CN116818025B - Step metal-coated fiber grating high-temperature vibration composite sensor and monitoring method - Google Patents

Abstract

The invention provides a high-temperature vibration composite sensor of a step metal coating fiber bragg grating and a monitoring method, comprising a shell, wherein two first through holes are formed in the side surface of the shell in the axial extending direction, and the two first through holes are communicated with the inside of the shell; the two ends of the shell are respectively a connecting end and an extending end; the vibration sensing module is arranged in the shell, one end of the vibration sensing module is fixedly connected with the inner surface of the connecting end, and the other end of the vibration sensing module extends along the axial direction of the shell; at least one pair of bosses are arranged on the vibration sensing module; the optical fiber sensing detection module is suspended in a tensioning manner in at least one pair of bosses and a spacing area thereof, and two ends of the optical fiber sensing detection module extending in the axial direction are respectively wound and pass through a first through hole with the largest distance with the bosses and extend outwards; the optical fiber sensing detection module is characterized in that the surfaces of the optical fiber sensing detection module, which are contacted with at least one pair of bosses, and the surfaces of the optical fiber sensing detection module, which are penetrated in the two first through holes, are respectively provided with a first metal coating, and the first metal coatings are fixedly connected with the inner surfaces of at least one pair of bosses or the two first through holes.

Description

Step metal-coated fiber grating high-temperature vibration composite sensor and monitoring method

Technical field

The invention relates to the technical field of optical fiber sensing and detection equipment, and in particular to a step metal-coated fiber grating high-temperature vibration composite sensor and a monitoring method.

Background technique

In recent years, temperature and vibration measurement at high temperatures have been widely used in aerospace, energy industry, automobile industry and other fields. Harsh thermal and vibration environments will cause a series of problems, such as thermal fatigue, thermal shock, etc. These problems will reduce the reliability of mechanical equipment, shorten their lifespan, and may cause production shutdowns and increased maintenance costs. Therefore, In order to ensure production safety, there is an increasing demand for real-time monitoring of temperature and vibration in high-temperature environments.

Traditional electrical sensors have problems such as weak anti-electromagnetic interference capabilities, poor linear output at high temperatures, low reliability, and single measurement signals. Compared with fiber optic sensors, they have outstanding advantages, such as being free from electromagnetic interference, high operating temperature, enabling distributed multi-point measurement, and easy to implement multi-signal measurement. At present, high-temperature vibration composite sensors based on fiber gratings are applicable to low temperatures and have complex structures, making it difficult to meet the needs for simultaneous monitoring of temperature and vibration signals in high-temperature environments.

In order to solve the above problems, it is very necessary to design step metal-coated fiber grating high-temperature vibration composite sensors and monitoring methods, taking into account simultaneous sensing measurements of high-temperature and vibration composite scenarios.

Contents of the invention

In view of this, the present invention proposes a step metal-coated fiber grating high-temperature vibration composite sensor and a monitoring method that can simultaneously monitor high-temperature and vibration composite scenarios.

The technical solution of the present invention is implemented as follows:

On the one hand, the present invention provides a step metal-coated fiber grating high-temperature vibration composite sensor, including:

A shell with a hollow cavity inside;

A vibration sensing module, with one end fixedly provided on the inner surface of the housing, and the other end extending along the axial direction of the housing and provided with at least one pair of bosses, at least one pair of bosses facing each other and arranged at intervals;

The optical fiber sensing and detection module is tensioned and suspended on the at least one pair of bosses and their spacing areas, and the two ends of the optical fiber sensing and detection module also pass through the housing and extend outward;

Wherein, the surface of the optical fiber sensing detection module in contact with at least one pair of bosses and the surface passing through the housing are both provided with a first metal plating layer, and the first metal plating layer is also fixedly connected to at least one pair of bosses or the housing.

Based on the above technical solution, preferably, the vibration sensing module further includes a base, two first connection parts, two second connection parts and two inertial mass blocks; the two ends in the axial extension direction of the housing are respectively connected end and protruding end;

The base is fixedly arranged on the inner surface of the connecting end, and the other end extends along the axial direction of the housing;

Two first connecting parts are spaced apart from each other on the end surface of the base away from the connecting end. One end of the two first connecting parts is fixedly connected to the base, and the other end of the two first connecting parts are respectively along the axial direction and radial direction of the housing. extend;

The two second connecting parts are respectively hinge-connected to the ends of the two first connecting parts away from the base; the two second connecting parts also extend along the radial direction and the axial direction of the housing; the two second connecting parts are opposite and spaced apart;

The two inertial mass blocks are respectively hingedly connected to the ends of the two second connecting parts away from the base; the two inertial mass blocks also extend along the axial direction of the housing and are arranged at intervals;

At least one pair of bosses are respectively provided on the end surfaces of the two inertial mass blocks away from the base.

