CN102095537A - Fiber grating pressure sensor, manufacture method and method for monitoring load of asphalt pavement - Google Patents

Abstract

The invention relates to an optical fiber grating pressure sensor, a manufacturing method and an asphalt pavement load monitoring method, belonging to the field of civil engineering sensor testing. The structure consists of a metal casing (1), a fiber Bragg grating (2) installed in the metal casing (1), and a polymer part (3) for encapsulating the fiber Bragg grating (2) in the metal casing (1); The above-mentioned polymer part (3) is composed of a left cube fixed on the lower side of the upper metal cover (4), a right cube and an elongated horizontal cube fixed between the left cube and the right cube, and the whole is dumbbell-shaped; the fiber Bragg grating (2) Encapsulated in the polymer part (3) slender horizontal cube along the horizontal direction, and the transmission optical fibers at both ends extend out of the left and right cubes. The invention utilizes the dumbbell-shaped structure to realize the sensitivity enhancement of the optical fiber grating pressure sensor and improve the sensitivity of the sensor.

Description

Optical fiber grating pressure sensor and manufacturing method, and asphalt pavement load monitoring method

technical field

The invention relates to an optical fiber grating pressure sensor, a manufacturing method and an asphalt pavement load monitoring method, belonging to the field of civil engineering sensor testing. the

Background technique

Highways are closely related to human life, play a decisive role in the economic development of a country and a region, and serve as a link for communication between various regions. At the same time, they also undertake the tasks of passenger and freight transportation, which has the advantages of speed and convenience. In order to adapt the highway to the development pattern of the national economy and coordinate with other modes of transportation, an efficient, fast and safe key highway system and national highway trunk line system should be established so that the traffic capacity of the highway can meet the needs of social development and the national economy as a whole. To meet the needs of the country, my country has specially formulated a national key highway plan and a development plan for national trunk lines, that is, 85,000 kilometers of national expressways and a number of local expressways will be built before 2010, and a national expressway network will be formed before 2020. the

Highway pavement not only has to resist various harsh natural conditions, but also directly bears the load of passing vehicles. In recent years, asphalt pavement has been used more and more widely, and most of the surface course of high-grade highway pavement is asphalt pavement. Asphalt pavement is a pavement structure that uses asphalt as a binder, combined with mineral aggregates or other mixtures to build a pavement surface layer. Because asphalt pavement uses asphalt with strong cohesive force as a binder, it strengthens the gap between mineral aggregate particles. Therefore, the asphalt pavement has many advantages: wear-resistant, smooth, impermeable, dust-free, durable, etc., and the asphalt has good viscosity, elasticity, and plasticity, and the noise is low when driving. , small vibration, stable and comfortable, slightly elastic. the

The quality of the road surface affects the operating cost of the vehicle, the smoothness of the road and the comfort of driving, and directly affects the economic benefits of the society. Our country invests a lot of money in the construction and maintenance of highways every year, but due to the combined effects of severe overloading, overspeeding and natural factors of some vehicles, many highways are damaged, and the effective use time of most highways has not reached the designed service life. Serious early damage occurred 2-3 years after it was opened to traffic. These damages mainly include: ruts, potholes, cracks, cracks, loose, exposed, uplift, water damage, etc. The existence of road damage directly affects the driving safety and Traffic efficiency. the

Most of these failure phenomena are closely related to the load on the pavement. Therefore, it is necessary to study a set of asphalt pavement load monitoring system to realize the monitoring of vehicle load and speed, and to explore the mechanism and development law of pavement damage. the

At present, the sensors for road load monitoring mainly include strain gauge load cells, hydraulic piston load cells, spring load cells and piezoelectric load cells. They generally have high sensitivity and precision, but there are problems of durability, long-term stability and electromagnetic interference, which cannot meet the needs of pavement structural health monitoring. In recent years, the application of fiber grating sensing in the field of civil engineering has attracted more and more attention. It has the advantages of high sensitivity, anti-electromagnetic interference, simple structure, small size, and good stability. But because the optical fiber is relatively slender, it is easy to break due to shearing force. If it is directly applied to civil engineering, the survival rate is low. Therefore, although fiber grating sensors have been used in road monitoring, due to the complex construction environment of asphalt pavement structures, fiber gratings are rarely used in asphalt pavement structures, which is still in the trial stage; and the exposed fiber grating pressure sensitivity coefficient Smaller, only 1.98×10-12Pa-1, which brings inconvenience to signal detection and restricts the application of gratings in pressure measurement. Therefore, improving the pressure sensitivity and protecting the fiber grating are the key technologies to be solved to make the fiber grating enter the practical measurement. the

