A system and method for preparing speckles for local strain

Abstract

The present application provides a system and method for preparing speckles for local strain, the preparation system comprising: a preparation platform and a spraying system; the preparation platform comprises an outer platform and an inner platform that can be raised and lowered, the spraying system comprising: a spraying tool and a spraying fixture; the spraying tool is densely covered with a plurality of through holes, the spraying fixture is invertedly provided with a nozzle assembly, and the nozzle assembly is connected to a paint conveying mechanism. In the above description, a method of mechanically spraying speckles is adopted to replace manual spraying speckles, which solves the problems that the speckle size obtained by the manual spraying method is large and cannot meet the measurement requirements of small deformations, and the high scrap rate leads to low sample preparation efficiency; at the same time, the present application also provides a preparation method, which ensures that the speckle is completely consistent with the material during the deformation process, and at the same time will not have any effect on the surface and matrix properties of the material, ensures the consistency of the speckle between different samples, and eliminates the interference caused by the inconsistent speckle between samples.

Description

Technical Field

[0001] One or more embodiments of the present specification relate to the field of deformation measurement and detection technology, and more particularly, to a system and method for preparing speckles for local strain. Background Art

[0002] In recent years, with the advancement of automobile lightweighting and the support of national industrial policies, the use of lightweight materials such as hot-formed steel, aluminum-magnesium alloys, and plastics in automobiles has continued to increase due to their significant weight reduction effects. When it comes to calculations of automobile parts stamping, strength durability, and collision safety, it is necessary to carry out quasi-static stretching, high-speed stretching, forming limit curve (FLC), and fracture failure curve (GISSMO) tests to characterize the deformation and failure behavior of materials under different strain states and strain rates. The test data is imported into the software to carry out CAE analysis of automobile parts. Therefore, the accuracy of the measurement data directly determines the accuracy of CAE analysis.

[0003] In various current measurement tests, for the measurement of material strain, most of them have adopted non-contact digital image correlation measurement technology (DIC: Digital Image Correlation) to replace traditional extensometer measurement, caliper measurement, etched grid measurement and other methods. The measurement has almost no effect on the properties of the sample itself, has the characteristics of full-field measurement, can fully obtain the displacement, strain and other information of components and materials, and is widely used in precise strain measurement. The principle of DIC measurement technology is to determine the deformation characteristics of the material in the process by analyzing the correlation of speckles attached to the surface of the material before and after deformation. Therefore, as the key feature of DIC measurement technology that reflects the deformation of components and materials, the quality of speckles will directly affect the accuracy of the measurement results. Therefore, high-quality speckles play a very important role in measurement.

[0004] Regarding the preparation of speckles, the most commonly used method at present is the manual spraying method: that is, the sample preparation personnel use handheld spray paint and other spot preparation equipment to manually spray the material surface. The speckle size obtained in this way is large and cannot meet the measurement needs of small deformations. At the same time, due to the instability of speckle quality, it often leads to waste samples because some speckles are too large in size. The high waste rate leads to low sample preparation efficiency. In order to solve the related problems, a method of using laser burning is proposed in the patent CN112014181A, which removes the coating at the specified position on the material that has been sprayed with black paint coating to form a plurality of tiny through holes as spots of speckle. This method greatly improves the sample preparation efficiency and sample preparation accuracy, but a certain amount of heat input will be generated to the sample of the material to be inspected during laser burning, which may affect the material properties; in the patent CN109458943A, a method of pre-opening micropores on polyethylene film and similar films by laser, pasting them on the surface of the material for spraying and sample preparation, and then removing the polyethylene film is proposed. This method is similar to the above method, but after spraying, when the polyethylene film is removed, part of the sprayed primer will be taken away, and even the surface of the substrate will be damaged; in the patent CN113504110A, a speckle preparation method based on standard speckle stickers is proposed, which greatly improves the preparation efficiency and preparation quality consistency, but when the material undergoes large strain, the stickers may slide or even detach from the substrate. Summary of the invention

[0005] In view of this, an object of one or more embodiments of the present specification is to provide a system and method for preparing speckles for local strain, which ensures the consistency of speckles between different samples and eliminates interference caused by inconsistent speckles between samples.

