipment measures the deformation cloud map data of the entire field of view of all speckle areas in real time, and marks the areas with deformation exceeding 2mm as S. j j = 1, 2, 3...;

[0121] Step (9): Use an electromagnetic induction heating device to heat all areas S with large deformations within the entire field of view of the DIC. ij Electromagnetic induction heat treatment was performed, and the deformation changes of all marked speckle regions in the DIC software were observed (DIC deformation cloud map e). yy Data curves are shown Figure 11Once the maximum deformation is less than 0.25mm, electromagnetic induction heating is stopped. Before the next stage of the additive manufacturing process is completed, DIC continues to monitor the deformation of all speckle areas. Furthermore, when the workpiece deformation cloud map data exceeds 2mm, the additive manufacturing process is stopped, and induction heating is used to control the deformation. (See the main cloud map of the out-of-plane displacement.) Figure 12 )

[0122] Step (10): Repeat steps (6), (7), (8), and (9) to complete the full-field deformation measurement and electromagnetic induction heat treatment of the large workpiece produced by arc additive manufacturing. The surface of the straight-arm structure workpiece prepared by the arc additive manufacturing process is smooth and flat, with regular spread between layers. No defects such as deformation, cracking, or slag inclusions are observed. No molten pool flow occurs at the offset ends (see forming condition). Figure 13 ).

Claims

1. An arc additive manufacturing shaping method based on an arc additive manufacturing shaping device using DIC full-field deformation measurement, characterized in that, The arc additive manufacturing shaping device based on DIC full-field deformation measurement includes an arc additive manufacturing DIC full-field deformation measurement system, a computer workstation, a constant temperature preheating device, an infrared thermal imager, a local heat treatment system, and a robotic additive manufacturing platform. The arc additive manufacturing DIC full-field deformation measurement system is used for real-time measurement of the deformation of the additive part. The computer workstation is equipped with an arc additive manufacturing simulation module and the DIC system. In the arc additive manufacturing simulation module, the temperature field simulation results are compared with the data recorded by the infrared thermal imager to generate a thermal cycling curve error verification of the effectiveness of the heat source model. Using the acquired complete temperature field simulation results as input, the simulation is used to simulate the deformation and mechanical behavior of the additive workpiece during the overall arc additive manufacturing temperature change process. The constant temperature heating device is used to assist in uniform preheating of the substrate, and the infrared thermal imager is used to acquire the temperature of the additive workpiece in real time. The local heat treatment system heats the deformed part of the workpiece according to the measurement results of the arc additive manufacturing DIC full-field deformation measurement system, and the robotic additive manufacturing platform is used for the additive manufacturing of the workpiece. The method includes the following steps: Step (1): Use simulation to obtain the deformation cloud map of the N-layer of the arc additive manufacturing process, and mark the areas with deformation exceeding 2 mm as S. i i = 1, 2, ...; Step (2): Arc additive manufacturing of N layers of workpiece and marking of area S i DIC monitoring was performed on areas with deformation exceeding 2mm. j Local heat treatment is performed for j=1, 2..., and the marked speckle region S in the DIC is observed simultaneously. j The deformation is varied until it is less than 0.25 mm, and then the next N layers of additive manufacturing are carried out. Before the Nth layer of additive manufacturing is completed, maintain DIC for all speckle regions S. i and S j Real-time monitoring of deformation; when the deformation of the monitoring cloud map exceeds 2 mm, additive manufacturing is stopped, and local heat treatment is used to eliminate the deformation of the original N layer and the speckle marking area of ​​the new deposition layer. Repeat the above steps to complete the arc additive manufacturing process; The electric arc additive manufacturing (AIC) full-field deformation measurement system includes two high-speed cameras, high-power blue LED lights, a matching DIC system, an air supply device, a baffle, a movable support, and a fixed support device. Two high-speed cameras and a high-power blue LED light are mounted on a movable bracket via ball bearing slide rails. The high-speed cameras are connected to the computer of the matching DIC system. The movable bracket is embedded in the fixed bracket device. The air supply device is used to remove the dust generated during the additive manufacturing process. The error of the full-field deformation measurement system of electric arc additive manufacturing (DIC) meets the following conditions: strain resolution: 3D ≤ 0.002%; 2D ≤ 0.001%; ​​strain measurement system noise 3D ≤ 0.001%; ​​3D displacement resolution ≤ 0.001 pixels; full-field displacement error ≤ 1σ in pixels.

2. The method according to claim 1, characterized in that, The constant temperature preheating device has a built-in K-value temperature sensor and can operate normally within a range of 650℃. The infrared thermal imager has a temperature measurement range of 0℃ to 1500℃. The local heat treatment system is one or both of electromagnetic induction heating devices and flame heating devices.