Preferably, the distance between the two first connecting parts far away from the base is smaller than the distance between the ends close to the base; and the distance between the two second connecting parts far away from the base is smaller than the distance between the ends close to the base.

Preferably, the two first connecting parts each include a first segment and a second segment; one end of the first segment is fixedly connected to the end face of the base away from the connection end, and the other end of the first segment is along the edge of the housing. The axial direction extends outward in the direction away from the base; one end of the second segment is fixedly connected to the end of the first segment away from the base, and the other end of the second segment moves toward the center of the shell along the radial direction of the shell. direction extension.

Preferably, the two second connecting parts each include a third segment and a fourth segment; one end of the third segment is hingedly connected to the end of the second segment away from the first segment, and the other end of the third segment is hingedly connected. One end extends along the radial direction of the shell toward the center of the shell; one end of the fourth segment is fixedly connected to the end of the third segment away from the second segment, and the other end of the fourth segment extends along the axial direction of the shell. The direction extends outward away from the base; the third segment is coaxially arranged with the second segment, and the fourth segment is arranged parallel with the first segment.

Preferably, the cross-sectional profile of the hinge connection portion of the two second connection portions respectively with the ends of the two first connection portions away from the base, or the cross-section of the hinge connection portion of the two inertial mass blocks with the ends of the two second connection portions away from the base. A contour is a closed shape with a symmetrical concave arc-shaped boundary or a closed shape with a concave hyperbolic boundary.

Based on the above technical solution, preferably, the optical fiber sensing and detection module includes an optical fiber body; an optical fiber grating is provided on the optical fiber body spanning at least one pair of boss end faces; and a third fiber grating on the surface of the optical fiber body that is in contact with the bosses. A metal coating also partially covers the optical fiber grating; two first through holes are provided on the side surface in the axial extension direction of the housing, and both first through holes are interconnected with the cavity; both ends of the optical fiber sensing detection module are respectively wound around and It passes through the first through hole with the largest distance from the boss and extends outward; the central angle of the portion of the optical fiber body wound between the boss and the first through hole with the largest distance is 180°.

Preferably, the surface of the optical fiber sensing detection module is further provided with a second metal plating layer; the first metal plating layer covers the surface of the second metal plating layer.

Further preferably, the first metal plating layer and the second metal plating layer are both metallic nickel plating layers; and the thickness of the first metal plating layer is greater than the thickness of the second metal plating layer.

On the other hand, the present invention provides a step metal-coated fiber grating high-temperature vibration composite sensing monitoring method, which includes the following steps:

S1: Configure the above-mentioned step metal-coated fiber grating high-temperature vibration composite sensor;

S2: Fix the shell; let external vibration and high temperature environment act on the step metal-coated fiber grating high-temperature vibration composite sensor and its optical fiber sensing detection module, causing tensile deformation and driving the center wavelength of the optical fiber sensing and detection module to drift. ;

S3: Analyze the drift of the center wavelength of the optical fiber sensing and detection module, and combine it with the elastomer mechanics model of the step metal-coated fiber grating high-temperature vibration composite sensor to obtain the relationship between the drift of the center wavelength of the optical fiber sensing and detection module and temperature and vibration. matrix.

Compared with the existing technology, the step metal-coated fiber grating high-temperature vibration composite sensor and monitoring method provided by the present invention have the following beneficial effects:

(1) This solution uses only one fiber grating fiber sensing detection module. By arranging half of the metallized fiber grating to be suspended and the other half of the metallized fiber grating to be fixed, synchronous measurement of temperature and vibration signals can be achieved. This method Compared with other fiber grating temperature-vibration composite sensors, the invention has a simpler structure and smaller size;

(2) Laser welding is used to fix the metallized optical fiber to realize glue-free packaging of the sensor, thereby improving the sensor's adaptability in high-temperature and harsh environments;

(3) The structure of a composite flexible hinge is used as the elastic element, which has smaller stiffness than a single flexible hinge, making the sensor more sensitive;

(4) The theoretical model of coating thickness established by the invention can quantitatively control the coating thickness to ensure that the fiber grating will not be damaged during the laser welding process.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a perspective view of the sensor of the step metal-coated fiber grating high-temperature vibration composite sensor and monitoring method of the present invention;

Figure 2 is a half-section perspective view of the sensor of the step metal-coated fiber grating high-temperature vibration composite sensor and monitoring method of the present invention;