[0006] In a first aspect, a system for preparing speckles of local strain is provided, comprising: a preparation platform and a spraying system located directly above the preparation platform; wherein:

[0007] The preparation platform comprises a liftable outer platform and an inner platform, wherein a clearance space is provided on the outer platform for the inner platform to pass through;

[0008] The spraying system comprises: a spraying tool with adjustable spacing and a spraying fixing seat; the spraying tool is densely covered with a plurality of through holes, the spraying fixing seat is invertedly provided with a spray head assembly facing the plurality of through holes, and the spray head assembly is connected to a paint conveying mechanism;

[0009] When the inner platform is raised to the first set position, the inner platform is located inside the clearance space, and the inner platform and the outer platform are spaced apart by a set height difference;

[0010] When the inner platform and the outer platform are synchronously raised to the second set position, the outer platform and the bottom surface of the painting tool are in contact with each other.

[0011] In the above description, the mechanical spraying speckle method is used to replace the manual spraying speckle method, which solves the problems of the large speckle size obtained by the manual spraying method and cannot meet the measurement requirements of small deformations, and the high scrap rate leads to low sample preparation efficiency.

[0012] In a specific possible implementation manner, the outer platform and the inner platform are driven by a lifting mechanism to independently lift and / or synchronously lift and lower.

[0013] In a specific possible implementation manner, the paint spraying tool and the paint spraying fixing seat are connected via locking support rods distributed at four corners, and nuts are threadedly connected at both ends of the locking support rods.

[0014] In a specific embodiment, the diameter of each through hole is between 20 and 30 μm, and the distance between any two adjacent through holes is less than or equal to 150 μm.

[0015] In a specific implementation manner, the distribution density of the plurality of through holes accounts for 60% to 80% of the painting tool.

[0016] In a specific embodiment, the nozzle assembly includes: a plurality of nozzles arranged and distributed;

[0017] The multiple spray heads spray the multiple through holes in the painting tooling area.

[0018] In a specific possible implementation scheme, the paint delivery mechanism includes: a paint storage tank connected to the plurality of spray heads via a paint delivery pipeline;

[0019] The paint delivery pipeline is equipped with a paint spraying sensor.

[0020] In a specific implementation scheme, the preparation system further includes an operation panel, and the operation panel controls the corresponding lifting and lowering of the lifting mechanism and controls the intermittent opening of the nozzle assembly.

[0021] In a specific implementation manner, the set drop is: the drop distance between the upper surface of the inner platform and the upper surface of the outer platform is 0.1 mm to 0.5 mm.

[0022] In a second aspect, a method for preparing a speckle for local strain is provided, characterized in that the method comprises the following steps:

[0023] Spray the first color primer on the sample to be tested, and leave it to stand until it is completely dry;

[0024] The sample to be tested is placed on the inner platform, and the lifting mechanism independently drives the inner platform to rise to a first set position with a set height difference from the outer platform;

[0025] The lifting mechanism synchronously drives the inner platform and the outer platform to rise until they are raised to a second set position where the outer platform and the bottom surface of the painting tooling are in contact with each other;

[0026] Starting a plurality of spray heads to spray a second color paint, the second color paint falls through a plurality of through holes and adheres to the sample to be inspected, forming speckles;

[0027] The lifting mechanism synchronously drives the outer platform and the inner platform to descend, and the sample to be tested is taken out after the surface of the sample to be tested is left to stand until it is completely dry.

[0028] In a specific possible embodiment, there is a high contrast between the first color paint and the second color paint.

[0029] The above method ensures that the speckle is completely consistent with the material during the deformation process, and at the same time will not have any impact on the material surface and matrix performance, ensuring the consistency of speckle between different samples and eliminating the interference caused by inconsistent speckle between samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate one or more embodiments of the present specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only one or more embodiments of the present specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 A schematic diagram of the structure of a system for preparing speckles for local strain provided in an embodiment of the present application;

[0032] Figure 2 A schematic diagram of the structure of the painting tool provided in the embodiment of the present application;

[0033] Figure 3 A schematic diagram of a sample to be tested after being sprayed with speckle provided in an embodiment of the present application;

[0034] Figure 4 A flow chart of a method for preparing speckles for local strain provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0036] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in one or more embodiments of this specification should be understood by people with ordinary skills in the field to which this disclosure belongs. The "first", "second" and similar words used in one or more embodiments of this specification do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0037] To facilitate understanding of the system and method for preparing speckles for local strain provided in the embodiments of the present application, the application scenario is first explained. The preparation system adopts mechanical spraying, which solves the problems of large speckle size obtained by manual spraying and cannot meet the measurement requirements of small deformations, high scrap rate and low sample preparation efficiency, and significantly improves the efficiency of speckle preparation. At the same time, it can also replace speckle stickers such as flexible membrane structures, avoiding the phenomenon of sliding or even detachment between the sticker and the substrate when the material undergoes large strain, thereby ensuring the accuracy of the measurement results.