3. The method according to claim 2, characterized in that, The heating rate of the electromagnetic induction heating device is adjustable from 0℃ / s to 400℃ / s, and the power is adjustable from 0 to 120 kW. The output power can enable the additive workpiece within 8 mm of the surface to reach 800 degrees Celsius in 3 to 5 seconds, and the maximum heating is up to 1200℃. The induction coil used in the electromagnetic induction heating device is selected and adjusted according to the specific shape of the additive workpiece. The flame heating device includes a flamethrower and a combustible gas storage cylinder.

4. The method according to claim 3, characterized in that, The robotic additive manufacturing platform includes: an additive power supply, an additive robot arm, a welding torch, a robot offline programming system, a wire feeder, a protective gas device, and a control system for controlling the additive motion trajectory of the additive robot arm.

5. The method according to claim 4, characterized in that, Step (1) specifically includes the following steps: Step (11): After modeling the multi-layer straight wall body, import it into the robot offline system, plan the additive path, generate the slice file, and import it into the additive control system to generate the additive program; Step (12): After the substrate is polished, it is fixed to the base. The arc additive DIC full-field deformation measurement system is built. The infrared thermal imager device is fixed and the angle is adjusted for real-time temperature measurement during the additive process. Step (13): Conduct an arc additive pre-test, start the infrared thermal imager device to measure the temperature of the additive component in real time, start the arc at one end of the welding torch, and add a straight wall body in a single layer on the substrate; Step (14): Perform electric arc additive simulation on the straight wall body, compare the temperature field simulation results with the data recorded by the infrared thermal imager, plot the thermal cycle curve error diagram and modify the heat source model parameters until the verification error is less than 2%.

6. The method according to claim 5, characterized in that, Step (2) specifically includes the following steps: Step (21): After modeling the workpiece, import it into the robot offline programming system, plan the additive path, generate the corresponding slice file and import it into the additive control system to generate the additive program; embed a constant temperature heating device under the base, use a fixture to assemble and fix the substrate on the base, preheat the substrate evenly, and use a tooling fixture to clamp the baffle at the welding gun. Step (22): Model an N-layer large workpiece structure, 1≤N≤50. Using the heat source calibrated in step (1), simulate the deformation and mechanical behavior of the N-layer metal arc additive manufacturing process. Mark the cloud map area where the workpiece deformation exceeds 2 mm into blocks, and denote the regions as S. i i = 1, 2, 3...; Step (23): The control system uses the additive manufacturing robot arm to drive the welding torch to start the arc and perform additive manufacturing according to the processing path set in the additive manufacturing control system. Step (24): After adding N layers, S i Artificial speckle and camera calibration were performed, and real-time measurement of DIC deformation cloud map data of the entire field of view of the speckle area was conducted. Areas with deformation exceeding 2 mm were marked as S. j j = 1, 2, 3...; Step (25): Use a local heat treatment system to treat S j Local heat treatment is performed, and strain changes in all marked speckle areas in the DIC system are observed until the deformation in the above areas is less than 0.25 mm. Step (22) is repeated, and then N+N additive manufacturing is performed. Before the N+N layer additive manufacturing is completed, the DIC continues to monitor the deformation of all speckle areas in real time. When the workpiece deformation cloud map data exceeds 2 mm, the additive manufacturing process is stopped. At this time, the number of newly deposited layers is M, M≤N. Simulation is performed on the M layer, and the cloud map area with deformation exceeding 2 mm is marked as S. k k=1, 2, 3...; S k After regional speckle pattern analysis, DIC deformation monitoring was performed, and areas with deformation exceeding 2 mm in the cloud map were marked as S. m m=1, 2, 3...; a local heat treatment system is used to eliminate deformation in the original N layer and the marked Sm region of the newly deposited layer; Step (26): Repeat steps (22)-(25) to complete the full-field deformation measurement and local heat treatment of the arc additive meter-level workpiece, and finally obtain the arc additive workpiece.

7. The method according to claim 6, characterized in that, In step (21), when the substrate is stainless steel, the preheating temperature is between 150°C and 350°C; when the substrate is aluminum alloy, the preheating temperature is between 100°C and 200°C; and when the substrate is titanium alloy, the preheating temperature is between 250°C and 300°C. In step (24) when creating artificial speckle patterns, the white paint sprayed should cover the specimen. The diameter of the speckle should be 5 to 10 pixels. The actual field of view in the X-axis direction (mm) / number of pixels in the X-axis direction = actual size of a single pixel (mm).

8. A meter-scale workpiece, characterized in that, Prepared using the method described in any one of claims 1-7.

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