Speckle coating preparation method based on synchronous measurement of pressure, temperature and deformation

Abstract

The application discloses a speckle coating preparation method based on synchronous measurement of pressure, temperature and deformation, and relates to the field of aerodynamics and fluid mechanics testing; the method comprises the following steps: preparing temperature-sensitive paint: dissolving fluorescent molecules with a thermal quenching effect in an organic solvent to form a fluorescent solution, and then mixing the fluorescent solution with transparent varnish and a curing agent and stirring to obtain uniform temperature-sensitive paint; preparing pressure-sensitive paint: dissolving or dispersing fluorescent molecules with an oxygen quenching effect and a polymer carrier in an organic solvent, and stirring to obtain uniform pressure-sensitive paint; first mask spraying; second mask spraying; coating curing: after the mask is removed, the coating is cured, and temperature-sensitive areas and pressure-sensitive areas that are not overlapped in space are formed on the surface of a model to be measured. The application eliminates signal interference caused by cross-sensitivity of different functional materials, and ensures the independence and accuracy of pressure and temperature measurement data.

Description

Technical Field

[0001] This invention relates to the field of aerodynamics and fluid dynamics testing, and in particular to a method for preparing speckle coatings based on simultaneous measurement of pressure, temperature and deformation. Background Technology

[0002] In aerodynamic and fluid dynamics experiments, simultaneous, non-contact, full-field measurements of pressure, temperature, and structural deformation are crucial for revealing complex mechanisms. With the development of high-end equipment such as hypersonic vehicles and advanced turbomachinery, traditional single-parameter or time-division measurement methods are no longer sufficient to meet the demands of observing multi-field collaborative evolution processes at high spatiotemporal resolution. Therefore, developing a surface coating technology capable of integrating multiple sensing functions within the same field of view without interference has become an urgent need in the fields of experimental mechanics and aerothermodynamics.

[0003] The main challenges currently facing this field can be summarized in the following two points: First, the integration of multi-physics sensing capabilities. Achieving simultaneous measurement of pressure, temperature, and deformation within the same field of view requires the sensing coating to respond to multiple physical quantities simultaneously.

[0004] Second, avoid signal crosstalk between multiple physical fields. It is necessary to ensure that multiple sensing functions are spatially distributed without interfering with each other and are physically isolated, so as to avoid cross-sensitivity and signal crosstalk between different sensing materials, thereby ensuring the accuracy of the measurement.

[0005] However, current technologies lack coating preparation solutions that can simultaneously and effectively address the issues of crosstalk between multi-physics signals and functional integration.

[0006] Dong Z., Liang L., Zhang W., Jiao L., Peng D., & Liu Y. (2020) proposed an innovative grid-patterned pressure-sensitive paint system (PSP) in their research "Simultaneous pressure and deformation field measurement on helicopter rotor blades using a grid-patterned pressure-sensitive paint system" published in the journal Measurement (Vol. 152, Article No. 107359). This system successfully achieved simultaneous measurement of surface pressure and three-dimensional topography of rotating helicopter rotors. However, this method cannot simultaneously obtain temperature information.

[0007] The research by Tiwari N., Uchida K., Inoba R., Saito Y., Asai K., & Nonomura T. (2022), in the journal Experiments in Fluids (Vol. 63, Article No. 171), entitled "Simultaneous measurement of pressure and temperature on the same surface by sensitive paints using the sensor selection method," achieved simultaneous measurement of pressure and temperature on the airfoil surface using a sensor selection method. This method typically involves combining a pressure-sensitive coating (PSP) and a temperature-sensitive coating (TSP) to eliminate the interference of temperature on pressure measurement. However, this technique fails to address the problem of simultaneous measurement of structural deformation, and its preparation of the PSP coating requires individually masking the TSP coating, resulting in low efficiency.

