Enclosed filter protection device for dic speckles for steel sheet forming tests

Abstract

The utility model provides a DIC speckle's closed type filter protection device for steel plate forming test relates to DIC speckle making technical field, include: spray room box body, negative pressure fan system, hot plate, magnetic attraction fixed module and central controller, realize toxic substance zero leakage, temperature fluctuation control and instant speckle making, clean steel plate surface and magnetic attraction fixed, through negative pressure fan system establishes - 50Pa negative pressure environment, adopts glove operation hole to carry out white primer and black speckle spraying, gradient drying ensures that the paint film adhesion reaches 5B level, through VOC sensor and particulate matter sensor real -time monitoring, when VOC is less than or equal to 1mg / m 3, automatically releases the case door safety lock. The utility model improves operation safety, speckle uniformity and forming test data precision significantly, improves operation efficiency.

Description

Technical Field

[0001] This utility model relates to the field of DIC speckle fabrication technology, and more particularly to a closed-loop filtration and protection device for DIC speckle in steel plate forming tests. Background Technology

[0002] In steel plate forming tests, digital image correlation (DIC) uses speckle patterns as optical markers to measure the strain distribution across the entire steel plate with high precision. However, existing DIC speckle fabrication methods have significant drawbacks, severely limiting the reliability and safety of the tests.

[0003] Traditional DIC speckle formation processes, which involve manual spraying in an open environment, suffer from significant technical drawbacks. During spraying, volatile organic compound (VOC) concentrations can reach 112 mg / m³ (the national standard limit is 10 mg / m³). Benzene compounds pose occupational health risks through inhalation or skin contact, and the need for respirators significantly reduces operational convenience. More critically, manual spraying causes a sudden temperature drop of over 15°C on the steel sheet surface, altering the material's strain-hardening behavior. Airflow-induced speckle drift exceeds 20 μm, directly causing errors in strain calculations in the necking region. Existing protective solutions cannot address the integration requirements of speckle formation and forming equipment in high-temperature environments. Mismatches in the thermal expansion coefficients of the paint film lead to speckle layer detachment during high-temperature testing, and speckle diameter deviations exceeding 40% occur with traditional methods. Insufficient contrast causes mismatches in the DIC system. These technical bottlenecks result in persistently high error rates in forming limit curve (FLC) testing, hindering the development of precision stamping processes for automotive steel sheets. The aforementioned technical deficiencies directly result in high dispersion and poor repeatability of forming test data, making it impossible to provide a reliable basis for material process optimization. Therefore, there is an urgent need for an integrated solution that can simultaneously achieve zero leakage of toxic substances, precise temperature field control, and high-adhesion speckle preparation, in order to overcome the limitations of existing technologies in high-precision forming analysis. Utility Model Content

[0004] To address the aforementioned technical problems, a closed-loop method for fabricating DIC speckle patterns for steel plate forming tests and a filtration and protection device are provided. This invention achieves zero toxicity leakage and high-precision speckle preparation through a negative pressure environment, gradient drying, and safety monitoring.

[0005] To achieve the above objectives, this utility model provides a closed-loop filtration and protection device for DIC speckle in steel plate forming tests, which is applied to the closed-loop safety manufacturing method of DIC speckle in steel plate forming tests. The device includes: a spray booth housing with a negative pressure fan system installed on the top, and a glass observation window and a door installed on the front of the spray booth housing. The side wall of the spray booth is equipped with two glove operation holes, and gloves are connected to the inside of the glove operation holes; a spray can bracket and a VOC sensor are installed on the lower side of the glass observation window inside the spray booth. The spray booth is equipped with lamp tubes on the inside of the top of the booth, and heating plates and temperature sensors are also installed on the side walls of the booth. The bottom of the spray booth is a workbench, on which a magnetic chuck is installed to fix the steel plate sample by magnetic attraction.

[0006] Furthermore, the lamp tube includes a UV germicidal lamp and an LED for illumination.

[0007] Furthermore, the cabinet door is equipped with an electronic safety lock, which is linked to a VOC sensor and controls the door to unlock based on the air quality data inside the cabinet.

[0008] Furthermore, the spray booth enclosure achieves compression sealing of the door through a sealing strip, and the negative pressure fan system continuously maintains an air pressure environment of -50~-60Pa to prevent harmful gases from leaking out.

[0009] Furthermore, the spray can bracket is used to fix the self-spraying paint can, and the operator completes the spraying operation on the steel plate sample through the glove operating hole.

