CN115261770A - Thermal spraying installation process for surface resistance strain gauge of thermal structure - Google Patents
Thermal spraying installation process for surface resistance strain gauge of thermal structure Download PDFInfo
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- CN115261770A CN115261770A CN202210701086.5A CN202210701086A CN115261770A CN 115261770 A CN115261770 A CN 115261770A CN 202210701086 A CN202210701086 A CN 202210701086A CN 115261770 A CN115261770 A CN 115261770A
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
- C23C4/134—Plasma spraying
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/009—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone characterised by the material treated
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
- C04B41/50—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials
- C04B41/5025—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials with ceramic materials
- C04B41/5031—Alumina
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
- C04B41/81—Coating or impregnation
- C04B41/85—Coating or impregnation with inorganic materials
- C04B41/87—Ceramics
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
- C23C4/10—Oxides, borides, carbides, nitrides or silicides; Mixtures thereof
- C23C4/11—Oxides
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge
- G01B7/18—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge using change in resistance
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- Chemical Kinetics & Catalysis (AREA)
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- Structural Engineering (AREA)
- Inorganic Chemistry (AREA)
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- Coating By Spraying Or Casting (AREA)
Abstract
The invention discloses a thermal spraying installation process of a surface resistance strain gauge of a thermal structure, which comprises the following steps: carrying out surface treatment on a test area of a tested structure; carrying out plasma spraying treatment on a test area of a tested structure to obtain an insulating layer; on the insulating layer, carrying out plasma spraying treatment on part of the grid wires of the resistance strain gauge for multiple times by using a mask to obtain a first coating; on the first coating, carrying out plasma spraying treatment on the rest part of the resistance strain gauge grid wires for multiple times by using a mask to obtain a second coating; carrying out spraying treatment on the whole areas of the first coating and the second coating to obtain a third coating; the first coating, the second coating and the third coating jointly form a surface covering layer, and the fixed installation of the grid wire of the resistance strain gauge is completed. According to the invention, the resistance strain gauge is combined with the tested structure to form a local microstructure for good strain test at high temperature, and the strain test of the ceramic-based novel composite material thermal structure at the high temperature of 1100 ℃ can be realized.
Description
Technical Field
The invention belongs to the technical field of installation of resistance strain gauges, and particularly relates to a thermal structure surface resistance strain gauge thermal spraying installation process.
Background
When the aircraft flies at hypersonic speed, the aircraft bears a severe force-heat composite environment, and the temperature of a large-area heat-proof structure can reach 1200 ℃. In order to adapt to a severe service environment, the hypersonic aircraft structure largely adopts novel heatproof bearing integrated thermostructural materials. The thermal structure is a structure which bears high-temperature airflow scouring when an aircraft flies at high speed, the development of the thermal structure depends on a large number of ground tests, thermal environment parameters and structural response parameters are obtained in the ground tests, and the thermal structure is one of important purposes of the tests, wherein high-temperature strain is a key parameter. The high-temperature strain test is used for exploring the stress state of the thermal structure of the high-speed aircraft, verifying the thermal strength of the structure and calculating and analyzing a model, and providing reference for evaluation and optimization design of the thermal structure.
Generally, the electrical resistance strain test technique is the main means for obtaining the strain parameter of the structure at high temperature. The technology utilizes the fact that a certain physical corresponding relation exists between the resistance change of the grid wire of the resistance strain gauge and the deformation of a measured structure, and therefore strain parameters of the structure are obtained. Before testing, the resistance strain gauge needs to be mounted on the structure by adopting a corresponding process, so that the strain gauge is combined with the structure, and good strain transmission is realized at high temperature, which is a key factor for testing success or failure. Regarding the installation of the strain gauge, the traditional metal structure can adopt a welding mode to install the resistance strain gauge, and the non-metal material is installed by using a sticking mode. Aiming at the novel composite material with the thermal structure form being a ceramic base, the traditional pasting process has the defects of complex process and long consumed time, particularly, in the process of baking and curing the adhesive layer, the risk of cracking of the adhesive layer caused by shrinkage exists, the mounting failure of the strain gauge is easily caused, and the existing pasting process is only suitable for mounting the non-metal strain gauge within the range of 500 ℃, and cannot be applied to higher temperature.