Figure 3 is a half-section front view of the sensor of the step metal-coated fiber grating high-temperature vibration composite sensor and monitoring method of the present invention;

Figure 4 is a three-dimensional view of the combined state of the vibration sensing module and part of the optical fiber sensing detection module of the step metal-coated fiber grating high-temperature vibration composite sensor and monitoring method of the present invention;

Figure 5 is a top view of the combined state of the vibration sensing module and part of the optical fiber sensing detection module of the step metal-coated fiber grating high-temperature vibration composite sensor and monitoring method of the present invention;

Figure 6 is a half-section front view of the vibration sensing module and part of the optical fiber sensing detection module of the step metal-coated fiber grating high-temperature vibration composite sensor and monitoring method of the present invention;

Figure 7 is a diagram of the sensor dynamics model and force mechanics model of the step metal-coated fiber grating high-temperature vibration composite sensor and monitoring method of the present invention.

Reference signs: 5. Shell; 500. Cavity; 51. First through hole; 52. Connecting end; 53. Extended end; 1. Vibration sensing module; 105. Boss; 2. Optical fiber sensing detection module; 8. First metal plating; 101. Base; 102. First connection part; 103. Second connection part; 104. Inertial mass block; 1021. First segment; 1022. Second segment; 1031. Third segment Section; 1032, fourth segment; 300, first flexible hinge, 200, second flexible hinge; 21, optical fiber body; 22, fiber grating; 202, first grating area; 203, second grating area; 9. 2. Metal plating; 6. Fastening bolts; 54. Second through hole; 3. End cover; 4. Conical protective cover.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

As shown in Figures 1-3, on the one hand, the present invention provides a step metal-coated fiber grating high-temperature vibration composite sensor, which includes the following structure: a housing 5, a vibration sensing module 1 and an optical fiber sensing detection module 2. in:

A hollow cavity 500 is provided inside the housing 5; two first through holes 51 are provided on the side surface of the housing 5 in the axial extension direction, and both first through holes 51 are interconnected with the cavity 500; The two ends are the connecting end 52 and the extending end 53 respectively; the internal area of the cavity 500 is used to place the vibration sensing module 1 and the optical fiber sensing module 2 . In order to make it easier to pick up and place the vibration sensing module 1, the end of the extended end 53 of the housing 5 can be configured as a split structure, that is, the extended end 53 is provided with an internally threaded opening and is threadedly connected to the end cap 3 there. The two first through holes 51 are for facilitating the optical fiber sensing detection module 2 to pass through the housing 5 .

The vibration sensing module 1 is arranged in the cavity 500, with one end fixedly connected to the inner surface of the connecting end 52, and the other end extending toward the extended end 53 along the axial direction of the housing 5; the vibration sensing module 1 is provided with at least A pair of bosses 105, at least one pair of bosses 105 are opposite and spaced apart; the bosses 105 are used to make contact with the optical fiber sensing detection module 2. The vibration sensing module 1 as a whole is an elastomer structure and transmits the vibration or temperature received by the housing 5 to the optical fiber sensing detection module 2 .

The fiber optic sensing detection module 2 is tensioned and suspended on at least a pair of bosses 105 and their spacing areas of the vibration sensing module 1, and the two ends extending in the axial direction of the fiber optic sensing detection module 2 are respectively wound around and passed through the bosses 105. The first through hole 51 with the largest distance between the stages 105 extends outward; as can be seen from Figure 2, the optical fiber sensing detection module 2 does not pass through the area between the housing 5 and the vibration sensing module 1 in a straight line, but by winding. According to the layout, the free end of the optical fiber sensing detection module 2 does not extend from the nearest first through hole 51 after passing through the boss 105. Instead, after 180° internal rotation, it extends from the first through hole 51 on the other side of the housing 5. The through hole 51 protrudes, and 180° here refers to the central angle relative to the central axis of the housing 5 .

Among them, the surface of the optical fiber sensing detection module 2 in contact with at least one pair of bosses 105 and the surface inserted in the two first through holes 51 are both provided with a first metal plating layer 8, and the first metal plating layer 8 is also connected with at least a pair of bosses 105. The boss 105 or the inner surfaces of the two first through holes 51 are fixedly connected. In order to better fit and fix the first bonding metal coating 8 and the optical fiber sensing detection module 2, at least one pair of bosses 105 are also provided with corresponding semicircular grooves on their end surfaces, and the semicircular grooves are connected to the first pair of bosses 105. A metal coating 8 is adapted to the contours. In this solution, laser welding is used to fix the first metal plating layer 8 and the end surfaces of at least one pair of bosses 105 .

