Intelligent metal material with self-sensing function and preparation method thereof

Abstract

The invention relates to an intelligent metal material with a self-sensing function and a preparation method thereof, and belongs to the field of structural health monitoring. The method comprises the following basic steps: firstly, preparing a multifunctional quasi-distributed optical fiber sensor based on a spiral structure by adopting a partial dual-core optical fiber; secondly, carrying out Al coating metallization on the sensor so as to improve the integration level and compatibility of the sensor and a metal matrix; then, when the metal composite material Al / Ti is consolidated layer by layer by using high-power ultrasonic consolidation equipment, embedding the metalized optical fiber sensor into the metal composite material Al / Ti; and finally, the metal foil is solidified through ultrasonic lamination. According to the method, metal is made to flow plastically instantly by means of energy released by ultrasonic consolidation, the optical fiber is embedded into the metal, metal atoms are driven by ultrasonic vibration energy to diffuse on an interface to form new valence bonds, microscopic combination of the optical fiber and the metal is achieved, and signal transmission is almost free of attenuation. The metal performance and the optical fiber sensing function are combined, and a new scheme is provided for metal structure health monitoring.

Description

Technical Field

[0001] The present invention relates to an intelligent metal material with self - sensing function and its preparation method, belonging to the field of structural health monitoring. Background Art

[0002] Intelligent metal structural materials are essential key materials for the safe operation of aircraft. Aircraft structural health monitoring technology has great potential in improving the safety and reliability level of aircraft structures and reducing maintenance costs, and will bring a revolutionary impact on the future aircraft structural design concept. In the structural design of aerospace aircraft, lightweight metal structures such as metal laminated composite structures and sandwich honeycomb core structures are generally adopted at present. For example, sandwich honeycomb core structures are usually made of light metals such as titanium (Ti) and aluminum (Al) to improve flight speed and stability. With the rapid development of aerospace science and technology, requirements for the metal structures of aircraft have been put forward in terms of light weight, high reliability, high maintainability, and high survivability. In order to meet these requirements, it is necessary to increase the intelligence of metal materials and use intelligent metal structural materials. In aerospace intelligent structures, sensors are usually embedded in light metal laminated composite components for on - line detection of load, strain, temperature, crack, etc. and prediction of the safety of aircraft. At present, the main method is to paste optical fibers on the surface of the matrix structure or bury them in the matrix structure to realize structural health monitoring such as material structure strain, temperature, bending, and damage. The combination of optical fiber and metal matrix still belongs to physical combination, and the existing macroscopic gaps have attenuation and delay phenomena on the transmitted signals, and the optical properties of optical fibers are greatly affected after consolidation. Embedding optical fiber sensors into metals with high hardness and high melting point is the main technical difficulty in realizing optical fiber sensing inside metals. Aiming at the technical bottleneck problem of embedding optical fiber sensors in metals at present, it is necessary to find a suitable embedding method to change the macroscopic assembly of optical fiber and metal matrix into microscopic combination at the atomic and molecular levels, so as to obtain a more homogeneous metal intelligent material and realize efficient transmission of signals from metal to optical fiber without attenuation and zero delay.

[0003] Ultrasonic consolidation technology uses metal foils as raw materials. It utilizes the energy of high - frequency vibration of ultrasonic waves to make two metal surfaces rub against each other to form fusion between atomic layers. Then, through integration with numerical control machining, the milling process in the consolidation forming process of metal foils is completed, and finally metal laminated material components with required geometric dimensions and accuracies are prepared. During the ultrasonic consolidation process, the metal is in a solid state without melting, which will not affect the original properties of the metal. During the consolidation process, sensors, electronic circuits, brakes, etc. can be completely embedded in a dense metal structure without causing damage to the sensor components. Therefore, ultrasonic consolidation is very suitable for the printing of "intelligent materials" and the forming of "intelligent structures". Summary of the Invention

[0004] The object of the present invention is to solve the problems existing in the current technology, and for this purpose, an intelligent metal material with self-sensing function and its preparation method are provided.