[0008] Moon K.-J., Mori H., & Furukawa M. (2018) proposed a lifetime-based dual-layer PSP / TSP technique in Measurement Science and Technology (Vol. 29, No. 12, Article No. 125301) to achieve simultaneous measurement of pressure and temperature using a single camera. This method achieves simultaneous measurement of pressure and temperature through layered design and lifetime difference signal separation. However, this technique cannot completely avoid signal crosstalk between multiple physics fields, may suffer from spectral overlap for different luminescent molecules, and cannot simultaneously measure displacement fields.

[0009] Therefore, this invention proposes a method for preparing speckle coatings based on simultaneous measurement of pressure, temperature, and deformation. Summary of the Invention

[0010] The purpose of this invention is to address the shortcomings of existing technologies by proposing a speckle coating preparation method based on simultaneous measurement of pressure, temperature, and deformation.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: A speckle coating preparation method based on simultaneous measurement of pressure, temperature, and deformation employs a two-step mask in-situ forming technique to sequentially prepare spatially complementary temperature-sensitive and pressure-sensitive coatings on the surface of the model under test. The temperature-sensitive coating exists in the form of discrete speckles, and its spatial distribution characteristics simultaneously serve as feature points for calculating full-field deformation in digital image correlation algorithms. The method specifically includes the following steps: S1: Preparation of temperature-sensitive coating: Fluorescent molecules with thermal quenching effect are dissolved in an organic solvent to form a fluorescent solution, which is then mixed with a transparent varnish and a curing agent and stirred to obtain a uniform temperature-sensitive coating; S2: Preparation of pressure-sensitive coating: Fluorescent molecules with oxygen quenching effect are dissolved or dispersed together with polymer carriers in an organic solvent and stirred to obtain a uniform pressure-sensitive coating; S3: First step mask spraying: A first mask with multiple randomly distributed through holes is covered on the model surface. The temperature-sensitive coating obtained in step S1 is sprayed onto the model surface through the through holes to form a discretely distributed speckled temperature-sensitive coating. Then the first mask is removed. S4: Second step mask spraying: A second mask with a pattern complementary to the first mask is applied to the model surface. The pressure-sensitive coating obtained in step S2 is sprayed onto the model surface through the transparent area of ​​the second mask, so that it covers the area of ​​the model surface not covered by the temperature-sensitive coating. S5: Coating Curing: After removing the mask, the coating is cured, forming temperature-sensitive and pressure-sensitive areas that do not overlap in space on the surface of the model to be tested.

[0012] Preferably, in step S1, the mass ratio of fluorescent solution, transparent varnish and curing agent is 1:2:1 to 1:5:1.

[0013] Preferably, the fluorescent molecule with thermal quenching effect is Ru(dpp)3, and the mass ratio of fluorescent solution, transparent varnish and curing agent is 1:3:1.

[0014] Preferably, in step S2, the fluorescent molecule with oxygen quenching effect is PtTFPP or PtOEP; the polymer carrier is polystyrene, silicone rubber or polyethylene.

[0015] Preferably, in step S3, the through-hole shape of the first mask is circular, polygonal, or irregular, and the diameter of the through-hole is 1-10 mm; the mask material is metal, polymer, or composite material, and the thickness is 0.5-2 mm.

[0016] Preferably, the diameter of the through-hole in the first mask is 2-5 mm.

[0017] Preferably, in step S3, the distance between the first mask and the model surface is 3-10 mm.

[0018] Preferably, in step S2, the pattern of the second mask is complementary to that of the first mask, and its shielding area is a circle with a diameter 1-2 mm larger than the actual diameter of the temperature-sensitive coating. The shielding areas are interconnected by connecting strips with a width of 1-3 mm.

[0019] Preferably, the temperature-sensitive coating formed in step S3 has an actual diameter that is 0.5-2 mm larger than the diameter of the through hole in the first mask.

[0020] Preferably, in steps S3 and S4, a spray gun is used for spraying, and the spraying direction is perpendicular to the model surface.