Contents of the invention

The object of the present invention is to propose a high-sensitivity, low-interference fiber grating pressure sensor, a manufacturing method and a load monitoring method for asphalt pavement, aiming at the problems of large interference in asphalt pavement monitoring and the accuracy of current monitoring methods. the

A fiber grating pressure sensor, characterized in that: it consists of a metal casing, a fiber Bragg grating installed in the metal casing, and a polymer part for encapsulating the fiber Bragg grating in the metal casing; the metal casing includes an upper metal cover; the above-mentioned The polymer part is composed of a left cube, a right cube fixed on the underside of the upper metal cover, and a slender horizontal cube fixed between the left cube and the right cube, and the whole is dumbbell-shaped; the above fiber Bragg grating is packaged in a slender In the horizontal cube, the two ends of the transmission fiber protrude from the left cube and the right cube. the

The manufacturing method of the above-mentioned fiber Bragg grating pressure sensor is characterized in that it includes the following process: (a), the polymer part is molded, and the fiber Bragg grating is encapsulated in the molding process; (b), the fiber Bragg grating is packaged The polymer part is fixed under the upper metal cover of the metal shell by glue; (c), the upper metal cover is assembled with other parts of the metal shell, and the two ends of the transmission optical fiber protrude from the metal shell. the

The asphalt pavement load monitoring method that utilizes above-mentioned fiber grating pressure sensor to carry out is characterized in that comprising following process: (a), this pressure sensor transmits the pressure acting on it to left cube and right cube through upper metal cover; Left cube and right cube Axial strain occurs in the right cube part, which in turn causes axial strain in the slender horizontal cube part; thus, axial strain occurs in the fiber Bragg grating embedded in it, which causes the wavelength shift of the fiber Bragg grating; (b), using fiber Bragg grating to The characteristic of axial strain sensitivity converts the load acting on the upper metal cover into the wavelength drift of the fiber Bragg grating, and monitors the load by monitoring the change of the center wavelength of the fiber Bragg grating; (c), using a slender horizontal cube with a cross-section smaller than The cross-sections of the left cube and the right cube realize the sensitization of the fiber grating pressure sensor and improve the sensitivity of the sensor. the

The sensor is packaged in the form of a combination of polymer and metal materials. The sensor shell is made of metal material to protect the sensor so as to improve its survival rate and service life. The sensing element of the sensor uses a polymer with a small elastic modulus to sensitize the fiber grating, which can not only achieve pressure sensitization, but also effectively protect the sensor. Bare fiber grating. High multiple pressure sensitization effect is achieved by changing the geometric structure of the polymer. The sensor can be directly embedded in the asphalt pavement, has high radial load measurement sensitivity, good real-time performance, and can realize distributed monitoring. The sensor can be directly buried inside the asphalt pavement, has good damage resistance, and can realize distributed online monitoring. the

Description of drawings

Figure 1 is the appearance of the fiber grating pressure sensor;

Fig. 2 is a sectional view of a fiber grating pressure sensor;

Fig. 3 is the polymer part of the fiber grating pressure sensor;

The names of the labels in the figure: 1. Metal shell, 2. Fiber Bragg grating, 3. Polymer part, 4. Upper metal cover, 5. Metal ring, 6. Metal bottom plate. the

Detailed ways

Figure 1 shows the appearance of the sensor. The metal housing 1 of the sensor consists of three parts: an upper metal cover 4 , a metal ring 5 , and a metal bottom plate 6 . Because the metal ring has a certain thickness, internal threads are processed on the metal ring, and the upper metal cover and the metal bottom plate are connected with the metal ring through threads to form the metal casing (1) of the sensor. The metal shell (1) encapsulates the polymer part 3 embedded in the Bragg fiber grating 2 in the shell, and makes both ends of the transmission optical fiber protrude from the metal shell 1. The metal shell 1 is mainly used to protect the sensor to improve its survival rate and service life. the

Figure 2 is a cross-sectional view of the sensor, it can be seen that the sensor consists of three components: a metal shell 1, a fiber Bragg grating 2, and a polymer part 3. Before the metal casing is assembled, the polymer part 3 embedded in the fiber Bragg grating 2 is fixed in the middle of the upper metal cover 4 by glue, and the metal casing 1 can protect the polymer part 3 from damage. the

Fiber Bragg grating 2, one of the components of the sensor, is the sensing element of the sensor, encapsulated in the polymer part 3, and is mainly used to sense the axial strain generated by the pressure transmitted through the upper metal cover 4. the