In addition, in the aspect of spray mounting, a handheld flame spraying mode is usually adopted for mounting the resistance strain gauge on a metal structure, and the application temperature is usually 200-600 ℃. Because of the manual mode, the spraying technology completely depends on manual experience, so that parameters such as spraying thickness and the like are not easy to control, and the defects that the strain gauge is not installed with high power, the dispersion degree of strain test data is poor and the like exist. The spraying process of the resistance strain gauge aiming at the novel composite material with the thermal structure form of ceramic matrix is not reported in public.
Disclosure of Invention
The technical problem solved by the invention is as follows: the defects of the prior art are overcome, the thermal spraying installation process of the thermal structure surface resistance strain gauge is provided, and the problem that the expansion of the ceramic matrix composite material and the resistance strain gauge is not matched easily at high temperature is solved.
The technical solution of the invention is as follows:
a thermal spraying installation process for a surface resistance strain gauge of a thermal structure comprises the following steps:
1) Carrying out surface treatment on a test area of a tested structure;
2) Carrying out plasma spraying treatment on a test area of a tested structure to obtain an insulating layer;
3) On the insulating layer, carrying out plasma spraying treatment on part of the grid wires of the resistance strain gauge for multiple times by using a mask to obtain a first coating;
4) On the first coating, carrying out plasma spraying treatment on the rest part of the resistance strain gauge grid wires for multiple times by using a mask to obtain a second coating;
5) Carrying out spraying treatment on the whole areas of the first coating and the second coating to obtain a third coating; the first coating, the second coating and the third coating jointly form a surface covering layer, and the fixed installation of the grid wire of the resistance strain gauge is completed.
Preferably: the surface treatment method in the step 1) specifically comprises the following steps: sand blasting treatment and cleaning treatment.
Preferably: the sand blowing treatment adopts 100-300 meshes of sand grains, the value range of the sand blowing pressure is 0.3-0.5 MPa, and the value range of the sand blowing time is 10-30 seconds.
Preferably: the sand blasting area is equal to 8-12 times of the fixed installation area of the grid wire of the resistance strain gauge.
Preferably, the area of the spraying area, i.e. the area of the insulating layer, of the plasma spraying treatment in the step 2) is equal to 3 to 8 times of the fixed installation area of the resistance strain grid wire.
Preferably, the spraying thickness of the plasma spraying treatment in the step 2), namely the thickness of the insulating layer, ranges from 0.04mm to 0.1mm.
Preferably: the method for obtaining the first coating in the step 3) specifically comprises the following steps:
31 Processing a plurality of hollowed grids on a mask, and pressing the resistance strain gauge grid wires on the insulating layer by using the mask, wherein the hollowed grids are used for exposing partial resistance strain gauge grid wires;
32 Carrying out plasma spraying treatment on part of the grid wires of the resistance strain gauge exposed in the hollowed-out grid for multiple times to obtain a first coating;
33 Heat treating the mask, and stripping the mask from the grid wire of the resistance strain gauge after the mask is softened.
Preferably: the exposed length of the grid wires of the resistance strain gauge in the step 31) is not less than one third of the total length.
Preferably: the first coating and the second coating are equal in thickness.
Preferably: the method for obtaining the second coating in the step 4) specifically comprises the following steps:
41 Processing a plurality of hollowed grids on the mask, and pressing the grid wires of the resistance strain gauge on the insulating layer by using the mask, wherein the hollowed grids are used for exposing the rest grid wires of the resistance strain gauge;
42 Carrying out plasma spraying treatment on the grid wires of the resistance strain gauge exposed in the hollow grid for multiple times to obtain a second coating;
43 Heat treating the mask, and stripping the mask from the grid wire of the resistance strain gauge after the mask is softened.