[0005] An intelligent metal material with self-sensing function and its preparation method according to the present invention, as Figure 1 shown, includes the following steps:

[0006] The first step is to prepare a spiral-structure-based partial double-core multi-functional quasi-distributed optical fiber sensor;

[0007] The second step is to metallize the coating of the quasi-distributed optical fiber sensor;

[0008] The third step is to embed the optical fiber sensor into the metal matrix to realize the integration of the optical fiber and the metal matrix;

[0009] Furthermore, the specific steps of the preparation of the spiral-structure-based partial double-core multi-functional quasi-distributed optical fiber sensor are as follows:

[0010] 1) Selection of optical fiber. In this patent, an optical fiber with a diameter of 125 μm and a core diameter of 8 μm is selected, with the same refractive index distribution as that of a common standard single-mode optical fiber. It is required that at a distance of 20 μm from the center dot of the optical fiber, there is another core in the cladding, which is called a partial double-core optical fiber (as Figure 1 (a) shown). The type of optical fiber is not limited to this, and it can be a partial triple-core optical fiber or a four-core optical fiber, etc.

[0011] 2) Preparation of the large spiral structure of the optical fiber. The large spiral single-pitch torsion structure is prepared by the thermal melting method. The heating device mainly consists of an electrode, a precision displacement stage, and a rotating electrode, as Figure 2 shown. One end of the optical fiber is fixed with a clamp, and the other end is fixed on the rotating motor. The electrode discharges while moving on the precision displacement stage and twists the optical fiber at the same time. By controlling the twisting speed, the moving distance of the displacement stage, and the discharging time, the pitch and total length of the spiral torsion structure can be controlled. Its torsion structure is as Figure 3 (b) shown.

[0012] 3) Preparation of the FBG array. In this application, the defocus mask plate method is used to prepare FBG in the spiral torsion area of the partial double-core optical fiber. The multi-core optical fiber is placed on the defocus plane of the focusing lens, and FBG can be inscribed on multiple cores at the same time. The structural schematic diagram is as Figure 4 shown.

[0013] For the side core, the changes in the central wavelength of FBG caused by torsion, bending, temperature, and strain can be expressed as:

[0014]

[0015] where L and L εare the edge core lengths before and after twisting, respectively; Λ helix is the pitch of the helical twist structure; r is the distance from the central core to the edge core; θ t is the additional twist angle per unit pitch; n side,0 is the refractive index of the helical edge core before applying twist; τ0 is the twist already cured in the edge core; τ is the applied twist, and ± depends on the direction of the applied twist; P 11 and P 12 are the Pockels piezoelectric coefficients of the photoelastic tensor; ρ is the radius of curvature; θ b is the angle between the bending direction and the Y-axis; θ i is the angle between the edge core and the Y-axis. It can be seen from formula (1) that the twist sensitivity of the sensor depends on the ratio of the pitch Λ helix of the twist structure and the distance r from the central core to the edge core, and the twisted multi-core fiber FBG can distinguish the direction of twist; the bending sensitivity depends on the distance r from the center to the edge core. Therefore, for a determined r and different pitches Λ helix result in different sensitivities. For the central core, the change in the central wavelength of the FBG caused by these sensing parameters can be expressed as:

[0016]

[0017] It can be seen from formulas (1) and (2) that the central FBG is insensitive to twist and bending, and is only sensitive to temperature and strain, while the FBG of the edge core is sensitive to all the above sensing parameters.

[0018] Furthermore, the specific steps of the preparation process of the metalized coating of the quasi-distributed fiber optic sensor are as follows:

[0019] 1) Remove the coating: Soak the prepared fiber optic sensor array in acetone for about 20 minutes, and wipe off the coating on the fiber with an alcohol cotton cloth.

[0020] 2) Remove oil stains: Clean the fiber optic sensor after removing the coating with ultrasonic alcohol, clean the oil stains on the fiber surface for 10 minutes, and then clean it with ultrasonic distilled water for 10 minutes.