In order to ensure the contact area between the housing 5 and the optical fiber sensing detection module 2, an outwardly protruding stepped ring structure can be further provided on the side surface of the housing 5. The stepped inner surface of the stepped ring structure is in contact with the The first through holes 51 are connected with each other. The inner surface of the stepped annular structure and the inner surface of the first through hole 51 jointly hold up the optical fiber sensing detection module 2 and increase the contact area with the optical fiber sensing detection module 2 and the first metal plating layer 8 .

In order to seal and protect the shell, external threads are provided on the outer surface of the stepped annular structure. The outer shell 5 is provided with an internally penetrating conical protective cover 4. The conical protective cover 4 is connected to the stepped annular structure thread. Connect and allow the fiber optic sensing detection module 2 to extend. The vibration sensing module 1, shell 5, end cover 3 and conical protective cover 4 of this solution are all made of high temperature resistant stainless steel material 310S.

The surface of the optical fiber sensing detection module 2 in this solution is metalized by the first metal plating 8 and fixed by welding. Compared with adhesive packaging, it is better adapted to the harsh high-temperature environment outside the housing 5 .

As shown in Figures 2 and 3, in addition to at least a pair of bosses 105, the vibration sensing module 1 also includes a base 101, two first connection parts 102, two second connection parts 103 and two inertial mass blocks 104;

The base 101 is fixedly provided on the inner surface of the connecting end 52, and the other end extends along the axial direction of the housing 5;

The two first connecting parts 102 are spaced apart on the end surface of the base 101 away from the connecting end 52 . One end of the two first connecting parts 102 is fixedly connected to the base 101 , and the other ends of the two first connecting parts 102 are respectively along the shell 5 extending in the axial and radial directions;

The two second connection parts 103 are respectively hinge-connected to the ends of the two first connection parts 102 away from the base 101; the two second connection parts 103 also extend along the radial direction and axial direction of the housing 5; the two second connection parts 103 relative and spaced settings;

The two inertial mass blocks 104 are respectively hinge-connected to the ends of the two second connecting parts 103 away from the base 101; the two inertial mass blocks 104 also extend along the axial direction of the housing 5 and are spaced apart;

At least a pair of bosses 105 are respectively provided on the end surfaces of the two inertial mass blocks 104 away from the base 101 .

In order to better fix the base 101, a second observation through hole 54 is provided on the connecting end 52, and a threaded blind hole is provided on the base. The fastening bolt 6 passes through the second through hole 54 and is tightly connected to the base 101. The external vibration will pass through the base 101, the two first connecting parts 102, the two second connecting parts 103, the two inertial mass blocks 104 and at least a pair of bosses 105 in sequence, transmitting the deformation of the vibration sensing module 1 to the optical fiber sensing detection module 2.

As shown in the figure, the adjacent portions of the first connecting portion 102 and the second connecting portion 103 and the adjacent portions of the second connecting portion 103 and the inertial mass block 104 respectively form structures with reduced cross-sections, that is, the first connecting portion 102 A first hinge point is formed between the adjacent second connecting portion 103 and a second hinge point is formed between the second connecting portion 103 and the adjacent inertial mass block 104 . As a preferred embodiment, the cross-sectional profile of the first flexible hinge 300 and the second flexible hinge 200 is a closed shape with a symmetrical concave arc-shaped boundary or a closed shape with a concave hyperbola-shaped boundary. The first connecting part 102 and its first hinge point of this solution can be used as a single-notch straight circular flexible hinge, that is, the first flexible hinge 300; the entire second connecting part 103 and its second hinge point can be used as a double-notched straight circular flexible hinge. The flexible hinge is the second flexible hinge 200 . The first flexible hinge 300 and the second flexible hinge 200 together form a composite flexible hinge structure, forming an integral structure with the inertial mass block 104 and the base 101 . The boss 105 can be considered as a part of the inertial mass block 104, or can be provided separately. This solution prefers the former.