[0010] This utility model also provides a closed-loop safety manufacturing method for DIC speckle patterns used in steel plate forming tests, applicable to the aforementioned closed-loop filtration and protection device for DIC speckle patterns used in steel plate forming tests, comprising the following steps: S1. Sample preparation and fixing: Wipe the surface of the steel plate with acetone to remove oil stains, and fix the steel plate firmly on the workbench of the protective device using a magnetic chuck. S2. Establish a closed negative pressure environment: Close the protective device door and ensure that the sealing strip is tightly compressed. Start the negative pressure fan system to stabilize the air pressure inside the chamber at -50~-60Pa. At the same time, turn on the UV sterilization lamp and LED lighting inside the chamber. S3. Spraying white primer: The operator inserts his hands into the glove operating holes through the glove holes and uses a white self-spraying paint can to spray two coats evenly on the steel plate surface to form a uniform white background layer. S4. Spraying black speckles: Replace the water-based black spray paint can and spray a coat evenly on the steel plate surface to form black speckles. S5. Gradient drying and curing: Start the stepped heating and drying system and perform temperature gradient drying at 80℃ / 10 minutes, 120℃ / 5 minutes, and 60℃ / 5 minutes in sequence according to the program. S6. Safety monitoring and sample removal: The air quality inside the chamber is monitored in real time by a VOC sensor. When the VOC concentration is ≤1mg / m³, the central controller releases the electronic safety lock on the chamber door, and the operator removes the sample. S7. Forming test: The prepared specimen is placed in the stamping die of the forming test machine for forming test. The DIC system captures the strain distribution in the whole field.

[0011] Furthermore, in step S3, the white spray paint can is sprayed at a uniform speed at a distance of 25-35m from the surface of the steel plate.

[0012] Furthermore, in step S4, the black spray paint can is sprayed at a uniform speed at a distance of 25-35cm from the surface of the steel plate.

[0013] Furthermore, in the S5 gradient drying and curing process, the orange peel effect of the paint film is eliminated at the 80°C stage, the paint film is fully cured at the 120°C stage, and the internal stress is eliminated by slow cooling at the 60°C stage.

[0014] By adopting the above technical solution, this utility model has the following advantages compared with the prior art: 1. The closed-loop manufacturing method and filtration protection device for DIC speckle in steel plate forming test provided by this utility model, through a closed negative pressure system and a self-filtration protection device, controls the concentration of volatile organic compounds (VOCs) of benzene series compounds to ≤1mg / m³ during the spraying process, prevents leakage of toxic substances, and eliminates the need for operators to wear gas masks, significantly reducing occupational health risks.

[0015] 2. The closed-loop manufacturing method and filtration protection device for DIC speckle patterns used in steel plate forming tests provided by this utility model, with a stepped drying process, enables the paint film adhesion to reach the highest level 5B (4B in the traditional method), the speckle diameter uniformity to reach 0.3mm±0.02mm, the contrast ratio to be improved to 87%, and ensures that the strain measurement error of the DIC system is ≤0.5% across the entire field.

[0016] 3. The closed-loop manufacturing method and filtration protection device for DIC speckle pattern in steel plate forming test provided by this utility model are integrated to achieve full automation of the "spraying-drying-sampling" process, significantly saving time. The device is integrated next to the forming equipment, supports instant speckle pattern production of high-temperature steel plates, shortens the preparation time for forming test, and significantly improves R&D and production efficiency. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the closed-loop filter protection device for DIC speckle in steel plate forming tests according to the present invention. Figure 2 This is a flowchart of the closed-loop fabrication method for DIC speckle patterns used in steel plate forming tests according to this utility model; Figure 3 This is the forming limit diagram of Example 1 of the closed-loop manufacturing method and filter protection device for DIC speckle pattern used in steel plate forming tests; Figure 4 This is the forming limit diagram of Example 2 of the closed-loop manufacturing method and filter protection device for DIC speckle pattern used in steel plate forming tests; Figure 5 This is the forming limit diagram of Example 3 of the closed-loop manufacturing method and filter protection device for DIC speckle pattern used in steel plate forming tests; Figure 6 This is a flowchart illustrating the closed-loop manufacturing method and filtration protection device for DIC speckle patterns used in steel plate forming tests, as well as the linkage between the VOC concentration sensor and the chamber door.