[0038] To this end, an embodiment of the present application provides a lightweight design method, which is described in detail below with reference to specific drawings.

[0039] To facilitate the description of the preparation system provided in the embodiment of the present application, an X, Z, and Y coordinate system is first established, wherein the X direction is the length direction of the preparation system, the Y direction is the width direction of the preparation system, and the Z direction is the height direction of the preparation system, and the X direction is perpendicular to the Y direction and the Z direction.

[0040] refer to Figure 1 , Figure 1 The schematic diagram of the structure of the preparation system for local strain speckle is shown; the preparation system is used to prepare speckles using mechanized equipment, thereby reducing the problems of large speckle size obtained by artificial spraying method that cannot meet the measurement requirements of small deformations, high scrap rate resulting in low sample preparation efficiency, etc.

[0041] The preparation system comprises a preparation platform, which is used to fix a sample 1 to be tested, and has an outer platform 3 and an inner platform 2 which can be lifted and lowered vertically along the Z direction.

[0042] The outer platform 3 and the inner platform 2 are both driven to rise and fall by a lifting mechanism 14; Figure 1It can be seen that the outer platform 3 and the inner platform 2 are both rectangular platforms with their length along the X direction and their width along the Y direction, and are driven by the lifting mechanism 14 to lift the outer platform 3 and the inner platform 2 individually or synchronously.

[0043] The lifting mechanism 14 vertically drives the outer platform and the inner platform to perform a corresponding lifting process, so as to raise the sample 1 to be tested to a suitable position, and cooperate with the spraying system located just above the preparation platform to spray the speckle 17 .

[0044] In order to facilitate understanding of the lifting mechanism 14, the lifting mechanism 14 is divided into a lifting mechanism 14 supporting both ends of the outer platform 3 as a first lifting mechanism, and a lifting mechanism 14 supporting both ends of the inner platform as a second lifting mechanism.

[0045] It can be seen that the lifting mechanism 14 is two independent lifting devices, which can adopt telescopic devices such as electric telescopic rods or hydraulic telescopic rods; and the first lifting mechanism and the second lifting mechanism are fixedly assembled on the same platform, and the telescopic direction of the first lifting mechanism and the second lifting mechanism are both along the Z direction.

[0046] When the second lifting mechanism drives the inner platform 2 to rise, since the sample 1 to be tested is placed on the inner platform 2, it is necessary to ensure that the sample 1 to be tested is located on the surface during the process of spraying the speckle pattern 17; for this purpose, a clearance space is opened on the outer platform 3 for the inner platform 2 to pass through; thereby, the inner platform 2 can be located in the clearance space, ensuring that the sample 1 to be tested is exposed for spraying the speckle pattern 17.

[0047] Furthermore, in the embodiment of the present application, in order to ensure that the existing primer on the surface of the sample 1 to be tested will not be damaged, when the inner platform 2 rises to the first set position, the inner platform 2 is located inside the clearance space, and the inner platform 2 and the outer platform 3 are separated by a set height.

[0048] After the inner platform 2 is located inside the clearance space of the outer platform 3, the second lifting mechanism is controlled by the operation panel 12 according to the displacement sensor 15 for detecting the heights of the inner platform 2 and the outer platform 3 to raise the inner platform 2 to a position with a set height difference from the upper surface of the outer platform 3, thereby ensuring that the sample 1 to be tested is always in a recessed position.

[0049] The set drop is based on the thickness of the sample 1 to be tested. The drop is preferably set to a drop distance of 0.1mm to 0.5mm between the upper surface of the inner platform 2 and the upper surface of the outer platform 3, thereby ensuring that the sample 1 to be tested is always located in the groove structure and the primer of the sample 1 to be tested is not damaged.

[0050] Continue reading Figure 1-3When the inner platform 2 is located at the first set position with a set height difference from the outer platform 3, the operation panel 12 controls the first lifting mechanism and the second lifting mechanism to rise synchronously to the second set position, and the second set position cooperates with the spraying system to spray the speckle 17 on the sample 1 to be inspected.