[0021] The beneficial effects of this invention are as follows: Signal crosstalk is avoided: Through a spatially complementary mask design, the temperature and pressure sensitive coatings are physically isolated, fundamentally eliminating signal interference caused by the cross-sensitivity of different functional materials, and ensuring the independence and accuracy of pressure and temperature measurement data.

[0022] Achieving integrated functionality: The temperature-sensitive coating also serves as a speckle marker for deformation analysis, enabling a single structure to have the dual functions of sensing temperature and characterizing deformation. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the preparation process of the present invention.

[0024] Figure 2 This is a schematic diagram of the first mask used in the first step of the present invention.

[0025] Figure 3 This is a schematic diagram of the second mask used in the second step of the present invention.

[0026] In the picture: 1 is the surface of the model to be tested, 2 is the first mask, 3 is the mask support, 4 is the temperature-sensitive coating, 5 is the second mask, 6 is the temperature-sensitive coating, 7 is the pressure-sensitive coating, and 8 is the pressure-sensitive coating. Detailed Implementation

[0027] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0029] Example 1

[0030] This embodiment uses a planar model to be tested as an example to illustrate the preparation process of the present invention in detail.

[0031] S1: Preparation of temperature-sensitive coating: Weigh 20mg of Ru(dpp)3 fluorescent molecules, dissolve them in 10ml of methanol, and stir magnetically for 3 hours in a sealed container to obtain a homogeneous and transparent fluorescent solution; then, mix the fluorescent solution with 30g of G2-7800S transparent varnish and 10g of AK260 curing agent (mass ratio approximately 1:3:1), and continue to stir magnetically for 3 hours under sealed conditions to obtain a uniform temperature-sensitive coating, which should be stored away from light for later use.

[0032] S2: Preparation of pressure-sensitive coating: Weigh 1.5g of polystyrene particles and dissolve them in 50ml of dichloromethane, stirring until completely dissolved; weigh 12.5mg of PtTFPP and add it to the above solution, stirring in the dark for 1 hour to ensure complete dissolution. Subsequently, add 7.5g of hollow silica microspheres with an average particle size of 2μm (to increase the coating's air permeability and enhance pressure response), and disperse using an ultrasonic cell disruptor for 30 minutes to obtain a uniform pressure-sensitive coating slurry, which is then stored in the dark for later use.

[0033] S3: Step 1 Mask Coating: A 1mm thick stainless steel plate is used to laser-cut a first mask 2, which has randomly distributed 3mm diameter circular through-holes. The first mask 2 is fixed to the surface of the test model 1, which is clean and dry, 5mm above the surface using a mask support 3. Using an air spray gun, temperature-sensitive coating 4 is sprayed vertically and evenly through the through-holes of the first mask 2. Due to the diffusion of the coating, discrete circular temperature-sensitive coating spots with a diameter of approximately 4mm are formed on the surface of the test model. After spraying, the first mask 2 and the mask support 3 are carefully removed.

[0034] S4: Second step mask spraying: A second mask 5 is made using a 1mm thick stainless steel plate; its pattern is strictly complementary to the first mask 2: the masking area is a circle with a diameter of 5mm (slightly larger than the actual diameter of the temperature-sensitive coating spot formed in the first step, which is 4mm), and each circular masking area is connected to the outer frame by a 1.5mm wide connecting strip; the second mask 5 is fixed 5mm above the surface 1 of the model to be tested, ensuring that its circular masking area is precisely aligned and covered with the formed temperature-sensitive coating 6. Using an air spray gun, the pressure-sensitive coating 7 is sprayed vertically and evenly through the connected area of ​​the second mask 5; the coating will cover all areas not occupied by the temperature-sensitive coating 6.