[0021] 3) Metallization: Prepare a metal aluminum film by magnetron sputtering coating process, and perform magnetron sputtering on the fiber in a vacuum state. It is required that the diameter of the fiber after coating is 170 ± 5 μm.

[0022] Furthermore, the fiber optic sensor is embedded in the metal matrix to realize the integration of the fiber optic and the metal matrix. The specific steps of the material selection and cleaning process are as follows:

[0023] 1) Select aluminum foil with a thickness of 200 μm, and its model is Al-1100. The percentage contents are as follows: Al: 99, Mn: ≤0.035, Zn: ≤0.01, Cu ≤0.05, Si ≤0.45, Fe ≤0.35; select titanium foil with a thickness of 200 μm, and its percentage contents are as follows: Ti: 99, Fe: ≤0.25, C: ≤0.1, N ≤0.03, H ≤0.0015, O ≤0.02; use the two kinds of foils as the base materials.

[0024] 2) First, cut Al and Ti foils with a length of 100 cm, and wipe their surfaces with cotton cloth respectively for degreasing treatment.

[0025] 3) Clean the surfaces of the foils with non-woven fabric dipped in alcohol to keep the surfaces of the foils clean.

[0026] 4) Use a laser to etch a small "V"-shaped groove on the Ti foil, with a depth of about 5 μm.

[0027] For an intelligent metal material with self-sensing function and its preparation method according to the present invention, it is characterized in that: in step three, the steps of ultrasonic consolidation of the intelligent metal material are as follows (as Figure 5 shown):

[0028] 1) Select a metal plate with a thickness of 4 cm as the substrate for ultrasonic consolidation.

[0029] 2) First, set the first layer as the Ti foil and fix its two ends on the substrate. Then place the metallized fiber optic sensor in the V-shaped groove, and keep the optical fiber in a just-straightened state, and fix both ends. Place the third layer of metal Al foil on the metallized fiber, and fix one end of it; then place a metal Ti layer on the third layer. Set the ultrasonic consolidation parameters, the ultrasonic amplitude is set to 28 μm - 30 μm; the ultrasonic pressure is set to 1800 N - 2000 N; the consolidation speed is 25 - 30 mm / s, and the heating temperature of the substrate is 190 °C.

[0030] 3) Start the device, and the probe for ultrasonic consolidation rolls at a preset speed, and at the same time, high-frequency ultrasonic vibration is carried out through the energy transmitted by the transducer. According to the set pressure and ultrasonic amplitude, the welding probe rolls over the following metal foils, so as to consolidate Al, Ti, and the fiber optic sensor together to obtain a composite intelligent metal material with a sandwich structure.

[0031] For an intelligent metal material with self-sensing function and its preparation method proposed by the present invention, it is characterized in that: atomic diffusion occurs between the metallized fiber optic sensor and the upper and lower layer metals, realizing the combination of the microscopic mechanism, so that there is no any macroscopic gap between the optical fiber and the metal matrix, as Figure 5 shown.

[0032] An intelligent metal material with self - sensing function and its preparation method according to the present invention are characterized in that the excellent properties of Ti and Al metal materials are effectively combined with the optical fiber sensing function, and the material has the ability of self - sensing.

[0033] An intelligent metal material with self - sensing function and its preparation method according to the present invention are characterized in that this intelligent metal material can realize the simultaneous measurement of multiple parameters, such as: measurement of vector bending, measurement of vector torsion, measurement of strain, temperature measurement, etc.

[0034] Advantages of the present invention

[0035] A new method is proposed in which an optical fiber sensor can be embedded in a metal at normal temperature and pressure. The ultrasonic consolidation technology is used to embed an optical fiber sensor with a metal coating during the forming of the metal structure. Utilizing the high - frequency ultrasonic vibration energy of ultrasonic waves to promote the mutual diffusion and combination of metal atoms at the interface to form new valence bond combinations. It can solve the problem that there are macroscopic gaps in the traditional method of embedding an optical fiber sensor into a metal by gluing or encapsulation, resulting in signal attenuation, and provides a new method for realizing the microscopic combination of an optical fiber and a metal.