As shown in Figures 4-6, as a preferred embodiment, the distance between the two first connection parts 102 far away from the base 101 is smaller than the distance between the ends close to the base 101; the two second connection parts 103 are far away from the base 101 The distance between the ends is smaller than the distance between the ends close to the base 101 . Specifically, the two first connecting parts 102 and the two second connecting parts 103 can adopt the following structure; the two first connecting parts 102 each include a first segment 1021 and a second segment 1022; one end of the first segment 1021 and the base 101 is fixedly connected to the end face away from the connecting end 52, and the other end of the first segment 1021 extends outward along the axial direction of the housing 5 in a direction away from the base 101; one end of the second segment 1022 is connected to the first segment. The end of the segment 1021 away from the base 101 is fixedly connected, and the other end of the second segment 1022 extends along the radial direction of the housing 5 toward the center of the housing 5 . Both second connecting parts 103 include a third section 1031 and a fourth section 1032; one end of the third section 1031 is hingedly connected to the end of the second section 1022 away from the first section 1021, and the third section 1031 The other end extends along the radial direction of the housing 5 toward the center of the housing 5; one end of the fourth segment 1032 is fixedly connected to the end of the third segment 1031 away from the second segment 1022, and the fourth segment 1032 The other end extends outward along the axial direction of the housing 5 in a direction away from the base 101; the third section 1031 is coaxially arranged with the second section 1022, and the fourth section 1032 is arranged in parallel with the first section 1021. It can be seen that the first segment and the second segment are perpendicular to each other, and the third segment and the fourth segment are also perpendicular to each other. The two first connecting parts 102, the two second connecting parts 103, the two inertial mass blocks 104 and at least one pair of bosses 105 are respectively arranged symmetrically. Each of the first connecting part 102, the second connecting part 103, the inertial mass block 104 and the boss 105 arranged in sequence can swing independently. And the amplitude of the swing is constrained by the corresponding hinge points.

As shown in Figures 2 and 3, the optical fiber sensing and detection module 2 includes an optical fiber body 21; a fiber grating 22 is provided on the optical fiber body 21 spanning the end faces of at least one pair of bosses 105; the optical fiber body 21 is in contact with the bosses 105 The first metal coating 8 on the surface also partially covers the optical fiber grating 22; the central angle of the portion of the optical fiber body 21 wound between the boss 105 and the first through hole 52 with the largest distance is 180°. It can be seen that a part of the fiber grating 22 is suspended between the bosses 105, which is the first grating area 202; the other part of the fiber grating 22 is covered and fixed by the first metal plating layer 8 and the bosses 105, forming the second grating area 203. .

The surface of the optical fiber sensing detection module 2 is also entirely provided with a second metal plating layer 9 ; the first metal plating layer 8 covers the surface of the second metal plating layer 9 . The first metal plating layer 8 and the second metal plating layer 9 are both metallic nickel plating layers; and the thickness of the first metal plating layer 8 is greater than the thickness of the second metal plating layer 9, that is, the surface of the first gate area 202 is covered with the second metal plating layer 9. The surface of the second gate area 203 not only has the second metal plating layer 9 but also the first metal plating layer 8 and its position is fixed relative to the boss 105 . In particular, the length of the first grating area 202 and the length of the second grating area 203 are respectively half of the fiber grating 22 .

The second metal plating layer 9 and the first metal plating layer 8 of this solution are both nickel plating layers. The process of nickel plating is to conduct electroless nickel plating to prepare the second metal plating layer 9, and then perform electroless nickel plating to prepare the first metal plating layer 8. The thickness of the second metal plating layer 9 is about 5 microns, and the thickness of the first metal plating layer 8 is greater than 350 microns.

Electroless nickel plating uses an acidic electroless nickel plating process, which requires the use of chemicals including nickel sulfate, boric acid, propionic acid and sodium hypophosphite. The second metal plating layer 9 is prepared by first removing the protective layer and water film on the optical fiber body 21, and then immersing the optical fiber body 21 in the above-mentioned chemicals.

The chemicals required for nickel plating include nickel sulfate, nickel chloride, sodium dodecyl sulfate and boric acid, and the current density is controlled at 1-10A/dm ² . Due to the deposition of the first metal coating 8, this part of the fiber grating is subject to uniform stress, causing the normal reflection peak to be split into two at the fiber grating.

In addition, the present invention provides a step metal-coated fiber grating high-temperature vibration composite sensing monitoring method, which includes the following steps:

S1: Configure the above-mentioned step metal-coated fiber grating high-temperature vibration composite sensor;

S2: Fix the shell 5, and the external threads provided on the surface of the shell 5 are convenient for fastening; let external vibration and high temperature environment act on the step metal-coated fiber grating high-temperature vibration composite sensor and its optical fiber sensing detection module 2, resulting in Stretching and deforming, and driving the center wavelength of the optical fiber sensing detection module 2 to drift;

S3: Analyze the drift amount of the center wavelength of the optical fiber sensing detection module 2, and combine it with the elastomer mechanics model of the step metal-coated fiber grating high-temperature vibration composite sensor to obtain the drift amount of the center wavelength of the optical fiber sensing detection module 2 and its relationship with temperature and vibration. relationship matrix.