Preferably: 32) and 42), wherein the spraying times are not less than 3 times, each spraying time is not longer than 20 seconds, and the time interval between two adjacent spraying is not less than 10 seconds.
Preferably: the spraying areas of the multiple times of plasma spraying treatment in the steps 32) and 42) cover the hollow grid area of the mask.
Preferably: the plasma spraying treatment method in the steps 2), 3) and 4) comprises the following specific steps:
the plasma spraying treatment is carried out by adopting aluminum oxide powder, the spraying distance from a spray gun opening to a measured structure ranges from 80mm to 120mm, the spraying current ranges from 550A to 650A, the spraying voltage ranges from 55V to 65V, the spraying gas pressure ranges from 0.6 MPa to 0.8MPa, and the powder feeding amount ranges from 25L/min to 35L/min.
Preferably: the thickness of the surface covering layer ranges from 0.4mm to 0.6mm.
Preferably: after the step 5) of obtaining the third coating, the method further comprises the following steps: and welding and leading out the lead wire end connected with the grid wire of the resistance strain gauge, so that the grid wire of the resistance strain gauge is connected with signal acquisition equipment.
Compared with the prior art, the invention has the advantages that:
1) Compared with the sticking process of the resistance strain gauge, the plasma spraying installation process has no time-consuming processes such as glue layer baking and curing, so that the installation time of the resistance strain gauge is shortened from 8 hours consumed by the sticking process to 0.5 hour consumed by the spraying process, and the installation efficiency is greatly improved;
2) Compared with a handheld flame spraying process, the plasma spraying process can accurately control the spraying thickness through the combination setting of relevant parameters, and solves the problem that the spraying thickness is difficult to control because the flame spraying process completely depends on manual experience, so that the dispersity of strain test data is reduced;
3) The plasma spraying process is adopted, so that the spraying thickness of the insulating layer can be controlled within a very thin range (0.04 mm-0.1 mm), the coating is compact, the thermal expansion of the insulating layer caused at high temperature is very small, the strain can be effectively transferred, the strain testing precision is improved, and the risk of cracking of the adhesive layer caused by shrinkage in the baking and curing process of the pasting process is solved;
4) The adoption of the mask for spraying the resistance strain gauge in batches can solve the problem that the resistance strain gauge is damaged due to high temperature and high pressure of spraying air flow in a one-time spraying process.
5) In order to ensure that the surface temperature of the grid wire of the resistance strain gauge is lower than 250 ℃, a spraying programming process which is a cycle of spraying three times every time (the spraying time of each time is not longer than 20 seconds) and suspending for 10 seconds is adopted, so that the problem of damage of the resistance strain gauge caused by overhigh temperature in the spraying process is solved.
Drawings
FIG. 1 is a schematic diagram of a high temperature resistance strain gauge;
FIG. 2 is a schematic diagram of a mask structure;
FIG. 3 is a schematic view of a mask fixed resistance strain gauge;
FIG. 4 is a partial microarchitecture diagram of a test strain;
FIG. 5 is a process flow diagram of the present invention.
1-measured structure, 2-insulating layer, 3-resistance strain gauge grid wire, 4-surface covering layer, 5-lead terminal and 6-mask
Detailed Description
The thermal structure for the hypersonic aircraft is mostly ceramic matrix composite material, has the characteristics of brittle material, poor surface flatness, high roughness and certain pores, and causes the problem of surface oxidation at high temperature, the material has certain electrical conductivity, the thermal expansion coefficient is small (about 3-4 ppm/DEG C), the difference with the resistance strain gauge based on the metal grid wire is an order of magnitude, and the expansion mismatching is easy to occur at high temperature. The invention aims to provide a mounting process of a resistance strain gauge based on plasma spraying aiming at a novel composite material (namely a measured structure 1) with a thermal structure form of a ceramic matrix, wherein the resistance strain gauge mainly comprises a resistance strain gauge grid wire 3 and lead ends 5, the resistance strain gauge grid wire 3 is formed by winding a metal wire, and the lead ends 5 are two free ends of the metal wire. As shown in fig. 4, the resistance strain gauge is combined with a structure 1 to be tested to form a local microstructure for testing strain at high temperature (1100 ℃), which includes a test region of the structure to be tested, an insulating layer 2, a gate wire 3 of the resistance strain gauge, a surface covering layer 4 and a lead terminal 5.