[0036] The microscopic combination of a metallized optical fiber sensor and a metal matrix is realized. The optical fiber with a metal coating is embedded in the metal matrix, and the combination of the optical fiber and the metal matrix changes from macroscopic assembly to microscopic combination at the atomic and molecular levels, thereby obtaining a more homogeneous metal intelligent material and enabling efficient transmission of signals from the metal to the optical fiber without attenuation and zero delay.

[0037] A new type of metal intelligent material is obtained in which an optical fiber sensor and a metal are microscopically combined and can realize the simultaneous measurement of multiple parameters. An optical fiber sensor integrated with a fiber Bragg grating (FBG) array based on a spiral structure is embedded in the metal matrix, enabling the metal to have the ability of self - sensing and monitoring. The use of an optical fiber sensor with a metal coating embedded in the metal matrix lays a foundation for realizing the integration degree, compatibility degree, optimized sensing ability, and improving the sensitivity and accuracy of the metal intelligent material. Description of the drawings

[0038] Figure 1 Schematic diagram of the basic structure of the present invention

[0039] Figure 2 Schematic diagram for the preparation of a hot - melt spiral structure

[0040] Figure 3 Microstructure diagram of a polarization - maintaining twin - core fiber (a) Cross - sectional micrograph (b) Side view of a single - helix structure

[0041] Figure 4Schematic diagram of the FBG array of a partial dual-core fiber based on a spiral structure

[0042] Figure 5 Schematic diagram of the ultrasonic consolidation process Specific implementation manners

[0043] The present invention will be further described below in conjunction with the accompanying drawings and examples. The following embodiments are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0044] Embodiment 1

[0045] An intelligent metal material with self-sensing function and its preparation method proposed in this embodiment include the following steps:

[0046] Step 1: In this patent, a partial dual-core fiber with a fiber diameter of 125 μm, a core diameter of 8 μm, and the same refractive index distribution as that of a common standard single-mode fiber is selected. There is another core at a distance of 20 μm from the center dot of the fiber. Then, a large spiral single-pitch torsion structure is prepared by using the thermal melting method. The heating device mainly consists of an electrode, a precision displacement stage, and a rotating electrode. One end of the fiber is fixed by a clamp, and the other end is fixed on a rotating motor. The electrode discharges while moving on the precision displacement stage and twists the fiber at the same time. By controlling the twisting speed, the moving distance of the displacement stage, and the discharging time, the pitch and total length of the spiral torsion structure can be controlled, as Figure 2 shown. For the fiber optic sensor with a large spiral structure prepared, FBG etching is carried out. In this application, the defocus mask plate method is used to prepare FBG in the spiral torsion region of the partial dual-core fiber. The multi-core fiber is placed on the defocus plane of the focusing lens, and FBG can be written on multiple cores simultaneously.

[0047] Step 2. In this patent, the prepared fiber optic sensor array is soaked in acetone for about 20 minutes, and the coating on the fiber is wiped off with an alcohol cotton cloth. The fiber optic sensor after removing the coating is cleaned with ultrasonic alcohol to clean the oil stains on the fiber surface for 10 minutes, and then cleaned with ultrasonic distilled water for 10 minutes. The metal aluminum film is prepared by using the magnetron sputtering coating process. The fiber is magnetron sputtered in a vacuum state, and it is required that the diameter of the fiber after coating is 170 ± 5 μm.