Combining Faraday's first law of electrolysis and establishing a theoretical model of nickel plating, the quality of nickel plating deposited during the electrolysis process can be expressed as:

, of which/> is the quality of deposited nickel plating;/> Represents electrochemical equivalent;/> Represents the current in the electrolytic cell solution;/> Indicates the time of nickel plating;

In addition, the quality of the electroplated nickel layer can also be expressed as:

, of which/> Indicates the density of electroplated nickel;/> Indicates the length of electroplated nickel;/> is the radial cross-sectional radius of the optical fiber body 21 after electroless nickel plating;/> is the radial cross-sectional radius of the optical fiber body 21 after nickel plating;

Combining the above expression for the quality of the nickel plating layer, the thickness of the nickel plating layer It can be expressed as:

.

Combined with the analysis of (a) in Figure 7, the dynamic model of the step metal-coated fiber grating high-temperature vibration composite sensor of this solution can be regarded as a mass-spring system, composed of the first flexible hinge 300 and the second flexible hinge 200. A composite flexible hinge can be considered as a series structure of a single-notch straight circular flexible hinge and a double-notch straight circular flexible hinge. The overall stiffness of the composite flexible hinge for:

, of which/> is the stiffness of the first flexible hinge 300;/> is the stiffness of the second flexible hinge 200. Then according to the rotation angle of the composite flexible hinge/> , establish a dynamic model of a step metal-coated fiber grating high-temperature vibration composite sensor:

, of which/> is the moment of inertia of the inertial mass block 104 and the boss 105;/> is the stiffness of the optical fiber body 21;/> is the axial length of the inertial mass block 104 and the boss 105 along the housing 5;/> is the radius of metallized fiber grating;/> is the mass of the inertial mass block 104 and the boss 105;/> is the inertial acceleration;/> is the horizontal distance from the center of mass to the rotation center of the composite flexible hinge;/> It is the vibration frequency caused by external effects.

Therefore, the natural frequency of the step metal-coated fiber grating high-temperature vibration composite sensor proposed by the present invention can be expressed as:

.

The entire fiber grating 22 is divided into two parts: the first grating area 202 of the suspended section and the second grating area 203 of the fixed section. The first grating area 202 is arranged between the two bosses 105. Under the action of acceleration, Tensile deformation will occur, but the second gate region 203 is not affected by acceleration. Referring to (b) in Figure 7, when being excited by external vibration, it will be accelerated in the vertical direction. The mass block 104 and the boss 105 will rotate around the composite flexible hinge relative to the base under the action of inertia force, resulting in a slight vibration. Swing, thereby driving the first gate area 202 to produce tensile deformation, and the axial deformation of the first gate area 202 It can be expressed as:

, of which/> is the length of the optical fiber body suspended between the bosses 105, that is, the spacing between the bosses 105.

When external temperature and vibration act on the sensor at the same time, the center wavelength drift of the first gate area 202 and the second gate area 203 can be expressed as:

, of which/> is the center wavelength drift amount of the first gate region 202;/> is the initial value of the center wavelength of the first gate region 202;/> is the effective elastic coefficient;/> is the thermal expansion coefficient of the optical fiber body;/> is the thermo-optical coefficient;/> is the temperature rise;/> is the center wavelength drift amount of the second gate region 203;/> is the initial value of the center wavelength of the second gate region 203;/> is the thermal expansion coefficient of nickel. The center wavelength shift of the first gate region 202 and the second gate region 203 is expressed in a matrix as:

, of which/> is the acceleration sensitivity coefficient; and/> is the temperature sensitivity coefficient;/> refers to the thermal expansion coefficient. This matrix is the matrix form of the relationship between the drift amount of the center wavelength of the optical fiber sensing detection module 2 and temperature and vibration mentioned in step S3. Through the expression of the matrix, it can be known that in the actual measurement process, by analyzing the first grating The degree of center wavelength drift of the area 202 and the second grating area 203 can simultaneously obtain the temperature information and vibration information of the environment where the step metal-coated fiber grating high-temperature vibration composite sensor is located.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (9)