The measured structure 1 is a novel ceramic-based composite material thermal structure, and sand blowing and cleaning treatment needs to be carried out on the surface of the measured structure 1 aiming at the characteristics of the measured structure 1 so as to be suitable for installation of the resistance strain gauge.
The insulating layer 2 plays a role in electrically insulating the electric resistance strain gauge grid wire 3 from the structure 1 to be tested, and test errors caused by electric conduction between the structure 1 to be tested and the electric resistance strain gauge grid wire 3 are avoided. Meanwhile, the insulating layer 2 needs to have characteristics of high shear modulus, small creep and the like, so that good strain transfer can be ensured at both normal temperature and high temperature.
The resistance strain gauge grid wire 3 is a core sensor sensitive to strain, and in order to avoid the resistance strain gauge from moving on the surface of the structure 1 to be measured during spraying installation, the resistance strain gauge grid wire 3 is fixed in batches by adopting a mask 6.
The surface covering layer 4 plays a role in fixing the grid wire 3 of the resistance strain gauge and protecting the outside, and prevents the grid wire 3 of the resistance strain gauge from being oxidized at high temperature (higher than 400 ℃).
The lead terminal 5 is fixed by using an adhesive tape in the installation process of the resistance strain gauge, and after the installation is finished, the grid wire 3 of the resistance strain gauge is connected with acquisition equipment through the lead terminal 5 to realize high-temperature strain test.
The mask 6 is formed by processing a Teflon adhesive tape, and a plurality of hollow grids are arranged in the middle and used for spraying the grid wires 3 of the resistance strain gauges in batches.
The spraying process of the resistance strain gauge is mainly based on a plasma spraying technology, and has the basic principle that spraying powder is sent into plasma arc flame flow to be heated to a molten or semi-molten state, and is sprayed and deposited on a grid wire 3 of the resistance strain gauge to form a compact surface covering layer 4, and the surface covering layer 4 and a tested structure 1 generate good bonding strength by virtue of the spraying process, so that the structure strain can be effectively transmitted at high temperature. Aiming at a novel composite material structure body, a substrate-free strain sensor which can resist 1100 ℃ is selected as a high-temperature resistance strain gauge, alumina powder (linear expansion is 5-6 ppm/DEG C, and the temperature is 1400 ℃) with the linear expansion coefficient matched with the tested structure 1 is selected as spraying powder, and as shown in figure 5, the specific spraying process is as follows:
1) Surface treatment: and carrying out sand blasting treatment on the surface of the tested structure 1, and roughening the surface of the test piece and increasing the spraying adhesion. Aiming at the characteristics of the novel composite material with a thermal structure form of a ceramic matrix, sand grains of 100-300 meshes are adopted, the sand blowing pressure is preferably in the range of 0.3-0.5 MPa, the sand blowing time is adjusted according to parameters such as the size of a test piece, the hardness of the material, the sand blowing pressure and the like, and the sand blowing time is usually in the range of 10-30 seconds. The sand blowing area is about 8-12 times of the bonding area of the grid wire 3 of the resistance strain gauge. And after the sand blowing is finished, cleaning the surface of the tested structure 1, and mainly removing the residual abrasive dust on the surface of the tested structure 1.
2) And (3) spraying the insulating layer 2 by adopting a plasma spraying process: spraying an insulating layer 2 on a test area on the surface of the tested structure 1 by adopting alumina powder; considering the effectiveness of strain transfer in a high-temperature environment (1100 ℃) and the insulation requirement of a sprayed layer (350M omega), the spraying area of the insulating layer 2 is about 3-8 times of the bonding area of the resistance strain grid wire 3, and the spraying thickness is about 0.04-0.1 mm; the specific spraying parameters are as follows: the spraying distance between the nozzle of the spray gun and the measured structure 1 is 80-120 mm, and the parameters of the plasma spraying equipment are as follows: the current is 550A-650A, the voltage is 55V-65V, the gas pressure is 0.6-0.8 MPa, and the powder feeding amount is 25-35L/min.