[0048] In step 3, an aluminum foil with a thickness of 200 μm is selected, and its model is Al-1100. The percentage contents are as follows: Al: 99, Mn: ≤0.035, Zn: ≤0.01, Cu ≤0.05, Si ≤0.45, Fe ≤0.35; a titanium foil with a thickness of 200 μm is selected, and its percentage contents are as follows: Ti: 99, Fe: ≤0.25, C: ≤0.1, N ≤0.03, H ≤0.0015, O ≤0.02; the two foils are used as the base materials; first, cut Al and Ti foils with a length of 100 cm, and wipe their surfaces with cotton cloth for degreasing treatment. Clean the surfaces of the foils with non-woven fabric dipped in alcohol to keep the surfaces of the foils clean. Use a laser to etch a small "V"-shaped groove on the Ti foil, with a depth of about 5 μm.

[0049] In step 4, a 4-cm-thick metal plate is selected as the substrate for ultrasonic consolidation. First, set the first layer as the Ti foil and fix its two ends on the substrate. Then place the metallized fiber optic sensor in the V-shaped groove, and keep the optical fiber in a just-straightened state and fix both ends. Place the third layer of metal Al foil on the metallized optical fiber and fix one end of it; then place a metal Ti layer on the third layer. Set the ultrasonic consolidation parameters. The ultrasonic amplitude is set to 28 μm to 30 μm; the ultrasonic pressure is set to 1800 N to 2000 N; the consolidation speed is 25 to 30 mm / s, and the substrate heating temperature is 190 °C. Start the device, and the probe for ultrasonic consolidation rolls at a preset speed, and at the same time, high-frequency ultrasonic vibration is carried out through the energy transmitted by the transducer. According to the set pressure and ultrasonic amplitude, the welding probe rolls over the underlying metal foil, thereby consolidating Al, Ti, and the fiber optic sensor together to obtain a composite intelligent metal material with a sandwich structure.

[0050] In step 5, during the process of layer-by-layer consolidation of the metal foils in step 4, the required sensing elements can be embedded according to actual needs to prepare a metal component with sensing functions. The metal intelligent material embedded with the metallized fiber optic sensor is used to prepare aircraft materials to form a metal intelligent material that can self-perceive and self-monitor.

[0051] The present invention can be outlined in other specific forms that do not violate the spirit or main features of the present invention. Therefore, the above-mentioned embodiments of the present invention can only be considered as illustrative of the present invention and cannot limit the present invention. The claims point out the scope of the present invention, while the above description does not point out the scope of the present invention. Therefore, any changes within the meaning and scope equivalent to the claims of the present invention should be considered as included within the scope of the claims.

Claims

1. An intelligent metal material with self-perception function and its preparation method, characterized in that, It includes the following steps: Step 1: Preparation of a partial double-core multifunctional quasi-distributed optical fiber sensor based on a spiral structure; Step 2: Metallization coating of the quasi-distributed optical fiber sensor; Step 3: Embedding the optical fiber sensor into a metal matrix to realize the integration of the optical fiber and the metal matrix.

2. The intelligent metal material with self-sensing function and its preparation method according to claim 1, characterized in that: In Step 1, the specific preparation process is as follows: 1) Selection of optical fiber. In this patent, an optical fiber with a diameter of 125 μm and a core diameter of 8 μm is selected, having the same refractive index distribution as a common standard single-mode optical fiber. It is required that at a distance of 20 μm from the center dot of the optical fiber, there is another core in the cladding, which is called a partial double-core optical fiber. The optical fiber type is not limited to this, and it can be a partial triple-core optical fiber or a four-core optical fiber, etc. 2) Preparation of the large spiral structure of the optical fiber. The hot melting method is used to prepare a large spiral single-pitch torsion structure. The heating device mainly consists of an electrode, a precision displacement stage, and a rotating electrode. One end of the optical fiber is fixed by a clamp, and the other end is fixed on a rotating motor. The electrode discharges while moving under the control of the precision displacement stage and twists the optical fiber at the same time. By controlling the twisting speed, the moving distance of the displacement stage, and the discharging time, the pitch and total length of the spiral torsion structure can be controlled. 3) Preparation of the FBG array. In this application, the defocus mask plate method is used to prepare FBGs in the spiral torsion region of the partial double-core optical fiber. The multi-core optical fiber is placed on the defocus plane of the focusing lens, and FBGs can be inscribed on multiple cores simultaneously.