1. The step metal coating fiber bragg grating high-temperature vibration composite sensor is characterized by comprising:

a housing (5) having a hollow cavity (500) therein;

the vibration sensing module (1) is fixedly arranged on the inner surface of the shell (5) at one end, and at least one pair of bosses (105) are arranged at the other end along the axial direction of the shell (5) in an extending manner, and the bosses (105) are opposite and are arranged at intervals;

the optical fiber sensing detection modules (2) are suspended in a tensioning manner in the at least one pair of bosses (105) and the interval areas thereof, and two end parts of the optical fiber sensing detection modules (2) also penetrate through the shell (5) and extend outwards;

the optical fiber sensing detection module (2) is provided with a first metal coating (8) on the surface contacted with at least one pair of bosses (105) and the surface penetrating through the shell (5), and the first metal coating (8) is fixedly connected with at least one pair of bosses (105); the optical fiber sensing detection module (2) comprises an optical fiber body (21); an optical fiber grating (22) is arranged on the optical fiber body (21) which is spanned on the end surfaces of at least one pair of bosses (105); the first metal coating (8) on the surface of the optical fiber body (21) contacted with the boss (105) also covers the optical fiber grating (22) partially; two first through holes (51) are formed in the side surface of the shell (5) in the axial extending direction, and the two first through holes (51) are communicated with the cavity (500); the two ends of the optical fiber sensing detection module (2) are respectively wound and pass through the first through hole (51) with the largest distance with the boss (105) and extend outwards; the central angle of the winding part of the optical fiber body (21) between the boss (105) and the first through hole (51) with the largest distance is 180 degrees.

2. The step metal coated fiber grating high temperature vibration composite sensor according to claim 1, characterized in that the vibration sensing module (1) further comprises a base (101), two first connecting parts (102), two second connecting parts (103) and two inertial mass blocks (104); the two ends of the shell (5) in the axial extending direction are respectively a connecting end (52) and an extending end (53);

the base (101) is fixedly arranged on the inner surface of the connecting end (52), and the other end of the base extends along the axial direction of the shell (5);

the two first connecting parts (102) are arranged on the end face of the base (101) far away from the connecting end (52) at intervals, one end of each first connecting part (102) is fixedly connected with the base (101), and the other ends of the two first connecting parts (102) extend along the axial direction and the radial direction of the shell (5) respectively;

the two second connecting parts (103) are respectively hinged with the end parts of the two first connecting parts (102) far away from the base (101); the two second connecting parts (103) are also arranged along the radial direction and the axial direction of the shell (5) in an extending way; the two second connecting parts (103) are opposite and are arranged at intervals;

the two inertial mass blocks (104) are respectively hinged with the end parts of the two second connecting parts (103) far away from the base (101); the two inertial mass blocks (104) also extend along the axial direction of the shell (5) and are arranged at intervals;

at least one pair of bosses (105) are respectively arranged on the end surfaces of the two inertial mass blocks (104) far away from the base (101).

3. The step metal coated fiber grating high temperature vibration composite sensor according to claim 2, characterized in that the spacing of the two first connection parts (102) at the end far from the base (101) is smaller than the spacing of the end near to the base (101); the distance between the two second connecting parts (103) and the end part far away from the base (101) is smaller than the distance between the two second connecting parts and the end part close to the base (101).

4. A step metal coated fiber grating high temperature vibration composite sensor according to claim 3, characterized in that said two first connections (102) each comprise a first section (1021) and a second section (1022); one end of the first section (1021) is fixedly connected with the end surface of the base (101) far away from the connecting end (52), and the other end of the first section (1021) extends outwards along the axial direction of the shell (5) towards the direction far away from the base (101); one end of the second section (1022) is fixedly connected with the end of the first section (1021) away from the base (101), and the other end of the second section (1022) extends towards the center of the housing (5) along the radial direction of the housing (5).

5. The step metal-plated fiber bragg grating high-temperature vibration compound sensor of claim 4, wherein the two second connection portions (103) each include a third segment (1031) and a fourth segment (1032); one end of the third section (1031) is hinged with the end part of the second section (1022) far away from the first section (1021), and the other end of the third section (1031) extends towards the center of the housing (5) along the radial direction of the housing (5); one end of the fourth segment (1032) is fixedly connected with the end of the third segment (1031) away from the second segment (1022), and the other end of the fourth segment (1032) extends outwards along the axial direction of the housing (5) towards the direction away from the base (101); the third section (1031) is coaxially arranged with the second section (1022), and the fourth section (1032) is parallel to the first section (1021).

6. The stepped metal-plated fiber bragg grating high-temperature vibration composite sensor of claim 2, wherein a cross-sectional profile of a hinge connection portion of the two second connection portions (103) and an end portion of the two first connection portions (102) away from the base (101), respectively, or a cross-sectional profile of a hinge connection portion of the two inertial mass blocks (104) and an end portion of the two second connection portions (103) away from the base (101), respectively, is a closed shape having a symmetrical concave arc boundary.

7. The step metal-plated fiber bragg grating high-temperature vibration composite sensor according to claim 1, wherein the surface of the fiber sensing detection module (2) is also integrally provided with a second metal plating layer (9); the first metal coating (8) covers the surface of the second metal coating (9).