[0051] When the spraying system is specifically set up, the spraying system includes a paint spraying tool 11 with adjustable spacing and a paint spraying fixed seat 9; the paint spraying tool 11 and the paint spraying fixed seat 9 are both stacked along the Z direction; specifically, the paint spraying fixed seat 9 is located above the paint spraying tool 11, and the paint spraying fixed seat 9 and the paint spraying tool 11 are both long-direction platforms with a length along the X direction and a width along the Y direction.

[0052] The gap between the paint spray fixture 9 and the paint spray fixture 11 is set to be adjustable, and the height can be adjusted corresponding to the spray radius of different nozzle assemblies; preferably, the paint spray fixture 11 and the paint spray fixture 9 are connected by locking struts 10 distributed at the four corners, and nuts 8 are threadedly connected at both ends of the locking struts 10. The nuts 8 connected at both ends of the locking struts 10 are used to connect the paint spray fixture 11 and the paint spray fixture 9 into one body. When changing the spacing between the paint spray fixture 11 and the paint spray fixture 9, the locking struts 10 of different lengths can be replaced, or the threaded nuts 8 can be used to lock and fix the upper and lower surfaces of the paint spray fixture 11 or the paint spray fixture 9 on the threaded section of the locking struts 10.

[0053] The paint spraying tool 11 in the embodiment of the present application is densely covered with multiple through holes 16. The paint spraying tool 11 is made of mold steel + titanium nitride coating, and multiple micro through holes 16 are pre-opened to ensure that the paint sprayed from the nozzle assembly invertedly arranged on the paint spraying fixed seat 9 falls along the multiple through holes 16 and adheres to the surface of the sample 1 to be tested.

[0054] Specifically, the plurality of through holes 16 are laser-drilled according to the random generation result of the computer simulation software; before the simulation software is randomly generated, the diameter and distribution density of the through holes 16 need to be constrained input, the diameter of each through hole 16 is between 20 and 30 μm, and the spacing between any two adjacent through holes 16 is ≤150 μm. The distribution density of the plurality of through holes 16 accounts for 60% to 80% of the spray painting tool 11, and the random degree is 0.5 to 0.7.

[0055] During the spraying process, a spray head assembly facing multiple through holes 16 is invertedly arranged on the spray paint fixing seat 9, and the spray head assembly includes: multiple spray heads 4 arranged and distributed; each spray head 4 corresponds to the through hole 16 in the set area of ​​the spray paint tooling 11. The set area is adjusted accordingly according to the pressure of the supplied color paint and the number of the spray heads 4, and no excessive restrictions are made here.

[0056] The spray head assembly is connected to a paint delivery mechanism; the paint delivery mechanism includes: a paint storage tank 5 connected to multiple spray heads 4 through a paint delivery pipeline 6; the paint storage tank 5 preferably stores black paint, and a suction pump is arranged in the paint storage tank 5, so that the black paint is delivered to the multiple spray heads 4 through the paint delivery pipeline 6 for spraying.

[0057] The paint delivery pipeline 6 is equipped with a paint spraying sensor 7 for monitoring the delivery status of black paint. The operation panel 12 controls the multiple nozzles 4 to open at a set frequency, thereby achieving intermittent spraying of color paint to ensure the consistency of the effect of the spraying speckle 17. Of course, a solenoid valve can also be installed on the paint delivery pipeline 6, and the operation panel 12 controls the solenoid valve to open at a set frequency to deliver black paint to the multiple nozzles 4 for spraying.

[0058] As can be seen from the above description, the operating panel 12 controls the lifting mechanism 14 through the wire 13 or signal, so that the outer platform 3 and the inner platform 2 have a set height difference, and the sample 1 to be tested sprayed with primer is placed on the inner platform 2; the operating panel 12 controls the first lifting mechanism and the second lifting mechanism to rise synchronously, and stops rising after rising to the second set position. At this time, the outer platform 3 is completely in contact with the bottom surface of the painting tool 11. Due to the set height difference between the inner platform 2 and the outer platform 3, the sample 1 to be tested does not have stress contact with the bottom surface of the painting tool 11, thereby avoiding damage to the primer; the operating panel 12 starts multiple nozzles 4 and uses black paint for spraying. The black paint falls through multiple micro through holes 16 and adheres to the sample 1 to be tested, forming speckles 17.