3. The intelligent metal material with self-sensing function and its preparation method according to claim 1, characterized in that: In Step 2, the specific preparation process is as follows: 1) Removal of the coating layer: Soak the prepared optical fiber sensor array in acetone for about 20 minutes, and wipe off the coating layer on the optical fiber with an alcohol cotton cloth. 2) Removal of oil stains: Clean the optical fiber sensor after removing the coating layer with ultrasonic alcohol, clean the oil stains on the surface of the optical fiber for 10 minutes, and then clean it with ultrasonic distilled water for 10 minutes. 3) Metallization: Use the magnetron sputtering coating process to prepare a metal aluminum film, and perform magnetron sputtering on the optical fiber in a vacuum state. It is required that the diameter of the optical fiber after coating is 170 ± 5 μm.

4. The intelligent metal material with self-sensing function and its preparation method according to claim 1, characterized in that: In Step 3, the material selection and cleaning process are as follows: 1) Select aluminum foil with a thickness of 200 μm, and its model is Al-1100. The content percentages are as follows: Al: 99, Mn: ≤0.035, Zn: ≤0.01, Cu ≤0.05, Si ≤0.45, Fe ≤0.35; select titanium foil with a thickness of 200 μm, and its content percentages are as follows: Ti: 99, Fe: ≤0.25, C: ≤0.1, N ≤0.03, H ≤0.0015, O ≤0.02; use the two kinds of foil materials as the matrix materials; 2) First, cut Al and Ti foils with a length of 100 cm, and wipe their surfaces with a cotton cloth for oil stain removal treatment. 3) Clean the surface of the foil with a non-woven fabric dipped in alcohol to keep the surface of the foil clean. 4) Use a laser to etch a "V"-shaped small groove on the Ti foil, with a depth of about 5 μm.

5. A smart metal material with self-sensing function and its preparation method according to claim 1, characterized in that: In Step 3, the steps of ultrasonic consolidation of intelligent metal materials are as follows: 1) Select a 4-cm-thick metal plate as the substrate for ultrasonic consolidation. 2) First, set the first layer as a Ti foil and fix both ends of it on the substrate. Then, place the metallized fiber optic sensor in the V-groove, keep the optical fiber in a just-straightened state, and fix both ends. Place a third-layer metal Al foil on the metallized fiber optic, and fix one end of it; then place a metal Ti layer on the third layer. Set the ultrasonic consolidation parameters, with the ultrasonic amplitude set to 28 μm to 30 μm; the ultrasonic pressure set to 1800 N to 2000 N; the consolidation speed to 25 to 30 mm / s, and the substrate heating temperature to 190 °C. 3) Start the device. The probe for ultrasonic consolidation rolls at a preset speed, and at the same time, high-frequency ultrasonic vibration is carried out through the energy transmitted by the transducer. According to the set pressure and ultrasonic amplitude, the welding probe rolls over the underlying metal foil, thereby consolidating Al, Ti, and the fiber optic sensor together to obtain a composite intelligent metal material with a sandwich structure.

6. The intelligent metal material with self-perception function and its preparation method according to claim 1, characterized in that: Atomic diffusion occurs between the metallized fiber optic sensor and the upper and lower layer metals, achieving a combination at the microscopic mechanism level, such that there are no any macroscopic gaps between the optical fiber and the metal matrix.

7. A kind of intelligent metal material with self-sensing function and its preparation method according to claim 1, characterized in that: The excellent properties of Ti and Al metal materials are effectively combined with the fiber optic sensing function, and the material has the ability of self-sensing.

8. A kind of intelligent metal material with self-sensing function and its preparation method according to claim 1, characterized in that: This intelligent metal material can achieve simultaneous measurement of multiple parameters, such as: measurement of vector bending, measurement of vector torsion, measurement of strain, temperature measurement, etc.

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