3) Fixed resistance strain gauge wire 3: placing the resistance strain gauge on the spraying insulating layer 2 of the tested structure 1 by using a professional scalpel blade and forceps to ensure that the resistance strain grid wire 3 is completely attached to the spraying insulating layer 2; the lead terminals 5 are attached to the structure 1 under test using an adhesive tape.
4) And (6) covering by using a mask: the one-time spraying process is very easy to damage the resistance strain gauge under the influence of the pressure and the temperature of the spraying airflow, so the mask 6 is adopted for batch spraying. The mask 6 is used for covering the grid wires 3 of the resistance strain gauges, and due to the fact that the mask 6 is provided with a plurality of hollow grids, part of the grid wires 3 of the resistance strain gauges can be exposed, and the length of the exposed grid wires 3 of the resistance strain gauges is not less than one third of the total length. Meanwhile, in order to avoid damaging other parts of the test piece in the high-temperature spraying process, a shielding adhesive tape is used for shielding and protecting the periphery of the sprayed resistance strain gauge.
5) Spraying the strain gauge for the first time to obtain a first coating: and (3) carrying out plasma spraying treatment on part of the electric resistance strain gauge grid wires 3 exposed in the hollowed-out grids, and adopting a spraying programming process which is a cycle of spraying three times every time (the spraying time of each time is not longer than 20 seconds) and pausing for 10 seconds in order to ensure that the surface temperature of the electric resistance strain gauge grid wires 3 is lower than 250 ℃ (so as to prevent the electric resistance strain gauge from being damaged).
In the spraying parameters, the powder feeding amount mainly controls the thickness of the coating, and the gas pressure is used for controlling the bonding strength of the sprayed coating and the tested structure 1. In order to ensure the spraying quality of the resistance strain gauge, the spraying parameters are set as follows: the spraying distance between the mouth of the spray gun and the resistance strain gauge is 80-120 mm, and the parameters of the plasma spraying equipment are as follows: the current is 550A-650A, the voltage is 55V-65V, the gas pressure is 0.6-0.8 MPa, and the powder feeding amount is 25-35L/min.
The spraying area is preferably covered by the hollow grid area of the mask 6, and the value range of the coating thickness is 0.1mm-0.2mm, so that the first coating and the insulating layer 2 of the tested structure 1 have good bonding strength.
6) First stripping of the mask 6: and heating the mask 6, wherein the temperature range of the heating treatment is 50-80 ℃. After the mask is softened, the mask is peeled off from the resistance strain gauge by using tweezers, so that the non-sprayed part of the grid wire 3 of the resistance strain gauge is subjected to spraying treatment.
7) Spraying the strain gauge for the second time to obtain a second coating: covering the first coating by using a new mask 6, exposing the grid wire 3 of the resistance strain gauge at the part which is not sprayed, and spraying the grid wire 3 of the resistance strain gauge, wherein the spraying parameters are as follows: the spraying distance between the mouth of the spray gun and the resistance strain gauge is 80-120 mm, and the parameters of the plasma spraying equipment are as follows: the current is 550A-650A, the voltage is 55V-65V, the gas pressure is 0.6-0.8 MPa, and the powder feeding amount is 25-35L/min. The area of the spray is preferably covered by the hollow grid region of the mask 6. The first coating and the second coating are equal in thickness.
8) Second stripping of the mask 6: and heating the mask 6, wherein the temperature of the heating is 50-80 ℃. After the mask is softened, it is peeled off from the resistance strain gauge using tweezers, exposing the first coating and the second coating.