[0059] refer to Figure 4 In addition, the present application also provides a method for preparing a speckle for local strain, which specifically includes the following steps:

[0060] S1. Spray the first color paint primer on the sample to be inspected, and let it stand until it is completely dry after spraying. Specifically, use white spray paint as the primer, spray the sample to be inspected on one side with 100% coverage, and let it stand until it is completely dry after spraying.

[0061] S2. Place the sample to be tested on the inner platform, and the lifting mechanism independently drives the inner platform to rise to a first set position with a set height difference with the outer platform; specifically, place the sample to be tested after being processed in step S1 on the inner platform of the preparation platform, and slowly move the inner platform upwards through the lifting mechanism until it is connected to the outer platform, and keep a height difference of 0.1mm to 0.5mm between the upper surface of the sample to be tested and the upper surface of the outer platform to ensure that the existing primer on the surface of the sample to be tested will not be damaged when it is subsequently attached to the painting tooling; the height difference is controlled by a displacement sensor and displayed in real time by the operation panel.

[0062] S3. The lifting mechanism synchronously drives the inner platform and the outer platform to rise until they reach the second set position where the outer platform and the bottom surface of the painting tool are in contact with each other; specifically, the outer platform and the inner platform of the preparation platform are slowly and synchronously moved up until the outer platform is completely in contact with the painting tool with a plurality of through holes pre-opened; the painting tool is made of metal material, and a plurality of micro through holes are pre-opened to ensure that the paint sprayed from the nozzle falls along the through holes and adheres to the surface of the sample to be tested; the through holes are laser opened according to the random generation results of the computer simulation software; before the simulation software is randomly generated, the diameter and distribution density of the through holes need to be constrained input; the average diameter of the through holes is 20-30μm, the spacing is ≤150μm, the distribution density is 60%-80% coverage, and the random degree is 0.5-0.7.

[0063] S4. Start multiple nozzles to spray the second color paint. The second color paint falls through multiple through holes and adheres to the sample to be tested, forming speckles. Specifically, after inputting the control of a single spraying time, the number of spraying times and the spraying radius on the operation panel, start the nozzles and use black paint for spraying. The black paint falls through micropores and adheres to the sample to be tested, forming speckles. The black paint is stored in a paint storage tank and transported to each nozzle through a paint delivery pipeline and sprayed out.

[0064] S5. The lifting mechanism drives the outer platform and the inner platform to descend synchronously, and the samples are taken out after standing still until the surface of the samples is completely dry. The preparation platform is slowly and synchronously moved down, and after standing still until the surface is completely dry, the inner platform is slowly moved up by the lifting mechanism until it is higher than the outer platform, so that the samples are taken out conveniently. At this point, the preparation of the samples with speckles is completed, which is used to support the local strain measurement and analysis of materials in various subsequent tests.

[0065] In the present invention, through the above-mentioned speckle preparation method and preparation system, the method of preparing speckle by spray painting is retained, which ensures that the speckle is completely consistent with the material during the deformation process, and will not have any impact on the surface of the material and the performance of the matrix, thereby achieving high-precision and high-efficiency automated preparation of the speckle, while ensuring the consistency of the speckle between different samples, and eliminating the interference caused by inconsistent speckle between samples.

[0066] Continue to refer Figure 1-4 In addition, in the first embodiment of the present application, the speckle preparation of a sample to be tested for a type of forming limit curve (FLC) test specifically includes the following steps:

[0067] Step 1: Use white spray paint as primer to spray the sample on one side with 100% coverage. After spraying, let it stand until it is completely dry.

[0068] Step 2: Place the sample to be tested after being processed in step 1 on the inner platform of the preparation platform, and slowly move the inner platform upwards through the lifting mechanism until it is connected to the outer platform, and keep a height difference of 0.15mm between the upper surface of the sample to be tested and the upper surface of the outer platform to ensure that the existing primer on the surface of the sample to be tested will not be damaged when it is subsequently attached to the painting tooling; the height difference is controlled by the displacement sensor and displayed in real time by the operation panel.