[0035] S5: Coating Curing: Remove the second mask 5, place the coated model in a ventilated, dust-free, and light-proof environment, and allow it to cure at room temperature for more than 6 hours; finally, a composite functional coating consisting of discrete circular temperature-sensitive areas (speckle) and continuous mesh pressure-sensitive areas is obtained on the surface of the model to be tested; the temperature-sensitive areas can be used for temperature measurement based on thermal quenching effect and deformation measurement based on digital image correlation; the pressure-sensitive areas can be used for pressure measurement based on oxygen quenching effect.

[0036] Example 2

[0037] This embodiment is basically the same as Embodiment 1, except that the fluorescent materials and their ratios used in steps S1 and S2 are different, in order to demonstrate the material universality of this method.

[0038] S1: Preparation of temperature-sensitive coating: Eu(TTA)3phen was used as the thermal quenching fluorescent molecule, and xylene was used as the solvent to prepare a fluorescent solution with a concentration of 1 mg / ml; the solution, nitrocellulose varnish and curing agent were mixed in a mass ratio of 1:4:1 and stirred for 2 hours to obtain the temperature-sensitive coating.

[0039] S2: Preparation of pressure-sensitive coating. PtOEP was used as the oxygen quenching fluorescent molecule, silicone rubber RTV-118 was used as the polymer carrier, and toluene was used as the solvent. PtOEP (0.5 mg / ml) and silicone rubber prepolymer (0.2 g / ml) were dissolved together in toluene, and silicone rubber curing agent (according to the prepolymer ratio) was added. The mixture was stirred for 2 hours to obtain the pressure-sensitive coating.

[0040] S3-S5: The mask spraying and curing steps are the same as in Example 1; the coating prepared in this example also has the ability to measure three fields simultaneously and is suitable for flexible model surfaces that require elasticity.

[0041] Example 3

[0042] Steps S1, S2, S4, and S5 in this embodiment are the same as in Embodiment 1. The difference lies in step S3: A first mask 2 is fabricated using a 0.5mm thick polyimide film; the through-holes are randomly distributed squares with sides of 2mm, and the spacing between the through-holes varies. The mask is then attached tightly to the surface of a complex 3D model (such as an airfoil) using vacuum adsorption; during spraying, the distance between the spray gun and the surface is adjusted to 10mm to reduce lateral diffusion of the coating. The resulting temperature-sensitive coating is a square speckle pattern with an actual side length of approximately 2.8mm; the second mask 5 has a 3.2mm side square covering area with a 1mm wide connecting strip. This embodiment demonstrates that the present invention is applicable to complex curved surfaces, and the speckle shape and size can be flexibly designed according to measurement resolution requirements.

[0043] Example 4

[0044] S1: Preparation of temperature-sensitive coating: Inert fluorescent particles (europium-doped aluminate phosphor) that are not sensitive to temperature are mixed with high-temperature resistant silicate binder and ground into a slurry; this coating is only used as a high-temperature stable speckle mark for deformation measurement and is not used for temperature measurement; temperature measurement is carried out simultaneously by other means such as infrared thermal imager.

[0045] S2: Preparation of pressure-sensitive coating: A high-temperature PtTFPP derivative is mixed with a high-temperature resistant silicone resin carrier (polymethylsiloxane) and dispersed in a high-boiling-point solvent (dimethylsiloxane cyclic) to prepare a high-temperature resistant pressure-sensitive coating.

[0046] S3: The first step of mask spraying is the same as in Example 1, forming inert fluorescent speckle.

[0047] S4: The second step of mask spraying is the same as in Example 1, forming a high-temperature and pressure-sensitive coating.

[0048] S5: The coating is cured by a stepped temperature increase heat treatment, first at 80℃ for 2 hours, then at 150℃ for 4 hours, to obtain high temperature resistant coating performance; This embodiment illustrates that the two-step mask space isolation concept of the present invention can be combined with different functional materials to adapt to a wider range of testing environments.