9) Spraying a strain gauge for the third time to obtain a third coating; and (3) carrying out secondary spraying treatment on the whole areas of the first coating and the second coating until the third coating uniformly covers the whole resistance strain gauge grid wire 3, controlling the total thickness of the three-time spraying to be 0.4-0.6 mm, and forming a surface covering layer 4 by the first coating, the second coating and the third coating together.
10 After the spraying process is finished, the spraying quality is checked, and the resistance value of the resistance strain gauge and the insulation resistance between the grid wire 3 of the resistance strain gauge and the tested structure 1 are tested by a universal meter to determine whether the use requirements are met.
11 Lead bonding: and (3) welding and leading out a lead end 5 connected with the high-temperature lead and the resistance strain gauge grid wire 3 by adopting a spot welding mode, so that the resistance strain gauge grid wire 3 is connected with signal acquisition equipment.
12 The adhesive tape on the lead terminal 5 is removed.
The invention has the innovation point that a set of complete resistance strain gauge mounting process based on the plasma spraying technology is formed aiming at the novel composite material with the thermal structure form of ceramic matrix. Wherein, the high temperature resistant (1400 ℃) alumina spraying powder, the high temperature resistance strain gauge (resistant to 1100 ℃) and the corresponding plasma spraying process ensure that the mounted strain gauge can work normally under the high temperature environment of 1100 ℃.
Examples
In the embodiment, the tested structure 1 adopts a modified C/C composite material platelet (with the size of 100mm multiplied by 100 mm), and the thermal structure form is a novel ceramic-based composite material; the spraying powder is alumina powder (linear expansion 5.5 ppm/DEG C, temperature resistance 1400 ℃); the resistance strain gauge is a substrate-free sensor capable of resisting 1200 ℃, and the grid wire of the resistance strain gauge is 3mm multiplied by 8mm in size; the mask 6 has a size of 6mm × 12mm, and the specific spraying process is as follows:
1) Surface treatment: and carrying out sand blasting treatment on the surface of the tested structure 1, wherein 200-mesh sand is adopted, the sand blasting pressure is 0.4MPa, the sand blasting time is 15 seconds, and the sand blasting area is about 30mm multiplied by 80mm. And after sand blowing is finished, blowing and cleaning by using compressed air, and mainly removing residual abrasive dust on the surface.
2) Spraying an insulating layer: spraying an insulating layer 2 on a test area on the surface of the tested structure 1 by adopting plasma spraying equipment; the spray area of the insulating layer 2 was 15mm × 40mm, and the spray thickness was 0.05mm. Spraying parameters: the spraying distance between the nozzle of the spray gun and the measured structure 1 is 100mm, the parameters of the plasma spraying equipment are set to be 600A of current, 60V of voltage, 0.7MPa of gas pressure and 30L/min of powder feeding amount.
3) Fixing a strain gauge: placing the resistance strain gauge on a spraying insulating layer 2 of a tested structure 1 by using a professional scalpel blade and forceps to ensure that a grid wire 3 of the resistance strain gauge is completely attached to the tested structure 1; the lead terminals 5 are attached to the structure 1 under test using a high temperature adhesive tape.
4) And (6) covering by using a mask: the grid wire 3 of the resistance strain gauge is covered and fixed by using a mask 6, as shown in fig. 4, the length of the exposed grid wire 3 of the resistance strain gauge is half of the total length, and meanwhile, in order to avoid damaging other parts of a test piece in the high-temperature spraying process, the periphery of the sprayed resistance strain gauge needs to be shielded by using a shielding adhesive tape.
5) Spraying the strain gauge for the first time to obtain a first coating: and carrying out plasma spraying treatment on the exposed part of the grid wire 3 of the resistance strain gauge, wherein the spraying parameters are set as follows: the spraying distance is 100mm, the current is 600A, the voltage is 60V, the gas pressure is 0.7MPa, and the powder feeding amount is 30L/min. The spraying area covers the hollow grid area of the mask 6, and the spraying thickness is 0.1mm. In order to ensure that the surface temperature of the grid wire 3 of the resistance strain gauge is lower than 250 ℃, a programmed spraying process of spraying three times per time (the spraying time of each time is not longer than 20 seconds) and pausing for 10 seconds to form a cycle is adopted.