[0069] Step 3, slowly and synchronously move up the outer platform and the inner platform of the preparation platform until the outer platform is fully fitted with the spray painting tooling with a plurality of through holes pre-opened; the spray painting tooling is made of mold steel + titanium nitride coating, and a plurality of micro through holes are pre-opened to ensure that the paint sprayed from the nozzle falls along the through holes and adheres to the surface of the sample to be tested; the through holes are laser opened according to the random generation results of the computer simulation software; before the simulation software is randomly generated, the diameter and distribution density of the through holes need to be constrained input; the average diameter of the through holes is 25μm, the spacing is ≤100μm, the distribution density is 75% coverage, and the random degree is 0.65.

[0070] Step 4. After inputting the control of single spraying time 1s, number of spraying 2 times and spraying radius 40mm on the operation panel, start the 9 nozzles pre-installed on the paint spraying fixture for spraying. Use black paint for spraying. The black paint falls through the through hole and adheres to the sample to be tested, forming speckles. The black paint is stored in the paint storage tank and transported to each nozzle through the paint delivery pipeline and sprayed out.

[0071] Step 5: Slowly and synchronously move the preparation platform downwards, let it stand until the surface is completely dry, and then slowly move the inner platform upwards through the lifting mechanism until it is higher than the outer platform to facilitate the removal of the sample to be tested. At this point, the preparation of the sample to be tested with speckles is completed, which is used to support the local strain measurement and analysis of the material in the forming limit curve (FLC) test.

[0072] In a second embodiment of the present application, the speckle preparation of a sample to be tested for a quasi-static tensile test specifically includes the following steps:

[0073] Step 1: Use white spray paint as primer to spray the sample on one side with a coverage rate of 75% (focus on the middle section, the clamping end does not need to be completely sprayed). After spraying, let it stand until it is completely dry.

[0074] Step 2: Place the sample to be tested processed in step 1 on the inner platform of the preparation platform, and slowly move the inner platform up through the lifting mechanism until it connects with the outer platform, and keep a height difference of 0.15mm between the upper surface of the sample to be tested and the upper surface of the outer platform to ensure that the existing primer on the surface of the sample to be tested will not be damaged when it is subsequently attached to the painting tooling; the height difference is controlled by the displacement sensor and displayed in real time by the operation panel.

[0075] Step 3. Slowly and synchronously move the outer platform and the inner platform of the preparation platform upward until the outer platform is fully fitted with the spray painting tooling with a plurality of pre-opened through holes; the spray painting tooling is made of mold steel + titanium nitride coating, and a plurality of micro through holes are pre-opened to ensure that the paint sprayed from the nozzle falls along the through holes and adheres to the surface of the sample to be tested; the through holes are laser opened according to the random generation results of the computer simulation software; before the simulation software is randomly generated, the diameter and distribution density of the through holes need to be constrained input; the average diameter of the through holes is 30μm, the spacing is ≤120μm, the distribution density is 65% coverage, and the random degree is 0.60.

[0076] Step 4. After inputting the control of single spraying time 1s, number of spraying 2 times and spraying radius 60mm on the operation panel, start the 6 nozzles pre-installed on the paint spraying fixture, and use black paint for spraying. The black paint falls through the micropores and adheres to the sample to be tested, forming speckles; the black paint is stored in the paint storage tank and transported to each nozzle through the paint delivery pipeline and sprayed out.

[0077] Step 5. Slowly and synchronously move the preparation platform downwards, let it stand until the surface is completely dry, and then slowly move the inner platform upwards through the lifting mechanism until it is higher than the outer platform to facilitate the removal of the sample to be tested. At this point, the preparation of the sample to be tested with speckles is completed, which is used to support the local strain measurement and analysis of the material in the quasi-static tensile test.

[0078] The present invention adopts a method of mechanically spraying speckle patterns instead of artificially spraying speckle patterns, thereby solving the problems that the speckle patterns obtained by the artificial spraying method are large in size and cannot meet the measurement requirements of small deformations, and the high scrap rate leads to low sample preparation efficiency, and the preparation efficiency of the speckle patterns is significantly improved. At the same time, the present invention can also replace speckle stickers such as flexible membrane structures, avoiding the phenomenon that the stickers and the substrate slide or even separate when the material undergoes large strain, thereby ensuring the accuracy of the measurement and detection results.

[0079] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present disclosure (including the claims) is limited to these examples. In line with the present disclosure, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present specification as described above, which are not provided in detail for the sake of simplicity.