[0049] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing speckle coatings based on simultaneous measurement of pressure, temperature, and deformation, characterized in that, A two-step mask in-situ forming technique is adopted: (1) The first mask through-hole forms a randomly distributed TSP speckle, which is directly used as DIC feature points; (2) The second mask is an integral complementary mask, the diameter of each masking area is 1–2 mm larger than the actual diameter of the corresponding TSP, and they are interconnected by 1–3 mm connecting strips. The PSP is only coated in the remaining continuous area, thereby forming a continuous annular isolation gap around the TSP speckle; a spatially complementary temperature-sensitive coating and a pressure-sensitive coating are sequentially prepared on the model surface. The temperature-sensitive coating exists in the form of discrete speckle patterns, and its spatial distribution characteristics are simultaneously used as feature points in digital image correlation algorithms to calculate full-field deformation; specifically, the following steps are included: S1: Preparation of temperature-sensitive coating: Fluorescent molecules with thermal quenching effect are dissolved in an organic solvent to form a fluorescent solution, which is then mixed with a transparent varnish and a curing agent and stirred to obtain a uniform temperature-sensitive coating; S2: Preparation of pressure-sensitive coating: Fluorescent molecules with oxygen quenching effect are dissolved or dispersed together with polymer carriers in an organic solvent and stirred to obtain a uniform pressure-sensitive coating; S3: First step mask spraying: A first mask with multiple randomly distributed through holes is covered on the model surface. The temperature-sensitive coating obtained in step S1 is sprayed onto the model surface through the through holes to form a discretely distributed speckled temperature-sensitive coating. Then the first mask is removed. S4: Second step mask spraying: A second mask with a pattern complementary to the first mask is applied to the model surface. The pressure-sensitive coating obtained in step S2 is sprayed onto the model surface through the transparent area of ​​the second mask, so that it covers the area of ​​the model surface not covered by the temperature-sensitive coating. S5: Coating Curing: After removing the mask, the coating is cured, forming temperature-sensitive and pressure-sensitive areas that do not overlap in space on the model surface; In step S2, the fluorescent molecule with oxygen quenching effect is PtTFPP or PtOEP; the polymer carrier is polystyrene, silicone rubber or polyethylene; In step S3, the through-hole shape of the first mask is circular, polygonal, or irregular, and the diameter of the through-hole is 1-10mm; the mask material is metal, polymer, or composite material, and the thickness is 0.5-2mm. The diameter of the through-hole in the first mask is 2-5 mm; In step S3, the distance between the first mask and the model surface is 3-10mm.

2. The method for preparing speckle coating based on simultaneous measurement of pressure, temperature, and deformation according to claim 1, characterized in that, In step S1, the mass ratio of fluorescent solution, transparent varnish and curing agent is 1:2:1 to 1:5:

1.

3. The method for preparing speckle coating based on simultaneous measurement of pressure, temperature, and deformation according to claim 2, characterized in that, The fluorescent molecule with thermal quenching effect is Ru(dpp)3, and the mass ratio of fluorescent solution, transparent varnish and curing agent is 1:3:

1.

4. The method for preparing speckle coating based on simultaneous measurement of pressure, temperature, and deformation according to claim 1, characterized in that, In step S2, the pattern of the second mask is complementary to that of the first mask, and its shielding area is a circle with a diameter 1-2 mm larger than the actual diameter of the temperature-sensitive coating. The shielding areas are interconnected by connecting strips with a width of 1-3 mm.

5. The method for preparing speckle coating based on simultaneous measurement of pressure, temperature, and deformation according to claim 4, characterized in that, The temperature-sensitive coating formed in step S3 has an actual diameter that is 0.5-2 mm larger than the diameter of the through-hole in the first mask.

6. The method for preparing speckle coatings based on simultaneous measurement of pressure, temperature, and deformation according to any one of claims 1-5, characterized in that, In steps S3 and S4, a spray gun is used for spraying, with the spraying direction perpendicular to the model surface.

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