6) First stripping of the mask 6: after the first spraying, when the mask temperature is reduced to 70 ℃, the mask is peeled off from the resistance strain gauge by using tweezers.
7) Spraying the strain gauge for the second time to obtain a second coating: covering the first coating by using a new mask 6, exposing the grid wire 3 of the resistance strain gauge at the part which is not sprayed, and spraying the grid wire 3 of the resistance strain gauge, wherein the spraying parameters are as follows: the spraying distance is 100mm, the current is 600A, the voltage is 60V, the gas pressure is 0.7MPa, and the powder feeding amount is 30L/min. The spraying area covers the hollow grid area of the mask 6, and the spraying thickness is 0.1mm. After the spraying is finished, the method of the step 6) is adopted to strip the mask.
8) Spraying the strain gauge for the third time to obtain a third coating: and (4) spraying the whole areas of the first coating and the second coating again, wherein the spraying parameters are the same as those in the step (7) until the spraying layer uniformly covers the whole resistance strain grid wire 3. The total thickness of the three spraying is controlled to be 0.5mm, and the first coating, the second coating and the third coating jointly form the surface covering layer 4. The surface coating 4 has an area of 5mm × 12mm.
9) And after spraying, carrying out spraying quality inspection, and testing the resistance value of the resistance strain gauge and the insulation resistance between the grid wire 3 of the resistance strain gauge and the tested structure 1 by adopting a universal meter to confirm that the use requirements are met.
10 Lead bonding: and (3) welding and leading out the high-temperature lead and the lead end 5 connected with the grid wire 3 of the resistance strain gauge by adopting a spot welding mode, so that the grid wire 3 of the resistance strain gauge is connected with a signal acquisition device.
11 Remove the adhesive tape from the lead terminal 5.
The invention relates to a force-heat composite environmental test testing technology, and provides a resistance strain gauge mounting process based on plasma spraying aiming at the difficult problem of testing the surface resistance strain of a novel ceramic-based composite material thermal structure (namely a tested structure 1).
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above. The embodiments of the present application and the technical features in the embodiments may be combined with each other without conflict.
Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.
Claims (15)
1. A thermal spraying installation process for a surface resistance strain gauge of a thermal structure is characterized by comprising the following steps:
carrying out surface treatment on a test area of the tested structure (1);
carrying out plasma spraying treatment on a test area of the tested structure (1) to obtain an insulating layer (2);
on the insulating layer (2), carrying out plasma spraying treatment on part of the resistance strain gauge grid wires (3) for multiple times by using a mask (6) to obtain a first coating;
on the first coating, carrying out plasma spraying treatment on the rest parts of the resistance strain gauge grid wires (3) for multiple times by using a mask (6) to obtain a second coating;
carrying out spraying treatment on the whole areas of the first coating and the second coating to obtain a third coating; the first coating, the second coating and the third coating jointly form a surface covering layer (4) to finish the fixed installation of the grid wire (3) of the resistance strain gauge.
2. The thermal spraying installation process for the surface resistance strain gauge of the thermal structure as claimed in claim 1, wherein: the surface treatment method specifically comprises the following steps: sand blasting treatment and cleaning treatment.
3. A thermal spray mounting process for a thermal structure surface resistance strain gauge according to claim 2, wherein: the sand blowing treatment adopts 100-300 meshes of sand grains, the value range of the sand blowing pressure is 0.3-0.5 MPa, and the value range of the sand blowing time is 10-30 seconds.
4. A thermal spray mounting process for a thermal structure surface resistance strain gauge according to claim 2, wherein: the sand blasting area is equal to 8-12 times of the fixed installation area of the resistance strain gauge grid wire (3).
5. A thermal spray mounting process for a thermal structure surface resistance strain gauge according to claim 1, wherein: the area of the insulating layer (2) is equal to 3-8 times of the fixed installation area of the resistance strain grid wire (3).