[0019] In the diagram: 1. Spray booth housing; 2. Glass observation window; 3. Negative pressure fan system; 4. Glove operation port; 5. Glove; 6. Lamp tube; 7. Spray can support; 8. Heating plate; 9. Temperature sensor; 10. Magnetic chuck; 11. VOC sensor. Detailed Implementation

[0020] It should be noted that, where there is no conflict, the embodiments and features in the embodiments of this utility model can be combined with each other. The present utility model will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this utility model or its application or use. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0024] In the description of this utility model, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this utility model and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this utility model. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0025] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0026] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this utility model.

[0027] like Figure 1 As shown, this utility model provides a closed-loop filtration and protection device for DIC speckle in steel plate forming tests, which is applied to the above-mentioned closed-loop safety manufacturing method for DIC speckle in steel plate forming tests. It includes: a spray chamber 1, which is equipped with a negative pressure fan system 3 on its top, a glass observation window 2 and a door on the front of the spray chamber 1, a sealing strip at the connection between the glass observation window 2 and the door and the spray chamber 1, and an electronic safety lock on the door, which is linked with a VOC sensor 11 and controls the door to unlock according to the air quality data inside the chamber. Two glove operation holes 4 are provided on the side wall of the spray booth 1, and a glove 5 is connected to the inside of the glove operation holes 4. A spray can bracket 7 and a VOC sensor 11 are provided on the lower side of the glass observation window 2 inside the spray booth 1. The spray can bracket is used to fix the self-spraying paint can, and the VOC sensor 11 monitors the air quality inside the spray booth 1 in real time. The spray booth 1 is equipped with a lamp tube 6 on the inner side of the top. The lamp tube 6 includes a UV germicidal lamp and an LED for lighting. The side wall of the spray booth 1 is also equipped with a heating plate 8 and a temperature sensor 9. The bottom of the spray booth 1 is a workbench, on which a magnetic chuck 10 is installed to fix the steel plate sample by magnetic attraction.

[0028] Furthermore, the spray booth 1 achieves compression sealing of the door through a sealing strip, and the negative pressure fan system 3 continuously maintains an air pressure environment of -50~-60Pa to prevent harmful gases from leaking out.

[0029] like Figure 2 As shown, this utility model also provides a closed-loop fabrication method for DIC speckle patterns used in steel plate forming tests, comprising the following steps: S1. Sample preparation and fixing: The operator first wipes the surface of the steel plate with acetone or alcohol to remove oil stains. Then, the treated steel plate is fixed by the magnetic suction cup 10 on the workbench of the protective device to ensure that the steel plate does not shift during the subsequent spraying process. S2. Establish a closed negative pressure environment: Close the protective device door and ensure the sealing strip is tightly compressed. Start the negative pressure fan system 3 to stabilize the air pressure inside the chamber at -50~-60Pa. This negative pressure environment ensures that harmful gases will not leak out. At the same time, the UV germicidal lamps and LED lighting inside the chamber will automatically turn on, providing a sterile operating environment and sufficient lighting conditions. S3. Spraying white primer: The operator inserts both hands into the glove operating holes 4 on the side wall of the spray booth 1 and operates through gloves 5. Using a white spray paint can, at a distance of approximately 25-35cm from the steel plate surface, moves the arm at a uniform speed to apply two thin coats, forming a uniform white background layer. After spraying, return the paint can to the spray can holder; S4. Spraying Black Spots: The operator replaces the can with a water-based black spray paint can and, at a distance of approximately 25-35cm from the steel plate surface, moves the arm at a uniform speed to apply a thin coat of paint, forming black spots. After spraying, return the paint can to the spray can holder. S5. Gradient Drying and Curing: Start the stepped heating and drying system and perform the following temperature gradient drying according to the program: 80℃ / 10 minutes: Allow the paint film to flow and level fully to avoid orange peel effect; 120℃ / 5 minutes: Allows the paint film to fully cure and achieve optimal mechanical properties. 60℃ / 5 minutes: Slowly cool down to eliminate internal stress and prevent the paint film from cracking; S6. Safety monitoring and sample removal: (e.g.) Figure 6 As shown, the VOC sensor 11 of the spray booth 1 monitors the air quality inside the booth in real time; When the VOC concentration is ≤1mg / m³, the electronic safety lock on the chamber door is released and a green signal light is emitted. The operator then opens the chamber door and removes the steel plate sample. When the VOC concentration is >1mg / m³, the negative pressure fan system 3 increases the fan power and extends the drying time until the VOC concentration is ≤1mg / m³. S7. Forming test: The prepared specimen is placed in the stamping die of the forming test machine for forming test. The DIC system captures the strain distribution in the whole field.

[0030] Furthermore, such as Figure 6 As shown, during the spraying process, when the VOC concentration is >28mg / m³, the negative pressure fan system 3 increases the fan power and strengthens filtration, and the VOC concentration continues to decrease in a short period of time.