8. The stepped metal-plated fiber bragg grating high-temperature vibration composite sensor of claim 7, wherein said first metal plating (8) and second metal plating (9) are both metal nickel plating; and the thickness of the first metal coating (8) is larger than that of the second metal coating (9).

9. The step metal coating fiber bragg grating high-temperature vibration composite sensing monitoring method is characterized by comprising the following steps of:

s1: configuring the step metal-plated fiber grating high-temperature vibration composite sensor according to any one of claims 1-8;

s2: fixing the shell (5); the external vibration and the high-temperature environment act on the step metal coating fiber grating high-temperature vibration composite sensor and the fiber sensing detection module (2) thereof to generate stretching deformation and drive the center wavelength of the fiber sensing detection module (2) to drift;

s3: analyzing the drift amount of the center wavelength of the optical fiber sensing detection module (2), and combining an elastic physical model of the step metal coating optical fiber grating high-temperature vibration composite sensor to obtain a relation matrix of the drift amount of the center wavelength of the optical fiber sensing detection module (2) and the temperature and vibration: the dynamic model of the step metal coating fiber bragg grating high-temperature vibration composite sensor is regarded as a mass-spring system, and a first hinge point is formed between a first connecting part (102) and an adjacent second connecting part (103); a second hinge point is formed between the second connecting part (103) and the adjacent inertial mass block (104); the first connecting part (102) and the first hinge point thereof are used as a single-notch straight round flexible hinge, namely a first flexible hinge (300); the whole second connecting part (103) and the second hinge point thereof are used as a double-notch straight round flexible hinge, namely a second flexible hinge (200); a composite flexible hinge formed by a first flexible hinge (300) and a second flexible hinge (200) together is considered to be a serial structure of a single-notch straight round flexible hinge and a double-notch straight round flexible hinge, and the overall rigidity K of the composite flexible hinge _z The method comprises the following steps:

wherein K is ₁ Is the stiffness of the first flexible hinge (300); k (K) ₂ Is the stiffness of the second flexible hinge (200); and then, according to the rotation angle delta theta of the composite flexible hinge, establishing a dynamic model of the step metal-coated fiber bragg grating high-temperature vibration composite sensor:

wherein J is the moment of inertia of the inertial mass (104) and the boss (105); k (K) _f Is the rigidity of the optical fiber body (21); h is the axial length of the inertial mass (104) and the boss (105) along the housing (5); r is the radius of the metallized fiber grating; m is the mass of the inertial mass block (104) and the boss (105); a is inertial acceleration; d, d _x Is the horizontal distance from the mass center to the rotation center of the composite flexible hinge; omega is the vibration frequency caused by external action;

the natural frequency of the step metal coating fiber bragg grating high-temperature vibration composite sensor is expressed as:

the whole fiber bragg grating (22) is split into a first grating region (202) of a suspension section part and a second grating region (203) of a fixed section part, the first grating region (202) is arranged between two bosses (105) and can generate stretching deformation under the action of acceleration, and the second grating region (203) is not influenced by the acceleration; when being excited by external vibration, the mass block (104) and the boss (105) are accelerated in the vertical direction and rotate relative to the base around the composite flexible hinge under the action of inertia force to generate micro-swing, thereby driving the first grid region (202) to generate tensile deformation and the axial deformation delta epsilon of the first grid region (202) ₁ Expressed as:

wherein l isThe length of the fiber body suspended between the bosses (105), i.e., the spacing of the bosses (105);

when external temperature and vibration are simultaneously applied to the sensor, the center wavelength drift of the first gate region (202) and the second gate region (203) can be expressed as:

wherein Deltalambda _B1 Is the amount of center wavelength shift of the first gate region (202); lambda (lambda) _B1 Is the initial value of the center wavelength of the first gate region (202); ρ _e Is an effective elasto-optical coefficient; alpha _f1 Is the thermal expansion coefficient of the optical fiber body; zeta type _f Is a thermo-optic coefficient; delta T is temperature rise; Δλ (delta lambda) _B2 Is the amount of center wavelength shift of the second gate region (203); lambda (lambda) _B2 Is the initial value of the center wavelength of the second gate region (203); alpha _f2 Is the thermal expansion coefficient of nickel; the center wavelength shift of the first gate region (202) and the second gate region (203) is represented by a matrix:wherein K is _a1 Is an acceleration sensitivity coefficient; k (K) _f1 And K _f2 Is a temperature sensitivity coefficient; alpha refers to the coefficient of thermal expansion.