6. A thermal spray mounting process for a thermal structure surface resistance strain gauge according to claim 1, wherein: the thickness range of the insulating layer (2) is 0.04mm-0.1 mm.
7. The thermal spraying installation process for the surface resistance strain gauge of the thermal structure as claimed in claim 1, wherein: the method for obtaining the first coating specifically comprises the following steps:
processing a plurality of hollowed grids on the mask (6), and pressing the resistance strain gauge grid wires (3) on the insulating layer (2) by using the mask (6), wherein the hollowed grids are used for exposing part of the resistance strain gauge grid wires (3);
carrying out plasma spraying treatment on part of the exposed grid wires (3) of the resistance strain gauge in the hollowed grid for multiple times to obtain a first coating;
and heating the mask (6), and peeling the mask (6) from the electric resistance gauge grid wire (3) after the mask (6) is softened.
8. A thermal spray mounting process for a thermostructural surface resistance strain gauge according to claim 7, characterised in that: the exposed length of the grid wire (3) of the resistance strain gauge is not less than one third of the total length.
9. A thermal spray mounting process for a thermal structure surface resistance strain gauge according to claim 1, wherein: the first coating and the second coating are equal in thickness.
10. A thermal spray mounting process for a thermal structure surface resistance strain gauge according to claim 1, wherein: the method for obtaining the second coating specifically comprises the following steps:
processing a plurality of hollowed grids on the mask (6), and pressing the resistance strain gauge grid wires (3) on the insulating layer (2) by using the mask (6), wherein the hollowed grids are used for exposing the rest of the resistance strain gauge grid wires (3);
carrying out plasma spraying treatment on the resistance strain gauge grid wires (3) exposed in the hollow grid for multiple times to obtain a second coating;
and heating the mask (6), and peeling the mask (6) from the resistance strain gauge grid wire (3) after the mask (6) is softened.
11. A thermal spray mounting process for a thermostructural surface resistance strain gauge according to claim 7 or 10, characterized in that: in the multiple plasma spraying treatment, the spraying times are not less than 3, each spraying time is not longer than 20 seconds, and the time interval between two adjacent spraying times is not less than 10 seconds.
12. A thermal spray mounting process for a thermal structure surface resistance strain gauge according to claim 7 or 10, wherein: the spraying area of the multiple times of plasma spraying treatment covers the hollow grid area of the mask (6).
13. A thermal spray mounting process for a thermal structure surface resistance strain gauge according to claim 1, wherein: the plasma spraying treatment method specifically comprises the following steps:
the method is characterized in that the alumina powder is adopted for plasma spraying treatment, the spraying distance from a spray gun opening to a measured structure (1) ranges from 80mm to 120mm, the spraying current ranges from 550A to 650A, the spraying voltage ranges from 55V to 65V, the spraying gas pressure ranges from 0.6 MPa to 0.8MPa, and the powder feeding amount ranges from 25L/min to 35L/min.
14. The thermal spraying installation process for the surface resistance strain gauge of the thermal structure as claimed in claim 1, wherein: the thickness of the surface covering layer (4) ranges from 0.4mm to 0.6mm.
15. A thermal spray mounting process for a thermal structure surface resistance strain gauge according to claim 1, wherein: after the third coating is obtained, the method further comprises the following steps: and welding and leading out a lead end (5) connected with the resistance strain gauge grid wire (3) to enable the resistance strain gauge grid wire (3) to be connected with a signal acquisition device.
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Cited By (1)
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| CN116637789A (en) * | 2023-05-26 | 2023-08-25 | 中国航空工业集团公司沈阳空气动力研究所 | Electric heating coating suitable for wind tunnel test model with complex appearance and large curvature surface and preparation method thereof |
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| CN116637789A (en) * | 2023-05-26 | 2023-08-25 | 中国航空工业集团公司沈阳空气动力研究所 | Electric heating coating suitable for wind tunnel test model with complex appearance and large curvature surface and preparation method thereof |
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