[0080] In addition, to simplify the description and discussion, and in order not to make one or more embodiments of the present specification difficult to understand, known power / ground connections to integrated circuit (IC) chips and other components may or may not be shown in the provided figures. In addition, the system can be shown in the form of a block diagram to avoid making one or more embodiments of the present specification difficult to understand, and this also takes into account the fact that the details of the implementation of these block diagram systems are highly dependent on the platform on which one or more embodiments of the present specification will be implemented (that is, these details should be fully within the scope of understanding of those skilled in the art). Where specific details (e.g., modeling, finite element simulation) are set forth to describe exemplary embodiments of the present disclosure, it is apparent to those skilled in the art that one or more embodiments of the present specification can be implemented without these specific details or with changes in these specific details. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0081] Although the present disclosure has been described in conjunction with specific embodiments of the present disclosure, many replacements, modifications and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. For example, other memory architectures (e.g., dynamic RAM (DRAM)) may use the embodiments discussed.

[0082] One or more embodiments of this specification are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of this specification should be included in the scope of protection of this disclosure.

Claims

1. A system for preparing speckles for local strain, characterized in that: include: A preparation platform and a spraying system located directly above the preparation platform; wherein, The preparation platform comprises a liftable outer platform and an inner platform, wherein a clearance space is provided on the outer platform for the inner platform to pass through; The spraying system comprises: a spraying tool with adjustable spacing and a spraying fixing seat; the spraying tool is densely covered with a plurality of through holes, the spraying fixing seat is invertedly provided with a spray head assembly facing the plurality of through holes, and the spray head assembly is connected to a paint conveying mechanism; When the inner platform is raised to the first set position, the inner platform is located inside the clearance space, and the inner platform and the outer platform are spaced apart by a set height difference; When the inner platform and the outer platform are synchronously raised to the second set position, the outer platform and the bottom surface of the painting tool are in contact with each other.

2. The system for preparing speckles for local strain according to claim 1, characterized in that: The outer platform and the inner platform are driven by a lifting mechanism to lift independently and / or synchronously.

3. The system for preparing speckles for local strain according to claim 1, characterized in that: The paint spraying tool and the paint spraying fixing seat are connected by locking rods distributed at four corners, and nuts are threadedly connected at both ends of the locking rods.

4. The system for preparing speckles for local strain according to claim 1, characterized in that: The diameter of each through hole is between 20 and 30 μm, and the distance between any two adjacent through holes is less than or equal to 150 μm.

5. The system for preparing speckles for local strain according to claim 4, characterized in that: The distribution density of the plurality of through holes accounts for 60% to 80% of the painting tool.

6. The system for preparing speckles for local strain according to claim 1, characterized in that: The nozzle assembly comprises: a plurality of nozzles arranged and distributed; The multiple spray heads spray the multiple through holes in the painting tooling area.

7. The system for preparing speckles for local strain according to claim 6, characterized in that: The paint delivery mechanism comprises: a paint storage tank connected to the plurality of spray heads via a paint delivery pipeline; The paint delivery pipeline is equipped with a paint spraying sensor.

8. The system for preparing speckles for local strain according to claim 1, characterized in that: The preparation system also includes an operation panel, which controls the corresponding lifting and lowering of the lifting mechanism and controls the intermittent opening of the nozzle assembly.

9. The system for preparing speckles for local strain according to any one of claims 1 to 8, characterized in that: The set drop is: the drop distance between the upper surface of the inner platform and the upper surface of the outer platform is 0.1 mm to 0.5 mm.

10. A method for preparing speckles for local strain, characterized in that: The method is performed using the system for preparing speckles for local strain according to any one of claims 1 to 8, and the method comprises the following steps: Spray the first color primer on the sample to be tested, and leave it to stand until it is completely dry; The sample to be tested is placed on the inner platform, and the lifting mechanism independently drives the inner platform to rise to a first set position with a set height difference with the outer platform; The lifting mechanism synchronously drives the inner platform and the outer platform to rise until they are raised to a second set position where the outer platform and the bottom surface of the painting tooling are in contact with each other; A plurality of spray heads are started to spray a second color paint, and the second color paint falls through a plurality of through holes and adheres to the sample to be inspected to form speckles; The lifting mechanism synchronously drives the outer platform and the inner platform to descend, and the sample to be tested is taken out after the surface of the sample to be tested is left to stand until it is completely dry.

11. The method for preparing speckles for local strain according to claim 10, characterized in that: There is a high contrast between the first color paint and the second color paint.

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