[0031] Example 1 The tested steel plate is QP980 steel with a thickness of 1.6mm; Test equipment: the self-filtering protection device described in this utility model, handheld spray cans (matte white primer, matte black speckled paint), molding test machine and DIC system (2×2 megapixel camera); 1) Safety and environmental indicators: Background VOC concentration in the spraying chamber before spraying: 0.05 mg / m³.

[0032] During the spraying process, the peak VOC concentration was 28 mg / m³. The negative pressure fan system 3 automatically triggered the negative pressure fan to speed up and enhance filtration. The peak concentration began to decrease continuously within 10 seconds. After the VOC concentration dropped to 20 mg / m³, the accelerated filtration stopped.

[0033] After the spraying was completed and a short period of purification was carried out, the VOC concentration dropped to 0.8 mg / m³, which is far below the safety limit of 10 mg / m³ specified in the Chinese National Occupational Health Standard GBZ2.1-2019.

[0034] Once the concentration reaches the standard, the safety lock on the box door automatically releases, and the operator removes the steel plate sample.

[0035] 2) Speckle quality indicators: Speckle diameter: average diameter 302μm, standard deviation ±8μm, indicating excellent uniformity of speckle size.

[0036] Speckle density: approximately 55%, which is within the ideal range of 40%-60% for DIC analysis.

[0037] Contrast ratio: With a white background grayscale value of 225 and a black spot grayscale value of 32, the calculated contrast ratio is as high as 87%, ensuring high contrast and clarity for DIC software image recognition.

[0038] Adhesion: Performed according to ASTM D3359 standard, the adhesion reaches the highest 5B level, with completely smooth edges and no squares falling off.

[0039] 3) Molding test and DIC analysis results: The prepared specimens were subjected to a cold stamping simulation test on a sheet metal forming testing machine. After experiencing a complex strain path, the speckle pattern showed no discoloration, cracking, or flaking, maintaining a high degree of integrity.

[0040] The DIC system successfully captured the full-field strain distribution of the steel plate during the forming process. The generated maximum principal strain cloud map had clear texture and smooth transition, without any mismatch, jump points, or data loss caused by speckle quality.

[0041] like Figure 3 As shown, the calculated forming limit curve (FLC) matches the reference curve in the material supplier database with a consistency of up to 98%, fully verifying the excellent ability of the speckle pattern prepared by the method of this invention to provide high-fidelity and high-reliability strain data.

[0042] 4) Data quality: The strain field calculated by DIC has an extremely low noise level and a strain resolution of 10με (micro-strain), which meets the requirements of forming tests.

[0043] Example 2 Experimental material: HC340 / 590DPD+Z high-strength steel plate, dimensions: 300mm×300mm×1.5mm; Test equipment: the self-filtering protection device described in this utility model, handheld spray cans (matte white primer, matte black speckled paint), molding test machine and DIC system (2×2 megapixel camera); 1) Safety and environmental indicators: Background VOC concentration in the spraying chamber before spraying: 0.04 mg / m³.

[0044] During the spraying process, the peak VOC concentration is 30 mg / m³. The negative pressure fan system 3 automatically triggers accelerated filtration, and the accelerated filtration stops after the concentration drops to 20 mg / m³.

[0045] Five minutes after the spraying was completed, the VOC concentration dropped to 0.8 mg / m³ (far below the 10 mg / m³ limit specified in the national standard GBZ 2.1-2019). Once the concentration reaches the standard, the safety lock on the box door automatically releases, and the operator removes the steel plate sample.

[0046] 2) Speckle quality indicators: Speckle diameter: average diameter 302 μm, standard deviation ±8 μm, indicating excellent speckle size uniformity; Speckle density: approximately 55%, within the ideal range of 40%-60% for DIC analysis; Contrast ratio: White background grayscale value 225, black spot grayscale value 32, contrast ratio up to 87%; Adhesion: According to the ASTM D3359 standard, the cross-cut adhesion test was conducted, and the adhesion reached level 5B (the highest level), with no peeling.

[0047] 3) Molding test and DIC analysis results: The prepared specimens were subjected to a cold stamping simulation test on a sheet metal forming testing machine. After experiencing a complex strain path, the speckle pattern showed no discoloration, cracking, or flaking, maintaining a high degree of integrity.