Figure 3 shows the polymer part of the sensor, which is fixed on the lower side of the upper metal cover 4 and is composed of cubes with different cross-sections. The polymer part 3 is composed of a left cube, a right cube, and a slender horizontal cube fixed between the left cube and the right cube, and is in the shape of a dumbbell as a whole; the fiber Bragg grating 2 is encapsulated in the polymer part 3 in the slender horizontal cube along the horizontal direction , the two ends of the transmission fiber protrude from the left cube and the right cube. The cross section of the elongated horizontal cube is smaller than that of the left cube and the right cube to realize the sensitivity enhancement of the fiber grating pressure sensor and improve the sensitivity of the sensor. . the

The polymer part 3 is formed by curing an epoxy resin and a curing agent in a certain proportion, and is mainly used for encapsulating the fiber grating to protect the fiber grating and increase sensitivity. It adopts mold molding, and the package mold is processed according to the package size, and the fiber grating is collimated and fixed in the center of the mold. Mix the epoxy resin and curing agent in a ratio of 1:1, add an appropriate amount of defoamer and stir evenly to eliminate the influence of air bubbles, inject the mold into the polymer to form it. Put the polymer-cast fiber grating and the mold into an incubator for high-temperature curing, open the mold, take out the fiber grating encapsulated with the polymer, and put it in the incubator again for low-temperature aging. the

After the fiber Bragg grating 2 is encapsulated by the polymer, the polymer part 3 embedded in the fiber Bragg grating 2 is fixed on the upper metal cover 4 by glue. Both the upper metal cover 4 and the metal bottom plate 6 are connected to the metal ring through threads to form a fiber grating pressure sensor. After the assembly is completed, both the polymer part 3 and the fiber Bragg grating 2 are inside the metal casing, which can protect the fiber Bragg grating 2 to a certain extent. the

The fiber grating pressure sensor transmits the pressure acting on it to the left cube and the right cube of the polymer part 3 through the upper metal cover 4; Strain; so that the fiber Bragg grating 2 embedded in the polymer part 3 is axially strained, causing the wavelength drift of the fiber Bragg grating 2;

The instrument needed for detection is a fiber grating demodulator. During the measurement, the fiber jumper is connected to the fiber grating demodulator, and the center wavelength of the fiber grating in the initial state is recorded. Apply a uniform load to the sensor step by step, and record the center wavelength of the fiber grating corresponding to the corresponding load. The sensitivity of the fiber grating pressure sensor can be obtained by analyzing the drift curve of the load and the center wavelength of the fiber grating. the

Claims (3)

1. A fiber grating pressure sensor, characterized in that: It consists of a metal housing (1), a fiber Bragg grating (2) installed in the metal housing (1), and a polymer part (3) for encapsulating the fiber Bragg grating (2) in the metal housing (1); The metal casing (1) above includes an upper metal cover (4); The above-mentioned polymer part (3) is composed of a left cube fixed on the lower side of the upper metal cover (4), a right cube and a slender horizontal cube fixed between the left cube and the right cube, and the whole is dumbbell-shaped; The above fiber Bragg grating (2) is packaged in a slender horizontal cube along the horizontal direction, and the two ends of the transmission fiber protrude from the left cube and the right cube. 2. the manufacture method of fiber grating pressure sensor according to claim 1, is characterized in that comprising the following process: (a), the polymer part (3) is molded, and the fiber Bragg grating (2) is encapsulated in the molding process; (b), fixing the polymer part (3) of the packaged fiber Bragg grating (2) under the upper metal cover (4) of the metal casing (1) by glue; (c) Assemble the upper metal cover (4) with other parts of the metal casing (1), and make the two ends of the transmission fiber protrude from the metal casing (1). 3.3. The asphalt pavement load monitoring method that utilizes the fiber grating pressure sensor described in claim 1 to carry out, it is characterized in that comprising the following process: (a), the pressure sensor transmits the pressure acting on it to the left cube and the right cube through the upper metal cover (4); the axial strain of the left cube and the right cube causes the axial strain of the slender horizontal cube ; so that the fiber grating embedded in it is axially strained, causing the wavelength drift of the fiber grating; (b) The load acting on the upper metal cover (4) is converted into the wavelength drift of the fiber grating by using the characteristic that the fiber grating is sensitive to axial strain, and the monitoring of the load is achieved by monitoring the change of the center wavelength of the fiber grating; (c) The cross-section of the elongated horizontal cube is smaller than the cross-section of the left and right cubes to realize the sensitization of the fiber grating pressure sensor and improve the sensitivity of the sensor.

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