[0048] The DIC system successfully captured the full-field strain distribution of the steel plate during the forming process, with a clear maximum principal strain cloud map and no mismatch or data loss caused by speckle quality. like Figure 4 As shown, the calculated forming limit curve (FLC) matches the reference curve in the material supplier database by 98%, which fully verifies the excellent ability of the speckle pattern prepared by the method of this invention to provide high-fidelity and high-reliability strain data.

[0049] 4) Data quality: The strain field calculated by DIC has an extremely low noise level and a strain resolution of 11με (micro-strain), which meets the requirements of forming tests.

[0050] Example 3 Test material: DP780+Z steel plate, 1.5mm thick; Test equipment: the self-filtering protection device described in this utility model, handheld spray cans (fast-drying matte white primer, fast-drying matte black speckled paint), sheet forming test machine and DIC system (2×2 million pixel camera); 1) Safety and environmental indicators: Background VOC concentration in the spraying chamber before spraying: 0.05 mg / m³.

[0051] The peak VOC concentration during the spraying process was 22 mg / m³. Due to the use of fast-drying paint, the initial VOC release rate was high, but the negative pressure of the system effectively controlled it. After the spraying was completed and a short period of purification was carried out, the VOC concentration dropped to 0.6 mg / m³, which is far below the safety limit of 10 mg / m³ specified in the Chinese National Occupational Health Standard GBZ2.1-2019. Once the concentration reaches the standard, the safety lock on the box door automatically releases, and the operator removes the steel plate sample.

[0052] 2) Speckle quality indicators: Speckle diameter: average diameter 275 μm, standard deviation ±12 μm; Speckle density: approximately 48%, within the ideal range of 40%-60% for DIC analysis; Contrast ratio: White background grayscale value 218, black spot grayscale value 35, contrast ratio 85%; Adhesion: According to the ASTM D3359 standard, the cross-cut adhesion test was conducted, and the adhesion reached level 5B (the highest level), with no peeling.

[0053] 3) Molding test and DIC analysis results: The prepared specimens were subjected to a cold stamping simulation test on a sheet metal forming testing machine. After experiencing a complex strain path, the speckle pattern showed no discoloration, cracking, or flaking, maintaining a high degree of integrity.

[0054] The DIC system successfully captured the full-field strain distribution of the steel plate during the forming process, with a clear maximum principal strain cloud map and no mismatch or data loss caused by speckle quality. like Figure 5 As shown, the calculated forming limit curve (FLC) matches the reference curve in the material supplier database with a 97% agreement, verifying the superior ability of the speckle pattern prepared by the present invention to provide high-fidelity and high-reliability strain data.

[0055] 4) Data quality: The strain field calculated by DIC has an extremely low noise level and a strain resolution of 10με (micro-strain), which meets the requirements of forming tests.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A closed-loop filter protection device for DIC speckle patterns used in steel plate forming tests, characterized in that, include: The spray booth is equipped with a negative pressure fan system on the top. The front of the spray booth is equipped with a glass observation window and a door. A sealing strip is installed at the connection between the glass observation window and the door and the spray booth. The side wall of the spray booth is equipped with two glove operation holes, and gloves are connected to the inside of the glove operation holes; a spray can bracket and a VOC sensor are installed on the lower side of the glass observation window inside the spray booth. The spray booth is equipped with lamp tubes on the inside of the top of the booth, and heating plates and temperature sensors are also installed on the side walls of the booth. The bottom of the spray booth is a workbench, on which a magnetic chuck is installed to fix the steel plate sample by magnetic attraction.

2. The closed-loop filter protection device for DIC speckle in steel plate forming tests according to claim 1, characterized in that, The lamp tube includes a UV germicidal lamp and an LED for lighting.

3. The closed-loop filter protection device for DIC speckle in steel plate forming tests according to claim 1, characterized in that, The cabinet door is equipped with an electronic safety lock, which is linked to a VOC sensor and controls the door to unlock based on the air quality data inside the cabinet.

4. The closed-loop filter protection device for DIC speckle in steel plate forming tests according to claim 1, characterized in that, The spray booth enclosure is sealed by a sealing strip to achieve compression sealing of the door, and the negative pressure fan system continuously maintains an air pressure environment of -50~-60Pa to prevent harmful gases from leaking out.

5. The closed-loop filter protection device for DIC speckle in steel plate forming tests according to claim 1, characterized in that, The spray can bracket is used to fix the self-spraying paint can, and the operator completes the spraying operation on the steel plate sample through the glove operating hole.

6. The closed-loop filter protection device for DIC speckle in steel plate forming tests according to claim 1, characterized in that, The heating plate is linked with a temperature sensor to achieve stepped heating and drying.

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